Managing Welding Induced Distortion – Comparison of Different Computational Approaches

AbstractThis study aims to assess and compare three different approaches of inherent strain method for prediction of welding induced distortion; inherent strain, inherent deformation and shrinkage force approaches. The FEA was performed on T-fillet welded structures. The results are compared with elastic-plastic FEA and experiments and shows a qualitative good agreement. It is found that the inherent strain and inherent deformation approaches are suitable to predict transverse shrinkage and transverse bending whereas to predict the longitudinal shrinkage and longitudinal bending the shrinkage force approach is more suitable

D. AFSHARI et al.: PREDICTION OF THE NUGGET SIZE IN RESISTANCE SPOT WELDING ... PREDICTION OF THE NUGGET SIZE IN RESISTANCE SPOT WELDING WITH A COMBINATION OF A FINITE-ELEMENT ANALYSIS AND AN ARTIFICIAL NEURAL NETWORK NAPOVEDOVANJE PODRO^JA PRETALITVE PRI

The goal of this investigation is to predict the nugget size for a resistance spot weld of thick aluminum 6061-T6 sheets 2 mm. The quality and strength of spot welds determine the integrity of the structure, which depends thoroughly on the nugget size. In this study, the finite-element method and artificial neural network were used to predict the nugget size. Different spot welding parameters such as the welding current and the welding time were selected to be used for a coupled, thermal-electrical-structural finite-element model. In order to validate the numerical results a series of experiments were carried out and the nugget sizes were measured. The results obtained with the finite-element analysis were used to build up a back-propagation, artificialneural-network model for the nugget-size prediction. The results revealed that a combination of these two developed models can accurately and rapidly predict the nugget size for a resistance spot weld. Keywords: resistance spot weld, nugget size, finite-element analysis, artificial neural network, aluminum alloys Cilj te preiskave je napovedati velikost podro~ja pretalitve pri uporovno zvarjeni aluminijasti plo~evini 6061-T6, debeli 2 mm. Kvaliteta in trdnost to~kastega zvara dolo~ata celovitost konstrukcije, kar je odvisno predvsem od velikosti podro~ja pretalitve. V tej {tudiji sta bili za napovedovanje velikosti podro~ja pretalitve uporabljeni metoda kon~nih elementov in umetna nevronska mre`a. Izbrani so bili razli~ni parametri varjenja, kot sta varilni tok in~as varjenja, za skupni termi~no-elektri~no-strukturni model kon~nih elementov. Za oceno numeri~nih rezultatov je bilo izvr{enih ve~preizkusov in izmerjena je bila velikost podro~ja pretalitve. Rezultati, dobljeni iz analize kon~nih elementov, so bili uporabljeni za gradnjo modela umetne nevronske mre`e za napovedovanje velikosti podro~ja pretalitve. Rezultati so odkrili, da kombinacija teh dveh razvitih modelov lahko zanesljivo in hitro napove velikost podro~ja pretalitve pri uporovnem to~kastem zvaru. Klju~ne besede: uporovni to~kasti zvar, velikost podro~ja pretalitve, analiza kon~nih elementov, umetna nevronska mre`a, zlitine aluminij

GUIDELINES FOR FATIGUE ANDSTATIC ANALYSIS OF WELDEDAND UN-WELDED STEELSTRUCTURES

QC 20201224</p

GUIDELINES FOR FATIGUE ANDSTATIC ANALYSIS OF WELDEDAND UN-WELDED STEELSTRUCTURES

QC 20201224</p

Residual Stress Analysis and Fatigue Assessment of Welded Steel Structures

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&amp;D project QFAB (Quality and Cost of Fabricated Advanced Welded Structures) and the Swedish R&amp;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.QC 2010070

Reduced VARIation in the manufacturing processes enabling LIGHTweight welded structures : Highlights from the research project VariLight

QC 20201224</p

Reduced VARIation in the manufacturing processes enabling LIGHTweight welded structures : Highlights from the research project VariLight

QC 20201224</p

Reduced VARIation in the manufacturing processes enabling LIGHTweight welded structures : Highlights from the research project VariLight

QC 20201224</p