Aero-engine external pipeline clamp support design and simulation method for resisting vibration-impact combined load

Abstract

The invention discloses a design and simulation method of an aero-engine external pipeline clamp support for resisting vibration-impact combined load, and relates to vibration and impact protection of aero-engines and external pipelines. A composite vibration isolation unit composed of metal rubber and annular cavity particle damping is introduced into the connecting position of a traditional clamp and a cartridge receiver, and a mass block-metal rubber-particle damping parallel supporting structure is constructed. Establishing an external pipeline finite element model, and obtaining an engine vibration load and an impact acceleration time history similar to carrier-based aircraft landing; the equivalent stiffness and nonlinear particle damping parameters of the composite vibration isolation unit are identified, and a mass-spring-nonlinear damping kinetic model is established; and a composite vibration isolation unit is equivalent to a nonlinear spring-damping element to be coupled into the pipeline-hoop-casing finite element model, and response analysis and parameter optimization design under the vibration-impact combined working condition are carried out. The peak acceleration and the bending stress of an external pipeline are reduced, and the accuracy and the engineering efficiency of anti-vibration and anti-impact design are improved.

Description

Technical Field

[0001] This invention belongs to the field of vibration and shock protection technology for aero-engines and their external pipelines, and in particular relates to a design and simulation method for aero-engine external pipeline clamp brackets for resisting combined vibration and shock loads. Background Technology

[0002] External piping of an aircraft engine serves as a conduit for the delivery of fuel, lubricating oil, hydraulic oil, and gaseous media. It is typically fixed to the outer surface of the engine casing using multiple clamps or brackets. Due to space and installation constraints, external piping systems often take the form of U-shaped, Z-shaped, or L-shaped multi-bend pipes and are connected to the casing via multiple clamps.

[0003] During engine operation, the casing experiences wide-frequency vibrations due to multiple excitation sources, including rotor imbalance, aerodynamic excitation, and external attachments. Consequently, external piping is subjected to complex base vibrations and fluid-structure interaction. Numerous studies have shown that the dynamic characteristics of multi-clamp supported piping are significantly affected by clamp stiffness and damping, preload, and arrangement. Current engineering practices often employ metal clamps or rubber bushing clamps for direct rigid connection to the casing. The support characteristics between the clamps and piping can be approximated as linear or piecewise linear springs, with limited energy dissipation capacity, primarily suitable for low-to-medium amplitude vibration environments.

[0004] For carrier-based aircraft and other aircraft subjected to extreme conditions such as arresting gear, catapult launch, and deck impact, their engines and external piping will be subjected to large-amplitude, high-acceleration impact loads in a very short time, resulting in strong vibration-impact coupling in the casing-piping system. Traditional rigid clamps or simple rubber vibration isolation structures are prone to the following problems under such impact conditions: a sharp increase in bending stress at certain bends and welded joints of the piping, leading to low-cycle fatigue or even instantaneous failure; local stress concentration at the contact interfaces between the clamp and the casing, and between the clamp and the piping, resulting in bushing damage, clamp breakage, or cracking of the casing connection holes; increasing stiffness is beneficial for stabilizing piping vibration, but it will amplify the impact response, and relying solely on traditional viscoelastic materials is difficult to ensure long-term reliable operation in high-temperature and fuel-intensive environments.

[0005] Existing literature on finite element modeling and vibration response analysis of multi-clamp piping systems is relatively mature. Timoshenko beam elements are typically used to discretize the piping, treating the clamps as equivalent to spring-damped supports, and studying their modal characteristics and responses under base harmonic or random vibrations. However, the impact-resistant design and simulation methods for aero-engine external piping under high-impact conditions such as carrier-based aircraft landings are still imperfect. There is a lack of clamp support structures and supporting design processes that can simultaneously consider combined vibration and impact loads, while also possessing high damping and high reliability.

[0006] In recent years, novel energy-dissipating materials such as metal rubber and particulate damping have attracted attention in the aerospace field. Metal rubber possesses adjustable stiffness and good hysteretic damping, but its energy dissipation capacity remains limited when used alone under high-impact conditions. Particulate damping, on the other hand, relies on collisions and friction between particles and between particles and cavity walls to achieve strong nonlinear energy dissipation, exhibiting particularly good energy dissipation capabilities for transient impacts, but requires reasonable structural encapsulation and parameter matching. How to effectively integrate metal rubber and particulate damping into external pipeline clamp supports, and establish an integrated design and simulation method for combined vibration-shock conditions, is a pressing technical problem that needs to be solved. Summary of the Invention

[0007] The purpose of this invention is to address the fatigue damage and impact failure that easily occur in the external pipelines of aero-engines under combined vibration and shock loads. It provides an external pipeline clamp support structure based on a metal-rubber-particle damping composite vibration isolation unit, and on this basis, constructs a design and simulation method that can be used for multi-clamp pipeline systems to achieve integrated optimization for both vibration and shock conditions. It is particularly suitable for high-impact environments such as carrier-based aircraft landing and hard landing.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] A design and simulation method for external piping clamp supports of aero-engines to resist combined vibration and shock loads includes the following steps:

[0010] Step 1: Introduce a composite vibration isolation unit consisting of metal rubber and annular cavity particle damping between the casing and the external pipeline clamps. A wide-band vibration control and strong impact energy dissipation are achieved through a multi-point supported mass block-metal rubber-particle damping structure.

[0011] Step 2: Based on the experiment, establish a mass-spring-nonlinear damping dynamic model of the composite vibration isolation unit, focusing on characterizing the collision energy dissipation characteristics of the annular cavity particles under impact conditions;

[0012] Step 3: Equivalent the composite vibration isolation unit to a nonlinear spring-damped support and couple it to the finite element model of the multi-clamp external pipeline to construct an overall dynamic model for the combined vibration-shock working condition;

[0013] Step 4: Using a combination of vibration frequency response analysis and shock transient analysis, a joint simulation was conducted on typical engine vibration conditions and superimposed carrier-based aircraft landing impact conditions to evaluate pipeline stress, displacement and acceleration response.

[0014] Step 5: Through multi-objective optimization design, optimize parameters such as metal rubber pre-compression amount, particle filling rate and material, number and position of vibration isolation units, so as to obtain a clamp bracket design scheme with good vibration isolation effect under vibration condition, strong impact attenuation capability under impact condition, and limited mass and volume.

[0015] In step 1, a composite vibration isolation unit consisting of metal rubber and annular cavity particle damping is introduced between the casing and the external pipeline clamps. This multi-point supported mass block-metal rubber-particle damping structure achieves broadband vibration control and strong impact energy dissipation. This step forms the structural basis for the vibration and impact protection of this invention. Its core lies in combining the hysteretic damping characteristics of metal rubber with the impact energy dissipation characteristics of particle damping. Through a parallel structure with multi-point supports, the device can rely on the metal rubber to provide stable damping support under broadband vibration conditions, and under strong impact conditions, energy can be dissipated through the collision and friction of particles within the annular cavity, thus simultaneously meeting the dual requirements of vibration control and impact protection.

[0016] In step 1, the external pipeline is a U-shaped, Z-shaped or L-shaped bend structure supported by multiple clamps, and the pipeline is connected to the aero-engine casing through three or more clamps; the finite element model uses Timoshenko beam elements to uniformly model the straight pipe section and the bend section, and discretizes the clamp width effect into multi-point spring-damped supports arranged along the pipe axis.

[0017] In step 2, a mass-spring-nonlinear damping dynamic model of the composite vibration isolation unit is established based on the experiments, focusing on characterizing the collision energy dissipation characteristics of the annular cavity particles under impact conditions. This step is a key prerequisite for achieving accurate simulation analysis. It requires obtaining the force-displacement and force-velocity hysteresis curves of the composite vibration isolation unit under different preloads and particle filling rates through quasi-static compression tests, vibration table tests, and impact table tests. Then, the equivalent stiffness and nonlinear damping parameters are fitted using the Bouc-Wen model or a piecewise linear hysteresis model, ultimately establishing a dynamic model that accurately reflects the nonlinear characteristics of particle collision energy dissipation, providing reliable model support for subsequent finite element coupling. Specifically, the nonlinear damping force Fz of the composite vibration isolation unit is generated jointly by particle damping and internal friction of the metal-rubber. The particle damping part is characterized by an exponential or piecewise linear velocity function related to the relative velocity amplitude, which can significantly increase the damping force to dissipate impact energy under large displacement and high acceleration impact. The mass block is considered as a concentrated mass m, and the vibration system base is considered as the moving boundary. The base displacement is... The displacement of the mass block is The composite vibration isolation unit consists of an equivalent linear spring force. and nonlinear damping force The parallel system is characterized by the following differential equations of motion:

[0018]

[0019] The above model is discretized into frequency domain or time domain form for coupling with the external pipeline finite element model.

[0020] In step 3, the composite vibration isolation unit is equivalent to a nonlinear spring-damped support and coupled to the finite element model of the multi-clamp external pipeline to construct an overall dynamic model for the combined vibration-shock condition. This step requires first completing the finite element modeling of the multi-clamp external pipeline, determining the pipeline geometric parameters and support node positions, and then replacing the rigid constraints at each clamp with equivalent nonlinear spring-damped units. The contact between the clamp body and the pipeline is characterized by a piecewise linear stiffness model, where the stiffness changes with the clamp tightening torque to reflect the bilinear support characteristics of the clamp during loading and unloading. At the same time, the combined load input requirements are clarified. The impact acceleration time history is the measured vertical acceleration time history at the casing or casing mounting frame during carrier landing, or an equivalent half-sine pulse, trapezoidal pulse, or their superimposed waveform constructed according to the carrier landing impact test standard. Combining this impact load with the engine vibration load, an integrated dynamic model of casing-composite clamp support-external pipeline is built from top to bottom to achieve precise coupling between structure and load.

[0021] In step 4, a combination of vibration frequency response analysis and shock transient analysis is used to conduct joint simulation of typical engine vibration conditions and superimposed carrier-based aircraft landing impact conditions to evaluate pipeline stress, displacement and acceleration response. This step requires simulation calculation in stages: vibration-shock joint condition response analysis includes: (1) under engine steady-state conditions, frequency response analysis of narrow-band or broadband random vibration of the base is performed to obtain the modal characteristics and vibration response of the pipeline-clamp system in the range of 0 to 1500 Hz; (2) based on engine vibration, the landing impact time history is superimposed to perform transient response analysis on the overall model to evaluate the weakening effect of the composite clamp bracket on the pipeline impact response. The coupled modes and key response modes were identified through modal strain energy analysis. First, frequency response analysis was performed on the steady-state vibration condition of the engine to obtain the modal characteristics of the pipeline system and verify whether it avoids the main excitation frequency. Then, the carrier-based aircraft landing impact time history was superimposed to perform transient response analysis, calculate the stress, peak displacement and mass block acceleration response of the key section of the pipeline, and comprehensively evaluate the vibration reduction and impact resistance effect of the composite clamp bracket.

[0022] In step 5, through multi-objective optimization design, the parameters such as the pre-compression amount of metal rubber, particle filling rate and material, and the number and position of vibration isolation units are optimized to obtain a clamp support design scheme that has good vibration isolation effect under vibration conditions, strong impact attenuation ability under impact conditions, and limited mass and volume. This step needs to clarify the optimization objectives and constraints such as pipeline peak stress, clamp connection reaction force, and support mass; the design evaluation indicators include at least: (1) the equivalent stress of any section of the external pipeline under the landing impact condition does not exceed the predetermined safety factor of 1.25 of the material yield strength; (2) the maximum reaction force at the connection between the clamp and the casing is lower than the bearing limit of the casing connection structure; (3) the mass of the composite clamp support does not exceed 110% of the mass of the original rigid support; (4) compared with the benchmark scheme without composite vibration isolation units, the peak acceleration or peak stress of the key nodes of the pipeline is reduced by no less than 30%; by adjusting the design variables and conducting multiple rounds of simulation iteration, the optimal parameter combination that takes into account various performance indicators is finally selected to form a clamp support design scheme that can be directly applied to engineering practice.

[0023] An external piping clamp bracket for aero-engines used to resist combined vibration and shock loads, comprising:

[0024] The vibration system base is a metal disc or plate structure that is fixedly connected to the aircraft engine casing, with bolt holes for mounting composite vibration isolation units provided on its outer edge or at specific locations;

[0025] The mass block, arranged above the base of the vibration system, is cylindrical or frustum-shaped, with mounting surfaces on its top or side for fixing external pipe clamps.

[0026] Several composite vibration isolation units are symmetrically arranged in a circumferential or rectangular arrangement between the base of the vibration system and the mass block. Each composite vibration isolation unit consists of a lower pad, a lower metal rubber component, an annular cavity particle damping layer, an upper metal rubber component, and an upper pad arranged sequentially from bottom to top, and is clamped together as a whole by a central bolt.

[0027] The center bolt is a high-strength bolt. Its lower end is connected to the base of the vibration system, and its upper end is connected to the mass block. It is used to press the metal rubber parts and the annular cavity particle damping layer under the action of a predetermined preload to form a multi-point supported nonlinear spring-damping system.

[0028] Furthermore, the annular cavity particle damping layer is a closed metal annular cavity filled with at least one of steel shot, ceramic particles or metal powder, with a particle filling rate of 30% to 80%. Under impact load, the particles collide and rub violently with each other and with the cavity wall to dissipate impact energy and achieve impact protection for external pipelines.

[0029] Furthermore, the clamp bracket is installed between the external pipes and the casing of the aircraft engine of a carrier-based aircraft or an aircraft with similar landing impact conditions, and is used in impact environments such as arrested landing, catapult takeoff, or large deck turbulence of carrier-based aircraft.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1) Integrated Vibration-Shock Design: This design simultaneously considers engine vibration and carrier-based aircraft landing impact within a unified dynamic model, enabling a comprehensive evaluation of the vibration and impact responses of external pipeline clamp supports. This avoids the problems of separate verification and fragmentation inherent in traditional designs. Compared to traditional step-by-step verification methods, the integrated design reduces the overall dynamic response prediction error of the pipeline system by 15%–25%. While maintaining support strength, cross-condition collaborative optimization allows for a more uniform distribution of overall pipeline structural margins and reduces local stress concentration by over 20%.

[0032] 2) Enhanced Impact Resistance Through Particle Collision Energy Dissipation: By arranging annular cavity particle damping layers between the metal and rubber components, the device exhibits high-damping elastic support under small vibrations. Under large impacts, the particles undergo intense collisions and friction, forming strong nonlinear damping. This significantly reduces peak acceleration and stress at pipes and clamps, making it particularly suitable for short-term, high-impact conditions such as carrier landings. Under large-load impacts (e.g., acceleration loads exceeding 15g) such as carrier landings, the strong nonlinear energy dissipation mechanism of the particle damping layer can reduce peak acceleration at key pipe nodes by 30%–55% and peak stress by 25%–40%. Its damping ratio dynamically increases with amplitude, resulting in an energy dissipation density 1.5–2.2 times higher than that of a pure metal-rubber structure.

[0033] 3) Applicable to complex pipeline systems with multiple clamps: Timoshenko beam elements and equivalent spring-damped supports are used to model the external pipelines with multiple clamps. It can adapt to various complex spatial pipeline forms such as U-shape, Z-shape, and L-shape. Furthermore, the computational efficiency is improved through segmented modeling and substructure integration, making it suitable for rapid iteration in the engineering design stage.

[0034] 4) Adjustable parameters and ease of engineering implementation: By adjusting the bolt preload, metal-rubber density, particle type and filling rate, as well as the number and arrangement of composite vibration isolation units, the equivalent stiffness and damping can be controlled within a wide range, facilitating customized design based on the environmental loads of different engine models and installation locations. By adjusting the preload and particle filling rate, the equivalent stiffness of the bracket can be adjusted by 3 to 5 times. This high adjustability allows the same basic configuration to adapt to various engine operating conditions, significantly reducing the customized development cost of different bracket types.

[0035] 5) Simulation-Experiment Closed-Loop Verification: The design and simulation method provided by this invention can be combined with pipeline vibration test, clamp stiffness and damping test and other means to realize model parameter identification and design scheme verification, improve the reliability of external pipeline vibration and impact resistance design, and significantly reduce the risk of physical prototype test failure, shortening the R&D cycle by 3 to 6 months. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of a composite vibration isolation unit structure based on metal rubber and annular particle damping. In the diagram, 1-lower gasket, 2-lower end metal rubber component, 3-annular cavity particle damping layer, 4-upper end metal rubber component, 5-upper gasket, and 6-center bolt.

[0037] Figure 2 This is a schematic diagram of the equivalent mass-spring-nonlinear damping dynamic model of the composite vibration isolation unit.

[0038] Figure 3 This is a schematic diagram of the overall structure of an external pipeline clamp bracket for an aero-engine that resists combined vibration and shock loads according to the present invention. 7 represents the vibration system base, and 9 represents the composite vibration isolation unit.

[0039] Figure 4 The results of modal tests based on this invention are compared. The dashed line represents the traditional rigid clamp solution, and the solid line represents the composite vibration isolation clamp solution of this invention. The horizontal axis represents frequency, and the vertical axis represents displacement response amplitude.

[0040] Figure 5 This is a flowchart of the vibration-shock joint simulation design for aero-engine piping according to the present invention. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0042] A design and simulation method for external piping clamp supports of aero-engines for resisting combined vibration and shock loads, including:

[0043] Step 1: Modeling the Multi-Clamp External Piping System: Based on the actual layout of the aero-engine's external piping, determine the piping geometry, bend radius, branch connection relationships, and clamp support positions. Establish a three-dimensional finite element topology model of the external piping based on Timoshenko beam elements, and define each clamp position as a support node connected to the engine casing. The external piping is a U-shaped, Z-shaped, or L-shaped bend structure supported by multiple clamps, and the piping is connected to the aero-engine casing through three or more clamps. The finite element model uses Timoshenko beam elements to uniformly model straight and bend sections, and discretizes the clamp width effect as multi-point spring-damped supports arranged along the pipe axis. The aero-engine piping vibration-shock co-simulation design process is as follows: Figure 5 As shown, the system includes three core modules: A) system modeling and load definition, B) vibration isolator characteristic identification, and C) coupled simulation and optimization closed-loop. First, a three-dimensional geometric topology model of the external piping of the aero-engine is performed based on Timoshenko beam elements. Then, two types of excitation loads are simultaneously acquired: the acceleration spectrum or equivalent harmonic excitation of the engine's steady-state vibration, and the measured acceleration time history or equivalent pulse waveform of the carrier-based aircraft's landing impact. A complete finite element model of the piping is established by combining the piping topology. Next, vibration isolator characteristic identification is performed. First, the composite vibration isolation clamp structure, including core energy-dissipating components such as a metal-rubber layer and annular cavity particle damping layer, is identified. Then, the force-displacement and force-velocity hysteresis curves of the composite vibration isolation unit 9 under different preloads and particle filling rates are measured through quasi-static compression tests and shaking table / impact table tests. Finally, the Bouc-Wen model or piecewise linear hysteresis model is used to fit the test data to identify the equivalent linear stiffness and non-linear stiffness. Linear damping parameters are used to establish an equivalent dynamic model that can accurately characterize the energy dissipation characteristics of particle collisions. Finally, the simulation and optimization closed-loop module, as the core output of the entire simulation design, first couples the finite element model of the pipeline with the nonlinear clamp dynamic model to construct an overall dynamic model of the casing-composite clamp bracket-external pipeline. Then, simulation calculations are carried out in stages. First, frequency response analysis is performed on the engine steady-state vibration to obtain the modal characteristics of the pipeline system. Then, the carrier-based aircraft landing impact time history is superimposed to perform transient response analysis to obtain the stress, displacement, and acceleration response of key sections of the pipeline. Finally, the peak stress, acceleration, and clamp reaction force of the pipeline are used as evaluation indicators to determine whether the design requirements are met. If not, the preload, particle filling rate, metal rubber density, and other design variables are adjusted, and the system returns to the B vibration isolator characteristic identification module to re-identify parameters and iterate the simulation. If the requirements are met, the final optimal clamp bracket design scheme is output.

[0044] Step 2, Vibration and Shock Combined Load Acquisition: Under typical engine speed conditions, acquire the vibration acceleration spectrum or equivalent harmonic excitation of the casing; simultaneously, based on carrier-based aircraft landing, hard landing, or similar shock conditions, acquire or construct the vertical shock acceleration time history or shock response spectrum of the casing mounting point as the excitation input for the external pipeline base; the shock acceleration time history is the measured vertical acceleration time history at the casing or casing mounting frame during carrier-based aircraft landing, or an equivalent half-sine pulse, trapezoidal pulse, or their superimposed waveform constructed according to the carrier-based aircraft landing shock test standard.

[0045] Step 3, Composite vibration isolation clamp bracket structure design: (e.g.) Figure 3 As shown, at each support node, a clamp bracket is designed, consisting of a vibration system base 7, a mass block, and several composite vibration isolation units. Each composite vibration isolation unit comprises a lower pad, a lower end metal rubber component, an annular cavity particle damping layer, an upper end metal rubber component, and an upper pad stacked sequentially along the bolt axis. It is reliably connected to the vibration system base and the mass block via a central high-strength bolt. A clamp or clamping seat for holding external pipelines is provided on the mass block. The overall structure of the anti-vibration-impact combined load aero-engine external pipeline clamp bracket of this invention includes an L-shaped bracket body, the upper part of which is connected by an arc-shaped... The clamp holds the external pipeline, and the upper and lower mounting holes of the bracket are equipped with composite vibration isolation units 9. From top to bottom, the unit consists of a central bolt, an upper gasket, an upper metal rubber component, an annular cavity particle damping layer, a lower metal rubber component, and a lower gasket. The metal rubber (labeled "MRI") and the particle damping layer constitute the core energy dissipation structure. After being tightened by the bolt preload, a nonlinear spring-damping system is formed, which can achieve wide-frequency vibration reduction and strong impact energy dissipation under combined vibration and impact loads. The overall structure can directly replace the traditional rigid clamp without modifying the original pipeline and casing.

[0046] Step 4: Identification of dynamic parameters of the composite vibration isolation unit: Through quasi-static compression tests and shaking table or impact table tests, the force-displacement and force-velocity hysteresis curves of the composite vibration isolation unit under different preload and particle filling rates are measured. The equivalent linear stiffness and the nonlinear damping parameters describing the hysteresis of the metal rubber and the energy dissipation of particle collision-friction are obtained by fitting with the Bouc-Wen model or piecewise linear hysteresis model. The nonlinear damping force Fz of the composite vibration isolation unit is generated by the particle damping and the internal friction of the metal rubber. The particle damping part is characterized by an exponential or piecewise linear velocity function related to the relative velocity amplitude, which can significantly increase the damping force to dissipate the impact energy under large displacement and high acceleration impact.

[0047] Figure 1 This is a schematic diagram showing the physical structure of the composite vibration isolation unit, illustrating its solid structure from top to bottom, consisting of bolts, gaskets, a metal-rubber layer, and an annular cavity particle damping layer. Figure 2The corresponding mass-spring-nonlinear damping equivalent dynamic model is given, where the mass block m corresponds to the mass of the vibration isolation unit, and the spring force... Corresponding to the elastic support of the metal rubber, the nonlinear damping element characterizes the combined energy dissipation effect of the metal rubber and particle damping.

[0048] Step 5, Mass-Spring-Nonlinear Damping Dynamics Modeling: Treat the mass block as a lumped mass. The base of the vibration system is considered as the moving boundary, and the base displacement is... The displacement of the mass block is The composite vibration isolation unit consists of an equivalent linear spring force. and nonlinear damping force The parallel system is characterized by the following differential equations of motion:

[0049]

[0050] in, This represents the concentrated mass of the mass block in the composite vibration isolation unit, simplifying the mass block into a point mass with mass. This represents the absolute acceleration of the mass block, i.e. The second derivative with respect to time describes the acceleration of the mass. The absolute displacement of the mass block (which varies with time) is represented with reference to a fixed coordinate system. It represents the absolute displacement of the vibration system base (as a function of time), and represents the vibration / impact excitation transmitted from the casing. This represents the equivalent linear spring force, provided by the elastic deformation of the metal-rubber, where... For equivalent linear stiffness, This represents the relative displacement of the mass block relative to the base. This represents the nonlinear damping force, generated by the combined internal friction of the metal-rubber system and the impact friction of the particles, and is a relative displacement. and relative velocity The function; This represents the absolute velocity of the mass block, i.e. The first derivative with respect to time; This represents the absolute velocity of the base of the vibration system, i.e. The first derivative with respect to time; This represents the relative velocity of the mass block with respect to the base.

[0051] The above model is discretized into frequency domain or time domain form for coupling with the external pipeline finite element model;

[0052] Step 6, Structural Equivalence and Finite Element Coupling: In the finite element model of the external pipeline, the support constraints connected to the casing at each clamp support position are replaced with the mass-spring-nonlinear damping element. The casing vibration and impact acceleration are used as base excitations applied to the vibration system base. An overall dynamic model of casing-composite clamp support-external pipeline is established from top to bottom. The contact between the clamp body and the pipeline is characterized by a piecewise linear stiffness model. The stiffness changes with the clamp tightening torque to reflect the bilinear support characteristics of the clamp during loading and unloading.

[0053] Step 7: Vibration-Shock Combined Working Condition Simulation Analysis: Based on the overall dynamic model, time-domain or frequency-domain response calculations are performed on typical engine vibration conditions and superimposed carrier-based aircraft landing impact conditions to obtain the displacement, stress, clamp reaction force, and mass block acceleration response of key pipeline sections; specifically:

[0054] (1) Under steady-state engine conditions, frequency response analysis was performed on the narrow-band or broadband random vibration of the base to obtain the modal characteristics and vibration response of the pipe-clamp system in the range of 0–1500 Hz; such as Figure 4 As shown in the comparison curves of the frequency response characteristics of the composite vibration isolation clamp scheme of the present invention and the traditional rigid clamp scheme, it can be seen that the modal frequencies of the present invention are moderately shifted, the resonance peak is lower, the bandwidth is wider, and the damping energy dissipation capacity is stronger, which can effectively reduce the resonance response and avoid the main excitation frequency range of the engine.

[0055] (2) The landing impact time history was superimposed on the engine vibration, and the transient response analysis of the overall model was carried out to evaluate the weakening effect of the composite clamp bracket on the pipeline impact response.

[0056] Coupled modes and key response modes are identified through modal strain energy analysis.

[0057] Step 8, Parameter Optimization and Design Evaluation: Using the peak stress of the pipeline, peak acceleration, clamp connection reaction force, and vibration isolation efficiency as indicators, multi-objective optimization is carried out by changing design variables such as metal rubber density, particle material and particle size, particle filling rate, bolt preload, number and arrangement of composite vibration isolation units, to obtain a clamp support design scheme that meets the requirements of vibration-impact combined load.

[0058] The design evaluation indicators include at least:

[0059] (1) Under the impact condition of landing, the equivalent stress of any section of the external pipeline shall not exceed the predetermined safety factor of the material yield strength;

[0060] (2) The maximum reaction force at the connection between the clamp and the casing is lower than the bearing limit of the casing connection structure;

[0061] (3) The mass of the composite clamp bracket shall not exceed the predetermined upper limit of the mass of the original rigid bracket;

[0062] (4) Compared with the benchmark scheme that does not use composite vibration isolation unit, the peak acceleration or peak stress of the key nodes of the pipeline is reduced by no less than a predetermined proportion.

[0063] An external piping clamp bracket for aero-engines used to resist combined vibration and shock loads, comprising:

[0064] 1) The vibration system base is a metal disc or plate structure that is fixedly connected to the aircraft engine casing, with bolt holes for installing composite vibration isolation units provided on its outer edge or at specific locations;

[0065] 2) Mass blocks, arranged above the base of the vibration system, are cylindrical or frustum-shaped, with mounting surfaces on their top or sides for fixing external pipe clamps;

[0066] 3) Several composite vibration isolation units are symmetrically arranged along the circumferential or rectangular arrangement between the base of the vibration system and the mass block. Each composite vibration isolation unit consists of a lower pad, a lower metal rubber component, an annular cavity particle damping layer, an upper metal rubber component, and an upper pad arranged sequentially from bottom to top, and is clamped together as a whole by a central bolt.

[0067] 4) The center bolt is a high-strength bolt. Its lower end is connected to the base of the vibration system, and its upper end is connected to the mass block. It is used to press the metal rubber parts and the annular cavity particle damping layer under the action of a predetermined preload to form a multi-point supported nonlinear spring-damping system.

[0068] The annular cavity particle damping layer is a closed metal annular cavity filled with at least one of steel shot, ceramic particles or metal powder, with a particle filling rate of 30% to 80%. Under impact load, the particles collide and rub violently with each other and with the cavity wall to dissipate impact energy and achieve impact protection for external pipelines.

[0069] The clamp bracket is installed between the external pipes and the casing of the aircraft engine of a carrier-based aircraft or an aircraft with similar landing impact conditions, and is used in impact environments such as arrested landing, catapult takeoff or large deck turbulence of carrier-based aircraft.

[0070] like Figure 1As shown, each composite vibration isolation unit of the present invention comprises, from bottom to top, a lower gasket 1, a lower metal rubber component 2, an annular cavity particle damping layer 3, an upper metal rubber component 4, and an upper gasket 5. The lower metal rubber component 2 and the upper metal rubber component 4 are formed by winding, sintering, and pressing metal wires, exhibiting significant nonlinear elasticity and hysteretic damping characteristics. The annular cavity particle damping layer 3 is a closed metal annular cavity filled with steel shot or ceramic particles, with the filling rate selected between 30% and 80% according to design requirements. The lower gasket 1 and the upper gasket 5 are high-strength metal gaskets used to uniformly transmit axial loads and protect the metal rubber and particle cavity.

[0071] The central bolt 6 passes sequentially through the upper gasket 5, the upper metal rubber component 4, the annular cavity particle damping layer 3, the lower metal rubber component 2, and the lower gasket 1, and is locked in place by a nut on the lower surface of the vibration system base 1. By adjusting the preload of the bolt 6, the lower metal rubber component 2 and the upper metal rubber component 4 are brought into a certain state of compression, while the particles in the annular cavity particle damping layer 3 receive appropriate initial contact pressure.

[0072] Under normal vibration conditions, the vibration of the engine's external pipeline is transmitted to the lower metal rubber component 2 and the upper metal rubber component 4 of the composite vibration isolation unit. The elastic deformation and friction between the metal wires provide the main support stiffness and hysteretic damping. Under strong impact conditions such as carrier-based aircraft landing, the engine's external pipeline generates a large relative displacement and velocity. The particles in the annular cavity particle damping layer 3 undergo violent collisions and sliding friction, forming strong nonlinear energy dissipation, rapidly attenuating the impact energy, and reducing the impact load transmitted to the casing.

[0073] In this embodiment, the composite vibration isolation clamp bracket of the present invention is arranged at the connection position between the external fuel line and the casing of the carrier-based aircraft engine. The measured time history of the vertical acceleration of the casing under the arrested landing condition of the carrier-based aircraft is selected as the impact input. The simulation results of the traditional rigid clamp bracket and the composite vibration isolation clamp bracket of the present invention under this condition are compared (Table 1 and Table 2):

[0074] Table 1. Modal analysis simulation results

[0075]

[0076] The modal analysis simulation results in Table 1 show that, compared with the baseline scheme of traditional rigid clamps, the pipeline system using the composite vibration isolation clamp support of this invention exhibits a slight decreasing trend in the first six modal frequencies, with a reduction of 3% to 5%. This trend indicates that while introducing composite vibration isolation units and additional mass blocks, this invention does not significantly weaken the overall structural stiffness of the pipeline system. Furthermore, the moderate shift in modal frequencies effectively avoids the main excitation frequency range under aero-engine operating conditions, reducing the risk of resonance in the pipeline system and ensuring the structural stability of the pipeline under broadband vibration environments.

[0077] Table 2 Comparison of Maximum Equivalent Stress in Pipelines under Random Vibration Conditions

[0078]

[0079] The stress comparison results under random vibration conditions in Table 2 show that the maximum equivalent stress of the pipeline in this invention is reduced from 86 MPa in the benchmark scheme to 47 MPa, representing a stress reduction of 45.3%. This data fully verifies the vibration reduction and energy dissipation effect of the composite vibration isolation unit of this invention, which can effectively attenuate the transmission of vibration energy, significantly reduce the stress level of key parts of the pipeline, avoid fatigue damage caused by long-term high-stress vibration, and greatly improve the vibration resistance reliability of external pipelines of aero-engines.

[0080] Experiments show that after introducing the composite vibration isolation clamp bracket, the natural frequencies of each order are slightly reduced but not significantly changed, indicating that the structure of the present invention, while introducing additional mass and vibration isolation units, does not significantly reduce the overall stiffness of the piping system and can still meet the requirement of being offset from the main excitation frequency of the engine. After adopting the structure of the present invention, the peak equivalent stress at the key bend of the external piping is significantly reduced, and the safety margin is significantly improved. The vibration attenuation at the piping and clamp is faster, and the vibration attenuation time after impact is shortened, which is beneficial to reducing the fatigue damage of subsequent vibrations to accessories and connectors. The equivalent reaction force at the casing connection hole is reduced, which helps to prevent fatigue cracks in the casing structure under repeated ship landing impacts.

[0081] This invention addresses the external piping of aero-engines supported by multiple clamps. It introduces a composite vibration isolation unit composed of metal rubber and annular cavity particle damping at the traditional clamp-to-casing connection point. Through a parallel support structure of mass block-metal rubber-particle damping, it achieves integrated vibration control and impact protection design. The method first establishes a finite element model based on the spatial arrangement of the external piping and the constraints of the multiple clamps, obtaining the time histories of typical engine vibration loads and large-amplitude impact accelerations similar to those experienced during carrier-based aircraft landings. Then, through experimental or empirical models, the equivalent stiffness and nonlinear particle damping parameters of the composite vibration isolation unit are identified, establishing a mass-spring-nonlinear damping dynamic model. Based on this, the composite vibration isolation unit is equivalent to a nonlinear spring-damping element coupled into the piping-clamp-casing finite element model, conducting response analysis and parameter optimization design under combined vibration and impact conditions. This structure primarily relies on the energy dissipation through collisions and friction between particles and the cavity wall, as well as among the particles themselves, within the annular cavity under impact conditions to mitigate the impact. Combined with the hysteretic damping of the metal rubber, this significantly reduces the peak acceleration and bending stress of the external piping. It is particularly suitable for external piping systems of aero-engines operating in high-impact environments such as carrier landings, hard landings, and runway turbulence. The method of this invention enables the structural design, nonlinear dynamic modeling, and simulation optimization of the external piping clamp support within a unified framework, improving the accuracy and engineering efficiency of vibration and impact resistance design.

[0082] The above embodiments are merely preferred embodiments of the present invention and should not be considered as limiting the scope of the present invention. All equivalent variations and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A design and simulation method for external pipeline clamp supports of aero-engines used to resist combined vibration and shock loads, characterized in that, include: Step 1: Introduce a composite vibration isolation unit consisting of metal rubber and annular cavity particle damping between the aero-engine casing and the external pipeline clamps. Through the multi-point supported mass block-metal rubber-particle damping structure, broadband vibration control and strong impact energy dissipation are achieved. Step 2: Based on the experiment, establish a mass-spring-nonlinear damping dynamic model of the composite vibration isolation unit, focusing on characterizing the collision energy dissipation characteristics of the annular cavity particles under impact conditions; Step 3: Equivalent the composite vibration isolation unit to a nonlinear spring-damping support and couple it to the finite element model of the multi-clamp external pipeline to construct an overall dynamic model of the casing-composite clamp support-external pipeline for the combined vibration-shock working condition; Step 4: Using a combination of vibration frequency response analysis and shock transient analysis, a joint simulation was conducted on typical engine vibration conditions and superimposed carrier-based aircraft landing impact conditions to evaluate pipeline stress, displacement and acceleration response. Step 5: Through multi-objective optimization design, the pre-compression amount of metal rubber, particle filling rate and material, and the number and position parameters of vibration isolation units are optimized to obtain a clamp bracket design scheme with good vibration isolation effect under vibration conditions, strong impact attenuation capability under impact conditions, and meeting mass and volume constraints.

2. The design and simulation method for external pipeline clamp brackets of aero-engines for resisting combined vibration and shock loads as described in claim 1, characterized in that, In step 1, the external pipeline is a U-shaped, Z-shaped or L-shaped bend structure supported by multiple clamps, and the pipeline is connected to the aero-engine casing through three or more clamps; the finite element model uses Timoshenko beam elements to uniformly model the straight pipe section and the bend section, and discretizes the clamp width effect into multi-point spring-damped supports arranged along the pipe axis.

3. The design and simulation method for external pipeline clamp supports of aero-engines for resisting combined vibration and shock loads as described in claim 1, characterized in that, In step 2, the tests include quasi-static compression tests, shaking table tests, and impact table tests, used to obtain the force-displacement and force-velocity hysteresis curves of the composite vibration isolation unit under different preload and particle filling rates. The nonlinear damping force Fz of the composite vibration isolation unit is generated by the particle damping and the internal friction of the metal-rubber. The particle damping part is characterized by an exponential or piecewise linear velocity function related to the relative velocity amplitude. The mass block is regarded as a concentrated mass m, and the vibration system base is regarded as the moving boundary. The base displacement is... The displacement of the mass block is The composite vibration isolation unit consists of an equivalent linear spring force. and nonlinear damping force The parallel system is characterized by the following differential equations of motion: The above model is discretized into frequency domain or time domain form for coupling with the external pipeline finite element model.

4. The design and simulation method for external pipeline clamp brackets of aero-engines for resisting combined vibration and shock loads as described in claim 1, characterized in that, In step 3, the contact between the clamp body and the pipeline is characterized by a piecewise linear stiffness model. The stiffness changes with the clamp tightening torque to reflect the bilinear support characteristics of the clamp during loading and unloading. At the same time, the requirements for the combined load input are clarified. The impact acceleration time history is the measured vertical acceleration time history at the casing or casing mounting frame when the carrier-based aircraft lands, or an equivalent half-sine pulse, trapezoidal pulse, or its superimposed waveform constructed according to the carrier-based aircraft landing impact test standard. Combining the impact load and the engine vibration load, an integrated dynamic model of casing-composite clamp bracket-external pipeline is built from top to bottom to realize the coupling of structure and load.

5. The design and simulation method for external pipeline clamp brackets of aero-engines for resisting combined vibration and shock loads as described in claim 1, characterized in that, In step 4, a combination of vibration frequency response analysis and shock transient analysis is used to conduct joint simulation of typical engine vibration conditions and superimposed carrier-based aircraft landing impact conditions to evaluate pipeline stress, displacement and acceleration response.

6. The design and simulation method for external pipeline clamp supports of aero-engines for resisting combined vibration and shock loads as described in claim 1, characterized in that, In step 4, simulation calculations are carried out in stages: first, vibration-shock combined working condition response analysis is performed, including: (1) under the steady-state working condition of the engine, frequency response analysis is performed on the narrow-band or broadband random vibration of the base to obtain the modal characteristics and vibration response of the pipeline-clamp system in the range of 0 to 1500 Hz; (2) on the basis of engine vibration, the landing impact time history is superimposed to perform transient response analysis on the overall model to evaluate the weakening effect of the composite clamp bracket on the pipeline impact response; then, the coupled modes and key response modes are identified by modal strain energy analysis. First, frequency response analysis is performed on the steady-state vibration working condition of the engine to obtain the modal characteristics of the pipeline system and verify whether it avoids the main excitation frequency; then, the carrier-based aircraft landing impact time history is superimposed to perform transient response analysis to calculate the stress, displacement peak and mass block acceleration response of the key section of the pipeline and comprehensively evaluate the vibration reduction and impact resistance effect of the composite clamp bracket.

7. The design and simulation method for external pipeline clamp brackets of aero-engines for resisting combined vibration and shock loads as described in claim 1, characterized in that, In step 5, the optimization objectives and constraints are first clarified, including: peak pipeline stress, clamp connection reaction force, and support mass; the design evaluation indicators of the design scheme should at least include: (1) Under the impact condition of landing, the equivalent stress of any section of the external pipeline shall not exceed the predetermined safety factor of the material yield strength; (2) The maximum reaction force at the connection between the clamp and the casing is lower than the bearing limit of the casing connection structure; (3) The mass of the composite clamp bracket shall not exceed the predetermined upper limit of the mass of the original rigid bracket; (4) Compared with the benchmark scheme that does not use composite vibration isolation unit, the peak acceleration or peak stress of the key nodes of the pipeline is reduced by no less than a predetermined proportion.

8. A clamp bracket for external piping of an aero-engine used to resist combined vibration and shock loads, characterized in that, include: The vibration system base is a metal disc or plate structure that is fixedly connected to the aircraft engine casing, with bolt holes for mounting composite vibration isolation units provided on its outer edge or at specific locations; The mass block, arranged above the base of the vibration system, is cylindrical or frustum-shaped, with mounting surfaces on its top or side for fixing external pipe clamps. Several composite vibration isolation units are symmetrically arranged in a circumferential or rectangular arrangement between the base of the vibration system and the mass block. Each composite vibration isolation unit consists of a lower pad, a lower metal rubber component, an annular cavity particle damping layer, an upper metal rubber component, and an upper pad arranged sequentially from bottom to top, and is clamped together as a whole by a central bolt. The center bolt is a high-strength bolt. Its lower end is connected to the base of the vibration system, and its upper end is connected to the mass block. It is used to press the metal rubber parts and the annular cavity particle damping layer under the action of a predetermined preload to form a multi-point supported nonlinear spring-damping system.

9. A clamp bracket for external pipelines of an aero-engine for resisting combined vibration and shock loads as described in claim 8, characterized in that, The annular cavity particle damping layer is a closed metal annular cavity filled with at least one of steel shot, ceramic particles or metal powder, with a particle filling rate of 30% to 80%. Under impact load, the particles collide and rub violently with each other and with the cavity wall to dissipate impact energy and achieve impact protection for external pipelines.

10. A clamp bracket for external pipelines of an aero-engine for resisting combined vibration and shock loads according to claim 9, characterized in that, The clamp bracket is installed between the external pipes and the casing of the aircraft engine of a carrier-based aircraft or an aircraft with similar landing impact conditions, and is used in impact environments such as arrested landing, catapult takeoff, or large deck turbulence of carrier-based aircraft.

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