Chapter 6 Flashcards
elastic means ____________
reversible
plastic means__________
permanent
stress has units _________ or _______
stress has units N/m^2 or lb/in^2
strain is always ___________
dimensionless
units for
E:
v:
E=GPA or psi
v: dimensionless
slope of stress strain plot (________________________) depends on bond strength of metal
which is proportional to the elastic modulus
material, geometric, and loading parameters all contribute to ___________
deflection
large ________ minimize elastic deformation
elastic moduli
yield strength=?
stress at which noticeable deformation has occured
metals:
polymers:
metals- occurs when noticeable necking starts
polymers: occurs when polymer backbone chains are aligned and about to break
what is toughness?
energy to break a unit volume of material
approximate by the area under the stress-strain curve
what is hardness?
resistance to permanently indenting the surface
large hardness means:
-resistance to plastic deformation or cracking in compression
-better wear properties
rockwell:
no major sample damage
elastic modulus is material property
critical properties depend largy on sample flaws (defects etc) large sample to sample variabilit
?
design or safety factors:
design uncertainties mean we do not push the limit
stress and strain:
these are size independent measures of load and displacement, respectively
elastic behavior:
the reversible behavior often shows a linear relation between stress and strain to minimize deformation, select a material with a large elastic modulus (E or G)
plastic behavior:
the permanent deformation behavior occurs when the tensile (or compressive) uniaxial stress reaches shear stress y
toughness
the energy needed to break a unit volume of a material
ductility
the plastic strain at failure
