{"id":458096,"date":"2026-05-13T15:39:58","date_gmt":"2026-05-13T15:39:58","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/tangential-stiffness-in-hertz-mindlin\/"},"modified":"2026-05-13T15:39:58","modified_gmt":"2026-05-13T15:39:58","slug":"tangential-stiffness-in-hertz-mindlin","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/tangential-stiffness-in-hertz-mindlin\/","title":{"rendered":"Tangential stiffness in Hertz-Mindlin?"},"content":{"rendered":"<p>&lt;p&gt;Hello, I am trying to understand how tangential stiffness (K_tau) is calculated for Type C rolling in Eqn (2-33) in the Rocky 2025 R1 technical manual when Hertz and Mindlin-Deresiewicz are chosen.&lt;\/p&gt;&lt;p&gt;In the linear spring Coulomb limit model, a tangential stiffness ratio is user-defined for Eqn (2-19) to calculate tangential stiffness. For Hertz, it seems that the ratio remains at the default of 1 in Rocky&#8217;s SDK. Is that true?&lt;\/p&gt;&lt;p&gt;Looking at the SDK in &#8220;&#8230;Rocky\\Modules\\sdk\\include\\rocky20\\device\\device_contact_model_functions.hpp&#8221; for the function calculate_tangential_stiffness(), kn is calculated so that it corresponds to K_H,hat in Eqn (2-13). Then the tangential stiffness is calculated as follows:&lt;\/p&gt;&lt;div&gt;&lt;div&gt;kt = 1.5 * (mat_interaction-&gt;kt_kn) * kn;&lt;\/div&gt;&lt;div&gt;&nbsp;&lt;\/div&gt;&lt;div&gt;Is the factor of 1.5 from taking the derivative of the Hertzian force to get dF\/ds = 3\/2 * K_H,hat * sqrt(s_n) ?&lt;\/div&gt;&lt;\/div&gt;<\/p>\n","protected":false},"template":"","class_list":["post-458096","topic","type-topic","status-publish","hentry","topic-tag-rocky-dem-1"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27792"],"_bbp_topic_id":["458096"],"_bbp_author_ip":["18.10.74.213"],"_bbp_last_reply_id":["458462"],"_bbp_last_active_id":["458462"],"_bbp_last_active_time":["2026-05-19 15:31:58"],"_bbp_reply_count":["1"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["21912","642030"],"_btv_view_count":["72"],"_bbp_topic_status":["unanswered"],"_bbp_subscription":["642030"]},"test":"seijiengmit-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/458096","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\/458096\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=458096"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}