The Lightweight Design Of Large Complex Structures Based On Equivalent Static Load Method

Mechanical structures are inevitably subjected to various dynamic loads. As the engineering goods and equipments are more and more towards to be higher precise, faster, and more lightweight, dynamic response optimization of products is the urgent demand of engineering. If the direct-dynamic response optimization of structure be submitted, it will be very time-consuming of the sensitivity calculation and be difficult to deal with the dynamic constraints. The equivalent static load method is used to transform the dynamic optimization problem into a static optimization, the lightweight design of the lifting device and sub frame are performed, and then the different results of the same structure under the static optimization method and equivalent static load method are discussed.Firstly, the mathematical model of structure optimization and the algorithm of the mathematical model are introduced. The fundamental theory of the flexible multi-body dynamics analysis and the equivalent static load method are also introduced.Secondly, as the optimization object,three hinge points of the lifting device are parameterized. The optimal solution of the three hinge points is obtained by deriving an analytical expression of objection function and solving the objective function through the program.Thirdly, the dynamic response structural optimization of the lifting device and the sub frame are performed using equivalent static load method to realize the lightweight design of lifting device and sub frame. Under the premise of not reducing the strength and stiffness of the lifting device, the lightweight design is performed using the continuous variable optimization method, the optimized lifting device total weight than that before optimization reduces the rate of15.4%. The lightweight design of sub frame is performed using the discrete variable optimization method. The optimized sub frame total weight than before optimization reduces the rate of6.3%, and the maximum stress reduces rate of16.4%.Finally, taking connecting rod of the vibration sieve as the object of optimization, the static structural optimization and dynamic structural optimization which is based on equivalent static load method are performed. By comparing the results of the optimization, It shows that it is unreasonable if the optimization of high-speed structure be performed just using the simple static structural optimization method.The results from these demonstrations show that applying dynamic response optimization on vehicle structure using equivalent static load method is feasible and can get a better improved structure. It also can reduce the dependency of engineers’ experience and cut off the time of applying optimization.