Materials Flashcards
What is Hooke’s law
Extension (∆L) is directly proportional to force applied (F), given that the environmental conditions are kept constant.
F= k∆L
What is meant by tensile stress
The force applied per unit cross sectional area
What is tensile strain
A measure of how the material stretches: the extension (ΔL) divided by the original length (L), strain has no units
What is the difference between elastic and plastic deformation
Elastic deformation: when the force is removed the object will return to its original shape.
Plastic deformation: after the load is removed the object will not return to its original shape
What is breaking stress
The minimum stress needed to break a material
What is meant when a material is described as brittle
A brittle object will show very little strain before reaching its breaking stress
What is the elastic limit
The force above which the material will be plastically deformed (permanently stretched)
What does the area underneath a force extension graph represent
The work done to deform the material
Work done= ½ x F x ΔL
What is Young’s modulus
Young’s modulus (E) = tensile stress/ tensile strain.
It describes the stiffness of a material
Outline the energy changes that occur when a spring fixed at the top is pulled down and released
The work done in pulling the spring down (stretching it) is stored as elastic strain energy, when the spring is released this is converted to kinetic energy which is converted to gravitational potential energy as the spring rises
What is Breaking Stress
The maximum stress that an object can withstand before failure occurs
Define stiffness
A measure of how difficult it is to stretch a given object
What is ultimate tensile strength (UTS)
The maximum stress that a material can withstand while being stretched or pulled before breaking
