{"id":283669,"date":"2023-05-12T13:35:51","date_gmt":"2023-05-12T13:35:51","guid":{"rendered":"\/forum\/forums\/topic\/calculate-by-hand-frequency-responses-including-residual-vectors\/"},"modified":"2023-05-12T13:35:51","modified_gmt":"2023-05-12T13:35:51","slug":"calculate-by-hand-frequency-responses-including-residual-vectors","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/calculate-by-hand-frequency-responses-including-residual-vectors\/","title":{"rendered":"Calculate by hand frequency responses including residual vectors"},"content":{"rendered":"

Hello, <\/p>\n

I performed a modal analysis and exported in a text file X,Y,Z,RX,RY,RZ displacement (in that case, mode shape) of some interesting nodes: here an example<\/p>\n

<\/p>\n

Line : node (6 nodes here)<\/p>\n

column : mode (10 modes)<\/p>\n

Then, I performed a harmonic analysis with the MSUP method (mode-superposition) linked with the previous modal analysis, and write the MCF file related to it (HROPT,MSUP, , ,YES).<\/p>\n

I know that the idea of the MSUP method is to calculate the displacement like this :<\/p>\n

<\/p>\n

That is to say, express the displacement vector in the modal basis formed with the mode shapes calculated during the eigenproblem in the previous modal analysis.<\/p>\n

Then, i want to take into account the residual vector, which is the highest modes contribution. When i enable including the residual mode (RESVEC, ON), or the harmonic analysis settings , the MCF file contains one more mode (last column) that is the residual mode :<\/p>\n

<\/p>\n

In my modal analysis, I only chose the 10 first modes, and the 11th one refers to the residual mode.<\/p>\n

Now, I have all i need to calculate the frequency response.<\/p>\n

I guess I just have to make “sum(phi_i * y_i) + residual vector” at each frequency excitation to calculate that, but it doesn’t give me the good result. In fact, i’m comparing result to ANSYS and it doesnt correspond. Here is the comparison response at one particular node :<\/p>\n

<\/p>\n

Blue : “by hand” calculation in MATLAB with MSUP method, with <\/strong>residual mode (RM)<\/p>\n

Red : “by hand” calculation in MATLAB with MSUP method, without <\/strong>residual mode<\/p>\n

Yellow : Ansys frequency response with MSUP method, without <\/strong>residual mode<\/p>\n

Purple : Ansys frequency response with MSUP method, with <\/strong>residual mode<\/p>\n

The yellow and red curves are corresponding, which is normal because i just made by hand the same calculation than ANSYS.<\/p>\n

Yet, the red and purple curves does not correspond, and it should. Is the operation “sum(phi_i * y_i) + residual vector” wrong ?<\/p>\n

To resume : I obtain the good results when i’m performing the MSUP method whithout RM, but not the good results in MSUP method with RM.<\/p>\n

Thanks,<\/p>\n

Adrien<\/p>\n","protected":false},"template":"","class_list":["post-283669","topic","type-topic","status-closed","hentry","topic-tag-Modal_Analysis-1","topic-tag-eigenmode","topic-tag-eigensolver-analysis-2","topic-tag-frequency-response","topic-tag-harmonic","topic-tag-harmonicmodalanalysis-1","topic-tag-modal","topic-tag-modal-analysis","topic-tag-mode-superposition","topic-tag-residual"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["284164","88","20905"],"_bbp_author_ip":["23.39.172.6"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_bbp_likes_count":["1"],"_btv_view_count":["1721"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["283669"],"_bbp_forum_id":["27791"],"_bbp_engagement":["88","20905","284164"],"_bbp_voice_count":["3"],"_bbp_reply_count":["7"],"_bbp_last_reply_id":["284525"],"_bbp_last_active_id":["284525"],"_bbp_last_active_time":["2023-05-17 17:23:13"]},"test":"adrien-vetsafrangroup-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/283669","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\/283669\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=283669"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}