√area法を用いたアルミダイカスト合金の疲労限度予測

Abstract

In order to evaluate quantitatively the effects of casting defects on the fatigue properties of aluminum die-casting alloy, a fatigue limit estimation for aluminum die-casting alloy (JIS ADC12) containing large casting defects was proposed by means of √area method. Fatigue tests were performed in ambient air by means of a dual spindle type rotating bending fatigue testing machine for two types of the specimen; one is an hourglass type specimen and the other is a smooth specimen having four artificial drilled holes whose √area were ranged from 300 to 2000 μm on the surface. After fatigue tests, fracture surfaces and artificial defects were observed using an optical microscope and a scanning electron microscope (SEM). As results, all hourglass type specimens failed from casting defects. In the case of the smooth specimen having four artificial drilled holes, fatigue limit tended to decrease as artificial defects became large. According to the fatigue limits of the hourglass type specimen and of the straight type specimens having four artificial drilled holes, fatigue limit estimation for aluminum die-casting alloy was proposed by means of modified √area method. In addition, it was clarified that the proposed equations for JIS ADC12 could estimate fatigue limits of another type aluminum die-casting alloys, JIS ADC10-T6.