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Simplified FE welding simulation of fillet welds: 3D effects on the formation residual stresses
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0003-4180-4710
Luleå Univ Technol, Div Mat Mech.
2009 (English)In: Engineering Failure Analysis, ISSN 1350-6307, Vol. 16, no 7, 2281-2289 p.Article in journal (Refereed) Published
Abstract [en]

In this study two- and three-dimensional finite element welding simulations have been carried out. The welded component studied is a T-type fillet weld which is frequently used in the heavy vehicle machine industry with plate thicknesses of eight and 20 mm, respectively. The software's used for the welding simulations is MSC.Marc and ANSYS. The objective is to study the formation of the residual stresses due to 3D effect of the welding process. Moreover, welding simulations using solid models and contact models in the un-fused weld roots were carried out in order to investigate the possible effect with respect to the residual stresses. Residual stress measurements were carried out using X-ray diffraction technique on the manufactured T-welded structure. The 2D residual stress predictions shows good agreement with measurements, hence the 2Dwelding simulation procedure is suitable for residual stress predictions for incorporation in further fatigue crack growth analysis from weld defects emanating from the weld toe and the un-fused root.

Place, publisher, year, edition, pages
2009. Vol. 16, no 7, 2281-2289 p.
Keyword [en]
Welding simulation; FEM; Residual stresses; Fillet welds; FATIGUE
National Category
Mechanical Engineering
URN: urn:nbn:se:kth:diva-8175DOI: 10.1016/j.engfailanal.2009.03.018ISI: 000268566500030ScopusID: 2-s2.0-67649591918OAI: diva2:13427
QC 20100705. Uppdaterad från submitted till published (20100705). Tidigare titel: FEM welding simulation of fillet welds: 3D effects on residual stresses.Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-07-06Bibliographically approved
In thesis
1. Residual Stress Analysis and Fatigue Assessment of Welded Steel Structures
Open this publication in new window or tab >>Residual Stress Analysis and Fatigue Assessment of Welded Steel Structures
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This doctoral thesis is concerned with fatigue life of welded structures. Several topics related to fatigue of welded structures are treated such as; weld defects and their influence on fatigue performance of welded structures, fatigue life prediction using LEFM (Linear Elastic Fracture Mechanics), fatigue testing, welding simulation, residual stress prediction and measurement and their influence on fatigue life.

The work that is reported in this doctoral thesis is part results of the Nordic R&D project QFAB (Quality and Cost of Fabricated Advanced Welded Structures) and the Swedish R&D project LOST (Light Optimized Welded Structures). One of the main objectives is to compare different welding processes for the fatigue performance, weld quality and gain understanding of the weld defects, their appearance in different welding processes and their effect on fatigue life. Another main objective is to study welding residual stresses and their effect on fatigue. The design rules are in some cases conservative and especially on the weld root sides the knowledge about the residual stress field may improve the life prediction. The aim is to develop simplified procedures for analysis of residual stresses, their relaxation and influence on fatigue life.

Fatigue testing of Hybrid Nd: YAG laser/MAG and MAG welded (tandem arc solid wire, flux cored wire, tandem flux cored wire) non-load carrying cruciform joints was carried out. Four batches were produced, tested and the results were compared. The local weld geometry of the cruciform welded joints was measured and analyzed. Residual stress measurement was carried out close to the toe region using X-ray diffraction. Weld defects, in most cases cold laps, in the cracked specimens were measured.

Further fatigue testing, weld defect assessment and residual stress and local weld geometry measurements were carried out on joints welded with flux cored and metal cored arc wires. Two-and three dimensional LEFM crack growth analysis were carried out in order to predict the influence of weld defects, local weld geometry and residual stresses.

Residual stresses in multi-pass welded tube-to-plates were studied for two different tubular joint configurations; a three-pass single-U weld groove for maximum weld penetration and a two-pass fillet (no groove) welded tube-to-plates for minimum weld penetration. Torsion fatigue tests were performed in order to study crack propagation from the weld root. Mode III propagation from the lower and upper weld toe on the same tubular joints was also studied. Some tubes were stress relieved (PWHT) and some were fatigue tested with internal static pressure.

A three dimensional finite element welding simulation of the multi-pass welded tubular joint was carried out. The calculated temperatures in the transient thermal analysis were compared with measured temperatures. The FE predicted residual stresses in the as-welded conditions were verified with hole drilling strain gage measurements. The residual stresses were used as internal stresses in the finite element model for the torsion fatigue simulation in order to study the cycle by cycle relaxation of the residual stresses in constant amplitude torsion loading.

A two dimensional finite element welding simulation procedure was developed in order to predict welding residual stress. The predicted residual stresses were used together with a developed 2D LEFM subroutine to predict the fatigue life, crack path and the effect of residual stresses on weld root defects. The developed simulation subroutines were validated with results found in the literature.

Residual stresses measurement, two-and three dimensional welding simulations were carried out in fillet welded joints in order to study the three dimensional effects of the welding process, boundary conditions and modelling technique on the formation of residual stresses.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. iv, 36 p.
Trita-AVE, ISSN 1651-7660 ; 2008:11
fatigue failure, welding, weld defects, welded joints, stress concentration, residual stress, linear elastic fracture mechanics, welding simulation, finite element analysis, fatigue crack growth.
National Category
Mechanical Engineering
urn:nbn:se:kth:diva-4687 (URN)
Public defence
2008-04-25, E1, E-huset, KTH, Lindstedtsvägen 3, Stockholm, 10:00
QC 20100706Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2011-04-12Bibliographically approved

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