An investigation of residual stresses in simulated wing panels of 7075-T6 aluminum.

Abstract

The advent of onboard aircraft microprocessor fatigue monitoring systems will establish the opportunity to fully exploit residual stresses at stress-critical areas, including their effects on fatigue predictions. An experimental investigation was undertaken to more fully understand them by making photoelastic measurements of residual stresses at notches in simulated wing panels of 7075-T6 aluminum and to establish the relationships between the local stresses, residual stresses, and the far-field or applied stress. The stress concentration factors were found to decrease with increased plastic deformation while the strain concentration factors were found to remain constant. The residual stress levels were found to be immutable despite changes in fatigue loading conditions, notch geometry, or test duration.