6 - Materials Flashcards
What are forces that produce extension known as?
Tensile forces
What are forces that produce compression known as?
Compressive forces
What is tensile deformation?
When tensile forces are exerted (a spring is stretched)
What is compressive deformation?
When compressive forces are exerted (a spring is compressed)
What is extension?
The difference between the length before and after it is stretched (extended)
What is compression?
The difference between the length of a string before and after it is squashed (compressed)
What is Hooke’s law?
The extension of a string is directly proportional to the force applied. This is true as long as the elastic limit of the spring has not been exceeded.
Define the force constant of a spring.
The force applied to give one metre (unit length) of extension.
How many forces do you need to change an object’s shape?
More than one
What happens to the force, extension graph for a spring after the elastic limit is exceeded?
It stops being directly proportional, it curves.
When is work done fully recoverable from an extended object?
Before it reaches the elastic limit.
Why is work done not fully recoverable from an object that has been extended past its elastic limit?
Because some work has been done on the material to change the position of the atoms.
What is the equation for work done?
W = Fx
What does the area under a force extension graph represent?
The work done.
What is plastic deformation?
When an object is stretched past its elastic limit and therefore will not return to its original shape.
What is elastic deformation?
When an object is stretched up to its elastic limit and therefore will return to its original shape.
What is the elastic limit of a material?
The point at which an object stops being elastic and plastic deformation begins.
What is tensile stress?
The force applied to a material per unit cross sectional area.
What is tensile strain?
The extension per unit original length due to an applied stress.
What is ultimate tensile strength?
The maximum stress a material can withstand before it breaks.
What is the Young Modulus?
The ratio of stress to strain for a particular material.
Why is the Young Modulus useful?
It is a property of a material and does not change with size or shape.
