Chapter 6 (Mechanical Properties)
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Stress equation
stress=F/A
Strain equation
strain=delta L/L0
which type of deformation is reversible
elastic
which type of deformation is permanent
plastic
Yung’s Modulus equation
stresss=(Yung’s)*Strain
what does the elastic modulus(yungs) tell us about a material
how much it will stretch
How to compare E between materials
compare the slopes of stress-strain curves
what is Yield strength
the stress at which noticeable plastic deformation has occurred
what is tensile strength
the MAXIMUM stress on the stress-strain curve
what is ductility
measure of the amount of plastic deformation before a material breaks
what is toughness
the energy required to break a unit volume of a material
how would you approximate the toughness of a material
compare the areas under the curves (stress-strain)
what is Resilience
the ability of a material to absorb energy during the ELASTIC deformation and give it back when unloaded
Ur(Resilance)=
area under curve until yield strength
what is hardness
a measure of the resistance to LOCALIZED plastic deformation
what is the conventional unit we use for stress?
MPa
what are the units of strain
strain is dimensionless
what does E(yung’s modulus) tell us microscopically?
its is a measure of how well the atoms are bonded together
is it possible to alter the stiffness of a metal?
impossible
what is poisson’s ratio?
a ratio of how much strain occurs on a material in the X & Y directions when strained in the Z direction
simple tension equation
sigma=FLo/EAo
simple torsion equation
alpha=2MLo/(pi)(r^4)G, where G is the elastic shear modulus
what is yielding
when deformation changes from elastic to plastic
when does the tensile strength occur for metals
when noticeable necking starts