3D modelling of plug failure in resistance spot welded shear-lab specimens (DP600-steel)

Nielsen, Kim Lau

doi:10.1007/s10704-008-9305-4

Cited by 35 publications

(10 citation statements)

References 36 publications

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“…One of the methods used for testing the strength of spot welds is a tensile test for a shear-lab specimen, where two plate strips are welded together by a single spot weld. The failure of such a shear-lab test made of DP600-steel has been analyzed in [95], using the GTN model. Vickers hardness measurements on the cross-section of welds have been used in an experimental investigation to measure the distribution of the initial yield stress.…”

Section: Resistance Spot Welded Specimensmentioning

confidence: 99%

Ductile failure modeling

et al. 2016

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Section: Resistance Spot Welded Specimensmentioning

confidence: 99%

Ductile failure modeling

et al. 2016

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“…To model the asymmetric localisation of plastic flow, one quarter of the micro-specimen is modelled by applying symmetric condition in the mid-thickness direction and anti-symmetric conditions at the mid-length (loading direction). The anti-symmetry conditions are introduced following the dynamic approach described in Nielsen (2008b).…”

Section: Micro-tensile Testing Simulationsmentioning

confidence: 99%

Modelling of plastic flow localisation and damage development in friction stir welded 6005A aluminium alloy using physics based strain hardening law

Nielsen

Pardoen

Tvergaard

et al. 2010

International Journal of Solids and Structures

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a b s t r a c tPlastic flow localisation and ductile failure during tensile testing of friction stir welded aluminium specimens are investigated with a specific focus on modelling the local, finite strain, hardening response. In the experimental part, friction stir welds in a 6005A-T6 aluminium alloy were prepared and analysed using digital image correlation (DIC) during tensile testing as well as scanning electron microscopy (SEM) on polished samples and on fracture surfaces. The locations of the various regions of the weld were determined based on hardness measurements, while the flow behaviour of these zones was extracted from micro-tensile specimens cut parallel to the welding direction. The measured material properties and weld topology were introduced into a 3D finite element model, fully coupled with the damage model. A Voce law hardening model involving a constant stage IV is used within an enhanced Gurson type micromechanical damage model, accounting for void nucleation, growth and coalescence, as well as void shape evolution. The stage IV hardening, observed in Simar et al. (2010), was found to increase the stiffness during plastic flow localisation as well as to postpone the onset of fracture as determined by the void coalescence criterion. Furthermore, the presence of a second population of voids was concluded to strongly affect the fracture strain of the high strength regions of the welds. This modelling effort links the microstructure and process parameters to macroscopic parameters relevant to the optimisation of the welds.

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“…In the absence of local heat affected zone (HAZ) constitutive behaviour, most authors would scale the base metal stressstrain curve according to the evolution of a hardness profile for example. [1][2][3][4] The approach developed in this study consists in an experimental-based characterization of the local microstructures and mechanical properties of spot welds. The constitutive behaviours obtained can then be used for an accurate modelling of the weld response under various loading modes.…”

Section: Introductionmentioning

confidence: 99%

HAZ Microstructures and Local Mechanical Properties of High Strength Steels Resistance Spot Welds

et al. 2011

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as in the case of DP450, a decrease of martensite hardness can be observed for 1.0 mm cycles as compared to water quenches. This may be due to an auto-tempering phenomenon, which can be activated by the decreasing cooling rates at the end of the cooling cycles (electrodes removal). Once again, the hardness levels are comparable with the ones obtained after welding, 1 mm He hardness being the closer to the value expected in the weld.As a conclusion for this section, subcritical and coarse grained HAZ weld microstructures could be successfully reproduced experimentally. These simulated specimens are used in the following in order to study their detailed mechanical properties. Local Constitutive BehaviourThe constitutive behaviour in tension of the different SCHAZ and CGHAZ is illustrated in Fig. 14. The true stress vs. true plastic strain is plotted until the onset of plastic localization. As expected from the microstructural observations and micro hardness of DP450, the different subcritical thermal cycles do not alter the base metal constitutive behaviour significantly. Both ultimate tensile strengths and uniform elongations remain in the same order of magnitude ( Fig. 14(a)). On the contrary, the different cooling cycles from 1 200°C result in a strong evolution of strain hardening and ultimate tensile strength. Martensitic microstructures (water quench and 1.0 mm cycle) are characterised by a high strength and low ductility, while the bainitic 3.0 mm microstructure exhibits a lower strength and increased ductility.In the case of DP980, martensite tempering in the SCHAZ highlighted previously allows an increase in ductility and a loss of yield and ultimate tensile strengths ( Fig. 14(b)). This softening is more pronounced for the 3.0 mm thermal cycle than for the 1.0 mm one, in accordance with a longer time in the subcritical temperature range. CGHAZ microstructures present high strengths and low ductilities. However, it can be noticed that the 1.0 mm and 3.0 mm microstructures exhibit lower strength in comparison with the water quench. This may be attributed to the auto-tempering of the martensite in formation at the end of the CGHAZ thermal cycles, where the cooling rates are reduced.Moreover, it is worth to mention that martensitic microstructures present low ductility, but not zero. A few percents uniform elongation can be obtained even with water quenched DP980. This can be related to the relatively low level of carbon content for such automotive steels. ConclusionA Finite element analysis of the resistance spot welding process was conducted in this paper in order to assess the order of magnitude of heating and cooling rates experienced in dual phase steel spot welds. The evolution of thermal cycles when welding sheets with thicknesses in the range [1.0-3.0] mm was highlighted. Spot welding thermal cycles could then be simulated experimentally with a Gleeble and their influences on microstructure and mechanical properties investigated. Gleeble simulations were targeted for the reproduction of the thermal ...

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3D modelling of plug failure in resistance spot welded shear-lab specimens (DP600-steel)

Cited by 35 publications

References 36 publications

Ductile failure modeling

Ductile failure modeling

Modelling of plastic flow localisation and damage development in friction stir welded 6005A aluminium alloy using physics based strain hardening law

HAZ Microstructures and Local Mechanical Properties of High Strength Steels Resistance Spot Welds

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