Experimental investigation for fatigue strength of a cast aluminium alloy

Fatigue strength of a type A319 cast aluminium alloy was studied by means of fully reversible tension-compression tests conducted at room temperature and at 130 °C; the specimens used in this study came from samples cut from the bulkheads of V-8 type engine blocks. Testing was carried out in a servohydraulic machine following staircase schedules. The specimens were tested to fracture or up to 107 cycles. Analyses of the fatigue tests yield to a strength of 99.4 and 90.3 MPa at 107 cycles for the tests at room temperature and at 130 °C. The size and nature of the defects that originated the failure were determined by scanning electron microscopy. It was found that fatigue cracks originated in pores; single cracks were observed to occur in samples tested below a nominal reversible stress of 120 MPa; multiple cracks were observed in samples stressed above this value.