Statistical Duplex S-N Characteristics of Bulk Amorphous Alloy in Rotating Bending in Very High Cycle Regime

Abstract

In order to investigate very high cycle fatigue properties of Zr55Al10Ni5Cu30 bulk amorphous alloy, rotating bending fatigue tests were conducted at room temperature by using 5 different series of Zr55Al10Ni5Cu30 alloy. The differences of material processing conditions are manufacturer, product year, material size and minimum diameter of specimen. Although all specimens fractured from surface, duplex S-N characteristics were observed for each series of the material. Time strength distributions at N=104 for short life region and at N=107 for long life region were well approximated by normal distribution. The entire S-N property accepting the normalized stress amplitude by the time strength at N=104 or N=107 has shown more clearly duplex S-N characteristics. In addition, P-S-N properties were also estimated from the standard deviation of time strength distributions at N=104 or N=107. Based on the observation of fracture surface by scanning electron microscope (SEM), it is confirmed that every fracture surface was consisting of typical three regions such as multi-facet region, stable crack growth region and instantaneous fracture region.