The paper describes the simulation of impact loads applied on plate panels with welding-induced residual stresses and deformation (WSD). Numerical simulations using FEM are carried out to study the influence of weldin...The paper describes the simulation of impact loads applied on plate panels with welding-induced residual stresses and deformation (WSD). Numerical simulations using FEM are carried out to study the influence of welding-induced residual stresses and deformation on the impact strength of plate panels. Welding is simulated using a three dimensional thermal mechanical coupled finite element method. The welding stress and deformation are taken as the initial imperfections in the impact strength analysis and their influence on the behavior of plate panels subjected to impact loadings. The impact loadings from the three directions, the lateral direction and two in-plane directions of the plate panels are studied. Results show a certain reduction in the impact strength due to the existence of welding stress and deformation in the plate panels. It is found that the reduction of impact force is strongly influenced by the welding deformation and the impact directions in the plate panels. This reduction is more significant when the impact force is in the lateral direction.展开更多
A numerical method for the optimum motion of an undulatory swimming plate is presented. The optimum problem is stated as minimizing the power input under the condition of fixed thrust. The problem is singular for the ...A numerical method for the optimum motion of an undulatory swimming plate is presented. The optimum problem is stated as minimizing the power input under the condition of fixed thrust. The problem is singular for the invisible modes, and therefore the commonly used Lagrange multiplier method cannot predict an optimum solution but just a saddle point. To eliminate the singularity, an additional amplitude inequality constraint is added to the problem. A numerical optimization code with a sequential quadratic programming method is used to solve the problem. The method is applied to several cases of the motion of two-dimensional and three-dimensional undulatory plates, and the optimum results are obtained.展开更多
The acoustic behavior of double-walled laminated composite panels consisting of two porous and air gap middle layers is studied within the classical laminated plate theory （CLPT）. Thus, viscous and inertia coupling ...The acoustic behavior of double-walled laminated composite panels consisting of two porous and air gap middle layers is studied within the classical laminated plate theory （CLPT）. Thus, viscous and inertia coupling in a dynamic equation, as well as stress transfer, thermal and elastic coupling of porous material ave based on the Biot theory. In addition, the wave equations are extracted according to the vibration equation of composite layers. The transmission loss （TL） of the structure is then calculated by solving these equations simultaneously. Statistical energy analysis （SEA） is developed to divide the structure into specific subsystems, and power transmission is extracted with balancing power flow equations of the subsystems. Comparison between the present work and the results reported elsewhere shows excellent agreement. The results also indicate that, although favorable enhancement is seen in noise control particularly at high frequencies, the corresponding parameters associated with fluid phase and solid phase of the porous layer are important on TL according to the boundary condition interfaces. Finally, the influence of composite material and stacking sequence on power transmission is discussed.展开更多
An original plastic equivalent model was proposed to solve the problem of excessive FEM simulation time when designing the press bend forming path and optimizing the process parameters of press bend forming of the int...An original plastic equivalent model was proposed to solve the problem of excessive FEM simulation time when designing the press bend forming path and optimizing the process parameters of press bend forming of the integrally stiffened aircraft panels. Based on the in-depth analysis of the mechanics of the bending and springback of the detailed model and the equivalent model of the integral panels,the plastic equivalent model of the virtual material with special initial yield stress and hardening coefficients was constructed. FEM results indicate that the objective of getting the similar contour with the same press bend forming path is achieved with the error less than 6%,and the efficiency of FEM simulation is improved by more than 80%. The plastic equivalent model is valuable and essential for the further research on the press bend forming process of large scale complicated integral panels.展开更多
It is important for the fuel cell integrated movable system to operate voltage and current using safety control technology. In order to work at the convenient condition of the fuel cell system, high performance fuel c...It is important for the fuel cell integrated movable system to operate voltage and current using safety control technology. In order to work at the convenient condition of the fuel cell system, high performance fuel cell stack with replaceable fiber bipolar plate should be arranged with the integrated subsystem and appropriate working process. The parameters which affect the performance of PEMFC consisting of relative humidity, reaction temperature, gas inlet temperature, gas inlet pressure, and hydrogen and air flow rate. This study is to develop the integrated movable system on distributed power generation and backup power application, such as oxidant supply system, fuel supply system, heat management system, water management system, and power conditioning system. It comprises a novel PLC (Programmable Logic Control) system and human-machine interface. The controller is developed to control fuel cell system and record the operation data by using data acquisition system. The controller can be applied to high performance stack and system to obtain the best performance. The easy-taken high capacity hydrogen barrel embedded into steel plate of this movable system and more convenient than other fuel cell system.展开更多
文摘The paper describes the simulation of impact loads applied on plate panels with welding-induced residual stresses and deformation (WSD). Numerical simulations using FEM are carried out to study the influence of welding-induced residual stresses and deformation on the impact strength of plate panels. Welding is simulated using a three dimensional thermal mechanical coupled finite element method. The welding stress and deformation are taken as the initial imperfections in the impact strength analysis and their influence on the behavior of plate panels subjected to impact loadings. The impact loadings from the three directions, the lateral direction and two in-plane directions of the plate panels are studied. Results show a certain reduction in the impact strength due to the existence of welding stress and deformation in the plate panels. It is found that the reduction of impact force is strongly influenced by the welding deformation and the impact directions in the plate panels. This reduction is more significant when the impact force is in the lateral direction.
文摘A numerical method for the optimum motion of an undulatory swimming plate is presented. The optimum problem is stated as minimizing the power input under the condition of fixed thrust. The problem is singular for the invisible modes, and therefore the commonly used Lagrange multiplier method cannot predict an optimum solution but just a saddle point. To eliminate the singularity, an additional amplitude inequality constraint is added to the problem. A numerical optimization code with a sequential quadratic programming method is used to solve the problem. The method is applied to several cases of the motion of two-dimensional and three-dimensional undulatory plates, and the optimum results are obtained.
文摘The acoustic behavior of double-walled laminated composite panels consisting of two porous and air gap middle layers is studied within the classical laminated plate theory （CLPT）. Thus, viscous and inertia coupling in a dynamic equation, as well as stress transfer, thermal and elastic coupling of porous material ave based on the Biot theory. In addition, the wave equations are extracted according to the vibration equation of composite layers. The transmission loss （TL） of the structure is then calculated by solving these equations simultaneously. Statistical energy analysis （SEA） is developed to divide the structure into specific subsystems, and power transmission is extracted with balancing power flow equations of the subsystems. Comparison between the present work and the results reported elsewhere shows excellent agreement. The results also indicate that, although favorable enhancement is seen in noise control particularly at high frequencies, the corresponding parameters associated with fluid phase and solid phase of the porous layer are important on TL according to the boundary condition interfaces. Finally, the influence of composite material and stacking sequence on power transmission is discussed.
基金Project(50675010) supported by the National Natural Science Foundation of China
文摘An original plastic equivalent model was proposed to solve the problem of excessive FEM simulation time when designing the press bend forming path and optimizing the process parameters of press bend forming of the integrally stiffened aircraft panels. Based on the in-depth analysis of the mechanics of the bending and springback of the detailed model and the equivalent model of the integral panels,the plastic equivalent model of the virtual material with special initial yield stress and hardening coefficients was constructed. FEM results indicate that the objective of getting the similar contour with the same press bend forming path is achieved with the error less than 6%,and the efficiency of FEM simulation is improved by more than 80%. The plastic equivalent model is valuable and essential for the further research on the press bend forming process of large scale complicated integral panels.
文摘It is important for the fuel cell integrated movable system to operate voltage and current using safety control technology. In order to work at the convenient condition of the fuel cell system, high performance fuel cell stack with replaceable fiber bipolar plate should be arranged with the integrated subsystem and appropriate working process. The parameters which affect the performance of PEMFC consisting of relative humidity, reaction temperature, gas inlet temperature, gas inlet pressure, and hydrogen and air flow rate. This study is to develop the integrated movable system on distributed power generation and backup power application, such as oxidant supply system, fuel supply system, heat management system, water management system, and power conditioning system. It comprises a novel PLC (Programmable Logic Control) system and human-machine interface. The controller is developed to control fuel cell system and record the operation data by using data acquisition system. The controller can be applied to high performance stack and system to obtain the best performance. The easy-taken high capacity hydrogen barrel embedded into steel plate of this movable system and more convenient than other fuel cell system.
