疲労寿命推定に及ぼす線形破壊力学因子の影響度評価

抄録

The sensitivity study of linear fracture mechanics parameters in the estimation of fatigue life has been carried out in this paper with the aim of improving the estimation accuracy and serving for the rationalization of structural design, maintenance and inspection.
Since the method of probabilistic sensitivity analysis which is known as the first-order-second-moment format seems to be quite difficult to apply in this case due to the lack of appropriate data, this paper describes the alternative method of deterministic sensitivity analysis which is also based on the first order approximation. The degree of importance of each linear fracture mechanics parameter can be easily evaluated by comparing the corresponding values of the partial derivative. This paper presents the evaluation equations for the case where ΔK can be approximated as ΔK=Δσ√πa, and it is shown that for 2<n≤4 and a₂>>a₁ condition, the degree of importance of linear fracture mechanics parameters on fatigue life is in the order of n>Δσ>C≥a₁>a₂, if C and n are evaluated independently. The same conclusions were obtained from two numerical examples for other conditions.
As the result of this analysis, the parameter n turns out to be most influential on fatigue life, so that it is considered quite important to evaluate n as precisely as possible in order to prevent fatigue failure or to rationalize structural design, maintenance and inspection.