{"id":461883,"date":"2026-07-28T15:54:49","date_gmt":"2026-07-28T15:54:49","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/pass-element-nodal-displacements-to-user-defined-material-subroutine\/"},"modified":"2026-07-28T16:29:30","modified_gmt":"2026-07-28T16:29:30","slug":"pass-element-nodal-displacements-to-user-defined-material-subroutine","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/pass-element-nodal-displacements-to-user-defined-material-subroutine\/","title":{"rendered":"Pass Element Nodal Displacements to User Defined Material Subroutine"},"content":{"rendered":"

<p><p>I am working on implementing a user defined material model that requires access to the displacement field directly to include some atypical components like the hessian of the displacement field. <\/p><p>How can I pass the element nodal displacement field into the user defined material subroutine? I looked through all the documentation and a lot of the code in the object file version of LS-DYNA. However, many of the variables are not defined, e.g. in commented code sections, and the naming convention doesn’t not provide a sufficient description to make an educated guess. <\/p><p>I know it seems a little odd but the deformation gradient is right there which is one step removed from the data I need. I would think the displacements are nearby I just don’t know where to find them.<\/p><p>Thanks in advance for any assistance you can offer. <\/p><\/p><p> <\/p><p><p> Edit 7\/28\/2026 12:15p <\/p><\/p><p><p> After some further digging it seems like it might be possible to define my own solid element type which has a call to the usrmat() subroutine. The user defined element subroutine has access to the nodal displacement field which I could then pass to the main user defined material subroutine usrmat() and on into the individual umatxx() subroutines where the material behavior is actually defined. Seems like a long and tedious work around. <\/p><\/p><p><p> I am also wondering if the nodal displacements are more directly accessible to the user defined material subroutine through a common block data structure. That would be very straightforward and simple to use. More digging on this required. I was hoping that’s how the displacement field was referenced in the user defined element subroutine and I could just copy it but alas tis not the case. <\/p><\/p><p><p> Thinking about it more here I am going to assume that the usrmat() function called from the standard solid element subroutine does not pass the nodal displacements to the usrmat() subroutine, and I would need access to that code to make that modification. Which makes me think that the user defined element is the way to go. However, if I update the subroutine call format are other parts of the code like the standard solid element function call going complain; I’m going to try this first because it is the simplest solution. If that doesn’t work then, I think one could define a custom usrmat_custom() which would be called by the user defined element and could be passed the displacement field. <\/p> <\/p><p><p> Here’s to chasing little white rabbits and jabberwockies. <\/p><\/p><\/p>\n","protected":false},"template":"","class_list":["post-461883","topic","type-topic","status-publish","hentry","topic-tag-displacement","topic-tag-material-model","topic-tag-material-property","topic-tag-nodal-displacement","topic-tag-user-defined-1","topic-tag-user-defined-function-1"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t