Please enable JavaScript.
Coggle requires JavaScript to display documents.
Module 3 - Chapter 6 - Material II - Coggle Diagram
Module 3 - Chapter 6 - Material II
Stretching materials
Tensile stress
Defined as force applied per unit cross-sectional area of the wire
Measured in
or
Tensile strain
Fractional change in the original length of the wire
Stress-strain graph
Ductile - material can easily be drawn into a wire or hammered into thin sheets
Stress is directly proportional to the strain when the line is straight
Limit of proportionality - point where stress is no longer proportional to strain
Elastic limit - point where beyond it, object doesn't return to its original shape even when the force is removed
Yield points - points where there is a large increase in the strain for small increases in stress
UTS - Ultimate tensile strength - maximum stress that a material can withstand when being stretched before it breaks, highest point on a stress/ strain graph
Beyond the UTS, material might become longer and thinner at its weakest point
Breaking strength - stress at which the material will break
Strong material has high UTS
Young modulus
Within the limit or proportionality, stress is directly proportional to strain
Young modulus - Ratio of stress to strain for a particular material
Young modulus =
Unit is
The gradient of the linear region of the stress-strain graph
Material with a larger Young modulus is stiffer than one with a smaller
Measures a material's stiffness, independent of shape and size
Determining Young modulus
Wear eye protection, just increase the wire breaks
Initial measurement
Meaure the cross sectional area using
Averaging measurements from several places along the wire
Measure the diameter, using a micrometer
Experiment measurements
Tensile force is the weight of the masses
After each mass is applied, calculate the extension, place a fiduceal market on the original length of the wire
Airplanes
Wings made from aluminium alloy - strong and stiff (high young modulus)
Rotor blades are made from ceramics and can withstand high temperatures and are very strong
Ceramics are brittle and show no plastic deformation
Tyres are made from rubber, which has elastic properties and is a great shock absorber
Other materials
Brittle material
Elastic behaviour is shown until the breakpoint where the material snaps
No plastic deformation
Loading and unloading curves are the same
Material that breaks at low strain, it doesn't yield
Elastic material
Endure alot of tensile stress before breaking
No plastic deformation
Unloading curve is different to loading curve
Some energy is lost as thermal
Ductile material
Easily be hammered into thin sheets
Experience elastic deformation until their elastic limit
Undergo plastic deformation before reaching UTS and breakpoint
Polymeric
