{"id":247400,"date":"2023-01-24T23:48:31","date_gmt":"2023-01-24T23:48:31","guid":{"rendered":"\/forum\/forums\/topic\/vertebrae-screw-pullout-analysis\/"},"modified":"2023-01-24T23:48:31","modified_gmt":"2023-01-24T23:48:31","slug":"vertebrae-screw-pullout-analysis","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/vertebrae-screw-pullout-analysis\/","title":{"rendered":"Vertebrae screw pullout analysis"},"content":{"rendered":"

Hello,<\/p>\n

I am trying to check the type of thread I used for transpedicular screw – I want to determine the force needed to pull it out of the vertebrae. My vertebrae model is divided into 3 objects – cortical bone, cancellous bone and posterior elements with proper materials assigned and shared topology. The screw is inserted into the vertebral body through the pedicle.<\/p>\n

Upper and lower vertebral body surfaces are fixed and I apply displacement of 1mm on the screw head in the longitudinal direction, trying to pull the screw out of the vertebrae.<\/p>\n

At first I have tried frictional contact (Augmented Lagrange) with 0.01 stiffness and bilinear hardening properties applied to materials – solver was unable to converge on a solution. Now I try to solve it with frictionless contact and without bilinear hardening – same thing, solver isn’t unable to converge, doesn’t matter if I use large deflection or not. I can only solve it with bonded contact and program controlled stiffness – but it says the force reaction on displacement is around 14000 N, which is at least 100 times more than I expect. <\/p>\n

<\/p>\n

Could anybody tell me, how should I set up this analysis and what are the possible reasons for it not to converge?<\/p>\n

I tried to attach .wbpz file, but it seems I can’t, I don’t know why.<\/p>\n

Thanks in advance.<\/p>\n","protected":false},"template":"","class_list":["post-247400","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["273349","79","50680","240"],"_bbp_author_ip":["23.56.168.190"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["885"],"_bbp_likes_count":["2"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["247400"],"_bbp_forum_id":["27791"],"_bbp_engagement":["79","240","50680","273349"],"_bbp_voice_count":["4"],"_bbp_reply_count":["7"],"_bbp_last_reply_id":["247657"],"_bbp_last_active_id":["247657"],"_bbp_last_active_time":["2023-01-27 01:58:33"]},"test":"patryk-sienkiewicz-105254student-pb-edu-pl"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/247400","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\/247400\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=247400"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}