Topological Optimal Design Of Vehicle Components

With the competition of domestic commercial vehicle market develop increasingly, the demanding of the more efficiency methods for controlling the performance about the vehicle components became urgently. The layout optimization deals with the selection of the best configuration for the vehicle component structural systems have turned into the newest and the most rapidly fields in vehicle engineering.In the optimal design process of an vehicle component structure, we have to modify the structure and resolve the displacement or generalized eigen problem in order to get the optimal result. There are two important problems are always confronted in the optimal process, the first is the design sensitivity analysis of the vehicle components and the second is the fast reanalysis of modified structure about the vehicle components. Considering a general layout optimization problem, the various reanalysis methods for modified structures could be classified as follows: the topology modification, the shape modification and the parameter modification. Commonly, the shape modification and the parameter modification usually applied in vehicle engineering field until the topological modification had enough progress in theory and engineering application with the promptly increasing of the computer technology. Topological optimization concerning the topological variations of a structure(number and orientation of elements) is difficult because of changes in the structural model. The solutions of topological optimization problems are more difficult because of changes in the structural model. Members and joints are deleted or added during the solution process and the reanalysis model becomes complicated. Developing reanalysis procedures for general topological modifications is particularly important when the number of degrees of freedom (DOFs) is modified and the structural response is significantly changed. It seems that more efforts are still required in order to implement topological modifications in practical structural design. In this paper, the reanalysis problem for the layout topological modification of vehicle component in automotive engineering field have been studied. Integrating with the layoutOptimization of stiffeners for the engine's flywheel housing of the commercial vehicle and the mode analyzing/optimization of the heavy vehicle load bearing system, bring for-ward some optimal resolutions accordingly. The main research work is summarized as follow:In chapter 2, the combined approximations of displacement, stress, and force are introduced. The main objectives in developing the method presented are to preserve the ease of implementation and the efficiency of the common first Taylor series approximations and to improve significantly the quality of results, such that the method can be used in problems with very large changes in the design variables.In chapter3, discussed the method of structural reanalysis for topological modification. The presented method is suitable for all three cases of topological modifications, especially for the condition that the DOFs about the additions of members and joints changed. Firstly, establish the rigid matrix of initial analysis structure, then reanalyzed the transitional rigid matrix of the structure. Continue the decompose solution to get the analysis result with constant rigid matrix that is assembled and decomposed to avoid reanalyzing the whole rigid matrix of the modified structure.In chapter 4, For instance to do the optimal topological modification of the stiffness for the commercial vehicle engine wheel housing, proposed the rapid reanalysis method adapt to modified structure in automotive engineering field. According to cell sensitivity of the strain energy, establish the searching method for deciding optimal locations of the vehicle engine wheel housing stiffness and the optimal process. With the cell sensitivity of the strain energy we can identify the stiffness that ought to delete or not, to get the optimal stiffness layout. Using this method can shorten design period greatly, acquire exact result.In chapter 5, the method for structural modal reanalysis for topological modifications is presented. This method mainly aimed at the most challenging condition for the newly added degrees of freedom (DOFs) are linked to the original DOFs of the modified structure by means of the dynamic reduction so as to obtain the condensed equation. And then, the eigenvectors of newly added DOFs resulting from topological modification can be re-covered. At last, the Rayleigh-Ritz analysis is used to evaluate the eigen values and eigenvectors for the modified structure, avoid the conditional convergence when using iterative perturbation method based on the results of the initial structure. The reanalysis method can deal with mass and rigid matrix directly and applicable in universal FE system.In chapter 6, the dynamic optimal design of Body in white is discussed. A new like method is developed. In this method, the element is recovered according to the element sensitivity. Using the critical methods, the body in white of heavy commercial truck is improved, and the abnormal vibration is avoided. Also, the safety and the comfortable of body in white is improved by optimization with the modified structure is solved using the modal reanalysis method presented in chater5.