Size effects on residual stress and fatigue crack growth in friction stir welded 2195-T8 aluminium – Part I: Experiments

Abstract

Residual stress fields were measured in three different sizes of Compact-Tension (C(T)) and eccentrically loaded single edge notch (ESE(T)) specimens containing transverse or longitudinal welds. The effect of size on residual stress profiles was studied. Fatigue crack growth tests were carried out with cracks growing into or away from the weld line, as well as growing along the weld centre line. Effects of weld residual stresses on fatigue crack growth rates parallel and perpendicular to the friction stir welds were studied. It wan found that compressive residual stresses around the sample notch had significant retarding effects on both crack initiation and crack growth rates for cracks growing towards the weld line.Effects of residual stress on crack growth rates declined with increasing crack length.When cracks grew parallel to the weld line in C(T) samples the crack growth rate was around 20% lower than in parent material.

Fatigue crack propagation for Q345qD bridge steel and its butt welds at low temperatures

“…Compared with the fatigue data at the stress ratio of R = 0.1, the crack propagation rates were generally accelerated at higher stress ratios. The retarded fatigue crack propagation rates in the weld material at a lower stress ratio result from the possible more severe crack closure effect, caused by the welding residual stress around the crack tips in welded C(T) specimens, 20,42,43 than that at a higher stress ratio. The discrepancy in the fatigue crack propagation rate among different stress ratios decreases at −20°C and −60°C, caused by different reduction in the fatigue resistance at low temperatures.…”

Microstructure–property characteristics of a novel non-weld-thinning friction stir welding process of aluminum alloys

“…Thirdly, stress concentration is easily introduced to the sharp weld edge caused by weld thinning. Owing to this, failure tends to occur at the weld edge under fatigue load, resulting in the poor fatigue properties of FSW joints [10][11][12].…”

Aluminum friction stir welds: Review of fatigue parameter data and probabilistic fracture mechanics analysis

“…While the residual stress distribution through the thickness is normally self-equilibrating, most of the fatigue life is spent during near surface small crack growth, so the residual stress at the surface is the most important from the point of view of fatigue behavior. Although Mahoney [80] found compressive stresses, the data obtained in this work show that they can be tensile and compressive [81][82][83][84][85][86][87], as Fig. 9 presents.…”