VUMAT and DOUBLE_PRECISION

shawn2008

I want to use ABAQUS/Explicit with user-subroutine VUMAT, which needsdouble precision variables. As indicated by the Reference Manual i startabaqus with "abaqus job=... user=... double" and/or on a second try with "explicit_precision=DOUBLE_PRECISION" in the abaqus environment file.
But somehow i still get e.g. the props field as single precision, because using it as real*8 in a subroutine does not work correctly.
Secondly the .log file shows two compilation/linking steps, one "double precision" and the second one "single precision".
Is this normal andwhat am I'm doing wrong?
3x

[ 本帖最后由 shawn2008 于 2007-8-31 13:19 编辑 ]

joyce_chen

有一段时间没有用ABAQUS了，为了提高计算精度，我记得自己当初是用"abaqus job=... user=... double interactive" 提交任务的，只显示用explicit double precision 进行求解。

shawn2008

谢谢！
已经知道原因了，一个USA的朋友给的解释如下，
（感觉很多时候都是abaqus软件内部原理的问题，但我们对abaqus的内部知道的太少了）

When running a double precision ABAQUS/Explicit simulation that is using a VUMAT, ABAQUS will use an initial single precision increment to "set things up", and then during the real simulation switch over to double precision.

In your case this can be a problem since your Fortran file is first called with single precision variables and then called with double precision variables. If you hard-code your Fortran file for double precision it will not work!                               ```````````````````````````
`````````````````````````````

I think that this behavior is new for ABAQUS v6.7.

I know of two ways to solve this problem:
- use "include 'vaba_params.inc" . This is an approach that I personally no not like.
- create both single and double precision shared libraries from your source file *before* calling ABAQUS. I can explain this in more detail is you want.

birdva

3# shawn2008
版主你好，我最近在编材料本构vumat，单精度时可以正常计算，但是换为双精度（real*8）时却出现code693，我也尝试着改include 'vaba_params.inc‘，但仍然出现错误，望赐教！
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