Materials Flashcards
(25 cards)
What is the formula for density?
Density = Mass ÷ Volume
What is Hooke’s Law?
Force is directly proportional to extension: F = kΔL
What does ‘k’ represent in Hooke’s Law?
The spring constant (N/m), indicating stiffness.
What happens beyond the limit of proportionality?
Extension is no longer proportional to force; Hooke’s law no longer applies.
How do you find the extension of a spring?
ΔL = Stretched Length – Unstretched Length
What is shown by the straight-line section of a force-extension graph?
The region where Hooke’s Law is obeyed.
What is the significance of the gradient in a force-extension graph?
Gradient = Spring constant (k)
What is the elastic limit?
The maximum extension where the material still returns to its original shape.
Define tensile stress.
Stress = Force ÷ Cross-sectional Area (Pa)
Define tensile strain.
Strain = Extension ÷ Original Length (no units)
What is the ultimate tensile stress?
The max stress a material can handle before breaking.
What does the area under a stress-strain graph represent?
Elastic strain energy per unit volume.
What is yield stress?
The stress at which plastic deformation begins.
What is breaking stress?
The maximum stress before a material fractures
What is elastic deformation?
Material returns to original shape after load removed.
What is plastic deformation?
Material remains permanently deformed after load removed.
What is a brittle material?
Breaks with little or no plastic deformation (e.g. glass)
What is a ductile material?
Stretches significantly before breaking (e.g. copper)
What do shock absorbers in vehicles do?
Convert kinetic energy into heat to dampen motion.
Why do shock absorbers help with control and comfort?
They reduce vibrations and maintain tire-road contact.
What does the Young modulus measure?
The ability of a material to withstand changes in length when a load is applied — a measure of stiffness.
Why is Young modulus important for engineers?
It helps ensure materials used can withstand sufficient forces without deforming too much.
What are the units of Young modulus?
Pascals (Pa), since strain is dimensionless.
How can you find the Young modulus from a stress-strain graph?
It is the gradient (slope) of the linear (straight-line) region where Hooke’s law applies.
