Simulation-based load and damage estimation method and system for civil aircraft heavy landing conditions

Abstract

This application belongs to the field of aircraft safety assessment technology, specifically involving a simulation-based method and system for estimating loads and damage under heavy landing conditions for civil aircraft. It aims to solve the problem of achieving a balance between computational efficiency and analytical accuracy, as well as precise estimation of loads under multiple conditions and quantitative damage assessment during heavy landing. The method includes: constructing a full-size structural model, a landing gear model, and fine-grid sub-models for key locations; setting heavy landing condition parameters and conducting heavy landing simulations; acquiring the acceleration and displacement at measurement points, and material damage at key locations; obtaining the impact load transmission path diagram based on acceleration and displacement; and obtaining equivalent stress cloud maps and damage factor cloud maps for key locations based on material damage. The simulation-based method and system for estimating loads and damage under heavy landing conditions for civil aircraft provided in this application significantly reduces computational resources and time, and achieves precise analysis of the impact load transmission law and quantitative assessment of structural damage at key locations.

Description

Technical Field

[0001] This invention belongs to the field of aircraft safety assessment technology, specifically relating to a simulation-based method and system for estimating loads and damage during heavy landing of civil aircraft, as well as an electronic device, a computer-readable storage medium, and a computer program product containing instructions. Background Technology

[0002] A hard landing refers to a special landing event in which an aircraft lands exceeding its maximum operating load, resulting in damage to the airframe structure or landing gear, or requiring a comprehensive inspection as mandated. In recent years, influenced by factors such as frequent extreme weather events and denser flight networks, the frequency of hard landing accidents has further increased, and related safety hazards have become increasingly prominent. This underscores the importance and urgency of structural safety assessment under hard landing conditions, necessitating the use of precise simulation analysis technology to support structural design and safety assurance.

[0003] In the field of simulation analysis for heavy landing of civil aircraft, the core technical challenge has always centered on balancing computational efficiency at the whole-aircraft scale with analytical accuracy in key local areas. Existing modeling methods generally have significant shortcomings and are difficult to meet actual engineering needs. Specifically, the deficiencies of existing technologies are mainly reflected in the following three aspects:

[0004] Firstly, it is difficult to balance accuracy and efficiency in whole-aircraft modeling. If a uniform fine-mesh modeling strategy is adopted for the whole aircraft, although the geometric details of key local structures such as the landing gear-fuselage connection area and wing root can be fully preserved, which is beneficial to improving the analysis accuracy of key information such as stress concentration and subtle deformation, it will lead to an exponential increase in the number of meshes, resulting in excessive consumption of computing resources. The single simulation solution cycle often takes several weeks or even months, which is seriously lagging behind the timeliness requirements of civil aircraft design iteration and airworthiness verification. On the other hand, if a coarse-mesh modeling is adopted for the whole aircraft to improve computing efficiency, although the solution time can be shortened, the fine mechanical response information of local key areas will inevitably be lost. It will be impossible to accurately capture the structural stress concentration effect and material failure process, resulting in the damage assessment results being conservative or having safety hazards, and making it difficult to truly reflect the actual load-bearing capacity of the structure.

[0005] Secondly, the load estimation methods have significant limitations. Existing heavy landing load estimation methods mostly focus on static load transfer analysis under a single operating condition, without fully considering the multi-parameter coupling effects during heavy landing—such as the synergistic influence of key parameters like aircraft landing weight, vertical sinking velocity, wing stiffness distribution, landing attitude (pitch and roll angles), and yaw speed. This leads to a large deviation between the predicted load transfer law and the actual accident scenario. At the same time, existing methods generally lack the ability to analyze the cumulative effect of structural damage under multiple weak heavy landing conditions (when the settling velocity and landing mass are low and all three attitude angles of the fuselage are zero). In actual operation, aircraft may experience multiple light or moderate heavy landings that do not meet the "severe heavy landing" standard, and the cumulative damage may also lead to a decrease in structural safety margin. Existing technologies cannot provide effective load assessment basis for such scenarios.

[0006] Third, the damage assessment model lacks quantitative accuracy. Traditional heavy landing damage assessment relies heavily on empirical formulas based on fitting experimental data, which makes it difficult to accurately characterize the structural damage evolution mechanism under high strain rate and large deformation conditions during heavy landing. As a result, the damage assessment results cannot quantitatively reflect the complete process of the material from elastic deformation and plastic yielding to crack initiation, making it difficult to provide scientific and reliable technical support for the assessment of the remaining strength of the main load-bearing structure and maintenance decisions.

[0007] In summary, the current civil aircraft hard landing simulation analysis technology suffers from several shortcomings. These include an imbalance between the efficiency of whole-aircraft modeling and the accuracy of local analysis, the one-sidedness of multi-condition load estimation, and the reliance on empirical damage assessment. These factors collectively limit the accuracy and engineering applicability of hard landing safety assessments. Therefore, there is an urgent need for a hard landing load and damage estimation method that balances computational efficiency and analytical accuracy, enabling precise estimation of multi-condition loads and quantitative damage assessment. This method would address the deficiencies of existing technologies and provide reliable technical support for civil aircraft hard landing safety design, airworthiness certification, and maintenance decisions. Summary of the Invention

[0008] To address the aforementioned technical problems in the prior art, namely how to achieve both computational efficiency and analytical accuracy, accurate estimation of multi-condition loads and quantitative damage assessment in heavy landing load and damage estimation, this application provides a simulation-based method and system for estimating civil aircraft heavy landing load and damage.

[0009] In a first aspect of this application, a simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft is provided, comprising:

[0010] Construct a full-scale structural model of the civil aircraft;

[0011] Construct a landing gear model of the aforementioned civil aircraft;

[0012] Based on the full-size structural model and the landing gear model, a fine mesh sub-model is constructed for the key locations, which are the stress-concentrated landing gear-fuselage connection areas.

[0013] Set the parameters for the hard landing condition, which include initial conditions, ground model and tire contact definition. The initial conditions include wing stiffness, aircraft weight, descent speed, yaw speed, pitch angle and roll angle.

[0014] Based on the full-size structural model and the hard landing parameters, a hard landing simulation of the civil aircraft was performed.

[0015] Verify the fine mesh sub-model;

[0016] If the verification is successful, the acceleration and displacement of the preset measurement points are obtained based on the fine mesh sub-model, as well as the material damage of the landing gear-fuselage connection area;

[0017] The impact load transmission path diagram is obtained based on the acceleration and displacement of the preset measuring points; and...

[0018] Based on the material damage, the equivalent stress cloud map and damage factor cloud map of the landing gear-airframe connection area are obtained.

[0019] Optionally, the construction of the full-size structural model of the civil aircraft includes:

[0020] The mass of the nose and tail sections is applied to the floor longitudinal beams of the mid-section of the passenger cabin via 12 concentrated mass points. The mid-section of the fuselage includes the central wing box, the mid-wing section, and the landing gear of the civil aircraft. The mid-wing section includes the mid-section of the passenger cabin and the nacelle. The nose section is the fuselage preceding the mid-section of the fuselage, including the nose. The tail section is the fuselage following the mid-section of the fuselage, including the tail.

[0021] Adjust the mass of the 12 concentrated mass points so that the center of gravity of the mid-section fuselage after removing the landing gear is on the same cross-section as the line of action of the resultant force of the landing gear, and the cross-section is perpendicular to the fuselage roller axis.

[0022] The material constitutive model is set as a bilinear elastoplastic model, and the skeleton of the middle section of the cabin is modeled using reduced integral shell elements to obtain the skeleton model of the middle section of the cabin.

[0023] The material constitutive model is set as an elastic model. Beam elements are used to model the skeleton of the central wing box and the skeleton of the nacelle, resulting in the central wing box skeleton model and the nacelle skeleton model.

[0024] The reduced integral shell unit is used to model the skin corresponding to the skeleton of the cabin midsection, the central wing box and the nacelle, and the skeleton models of the cabin midsection, the central wing box and the nacelle are connected to the corresponding skin parts.

[0025] Rigid connector units are used to connect and assemble the cabin midsection skeleton model, the central wing box skeleton model, and the nacelle skeleton model after the skin is connected, to obtain the full-size structural model.

[0026] Optionally, constructing the landing gear model of the civil aircraft includes:

[0027] The upper sleeve and lower sleeve of the buffer rod can be considered as a spring unit and a damping unit, respectively, with the spring unit having a spring stiffness of 3 × 10⁻⁶. 5 N / m, the damping coefficient of the damping unit is 3.42×10 5 Ns / m, and the sliding joint of the upper sleeve of the buffer rod and the lower sleeve of the buffer rod is set as a translational joint;

[0028] The tire uses a hyperelastic constitutive material and adopts the Mooney-Rivlin model or the Yeoh model. The tire is coupled to the lower sleeve of the buffer rod through rigid elements. A uniformly distributed load equivalent to air pressure is applied to the inner wall of the tire, and the kinematic pair of the tire is set as a revolute pair.

[0029] The bolted connections of the landing gear-fuselage connection area are simulated using beam elements. The hinges of the landing gear-fuselage connection area are defined using the JOINT keyword of LS-DYNA. The landing gear-fuselage connection area is made of stainless steel, and the stainless steel material is a JC constitutive model that includes strain rate effects.

[0030] The landing gear includes an upper sleeve of the buffer bar, a lower sleeve of the buffer bar, a tire and a landing gear-body connection area. The upper sleeve of the buffer bar is connected to the body by bolts, and the lower sleeve of the buffer bar is connected to the tire through the rigid unit. The landing gear-body connection area is composed of a reinforcing plate and a strut structure.

[0031] Optionally, in constructing the landing gear model of the civil aircraft, when the tire is set as an incompressible rubber material with a medium strain range, the Mooney-Rivlin model is used; when the tire is set as a filler rubber with large deformation and changes with deformation according to the shear model, the Yeoh model is used; the upper sleeve and lower sleeve of the buffer rod are subjected to displacement constraints using the LS-DYNA JOINT keyword; and when a uniformly distributed load is applied to the inner wall of the tire, the stress relaxation setting is performed using the LS-DYNA CONTROL_DYNAMIC_RELAXION keyword.

[0032] Optionally, the step of constructing a fine-mesh sub-model for key locations based on the full-size structural model and the landing gear model includes:

[0033] The full-size structural model and the landing gear model are assembled to obtain a coarse network parent model that includes all the structures of the civil aircraft.

[0034] Extract the mesh surface at the boundary of the key position in the coarse network parent model as the boundary layer, and set the displacement data of all mesh nodes on the boundary layer as the d3interface file to be output;

[0035] Based on the coarse network parent model and the pre-set heavy landing condition parameters, a heavy landing simulation was performed on the civil aircraft to obtain the d3interface file;

[0036] The coarse mesh model, which includes the key positions within the boundary layer envelope of the coarse mesh parent model, is copied into the blank model to obtain the copied mesh model.

[0037] The copied mesh model is redrawn using a hexahedral volume mesh to obtain a redrawn mesh model.

[0038] Using the d3interface file as boundary conditions, a re-landing simulation was performed based on the same re-landing condition parameters and the coarse mesh parent model to obtain the global dynamic response of the entire aircraft and the displacement-time history of the boundary nodes at the key locations.

[0039] The displacement-time history is transferred to the redrawn mesh model to obtain the fine mesh sub-model.

[0040] Optionally, the ground model is a single-layer rigid ground, and the tire contact is defined as the contact algorithm between the tire and the rigid ground, which is an automatic contact algorithm.

[0041] Optionally, verifying the fine mesh sub-model includes:

[0042] Extract the peak ground contact force of the landing gear in the fine mesh sub-model, and calculate the contact force error between the peak ground contact force and the reference peak.

[0043] Extract the first stress peak value and the first displacement peak value of the fine mesh sub-model in the boundary region, and extract the second stress peak value and the second displacement peak value of the coarse mesh parent model in the boundary region;

[0044] Calculate the stress peak error between the first stress peak and the second stress peak, and the displacement peak error between the first displacement peak and the second displacement peak;

[0045] If the contact force error is less than or equal to the first preset threshold, the peak stress error is less than or equal to the second preset threshold, and the peak displacement error is less than or equal to the third preset threshold, then the verification is successful. The boundary region is the area formed by moving one or two units from the boundary of the connection area between the fine mesh sub-model and the coarse mesh parent model toward the fine mesh sub-model.

[0046] Optionally, obtaining the impact load transmission path diagram based on the acceleration and displacement of the preset measuring points includes:

[0047] The load at the preset measuring point is obtained based on the acceleration and displacement of the preset measuring point, and the load at different preset measuring points is normalized.

[0048] The normalized load is filtered to obtain the denoised load;

[0049] Based on the denoised load peak values ​​at each of the preset measurement points, the impact load transmission path diagram is obtained.

[0050] Optionally, obtaining the equivalent stress cloud map and damage factor cloud map of the landing gear-fuselage connection area based on the material damage includes:

[0051] Based on the JC constitutive model and corresponding damage model of the landing gear-fuselage connection area, as well as the material damage, the equivalent stress cloud map and damage factor cloud map of the landing gear-fuselage connection area are obtained.

[0052] Optionally, the simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft further includes:

[0053] Modify the parameters for the hard landing condition;

[0054] Based on the full-size structural model and the modified hard landing parameters, a hard landing simulation was performed on the civil aircraft.

[0055] Based on the fine mesh sub-model, the acceleration and displacement of preset measurement points are obtained, as well as the material damage of the landing gear-fuselage connection area is obtained;

[0056] An impact load transmission path diagram is obtained based on the acceleration and displacement of the preset measuring points, and an equivalent stress cloud diagram and damage factor cloud diagram of the landing gear-fuselage connection area are obtained based on the material damage.

[0057] Based on multiple impact load transmission path diagrams obtained after modifying the parameters of the hard landing condition multiple times, the impact load transmission paths under different hard landing conditions are analyzed; and...

[0058] Based on multiple equivalent stress cloud maps and multiple damage factor cloud maps obtained after modifying the parameters of the hard landing condition multiple times, the damage situation of the fuselage-landing gear connection area under different hard landing conditions is analyzed.

[0059] Optionally, the simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft further includes:

[0060] Create a second rigid ground identical to the first rigid ground under the current first rigid ground, and delete the first rigid ground;

[0061] Set the sinking velocity in the heavy landing condition parameters to the initial sinking velocity;

[0062] The stress of the full-size structural model is initialized, and a hard landing simulation of the civil aircraft is performed based on the modified sinking speed and the stress-initialized full-size structural model to obtain the material damage of the landing gear-fuselage connection area.

[0063] The change in the damage factor of the landing gear-fuselage connection area is obtained based on the material damage.

[0064] In a second aspect of this application, a simulation-based system for estimating loads and damage during a heavy landing of a civil aircraft is provided, the system comprising:

[0065] Full-size structural model building module, used to build full-size structural models of civil aircraft;

[0066] The landing gear model building module is used to build the landing gear model of the civil aircraft.

[0067] The fine mesh sub-model construction module is used to construct fine mesh sub-models for key locations based on the full-size structural model and the landing gear model. The key locations are the landing gear-fuselage connection areas where stress is concentrated.

[0068] The heavy landing condition setting module is used to set the heavy landing condition parameters, which include initial conditions, ground model and tire contact definition. The initial conditions include wing stiffness, aircraft weight, descent speed, yaw speed, pitch angle and roll angle.

[0069] The simulation module is used to perform a hard landing simulation of the civil aircraft based on the full-size structural model and the hard landing condition parameters;

[0070] The verification module is used to verify the fine mesh sub-model;

[0071] The data acquisition module is used to acquire the acceleration and displacement of preset measurement points based on the fine mesh sub-model, and to acquire the material damage of the landing gear-fuselage connection area, if the verification is successful.

[0072] The load estimation module is used to obtain the impact load transmission path diagram based on the acceleration and displacement of the preset measuring points; and,

[0073] The damage estimation module is used to obtain the equivalent stress cloud map and damage factor cloud map of the landing gear-aircraft connection area based on the material damage.

[0074] Optionally, the full-size structural model building module is used for:

[0075] The mass of the nose and tail sections is applied to the floor longitudinal beams of the mid-section of the passenger cabin via 12 concentrated mass points. The mid-section of the fuselage includes the central wing box, the mid-wing section, and the landing gear of the civil aircraft. The mid-wing section includes the mid-section of the passenger cabin and the nacelle. The nose section is the fuselage preceding the mid-section of the fuselage, including the nose. The tail section is the fuselage following the mid-section of the fuselage, including the tail.

[0076] Adjust the mass of the 12 concentrated mass points so that the center of gravity of the mid-section fuselage after removing the landing gear is on the same cross-section as the line of action of the resultant force of the landing gear, and the cross-section is perpendicular to the fuselage roller axis.

[0077] The material constitutive model is set as a bilinear elastoplastic model. The skeleton of the middle section of the cabin is modeled using Belytschko-Tsey reduced integral shell elements to obtain the skeleton model of the middle section of the cabin.

[0078] The material constitutive model is set as an elastic model. Beam elements are used to model the skeleton of the central wing box and the skeleton of the nacelle, resulting in the central wing box skeleton model and the nacelle skeleton model.

[0079] The reduced integral shell unit is used to model the skin corresponding to the skeleton of the cabin midsection, the central wing box and the nacelle, and the skeleton models of the cabin midsection, the central wing box and the nacelle are connected to the corresponding skin parts.

[0080] Rigid connector units are used to connect and assemble the cabin midsection skeleton model, the central wing box skeleton model, and the nacelle skeleton model after the skin is connected, to obtain the full-size structural model.

[0081] Optionally, the landing gear model construction module is used for:

[0082] The upper sleeve and lower sleeve of the buffer rod can be considered as a spring unit and a damping unit, respectively, with the spring unit having a spring stiffness of 3 × 10⁻⁶. 5 N / m, the damping coefficient of the damping unit is 3.42×10 5 Ns / m, and the sliding joint of the upper sleeve of the buffer rod and the lower sleeve of the buffer rod is set as a translational joint;

[0083] The tire uses a hyperelastic constitutive material and adopts the Mooney-Rivlin model or the Yeoh model. The tire is coupled to the lower sleeve of the buffer rod through rigid elements. A uniformly distributed load equivalent to air pressure is applied to the inner wall of the tire, and the kinematic pair of the tire is set as a revolute pair.

[0084] The bolted connections of the landing gear-fuselage connection area are simulated using beam elements. The hinges of the landing gear-fuselage connection area are defined using the JOINT keyword of LSDYNA. The landing gear-fuselage connection area is made of stainless steel, and the stainless steel material is a JC constitutive model that includes strain rate effects.

[0085] The landing gear includes an upper sleeve of the buffer bar, a lower sleeve of the buffer bar, a tire and a landing gear-body connection area. The upper sleeve of the buffer bar is connected to the body by bolts, and the lower sleeve of the buffer bar is connected to the tire through the rigid unit. The landing gear-body connection area is composed of a reinforcing plate and a strut structure.

[0086] Optionally, the landing gear model construction module is specifically used for: using the Mooney-Rivlin model when the tire is set as an incompressible rubber material with a medium strain range; using the Yeoh model when the tire is set as a filler rubber with large deformation and changes with deformation according to the shear model; using the LS-DYNA JOINT keyword to perform displacement constraints on the upper sleeve and the lower sleeve of the buffer rod; and using the LS-DYNA CONTROL_DYNAMIC_RELAXION keyword to perform stress relaxation settings when a uniformly distributed load is applied to the inner wall of the tire.

[0087] Optionally, the fine mesh sub-model building module is used for:

[0088] The full-size structural model and the landing gear model are assembled to obtain a coarse network parent model that includes all the structures of the civil aircraft.

[0089] Extract the mesh surface at the boundary of the key position in the coarse network parent model as the boundary layer, and set the displacement data of all mesh nodes on the boundary layer as the d3interface file to be output;

[0090] Based on the coarse network parent model and the pre-set heavy landing condition parameters, a heavy landing simulation was performed on the civil aircraft to obtain the d3interface file;

[0091] The coarse mesh model, which includes the key positions within the boundary layer envelope of the coarse mesh parent model, is copied into the blank model to obtain the copied mesh model.

[0092] The copied mesh model is redrawn using a hexahedral volume mesh to obtain a redrawn mesh model.

[0093] Using the d3interface file as boundary conditions, a re-landing simulation was performed based on the same re-landing condition parameters and the coarse mesh parent model to obtain the global dynamic response of the entire aircraft and the displacement-time history of the boundary nodes at the key locations.

[0094] The displacement-time history is transferred to the redrawn mesh model to obtain the fine mesh sub-model.

[0095] Optionally, the ground model is a single-layer rigid ground, and the tire contact is defined as the contact algorithm between the tire and the rigid ground, which is an automatic contact algorithm.

[0096] Optionally, the verification module is used for:

[0097] Extract the peak ground contact force of the landing gear in the fine mesh sub-model, and calculate the contact force error between the peak ground contact force and the reference peak.

[0098] Extract the first stress peak value and the first displacement peak value of the fine mesh sub-model in the boundary region, and extract the second stress peak value and the second displacement peak value of the coarse mesh parent model in the boundary region;

[0099] Calculate the stress peak error between the first stress peak and the second stress peak, and the displacement peak error between the first displacement peak and the second displacement peak;

[0100] If the contact force error is less than or equal to the first preset threshold, the peak stress error is less than or equal to the second preset threshold, and the peak displacement error is less than or equal to the third preset threshold, then the verification is successful. The boundary region is the area formed by moving one or two units from the boundary of the connection area between the fine mesh sub-model and the coarse mesh parent model toward the fine mesh sub-model.

[0101] Optionally, the load estimation module is used for:

[0102] The load at the preset measuring point is obtained based on the acceleration and displacement of the preset measuring point, and the load at different preset measuring points is normalized.

[0103] The normalized load is filtered to obtain the denoised load;

[0104] Based on the denoised load peak values ​​at each of the preset measurement points, the impact load transmission path diagram is obtained.

[0105] Optionally, the damage estimation module is used for:

[0106] Based on the JC constitutive model and corresponding damage model of the landing gear-fuselage connection area, as well as the material damage, the equivalent stress cloud map and damage factor cloud map of the landing gear-fuselage connection area are obtained.

[0107] Optionally, the simulation-based civil aircraft hard landing load and damage estimation system further includes a load and damage analysis module, which is used for:

[0108] Modify the parameters for the hard landing condition;

[0109] Based on the full-size structural model and the modified hard landing parameters, a hard landing simulation was performed on the civil aircraft.

[0110] Based on the fine mesh sub-model, the acceleration and displacement of preset measurement points are obtained, as well as the material damage of the landing gear-fuselage connection area is obtained;

[0111] An impact load transmission path diagram is obtained based on the acceleration and displacement of the preset measuring points, and an equivalent stress cloud diagram and damage factor cloud diagram of the landing gear-fuselage connection area are obtained based on the material damage.

[0112] Based on multiple impact load transmission path diagrams obtained after modifying the parameters of the hard landing condition multiple times, the impact load transmission paths under different hard landing conditions are analyzed; and...

[0113] Based on multiple equivalent stress cloud maps and multiple damage factor cloud maps obtained after modifying the parameters of the hard landing condition multiple times, the damage situation of the fuselage-landing gear connection area under different hard landing conditions is analyzed.

[0114] Optionally, the simulation-based civil aircraft hard landing load and damage estimation system further includes a damage accumulation analysis module, which is used for:

[0115] Create a second rigid ground identical to the first rigid ground under the current first rigid ground, and delete the first rigid ground;

[0116] Set the sinking velocity in the heavy landing condition parameters to the initial sinking velocity;

[0117] The stress of the full-size structural model is initialized, and a hard landing simulation of the civil aircraft is performed based on the modified sinking speed and the stress-initialized full-size structural model to obtain the material damage of the landing gear-fuselage connection area.

[0118] The change in the damage factor of the landing gear-fuselage connection area is obtained based on the material damage.

[0119] In a third aspect of this application, an electronic device is provided, comprising:

[0120] At least one processor; and

[0121] A memory communicatively connected to at least one of the processors; wherein,

[0122] The memory stores instructions that can be executed by the processor to implement the above-described simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft.

[0123] In a fourth aspect of this application, a computer-readable storage medium is provided, the computer-readable storage medium storing computer instructions, the computer instructions being executed by the computer to implement the above-described simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft.

[0124] In a fifth aspect of this application, a computer program product containing instructions is provided, which, when executed by a computer device, causes the computer device to perform the above-described simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft.

[0125] The simulation-based method and system for estimating loads and damage during heavy landings of civil aircraft provided in this application constructs a full-scale structural model of the civil aircraft based on the mid-section fuselage using a segmented equivalent approach. Then, based on the full-scale structural model and the landing gear model, a collaborative analysis system is established, consisting of a coarse-mesh parent model and fine-mesh sub-models at key locations under dual scales. Furthermore, by setting up simulation and analysis scenarios for heavy landings of civil aircraft with different operating conditions, the system can achieve precise analysis of the transmission patterns of impact loads and quantitative assessment of structural damage at key locations such as the landing gear-fuselage connection area, while significantly reducing computational resources and time. This provides efficient and accurate technical support for the crashworthiness design and safety risk prediction of civil aircraft structures. Attached Figure Description

[0126] Figure 1 This is a flowchart illustrating one implementation of the simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft, as described in this application.

[0127] Figure 2 This is an example diagram of the full-size structural model, landing gear model, and fine mesh sub-model of the civil aircraft in the simulation-based method for estimating loads and damages during heavy landing of civil aircraft in this application;

[0128] Figure 3 This is a simplified schematic diagram illustrating the construction process of the full-size structural model in this application;

[0129] Figure 4 A schematic diagram illustrating the application of concentrated mass points on the mid-section fuselage during the construction of a full-size structural model for this application;

[0130] Figure 5 A schematic diagram illustrating the mass matching of the mid-fuselage during the construction of a full-size structural model for this application;

[0131] Figure 6 A schematic diagram illustrating the skeleton modeling, skin connection, and assembly process during the construction of the full-size structural model for this application;

[0132] Figure 7 This is a structural schematic diagram of the landing gear model in this application;

[0133] Figure 8 This is an assembly diagram of the full-size structural model and landing gear model in this application;

[0134] Figure 9 A schematic diagram illustrating the relationship between the coarse-mesh parent model and the fine-mesh sub-model during the construction of the fine-mesh sub-model for this application;

[0135] Figure 10 This is a schematic diagram of the layout of the preset measuring points in this application;

[0136] Figure 11 This is a schematic diagram of the acceleration, displacement, and impact load transmission path of the preset measuring points in this application;

[0137] Figure 12 This is a schematic diagram of the equivalent stress cloud map and damage factor cloud map of the landing gear-fuselage connection area during the landing process in this application;

[0138] Figure 13 This is a flowchart illustrating another implementation of the simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft, as described in this application.

[0139] Figure 14 This is a schematic diagram of the rigid ground during the damage accumulation analysis process of this application;

[0140] Figure 15 This is a schematic diagram of the overall structural response, equivalent stress contour map, and damage factor contour map of the two hard landing processes during the damage accumulation analysis in this application.

[0141] Figure 16 This is a structural block diagram of one embodiment of the simulation-based civil aircraft hard landing load and damage estimation system of this application;

[0142] Figure 17 This is a structural block diagram of another implementation of the simulation-based civil aircraft hard landing load and damage estimation system of this application;

[0143] Attached figures: 1-Full-size structural model, 2-Fine mesh sub-model, 3-Landing gear model. Detailed Implementation

[0144] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description, in conjunction with the accompanying drawings and examples, further clarifies this application. It should be understood that the specific examples described herein are merely illustrative and not intended to limit the scope of this application. Furthermore, the technical features involved in the various embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0145] The present application will now be described in detail with reference to the accompanying drawings. A first aspect of this application provides a simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft. Figure 1 This paper presents a flowchart illustrating one embodiment of the simulation-based load and damage estimation method for heavy landing conditions of civil aircraft according to this application. Figure 1 As shown, the simulation-based load and damage estimation method for heavy landing conditions of civil aircraft according to the first embodiment of this application includes:

[0146] Step S101: Construct a full-size structural model of the civil aircraft;

[0147] Step S102: Construct the landing gear model of the civil aircraft;

[0148] Step S103: Based on the full-size structural model and the landing gear model, construct a fine mesh sub-model for key locations, where the key locations are the landing gear-fuselage connection areas where stress is concentrated.

[0149] Step S104: Set the heavy landing condition parameters. The heavy landing condition parameters include initial conditions, ground model and tire contact definition. The initial conditions include wing stiffness, aircraft weight, descent speed, heading speed, pitch angle and roll angle.

[0150] Step S105: Perform a hard landing simulation on the civil aircraft based on the full-size structural model and the hard landing condition parameters;

[0151] Step S106: Verify the fine mesh sub-model;

[0152] Step S107: If the verification is successful, obtain the acceleration and displacement of the preset measurement points based on the fine mesh sub-model, and obtain the material damage of the landing gear-fuselage connection area.

[0153] Step S108: Obtain the impact load transmission path diagram based on the acceleration and displacement of the preset measuring points;

[0154] Step S109: Based on the material damage, obtain the equivalent stress cloud map and damage factor cloud map of the landing gear-airframe connection area.

[0155] The civil aircraft (civil aircraft) mentioned above is preferably a typical civil aircraft (such as the MA60 civil aircraft). A typical civil aircraft refers to a civil passenger / transport aircraft that is technologically mature, widely used in the market, and representative in the civil aviation field. Its structural design, load characteristics, etc. cover the commonalities of most civil aircraft, and the research and design results can be transferred to the same type of aircraft. Furthermore, the parameters and data are abundant and readily available, which facilitates modeling and verification of simulation results. Moreover, the analysis methods and processes for typical civil aircraft can be directly applied to the actual design and airworthiness verification work of the aviation industry.

[0156] It should be noted that this application uses the simulation-based method for estimating the load and damage of civil aircraft during a hard landing as an example, employing LS-DYNA (Livermore Software Technology Corporation's Dynamic Analyzer) software for modeling and simulation. The functions and keywords mentioned below are also functions and keywords in LS-DYNA. LS-DYNA is a mature and widely used software in this field. The inputs, outputs, functions, and capabilities of its functions and commands, as well as the meanings and capabilities of its keywords, are well-known to those skilled in the art. Those skilled in the art can easily understand the functions used and how to apply them to other similar software based on their experience with LS-DYNA.

[0157] Figure 2 Example diagrams of the full-size structural model, landing gear model, and fine mesh sub-model of the civil aircraft in the simulation-based heavy landing load and damage estimation method for civil aircraft of this application are shown. The construction of the full-size structural model, landing gear model, and fine mesh sub-model will be described in detail below.

[0158] Specifically, in step S101, the entire civil aircraft is divided into three sections: front, middle, and rear. Only the middle fuselage section (including the central wing box, wing midsection, and landing gear; the wing midsection includes the passenger cabin midsection and nacelle) undergoes detailed structural modeling and refined mesh generation. The weight of the front / rear fuselage sections is applied as concentrated mass points to the load-bearing main beams of the middle fuselage section (the floor longitudinal beams of the passenger cabin midsection) and mass matching is performed. Through a segmentation + mass equivalence approach, using concentrated mass point equivalence and symmetric boundary condition equivalence methods, the complete aircraft model is simplified to a semi-model of the middle fuselage section, such as... Figure 3 A simplified schematic diagram of the full-size structural model construction process in this application is shown. The equivalent symmetry boundary conditions include: determining the symmetry form of the entire civil aircraft structure (e.g., planar symmetry, axisymmetry, central symmetry; for example, the mid-section fuselage is planar symmetric, and the fuselage annular section is axisymmetric); extracting a symmetric sub-model, i.e., extracting 1 / 2 (in the case of planar symmetry), 1 / 4 (in the case of dual-planar symmetry), or 1 / n of the complete structure as a symmetric sub-model; then applying rotational and translational freedom constraints to the symmetry plane boundaries of the sub-models, ensuring that nodes on the symmetry plane boundaries cannot exhibit in-plane rotation or out-of-plane translation. In finite element software, this can be directly set by selecting "symmetry boundary conditions," and the software will automatically generate equivalent constraints. This significantly reduces the computational resources and time required to construct the full-size structural model, thus significantly improving the efficiency of full-size structural model construction. The forward fuselage, also known as the nose section, is the fuselage preceding the mid-fuselage and including the nose; the aft fuselage, also known as the tail section, is the fuselage following the mid-fuselage and including the tail, including the vertical tail and horizontal tail. Specifically, step S101 may include:

[0159] Step S1011: The mass of the nose and tail sections is applied to the floor longitudinal beams of the mid-section of the passenger cabin through 12 concentrated mass points. Figure 4 This diagram illustrates the application of concentrated mass points to the mid-section fuselage during the construction of the full-size structural model in this application. Figure 4 As shown, the concentrated mass points can be evenly distributed along the longitudinal beams of the cabin floor. By distributing the mass of the 12 concentrated mass points, the center of gravity position of the mid-section fuselage (after removing the landing gear) (i.e., the center of gravity position of the model) can be controlled.

[0160] Step S1012: Adjust the mass of the 12 concentrated mass points so that the center of gravity of the mid-section fuselage after removing the landing gear is on the same cross-section as the line of action of the resultant force of the landing gear, and the cross-section is perpendicular to the fuselage roller axis. Figure 5 A schematic diagram of the mass matching of the mid-fuselage during the construction of the full-size structural model for this application is shown below. Figure 5 As shown in the axonometric view of the full-size structural model, the center of gravity of the mid-section fuselage after removing the landing gear (i.e., the model's center of gravity) and the line of action of the resultant force of the landing gear are on the same cross section. Correspondingly, the top view of the full-size structural model shows the line connecting the center of gravity of the mid-section fuselage after removing the landing gear and the point of action of the resultant force of the landing gear on the line of action of the resultant force of the landing gear.

[0161] Step S1013: Set the material constitutive model of the cabin midsection to a bilinear elastoplastic model (e.g., the LSDYNA24 bilinear elastoplastic model of LS-DYNA), and use reduced integral shell elements (e.g., the Belytschko-Tsey reduced integral shell element of LS-DYNA) to model the skeleton of the cabin midsection, and obtain the cabin midsection skeleton model.

[0162] Step S1014: Set the material constitutive model of the central wing box and the nacelle to an elastic model (e.g., the LSDYNA1 elastic model of LS-DYNA). Use beam elements (the properties can be defined by the Hyperbeam tool) to model the skeleton of the central wing box and the skeleton of the nacelle to obtain the skeleton model of the central wing box and the skeleton model of the nacelle.

[0163] Step S1015: Use a reduced integral shell element (e.g., the Belytschko-Tsey reduced integral shell element of LS-DYNA) to model the skin corresponding to the skeleton of the cabin midsection, the central wing box and the nacelle, and connect the skeleton model of the cabin midsection, the skeleton model of the central wing box and the skeleton model of the nacelle to the corresponding skin parts.

[0164] Step S1016: Use rigid connector units (such as LS-DYNA's Reb2 rigid connector unit) to connect and assemble the cabin midsection skeleton model, the central wing box skeleton model, and the nacelle skeleton model after connecting the skin to obtain the full-size structural model.

[0165] Figure 6 This diagram illustrates the skeleton modeling, skin connection, and assembly process during the construction of the full-size structural model in this application. Figure 6 As shown, the cabin midsection skeleton model, central wing box skeleton model, and nacelle skeleton model are connected to their respective skins, and then connected and assembled together through rigid connector units to obtain a complete full-size structural model.

[0166] The landing gear of a civil aircraft includes an upper sleeve of the buffer bar, a lower sleeve of the buffer bar, and a tire-landing gear-fuselage connection area. The upper sleeve of the buffer bar is connected to the fuselage by bolts, and the lower sleeve of the buffer bar is connected to the tire by a rigid unit. The landing gear-fuselage connection area (i.e., the landing gear and fuselage connection area) is composed of a reinforcing plate and a strut structure. Figure 7 This application shows a schematic diagram of the landing gear model. Figure 7 As shown, specifically, step S102 may include:

[0167] Step S1021: Based on the principle of rigid body dynamics, the upper sleeve and the lower sleeve of the buffer rod are equivalent to a spring unit and a damping unit, respectively. The spring stiffness of the spring unit can be set to 3×10⁻⁶. 5 N / m, the damping coefficient of the damping unit can be set to 3.42 × 10 N / m. 5 Ns / m, and the sliding joint of the upper sleeve and the lower sleeve of the buffer rod is set as a translational joint (buffer sleeve sliding joint setting).

[0168] Step S1023: Use a hyperelastic constitutive material for the tire, employing either the Mooney-Rivlin model or the Yeoh model. The tire is coupled to the lower sleeve of the buffer rod via rigid elements, and a uniformly distributed load equivalent to air pressure (tire internal pressure setting) is applied to the inner wall of the tire. The kinematic pairs of the tire are set as revolute pairs (tire revolute pair setting). Specifically, when the tire is set as an incompressible rubber material with a medium strain range, the Mooney-Rivlin model is used; when the tire is set as a filler rubber with large deformation and changes with deformation according to the shear model, the Yeoh model is used. The upper sleeve and lower sleeve of the buffer rod can be subjected to displacement constraints using the LS-DYNA JOINT keyword. Furthermore, when applying a uniformly distributed load to the inner wall of the tire, the LS-DYNA CONTROL_DYNAMIC_RELAXION keyword can be used for stress relaxation settings to avoid non-physical oscillations caused by abrupt preloads in subsequent processes. The tire model can be meshed using hexahedral solid elements.

[0169] Step S1023: The bolted connection of the landing gear-fuselage connection area is simulated using beam elements (e.g., ID beam elements of LS-DYNA). The hinge of the landing gear-fuselage connection area can be defined using the JOINT keyword of LS-DYNA. The landing gear-fuselage connection area is made of stainless steel and the stainless steel material is a JC constitutive model that includes strain rate effects.

[0170] By setting the material constitutive parameters of the upper and lower sleeves of the buffer bar, the tires, and the landing gear-fuselage connection area, as well as defining and simulating the structure, the landing gear model can be obtained.

[0171] Specifically, step S103 may include:

[0172] Step S1031: Assemble the full-size structural model and the landing gear model, as follows: Figure 8 The assembly diagram of the full-size structural model and landing gear model in this application shows that a coarse network parent model containing all the structures of the civil aircraft is obtained.

[0173] Step S1032: Extract (e.g., using the INTERFACE keyword in LS-DYNA) the mesh surface at the boundary of the key location (the landing gear-fuselage connection area where stress concentration occurs; this can be a region containing stress concentration areas and whose boundary has a set distance from the stress concentration areas (areas prone to stress concentration), preferably the lower half of the landing gear-fuselage connection area) in the coarse network parent model as the boundary layer (key location boundary layer), and set the displacement data of all mesh nodes on the boundary layer as the d3interface file to be output. The boundary can be obtained by dividing the boundary based on the end face of a solid element, the boundary of a shell element, or the node of a beam element, such as... Figure 9 The diagram illustrates the relationship between the coarse-network parent model and the fine-network sub-model during the construction of the fine-mesh sub-model in this application.

[0174] Step S1033: Based on the coarse network parent model and the pre-set heavy landing condition parameters, perform a heavy landing simulation on the civil aircraft to obtain the d3interface file;

[0175] Step S1034: Copy the coarse mesh model (including the key positions) within the boundary layer envelope of the coarse mesh parent model to the blank model to obtain the copied mesh model;

[0176] Step S1035: Use a hexahedral volume mesh to redraw the copied mesh model to obtain a redrawn mesh model;

[0177] Step S1036: Using the d3interface file as boundary conditions (e.g., setting boundary conditions using the INTERFACE keyword in LS-DYNA), a relanding simulation is performed based on the same relanding condition parameters as in step S1033 and the coarse mesh parent model. The global dynamic response of the entire aircraft and the displacement-time history of the boundary nodes at the key locations are obtained. The boundary node displacement values ​​output by the parent model (coarse mesh parent model) are as follows: Figure 9 As shown;

[0178] Step S1037: The displacement-time history is transferred (e.g., via the LINK keyword in LS-DYNA) to the redrawn mesh model to obtain the fine mesh sub-model.

[0179] Specifically, in step S104, the heavy landing condition parameters are set, including initial conditions, ground model and tire contact definition. The initial conditions include wing stiffness, aircraft weight, descent speed, heading speed, pitch angle and roll angle. For example, the wing stiffness is the nominal wing stiffness, 1 / 2 of the nominal wing stiffness, or 1 / 4 of the nominal wing stiffness; the aircraft weight is the empty landing weight, the design landing weight, or the maximum landing weight; the descent speed is 1.83 m / s, 3.05 m / s, 3.66 m / s, or 4.27 m / s; the directional speed is 0 m / s, 30 m / s, 60 m / s, or 90 m / s; the pitch angle is 0°, 2°, or 4°; and the roll angle is 0°, 2°, or 4°. Preferably, the aircraft weight can be set to an empty landing weight of 13700 kg, a descent speed of 1.83 m / s, a directional speed of 0 m / s, and the wing stiffness to the nominal wing stiffness, with the pitch and roll angles both set to 0°. Each simulation can change only one of the above initial condition parameters while keeping the others constant. The ground model is set to a rigid ground, and the tire contact is defined as the contact algorithm between the tire and the rigid ground, which is an automatic contact algorithm.

[0180] Specifically, in step S105, the INITIAL keyword of LS-DYNA can be used to assign initial conditions to the full-size structural model and apply a gravity field, and the rigid ground can be simplified to a rigid wall. Then, LS-DYNA is used to perform a hard landing simulation of the civil aircraft based on the full-size structural model and hard landing condition parameters, and the simulation results are output.

[0181] Specifically, in step S106, after the relanding simulation, the fine mesh sub-model is first verified. Specifically, step S106 may include:

[0182] Step S1061: Extract the peak ground contact force of the landing gear in the fine mesh sub-model based on the simulation results, and calculate the contact force error between the peak ground contact force and the reference peak (which can be obtained through actual experiment).

[0183] Step S1062: Extract the first stress peak and the first displacement peak of the fine mesh sub-model in the boundary region based on the simulation results, and extract the second stress peak and the second displacement peak of the coarse mesh parent model in the boundary region. The boundary region is the area formed by moving one or two units (mesh units) from the boundary of the connection area between the fine mesh sub-model and the coarse mesh parent model toward the fine mesh sub-model.

[0184] Step S1063, and calculate the stress peak error between the first stress peak and the second stress peak, and the displacement peak error between the first displacement peak and the second displacement peak;

[0185] Step S1063: If the contact force error is less than or equal to the first preset threshold, the stress peak error is less than or equal to the second preset threshold, and the displacement peak error is less than or equal to the third preset threshold, then the verification is successful; otherwise, the verification fails.

[0186] The first, second, and third preset thresholds can be the same, for example, all 5%, or they can be set to different values ​​according to verification needs. The displacement refers to the displacement components of the nodes within the boundary region of the model in the x, y, and z directions, and the peak displacement is the maximum value of the node's displacement in the x, y, and z directions. Each of the above errors can be the absolute value of the difference between the corresponding two.

[0187] The fine mesh sub-model is verified in step S106. If the verification passes, the subsequent load and damage estimation is performed. If the verification fails, it means that the accuracy of the fine mesh sub-model is insufficient. The process ends, and the full-size structural model, landing gear model, and fine mesh sub-model can be reconstructed until a fine mesh sub-model with the required accuracy (verification can be passed) is obtained. Load and damage estimation is then performed on this basis.

[0188] Specifically, in step S107, if the verification in step S106 is successful, the acceleration and displacement of preset measurement points are obtained based on the simulation results and the fine mesh sub-model, and the material damage of the landing gear-fuselage connection area is obtained based on the simulation results. The preset measurement points are landing load measurement points. Figure 10 A schematic diagram of the arrangement of the preset measuring points (hereinafter referred to as measuring points) in this application is shown, as follows: Figure 10 As shown, preferably, six measuring points are pre-arranged in both the cabin floor and the wing structure. The measuring points in the cabin floor are evenly distributed along the longitudinal direction of the floor beams, while the measuring points in the wing structure are arranged at the six wing reinforcing ribs. The load data output by the measuring points arranged in this way can reflect the load transmission law within the cabin and the wing. Specifically, the acceleration and displacement results of the preset measuring points can be defined using the DATEBASE keyword of LS-DYNA, as well as the material damage variable output of the landing gear-fuselage connection area. The acceleration and displacement of the preset measuring points, and the material damage of the landing gear-fuselage connection area, can be obtained from the simulation results using the LS-DYNA post-processing function.

[0189] Figure 11 A schematic diagram of the acceleration, displacement, and impact load transmission path at the preset measuring points in this application is shown. Specifically, as follows: Figure 11 As shown, after obtaining the acceleration and displacement of the preset measuring point in step S108, an impact load transmission path diagram is drawn based on the acceleration and displacement. Specifically, step S108 includes:

[0190] Step S1081: The load of the preset measuring point is obtained based on the acceleration and displacement of the preset measuring point, and the load of different preset measuring points is normalized to eliminate the influence caused by different positions of the preset measuring points. The calculation of the load is a conventional technique, so it will not be described in detail.

[0191] Step S1082: Filter the normalized load to obtain a denoised load. For example, the SAE filter of LS-Prepost software can be used to filter out the influence of high-frequency noise.

[0192] Step S1083: Based on the denoised load peak values ​​of each of the preset measuring points, an impact load transmission path diagram is drawn, as shown below. Figure 11 As shown, the peak acceleration is mainly concentrated in the middle section of the cabin and the tip of the wing, while the peak displacement is mainly concentrated at the root of the wing.

[0193] Figure 12 The diagram illustrates the equivalent stress contour map and damage factor contour map of the landing gear-fuselage connection area during the landing process, as described in this application. Figure 12 As shown, in step S109, after obtaining the material damage in the landing gear-fuselage connection area, an equivalent stress cloud map of the landing gear-fuselage connection area during landing is obtained based on the material damage. Figure 12 The landing process stress cloud map and damage factor cloud map are obtained. Specifically, in step S109, based on the JC (Johnson-Cook) constitutive model and corresponding damage model (an existing damage model can be used), and the material damage, the equivalent stress cloud map and damage factor cloud map of the landing gear-fuselage connection area can be obtained. Specifically, the DATABASE keyword of LS-DYNA can be used to output the equivalent stress cloud map and damage factor cloud map based on the JC constitutive model and its damage model, and the obtained material damage. Figure 12 As shown, the maximum damage factor is concentrated in the lower part of the landing gear-fuselage connection area, with a peak value reaching 5.73 × 10⁻⁶. -6 .

[0194] Figure 13 The flowchart illustrates another implementation of the simulation-based load and damage estimation method for heavy landing conditions of civil aircraft according to this application. Figure 13 As shown, the simulation-based load and damage estimation method for heavy landing conditions of civil aircraft according to the second embodiment of this application includes:

[0195] Step S1301: Construct a full-size structural model of the civil aircraft;

[0196] Step S1302: Construct the landing gear model of the civil aircraft;

[0197] Step S1303: Based on the full-size structural model and the landing gear model, construct a fine mesh sub-model for key locations, where the key locations are the landing gear-fuselage connection areas where stress is concentrated.

[0198] Step S1304: Set the heavy landing condition parameters. The heavy landing condition parameters include initial conditions, ground model and tire contact definition. The initial conditions include wing stiffness, aircraft weight, descent speed, heading speed, pitch angle and roll angle.

[0199] Step S1305: Perform a hard landing simulation on the civil aircraft based on the full-size structural model and the hard landing condition parameters;

[0200] Step S1306: Verify the fine mesh sub-model;

[0201] Step S1307: If the verification is successful, obtain the acceleration and displacement of the preset measurement points based on the fine mesh sub-model, and obtain the material damage of the landing gear-body connection area.

[0202] Step S1308: Obtain the impact load transmission path diagram based on the acceleration and displacement of the preset measuring points;

[0203] Step S1309: Based on the material damage, obtain the equivalent stress cloud map and damage factor cloud map of the landing gear-fuselage connection area;

[0204] Step S1310: Perform impact load and damage analysis for different heavy landing conditions;

[0205] Step S1311: Perform damage accumulation analysis.

[0206] Steps S1301-S1309 can be referred to steps S101-S109.

[0207] Specifically, in step S1310, by changing the initial condition parameters of the heavy landing condition and re-simulating, the changes in the impact load transmission path under different heavy landing conditions and the damage status of the fuselage-landing gear connection area under different heavy landing conditions are analyzed to obtain the influence of different initial condition parameters on the impact load transmission path and damage under the heavy landing condition, as well as the damage evolution process. Specifically, step S1310 may include:

[0208] Step S13101: Modify the hard landing condition parameters;

[0209] Step S13102: Based on the full-size structural model and the modified hard landing parameters, perform a new hard landing simulation on the civil aircraft;

[0210] Step S13103: Based on the fine mesh sub-model, obtain the acceleration and displacement of the preset measurement points, and obtain the material damage of the landing gear-fuselage connection area;

[0211] Step S13104: Obtain the impact load transmission path diagram based on the acceleration and displacement of the preset measuring points, and obtain the equivalent stress cloud diagram and damage factor cloud diagram of the landing gear-fuselage connection area based on the material damage.

[0212] Step S13105: Analyze the impact load transfer paths under different heavy landing conditions based on multiple impact load transfer path diagrams obtained after modifying the heavy landing condition parameters multiple times; and...

[0213] Step S13106: Based on the multiple equivalent stress cloud maps and multiple damage factor cloud maps obtained after modifying the heavy landing condition parameters multiple times, analyze the damage situation of the fuselage-landing gear connection area under different heavy landing conditions.

[0214] Specifically, steps S13101-S13104 are repeated multiple times. The number of repetitions can be determined according to the actual analysis requirements. The simulation results of multiple repetitions can obtain multiple impact load transmission path diagrams, multiple equivalent stress cloud diagrams, and multiple damage factor cloud diagrams. Then, step S13105 analyzes the impact load transmission path under different heavy landing conditions based on multiple impact load transmission path diagrams. Step S13106 analyzes the damage situation of the fuselage-landing gear connection area under different heavy landing conditions based on multiple equivalent stress cloud diagrams and multiple damage factor cloud diagrams. Thus, the influence of different initial condition parameters on the attack load and damage, as well as the damage evolution process, are obtained.

[0215] Specifically, in step S1311, after performing one simulation, the rigid ground is reset, the stress of the full-size structural model is initialized, and the sinking velocity in the hard landing condition is set to the initial sinking velocity, with other parameters remaining unchanged. The simulation is then performed again to obtain the material damage in the landing gear-fuselage connection area, and the change in the damage factor of the landing gear-fuselage connection area is obtained. This process is repeated multiple times (the number of times can be determined according to actual analysis needs) to obtain the cumulative damage in the landing gear-fuselage connection area, thus completing the damage accumulation analysis. Specifically, step S1311 may include:

[0216] Step S13111: Create a second rigid ground identical to the first rigid ground under the current first rigid ground, and delete the first rigid ground;

[0217] Step S13112: Set the sinking velocity in the heavy landing condition parameters to the initial sinking velocity;

[0218] Step S13113: Initialize the stress of the full-size structural model, and re-perform a hard landing simulation of the civil aircraft based on the modified sinking speed and the stress-initialized full-size structural model to obtain the material damage of the landing gear-fuselage connection area.

[0219] Step S13114: Based on the material damage, obtain the change in the damage factor of the landing gear-airframe connection area.

[0220] Figure 14 A schematic diagram of the rigid ground during the damage accumulation analysis process of this application is shown, such as... Figure 14 As shown, specifically, in step S13111, a rigid ground 2 identical to the rigid ground 1 (the original rigid ground) is created, and then the rigid ground 1 is deleted, using the rigid ground 2 as the ground for re-landing. Updating the rigid ground and initializing the stress of the full-size structural model can be accomplished using LS-DYNA's restart technology. Figure 15 This paper presents the overall structural response and equivalent stress contour plots of the two hard landing processes during the damage accumulation analysis of this application. Figure 15 The diagram shows the stress cloud map and damage factor cloud map. The changes in the damage factor can be obtained from the overall structural response, equivalent stress cloud map, and damage factor cloud map. By executing steps S13111-S13114 multiple times, the damage accumulation in the landing gear-fuselage connection area under multiple impacts with a rigid ground at the same speed can be obtained, thus completing the damage accumulation effect analysis.

[0221] It should be noted that steps S1310 and S1311 can be performed individually or both. That is, only impact load and damage analysis under different heavy landing conditions can be performed, only damage accumulation analysis can be performed, or both can be performed. The numbering and illustration order of steps S1310 and S1311 are only examples and are not a limitation on the execution order of steps S1310 and S1311.

[0222] This application provides a simulation-based method for estimating the load and damage of civil aircraft during heavy landing conditions. Using the mid-section fuselage as a foundation, a full-scale structural model of the civil aircraft is constructed using a segmented equivalent method. Subsequently, this full-scale structural model is combined with a landing gear model to establish a dual-scale collaborative analysis system. This system includes a coarse-grid parent model derived from the full-scale structural model and fine-grid sub-models constructed for key locations. Furthermore, by setting up multi-condition simulation analysis scenarios for heavy landing of civil aircraft, the method can accurately analyze the transmission law of impact loads while significantly reducing computational resource consumption and time. It also enables quantitative assessment of structural damage at key locations in the landing gear-fuselage connection area. Moreover, it allows for analysis of attack loads and damage evolution processes under different heavy landing conditions, as well as damage accumulation analysis. This overcomes the shortcomings of existing technologies and ultimately provides efficient and accurate technical support for the crashworthiness design and safety risk prediction of civil aircraft structures.

[0223] A second aspect of this application provides a simulation-based system for estimating loads and damage during a heavy landing of a civil aircraft. Figure 16 This paper presents a structural block diagram of one embodiment of the simulation-based load and damage estimation system for heavy landing conditions of civil aircraft, as described in this application. Figure 16 As shown, the simulation-based load and damage estimation system for heavy landing conditions of civil aircraft according to the third embodiment of this application includes:

[0224] Full-size structural model building module 1601 is used to build full-size structural models of civil aircraft;

[0225] The landing gear model construction module 1602 is used to construct the landing gear model of the civil aircraft.

[0226] The fine mesh sub-model construction module 1603 is used to construct fine mesh sub-models for key locations based on the full-size structural model and the landing gear model. The key locations are the landing gear-fuselage connection areas where stress is concentrated.

[0227] The heavy landing condition setting module 1604 is used to set heavy landing condition parameters, which include initial conditions, ground model and tire contact definition. The initial conditions include wing stiffness, aircraft weight, descent speed, yaw speed, pitch angle and roll angle. In one possible implementation, the ground model is a single rigid ground layer, and the tire contact definition is an automatic contact algorithm between the tire and the rigid ground.

[0228] Simulation module 1605 is used to perform a hard landing simulation of the civil aircraft based on the full-size structural model and the hard landing condition parameters;

[0229] Verification module 1606 is used to verify the fine mesh sub-model;

[0230] The data acquisition module 1607 is used to acquire the acceleration and displacement of preset measurement points based on the fine mesh sub-model, and to acquire the material damage of the landing gear-fuselage connection area, if the verification is successful.

[0231] Load estimation module 1608 is used to obtain an impact load transmission path diagram based on the acceleration and displacement of the preset measuring points; and,

[0232] The damage estimation module 1609 is used to obtain the equivalent stress cloud map and damage factor cloud map of the landing gear-aircraft body connection area based on the material damage.

[0233] Specifically, the full-size structural model construction module can be used for:

[0234] The mass of the nose and tail sections is applied to the floor longitudinal beams of the mid-section of the passenger cabin via 12 concentrated mass points. The mid-section of the fuselage includes the central wing box, the mid-wing section, and the landing gear of the civil aircraft. The mid-wing section includes the mid-section of the passenger cabin and the nacelle. The nose section is the fuselage preceding the mid-section of the fuselage, including the nose. The tail section is the fuselage following the mid-section of the fuselage, including the tail.

[0235] Adjust the mass of the 12 concentrated mass points so that the center of gravity of the mid-section fuselage and the line of action of the resultant force of the landing gear are on the same cross section, and the cross section is perpendicular to the fuselage roller axis;

[0236] The material constitutive model is set as a bilinear elastoplastic model, and the skeleton of the middle section of the cabin is modeled using reduced integral shell elements to obtain the skeleton model of the middle section of the cabin.

[0237] The material constitutive model is set as an elastic model. Beam elements are used to model the skeleton of the central wing box and the skeleton of the nacelle, resulting in the central wing box skeleton model and the nacelle skeleton model.

[0238] The reduced integral shell unit is used to model the skin corresponding to the skeleton of the cabin midsection, the central wing box and the nacelle, and the skeleton models of the cabin midsection, the central wing box and the nacelle are connected to the corresponding skin parts.

[0239] Rigid connector units are used to connect and assemble the cabin midsection skeleton model, the central wing box skeleton model, and the nacelle skeleton model after the skin is connected, to obtain the full-size structural model.

[0240] Specifically, the landing gear model construction module can be used for:

[0241] The upper sleeve and lower sleeve of the buffer rod can be considered as a spring unit and a damping unit, respectively, with the spring unit having a spring stiffness of 3 × 10⁻⁶. 5 N / m, the damping coefficient of the damping unit is 3.42×10 5 Ns / m, and the sliding joint of the upper sleeve of the buffer rod and the lower sleeve of the buffer rod is set as a translational joint;

[0242] The tire uses a hyperelastic constitutive material and adopts the Mooney-Rivlin model or the Yeoh model. The tire is coupled to the lower sleeve of the buffer rod through rigid elements. A uniformly distributed load equivalent to air pressure is applied to the inner wall of the tire, and the kinematic pair of the tire is set as a revolute pair.

[0243] The bolted connections in the landing gear-fuselage connection area are simulated using beam elements. The landing gear-fuselage connection area is made of stainless steel, and the stainless steel material is a JC constitutive model that includes strain rate effects.

[0244] The landing gear includes an upper sleeve of the buffer bar, a lower sleeve of the buffer bar, a tire and a landing gear-body connection area. The upper sleeve of the buffer bar is connected to the body by bolts, and the lower sleeve of the buffer bar is connected to the tire through the rigid unit. The landing gear-body connection area is composed of a reinforcing plate and a strut structure.

[0245] Specifically, the landing gear model construction module is used to: employ the Mooney-Rivlin model when the tire is set as an incompressible rubber material with a medium strain range, and employ the Yeoh model when the tire is set as a filler rubber with large deformation and changes with deformation according to the shear model; apply the LS-DYNA JOINT keyword to the upper sleeve and the lower sleeve of the buffer rod for displacement constraint; and apply the LS-DYNA CONTROL_DYNAMIC_RELAXION keyword to stress relaxation settings when a uniformly distributed load is applied to the inner wall of the tire.

[0246] Specifically, the fine mesh sub-model construction module can be used for:

[0247] The full-size structural model and the landing gear model are assembled to obtain a coarse network parent model that includes all the structures of the civil aircraft.

[0248] Extract the mesh surface at the boundary of the key position in the coarse network parent model as the boundary layer, and set the displacement data of all mesh nodes on the boundary layer as the d3interface file to be output;

[0249] Based on the coarse network parent model and the pre-set heavy landing condition parameters, a heavy landing simulation was performed on the civil aircraft to obtain the d3interface file;

[0250] The coarse mesh model, which includes the key positions within the boundary layer envelope of the coarse mesh parent model, is copied into the blank model to obtain the copied mesh model.

[0251] The copied mesh model is redrawn using a hexahedral volume mesh to obtain a redrawn mesh model.

[0252] Using the d3interface file as boundary conditions, a re-landing simulation was performed based on the same re-landing condition parameters and the coarse mesh parent model to obtain the global dynamic response of the entire aircraft and the displacement-time history of the boundary nodes at the key locations.

[0253] The displacement-time history is transferred to the redrawn mesh model to obtain the fine mesh sub-model.

[0254] Specifically, the verification module can be used for:

[0255] Extract the peak ground contact force of the landing gear in the fine mesh sub-model, and calculate the contact force error between the peak ground contact force and the reference peak.

[0256] Extract the first stress peak value and the first displacement peak value of the fine mesh sub-model in the boundary region, and extract the second stress peak value and the second displacement peak value of the coarse mesh parent model in the boundary region;

[0257] Calculate the stress peak error between the first stress peak and the second stress peak, and the displacement peak error between the first displacement peak and the second displacement peak;

[0258] If the contact force error is less than or equal to a first preset threshold, the peak stress error is less than or equal to a second preset threshold, and the peak displacement error is less than or equal to a third preset threshold, then the verification is successful. The boundary region is the area formed by moving one or two units towards the fine mesh sub-model from the boundary of the connection area between the fine mesh sub-model and the coarse mesh parent model. The first, second, and third preset thresholds can be the same or different.

[0259] Specifically, the load estimation module can be used for:

[0260] The load at the preset measuring point is obtained based on the acceleration and displacement of the preset measuring point, and the load at different preset measuring points is normalized.

[0261] The normalized load is filtered to obtain the denoised load;

[0262] Based on the denoised load peak values ​​at each of the preset measurement points, the impact load transmission path diagram is obtained.

[0263] Specifically, the damage estimation module can be used for:

[0264] Based on the JC constitutive model and corresponding damage model of the landing gear-fuselage connection area, as well as the material damage, the equivalent stress cloud map and damage factor cloud map of the landing gear-fuselage connection area are obtained.

[0265] Figure 17 This paper presents a structural block diagram of another embodiment of the simulation-based civil aircraft hard landing load and damage estimation system of this application, as shown in the figure. Figure 17 As shown, the simulation-based load and damage estimation system for heavy landing conditions of civil aircraft according to the fourth embodiment of this application includes:

[0266] Full-size structural model building module 1701 is used to build full-size structural models of civil aircraft;

[0267] The landing gear model construction module 1702 is used to construct the landing gear model of the civil aircraft.

[0268] The fine mesh sub-model construction module 1703 is used to construct fine mesh sub-models for key locations based on the full-size structural model and the landing gear model. The key locations are the landing gear-fuselage connection areas where stress is concentrated.

[0269] The heavy landing condition setting module 1704 is used to set heavy landing condition parameters, which include initial conditions, ground model and tire contact definition. The initial conditions include wing stiffness, aircraft weight, descent speed, yaw speed, pitch angle and roll angle. In one possible implementation, the ground model is a single rigid ground layer, and the tire contact definition is an automatic contact algorithm between the tire and the rigid ground.

[0270] Simulation module 1705 is used to perform a hard landing simulation of the civil aircraft based on the full-size structural model and the hard landing condition parameters;

[0271] Verification module 1706 is used to verify the fine mesh sub-model;

[0272] The data acquisition module 1707 is used to acquire the acceleration and displacement of preset measurement points based on the fine mesh sub-model, and to acquire the material damage of the landing gear-fuselage connection area, if the verification is successful.

[0273] The load estimation module 1708 is used to obtain the impact load transmission path diagram based on the acceleration and displacement of the preset measuring points;

[0274] Damage estimation module 1709 is used to obtain equivalent stress cloud map and damage factor cloud map of the landing gear-fuselage connection area based on the material damage.

[0275] The 1710 module for load and damage analysis is used to perform impact load and damage analysis under different heavy landing conditions.

[0276] Damage accumulation analysis module 1711 is used to perform damage accumulation analysis.

[0277] Specifically, the load and damage analysis module can be used for:

[0278] Modify the parameters for the hard landing condition;

[0279] Based on the full-size structural model and the modified hard landing parameters, a hard landing simulation was performed on the civil aircraft.

[0280] Based on the fine mesh sub-model, the acceleration and displacement of preset measurement points are obtained, as well as the material damage of the landing gear-fuselage connection area is obtained;

[0281] An impact load transmission path diagram is obtained based on the acceleration and displacement of the preset measuring points, and an equivalent stress cloud diagram and damage factor cloud diagram of the landing gear-fuselage connection area are obtained based on the material damage.

[0282] Based on multiple impact load transmission path diagrams obtained after modifying the parameters of the hard landing condition multiple times, the impact load transmission paths under different hard landing conditions are analyzed; and...

[0283] Based on multiple equivalent stress cloud maps and multiple damage factor cloud maps obtained after modifying the parameters of the hard landing condition multiple times, the damage situation of the fuselage-landing gear connection area under different hard landing conditions is analyzed.

[0284] Specifically, the damage accumulation analysis module can be used for:

[0285] Create a second rigid ground identical to the first rigid ground under the current first rigid ground, and delete the first rigid ground;

[0286] Set the sinking velocity in the heavy landing condition parameters to the initial sinking velocity;

[0287] The stress of the full-size structural model is initialized, and a hard landing simulation of the civil aircraft is performed based on the modified sinking speed and the stress-initialized full-size structural model to obtain the material damage of the landing gear-fuselage connection area.

[0288] The change in the damage factor of the landing gear-fuselage connection area is obtained based on the material damage.

[0289] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process and related descriptions of the system described above can be referred to the corresponding processes in the foregoing method embodiments, and therefore will not be repeated here.

[0290] The simulation-based load and damage estimation system for heavy landing conditions of civil aircraft provided in this application adopts a piecewise equivalent method to construct a full-size structural model. Combined with the landing gear model, a dual-scale collaborative analysis system is built, which includes a coarse-mesh parent model and a fine-mesh sub-model for key locations. Through multi-condition heavy landing simulation, it can significantly reduce computational resources and time, accurately analyze the impact load transmission law, quantitatively assess the damage in the landing gear-aircraft connection area, analyze the attack load and damage evolution under different heavy landing conditions, and perform damage accumulation effect analysis. It overcomes the shortcomings of existing technologies and provides efficient and accurate technical support for the safety assessment of civil aircraft.

[0291] It should be noted that the video human behavior recognition system provided in the above embodiments is only illustrated by the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the modules or steps in the embodiments of this application can be further decomposed or combined. For example, the modules in the above embodiments can be merged into one module, or further divided into multiple sub-modules to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of this application are only for distinguishing the various modules or steps and are not considered as an improper limitation of this application.

[0292] In a third aspect of this application, an electronic device is also provided, the electronic device comprising: at least one processor; and a memory communicatively connected to at least one of the processors; wherein the memory stores instructions executable by the processor, the instructions being executed by the processor to implement the above-described simulation-based method for estimating loads and damage under heavy landing conditions for civil aircraft.

[0293] In a fourth aspect of this application, a computer-readable storage medium is also provided, the computer-readable storage medium storing computer instructions for execution by the computer to implement the above-described simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft.

[0294] In a fifth aspect of this application, a computer program product containing instructions is also provided, which, when executed by a computer device, causes the computer device to perform the simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft.

[0295] Those skilled in the art will recognize that the modules and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. The programs corresponding to the software modules and method steps can be placed in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. To clearly illustrate the interchangeability of electronic hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in electronic hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0296] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0297] The terms “first”, “second”, etc., are used to distinguish similar objects, not to describe or indicate a specific order or sequence.

[0298] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.

[0299] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A simulation-based method for estimating loads and damage during a heavy landing of a civil aircraft, characterized in that, include: Construct a full-scale structural model of the civil aircraft; Construct a landing gear model of the aforementioned civil aircraft; Based on the full-size structural model and the landing gear model, a fine mesh sub-model is constructed for the key locations, which are the stress-concentrated landing gear-fuselage connection areas. Set the parameters for the hard landing condition, which include initial conditions, ground model and tire contact definition. The initial conditions include wing stiffness, aircraft weight, descent speed, yaw speed, pitch angle and roll angle. Based on the full-size structural model and the hard landing parameters, a hard landing simulation of the civil aircraft was performed. Verify the fine mesh sub-model; If the verification is successful, the acceleration and displacement of the preset measurement points are obtained based on the fine mesh sub-model, as well as the material damage of the landing gear-fuselage connection area; The impact load transmission path diagram is obtained based on the acceleration and displacement of the preset measuring points; and... Based on the material damage, the equivalent stress cloud map and damage factor cloud map of the landing gear-airframe connection area are obtained.

2. The method as described in claim 1, characterized in that, The construction of the full-size structural model of the civil aircraft includes: The mass of the nose and tail sections is applied to the floor longitudinal beams of the mid-section of the passenger cabin via 12 concentrated mass points. The mid-section of the fuselage includes the central wing box, the mid-wing section, and the landing gear of the civil aircraft. The mid-wing section includes the mid-section of the passenger cabin and the nacelle. The nose section is the fuselage preceding the mid-section of the fuselage, including the nose. The tail section is the fuselage following the mid-section of the fuselage, including the tail. Adjust the mass of the 12 concentrated mass points so that the center of gravity of the mid-section fuselage after removing the landing gear is on the same cross-section as the line of action of the resultant force of the landing gear, and the cross-section is perpendicular to the fuselage roller axis. The material constitutive model is set as a bilinear elastoplastic model, and the skeleton of the middle section of the cabin is modeled using reduced integral shell elements to obtain the skeleton model of the middle section of the cabin. The material constitutive model is set as an elastic model. Beam elements are used to model the skeleton of the central wing box and the skeleton of the nacelle, resulting in the central wing box skeleton model and the nacelle skeleton model. The reduced integral shell unit is used to model the skin corresponding to the skeleton of the cabin midsection, the central wing box and the nacelle, and the skeleton models of the cabin midsection, the central wing box and the nacelle are connected to the corresponding skin parts. Rigid connector units are used to connect and assemble the cabin midsection skeleton model, the central wing box skeleton model, and the nacelle skeleton model after the skin is connected, to obtain the full-size structural model.

3. The method as described in claim 1, characterized in that, The construction of the landing gear model of the civil aircraft includes: The upper sleeve and lower sleeve of the buffer rod can be considered as a spring unit and a damping unit, respectively, with the spring unit having a spring stiffness of 3 × 10⁻⁶. 5 N / m, the damping coefficient of the damping unit is 3.42×10 5 Ns / m, and the sliding joint of the upper sleeve of the buffer rod and the lower sleeve of the buffer rod is set as a translational joint; The tire uses a hyperelastic constitutive material and adopts the Mooney-Rivlin model or the Yeoh model. The tire is coupled to the lower sleeve of the buffer rod through rigid elements. A uniformly distributed load equivalent to air pressure is applied to the inner wall of the tire, and the kinematic pair of the tire is set as a revolute pair. The bolted connections in the landing gear-fuselage connection area are simulated using beam elements. The landing gear-fuselage connection area is made of stainless steel, and the stainless steel material is a JC constitutive model that includes strain rate effects. The landing gear includes an upper sleeve of the buffer bar, a lower sleeve of the buffer bar, a tire and a landing gear-body connection area. The upper sleeve of the buffer bar is connected to the body by bolts, and the lower sleeve of the buffer bar is connected to the tire through the rigid unit. The landing gear-body connection area is composed of a reinforcing plate and a strut structure.

4. The method as described in claim 3, characterized in that, When the tire is set as an incompressible rubber material with a medium strain range, the Mooney-Rivlin model is used; when the tire is set as a filler rubber with large deformation and its deformation varies according to the shear model, the Yeoh model is used. The upper and lower sleeves of the buffer rod are subjected to displacement constraints using the LS-DYNA JOINT keyword. Furthermore, when a uniformly distributed load is applied to the inner wall of the tire, stress relaxation is set using the LS-DYNA CONTROL_DYNAMIC_RELAXION keyword. The ground model is a single-layer rigid ground, and the tire contact is defined as the contact algorithm between the tire and the rigid ground, which is an automatic contact algorithm.

5. The method as described in claim 1, characterized in that, The construction of fine-mesh sub-models for key locations based on the full-size structural model and the landing gear model includes: The full-size structural model and the landing gear model are assembled to obtain a coarse network parent model that includes all the structures of the civil aircraft. Extract the mesh surface at the boundary of the key position in the coarse network parent model as the boundary layer, and set the displacement data of all mesh nodes on the boundary layer as the d3interface file to be output; Based on the coarse network parent model and the pre-set heavy landing condition parameters, a heavy landing simulation was performed on the civil aircraft to obtain the d3interface file; The coarse mesh model, which includes the key positions within the boundary layer envelope of the coarse mesh parent model, is copied into the blank model to obtain the copied mesh model. The copied mesh model is redrawn using a hexahedral volume mesh to obtain a redrawn mesh model. Using the d3interface file as boundary conditions, a re-landing simulation was performed based on the same re-landing condition parameters and the coarse mesh parent model to obtain the global dynamic response of the entire aircraft and the displacement-time history of the boundary nodes at the key locations. The displacement-time history is transferred to the redrawn mesh model to obtain the fine mesh sub-model.

6. The method as described in claim 5, characterized in that, The verification of the fine mesh sub-model includes: Extract the peak ground contact force of the landing gear in the fine mesh sub-model, and calculate the contact force error between the peak ground contact force and the reference peak. Extract the first stress peak value and the first displacement peak value of the fine mesh sub-model in the boundary region, and extract the second stress peak value and the second displacement peak value of the coarse mesh parent model in the boundary region; Calculate the stress peak error between the first stress peak and the second stress peak, and the displacement peak error between the first displacement peak and the second displacement peak; If the contact force error is less than or equal to the first preset threshold, the peak stress error is less than or equal to the second preset threshold, and the peak displacement error is less than or equal to the third preset threshold, then the verification is successful. The boundary region is the area formed by moving one or two units from the boundary of the connection area between the fine mesh sub-model and the coarse mesh parent model toward the fine mesh sub-model.

7. The method as described in claim 1, characterized in that, The method of obtaining the impact load transmission path diagram based on the acceleration and displacement of the preset measuring points includes: The load at the preset measuring point is obtained based on the acceleration and displacement of the preset measuring point, and the load at different preset measuring points is normalized. The normalized load is filtered to obtain the denoised load; Based on the denoised load peak values ​​at each of the preset measurement points, the impact load transmission path diagram is obtained; The process of obtaining the equivalent stress cloud map and damage factor cloud map of the landing gear-fuselage connection area based on the material damage includes: Based on the JC constitutive model and corresponding damage model of the landing gear-fuselage connection area, as well as the material damage, the equivalent stress cloud map and damage factor cloud map of the landing gear-fuselage connection area are obtained.

8. The method according to any one of claims 1-7, characterized in that, Also includes: Modify the parameters for the hard landing condition; Based on the full-size structural model and the modified hard landing parameters, a hard landing simulation was performed on the civil aircraft. Based on the fine mesh sub-model, the acceleration and displacement of preset measurement points are obtained, as well as the material damage of the landing gear-fuselage connection area is obtained; An impact load transmission path diagram is obtained based on the acceleration and displacement of the preset measuring points, and an equivalent stress cloud diagram and damage factor cloud diagram of the landing gear-fuselage connection area are obtained based on the material damage. Based on the multiple impact load transmission path diagrams obtained after modifying the parameters of the hard landing condition multiple times, the impact load transmission paths under different hard landing conditions are analyzed. as well as, Based on multiple equivalent stress cloud maps and multiple damage factor cloud maps obtained after modifying the parameters of the hard landing condition multiple times, the damage situation of the fuselage-landing gear connection area under different hard landing conditions is analyzed.

9. The method according to any one of claims 1-7, characterized in that, Also includes: Create a second rigid ground identical to the first rigid ground under the current first rigid ground, and delete the first rigid ground; Set the sinking velocity in the heavy landing condition parameters to the initial sinking velocity; The stress of the full-size structural model is initialized, and a hard landing simulation of the civil aircraft is performed based on the modified sinking speed and the stress-initialized full-size structural model to obtain the material damage of the landing gear-fuselage connection area. The change in the damage factor of the landing gear-fuselage connection area is obtained based on the material damage.

10. A simulation-based load and damage estimation system for heavy landing conditions of civil aircraft, characterized in that, include: Full-size structural model building module, used to build full-size structural models of civil aircraft; The landing gear model building module is used to build the landing gear model of the civil aircraft. The fine mesh sub-model construction module is used to construct fine mesh sub-models for key locations based on the full-size structural model and the landing gear model. The key locations are the landing gear-fuselage connection areas where stress is concentrated. The heavy landing condition setting module is used to set the heavy landing condition parameters, which include initial conditions, ground model and tire contact definition. The initial conditions include wing stiffness, aircraft weight, descent speed, yaw speed, pitch angle and roll angle. The simulation module is used to perform a hard landing simulation of the civil aircraft based on the full-size structural model and the hard landing condition parameters; The verification module is used to verify the fine mesh sub-model; The data acquisition module is used to acquire the acceleration and displacement of preset measurement points based on the fine mesh sub-model, and to acquire the material damage of the landing gear-fuselage connection area, if the verification is successful. The load estimation module is used to obtain the impact load transmission path diagram based on the acceleration and displacement of the preset measuring points; as well as, The damage estimation module is used to obtain the equivalent stress cloud map and damage factor cloud map of the landing gear-aircraft connection area based on the material damage.

Images