Bi-axial Strain Accumulations in Mechanical Ratcheting

Abstract

Bi-axial strain accumulations in both axial and circumferential directions are observed in the mechanical ratcheting tests conducted by subjecting thin-walled tubular specimens to combined steady internal pressure and cyclic axial loading. The direction and magnitude of ratcheting strain are examined, as functions of maximum stress, stress ratio, steady stress and number of cycles. The strain accumulated in the direction of steady stress increases with an increasing steady stress. The direction of ratcheting strain accumulation is independent of the maximum stress value and number of cycles. At a given maximum effective stress, a stress ratio and a number of cycles, the magnitude of strain accumulated in a bi-axial stress condition is nearly equal to the ratcheting strain in a uni-axial stress condition.