Study On Structural Shape Optimization Under Multi - Load

Structure shape optimization mainly research how to determine the design boundary of the continuous structures, with several boundary and constraint conditions needed, such that most likely to reduce the stress concentration in order to improve the structure bearing capacity or extend the service life of the structures. For the research about the optimization problem under the condition of single load has made a lot progress, such as the optimal criteria under single load condition, various optimization methods et.al. However in fact, due to the change of environment, the deviation of manufacture and assemble, and the friction or wear and tear associated with time, structure or component is often sustained various loadings instead of single load during its service period. The optimal shape based on the single load condition possibly become unfavorable to resist the external various load. Therefore, to carry out the study on structural shape optimization under the multiple loads has important theoretical significance and practical application value.Optimization is a process of beginning from an initial state, then gradually approaching an optimal solution after some iteration; On the contrary, starting from an optimal state instead of an initial state, and then combining many feature information reflected by the optimal state into the optimization algorithm, if we can get them through theoretical analysis or logical reasoning, which undoubtedly has great help to solve the optimization problem. Based on the above idea, this text carried out a detailed research about the optimal shape characteristics, which achieved from the structure shape optimization problem under multiple loads for the purpose of getting the minimum of maximum stress on the design boundary.The classic problem of elastic mechanics——the stress concentration of the infinite plate with a center hole is applied in this task, and in order to improve the efficiency, the whole analysis use the Ansys Parameter Design Language(APDL) with the platform of ANSYS 12.0. At first, the paper gave the theoretical proof for the most optimal characteristic of structural shape under the single load (the stress distribution on the design boundary in the optimal state is uniform) and carried out the verification with the design of shoulder transition curve, and put award the necessary condition for structure shape optimization:the maximum stress on the optimal design boundary obtained from all the effective loads is equal, if also they are independent. Then, we proved the characteristic using reverse logic reasoning method, also raised condition that continuously variable loads with single parameter has the only effective load, at the same time, carried out the simulate analysis for the structure shape optimization under multiple loads, also further verified the optimal shape characteristics mentioned above, results indicate that:①when loading direction or position change continuously within a certain range, there is the only effective load; ②when structure under multiple independent loads, the maximum stresses are equal under in the optimal state. Lastly, for the possibility to reduce the difficulty of this optimal problem by using the optimal shape feature information, we gave the detailed analysis and discussions, from which we found that in some cases the optimal problem under multi-load condition can be converted into the situation of single load.