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[FAQ]

Yes, it is true that user can convert the Prony relaxation model used in Mechanical Implicit to the Viscoelastic material model used in Explicit Dynamics and Autodyn. Three parameters: instantaneous shear modulus G0, long term shear modulus G_inf, and the decay constant Beta, are used in the Viscoelastic model in Explicit Dynamics and Autodyn. In Prony Shear Relaxation model, the shear modulus and the relaxation time are known. Thus, the shear modulus with the longest relaxation time in the Prony model can be treated as the Long Term Shear Modulus in the Autodyn Viscoelastic model. The shear modulus with the shortest relaxation time in the Prony model can be treated as the Instantaneous Shear Modulus in the Autodyn Viscoelastic model. The decay constant can be found from the Instantaneous Shear Modulus and the Long Term Shear Modulus using the following equation G_inf = (G0-Ginf)*e^(-Beta*T) where T is the time difference between the longest and shortest relaxation time. Be aware that they are two different material models. So they may not predict exactly the same stress and strain values at the given relaxation time.