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+ سجاد سه‌شنبه 6 مهر 1395 10:10

مقاله جوشکاری با عنوان:

RESISTANCE SPOT WELDING OF MAGNESIUM
ALLOY SHEETS WITH COVER PLATES

S. Satonaka, C. Iwamoto, G.-i. Murakami
and Y. Matsumoto

چکیده مقاله:

Lightweight materials such as high-strength steels and aluminum alloys are widely used in automotive components
for the purposes of weight reduction and consequent higher fuel effi ciency. As new alloys have been
developed, magnesium alloys have become attractive for the production of automotive components due to
their unique properties, such as high specifi c strength, damping capacity, and recyclability. In the assembly
process of these materials, resistance spot welding (RSW) is used to construct thin sheet structures. Although
RSW of steel sheets with high weld quality has already been established, the following problems remain with
regard to RSW of magnesium alloys: high welding current, degeneration of electrodes, and blowholes and
expulsion in or around the nugget. In this study, RSW with cover plates was applied to magnesium alloy sheets
to investigate the performance of spot-welded joints. The weld quality was evaluated based on the tensile
shear strength of the joints, the shape and the size of the nugget, and the appearance of blowholes and
expulsion. Since RSW with cover plates is similar to conductive heat resistance seam welding (CHRSMW),
the results showed that RSW with cover plates enabled the spot welding of a magnesium alloy with a large
nugget and high tensile shear strength in the joint. It was also shown that blowhole-free spot welds with a
large nugget and high tensile shear strength were obtained for welding currents above 8 000 A with a long
down-slope time of welding current and a high electrode force.


خرید و دانلود مقاله جوشکاری RESISTANCE SPOT WELDING OF MAGNESIUM ALLOY SHEETS WITH COVER PLATES

+ سجاد دوشنبه 5 مهر 1395 11:49

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.


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

+ سجاد دوشنبه 5 مهر 1395 10:08

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.


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

+ سجاد دوشنبه 5 مهر 1395 08:46

مقاله جوشکاری با عنوان : Parametric Studies and Finite Element Analysis of Welded Steel in Resistance Spot Welding Process

Kishore, N.1*, Sreenu, S.2, Ramachandran, N.3, Allesu, K.

 

چکیده :

Resistance Spot Welding (RSW) is a widely used joining process for fabricating sheet assemblies in the automotive,
marine and aerospace industries. Modern vehicles contain 2000-5000 spot welded points. The main requirements of
these automobile parts are corrosion resistance of chassis, the high strength values of sheets used, the stiffness of
welded joints when exposed to an external force and the ability to absorb impacts, along with low cost and comfort.
In RSW, electrodes travel on a predetermined path and make contact with the sheets at selected weld points to apply
force. Electric current is then turned on and flows through the sheets clamped between the electrodes. Due to the
contact resistance to current flow, the temperature rises from resistance heating. When the temperature reaches the
desired fusing temperature, a molten nugget is formed, the current is shut off after a designated time to allow the
nugget to cool down and solidification of the weld spot occurs under pressure. It is proposed to study the effect of
various parameters on nugget dimensions and strength of the weld joint in RSW and concentrating on different
material and thicknesses to get good weld joint at low cost and compared with analytical part done in Ansys.


خرید و دانلود مقاله جوشکاری Parametric Studies and Finite Element Analysis of Welded Steel in Resistance Spot Welding Process

+ سجاد دوشنبه 5 مهر 1395 06:33

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.


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