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Mar. 16/10/2018 14:00 Petite Ourse, Bâtiment 13, Etage 1 SINGH Murari (L2C) Elasticity in Amorphous Solids: Nonlinear or Piecewise Linear? At low temperature, amorphous solids exhibit an elastic response to small strains(γ) or stresses(σ) and initially display a linear response to a quasistatic external loading with a shear modulus (μ) that relates the stress to the strain. We can write σ = μγ; γ << 1. Upon the increase in the external loading, this linear relation appears to fail. The response of the amorphous solid begins to mix elastic intervals interspersed with plastic events, leading generically to an apparent nonlinear dependence of the stress as a function of the strain. The stress versus strain curves for large values of the strain either end abruptly due to a catastrophic failure of the material or display a regime of “steady state” where the shear modulus appears to vanish. Viewing stress versus strain curves of this type, one is tempted to present them before the onset of the steady state as a nonlinear expansion of the stress in powers of the strain. In this talk, I will explain that such an expansion needs to be reconsidered. I will show the enormous difference between quenched and annealed averages of the stress versus strain curves and propose that a useful description of the mechanical response is given by a stress (or strain) -dependent shear modulus. The elastic response is piecewise linear rather than nonlinear. Pour plus d'informations, merci de contacter Berthier L. |
