Chapter 6 Flashcards
Destructive testing
render the test material useless for services - loaded to failure
Strength
the ability to of a material to withstand an applied load
Tensile Strength
two types
the ability of a metal to resist failure when subject to tensile or pulling load.
Ultimate tensile strength (UTS) and yield strength
Shear
a ductile mode of failure
Torsional Strength
a twisting or rotation force (strength)
impact Strength
same as Notch toughness - dependent on geometry
Fatigue Strength
Cyclic or repeated mechanical action on a member till failure
Ultimate tensile strength (UTS)
The maximum load-carrying capacity of that metal at the exact point when failure occurs
Elasticity
the deformation os a metal under load which causes no permanent deformation when the load is removed
- no permanent defamation or “set”
Plastic
when a metal is stressed beyond its elastic limit
-permanent defamation or “set”
Yield point / yield strength
the point at which a material’s behavior changes from elastic to plastic is referred to as its yield point.
- used for the maximum load for structures
As temp increases strength ?
decreases
The harder a metal the tensile strength
increases and vice versa
Tensile testing
must have the following 3 features
Two common shapes of specimen
Uses a reduced section that is intended to localize failure
- uniform cross section
- Easily measured to a cross sectional area can be calculated
- Free from surface irregularities
two most common type are CIRCULAR & RECTANGULAR
Toughness
a measure of a metal’s ability to absorb energy
usually as slow rate
toughness properties values only have meaning with temperature information.
Ductility
Temp change?
opposite of ductile is?
Expressed in two ways?
the ability of a material to deform, or stretch, under load without failing.
Directly related to temperature
ductility increases at higher temps and decrease at higher temps
opposite of ductile is brittle
Percent elongation and percent reduction of area
Rolling direction
Rolling direction = X
Transverse direction is = Y
Through thickness direction = Z
Hardness
ability of a metal to resist penetration o r indentation
Hardness Tests
Tests are performed using some type of penetrator which is forced against the surface of the test object
Brinell hardnes test
BHN?
Prepare test surface / apply test load, hold load for prescribed time, measure impression diameter, determine BHN from table
Covers a large area
reduces problems with surface irregularities and localized hardness
BHN = Brinell hardness number
10mm hardened steel ball & 3000 kg load
or 10mm tungsten carbide ball & 500kg load
Field testing uses a hamer blow
Rockwell Method Hardness test
smaller indentations than Brinell testing
Loader are also less @ 60kg to 150kg
Prepare test surface / place test in Rockwell tester, apply minor load using elevating screw / apply major load / release major load / release minor load and remove part
Microhardness test
hardnest test with impressions so small that high magnification os required . can be performed on a single gran if metal.
Vickers indicator has equal sides
& Knoop indicator has a long and short dimension
Prepare test surface / place specimen in holding fixture / locate area of interest using microscope / Make indention / Measure indention using microscope / Determine hardness using tables and calculations
BHN?
= Brinell hardness number
this number X 500 is about the same as the metals tensile strength
Notch toughness
materials energy absorbing ability when there are surface flaws present
toughness usually defines the materials behavior when loaded slowly / Notch toughness values reflect the energy absorption which occurs at high rate of loading
also referred to as impact strength
notch toughness decrease as its hardness increases and its tempura rue is reduced
