Hope your suggestion about Umat for composite shell!

Hello ABAQUS fans:
    I am a chinese students using ABAQUS to simulate welding process ,some
questions are encountered in analysis and i am confused about it ,in yahoo
abaqus group,i have learned more about abaqus from u,so i am so sorry to
interrupt to hope u give me some suggestion about my analysis.
    The questions are followed:
1.in general 3-D welding simulation,solid element are used to model the
welding pass ,which is suited in small model and not effective for a large
model because so many elements and nodes are costful. so i want to realize
that using laminated composite shell element to replace the solid element and
every shell layer will mean one weld pass. But a question comes ,for welding
using solid element ,we can model the add of weld material which are removed
at first time and be added sequently in proper time using *model change to add
or remove,but *model change only bases on the element and not available for
composite shell layer (which based on the section points or integrate point),
i know about the theory about *model change ,which means that the stiffen
(matrix) of the removed element are decreased to a very small value ,which
cant contribute to a total stiffen of the body ,and renew to its origin value
when added ,so i want to write UMAT to realize the removal  or add procedure
for the shell layer ,we can get the integrate points stiffen matrix from
abaqus (right?),and when time reached, i give the points concerned a very
small value or renew, all above ,can i realize?

2.If i can get a theory temperature value on each integrated point with time(i
have the fomula and i can write a program to calculate ,the fomula is about
the temperature changing with the time and coordinates of the points) ,can
these value be mapping into the abaqus model as a initial temperature
condition which are needed in welding residual stress analysis?

i hope i have explained my questions, right?and i hope your suggestions
eagerly!

3x for your reading!

                                                                    your
student:chenhu 

 





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