Welding simulation of tubular K-joints in steel S690QH

Jean-Marie Drezet, Alain Nussbaumer, Farshid Zamiri Akhlaghi
CRC press, 2015
Conference paper

Residual stress state in planar tubular K-joints, in the chord within the gap region between the two braces, is studied using numerical weld modelling. The motivation comes from past full-scale fatigue tests on tubular trusses made of various steel grades with sizes typical of bridge trusses, which shows that the cracking occurs at the hot spots located in this region. Residual stress field characterization is needed in order to assess its role in fatigue cracking, especially for the case of cracks occurring on the compression brace side. Comparison between residual stress field in a Y-joint and a K-joint is made to assess the significance of restraining effect in the gap region. Phase transformations during welding and cooling down are determined and their impact on the final residual stress state is evaluated. Computed residual stresses are compared to the neutron diffraction measurements. Transient thermal field and cooling times substantially affect phase transformations. Therefore, their accurate reproduction in the analysis is important.

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Jean-Marie Drezet, Alain Nussbaumer, Farshid Zamiri Akhlaghi
CRC press, 2015
Conference paper

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https://infoscience.epfl.ch/record/215458?ln=en

About this result

Related concepts (12)

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Related publications (12)

Related publications

Numerical investigation of welding residual stresses in planar bridge trusses made of CHS steel proﬁles

Claire Acevedo, Alain Nussbaumer, Farshid Zamiri Akhlaghi

The weld-induced residual stresses in a tubular planar K-shaped connection made of construction steel grades S355J2H and S690QH are evaluated using three-dimensional finite element models in thermo-mechanical simulation of welding process. Both lumped single-pass and multi-pass simulation alternatives are examined. The transversal component is the largest residual stress component at the gap region for all models, with values reaching the yield strength of studied steel grades. The shapes of residual stress profiles evaluated from the multi-pass models for the two steel grades show a similar trend. Although this can change when the effects of phase transformations will be considered. Considerable difference in the residual stress distribution in the gap region is observed between multi-pass welding simulation and equivalent single-pass models for both steel grades studied. For the single-pass models, the effect of using element activation on the residual stresses are negligible.

CRC Press/Balkema2012

Numerical modelling and experimental investigation on welding residual stresses in large-scale tubular K-joints

Claire Acevedo, Jean-Marie Drezet, Alain Nussbaumer

This paper is devoted to the experimental and numerical assessment of residual stresses created by welding in the region surrounding the weld toe of tubular K-shaped joints (i.e. region most sensitive to fatigue cracking). Neutron-diffraction measurements were carried out on K-joints cut from large-scale truss beams previously subjected to high cycle fatigue. Tri-axial residual stresses in the transverse, longitudinal and radial direction were obtained from the weld toe as a function of the depth in the thickness of the tube wall. In addition, thermomechanical analyses were performed in three-dimensional using ABAQUS and MORFEO finite element codes. Experimental and numerical results show that, at and near the weld-toe surface, the highest residual stresses are critically oriented perpendicularly to the weld direction, and combined with the highest externally applied stresses. Based on a systematic study on geometric parameters, analytical residual stress distribution equations with depth are proposed.

Wiley-Blackwell2013

Influence of welding residual stresses on stable crack growth in tubular K-joints under compressive fatigue loadings

Claire Acevedo, Alain Nussbaumer

Tubular bridge design has to deal with fatigue issues. The fatigue susceptibility of these bridges, composed of circular hollow section profiles welded together in K-joints, is mainly due to stress concentrations, to welding imperfections and to tensile residual stresses induced by the welding process. Since these residual stresses are unknown for K-joints, measurements were carried out in vicinity of weld toes using the incremental hole-drilling method, X-ray diffraction and neutron diffraction in particular. Re-sults from these techniques show that on the first millimeters from the surface, the most important tensile re-sidual stresses are oriented perpendicular to the weld and reach the yield strength. According to experimental investigations on two large scale specimens, it is established that tensile residual stresses have a strong influ-ence down to a depth of 2-3 mm from the surface, allowing cracks to propagate in compressive joints. Prelim-inary Finite Element Analyses are presented in this paper.

CRC Press/Balkema, Taylor & Francis group2010

Fatigue (material)

In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, t

Residual stress

In materials science and solid mechanics, residual stresses are stresses that remain in a solid material after the original cause of the stresses has been removed. Residual stress may be desirable o

Welding

Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct f