Mechanical Properties Flashcards
What is engineering stress?
Force/original area
What is true stress?
Force/area at that point
What is tensile strength?
(Ultimate Tensile Strength) The maximum stress on a stress-strain cure
Describe elastic deformation
It will return to its original shape
Describe plastic deformation
Won’t return to its original length (permanently deformed)
What is Young’s modulus?
Stress/strain (gradient of the stress-strain curve
What is Hooke’s law?
Stress is proportional to strain
What is yield strength?
The stress required to produce a small amount of plastic deformation (strength related to a permanent strain of 0.1%)
Brittle material
Will only deform elastically
Ductile material
Will deform elastically and plastically
Necking
Happens after UTS, void forms inside the neck, the void then propagates causing the material to fail and produce a fracture
What is poisson’s ratio?
-strain lateral/ strain longitudinal
What is tensile stress?
Perpendicular force / area
What is shear stress?
Parallel force / area
What is toughness?
The energy a material can absorb before it breaks (area under stress-strain curve)
Describe the Charpy and Izod impact test?
Initial height is measured, the hammer swings and the final height is measured, the difference in potential energy is the energy absorbed
What is hardness?
Ability of a material to resist scratching, surface indentation and plastic deformation
Describe the Brinell hardness test
Ball is pressed into the surface of the material, the hardness is then calculated using force/ surface area of impression
What is specific gravity?
Density of material / density of water
