IMProVe 2011 - Proceedings

Geometric Product Specification and Tolerancing
Assembly analysis for spot-welded compliant assembly:
Guidelines for formalizing the plasticity contribution
to tolerance analysis
S. Moos (a), E. Vezzetti (a), A. Zompì (a)
(a) Politecnico di Torino – Dipartimento di Sistemi di Produzione ed Economia dell’Azienda
Abstract:
The aim of the paper is to define guidelines for integrating the effects of plastic
deformations into a tolerance analysis model so to better describe the dimensional quality
of compliant assemblies, in which sheet metal parts are subjected to tolerances and are
joined by resistance spot welding.
It is developed a FEM computational model that considers the plastic effects of the
complete spot welding process. Two worst cases were analysed for a butt joint, the first
with parts mismatching with a gap and the second with parts mismatching for loading
interference.
The analysis results show an important role of material plasticity: the fixture clamping, the
electrode closure on flanges and the welding thermal cycle cause permanent deformation
on the parts and affect the assembly dimensional quality.
In conclusion, to improve the result of tolerance stack-up analysis for compliant
assemblies it is advisable to consider: isotropic plastic behaviour of material, two distinct
solution models for gap and interference geometrical conditions, the loading sequence,
contact surfaces, fixture locator position and dimensions.
Keywords: Compliant assembly analysis, Tolerance analysis, Quality, Resistance spot
welding, Plasticity
Corresponding Author: Sandro Moos
Tel.: 011 564 7294
Fax.: 011 564 7299
e-mail: sandro.moos@polito.it
Address: Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino.
June 15 th – 17 th , 2011, Venice, Italy
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IMProVe 2011 - Proceedings