Stresses along different planes in polycrystalline materials

[Srivathsan123]

A polycrystalline material is made up of many grains and grain boundaries. Each grain consists of lattices in different planes and hence different slip planes. Is that why we find stresses on different planes using mohrs circle(or analytically) even in a uniaxial tensile test.

 

[Arjan82]

No.

Does Mohr's circle contain any information about the crystalline structure of the material? How would it know then? Would Mohr's circle work for perfectly homogenous material?

The stresses are different in different planes because stress is a tensor.

 

[Chestermiller]

No.

Does Mohr's circle contain any information about the crystalline structure of the material? How would it know then? Would Mohr's circle work for perfectly homogenous material?

The stresses are different in different planes because stress is a tensor.

To add, Mohr's circle also applies to homogeneous materials.

 

[Srivathsan123]

Thanks for the replies.
I am still a bit unclear. Is there a relation between the slip planes, critically resolved shear stress that we study in material science and the stresses that we find on oblique planes in strength of materials. Or are they separate? If they are separate, where do the oblique planes come from.

 

[Arjan82]

They are entirely separate.

I cannot easily explain in very simple terms why the stress is different for different planes other than to say that they are tensors. Maybe the only thing I can say is that if you have a cylinder in axial load, then a plane at a right angle with the axis will give you only normal stresses and no shear stresses. If instead you take a plane that is parallel to the axis you will find only shear stresses and no normal stresses. This is maybe something you can imagine.

If you want to know more, you need to study stresses.