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Residual Stresses and Distortion
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Residual Stresses and Distortion
Lesson Objectives
When you finish this lesson you will
understand:• the generation of residual stress and
distortion in welds
• mechanisms to reduce residual stress
Learning Activities
1. Read Handbook
pp 21822!
2. "iew #lides$%. Read &otes'
(. )isten to lecture
*. +o online
workbook
Keywords
,hermal -pansion /oefficient' Residual #tress' +istortion'
#tressRelief
http://we019.eng.ohio-state.edu/wenc/wenc.cfmhttp://we019.eng.ohio-state.edu/we300/w300t/we300.htm
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Welding +esignWelding design involves consideration
of strength requirements cost and
service conditions
0 !echanical " #hysical $ro$erties
0 %oint Design 0 Welding stress and distortion
0.1.1.3.0.T1.95.12
&overed
'arlier
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T ∆=α ε
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Residual #tress +istortion in Welds
• Heat flows from the weld area and causing
the oint area to epand (See #revious !odule)
• ,hermal epansion and contraction due to
welding can lea3e behind permanent stress
and distortion
• Higher heat input welds are more prone to
residual stress and distortion
• 4ncreased restraint can decrease distortion
but can result in higher residual stress
Residual Stress and Distortion
0.1.1.3.3.T18.95.12
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Residual #tress 5attern• Residual stress is
present across an
unrestrained butt weldafter cooling
• ,ension near weld bead
• /ompression away
from the weld bead
• Restraint can affect this
stress stateCompression
Tension
Residual Stress and Distortion
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*urn to the $erson sitting ne+t to you and discuss (, min-).
• We have seen from the metallurgy module that dislocation
tangles and $ile/u$s occurring above the yield strength of
materials cause the higher stresses- We have seen here that
by a tem$erature cycle that varies across the $late we have
regions that yield and residual stresses occur- We have seen
that im$osing o$erating stresses above yield cause changesin the residual stress distribution by movement of the
dislocations- 0ow else then might we get rid of some of
these dislocations to remove these residual stresses1
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,ypes of +istortion
Residual Stress and Distortion
0.1.1.3.3.T19.95.12
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+istortion
Transverse Shrinkage
Rotational Distortion Longitudinal Bending Buckling
Longitudinal Shrinkage Angular Change
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-liminating +istortion
• 5reset members to
counteract distortion
• 6itures to clampworkpiece in place
0 Restraint reduces
distortion but increases
residual stress
• #tressrelief heat
treatment
Angular distortion after welding
Preset members before welding
Residual Stress and Distortion