مقاله جوشکاری Characterization of microstructure and deformation behaviour of resistance spot welded AZ31 magnesium alloy

مقاله جوشکاری با عنوان : Characterization of microstructure and deformation behaviour of resistance spot welded AZ31 magnesium alloy

N. Kishore Babua,∗, S. Brauserb, M. Rethmeierb,c, C.E. Crossd

چکیده : 

Resistance spot welds were prepared on 3 mm thick sheets of continuous cast and rolled AZ31 magnesium
alloy. The microstructure and composition analysis of weld nugget, heat affected zone (HAZ)
and base metal were examined using optical and scanning electron microscopy (HR-SEM and EDS/X).
The resistance spot welded magnesium alloy joints consist mainly of weld nugget and HAZ. The nugget
contains two different structures, i.e. the cellular-dendritic structure at the edge of the nugget and the
equiaxed dendritic structure in the centre of the nugget. The structure transition is attributed to the
changes of solidification conditions. In the HAZ, grain boundary melting occurred and grain boundaries
became coarse. It has been shown that hardness reduction in the weld nugget and HAZ compared with
base metal is evident due to dendritic microstructure and grain growth, respectively. The results showed
that spot welded joints have failed in interfacial mode under torsion and tensile–shear loading conditions.
Digital image correlation during tensile–shear testing showed that low surface strains occur in the
interfacial failure mode, because fracture and deformation happened primarily in the nugget area.

مقاله جوشکاری Metallurgy and mechanical performance of AZ31 magnesium alloy friction spot welds

مقاله جوشکاری با عنوان :

Metallurgy and mechanical performance of AZ31 magnesium alloy friction spot welds

Leonardo Contri Campanellia,∗, Uceu Fuad Hasan Suhuddinb, Armando Ítalo Sette Antoniallia,
Jorge Fernandez dos Santosb, Nelson Guedes de Alcântaraa, Claudemiro Bolfarini

چکیده مقاله:

Microstructural features were studied along the cross-section of AZ31 magnesium alloy friction spot
welded joints made using different combinations of welding parameters. Static lap shear testing was performed
to evaluate the mechanical properties of the welded joints, and the resulting fracture mechanisms
and crack propagation paths were fully examined. Failure load is optimized when the welding procedure
is performed with the combination of parameters that maximizes the material mixing, the size of fully
metallurgical bonding and simultaneously minimizes the vertical displacement of hook region. The welds
demonstrate three failure modes during lap shear testing: through the weld and non-circumferential
pull-out modes, in which crack propagation crosses the recrystallized zone, and circumferential pull-out
mode, around this zone.

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مقاله جوشکاری New parametric study of nugget size in resistance spot welding process using finite element method

مقاله جوشکاری با عنوان : New parametric study of nugget size in resistance spot welding process using finite element method

Hamid Eisazadeh a,*, Mohsen Hamedi b, Ayob Halvaee

چکیده :

Resistance spot welding process (RSW) is one of important manufacturing processes in automotive
industry for assembling bodies. Quality and strength of the welds and therefore body mainly are defined
by quality of the weld nuggets. The most effective parameters in this process are: current intensity, welding
time, sheet thickness and material, geometry of electrodes, electrode force, and current shunting. In
present research, a mechanical–electrical–thermal coupled model in a finite element analysis environment
is made using. Via simulating this process, the phenomenon of nugget formation and the effects
of process parameters on this phenomenon are studied. Moreover, the effects of welding parameters
on temperature of faying surface are studied. Using this analysis, shape and size of weld nuggets are computed
and validated by comparing them with experimental results from published articles. The methodology
developed in this paper provides prediction of quality and shape of the weld nuggets with variation
of each process parameter. Utilizing this methodology assists in adjusting welding parameters so that
costly experimental works can be avoided. In addition, the process can be economically optimized to
manufacture quality automotive bodies.

مقاله جوشکاری Welding time effect on mechanical properties of automotive sheets in electrical resistance spot welding

مقاله جوشکاری با عنوان :

Welding time effect on mechanical properties of automotive
sheets in electrical resistance spot welding

S. Aslanlar a,*, A. Ogur b, U. Ozsarac a, E. Ilhan a

چکیده:

In this study, the effects of welding time on the tensile-peel strength and tensile-shear strength of welding joints in electrical resistance
spot welding of chromate micro-alloyed steel sheets having 1.2 mm thicknesses were investigated. A timer and current controlled electrical
resistance spot welding machine having 120 kV A capacity and a pneumatic application mechanism with a single lever was used to
prepare the specimens. Welding current periods of 5–10 kA and 12 kA were selected, and it was adjusted by increasing 5 cycle from 5
cycle to 15 cycle during the welding process. The electrode pressure was fixed at 6 kN. The welding joints were exposed to tensile-peel and
tensile-shear tests, and the effect of welding time on tensile-peel strength and tensile-shear strength was researched by using related period
diagrams. The optimum welding times were obtained.