The progress is as following till now:
1. The problem may come from slave and master element/node penetration. Reason:
1.1 The dimensions of the model are too small (least possibility);
1.2 The thickness of the original blank is too small;
1.3 Mass of the final product is increased a lot with mass scaling;
1.4 Maximum penetration depth allowed is too big;
2. Methods to reduce the penetration but not to solve the problem:
2.1 Make DT2MS = 0;
2.2 SSF = 1; MSF = 1; make SLSFAC = 0.1 (or bigger enough without dynamic instability);
2.3 Make XPENE smaller than default value 4.0, but can not be too small. (I am not sure).
etc.
3. Conclusion:
3.1 LS-Dyna can not really solve this kind of problem, especially when the thickness is too small, and it has limitations.
3.2 Try to use other software. I am going to try MSC.Marc (preferred) or PAM STAMP for sheet metal forming.
"有的地方变薄，有的地方变厚，变薄太厉害就会拉裂，" You are right. "变厚太厉害就会起皱" I think it is only possible when the pressure pad (binder) force is not big enough and the wrinkle will happen only at the locations of the blank
between die and binder and can not happen between die and punch with good-designed production case since the
clearance between punch and die will iron the material. "模具间隙一般为1.1t mm,t是板材厚度。" This is the CONTACT
GAP set-up in Dynaform between tools and blank (e.g. contact gap between punch and blank), which can prevent initial
penetration. And normally, we can offset the tool from another tool (e.g. from punch to die) if and only if the geometry of
punch and die is the same. Unfortunately, this is not my case.
"dynaform里面可以定义板材和模具之间的穿透值", for shell element, the Max Distance of penetration is defined as
XPENE*(thickness of shell element) when SHLTHK=1. but I am not quite sure how the contact algorithm works. (如果没有穿透的话，接触计算就会报错) Could you please explain a little more?
"允许板材变厚比模具间隙大", then neither the final results of thickness can not be trusted, nor the stress and strain
because it does not follow the reality.
Thanks a lot!
Yes, you are right. We could set up the parameters in Dynaform directly. In Dynaform, "Tools" ---> "Define Tools", we
could select select the particular tool and specify the contact type, for my case, "FORMING_ONE_WAY_SURFACE_TO_SURFACE". Then, under "Define Contact Parameters", there are several parameters could be specified. "SCALE FACTOR SLAVE" means SFS in Dyna; "SCALE FACTOR MASTER" means SFM; "SLAVE SURF. THICKNESS" means SST; and "MASTER SURF. THICKNESS" means MST. I am still trying. There are too many variables.
You could download all the manuals from the "Tutorials" under www.feainformation.com if needed.
发表于 2005-9-15 23:04:26
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发表于 2005-10-27 21:42:10
