Bidirectional algorithm of structural topology optimization

The evolutionary structural optimization (ESO) method has been under continuous development since 1992. The topology and shape of structures are conservative for safety reasons and therefore contain an excess of material which should be removed. The ESO algorithm caters for topology optimization by allowing the removal of material from all parts of the design space. With appropriate chequer-board control and controls on the number of cavities, the method can reproduce traditional fully stressed topologies, and has been applied for the problems with static stress, stiffness, displacement etc. If the algorithm is restricted to the removal of surface-only material, then a shape optimization problem is solved. A bidirectional evolutionary structural optimization (BESO) method is presented whereby material can be added to and removed off. But there are much more oscillation states in optimizing iteration processes of this method, it leads to long calculation time for an optimum solution. Based on stress and the evolutionary structural optimization method, a procedure for an improved bidirectional structural topology optimization is given. It is the development and modification of the conventional ESO method and BESO method. Two examples demonstrate that the proposed method can deal with the solution oscillatory phenomenon, and obtain more optimal structural topology.