A comparison of fatigue life improvements obtained by weld reinforcement and toe grinding
Mullen, Christopher Louis
Merwin, John E.
Master of Science
A study is made of two treatments which help to improve the fatigue life of a welded structure. Experimental data are examined to assess the relative magnitude of the improvements under a bending type of loading. The results of this investigation are discussed in the light of stress distribution information obtained from a finite element analysis of two welds having different weld shapes. Reinforcement is found to achieve reductions in peak stress at the weld toe not only by reducing the angle at which the weld bead meets the plate surface but also by increasing the leg length which reduces the moment developed at the weld toe location. These reductions in stress are accompanied by reductions in strain which, in the presence of repeatedly applied tensile forces, make the weld toe more resistant to the formation and propagation of cracks. Toe grinding is shown to modify the shape and surface finish of the weld toe. These modifications vary significantly with the tool used in the grinding. At low load levels toe grinding with a tool that not only provides a beneficial curvature to the toe but also removes potential crack initiation sites may lead to improvements which are greater than those obtained by reinforcement.