{"id":35469,"date":"2019-05-20T21:12:41","date_gmt":"2019-05-20T21:12:41","guid":{"rendered":"\/forum\/forums\/topic\/mesh-refinement-convergence-and-singularities\/"},"modified":"2019-05-20T21:12:41","modified_gmt":"2019-05-20T21:12:41","slug":"mesh-refinement-convergence-and-singularities","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/mesh-refinement-convergence-and-singularities\/","title":{"rendered":"Mesh refinement, convergence and singularities"},"content":{"rendered":"

Hi again Peter,<\/p>\n

<\/p>\n

I regret having to come back to this issue but my last post<\/a> about it did not finish fully convincing me:<\/p>\n

<\/p>\n

OK, once the plasticity model was introduced stresses (whether they are real coming from stress concentrators or fictitious due to geometric singularities) stop growing up above the yield limit and instead the area around them plasticizes redistributing stress to nearby zones. Then, the failure criterion is not “max. stress < yield” anymore but the new deciding rule becomes “total strain < elongation at break”. So far so good: in my submodel this comparison resulted in a large safety margin (<\/span>0,83% << 23%) so, leaving aside the annoying issue with the cut-boundary misalignment, that closed and solved the problem. Right? Well, here is when my comes again:<\/span><\/p>\n

<\/p>\n

I realized the max. total strain was occurring in the inner face of the tubes; in fact, on the hard edge where the two inner surfaces meet (I had rounded the outer edges but indeed forgot the one inside):<\/span><\/span><\/p>\n

<\/p>\n

\"\"\"\"<\/span><\/span><\/p>\n

<\/p>\n

so I thought “what if I refine the mesh in this area to try a mesh-independence convergence there?”. <\/span><\/span><\/span>And so I did it… but first, in order to avoid the hard edge foreseeable singularity, I rounded the inner edge too:<\/span><\/span><\/p>\n

<\/p>\n

\"\"<\/span><\/span><\/p>\n

<\/p>\n

To my surprise with the mesh refinements it came the result escalation:<\/span><\/span><\/p>\n

<\/p>\n

\"\"<\/p>\n

<\/p>\n

\"\"<\/p>\n

<\/p>\n

so here I am again with the “same question”: even though the obtained values are still quite below the limit (2.49% is still far from 23%) and since the hard-edge singularity should be discarded, how can I be sure the strain will not continue growing with further refinements? (I have not run another refinement step because with a nonlinear setup running times already got long enough…), does it make the same sense to run a mesh-independence convergence study for plastic strains as it did for stresses? and, which value is then to be considered accurate\/useful enough? <\/p>\n","protected":false},"template":"","class_list":["post-35469","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_old_topic_id":["7641"],"_bbp_old_topic_author_name_id":["Anonymous"],"_bbp_old_is_topic_anonymous_id":["false"],"_bbp_old_closed_status_id":["publish"],"_bbp_author_ip":[null],"_bbp_old_sticky_status_id":["normal"],"_bbp_likes_count":["0","0"],"_btv_view_count":["1581"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["35469"],"_bbp_forum_id":["27793"],"_bbp_engagement":["240","163675"],"_bbp_voice_count":["2"],"_bbp_reply_count":["7"],"_bbp_last_reply_id":["86053"],"_bbp_last_active_id":["86053"],"_bbp_last_active_time":["2019-05-27 07:23:44"]},"test":"timescavenger"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/35469","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\/35469\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=35469"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}