The Effect of Discontinuities on The Fatigue Behavior of Transverse Butt Welds in Steel

The primary objectives of this study were to identify and evaluate the variables that influence the fatigue behavior of transverse butt welded steel members containing \nvarious weld discontinuities, and to formulate fatigue based weld quality rating crite ia. \nMathematical models for evaluating the fatigue strength of welds containing \ndiscontinuities have been developed from empirical fatigue relationships. Empirical \nrelationships for welds with nonplanar discontinuities are used to relate fatigue \nstrength zones to known discontinuity severities; welds containing planar discontinuities \nare modeled by partitioning the fatigue life into initiation and \npropagation phases for given discontinuity severities. \nAn experimental program was conducted to examine the accuracy of the mathematical \nmodels. Fatigue tests were conducted on notched mild steel plain plate specimens, \nwelded mild steel and quenched and tempered steel.specimens containing artificial \ndiscontinuities, and quenched and tempered transverse butt-welded steel specimens \ncontaining slag inclusions. Strain relaxation tests were conducted also to determine \nthe magnitude and distribution of residual stresses in the quenched and tempered \nsteel welds. \nA simple-to-use method is suggested to relate weld fabrication quality to the \nreduction in mean fatigue strength of a sound weldment. The recommendations are \nformulated from fatigue strength rating curves which relate predicted fatigue strength~ \nfor welds containing discontinuities to mean fatigue strengths of sound welds. Use of \nthe suggested weld fabrication quality levels provides a simple means of assessing \nthe effect of different types of discontinuities on the weldment fatigue strength.