Reliability Analysis of the Tube Hydroforming Process Using Fuzzy Sets Theory

Tube hydroforming currently enjoys increasingly widespread application in industry, especially in the automotive industries, because of several advantages over traditional methods. Reliability analysis as a probabilistic method to deal with the probability of the failure of the structure or the system has been widely used in industry. A new reliability analysis approach for the tube hydroforming process using the fuzzy sets theory is presented in this paper. The stress of the hydroformed tube is related to several parameters, such as geometry, material properties, and process parameters. In most cases, it is difficult to express in a mathematical formula, and its relative parameters are not random variables, but the uncertain variables that have not only randomness but also fuzziness. In this paper, the finite element method is applied as a numerical experiment tool to find the statistical property of the stress directly by a fuzzy linear regression method. Based on the fuzzy stress-random strength interference model, the fuzzy reliability of the tube hydroforming process can be evaluated. A tube hydroforming process for cross-extrusion is then introduced as an example to illustrate the approach. The result shows that this approach can be extended to a wide range of practical tube hydroforming process.