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Professors Wang and Hou
Department of Mechanical Engineering
Chang Gung University, Taiwan
Difficulty in Measuring Temperature
Distribution
In conventional welding technology researches, its temperature
distribution is often measured by performing experiments. With
changes in welding time, input heat, input position, and heat
transfer conditions such as material density, specific heat, heat
transfer coefficient, and boundary conditions, the results of this
temperature distribution vary. Among them, an uneven distribution
greatly influences the weldment heat distortion and produces thermal
stress. However, as the major factor of welding quality, the heat
affect zone, is located on the weldment edge, its temperature
distribution is difficult to obtain using experimental measures
(only the average temperature can be measured due to the
over-1500-Celsius-degree high center temperature and the extremely
small welding point).
To Solve the Problem
To solve this problem, Professors Wang and Hou have utilized the
numerical method to construct a welding heat transfer model and set
the related welding variables. Using this model, the
temperature field of the heat affect zone can be efficiently
calculated by measuring only the surrounding low-temperature
regions, comparing them with the numerical results, and further
adjusting the welding parameters.
The governing heat transfer equation during welding is a
transitional, 3D energy equation, which can be used to calculate the
temperature of various weldment parts. Based on a finite difference
algorithm, the ADI (Alternating Direction Implicit) method used in
this research is especially fitting in solving parabolic partial
differential equations. Of second-order precision, the method
possesses the stability of unconditional convergence. Thus, the
convergence of solutions is unaffected by the time-space grid size
during numerical analysis. As the ADI method primarily converts 2D
or 3D partial differential equations into consecutive first-order
problems, it is exceptional in calculation efficiency.
Visualizing the Results Using MATFOR
With MATFOR, the computing results can be drawn in 3D structure by
adding a few lines of codes. This assists users to quickly and
precisely analyze the temperature distribution of the weldment and
further calculate the heat distortion and heat affect zone. Figure
1 demonstrates the 1500-degree iso-surface visualized using the
function mfIsoSurface (shown in red); it also illustrates the
temperature distribution result in generated by the function
msTriContour. Figure 2 animates the sliced sections of the
distribution, which facilitates debugging during program development
and enhances visual presentation. General users also benefit as
they utilize these visual results for easier analysis of the
research contents, saving time and improving communication.
Figure 1.
The 1500-degree-Celsius iso-surface is drawn (in red) while the
temperature distribution result is illustrated using
msTriContour
in various shades of blue.
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Figure 2.
The distribution of temperature is animated in sliced sections.
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Welding Technology
Welding is one important manufacturing technique for traditional
machinery industries and large precision machines. It is commonly
exploited in the joining of metals; an excellent exemplification
would be the manufacturing process of automobiles. Not only does
quality welding technique reinforce automobile body rigidity to
enhance passenger safety, it extends the life of the car body at the
same time. Other machines requiring welding technique also benefit
from similar effects.
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