文档介绍：Recent Developments in Analysis and Testing
of Spot and Seam Welds
Dr. Shicheng Zhang
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Brief review
•The recent developments are characterised by the progress in
local approach which was first proposed by Pook in 1975.
•The key to the local approach is the determination of local
stress parameter (LSP).
•Different concepts are under development to get LSPs at spot
welds, especially for the automotive structures.
•Various specimens are proposed for spot weld testing.
Source: SAE Papers 2001-01-0432 and 2005-01-0905, Detroit, USA; FEMFAT User Meeting, May 9-11, 2007, Steyr, Austria
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Q&A about local stress parameters at spot welds
What are LSPs at spot welds?
•They are structural stress, notch stress, ., J-integral,
CTOD and any describer of stress concentration.
Why do we need the LSPs?
•Because they condensate fatigue test data.
How to determine the LSPs?
•They can be numerically calculated (stress solver),
analytically
approximated (stress formulas) and experimentally measured
(strain gauge technique).
Source: SAE Papers 2001-01-0432 and 2005-01-0905, Detroit, USA; FEMFAT User Meeting, May 9-11, 2007, Steyr, Austria
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r
Structural stresses around a spot weld
Stress solver
Structural stress is
•plate theory stress without singularity
•linearly distributed over sheet thickness
•output stress of shell elements (FEM)
Structural stress is denoted as σ(=σui ).
Source: SAE Papers 2001-01-0432 and 2005-01-0905, Detroit, USA; FEMFAT User Meeting, May 9-11, 2007, Steyr, Austria
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Notch stress around a spot weld
Stress solver
Notch stress is denoted as σk .
Source: SAE Papers 2001-01-0432 and 2005-01-0905, Detroit, USA; FEMFAT User Meeting, May 9-11, 2007, Steyr, Austria
T
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A stress solver for spot welds
Stress solver
Input : σij
ponents around a spot weld
The Stress Solver
A package of analytic solutions to spot welds
Output : σr , σk , K, J, θ, σ
Structural stress, Notch stress, ., J-integral, Crack growth angle