In design of experiments, analysis and identifying those variables that affect the outputs are of interest. Response surface methodology is a mathematical-statistical method to optimize the experiment outputs. This method tries to find the best response levels by optimizing the design variables called factors. In many engineering applications, robust design has become the most important issues. Robust design is that can be more and more reliable against possible stresses
Considering some outputs related to reliability aspects, response surface methodology can lead towards the mentioned purposes. Since there are few researches related to this topic in the literature, optimization of multiple response surfaces related to reliability characteristics are considered in this study.