06 Materials Flashcards
extension
the increase in length of an object when a tensile force is exerted on it
tensile force
equal and opposite forces acting on a material to stretch it
compression
the decrease in length of an object when a compressive force is exerted on it
compressive force
two or more forces together that reduce the length or volume of an object
tensile deformation
a change in the shape of an object due to tensile forces
compressive deformation
a change in the shape of an object due to compressive forces
force-extension graph
a graph of force against extension (or compression) with the area under the graph equal to the work done on the material
elastic limit
the value of stress or force beyond which elastic deformation becomes plastic deformation, and the material or object will no longer return to its original shape and size when the stress or force is removed
elastic deformation
a reversible change int he shape of an object due to a compressive or tensile force - removal of stress or force will return the object to its original shape and size (no permanent strain)
plastic deformation
an irreversible change in the shape of an object due to a compressive or tensile force - removal of the stress or force produces permanent deformation
Hooke’s law
the force applied is directly proportional to the extension of the spring unless the limit of proportionality es exceeded
force constant
a quantity determined by dividing force by extension (or compression) for an object obeying Hooke’s law - called constant of proportionality k in Hooke’s law, measured in Nm^-1
stiffness
the ability of an object to resist deformation
elastic potential energy
the energy stored in an object because of its deformation
loading curve
a force-extension graph
hysteresis loop
a loop-shaped plot obtained when, for example, loading and unloading a material to produce different deformations
tensile stress
the force per unit cross-sectional area, measured in Pa
tensile strain
the extension per unit length, a dimensionless quality
ductile
property of a material that has a large plastic region in a stress-strain graph, so can be drawn into wires
limit of proportionality
the value of stress or force beyond which stress is no longer directly proportional to strain
yield point
a point on a stress-strain graph beyond which the deformation is no longer entirely elastic
ultimate tensile strength
the maximum stress that a material can withstand before it breaks
breaking strength
the stress value at the point of fracture, calculated by dividing breaking force by cross-sectional area
strong material
a material with a large value for the ultimate tensile strength
Young modulus
the ratio of tensile stress to tensile strain when these quantities are directly proportional to each other, measured in Pa
polymeric
description of a material compromising of long-chain molecules, such as rubber, which may show large strains
brittle
property of a material that does not show plastic deformation and deform very little (if at all) under high stress
