A flexplate is a mechanical component that couples the crankshaft to the torque converter of a car with automatic transmission. A higher axial stiffness is one of significant requirements for it in order to ensure its performance. In this paper an optimum design of the flexplate disk is described that maximizes the axial stiffness of the flexplate disk with weight and inertial moment constraints. The strategy for optimizing the layout of the disk is to perform topology optimization first then position optimization. The relation is presented which shows the variation of axial stiffness with respect to changes of the number, shape and position of the holes on the flexplate disk. The research shows that the shape of the hole punched on the disk does not affect the axial stiffness greatly. Thus, the manufacturing cost should be considered first in the optimum design of the flexplate disk

The efficiency of the element removal or addition is of significance for evolutionary structural optimization (ESO) process. The key is to find an appropriate rejection criterion (RC) which allows to assess the contribution of each element to the specified behavior（stress, stiffness, displacement, etc.）of the structure, and to subsequently remove elements with least contribution. This paper proposed a varying elements removal ratio (VERR) method which uses a larger ERR (Element Rejection Ratio) value at early iterations where exist a lot of redundant material, and decreases the value of ERR in the optimal process to lessen the number of elements removed at later iterations. Meanwhile, this paper proposed a strategy for element addition based on stress level and the contribution of elements to the structure in order to decide which elements should be added to the model and the sequence of the element addition. With the proposed VERR and the strategy, the optimization procedure of the structure evolves more quickly and smoothly.