THE EFFECT OF MULTIAXIALITY ON THE EVALUATION OF WELDMENT STRENGTH REDUCTION FACTORS IN HIGH-TEMPERATURE CREEP

The conventional way to define the weldment creep strength reduction f actor is usually based on uniaxial creep data of weld metals and paren t metals. In order to take the multiaxial effect into consideration, t his paper has defined a structural transfer function which can be eval uated from general creep stress analysis. An analytical model is then proposed in the light of the function. Two numerical examples of typic al weld properties show that the transfer function has a load-independ ent feature, which allows one to obtain multiaxial stress components i n a weldment through minimal computation effort. Fairly good estimatio n of the stress level in the weld metal is achieved. On the basis of t he present semi-analytical procedure, the weldment creep strength redu ction factors are evaluated. For a 0.5Cr0.5Mo0.25V butt-welded tube un der interna pressure, which has a higher weld metal creep-rupture stre ngth, and lower weld metal creep strain rate, the reduction factors ra nge from 0.9 to 0.95. For the AISI 316 butt-welded tube of cold-worked parent metal and creep soft weld metal, lower strength reduction fact ors are found, but they may still be nonconservative due to stress enh ancement in the heat-affected zone.