Learning Forum

[longt8]

Hello,

I want to use a bilinear cohesive model, there is only a mixed model cohesive model MAT138. I only have G_IC, T , UND and E_N from the experiment, how can I fill in G_IIC, S, and E_T, UNT in the material card?

CH.png

[Ram Gopisetti]

in Bilinear cohsive law it consider the mixed mode seperation , this was alos dicussed in the vol - II of the lsdyna so MAT _189 (softening) or MAT_138 for linear type is correct to impliment if you want to use bilinear cohesive model, DCB has to be performed to find out the parameters,
Cheers, Ram

[longt8]

Thank you for your response!
I am working to mixed model now, but I get another question:

I have a material with
Stiffness (EN or ET) = 1.210+e013
Energy release rate(G)=5000
Ultimate Peak Tracking (T or S) = 3.123+e006
Ultimate displacement (UND or UTD) = 9.787e-004

L = T/E = (3.123+e006)/(1.210+e013) = 2.5810e-07
Thus L is smaller than u with u/L = (9.787e-004)/(2.5810e-07) = 3.7919e+03, but the solver still shows u/L is greater than 1

Could you let me what is the reason?

Thank you so much!

Teng

[longt8]

Hello I finally figure out we should give XMU based on the equation below and it works:

And UND and UNT are for error check or double-check in the material card:

[Andreas Koutras]

Hello @longteng09 Please set XMU not equal to zero, such as XMU=1.0. Also note that if the peak strength and energy release are specified, the peak displacement will be calculated as UND = 2*Gc/T and the value of UND in the input will be ignored.

[longt8]

Thank you so much for your reply!
For this reason, UND is optional input or it is ok to put zeros as default since the peak displacement will be calculated ad UND = 2*Gc/T?