{"id":379365,"date":"2024-08-19T15:08:44","date_gmt":"2024-08-19T15:08:44","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/influence-of-initial-stresses-on-linear-buckling-analyses\/"},"modified":"2024-08-19T15:08:44","modified_gmt":"2024-08-19T15:08:44","slug":"influence-of-initial-stresses-on-linear-buckling-analyses","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/influence-of-initial-stresses-on-linear-buckling-analyses\/","title":{"rendered":"Influence of initial stresses on Linear Buckling Analyses"},"content":{"rendered":"<p>Comparing the results of my (implicit) nonlinear transient buckling analyses of a sandwich panel using the Arc Length Method with a simple Linear Eigenvalue buckling analysis (also implicit), I observe a difference of only 2 percent in the calculated maximum buckling load. According to the literature, there should be a much larger difference due to the linearity, and the calculated buckling loads of the Linear Eigenvalue buckling analysis should be significantly higher. Therefore, I am now investigating why the results are so &#8220;lucky,&#8221; but I don&rsquo;t fully understand the simplifications made in this method and the influence of the base simulation, which is nonlinear in my case. From what I understand, the base step is used to set up the stiffness matrix that corresponds to the stresses from the reference load. Is it possible that by using initial stresses from the preforming step, the calculated stiffness matrix describes a stiffer behavior because the initial stresses add to the total stresses caused by the external force? Since initial stresses are not considered in the linear eigenvalue buckling analysis, the stiffness matrix is seen as a reaction only to the reference load, and therefore the buckling load is calculated to be smaller. Is this assumption correct ? This would also explain why using a smaller reference load is causing the calculated buckling load to be even smaller than the exact buckling load, because the proportion of the initial and force related stresses is bigger.&nbsp;<\/p>\n","protected":false},"template":"","class_list":["post-379365","topic","type-topic","status-publish","hentry","topic-tag-eigenvalue-buckling","topic-tag-implicit","topic-tag-ls-dyna","topic-tag-theory"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Comparing the results of my (implicit) nonlinear transient buckling analyses of a sandwich panel using the Arc Length Method with a simple Linear Eigenvalue buckling analysis (also implicit), I observe a difference of only 2 percent in the calculated maximum buckling load. According to the literature, there should be a much larger difference due to\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" href=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/influence-of-initial-stresses-on-linear-buckling-analyses\/\" \/>\n\t<meta name=\"generator\" content=\"All in One SEO (AIOSEO) 4.9.10\" \/>\n\t\t<meta property=\"og:locale\" content=\"en_US\" \/>\n\t\t<meta property=\"og:site_name\" content=\"Ansys Learning Forum | Ansys Innovation Space\" \/>\n\t\t<meta property=\"og:type\" content=\"article\" \/>\n\t\t<meta property=\"og:title\" content=\"Influence of initial stresses on Linear Buckling Analyses | Ansys Learning Forum\" \/>\n\t\t<meta property=\"og:description\" content=\"Comparing the results of my (implicit) nonlinear transient buckling analyses of a sandwich panel using the Arc Length Method with a simple Linear Eigenvalue buckling analysis (also implicit), I observe a difference of only 2 percent in the calculated maximum buckling load. 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