Fatigue Crack Growth of Weldments

Abstract

Fatigue crack growth rate experiments were performed on compact tension specimens of base plate and weldments of 5456-H116 aluminum and of base plate and the heat-affected zone (HAZ) of ASTM A710 Grade A steel. Stress ratios for the tests were 0.1 for both materials, with the aluminum weld also being tested at R = 0.5. Crack opening levels were determined for both the weld and the base plate in the aluminum material and for the A710 material in the as-welded and stress-relieved conditions. The fatigue crack growth rates of the welds and HAZ, when the total applied load was used, were significantly less than those of plate for both materials. Using the effective stress intensity, which accounts for crack closure and thus represents the actual stress intensity at the crack tip, results in a shift of the da/dN versus ΔK curves to a faster growth rate. Comparison of the curves shows that the fatigue crack growth rates of the aluminum weld material fall in the same scatter band of data as those for base plate and that, for the A710 material, the HAZ shifts to faster growth rates than the base plate does. This shift of data leads to more accurate estimates on fatigue life, based on the intrinsic properties of the material.

Sensitivity of Combustion Driven Structural Dynamics and Damage to Thermo-Acoustic Instability: Combustion-Acoustics-Vibration

“…It can be remarked that welds are the local discontinuous regions where fatigue cracks can occur. Residual stresses can be generated in weldments due to thermal expansion, plastic deformation, and shrinkage during cooling [58]. Even low-level residual stresses can significantly enhance the cracking behavior in structures [58,59] such as in combustion liners [60].…”

“…Residual stresses can be generated in weldments due to thermal expansion, plastic deformation, and shrinkage during cooling [58]. Even low-level residual stresses can significantly enhance the cracking behavior in structures [58,59] such as in combustion liners [60]. Besides, the welds can alter the structural dynamics due to the local stiff regions and dimensional inhomogeneity of the weld.…”

Fatigue crack growth assessments in welded components including crack closure effects: Experiments and 3-D numerical modeling

“…Early work of Benoit et al [13] on fatigue crack propagation in the heat affected zone (HAZ) for a structural steel weld showed that FCGR in welded materials are lower than the corresponding rates in the base plate material. Link [14] conducted FCGR experiments using compact tension specimens for both the base plate and weldments of a 5456-H116 aluminum alloy and an ASTM A710 Grade A steel with and without post-weld heat treatment (PWHT); these results show a strong influence of welding residual stresses on the measured FCGRs due to the effects of crack closure. Later, Shankar and Wu [15] showed that fatigue crack growth behavior in welded 5083-H321 aluminum alloys is essentially similar to the parent material.…”