Matter mechanics: Ideal & observed stress

[Master J]

So I understnad that typical solid state bonds brake at stress of up to 20%.
Why though, in reality, do we never observe this? Is it due to inherent inhomogenieties?

What kinds of mechanisms & structures would cause this observed strain in tensile and shear cases?

Could one observe ideal stresses in materials at all?


Matter is a fascinating subject! :p

thank you!

 

[Mapes]

So I understnad that typical solid state bonds brake at stress of up to 20%.
Why though, in reality, do we never observe this? Is it due to inherent inhomogenieties?

What kinds of mechanisms & structures would cause this observed strain in tensile and shear cases?

Could one observe ideal stresses in materials at all?


Matter is a fascinating subject! :p

thank you!

Do you mean a strain of 20%? Strain is unitless, stress has units of pressure.

Some metal whiskers (tiny single crystals) have been growth with strengths close to the theoretical value, but most polycrystalline materials contain large numbers of http://en.wikipedia.org/wiki/Dislocation#Dislocations.2C_slip_and_plasticity" that reduce strength by allowing a relatively small number of bonds to break at a time. Is this what you were asking about?