{"id":307476,"date":"2023-09-19T17:07:52","date_gmt":"2023-09-19T17:07:52","guid":{"rendered":"\/forum\/forums\/topic\/negative-volume-2\/"},"modified":"2023-09-19T17:07:52","modified_gmt":"2023-09-19T17:07:52","slug":"negative-volume-2","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/negative-volume-2\/","title":{"rendered":"Negative Volume"},"content":{"rendered":"

Hello,<\/span><\/p>\n

I have modeled a timber panel in LS-DYNA using *MAT_WOOD. The analysis goes well until a negative volume error terminates the analysis.  <\/span><\/span><\/p>\n

I found some information and approaches that can help to overcome negative volumes in the following link: <\/span><\/p>\n

https:\/\/www.dynasupport.com\/howtos\/material\/negative-volume-in-soft-materials<\/a> <\/span><\/p>\n

“<\/span><\/strong>In materials that undergo extremely large deformations, such as soft foams, an element may become so distorted that the volume of the element is calculated as negative. This may occur without the material reaching a failure criterion. There is an inherent limit to how much deformation a Lagrangian mesh can accommodate without some sort of mesh smoothing or remeshing taking place. A negative volume calculation in LS-DYNA will cause the calculation to terminate unless ERODE in *CONTROL_TIMESTEP is set to 1 and DTMIN in *CONTROL_TERMINATION is set to any nonzero value in which case the offending element is deleted and the calculation continues (in most cases). Even with ERODE and DTMIN set as described, a negative volume may cause an error termination.”<\/strong><\/span><\/p>\n

I followed the approaches and set the ERODE=1<\/strong> and DTMIN= nonzero<\/strong>, however, I understood that the analysis is very sensitive to the value of DTMIN which is a reduction factor for initial time step size to determine minimum time step<\/strong>. When I set it as a number equal to or greater than 1<\/strong>, all elements will be deleted at the beginning of the analysis. When I set it as a value between zero and 0.1 (e.g. DTMIN=0.08), all elements will be deleted at some point at the middle of the analysis. It is also noteworthy that when I set it as a number between 0.1 and one (e.g. DTMIN=0.8), error termination occurs because of out of range velocity of some nodes. <\/span><\/p>\n

Therefore, I wonder how I can find the proper value for DTMIN so that I can get rid of such a negative volume error. I would appreciate it if you could give me some advice in this regard or any other approaches that can help to overcome negative volumes for my model. <\/span><\/span><\/p>\n

Thanks in advance.<\/span><\/p>\n

Regards, <\/span><\/p>\n

Mehdi<\/span><\/p>\n

\"\"<\/span><\/p>\n

\"\"<\/span><\/p>\n","protected":false},"template":"","class_list":["post-307476","topic","type-topic","status-closed","hentry","topic-tag-ls-dyna"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["290312","3136"],"_bbp_author_ip":["168.143.243.14"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["5667"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["307476"],"_bbp_forum_id":["27814"],"_bbp_engagement":["3136","290312"],"_bbp_voice_count":["2"],"_bbp_reply_count":["4"],"_bbp_last_reply_id":["307699"],"_bbp_last_active_id":["307699"],"_bbp_last_active_time":["2023-09-20 16:07:12"]},"test":"mehdisaloocmail-carleton-ca"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/307476","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/307476\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=307476"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}