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Residual Stress Analysis and Fatigue of Multi-pass Welded Tubular Structures
KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.ORCID-id: 0000-0003-4180-4710
2008 (Engelska)Ingår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 15, nr 7, s. 863-874Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The purpose of this study is to investigate the residual stresses near the weld root and the weld toe for multi-pass welded tube-to-plates. Two different tubular joint configurations were studied; 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. A 2D axi-symmetric finite element model was developed to calculate the temperature distribution, HAZ, penetration depth and the residual stress distribution for the sequentially coupled thermo-mechanical analysis. The calculated residual stresses was compared with experimental results and showed qualitatively good agreement. Torsion fatigue tests were performed in order to study crack propagation from the weld root, lower and upper weld toe in mode III. Some of the tube structures were loaded with a static internal pressure in order to separate the root crack and initiate the crack growth in mode III. Another batch was PWHT and fatigue tested, in order to study the influence of residual stresses.

Ort, förlag, år, upplaga, sidor
2008. Vol. 15, nr 7, s. 863-874
Nyckelord [en]
welding simulation; residual stresses; tubular joints; fatigue; fracture mechanics; CRACK-GROWTH; MODE; DEFORMATIONS; SIMULATION; DEFECTS; JOINT
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
URN: urn:nbn:se:kth:diva-8172DOI: 10.1016/j.engfailanal.2007.11.016ISI: 000256631600007Scopus ID: 2-s2.0-41849142003OAI: oai:DiVA.org:kth-8172DiVA, id: diva2:13424
Anmärkning
QC 20100702Tillgänglig från: 2008-04-03 Skapad: 2008-04-03 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
Ingår i avhandling
1. Residual Stress Analysis and Fatigue Assessment of Welded Steel Structures
Öppna denna publikation i ny flik eller fönster >>Residual Stress Analysis and Fatigue Assessment of Welded Steel Structures
2008 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2008. s. iv, 36
Serie
Trita-AVE, ISSN 1651-7660 ; 2008:11
Nyckelord
fatigue failure, welding, weld defects, welded joints, stress concentration, residual stress, linear elastic fracture mechanics, welding simulation, finite element analysis, fatigue crack growth.
Nationell ämneskategori
Maskinteknik
Identifikatorer
urn:nbn:se:kth:diva-4687 (URN)
Disputation
2008-04-25, E1, E-huset, KTH, Lindstedtsvägen 3, Stockholm, 10:00
Opponent
Handledare
Anmärkning
QC 20100706Tillgänglig från: 2008-04-03 Skapad: 2008-04-03 Senast uppdaterad: 2011-04-12Bibliografiskt granskad
2. Residual Stress Analysis and Fatigue of Welded Structures
Öppna denna publikation i ny flik eller fönster >>Residual Stress Analysis and Fatigue of Welded Structures
2006 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

This licentiate thesis is generally concerned with the fatigue 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. The work that is reported in this thesis is a part result of a Nordic research project QFAB (Quality and Cost of Fabricated Advanced Welded Structures). One of the main objectives is to compare different welding processes in fatigue performance, weld quality and gain understanding of the weld defects, their appearance in different welding processes and their influence 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 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. In one study 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 was measured. 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 3 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.

Ort, förlag, år, upplaga, sidor
Stockholm: Farkost och flyg, 2006. s. iii, 21
Serie
Trita-AVE, ISSN 1651-7660 ; 2006:02
Nyckelord
welding, fatigue, finite element analysis, fracture mechanics, residual stresses
Nationell ämneskategori
Maskinteknik
Identifikatorer
urn:nbn:se:kth:diva-3872 (URN)91-7178-264-8 (ISBN)
Presentation
2006-03-01, S40, Farkost o Flyg, teknikringen 8, stockholm, 00:00
Opponent
Handledare
Anmärkning
QC 20101109Tillgänglig från: 2006-03-13 Skapad: 2006-03-13 Senast uppdaterad: 2010-11-09Bibliografiskt granskad

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