Lab 2. Impact Test-Charpy Flashcards
impact test
measures the energy absorbed up to fracture upon rapid loads
it is also an indication of toughness, it tells you how resistive your sample is to impact
elastic deformation
temporary change in the shape of a material when a load is applied. the object returns to its original shape on removal of the load
plastic deformation
this type of deformation is not reverisible. in the this case, the material retains the deformed shape even after the removal of the load
ductile materials
ductile materials experience significant plastic deformation before fracture
brittle materials
they show little or no plastic deformation before fracture
toughness
measure of the ability of a material to absorb energy up to fracture
static toughness
low strain rate, tensile test
dynamic toughness
high strain rate. ability of a material to absorb energy under sudden forces and shocks-impact test
stress-strain diagram
is a plot of the stress on the (y-axis) versus the strain on the x axis
ductile fracture
cracks move slowly and are accompanied by a large amount of plastic deformation
brittle fracture
cracks move more rapidily through a stressed material. the cracks usually travel so fast taht failure occurs without warning. In other words, there is very little plastic deformation before failure occurs
tough material
HIGH ductility under high stress value… resistive to fracture under static loads
ductile material
high strain, withstand dynamic and static loads. FCC
BCC metals
inconsistency between tensile test results and impact test result
a BCC material showing ductile behavior in tensile test and high toughness can exhibit brittle behavior in impact test. this is expecially seen under room temperature
dislocation
bond breaking and reforming
mechanism of crack propagtion
in a material is the way in which the advancing crack travels through the sampleq
for ductile materials
the mechanism is microvoids
for brittle materials
are transgranular or intergranular fracture
microvids
nucleate at inclusions and second-phase particle. . the viods grow together to form a crack
transgruanular fracture
the fracture travels through the grain of the material
intergranular fracture
in the this case, the crack travels along the grain boundaries and not through the actual grains. cracks choose the path of least resistance
Impact testing
an objects ability to resist high-rate loading
charpy impact test
is standarized high strain-rate test wich determines the amount of energy absorbed by a material during fracture
impact energy
measured by the charpy test is the work done to rapture the specimen
this absorbed energy is the measure of given material’s
toughness
impact testing
measures an object’s ability to resist high rate loading
the charpy impact test
is the standarized high strain-rate test which determines the amount of energy absorbed by a amaterial during fracture
the impact energy
measured by the charpy test is the work done to rapture the specimen
the abosorbed energy is measured of a given material’s
toughness
