{"id":50778,"date":"2020-12-21T18:57:10","date_gmt":"2020-12-21T18:57:10","guid":{"rendered":"\/forum\/forums\/topic\/energy-error-hourglass-error-in-a-piston-connecting-rod-crankshaft-engine-assembly-explicit-dynamics\/"},"modified":"2020-12-21T18:57:10","modified_gmt":"2020-12-21T18:57:10","slug":"energy-error-hourglass-error-in-a-piston-connecting-rod-crankshaft-engine-assembly-explicit-dynamics","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/energy-error-hourglass-error-in-a-piston-connecting-rod-crankshaft-engine-assembly-explicit-dynamics\/","title":{"rendered":"Energy error\/hourglass error in a piston connecting rod crankshaft engine assembly Explicit Dynamics"},"content":{"rendered":"<div class=\"Item-Body\">\n<div class=\"Message userContent\">\n<p><p><\/p>\n<\/p>\n<p>Hello all,<\/p>\n<p>To begin with, this is not a typical hourglass\/energy error problem, so please don&#039;t tell me to search the database. I contacted my local Ansys Elite Channel Partner, but they couldn&#039;t find the cause of the problem.<\/p>\n<p>I am simulating an engine assembly. The piston, the pins and the crankshaft are rigid bodies, while the connecting rod and the bolts are flexible. I use bonded contact for the threaded connection and frictional contacts for all other contacts.<\/p>\n<p>&nbsp;<\/p>\n<p>The first problem is the hourglass energy. I am using the stiffness formulation (Flanagan-Belytschko) for hourglass damping. I tried different coefficients, but every time the hourglass damping is much larger than the internal energy.However, no hourglassing is visible.&nbsp; Mesh refinement didn&rsquo;t work, on the contrary- on a very fine grid, the hourglass energy was about 1500% of the internal energy!! The viscous formulation is not working at all. I see that the hourglassing is accumulated in the bolts and near the bolt holes. The grid is perfect, almost 100% hexahedral elements. I use mass scaling, since there are a few smaller elements. Max element mass scaling is ~10.<\/p>\n<p><\/p>\n<\/p>\n<div class=\"embedExternal embedImage\">\n<div class=\"embedExternal-content\">\n<a class=\"embedImage-link\" href=\"https:\/\/us.v-cdn.net\/6032193\/uploads\/8T4V9YTB105S\/image.png\" rel=\"nofollow noopener\" target=\"_blank\"><br \/>\n<img decoding=\"async\" class=\"embedImage-img\" src=\"https:\/\/us.v-cdn.net\/6032193\/uploads\/8T4V9YTB105S\/image.png\" alt=\"image.png\" \/><br \/>\n<\/a><\/p>\n","protected":false},"template":"","class_list":["post-50778","topic","type-topic","status-closed","hentry","topic-tag-autodyn","topic-tag-energy-error","topic-tag-explicit-dynamics","topic-tag-hourglass","topic-tag-hourglass-energy"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_old_topic_id":["23030"],"_bbp_old_topic_author_name_id":["Anonymous"],"_bbp_old_is_topic_anonymous_id":["false"],"_bbp_old_closed_status_id":["publish"],"_bbp_author_ip":["S\u001dg\u000f"],"_bbp_old_sticky_status_id":["normal"],"_bbp_likes_count":["0"],"_btv_view_count":["1341"],"_bbp_subscription":["249342"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["50778"],"_bbp_forum_id":["27814"],"_bbp_engagement":["83","240","175158"],"_bbp_voice_count":["3"],"_bbp_reply_count":["12"],"_bbp_last_reply_id":["138202"],"_bbp_last_active_id":["138202"],"_bbp_last_active_time":["2021-01-09 10:55:04"]},"test":"bobsik641"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/50778","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\/50778\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=50778"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}