negetive temperature near the WELD!!!

[feri313]

hi all,
I'm trying to simulate the welding process.
I've faced a problem...
the temperature of some nodes that the heat source is to pass them next, get values like -138'C.
and some times get to the absolute zero, and an error is the result.
this nodal points are infront of weld pool on the weld direction.
at the time the temp in the model, at such a point gets to the minimum, we have the maximum temp near 3000'c at point just near that. some times at the next node of the cubic element along the weld line.
you can see the image in attachment.

thanks for any attention,

 

[corus]

It appears a very coarse mesh for a problem where you have rapid variations in temperature/heat flux. Try refining the mesh and see if the error reduces, or you get more sensible answers.

corus

 

[feri313]

hi corus,
thanks for attention and reply
I examined finer mesh and az u said the value of negetive temperature near the weld arc, reduced.
but I read a paper on simulation (by L.E.Lindgren) that pointed out using lumped heat capacity matrix, instead of consistent heat capacity matrix to overcome the negetive tempratures in the region near the weld arc.
now I'm looking for how I can manage this matrix in ABAQUS code...
tnx again