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Managing distortion in welded structures using FEM
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
2013 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Welding as high productive joining method is widely employed in automotive, aerospace and

shipbuilding industries. In practice, welding distortion brings about undesirable effects on

production accuracy, appearance and strength of welded components. Thus, in order to

increase the productivity and decrease the cost of the product, prediction and analysis of

welding deformation are key factors in industrial context.

Distortion of a structure can be measured experimentally; whilst in case of large or complex

structures it is expensive and also time consuming. Numerical analysis is then performed

using finite element method (FEM) that reduces the cost; however, in case of large welded

structure and considering extremely nonlinear mechanical behavior of welding the

computational expense incurred which must be cut through elastic analysis. In this sense, the

residual plastic strain, namely inherent strain as a source of residual stress and welding

distortion should be analyzed.

The purpose of this study is to detail the prediction procedure of deformation in welded

structure by elastic finite element modeling using inherent strain method. As a matter of fact

inherent strain as an inelastic permanent strain or residual plastic strain, which exists in

vicinity of fusion zone, is responsible for welding deformation and residual stresses.

Comparing with elastic plastic analysis, inherent strain method has less computing time

however the state of welding may be not investigated in detail; Furthermore, appropriate

assumption of inherent strain region and determining the accurate values of inherent

deformations in each typical joint bring about some limitations. On the other hand, just the

elastic modulus and Poisson’s ratio at room temperature is used in elastic FEM, and there is

no need for temperature material properties. So, at the present time, thermal elastic plastic

finite element method can be used to predict residual stresses and welding deformations in

small or medium structures but for large components elastic FEM is promising method.

Place, publisher, year, edition, pages
2013. , 38 p.
TRITA-AVE, ISSN 1651-7660 ; 2013:44
National Category
Vehicle Engineering
URN: urn:nbn:se:kth:diva-157498OAI: diva2:770237
Available from: 2014-12-10 Created: 2014-12-10 Last updated: 2014-12-10Bibliographically approved

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