Analytical and Graphical Aids for the Fatigue Design of Weldments

Abstract

There are four important attributes of weldments which, together with the magnitude of the fluctuating stresses applied, determine their resistance to metallic Fatigue: the ratio of the applied or self-induced axial and bending stresses; the severity of the discontinuity or notch which is an inherent property of the geometry of the joint; the notch-root residual stresses which result from fabrication and subsequent use of the weldment; and the mechanical properties of the notch-root material in which fatigue crack initiation and growth takes place. A simple version of a more elaborate analytical model of the fatigue behavior of weldments [l] is presented here which provides analytical and graphical design aids for design. 223J.-Y YLNC; and F. V. L A W H~. N C~

Fatigue crack initiation and growth in AlMg4.5Mn butt weldments

“…1 along with the measured values of their toe radius ( ρ ) and flank angle ( θ ). Estimated values of the weld‐toe elastic stress concentration factor ( K t ) 2 are also included. All weldments were stress‐relief annealed to reduce welding residual stresses.…”

Physical Modeling of the Entire Fatigue Process

“…The 2c a a predictions for the number of cycles to crack initiation, N i , are based on the Coffin-Manson equation with Morrow's mean stress correction (Refs [4] and [5]): In the present chapter we will show in more detail how the method is applied for a weld notch.…”

“…Yung and Lawrence conclude (see Ref [4]) that Peterson's equation correctly interrelates the fatigue notch factor with elastic stress concentration factors for welded joints: Equation 9.4 is sometimes modified by introducing the fatigue notch factor K f instead of K t .…”

“…The initial flaw has often been assumed to have a depth greater than 0.1 mm, sometimes 0.25 mm. It was Lawrence et al who first suggested the TPM, and a good overview is given in Refs [4] and [5]. These flaws directly start the fatigue crack propagation and the fatigue initiation period can be ignored.…”

The Effect of Specimen Dimension on Residual Stress Relaxation of the Weldments

“…[1] The residual stresses that develop in a part during manufacture or use are one of the most influential factors in determining the fatigue resistance of welded components. [2][3][4][5] Common manufacturing methods, e.g. welding, machining, hardening, casting and forging, can all produce residual stresses in the final product.…”