Characteristics of Fatigue-activated Creep in an Aluminium–Magnesium Alloy

Abstract

EXPERIMENTS have been conducted on thin-walled tubes of an aluminium–magnesium alloy (3.08 per cent magnesium, 0.3 iron, 0.44 manganese, 0.18 silicon) under conditions of simple shear. Two tubes aligned on a common axis are used for each test, the torque being applied through a disk connected to both tubes. The assembly is mounted in a thermostatically controlled enclosure, and to avoid any possible errors due to inertial effects associated with the dynamic stress component, the torque is applied through a spring system. A simple electrical device is used to maintain a constancy of torque (within 1 part in 5 × 10³) as the disk rotates during creep. The creep curves are recorded continuously by a photoelectric follower and associated recorder (a ‘Graphi-spot’) which traces the movement of a spot of light reflected from a mirror mounted on the shaft of the torque disk.