Abstract: An allocation method which considers fault correlation is proposed for the reliability allocation of series systems based on the non-linear transform functions of failure mode and effects analysis (FMEA). In consideration of the multiple factors that affect the reliability allocation, an reliability allocation matrix is established by employing the significance factors. The non-linear transform laws of failure severity and failure frequency are established to address the limitation of FMEA. A coefficient matrix of fault correlation is established based on Gumbel Copula function and Kendall correlation coefficients, and the correlated failure severities of subsystems are calculated. The equation of calculating the reliability of series system is derived based on Copula function. This equation is employed to guide the reliability allocation. Finally, the characteristics of the method are analyzed by taking a spindle system of a computerized numerical controlled (CNC) lathe for example. The allocation results are compared, which consideres dependent and independentfaults of subsystems. The result shows that the the allocation method with fault correlation can be used to provide the lower reliability allocation of subsystems, thus reducing the processing and maintenance costs.

Key words: machine tool technology, series system, reliability, failure mode and effects analysis, comprehensive reliability allocation, failure correlation