{"id":390119,"date":"2024-10-16T20:19:49","date_gmt":"2024-10-16T20:19:49","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/390119\/"},"modified":"2024-10-16T20:19:49","modified_gmt":"2024-10-16T20:19:49","slug":"390119","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/390119\/","title":{"rendered":"Reply To: Negative eroding contact energy in impact testing"},"content":{"rendered":"<p>&lt;p&gt;Hello,&lt;\/p&gt;&lt;p&gt;Which value did you use for SLSFAC? By increasing SLSFAC (contact stiffness), the timestep will change as well. Here is more information from the LS-DYNA User Manual Vol I:&lt;\/p&gt;&lt;p&gt;&#8221;<strong>Time Step Scale Factor TSSFAC.<\/strong> During the solution we loop through the&lt;br&gt;elements and determine a new time step size by taking the minimum value over&lt;br&gt;all elements:&lt;br&gt;&Delta;W +T = TSSFAC &times; min{&Delta;WT, &Delta;W,, . . . , &Delta;W&agrave;}&lt;br&gt;where N is the number of elements. The time step size roughly corresponds to&lt;br&gt;the transient time of an acoustic wave through an element using the shortest&lt;br&gt;characteristic distance. For stability reasons the scale factor TSSFAC should be&lt;br&gt;set to a value less than 1.0. The default value of TSSFAC is as follows:&lt;br&gt;a) If contacts are present, and SLSFAC is specified in CONTROL_CONTACT,&lt;br&gt;then&lt;br&gt;TSSFAC = }&lt;br&gt;0.333 for SLSFAC &ge; 9.&lt;br&gt;0.667 for 1.&le; SLSFAC &lt; 9.&#8221;&lt;\/p&gt;&lt;p&gt;So, if you used SLSFAC between 1 and 9, then TSSFAC will be equal to 0.667. So, this would have a similar effect to setting TSSFAC=0.66. Now, maybe the contact stiffness has an impact here.&lt;\/p&gt;&lt;p&gt;I would try with SLSFAC set as before and set TSSFAC=0.667 and see&nbsp; if it also fix the problem. If not, then the contact stiffness plays a role.&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;I don&#8217;t understand what you mean by red and green lines in the RCFORC. Could you post the graph?&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;Reno.&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-390119","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"acf":[],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies\/390119","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/reply"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies\/390119\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=390119"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}