Weld Design of Heavy Duty Vehicle Bodies
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Date
2007-11
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Addis Ababa University
Abstract
The welding process has been used extensively in the fabrication of many
structures including ships, airplanes, buildings, bridges, vehicle bodies,
pressure vessels, etc. It provides many advantages over other joining
techniques. To mention only a few, it provides better mechanical properties,
air and water tightness and good joining efficiency.
However, there are various problems such as residual stresses and shape
distortion associated with the construction of welded structures. When a
material is being welded, it experiences local heat due to the welding heat
source. The temperature field inside the weldment is not uniform and changes
as the welding progresses. The welding heat cycle gives rise to a complex
strain field in the weld metal and in the base metal regions near the weld.
These strains, along with the plastic upsetting, create the residual stresses
that remain after the welding is completed. In addition, shrinkage and
distortion are also produced. Residual stresses and distortion are highly
undesirable in welding technology. Thermal stresses during welding often
cause cracking.
Some of the above weld related problems can be solved by adhering to a
preset weld design practice and employing appropriate weld process
procedure in the welding tasks.
In our country, Ethiopia, there are limited numbers of heavy duty vehicles
body builders. Those body builders extensively use welding. In those local
body builders there is lack of proper weld design practice in the fabrication of
heavy duty vehicle bodies. Moreover, there is no well developed/structured
welding process procedure they have adapted except in the cases of
internationally undertaken projects.
This fact enhances the weld related problem mentioned above on the vehicle
bodies fabricated locally. In this paper case study is made on four local
representative vehicle body builders focusing on their weld design and
WELD DESIGN OF HEAVY DUTY VEHICLE BODIES
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processes. From the case studies the general problems related to the weld
design and process of the local heavy duty vehicle body builders is identified.
Eventually, general recommendation is made on weld design and process of
heavy duty vehicle bodies that the Ethiopian heavy duty vehicle body builders
are to adapt or practice.
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Mechanical Engineering