A method for calculating the dynamic characteristics of an aircraft impacting an arresting net

Abstract

The present application belongs to the field of overall aircraft design, and specifically relates to a method and device for calculating the dynamic characteristics of an aircraft impacting an arresting net. The method comprises step S1, constructing a full aircraft model including a pilot model, a landing gear model and a parachute model; step S2, constructing an arresting net model and an arresting system model, and assembling them into an arresting model, wherein the arresting net model simulates the net axis position through a one-dimensional unit that is only used to withstand tension, and simulates the net outer surface position through a two-dimensional unit that is only used to withstand shear, bending moment and torque; step S3, performing an aircraft impacting net simulation based on the full aircraft model and the arresting model; step S4, determining the movement process of the aircraft and the arresting net during the impacting net process and obtaining the load history of the set components. The present application can accurately establish detailed models of the aircraft and the arresting net, has high computational efficiency in dealing with nonlinear contact problems, and can be effectively applied to model design to solve the simulation of the dynamic characteristics of aircraft impacting nets.

Description

Technical Field

[0001] The present application belongs to the field of overall aircraft design, and specifically relates to a method for calculating the dynamic characteristics of an aircraft impacting an arresting net. Background Art

[0002] Affected by the length of the landing or carrier runway, the aircraft needs to stop at a shorter distance. In the event of a hook failure, the carrier-based aircraft needs to pull up the arresting net for emergency arrest. When an Air Force aircraft needs to make an emergency landing at a mountainous or island airport due to special circumstances such as the failure of the parachute to open, it needs to be arrested by the arresting net to avoid running off the runway.

[0003] In order to analyze the damage to the aircraft structure and the impact on pilot safety caused by the high-speed impact of an aircraft against an arresting net, it is necessary to carry out dynamic simulation analysis of the aircraft impacting the net and study the dynamic engagement of two highly nonlinear systems, including the aircraft and the arresting net. This involves large displacement and large deformation impact responses. It is necessary to establish a dynamic analysis method for the transient impact of an aircraft against an arresting net, as well as a high-fidelity nonlinear dynamic model of the aircraft and the arresting net.

[0004] The existing technologies used in the simulation of aircraft hitting the net include theoretical formula deduction and numerical simulation. Although the traditional theoretical formula can quickly give the maximum speed limit of the aircraft hitting the net, it fails to take into account the detailed factors, cannot give the damage location, and cannot judge the degree of damage caused by different types of aircraft shapes under various impact speeds, weights and postures, such as the nonlinear contact problem between the leading edge of the wing, landing gear, radome and the arresting net rope during the impact. However, the transient impact analysis functions provided by commercial software such as rigid body dynamics and finite element are limited, and cannot simulate the contact characteristics of flexible bodies such as ropes such as arresting nets and the body structure, as well as the refined movement of pilots after being impacted. Summary of the invention

[0005] In order to solve the above problems, the present application provides a method for calculating the dynamic characteristics of an aircraft impacting an arresting net. Based on rigid body dynamics and finite element contact nonlinear analysis methods, a special unit is developed to construct an arresting net device. Under the premise of ensuring calculation efficiency, the nonlinear contact between the airframe structure and the arresting net can be simulated, and a complete set of aircraft and arresting net system dynamics models can be established to analyze the damage to the airframe structure and the safety of the pilot, realize the dynamic characteristics analysis of the aircraft and the arresting net, and provide the safety limit of the impact speed and the impact weak area.

[0006] The present application provides a method for calculating the dynamic characteristics of an aircraft impacting an arresting net, which mainly includes:

[0007] Step S1, constructing a full aircraft model including a pilot model, a landing gear model and a parachute model;

[0008] Step S2, constructing a barrier net model and a barrier system model, and assembling them into a barrier model, wherein the barrier net material of the barrier net model adopts a nonlinear material constitutive model, and the position of the net axis is simulated by a one-dimensional unit that is only used to bear tension, and the position of the outer surface of the net is simulated by a two-dimensional unit that is only used to bear shear, bending moment and torque. The contact force is calculated by judging the penetration data of the nodes of the contact object and the two-dimensional unit on the surface of the barrier net, and then the node force of the one-dimensional unit is obtained by vector superposition of the force;

[0009] Step S3, performing an aircraft net punching simulation based on the full aircraft model and the arresting model;

[0010] Step S4: determining the movement process of the aircraft and the arresting net during the net punching process and obtaining the load history of the set components.

[0011] Preferably, step S1 further comprises:

[0012] An explicit finite element method is used to establish a finite element model including an airframe structure. The finite element model of the airframe structure includes at least three-dimensional solid models of the aircraft radome, wing leading edge, and canopy. At the same time, kinematic pairs are established between equipment models with assembly relationships to simulate motion constraint relationships.

[0013] Preferably, step S1 further comprises:

[0014] The rigid-flexible coupling method is used to establish the landing gear dynamics model, and the landing gear strut, piston rod, axle, and hub models are given rigid body properties. The buffer model is established using nonlinear spring damping units, and nonlinear contact is established between the piston rod and the landing gear strut. Finally, it is combined with the tire model.

[0015] The tire model is constructed separately, the tire rubber is modeled by solid units and adopts viscoelastic material constitutive model, the cord layer is modeled by membrane units and adopts fabric material constitutive model, the wheel hub is modeled by shell units and endowed with rigid body properties, the airbag is modeled by closed gas and endowed with ideal gas properties, and nonlinear contact is established between the tire and the deck.

[0016] Preferably, after constructing the tire model, the method further includes establishing a tire virtual static pressure experiment and correcting the tire model using experimental data.

[0017] Preferably, step S1 further comprises:

[0018] A drag parachute model is constructed. The parachute rope of the drag parachute is simulated by a one-dimensional rope unit, which bears axial tension. The parachute surface of the drag parachute is simulated by a two-dimensional membrane unit, which bears out-of-plane aerodynamic force. The aerodynamic load is applied to the parachute unit and then transmitted to the structural drag parachute joint to complete the simulation of aircraft deceleration.

[0019] Preferably, step S2 further includes: constructing an arresting system model, the arresting system model includes a hydraulic cylinder model, the flow of the hydraulic cylinder is controlled to control the size of the arresting force, the plunger inside the hydraulic cylinder model is established using a nonlinear spring damping unit, the hydraulic cylinder model and the arresting cable model are combined, contact is established between the models, and the motion constraint relationship between the rigid body and the flexible body is simulated.

[0020] Preferably, step S3 further includes constructing a runway model, assembling the runway model, the arresting system model and the whole aircraft model according to the relative position relationship, and initializing and setting the aircraft speed, weight center of gravity position, pitch angle and roll angle information.

[0021] This application can accurately establish detailed models of aircraft and arresting nets, has high computational efficiency in dealing with nonlinear contact problems, and can be effectively applied in model design to solve the simulation of the dynamic characteristics of aircraft impacting the net. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of a preferred embodiment of a method for calculating the dynamic characteristics of an aircraft impacting an arresting net in the present application.

[0023] Figure 2 Schematic diagram of the barrier net unit. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the implementation of this application will be described in more detail in combination with the drawings in the implementation of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and cannot be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in combination with the drawings.

[0025] This application provides a method for calculating the dynamic characteristics of an aircraft impacting an arresting net. Figure 1 As shown, it mainly includes:

[0026] Step S1, constructing a full aircraft model including a pilot model, a landing gear model and a parachute model;

[0027] Step S2, constructing a barrier net model and a barrier system model, and assembling them into a barrier model, wherein the barrier net material of the barrier net model adopts a nonlinear material constitutive model, and the position of the net axis is simulated by a one-dimensional unit that is only used to bear tension, and the position of the outer surface of the net is simulated by a two-dimensional unit that is only used to bear shear, bending moment and torque. The contact force is calculated by judging the penetration data of the nodes of the contact object and the two-dimensional unit on the surface of the barrier net, and then the node force of the one-dimensional unit is obtained by vector superposition of the force;

[0028] Step S3, performing an aircraft net punching simulation based on the full aircraft model and the arresting model;

[0029] Step S4: determining the movement process of the aircraft and the arresting net during the net punching process and obtaining the load history of the set components.

[0030] This application first needs to build a full machine model, including:

[0031] The first step is to build the detailed model of the aircraft:

[0032] The explicit finite element method is used to establish a finite element model including the fuselage structure. The fuselage structure needs to establish a three-dimensional solid model including the aircraft radome, wing leading edge, cockpit cover, etc. and a two-dimensional model of other key aircraft components. At the same time, kinematic pairs are established between equipment models with assembly relationships to simulate motion constraint relationships.

[0033] The second step is to establish the landing gear model:

[0034] The landing gear not only bears the load from the ground and the brake system during the taxiing process of the aircraft, but is also a key component for the aircraft to impact the arresting net. The landing gear includes tires, landing gear struts, piston rods, axles, hubs and other structures. The tire is one of the main buffer devices of the aircraft. In order to accurately simulate the characteristics of the tire, the internal structure of the tire needs to be established in sequence. The tire rubber is modeled by solid units and the viscoelastic material constitutive model is adopted; the cord layer is modeled by membrane units and the fabric material constitutive model is adopted; the hub is modeled by shell units and given rigid body properties; the airbag is modeled by closed gas and given ideal gas properties; nonlinear contact is established between the tire and the deck; finally, a virtual static pressure experiment of the tire is established, and the tire model is compared with the experimental data and corrected; the rigid-flexible coupling method is used to establish the landing gear dynamics model, and the landing gear struts, piston rods, axles, and hub models are given rigid body properties. The buffer model is established by nonlinear spring damping units, and nonlinear contact is established between the piston rod and the landing gear struts, and finally it is combined with the tire model.

[0035] The third step is to establish the drag parachute model:

[0036] As a key component for aircraft deceleration, the drag parachute is often used during the landing process of land-based aircraft, but not on carrier-based aircraft. The drag parachute model consists of parachute ropes and parachutes. The parachute ropes are simulated by one-dimensional rope units and mainly bear axial tension. The parachute is simulated by two-dimensional membrane units and bears out-of-plane aerodynamic forces. The simulation of aircraft deceleration is completed by applying aerodynamic loads to the parachute unit and then transferring them to the structural drag parachute joint.

[0037] Secondly, this application needs to establish an interception model, including:

[0038] Step 4: Establishment of barrier net model:

[0039] The arresting model includes the arresting system model and the arresting net model. The arresting system model converts the kinetic energy of the aircraft during landing into the thermal energy of the working fluid and the pressure energy in the accumulator through the arresting device to gradually stop the aircraft. The arresting net system and the arresting cable system on the aircraft carrier are interchangeable.

[0040] The arresting net model includes a woven net and a suspension support cable. Under high-speed impact of an aircraft, the arresting net will produce a large deformation, showing flexible characteristics. The arresting net material adopts nonlinear material constitutive characteristics. The arresting net model is established using a unique form of unit. Unlike traditional rope units, which fail to converge due to excessive penetration when simulating contact, the arresting net unit used in this paper can effectively simulate radial nonlinear contact with the aircraft, and can also withstand axial forces. By setting the destruction criterion, the process of the arresting net being broken can be simulated.

[0041] The original special unit form uses one-dimensional + two-dimensional units to simulate the barrier net, such as Figure 2 As shown. The one-dimensional unit is used to simulate the position of the net axis. It can only withstand tension, not pressure, bending moment and torque. The two-dimensional unit is used to simulate the outer surface of the net. It can only withstand shear, bending moment and torque, but does not participate in the transmission of axial tension and pressure. By judging whether the node of the contact object penetrates the two-dimensional unit on the surface of the barrier net and the size of the penetration distance, the contact force is calculated, and then the center one-dimensional rod unit node force is obtained by the vector superposition of the force. This form of unit can effectively simulate the flexible fluctuation characteristics of the barrier net, and can also simulate the pre-tightening state and natural suspension state of the barrier net.

[0042] The hydraulic cylinder model is mainly composed of a cylinder body and a plunger. The size of the arresting force is controlled by controlling the flow of the hydraulic cylinder. The internal plunger is established using a nonlinear spring damping unit. The hydraulic cylinder model and the arresting cable model are combined, and contact is established between the models to simulate the motion constraint relationship between the rigid body and the flexible body.

[0043] After that, you need to build the pilot body model:

[0044] According to aviation standards, a Hybrid III dummy was selected to establish a pilot dummy model and related seat and protection models. The injury hazards to the pilot were evaluated by analyzing the possible collisions between the pilot and the structure, equipment and canopy in the cockpit during the net punching process, as well as the impact overload on the pilot.

[0045] Afterwards, in step S3, an aircraft net-punching simulation analysis is performed: the carrier deck or runway, the arresting net system and the aircraft model are assembled according to the relative position relationship, and the aircraft speed, weight center of gravity position, pitch angle and roll angle and other information are set to perform net-punching analysis.

[0046] Finally, the simulation analysis results are post-processed: the movement process of the aircraft and the arresting net is output, the arresting result of the net is determined, the load history of key components is plotted, and the damage location and degree of damage are given.

[0047] This application can accurately establish detailed models of aircraft and arresting nets, has high computational efficiency in dealing with nonlinear contact problems, and can be effectively applied in model design to solve the simulation of the dynamic characteristics of aircraft impacting the net.

[0048] Although the present application has been described in detail above with general descriptions and specific implementation schemes, it is obvious to those skilled in the art that some modifications or improvements may be made to the present application. Therefore, these modifications or improvements made without departing from the spirit of the present application all fall within the scope of protection claimed in the present application.

Claims

1. A method for calculating the dynamic characteristics of an aircraft impacting an arresting net, characterized in that: include: Step S1, constructing a full aircraft model including a pilot model, a landing gear model and a parachute model; Step S2, constructing a barrier net model and a barrier system model, and assembling them into a barrier model, wherein the barrier net material of the barrier net model adopts a nonlinear material constitutive model, and the position of the net axis is simulated by a one-dimensional unit that is only used to bear tension, and the position of the outer surface of the net is simulated by a two-dimensional unit that is only used to bear shear, bending moment and torque. The contact force is calculated by judging the penetration data of the nodes of the contact object and the two-dimensional unit on the surface of the barrier net, and then the node force of the one-dimensional unit is obtained by vector superposition of the force; Step S3, performing an aircraft net punching simulation based on the full aircraft model and the arresting model; Step S4, determining the movement process of the aircraft and the arresting net during the net punching process and obtaining the load history of the set components; Wherein, step S1 further comprises: An explicit finite element method is used to establish a finite element model including an airframe structure, wherein the finite element model of the airframe structure at least includes a three-dimensional solid model of an aircraft radome, a wing leading edge, and a canopy, and kinematic pairs are established between equipment models having an assembly relationship to simulate a motion constraint relationship; The rigid-flexible coupling method is used to establish the landing gear dynamics model, and the landing gear strut, piston rod, axle, and hub models are given rigid body properties. The buffer model is established using nonlinear spring damping units, and nonlinear contact is established between the piston rod and the landing gear strut. Finally, it is combined with the tire model. The tire model is constructed separately, the tire rubber is modeled by solid units and viscoelastic material constitutive model, the cord layer is modeled by membrane units and fabric material constitutive model, the wheel hub is modeled by shell units and given rigid body properties, the airbag is modeled by closed gas and given ideal gas properties, and nonlinear contact is established between the tire and the deck; A drag parachute model is constructed. The parachute rope of the drag parachute is simulated by a one-dimensional rope unit, which bears axial tension. The parachute surface of the drag parachute is simulated by a two-dimensional membrane unit, which bears out-of-plane aerodynamic force. The aerodynamic load is applied to the parachute unit and then transmitted to the structural drag parachute joint to complete the simulation of aircraft deceleration.

2. The method for calculating the dynamic characteristics of an aircraft impacting an arresting net according to claim 1, characterized in that: After the tire model is constructed, the method further includes establishing a tire virtual static pressure experiment and correcting the tire model through experimental data.

3. The method for calculating the dynamic characteristics of an aircraft impacting an arresting net according to claim 1, characterized in that: Step S2 further includes: constructing an arresting system model, wherein the arresting system model includes a hydraulic cylinder model, and the size of the arresting force is controlled by controlling the flow of the hydraulic cylinder. The plunger inside the hydraulic cylinder model is established using a nonlinear spring damping unit, and the hydraulic cylinder model and the arresting cable model are combined. Contact is established between the models to simulate the motion constraint relationship between the rigid body and the flexible body.

4. The method for calculating the dynamic characteristics of an aircraft impacting an arresting net according to claim 1, characterized in that: Step S3 further includes constructing a runway model, assembling the runway model, the arresting system model and the whole aircraft model according to the relative position relationship, and initializing and setting the aircraft speed, weight center of gravity position, pitch angle and roll angle information.

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