Materials Flashcards
Stress is…
Force per unit area
Stress equation =
F/A
Stress units:
Pascals or NM^(-2)
Strain is…
extension (or compression) per unit initial length
Strain equation =
x/L
Strain units:
none
Young Modulus is…
the ratio of stress to strain for a material
Young modulus equation =
stress/strain
or
FL/Ax
F = force, L = initial length, A = Area, x = extension
Young modulus units:
same as stress (pascals and Nm^(-2)
What is the limit of proportionality?
also called proportional limit, where stress is proportional to strain
What is the elastic limit?
stops being elastic deformatin, becomes plastic
What is the yield point?
Point where a small stress causes a big strain
What does UTS stand for?
Ultimate tensile strength
What is ultimate tensile strength?
where failure occurs (I think this is where band breaks)
Describe what a stong, brittle material’s stress/strain graph would look like?
steep straight line, maybe small curve at top of line
Describe what a stongish, less ductile metal alloy’s stress/strain graph would look like
relatively steep line, curve with flatish line at top
Describe what a much less stong, less stiff and more ductile material (like toffee)’s stress/strain graph would look like
small curve, straight line
____
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give an equation for the elastic energy stored in a stretched spring in terms of force applied and extension of spring
Eel=1/2fx
If three identical springs were put in series, how would the spring constant of the system compare to just one of the springs on its own with the same force applied?
1/3 as much
If three identical springs were put in series, how would the total extension of the system compare to just one of the springs on its own with the same force applied?
Three times as much
If five identical springs were placed in parallel, how would the total extension of the system compare to just one of the springs on its own with the same force applied?
1/5 as large
Elastic behaviour
A material that deforms when a force is applied, but which returns to it’s initial shape when the force is removed
Plastic behaviour
A material that deforms when a force is applied and stays in its deformed shape when the force is removed
