# Stress and strain atomic level

1. Nov 12, 2013

### jayanth nivas

Hi all,
This is a question regarding stress and strain.
Can someone please explain the concepts of stress and strain in atomic level?

My understanding is as follows.Let us consider a metal bar or rod that is subjected to tension.The load applied to the bar will be try to elongate the bar,that is it will try to pull the atoms of the metal apart.The atoms do have a strong force binding them so they will offer resistance to the load.So if i cut the cross section of the bar,the atoms on the surface will try to balance the force applied in order to maintain the equilibrium.So we take the internal resistance as the force applied by the area of the cross section.(But i'm not sure how atomic density affects this).

Now my understanding strain and hence the deformation is as follows.When the load is applied,the distance between the atoms slightly increases before an equilibrium is achieved between internal and external forces.This movement of atoms is converted into stain energy that is stored in the bar.As long as the applied load is retained,the distance of separation and hence strain energy is retained.When the applied load is removed,the strain energy is used to move the atoms back to the original state.

The problem with above statement is I assume the atoms will move before an equilibrium is established.Can anyone explain to me this a bit clearly?

And also the role of Young's modulus in this.If young's modulus is less,does that mean the atoms will move more before an equilibrium is reached?.If it is more does that mean elasticity is less?.

I think this is a stupid question but i will ask it anyway.If the applied load deforms the material and some part of the load is getting stored as strain energy,then will the internal resistance offered be for a load less than the applied load.It doesn't make sense any way but can some one explain this to me in terms of energy?

Sorry for long post.And thanks in advance

2. Nov 14, 2013

### jayanth nivas

Is my question confusing ? .Or am I asking something very basic?.Please reply so that I can improve