Update: I re-ran both orientations described above in SW Premium 2017 SP3.0 and examined the corresponding .OUT files. I'm not sure how to interpret this information, but here are some bits that might be relevant:
Vertical (gravity parallel to springs -- the case that failed to reach equilibrium):
Last "CONTACT ITERATION NUMBER" = 75 (Is this the upper limit?)
"TOTAL NUMBER OF ACTIVE CONTACT ELEMENT(S) = 23465"
"TOTAL STRAIN ENERGY. . . . . . . . . . . = 0.158073E+00"
" Ave. Percentage Error (APE) = 0.183945E+02"
"S O L U T I O N T I M E L O G... ( 2:36:32)"
Horizontal (gravity perpendicular to springs -- the case that successfully reached equilibrium):
Last "CONTACT ITERATION NUMBER" = 50
"TOTAL NUMBER OF ACTIVE CONTACT ELEMENT(S) = 22447" (Why smaller?)
"TOTAL STRAIN ENERGY. . . . . . . . . . . = 0.335303E-03" (Much smaller!)
"Ave. Percentage Error (APE) = 0.937037E+02"
"S O L U T I O N T I M E L O G... ( 1:46:25)"
Does any of this help explain why equilibrium is not obtained? -- John Willett
I have the same problem. I have a problem with loads and gravity which solves, but when I add a temperature load I get the same error message as you. Hopefully, someone will respond with a clue as to what to look for.
Lesley -- Thanks! Maybe mark the "I have the same question" box? Perhaps that will catch somebody's attention... -- John Willett
Second Update: Questions about Contact Sets -- Since this error appears to be caused by equilibrium failure during the contact-analysis phase of the simulation, I'm wondering if I made wrong choices in setting up the no-penetration contact sets in this study. I'm trying to follow the somewhat confusing recommendations on setting up contact sets found in FAQID__x281.pdf, for example:
1) "Position your parts so as to establish initial contact..." -- All of my no-penetration contact sets are in initial contact on part of their paired faces, so this should be satisfied. After meshing, however, I suppose that interference might develop between opposing surfaces, depending on just how the mesher approximates these surfaces. Might this be an issue? Is this a reason to use node-to-surface conditions instead of the normally-preferred surface-to-surface conditions?
(By the way, I've always set the "Gap (clearance)" option to "Ignore clearances only if gap is less than 0." This would seem to minimize the contact areas that the program has to consider, but is it a bad idea for other reasons?)
2) "You typically shouldn't create many No Penetration contact sets with only one Source and one Target.
Instead, you should create fewer No Penetration contact sets. In each of them, include all the faces that make physical sense to group together. This will be the case for instance for contiguous faces on the same part. Also, if a part A touches simultaneously parts B and C [I think parts A and B should be reversed here for the illustration to make sense], then is probably makes sense to define a single contact set for it." -- This can often result in uncertainty about which source face is to be compared with which target face, which would seem to make unnecessary work for the program. Is this a potential issue? (My initial inclination was to specify individual pairs of source and target, but the advice is clearly against that. Why?)
3) "Target face(s) should be flatter, larger than Source entities. Target face(s) can be meshed coarser than
Source entities." -- This recommendation often conflicts with (2). In such cases which should take precedence? In general, when is it important to specify individual pairs of source and target instead of grouping them together as recommended in (2)?
In general do people have favored ways of grouping contact sets to avoid this kind of equilibrium failure? -- John Willett
Third Update: I eventually found a not-very-satisfactory work-around to this "Equilibrium is not achieved" error by eliminating several of the no-penetration contact sets (by eliminating some of the sliding parts while not eliminating any of the possible sliding motions). The fundamental questions still remain, however. -- John Willett