Concept-conforming Modeling and Analysis of Welded Pressure Vessel Components in the Context of Structural, Notch Stress and Local Strain Approaches to Design against Fatigue

Abstract

The general applicability of local stress and strain approaches for engineering components under cyclic loading conditions is one result of intensive international research activities during the past years and decades. The implementation of these methods within specific design codes is currently in progress and will be a primary requirement of the years to come. One common feature of structural, notch stress and local strain approaches is the necessity of using concept-conforming modeling strategies as one basis of numerical stress and strain analysis. A general strategy emanating from an adaptive nominal weld seam contour is presented and examples for lifetime assessment procedures of welded pressure vessel components are given. Special attention is paid to the consequences of post weld fatigue improvement methods, such as grinding and TIG dressing on the damage process, the modeling strategy and the design approach. Direct comparison of structural details with joints in the as welded condition and submitted to post weld treatment is possible making use of the notch stress approach according to Olivier, Kottgen, and Seeger for the former and the local strain approach for the latter.