The Influence on the Fatigue Strength of Aluminum Alloy Parts of the Relationship between the Surface Residual Stress State a

Author:  Jaensson, B.
Source:  Conf Proc: ICSP-1, (p.435-444)
Doc ID:  1981037
Year of Publication:  1981
Abstract:  
To be able to make a reasonable assessment of the fatigue strength improvement attainable by shot peening, it is necessary to know how the cyclic stresses should be added to the residual stresses and which failure criterion should be used. The vector-addition method of stress superposition, used by Mattson and Roberts, has been applied in a laboratory test program comprising fatigue testing of A1 alloy 7009 specimens, shot peened under five different levels of preload. The fatigue strength, evaluated at N - 10 exp 7 cycles, was found to satisfy the octahedral shear stress criterion in three cases, normal shot peening and peening under two levels of compressive preload. The corresponding failure mechanism was shear mode crack propagation from an initiation point below the surface. Tensile strain peened specimens failed by normal mode crack propagation inwards from a subsurface initiation point. This behavior implied deviation from the shear stress failure criterion. Descriptors: Aluminum base alloys-- Mechanical properties; Fatigue strength; Shot peening; Residual stress; Stress concentration.