today I have committed some changes, especially for MAT_058 (and 158) to have the possibility to define proper poisson's ratios PRCA and PRCB. They were assumed to be equal to PRBA. Althought it was possible to define PRCA and PRCB for MAT_059, they were assumed to be PRBA as well, as MAT_059 uses the same initialization routine. So with the changes in r85537, the results for older decks with MAT_059 and shells may differ, especially when looking at the internal energies. For the solid routines I would not expect any changes. As for MAT_058 and MAT_158, the results for older decks should not change but it may appear a warning message that the utilized poisson's ratio may be illegal. Best regards, Stefan 11/21/13 _____________________________________________________ Information on mat_59 is hard to come by. What I've gathered is very piecemeal. With the recent LS-DYNA addition of the xxxx=SPH option for *mat_059 > (*mat_composite_failure_xxxx_model), I might suggest reading the > following paper. Dr. Azevedo used a work around in representing the > SPH composite material behavior; he may, however, be using this new > feature in his follow on work. > > Azevedo, R.L., and Alves, M., "Numerical Simulation of Soft-Body > Impact on GFRP Laminate Composites: Mixed SPH-FE and Pure SPH", > Mechanics of Solids in Brazil 2009, Brazilian Society of Mechanical > Sciences and Engineering, 2009. > > http://www.abcm.org.br/symposiumseries/SSSM_Vol2/Contents/SSSM_02.pdf ____________________________________________________________________ The paper "Crashworthiness Analysis with Enhanced Composite Material Models in LS-DYNA - Merits and Limits", Karl Schweizerhof et al, 5th International LS-DYNA User's Conference (1998) (located in http://ftp.lstc.com/anonymous/outgoing/jday/composites/crash_composites_paper.pdf) provides some insight into several composite material models in LS-DYNA, including mat_54, mat_58, and mat_59. There are some typos in the paper, summarized as follows: 1. There are two negatives in the exponent in equation 5. Only one is needed as the exponent is supposed to be negative. Also, the condition on beta should be beta > 1 and not b > 0. 2. The multiplier at the tail end of Eq. 5 should be written as (epsi * Ei), not epsi/Ei. 3. Figure 2: Caption should read "..., (b) DFAILT = 0.03" mat_compos.ppt: A powerpoint presentation giving an overview of composite modeling in LS-DYNA. _____________________________________________________________ SF is used to calculate alpha in Eqns. 6 and 8 of the Schweizerhof paper. alpha = 1 - SF The parameter alpha is used to limit the tensile part of the failure surface after first tensile failure. sig1t = XT * alpha sig2t = YT * alpha (sig2c in Eq. 8 of paper is a typo) Consider a mat59 shell compressed in local-x and then returned to its original length: Compressive yield at sigx = -XC * SR After initial tensile failure at sigx = (XT * SR), the tensile yield stress drops to (XT * SR) * (1 - SF) The sign of the shear strength determines whether 59a or 59b failure theory is used. SC > 0 triggers the faceted failure surface (59a) SC < 0 triggers the ellipsoidal failure surface (59b) ___________________________________________ Failure means in Mat 59 that we have an elastic limit (not rupture), thus plasticity starts. If the "failure " occurred the first time then for the next time the alpha is taken. But still it is elastoplastic, however, with a reduced yield strength. Regards Karl ________________________________________________________ Dear Jim, concerning Mat59 I fully agree with your statements. ALP makes no sense here and is coming from copying the description from Mat54. I do not know whether SOFT (the crashfront model) is implemented here. Thus Klaus should have a short look. Regards Karl 1.04.2004 , you wrote: ALP appears to be unused in v. 970 mat_059. FBRT and SR cumulatively scale the tensile fiber strength. SR scales all strength values. SC is the unscaled shear strength (sign determines type of failure surface used). SOFT ... I'm not sure. Karl or Klaus may wish to elaborate or correct any misstatements on my part. Regards, Jim _________________________________________________________________ For mat_059 shells, the history variables... "plastic strain" = ef 1 = ec 2 = em 3 = ed 6 = efail 7 = dam ... do not appear to be updated as they are in mat_054/055. In other words, you can't monitor failure in various modes using these history variables. _____________________________________________________ For additional information pertaining specifically to mat_059 solids, see the text file "mat59_solids".