Fatigue Life Distributions and Fracture Types of Ti-6Al-4V Alloy
Hiroyuki OGUMA, Takashi NAKAMURA and Toru NOGUCHI
Abstract:The main purpose of this study is to investigate the mechanism of transition from the surface fracture to the interior fracture in Ti-6Al-4V alloy. During the investigation, we paid attention to the relation between the fracture mode and fatigue life distribution. We analyzed fatigue life distribution using a competing risk model, that regards surface fracture and interior fracture as independent fracture modes. As a result, the distribution of the surface fracture shows a tendency similar to that of nonferrous metals, and the interior fracture distribution is similar to that of low and medium carbon steel that shows a saturated failure probability. In this case, the latter (saturated failure probability) was caused by arrest of interior crack propagations. The fatigue life distribution shows a peculiarity when we do not consider fracture modes. However, there is no peculiar aspect when using the competing risk model to analyze fatigue life distribution individually. It shows that the competing risk model, which consists of two fracture modes, describes well the fatigue characteristics of Ti-6Al-4V alloy. Key Words:Fatigue,Fatigue life distribution, fracture mode, Competing risk model,Weibull plot, Surface originating fracture, Interior originating fracture, Ti-6Al-4V