Equivalence of positive corotational rates and strong monotonicity conditions

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Let E:Sym⁡++(3)→Sym⁡(3)\mathcal{E}: \operatorname{Sym}^{++}(3) \to \operatorname{Sym}(3) be a spatial strain tensor with strongly monotone scale function e:R+→Re: \mathbb{R}^+ \to \mathbb{R}. For a corotational rate D∘Dt\frac{\mathrm{D}^{\circ}}{\mathrm{D} t}, let B∈Sym⁡++(3)B\in\operatorname{Sym}^{++}(3) and D∈Sym⁡(3)D\in\operatorname{Sym}(3), and write ℓ(t)>0\ell(t)>0 for the one-dimensional stretch and D‾=ℓ˙(t)/ℓ(t)\overline D=\dot\ell(t)/\ell(t). Equivalence conjecture. The rate D∘Dt\frac{\mathrm{D}^{\circ}}{\mathrm{D} t} is positive, meaning

⟨D∘Dt[B],D⟩>0\left\langle \frac{\mathrm{D}^{\circ}}{\mathrm{D} t}[B],D\right\rangle>0

for every nonzero D∈Sym⁡(3)D\in\operatorname{Sym}(3), if and only if the corresponding one-dimensional and three-dimensional conditions hold:

 ⁣d ⁣dt[e(ℓ(t))]ℓ˙(t)>0for every ℓ˙(t)≠0,\frac{\mathop{}\!\mathrm{d}}{\mathop{}\!\mathrm{d}t}[e(\ell(t))]\dot\ell(t)>0\quad\text{for every }\dot\ell(t)\ne0,  ⁣d ⁣dt[e^(log⁡ℓ(t))]D‾>0for every D‾=ℓ˙(t)ℓ(t)≠0,\frac{\mathop{}\!\mathrm{d}}{\mathop{}\!\mathrm{d}t}[\widehat e(\log\ell(t))]\overline D>0\quad\text{for every }\overline D=\frac{\dot\ell(t)}{\ell(t)}\ne0,

and

⟨D∘Dt[E(B)],D⟩>0for every D∈Sym⁡(3)∖{0}.\left\langle\frac{\mathrm{D}^{\circ}}{\mathrm{D}t}[\mathcal{E}(B)],D\right\rangle>0\quad\text{for every }D\in\operatorname{Sym}(3)\setminus\{0\}.

The claim proposes a multidimensional characterization of positivity for corotational rates in terms of the corresponding one-dimensional strong-monotonicity inequalities and the strain tensor E\mathcal{E}.

References

Primary source

Patrizio Neff, Sebastian Holthause, Sergey N. Korobeynikov, Ionel-Dumitrel Ghiba and Robert J. Martin, “A natural requirement for objective corotational rates – on structure preserving corotational rates”, arXiv:2409.19707 (2024).

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