{"id":288965,"date":"2023-06-15T15:27:01","date_gmt":"2023-06-15T15:27:01","guid":{"rendered":"\/forum\/forums\/topic\/contact-issues-with-modal-analysis-on-a-structure\/"},"modified":"2023-06-15T15:27:01","modified_gmt":"2023-06-15T15:27:01","slug":"contact-issues-with-modal-analysis-on-a-structure","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/contact-issues-with-modal-analysis-on-a-structure\/","title":{"rendered":"Contact Issues with Modal Analysis on a Structure"},"content":{"rendered":"<p>I am attempting free-free modal analysis on this structure, so no loads are applied. I am looking for frequencies in 6 modes. When I use &#8216;program controlled&#8217; formulation for all connections, the mode frequencies are way too high. I have tried using MPC for all contacts relating to the 4 highlighted rods in the design, but this led to overconstraint since the connections all share a face. Despite the overconstraint, the frequency values were in the expected range. Next I tried only using MPC for one contact per rod to eliminate the overconstraint, but this made the frequencies too high again and a warning that the max contact stiffness is too big.<\/p>\n<p>Could I use MPC for all the rod contacts and ignore the overconstraint warning, or is there another solution?<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/06\/15-06-2023-1686842269-AnsysForum1.JPG\" alt=\"\" width=\"576\" height=\"349\"><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/06\/15-06-2023-1686842303-mceclip0.jpg\"><\/p>\n<p>Case 1: All rod contacts with MPC and the according frequencies and warning popup.&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/06\/15-06-2023-1686842311-mceclip1.jpg\" width=\"547\" height=\"332\"><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/06\/15-06-2023-1686842326-mceclip2.jpg\"><\/p>\n<p>Case 2: MPC used only once per rod, according frequency results and warning popup.&nbsp;<\/p>\n<p>Overall I am looking for insight on how accuracy differs between these two cases and further solutions\/troubleshooting. Thanks in advance for your input.&nbsp;<\/p>\n","protected":false},"template":"","class_list":["post-288965","topic","type-topic","status-closed","hentry","topic-tag-Modal_Analysis-1","topic-tag-bonded-contact","topic-tag-contact-method","topic-tag-mpc-constraint","topic-tag-natural-frequency"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["2997","200"],"_bbp_author_ip":["23.217.200.46"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["2165"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["288965"],"_bbp_forum_id":["27791"],"_bbp_engagement":["200","2997"],"_bbp_voice_count":["2"],"_bbp_reply_count":["3"],"_bbp_last_reply_id":["289530"],"_bbp_last_active_id":["289530"],"_bbp_last_active_time":["2023-06-20 12:20:24"]},"test":"kaiden-bedellunh-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/288965","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\/288965\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=288965"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}