An efficient method for estimation of reduction of welding residual stresses from stress-relief annealing, report 2: The characteristics of reduction of welding residual stresses in very thick joints during SR treatment

Abstract

Stress-Relief annealing (SR treatment) is included in the fabrication process of welded structures such as pressure vessels. This study aims to develop a simple analytical method which facilitates the calculation of transient and residual stresses during SR treatment, in order to easily determine reasonable conditions of SR treatment for the recent large-size structures constructed of high quality thick plates. In the first report, estimating equations in an uni-axial stress state were formulated for relaxation tests at changing and constant temperatures. In this report, the stresses relaxed by SR treatment in the thick welded joint are analyzed accurately by the finite element method based on thermal elastic-plastic-creep theory. The characteristics of the changes of the welding residual stresses in multi-axial stress state are studied in detail for further development of the estimation method.

圧力容器のような溶接構造物の製作には、圧力除去焼なまし(SR処理)が行われる。本研究は、最近の高品質厚板からなる大規模構造物に対して適切なSR処理を行うための条件を簡単に決定することを目的として、SR処理中の過渡および残留応力の計算を簡単に行える簡単な解析法を開発するためのものである。報告1においては、温度が一定の場合と変化させた場合の緩和試験に対して、1軸応力状態における評価式を立てた。本報告では、熱弾塑性クリープ理論に基づく有限要素を用いて、極厚溶接継手に対してSR処理を行って除去させた応力を正確に解析した。本推定法の開発をさらに進めるため、多軸応力状態下での溶接残留応力の変動特性を詳細に研究した。