i’m not really familiar with this material. but reading some articles, the units of hyperelastic ( Arruda-Boyce) materials are example given:
- Mu = 0.133 (MPa)
- lamda = 1 (unitless)
- D = 4.3 (1 / MPa)
another source notify D is half of bulk modulus, so the units should be in MPa. may this is the case of inconsistent unit.