{"id":186768,"date":"2021-07-29T04:59:47","date_gmt":"2021-07-29T04:59:47","guid":{"rendered":"\/forum\/forums\/reply\/186768\/"},"modified":"2021-07-29T04:59:47","modified_gmt":"2021-07-29T04:59:47","slug":"186768","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/186768\/","title":{"rendered":"Reply To: How to Create a Stiffness Matrix in APDL"},"content":{"rendered":"<p>Dear Mr. Erik:<br \/>\nMany, many thanks. Yes, I made some progress. If any Support Engineer could answer my questions or clarify my understanding that will be highly appreciated. These are my understanding:<br \/>\nThe stiffness matrix, provided by the *dmat command, is associated with the <strong>DOFs <\/strong>which are <strong>NOT constrained<\/strong>. For example, I made my FE model using Truss Element (Link180). I used only two nodes, Node # 1 and Node # 2. So, I have only <strong>one <\/strong>element, which is aligned along the global x-direction. I applied force also along x-direction. If I consider only <strong>1 DOF<\/strong> (Ux) per node, then the size of global stiffness (K) matrix will be a (2&#215;2) matrix. However, <strong>Node # 1<\/strong> is <strong>fixed<\/strong>. Hence, the stiffness matrix, provided by the *dmat command,  is <strong>NOT <\/strong>including the components under the &#8220;Row # 1 and Column # 1&#8221;. It is providing the stiffness components ONLY under the &#8220;Row # 2 and Column # 2&#8221;. So, it becomes a (1 x 1) matrix. <br \/>\nThen, I repeated the same simulation using <strong>4 nodes<\/strong>. So, I have 3 elements. Each element is aligned along global x-direction. If I consider only <strong>1 DOF<\/strong> (Ux) per node, then the size of global stiffness (K) matrix will be a (4 x 4) matrix. However, <strong>Node # 1<\/strong> is <strong>fixed<\/strong>. Hence, the stiffness matrix, provided by the *dmat command, is <strong>NOT <\/strong>including the components under the &#8220;Row # 1 and Column # 1&#8221;. It is providing the stiffness components under the &#8220;Row # 2 to 4 and Column # 2 to 4&#8221;. So, it becomes a (3 x 3) matrix. And, those components are matching with the stiffness matrix provided by MATLAB. Here is the image of stiffness matrix provided by *dmat command. <br \/>\n<img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/forum-uploads\/031\/C26OGKDWI3A3.png\" width=\"941\" height=\"276\" \/>If any <strong>Support Engineer<\/strong> could clarify my understanding that will be highly appreciated. Thanks<br \/>\nAwlad.<\/p>\n","protected":false},"template":"","class_list":["post-186768","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Dear Mr. Erik: Many, many thanks. Yes, I made some progress. If any Support Engineer could answer my questions or clarify my understanding that will be highly appreciated. These are my understanding: The stiffness matrix, provided by the *dmat command, is associated with the DOFs which are NOT constrained. For example, I made my FE\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" href=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/186768\/\" \/>\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=\"Reply To: How to Create a Stiffness Matrix in APDL | Ansys Learning Forum\" \/>\n\t\t<meta property=\"og:description\" content=\"Dear Mr. Erik: Many, many thanks. Yes, I made some progress. If any Support Engineer could answer my questions or clarify my understanding that will be highly appreciated. These are my understanding: The stiffness matrix, provided by the *dmat command, is associated with the DOFs which are NOT constrained. 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If any Support Engineer could answer my questions or clarify my understanding that will be highly appreciated. These are my understanding: The stiffness matrix, provided by the *dmat command, is associated with the DOFs which are NOT constrained. 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Yes, I made some progress. If any Support Engineer could answer my questions or clarify my understanding that will be highly appreciated. These are my understanding: The stiffness matrix, provided by the *dmat command, is associated with the DOFs which are NOT constrained. 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If any Support Engineer could answer my questions or clarify my understanding that will be highly appreciated. These are my understanding: The stiffness matrix, provided by the *dmat command, is associated with the DOFs which are NOT constrained. 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For example, I made my FE","inLanguage":"en-US","isPartOf":{"@id":"https:\/\/innovationspace.ansys.com\/forum\/#website"},"breadcrumb":{"@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/186768\/#breadcrumblist"},"datePublished":"2021-07-29T04:59:47+00:00","dateModified":"2021-07-29T04:59:47+00:00"},{"@type":"WebSite","@id":"https:\/\/innovationspace.ansys.com\/forum\/#website","url":"https:\/\/innovationspace.ansys.com\/forum\/","name":"Ansys Learning Forum","description":"Ansys Innovation Space","inLanguage":"en-US","publisher":{"@id":"https:\/\/innovationspace.ansys.com\/forum\/#organization"}}]},"og:locale":"en_US","og:site_name":"Ansys Learning Forum | Ansys Innovation Space","og:type":"article","og:title":"Reply To: How to Create a Stiffness Matrix in APDL | Ansys Learning Forum","og:description":"Dear Mr. Erik: Many, many thanks. Yes, I made some progress. 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