Materials Flashcards
(22 cards)
What happens when you pull on a spring fixed at one end?
It will stretch or extend.
What does Hooke’s law state?
F equals KE, where F is force, K is spring constant, and E is extension.
What is the unit for spring constant?
Newtons per meter.
What does elastic deformation mean?
An object returns to its original shape once the force is removed.
What happens when two springs are attached in series?
They stretch twice as far with the same force, meaning the spring constant must be half.
What is stress?
Stress is force per unit area, measured in newtons per meter squared or pascals.
What is strain?
Strain is the ratio of extension to original length.
What does a graph of stress against strain typically show?
A proportional relationship, at least initially.
What does the gradient of the stress-strain graph give us?
The Young’s modulus.
How is Young’s modulus measured?
In pascals.
What is the full version of the Young’s modulus equation?
E equals FL over A delta L.
How is area related to diameter?
Area is proportional to D squared.
What happens if you double the diameter of a material?
The extension quarters.
What occurs when the graph starts to curve?
We’ve gone past the limit of proportionality.
What happens when the force is removed after the graph curves?
It can still return to its original position, behaving elastically.
What does the area under the loading curve represent?
The energy needed to stretch the material.
What does the area under the unloading curve represent?
The energy returned as it returns to its original length.
What is the elastic limit?
The point beyond which the material will not return to its original length.
What is plastic deformation?
Deformation that occurs when the elastic limit is exceeded.
What is ultimate tensile stress?
The maximum stress the curve reaches before necking occurs.
What characterizes a ductile material?
It has a large plastic region.
What happens to brittle materials under stress?
They generally have a high Young’s modulus and snap suddenly before plastic deformation.
