Stress and strain

What is monatomic testing?

A function or quantity which varys in a way that it never decreases or it never increases

What are examples of monatomic testing?

Force applied to a boy

Stress, force per unit area

Strain, extention due to a applied stress

What does a tensile load produce?

A positive linear strain

What does a compressive load produce?

A negative linear strain

What is a tensile test?

The specimen is elongated at a constant rate and the instantaneous load and resulting elongation is measured simultaneously using a load cell and extensometer

Where does deformation occur in a tensile test?

In the narrow, gauge section which has a uniform cross section

How long does a tensile test last ?

Several minutes and is a destructive test

How to calculate engineerig stress?

Force / original area

Unit - Pa

How do you calculate engineering strain?

Change in length / original length

How do you calculate youngs modulus?

Slope of linear elastic region

What is yield stress?

Limit of proportionality, start of plastic deformation

What is proof stress?

Point of interception with a 0.2% offsetw

What is the UTS?

Maximum stress value

What is ductility?

elongation measured from final fracture to original gradient as the elastic region

What is hookes law?

Measurement of stiffness

stress and strain are proportional

What is stiffness?

Measurement of the total load required to induce a certain deformation W

What does toughness show?

Resilience to fracture

What is hardness?

Measure of its resistance to penetration by an indentor

What are the different types of hardness tests?

Mohs, RockwelL, VICKERS, BRINELL.

What is the process of a hardness test?

Indentor is pressed into the surface with a set force, the area of the indent is measures

the larger the indent, the softer the material

yield strength of a material is 1/3 the hardness

What is poissons ratio?

Ratio of laterial to axial strain

usually 0.3

How do you calculate poissons ratio?

-lateral strain/ axial strain