Reliability analysis using an enhanced response surface moment method

Moment methods, which are powerful and simple techniques for analyzing the reliability of a system, evaluate the statistical moments of a system response function and use information from the probability distribution in the analysis. The full factorial moment method (FFMM) performs reliability analysis by using a 3ⁿ full factorial design of experiments (DOE) and the Pearson system for random variables. To overcome the inefficiency of FFMM, the response surface moment method (RSMM) has been proposed, which is based on a response surface model (RSM) that is updated by adding cross product terms into the simple quadratic model. In this paper, we propose the enhanced RSMM (RSMM+) that modifies the procedure of selecting a cross product term in the RSMM and adds a process of judging whether the response surface model can be established before performing an additional experiment. We apply the proposed method to several examples and show that it gives better results in efficiency.     

Shape optimization of mobile phone folder module for structural strength

The mobile phone has become thinner even while its functionalities are ever increasing. Therefore, the importance of structural design to prevent structural failure is of increasing importance. To address this situation, a systematic optimization approach for shape design of a mobile phone folder module is utilized in this research. The structural strength and the exactness of the folder module assembly are considered as performance requirement of the optimization problem. Five shape parameters of the folder module assembly are used as design variables. In this research, the finite element method (FEM) is used to acquire the structural strength of the folder module assembly, and the morphing technique is applied to change the shape of the finite element (FE) model. However, manually performing the morphing and FEM for the simulation model is complex and time consuming especially for a model with complicated shape such as the mobile phone. Therefore, shape optimization involving FEM is known to be very difficult task for actual industrial applications. To overcome this deficiency, two types of approaches are applied in this research. First, process integration and design optimization (PIDO) technology is applied to integrate and automate the analysis processes needed for evaluating structural performances. In addition, a metamodel that can substitute for expensive simulation is employed for the optimization process. From this research, an optimum design for the folder module of a mobile phone enhancing the structural strength is acquired. In addition to the optimum solution, a metamodelbased shape optimization procedure which is applicable to practical engineering problem is established.