{"id":315196,"date":"2023-11-07T10:12:12","date_gmt":"2023-11-07T10:12:12","guid":{"rendered":"\/forum\/forums\/topic\/psd-reponse-lower-than-input-psd\/"},"modified":"2023-11-10T10:18:59","modified_gmt":"2023-11-10T10:18:59","slug":"psd-reponse-lower-than-input-psd","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/psd-reponse-lower-than-input-psd\/","title":{"rendered":"PSD Reponse lower than input PSD"},"content":{"rendered":"<p>I am trying to complete Random Vibration analysis of an assembly. <span style=\"font-size: 14pt\">The model contains a mixture of fixed and frictionless supports, as well as a number of displacement conditions. I have applied an input PSD (G acceleration) and probed the response at a predetermined location, giving the chart below.<\/span><\/p>\n<p><a class=\"wp-colorbox-image cboxElement\" href=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/11\/07-11-2023-1699351535-mceclip0.png\"><img loading=\"lazy\" decoding=\"async\" style=\"font-size: 14pt\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/11\/07-11-2023-1699351535-mceclip0.png\" width=\"1542\" height=\"750\"><\/a><\/p>\n<p><span style=\"font-size: 14pt\">What I&#8217;m unable to work out is why the response PSD is lower than the input, where usually these plots mirror each other up until close to the first eigenfrequency. I have probed the PSD response at the location of excitation to check whether the input PSD was applied correctly, which appeared correct.&nbsp;<\/span><\/p>\n<p><span style=\"font-size: 14pt\">What could be the cause of this apparent offset?&nbsp;<\/span><\/p>\n<p><span style=\"font-size: 14pt\">I run these analyses fairly regularly but I haven&#8217;t seen this issue before so I&#8217;m hoping someone can enlighten me.<\/span><\/p>\n","protected":false},"template":"","class_list":["post-315196","topic","type-topic","status-closed","hentry","topic-tag-mechanical","topic-tag-random-vibration","topic-tag-vibration"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["17778","88","304035","20905"],"_bbp_author_ip":["23.206.193.154"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["1297"],"_edit_lock":["1699611546:221391"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["315196"],"_bbp_forum_id":["27791"],"_bbp_engagement":["88","17778","20905","304035"],"_bbp_voice_count":["4"],"_bbp_reply_count":["7"],"_bbp_last_reply_id":["338460"],"_bbp_last_active_id":["338460"],"_bbp_last_active_time":["2023-12-13 16:40:40"]},"test":"matthew-kirbymicross-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/315196","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\/315196\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=315196"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}