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One Question about Mulliken Boyce Model

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I am using Mulliken-Boyce model for simulating constitutive response of PC. The model breaks down everything into alpha nd beta components, and adds the response together. The problem is that above 25 degree C, the E_beta~5MPa, and so s=0.077mu/(1-nu) ~ 0.2 MPa. With this small s, the quantity tau/(s+alpha*p) becomes greater than one, which should never happen for solution to converge.

The values I am using are quoted from his paper directly. Can anyone please let me know what is the mistake I am making, or the values quoted in the paper are wrong ?


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Initially, at zero strain, the value of tau is zero and the denominator is finite, hence the flow rate is zero. As the deformation grows, so will tau. Note, however, as tau grows so will the flow rate which in turn will keep the value of tau rather small and the solution covergent.

The s+alpha*p term, however, can be problematic. What if the pressure p is sufficiently negative that s+alpha*p becomes 0? Then you really run into numerical problems. I think there are better ways to compensate for the pressure p. Have you tried to run your simulation with alpha=0?

- Jorgen

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