For the turbine disk probabilistic risk assessment requirement of CCAR 33.70 airworthiness regulation

the applications of response surface method used in definition of failure zone and estimation of crack growth life were studied. A method of variance reduction of sampling and improving sampling efficiency was demonstrated based on the response surface method to allocate the failure sampling zone during Monte Carlo simulation. It was shown that importance sampling method could significantly improve sampling efficiency:samples rate between failure samples and total samples was 94% by importance sampling method

bigger than traditional direct sampling method (only 33%). The importance sampling method can minimize the total number of samples required to achieve a desired analysis accuracy results. In addition

the life approximation function by response surface method was presented to significantly reduce the computation time of crack growth life:computation time for 104 samples was only 2 minutes by using life approximation function

which was much shorter than traditional life model (288 min). The life error analysis showed that the maximum error was only 1.0%

which had good agreement with traditional method of crack growth life. These results can be applied to improve the efficiency of turbine disk probabilistic risk assessment.