The discussion centers on the Poynting effect in the context of simple shear deformation, specifically defined as the relationship between shear and normal stresses. Participants clarify that in large deformations, the stress tensor behaves non-linearly, resulting in non-zero normal stresses even when one shear stress component is zero. The conversation emphasizes the importance of precise definitions in understanding the Poynting effect, particularly in relation to the state of stress not being isotropic and all normal stresses being non-zero.
PREREQUISITESMechanical engineers, materials scientists, and researchers in continuum mechanics seeking to deepen their understanding of shear deformation and the Poynting effect.
No, but about shear and the corresponding normal stressesChestermiller said:You're talking about the effect of pressure on the Gibbs free energy?
I have no idea what you are referring to. Are you asking about the components of the stress tensor for the shear deformation you defined?feynman1 said:No, but about shear and the corresponding normal stresses
Yes, the normal and shear stress components, that is discussion about the normal components when shear is present.Chestermiller said:I have no idea what you are referring to. Are you asking about the components of the stress tensor for the shear deformation you defined?
OK. Are you familiar with the 3D tensorial version of Hooke's Law? If so, for this particular deformation, what does that predict for the components of the strain and stress tensors?feynman1 said:Yes, the normal and shear stress components, that is discussion about the normal components when shear is present.
Yes and I did the analysis, just wonder the precise definition of the effectChestermiller said:OK. Are you familiar with the 3D tensorial version of Hooke's Law? If so, for this particular deformation, what does that predict for the components of the strain and stress tensors?
Precise definition of what effect?feynman1 said:Yes and I did the analysis, just wonder the precise definition of the effect
poyntingChestermiller said:Precise definition of what effect?
right, but that's just a description not a rigorous definition. Does poynting refer to nonzero normal stresses or one specific normal stress component?Chestermiller said:In large deformations (even shear), the stress tensor is not just a linear function of the strain tensor, however that is defined (there are many tensorially acceptable definitions for finite strains). It is a non-linear function of the strain tensor, and this non-linearity results in not only shear stresses, but also normal stresses that are functions of the amount of shear (in simple shear).
For the deformation described in this thread, the state of stress is not isotropic, and all three normal stresses are non-zero.feynman1 said:right, but that's just a description not a rigorous definition. Does poynting refer to nonzero normal stresses or one specific normal stress component?
So if only one of sigma_x and sigma_y is 0, will that be called poyning effect?Chestermiller said:For the deformation described in this thread, the state of stress is not isotropic, and all three normal stresses are non-zero.
What it is specifically called does not matter (to me). What matters is whether such an effect exists.feynman1 said:So if only one of sigma_x and sigma_y is 0, will that be called poyning effect?
agree, but that will affect assessment and comparison with the literature when not knowing if the same thing is discussedChestermiller said:What it is specifically called does not matter (to me). What matters is whether such an effect exists.