信頼性手法に基づく設計基準決定システムの構築

抄録

A fatigue curve for design in which the reliability is taken into consideration is generally obtained by ASME code. A constant safety factor is used for design in this code though the fatigue life shows some dispersion. Therefore, a design margin decision system based on reliability, which is capable of evaluating fatigue statistically, has been developed in this paper. In the developed system, the following assumptions are used: (i) the distribution of fatigue strength follows one of the normal, log-normal and Weibull, (ii) the distribution of fatigue life follows either log-normal or Weibull, and (iii) η_D, the coefficient of variance for cumulative cycle ratio, coincides with η_N, the coefficient of variance for fatigue life. By using the developed system, a design fatigue curve for a given failure probability and confidence level was obtained and compared with that of ASME code. As a result, it has been clarified that design margin can be calculated statistically for various materials with different dispersion of fatigue life by the developed system.