黃永剛單晶塑性有限元umat子程序

1、 SUBROUTINE UMAT(stress,statev,ddsdde,sse,spd,scd,1 rpl, ddsddt, drplde, drpldt,2 stran,dstran,time,dtime,temp,dtemp,predef,dpred,cmname,3 ndi,nshr,ntens,nstatv,props,nprops,coords,drot,pnewdt,4 celent,dfgrd0,dfgrd1,noel

2、,npt,layer,kspt,kstep,kinc)c WRITE (6,*) 'c NOTE: MODIFICATIONS TO *UMAT FOR ABAQUS VERSION 5.3 (14 APR '94)c c (1) The list of variables above defining the *UMAT subroutine, c and the first (standard) bloc

3、k of variables dimensioned below, c have variable names added compared to earlier ABAQUS versions. cc (2) The statement: include 'aba_param.inc' must be added as below.cc (3) As of version 5.3, ABAQUS files

4、use double precision only.c The file aba_param.inc has a line “implicit real*8“ and, since c it is included in the main subroutine, it will define the variablesc there as double precision. But other subroutines still

5、 need thec definition “implicit real*8“ since there may be variables that arec not passed to them through the list or common block.cc (4) This is current as of version 5.6 of ABAQUS.cc (5) Note added by J. W. Kysar

6、 (4 November 1997). This UMAT has beenc modified to keep track of the cumulative shear strain in each c individual slip system. This information is needed to correct anc error in the implementation of the Bassani

7、 and Wu hardening law.c Any line of code which has been added or modified is precededc immediately by a line beginning CFIXA and succeeded by a line c beginning CFIXB. Any comment line added or modified will begin

8、 c with CFIX.cc The hardening law by Bassani and Wu was implemented incorrectly.c This law is a function of both hyperbolic secant squared and hyperbolicc tangent. However, the arguments of sech and tanh are rel

9、ated to the *total*c slip on individual slip systems. Formerly, the UMAT implemented thisc hardening law by using the *current* slip on each slip system. Therein c lay the problem. The UMAT did not restrict the c

10、urrent slip to be a c positive value. So when a slip with a negative sign was encountered, the c term containing tanh led to a negative hardening rate (since tanh is an c odd function).c The UMAT has been fixed

11、by adding state variables to keep track of the c *total* slip on each slip system by integrating up the absolute value C----- Variables:CC STRESS -- stresses (INPUT & OUTPUT)C Cauchy stress

12、es for finite deformationC STATEV -- solution dependent state variables (INPUT & OUTPUT)C DDSDDE -- Jacobian matrix (OUTPUT)C----- Variables passed in for information:CC STRAN -- strainsC

13、 logarithmic strain for finite deformation C (actually, integral of the symmetric part of velocityC gradient with respect to time)C DSTRAN -- increments of strainsC

14、 CMNAME -- name given in the *MATERIAL optionC NDI -- number of direct stress componentsC NSHR -- number of engineering shear stress componentsC NTENS -- NDI+NSHRC NSTATV -- number

15、of solution dependent state variables (as C defined in the *DEPVAR option)C PROPS -- material constants entered in the *USER MATERIAL C optionC NPROPS -- number of materia

16、l constantsCC----- This subroutine provides the plastic constitutive relation of C single crystals for finite element code ABAQUS. The plastic slipC of single crystal obeys the Schmid law. The program gives

17、the C choice of small deformation theory and theory of finite rotation C and finite strain.C The strain increment is composed of elastic part and plastic C part. The elastic strain increment corres

18、ponds to lattice C stretching, the plastic part is the sum over all slip systems of C plastic slip. The shear strain increment for each slip system isC assumed a function of the ratio of corresponding res

19、olved shear C stress over current strength, and of the time step. The resolvedC shear stress is the double product of stress tensor with the slipC deformation tensor (Schmid factor), and the increment of

20、current C strength is related to shear strain increments over all slip C systems through self- and latent-hardening functions.C----- The implicit integration method proposed by Peirce, Shih and C Needlema