3.4: Materials Flashcards
Brittle
A brittle object is one that shows very little strain before reaching its breaking stress.
Compression
The result of two coplanar forces acting into an object. Compression usually results in a reduction in the length of the object.
Compressive deformation
The changing of an object’s shape due to compressive forces.
Ductile
A material is ductile if it can undergo very large extensions without failure. Ductile materials can be stretched into wires.
Elastic deformation
If a material deforms with elastic behaviour, it will return to its original shape when the deforming forces are removed. The object will not be permanently deformed.
Elastic potential energy
The energy stored in an object when its stretched. It is equal to the work done to stretch the object and can be determined from the area under a force-extension graph.
Extension
The increase of an object’s length
Force-extension graph
A plot showing how an object extends as the force applied increases. For an elastic object, the gradient should be linear up to the limit of proportionality. The gradient gives the spring constant.
Hooke’s Law
The extension of an elastic object will be directly proportional to the force applied to it up to the object’s limit of proportionality.
Plastic deformation
If a material deforms with plastic behaviour, it will not return to its original shape when the deforming forces are removed. The object will be permanently deformed
Polymeric
A material made from polymers
Spring constant
The constant of proportionality for the extension of a spring under a force. The higher the s[ring constant, the greater the force needed to achieve a given extension.
Strain
The ratio of an object’s extension to its original length. It is a ratio of two lengths and so has no unit.
Stress
The amount of force acting per unit area. Its unit is the Pascal (Pa)
Tensile deformation
The changing of an object’s shape due to tensile forces.
