A Simple Model For Prediction Of Creep Stress
Redistribution For Butt-welded Joints
Author(s)
K. Zarrabi
Abstract
The creep life of pressure components used in power and chemical processing
plants is often determined by creep failure of butt-welded joints. Currently, there
exists no simple yet quantifiable model for predicting the stress redistribution
between the weld, heat affected zone and base material for the purpose of life
assessment of butt-welded joints. This paper describes an analytical/numerical
model and its verification for predicting the stress redistributions in a butt-welded
joint. It is shown that: (1) the proposed model is simple but it predicts the
maximum stress variation with time accurately, (2) stresses were redistributed
from the softer material (e.g., the heat affected zone) to the harder material (e.g.,
the weld).
Keywords: creep, butt-welded joints, life assessment.
1 Introduction
Most pressure components in high temperature plants contain welded joints.
These joints operate under conditions of elevated temperatures and sufficiently
high stress such that creep damage and failure can occur. The design of these
joints must therefore take into account the risk of creep rupture. In general,
existing standard codes specify allowable stresses for welded joints on the basis
of creep properties of base material (BM). For example, the ASME Code Case
N-47 [1] recommends the BM allowable stress is reduced by a factor to obtain
the weld allowable stress. This approach was a significant progress in the design
methodology of welded joints operating within creep range. Operating
experience, however, indicates that whilst the performance of high temperature
components, in general, exceeds the intended design, failures of welded joints
Keywords
creep, butt-welded joints, life assessment.
Related Book
Other papers in this volume
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