Question about implementing simple zener model in UMAT

[Peeyush]

I have a 1 D equation for zener model which I want to model in abaqus using UMAT. Comes from an incomplete example in abaqus

sigma=stress
epsilon=strain
sigmadot, epsilondot=derivatives wrt time
mu= damping element
E1= spring 1
E2= spring 2
deltasigma= increment in stress
deltaepsilon = increment in strain
delta_t=increment in time

k1=mu/(E1+E2)
k2=mu/(1+(E1/E2))
k3=(1/((1/E1)+(1/E2))

sigma+(k1)*sigmadot=k2*epsilondot+k3*epsilon

ABAQUS for eg uses a central difference operator, can come up with

deltasigma*(k1+delta_t/2)=deltaepsilon*(k2+k2*delta_t/2)+ (k3*epsilon_t-sigma_t)*delta_t

the question is

How do i make a plane strain model out of this? what do I specify for elasticity matrix

Please help .

Peeyush

[Jorgen]

Your equations are hard to follow without better explanations.

In general, a plane strain UMAT is implemented basically the same as a full 3D implementation. The only difference is the number of strain components. The stiffness tensor is the same in plane strain as is full 3D.

- Jorgen