Mechanical properties of matter Flashcards
Define Tensile stress.
The tension force per unit cross-sectional area of a material Stress = Force/Area where stress is measured in Pa or Nm^-2, F = force in Newtons and A is cross-sectional area in m^2.
Define Tensile strain.
The extension per unit length of a material. Strain = extension/Original length, where Strain has no units, extension measure in metres and original length measured in metres.
Define Young’s Modulus.
The tensile stress per unit tensile strain. Young’s Modulus is stress/strain where stress is measured in Pa or Nm^-2, strain has not units and therefore Young’s modulus is measured in Pa or Nm^-2.
Define Ultimate tensile stress.
The maximum stress a material can withstand before fracture.
Define Elastic limit.
The value of stress or force beyond which elastic deformation becomes plastic deformation; the material will not return to its original shape sand size when the stress or force is removed.
Define Limit of proportionality.
The value of the stress beyond which the stress is no longer proportional to the strain.
Define Elastic Region.
Removal of stress or force will return the object to its original shape.
Define Plastic Region.
Removal of the stress or force will return the object to its original shape; the change in shape of the material is irrecoverable.
Define the yield point.
The point beyond which the material extends rapidly for a small change in stress.
Define Brittle.
a material that distorts very little even when subject to a large stress and does not exhibit much plastic deformation; for example concrete or glass.
Define Polymeric.
Materials that consist of long molecular chains; they experience a high strain before breaking.
Define Ductile.
Materials that have a large plastic region and therefore they can be drawn into a wire; for example, copper.
Define strength.
The extent to which a material resists breaking under stress; a strong material has a high ultimate tensile Strength and high breaking stress.
Define stiffness.
The extent to which a material under stress experiences a strain.
State what is meant by a Hysteresis Loop?
A loop-shaped plot obtained when, for example, loading and unloading material produce different deformations.
