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Heat generation with user-subroutine UMATHT

Heat generation with user-subroutine UMATHT

Heat generation with user-subroutine UMATHT

(OP)
Dear all,

Does anyone know how to incorporate heat generation in the user subroutine UMATHT? I cannot use HETVAL
since I want to redefine thermal material behavior and this required the use of UMATHT. The Abaqus documentation states that UMATHT can be used to apply internal heat generation, but I don't know how to do this specific task.

In the HETVAL subroutine the heat generation is defined in the variable FLUX(1), which is described in Abaqus documentation as heat flux, r (thermal energy per time per volume: JT–1L–3). However, a similar variable has to be defined in UMATHT subroutine, called FLUX(NTGRD), and is described as heat flux vector, f, at the end of the increment. In Abaqus documentation there is an example for UMATHT where the variable FLUX(NTGRD) is defined as follows:
flux(i) = -cond*dtemdx(i)
where cond and dtemdx represents the conductivity of the material and the current values of the spatial gradients of temperature, respectively.

Should I assume the FLUX(NTGRD) variable has the same meaning that FLUX(1)? Or is it possible to call FLUX(1) inside the UMATHT subroutine?

Many thanks,
João

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