Materials Flashcards
What is breaking stress?
The stress required to break a material
What happens when a spring goes past the elastic limit?
The spring becomes permanently stretched.
What is another unit for Pa (Pascal)
Nm^-2
What is the unit for Tensile Stress?
Pa (Pascal)
What is the spring constant rule for springs in series?
1/keff = 1/k1 + 1/k2
What is the spring constant rule for springs in parallel?
keff = k1 + k2
Define Young Modulus
A measure of the stiffness of a material
What does it mean if a material is brittle?
It snaps without stretching or breaking when subject to stress.
What is the equation for density?
Mass/volume
What happens when a spring is behaving elastically?
Up to a certain extension, if the force is removed the spring will return to its original position.
What is spring constant and what is its unit?
The force required to produce an extension of one metre.
Unit is Nm^-1
What is the equation relating extension and force?
F = k x delta L
What is the unit for density?
kgm^3
What is Hooke’s Law?
The force needed to stretch a spring is directly proportional to the extension of a spring from its natural length. Up to the limit of proportionality.
What is breaking stress?
The stress required to cause a material to break.
What happens when a string becomes permanently stretched?
Plastic behaviour occurs and Hooke’s Law is no longer obeyed by the spring.
What is the equation for tensile stress?
Tensile force / cross-sectional area
Stretching force is also called what?
Tensile force
In a force/extension graph, what is represented by the area under the graph?
Work done.
What does the unloading line look like on a force/extension graph for a metal wire that has been stretched beyond its limit of proportionality?
Parallel to the straight section of the loading line going down to the x axis.
Why does the unloading line of a force/extension graph have a non zero intercept and why is it parallel to the loading line?
Plastic deformation has produced permanent extension hence intercept is non zero.
The gradient is the same because after extension there is still the same forces between bonds as there were during loading.
