Failure investigation and design improvements of Al 7075 piston for hydraulic actuators

Failure analysis was applied to a hydraulic actuator piston made of aluminium alloy 7075 T6 which failed at a relatively low number of cycles. Cracks were seen to nucleate from some defects naturally present in the material, and their propagation lead to component failure before 100,000 cycles. Experimental tests were carried out to characterize the material by means of the cyclic curve and the fatigue threshold ΔKth. The resultant failure analysis showed the problem in terms of crack propagation thus justifying a fracture mechanics approach to the component failure. Finally, some design recommendations were suggested to increase the fatigue life of the component.