Flashcards in Lectures 1-3 Deck (21)
What is a stress-strain diagram
-A diagram used to show tensile strength, youngs modulus(m), yield strength(y-max), stiffness and toughness
Engineering stress N^2/m, σ
-force/original cross-sectional area
Engineering strain, ε, (no units)
the change in length/original
-The amount of force required to cause a rope wire or beam to the point where it breaks.
Ultimate tensile strength- is the maximum stress on a stress-strain graph
When a material changes shape when undergoing stress but will return to its original shape once the stress is removed.
When a material changes shape when it undergoes stress but do not return to its original shape
Youngs Modulus, E
A measure of elasticity of an object, equal to the stress acting on an object compared to the strain.
-The point at which the object under stress starts to deform plastically, usually 0.2% of the unstressed length
What is Hooke's law
-Stress is proportional to the strain on an object, up to the elastic limit.
The point at which a specimen fails via fracture
When an object is subjected to stress it breaks with little elastic deformation and without significant plastic deformation.
Has the ability to withstand tensile strength and can be stretched without becoming weak/brittle.
True stress is the stress but the cross-sectional area will change with the elastic and plastic deformation of the object
-The ratio of the transverse contraction strain to the longitudinal
Stress in the direction of the cross-sectional area
How is ductility measured?
percentage or elongation
percentage of reduction in cross-sectional area
The amount of energy an object can absorb per unit volume before fracturing.
The area under a stress-strain diagram
Name two tests for toughness
What is a Charpy test?
Indent in the object before the impact, to focus on an imperfection
Bar placed behind the imperfection
What is an Izod test?
-Fixes into a pocket and the bar swings and takes the object off if KE>toughness