{"id":365305,"date":"2024-05-03T02:24:36","date_gmt":"2024-05-03T02:24:36","guid":{"rendered":"\/forum\/forums\/topic\/a-question-about-quasi-static-loading-and-oscillating-response\/"},"modified":"2024-05-03T02:24:36","modified_gmt":"2024-05-03T02:24:36","slug":"a-question-about-quasi-static-loading-and-oscillating-response","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/a-question-about-quasi-static-loading-and-oscillating-response\/","title":{"rendered":"A question about quasi-static loading and oscillating response"},"content":{"rendered":"

Hello all,<\/p>\n

I am running a simulation using LS-Dyna with *LOAD_NODE_SET and constraining some DOF at distinct ends with *BOUNDARY_SPC_SET. Following some recommendations given on previous posts, I am using a ramp to define the curve and then use a constant value (see graph below). To check the quasi-static condition, I am using glstat and matsum to verify that the kinetic energy is below 5% of the internal energy; this is true for glstat and for matsum only one part had high kinetic energy.<\/p>\n

My question comes from checking some variables (see graph below for v-m stress of just 2 elements, whole part rigid-body motion) for which I observe this weird oscillating behavior that prevents me to obtain confident results at the end of the simulation; naturally I am expecting a line that shows results converging to a value (similar to my loading curve). <\/p>\n

Has anyone experience a similar issue like this? Is this caused by the ramp application curve… maybe it’s too fast? Or maybe it’s a lack of boundary conditions? Any idea would be greatly appreciated.<\/p>\n

<\/p>\n

Also a follow up question. I noted there’s an option for rigid-body acceleration in the history variable option: I have nonzero (still relatively small considering my time units) values for some parts. Is zero acceleration also a condition for quasi-static behavior or is the internal vs kinetic energy ratio sufficient?<\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n","protected":false},"template":"","class_list":["post-365305","topic","type-topic","status-closed","hentry","topic-tag-quasi-static-1","topic-tag-fea","topic-tag-LS-DynaSolverExplicitDynamics-1","topic-tag-mechanical","topic-tag-structural-loading"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["280671","37202","240"],"_bbp_author_ip":["23.216.133.166"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["1683"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["365305"],"_bbp_forum_id":["27814"],"_bbp_engagement":["240","37202","280671"],"_bbp_voice_count":["3"],"_bbp_reply_count":["6"],"_bbp_last_reply_id":["365941"],"_bbp_last_active_id":["365941"],"_bbp_last_active_time":["2024-05-07 20:15:03"]},"test":"andres-menattu-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/365305","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\/365305\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=365305"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}