{"id":299021,"date":"2023-08-09T15:59:43","date_gmt":"2023-08-09T15:59:43","guid":{"rendered":"\/forum\/?post_type=topic&#038;p=299021"},"modified":"2023-08-09T15:59:43","modified_gmt":"2023-08-09T15:59:43","slug":"non-linear-convergence-problems","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/non-linear-convergence-problems\/","title":{"rendered":"Non-linear convergence problems"},"content":{"rendered":"<p>Hi,<\/p>\n<p>&nbsp;<\/p>\n<p>I am modelling an elastic (E = 1 kPA, v=0.3) poro-fluid solid (CPT216 elements) reinforced with a stiff (E= 300 MPa, v=0.3) linear elastic shell (Shell281 elements). The model has a compressive ramp displacement parallel to the shell face (perpendicular to disc CSA in attached images) followed by a stress relexation period up to t=1000s. The mesh is conformal between the solid and shell elements, thus no contact is required. The linear simulation is giving very large reaction forces on the bottom face of the disc, I believe this is because the shell is not buckling.<\/p>\n<p>When attempting a non-linear analysis (large deformations ON), the solver fails on the first step due to inverted elements &#8211; I imagine due to buckling. Therefore, I am attempting to model non-linear buckling by first modelling linear buckling and then using the first buckling mode for the non-linear analysis. However, upon solving linear eigenvlue buckling I get the following error:<\/p>\n<div id=\"paraDiv\"><\/div>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/09-08-2023-1691596672-mceclip0.png\"><\/p>\n<p>&nbsp;<\/p>\n<p>Any ideas why? I am using Student Versions 2023 R1.<\/p>\n<p>&nbsp;<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/09-08-2023-1691594104-mceclip0.png\"><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/09-08-2023-1691594177-mceclip1.png\"><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/09-08-2023-1691594296-mceclip2.png\"><\/p>\n","protected":false},"template":"","class_list":["post-299021","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_author_ip":["23.206.193.150"],"_bbp_subscription":["287093","88","50680","240"],"_btv_view_count":["365"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["299021"],"_bbp_forum_id":["27791"],"_bbp_engagement":["88","240","50680","287093"],"_bbp_voice_count":["4"],"_bbp_reply_count":["9"],"_bbp_last_reply_id":["306334"],"_bbp_last_active_id":["306334"],"_bbp_last_active_time":["2023-09-12 12:28:02"]},"test":"fraser-shieldspostgrad-manchester-ac-uk"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/299021","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\/299021\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=299021"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}