TWI Industrial Member Report Summary 733/2002
E J C Kellar, C I C Manger and S M Tavakoli
Improved methods for including residual stresses in defect assessment procedures are becoming available. The latest generation of guidance documents, including BS 7910, API 579 and reports from the European SINTAP project, provide standard residual stress distrubutions for common welded joint configurations. Some also give stress intensity factor (SIF) solutions for the non-linear distributions which are characteristic of residual stresses.
The new residual stress profiles provide a practical alternative to the traditional assumption that 'residual stresses at welds are equal to yield'. The excessive conservatism which may be associated with this assumption can be reduced or eliminated.
Examples are given in this report of the variation of SIF as a function of crack size for a range of defects and weld configurations including long and short surface defects at butt and T butt welds in plates. To demonstrate the benefits of using the standard residual stress profiles, the SIF values are compared with the stress intensity factor for the same defect subject to uniform yield magnitude residual stresses.
- Determine the sensitivity of the calculated stress intensity factors to the assumed residual stress profiles and solution methods.
- Develop techniques for applying the available stress intensity factor solution techniques in conjunction with the recommended residual stress profiles.
- Provide example solutions for typical joint and defect geometries.