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UMAT for linear Viscoelasticity

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Joined: 6 years ago

Hello everyone,
My ultimate aim is to write a UMAT based on Schaperys Integral equation and verify it in Abaqus. I am pretty much a newbie in UMAT. So decided to start off by working on a linear viscoelastic UMAT that of a simple Kelvin model (linear spring and dashpot in parallel). The constitutive law is known.

sigma_total = (E * epsilon) + (eta * d(epsilon)/dt)

Discretised constitutive law is of the form

sigma(t+1) = {E * epsilon(t+1)} + {eta * (del_epsilon)/del_time}

In abaqus will it suffiient to just code this as

dstress(k1) = {E * stran(k1)} + {eta * dstran(k1) / dtime}

and to find the jacobian as

ddsdde(k2,k1) = E + (eta/dtime)

I am a real newbie and I hope somebody helps me out to start with the work

Thanks for your time



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