Stiffener layout optimization to maximize natural frequencies of a structure: application to HDD cover structure

Beam-type stiffeners have frequently been used for raising natural frequencies of baseline structures. In stiffener layout optimization problems, most of the previous researches considering the position and/or the length of the stiffener as design variables dealt with structures having just simple convex shapes such as a square or a rectangle. The reason was because concave shape structures have difficulties in formulating geometric constraints. Recently, a geometric constraint handling technique, which can define both convex and concave feasible regions and can measure a degree of geometric constraint violation, was proposed by the authors. Based on the proposed technique, a stiffener layout optimization problem to maximize natural frequencies of a hard disk drive (HDD) cover structure was solved. Evolution strategies (ESs) and differential evolution (DE) were utilized as optimization tools. In addition, the constraint-handling technique of EVOSLINOC (EVOlution Strategies for scalar optimization with LInear and NOnlinear Constraints) was utilized to solve constrained optimization problems. From a numerical example, it was verified that the proposed technique can also be applicable to complex real engineering structures.