EFFECTS OF WELD DISCONTINUITIES ON FATIGUE-STRENGTH OF LASER-BEAM WELDS

The effects of weld discontinuities (i.e., weld underfill, poor joint clearance and insufficient root penetration) on fatigue strength of lap joint laser beam welds have been investigated. Fatigue testing of laser beam welds with weld discontinuities were conducted. A fatigue prediction model that takes into account weld geometry changes and a statistical analysis method were both employed to evaluate the separate effects of these discontinuities on fatigue resistance. It was found that within the dimension range studied here, inadequate root penetration and/or poor joint clearance substantially decreased the fatigue life. The presence of underfill degraded the fatigue properties, and the decrease is more pronounced as the gauge is increased. The relative importance of weld discontinuities on fatigue life is ranked in decreasing order as follows: inadequate root penetration, poor joint clearance and weld underfill.