Bulk Properties of Solids

Mechanics and Materials

Definition of Density

Mass per unit volume that indicates how much matter is contained in a given space ( how ‘compact’ the particles are)

What is Hookes law?

Extension is directly proportional to the force applied to an elastic material, given that the environmental conditions are kept constant

What does spring constant measure?

the stiffness of a material (the higher the constant the stiffer the material)

What is the limit of proportionality?

beyond hte limit of proportionality, hooks law is no longer true

What is Elastic limit?

The maximum stress that a material can withstand without undergoing permanent deformation. Beyond this point, the material will not return to its original shape.

How do you calculate Extension?

Extention = stretch length - original length

What is Tensile stress?

The force exerted per unit cross-sectional area of the material (Pa)

What is Ultimate Tensile stress?

The maximum force per cross-sectional area (tensile stress) an object can withstand before it fractures

What is Tensile strain?

• The extension per unit length

• This is a deformation of a solid due to stress in the form of elongation or contraction

  (it is a dimensionless unit due to its ratio of lengths)

Formula of Tensile stress

Tensile stress (𝜎) = F / A

What is the formula for Tensile strain?

Tensile strain (𝜖) = ΔL / L₀

What is the definition of Plastic?

where a material will experience a large amount of extension as the load is increased. Especially beyond the elastic limit.

Define Brittle

Where a material will extend very little and therefore is likely to fracture

When stretch is elastic what becomes of the workdone?

The workdone is stored as Elastic strain energy

When stretch is plastic what becomes of the workdone?

workdone is used to move atoms apart and therefore, energy is dissipated as heat

How do you calculate the workdone from a force extension graph

the area between loading and unloading