2-PARAMETER (J-M) DESCRIPTION OF CRACK-TIP STRESS-FIELDS FOR AN IDEALIZED WELDMENT IN SMALL-SCALE YIELDING

The crack tip stress-field in a trimaterial finite element model has b een examined. The model represents an idealised steel weldment with a crack located at the fusion line. The model was loaded with a KI displ acement field to simulate small scale yielding conditions. The effect of changing the weld metal plastic properties and the HAZ layer thickn ess on the crack tip stress-field was studied, keeping the material pr operties of the HAZ and base metal constant. The results show that the calculated J-integral remains path independent in the trimaterial mod el. It is confirmed that the crack tip stress-fields can be normalised by the J-integral. The mismatch constraint can be characterised by a difference field, which is independent of the normalised distance from the crack tip. The results show that changes of HAZ thickness only ha ve a small effect on the stress-fields close to the crack tip. The har denability of the weld metal influences on the slope of the crack tip stress distribution, but for small changes in hardenability, this effe ct can be neglected. The results indicate that the difference fields s how some radial dependence when a homogeneous reference field is used, but the radial dependence was removed by introducing an inhomogeneous reference field. The effect of changes in the weld metal yield streng th has been described with a two parameter (J-M) formulation using the inhomogeneous reference field.