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Numerical simulation of high-speed collision process of aircraft arresting system

Abstract: in view of the current lack of effective design methods for aircraft arresting system, the interception process of aircraft arresting system under high-speed collision is numerically simulated by using dynamic finite element method. This method simulates the whole interception process more truly, and the calculation results and experimental tests 5 Automatic Zui optimization of graphic curve scale auto scale data is consistent, which can realize the strength and structure design of the body; It can evaluate the damage of the aircraft; At the same time, the control law of the brake can be verified, and then the control law can be improved. This method can be used in the practical design of arresting system

Keywords: aircraft arresting system, numerical simulation, finite element, collision

1 overview

aircraft arresting system is an important airport ground facility, which is mainly used for emergency arresting of land-based and ship based aircraft and free flight landing of ship based aircraft. It is an auxiliary measure for aircraft landing control. The arresting system plays a very important role in ensuring the safety of aircraft taking off and landing and reducing ground accidents

Figure 1 composition diagram of land-based arresting system

the land-based arresting system is mainly composed of the following main parts (Figure 1 shows the composition and working diagram of the arresting system):1) body, which is generally made of nylon composite material and is the capture part of the whole arresting system; 2) The brake is the key part of the arresting system. It is required that the aircraft with different mass and collision speed should be stopped within a limited distance, and the overload condition can meet the requirements, so appropriate control law design should be adopted. At present, the main energy consumption methods are friction and water turbine. 3) The main function of the vertical mechanism is to realize the vertical and release of the body. 4) Brake band, connecting brake and body, solid 2 Carbon fiber reinforced polymer: nearly all body parts on polar 1 need good tensile strength for force transmission

the design of aircraft arresting system mainly has the following difficulties: 1) the design of brake control law. At present, research in this area has been carried out in China [1]. 2) At present, the strength design of the body structure is mainly based on experience and the static mechanical properties of the body materials, and a large margin design is adopted to ensure the realization of the blocking function. 3) Numerical simulation of arresting collision process. Through numerical simulation of the whole interception process, the control law, body structure and strength design are verified and improved. In the design of control law, the existing literature assumes that the aircraft is a simple mass point, so the kinematics and dynamics equations are established to solve, which is different from the actual aircraft arresting process [1,2]

in view of the above situation, this paper uses the dynamic finite element method and pam-shock software as the solver to simulate the arresting process of arresting more truly. Through the numerical simulation of the collision process between the aircraft and the arresting, we can understand the rationality of the body structure design. At the same time, we can effectively test the feasibility of the control law, and provide an intuitive and effective design method for the strength design of the body structure and the verification of the control law

2 calculation model

2.1 system discretization

discretization modeling of the body part of the arresting system using finite element elements. Generally, the body part is composed of multiple layers of single layers as shown in Figure 2 (a). In finite element modeling, only one layer can be used to simulate, and the volume is discretized by beam element. In this way, with the increase of the number of vertical bands of the volume, the length of the beam element in the transverse (horizontal) direction will be very small. Therefore, when modeling, the number of vertical bands of the whole body can be reduced in an appropriate proportion, and it can be achieved by proportional strengthening of material properties. The discrete model of the body part is shown in Figure 2 (b)

(a) actual single layer (b) discrete model

discrete of the body part in Figure 2

the aircraft is discrete by solid 8-node solid elements. After the solid modeling of an aircraft, the divided finite element lattice is shown in Figure 3. The finite element model of the whole aircraft arresting system is shown in Figure 4 after the discretization of the body part, the aircraft and the brake belt (using beam element), in which the brake belt is local

Figure 3 finite element model of aircraft Figure 4 finite element model of the whole arresting system

2.2 realization of control law

when dynamically simulating the arresting system, how to add the control force of the brake on the brake band is a difficulty in numerical simulation. In the process of the actual aircraft being intercepted (as shown in Figure 5), the brake belts on both sides are continuously lengthened after passing through the guide wheel, and the brake belts are subject to control forces in two oblique directions at the guide wheel. The change law of the force is adjusted according to the control law of the brake. In other words, the control force acts on the moving brake belt through the fixed guide pulley. According to the above loading process and the characteristics of finite element calculation, this calculation adopts the following methods to realize the loading of the control force: 1) convert the control law of the brake (the law of force changing with time F-T) into the law of force changing with the displacement of the brake band (F-S); 2) The brake belt is divided into beam elements with equal spacing, and the control force is applied to the nodes of the beam element. 3) The magnitude of the force exerted on the node will be determined according to the position of the node in the brake belt (i.e. the F-S function relationship) (added in the X and Z directions through the decomposition as shown in Figure 5). Time t at which the force begins to act on each node, duration period Δ t. According to the two curves in Figure 7 (f-s-t relationship). In other words, according to the existing brake control law (f-s-t), it is calculated that only the node that just moves to the guide pulley is loaded, and the duration of load action is very small Δ t. After the next node moves to the pulley, the control force received by the previous node becomes zero

Figure 5 decomposition of control force during interception

Figure 6 Variation Law of brake control force with time (test measurement)

Figure 7 variation curve of brake control force with brake belt displacement and time

2.3 material model

when modeling finite element method, beam element is used for body and brake belt, and its material model is material type 205 material model provided by pam-shock. The material tensile test data of typical body vertical belt is shown in Figure 8, The material data will be obtained after processing according to the tensile test results of the belt

figure 8 typical body material tensile test data

due to the high collision speed, the material data of the aircraft mainly adopts the material data of al-2024, and its strength model is described by Johnson cook model:

in the above formula, a=2.65 kbar, b=4.26 kbar, n=0.34, c=0.015, m=1.0, tmelt=775k. The density of the material is recalculated according to the volume and weight of the aircraft

3 simulation results

an aircraft weighs 1.95 tons and collides with the body at a speed of 63.89m/s. The solution results of the above interception process are shown in Figure 9, in which the cloud diagram shows the force on the body belt. It can be seen that through numerical simulation, the structure and strength of the body can be designed. At the same time, the damage degree of the aircraft can also be evaluated

Figure 9 the stress nephogram of the body part during the interception process shows that it is unnecessary for us to detect the displacement and overload changes of the material structure after the aircraft has been intercepted, as shown in Figure 10 and Figure 11. From Figure 10, it can be seen that the stopping distance of the aircraft is 193.5m, while the stopping distance measured in the test is 196m, which is very close. In addition, the overload change also meets the aircraft interception requirements. It can be seen that the control law can be verified and improved by using the numerical simulation method

Figure 10 the change law of aircraft distance with time in interception Figure 11 the change law of aircraft overload (acceleration) with time

4 conclusion

the interception process of the interception system is numerically simulated by using the dynamic finite element method. This method can be used to design the structure and strength of the aircraft arresting, verify and improve the control law of the brake, and evaluate the damage of the aircraft, which can be used to design the aircraft arresting system

thank you very much for the support of Si Group China for the work of this article

references

[1] Wu Juan, Yuan Chaohui, modeling analysis and Simulation Implementation of an aircraft arresting system, Journal of Air Force University of Engineering (NATURAL SCIENCE EDITION), vol2, no.6, PP, 2001

[2] Hu Mengquan, Lin Guohua, analysis of arresting dynamics of carrier based aircraft landing, Journal of Air Force Engineering University (NATURAL SCIENCE EDITION), Vol.1, No.5, PP, 2000. (end)

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