{"id":162023,"date":"2023-01-25T07:34:06","date_gmt":"2023-01-25T07:34:06","guid":{"rendered":"\/knowledge\/forums\/topic\/how-does-dc-in-contact-influence-the-way-the-friction-coefficient-transitions-between-static-and-dynamic-values\/"},"modified":"2023-07-31T12:36:17","modified_gmt":"2023-07-31T12:36:17","slug":"how-does-dc-in-contact-influence-the-way-the-friction-coefficient-transitions-between-static-and-dynamic-values","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/how-does-dc-in-contact-influence-the-way-the-friction-coefficient-transitions-between-static-and-dynamic-values\/","title":{"rendered":"How does DC in *CONTACT influence the way the friction coefficient transitions between static and dynamic values?"},"content":{"rendered":"<p>Synopsis:  The dynamic friction coefficient has no effect unless the decay coefficient DC is also defined.   DC serves to smoothly transition from FS to FD over a range of velocities.   If DC=0, your net friction coefficient will simply be FS.  DC governs the transition from the static friction coefficient to the dynamic friction coefficient, as a function of relative velocity.  As points of reference, if &#8230;  DC*|Vrel| = 0.7, then the friction coefficient is halfway between FS and FD DC*|Vrel| = 4,  then the friction coefficient is essentially equal to FD.  Full explanation:  VREL is the relative velocity of the contacting bodies at the contact point.  It is computed by LS-DYNA and has units of velocity.  In order for the exponent to be dimensionless, the parameter DC also has units &#8211; the inverse of velocity.  Contact interaction can involve sticking (when VREL=0) or sliding (when VREL is non-zero).  When this interaction is treated numerically with a Coulomb-like friction law we must be able to smoothly transition between the static and dynamic friction coefficients &#8211; the exponential involving DC and VREL accommodates this.  Please look at the relation for MU and note that it yields FS when VREL=0 &#8211; this correctly corresponds to the sticking case.  Now, when DC*abs(VREL) reaches a value of about 4.0 the exponential drives the second term down so that MU is within just a couple percent of FD &#8211; this corresponds to sliding.   When DC*abs(VREL) is between these values we are in the transition state and MU is a combination of FS and FD.  There is no &#8220;correct&#8221; value for DC; its value is the responsibility of the analyst, who must ask himself &#8220;above what relative velocity do I consider something to be sliding?&#8221;.   Using this critical value of VREL the analyst then selects a value of DC, using rule of thumb stated above, such that, DC*abs(VREL) = 4.0.  In this way, when VREL attains the critical value we have MU nearly equal to FD.<\/p>\n","protected":false},"template":"","class_list":["post-162023","topic","type-topic","status-publish","hentry","topic-tag-ls-dyna","topic-tag-ls-dyna-suite","topic-tag-r12","topic-tag-structural-mechanics"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_wp_page_template":["default"],"_bbp_forum_id":["27789"],"_bbp_last_active_time":["1-24-2023  20:20:00"],"_bbp_author_ip":["23.56.168.180"],"_btv_view_count":["1963"],"siebel_km_number":["2062901"],"product_version":["R12"],"km_published_date":["2020-06-16T21:35:42.000Z"],"family":["Structural Mechanics"],"application_name":["LS-DYNA Suite"]},"test":"articlesansys-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/162023","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/162023\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/media?parent=162023"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}