MMET 181 TEST 1 STUDY GUIDE
Strain - Answers :The controllable stretch or deformation on a specimen
Stress - Answers :The controllable ratio force/area on a specimen
ductility or elongation - Answers :The maximum strain before fracture of a material is the
material
material strength - Answers :The maximum stress before fracturing of a material
Normal stress - Answers :"sigma" = F/A = applied force/cross sectional area
Force is perpendicular to cross sectional area
Shear stress - Answers :"tao" = Fs/As = applied shear force/sheared area
Shear force is parallel to sheared area
Small strain - Answers :"metal"
% stretching
"Elongation" = Change in length/Original length = (Final length - Initial length) / Initial
length
Large strain - Answers :"plastics, rubber"
"Elongation" = ln (Final length/Initial length)
Shear strain - Answers :distortion
"y"
Tensile test - Answers :Increase force on a sample until breaking
Force is 90 degrees to the fractured surface
Note: If Normal stress is (> or equal to) Tensile strength then material fails
catastrophically
Normal stress - Answers :"sigma" = F/A
Small strain - Answers :"Elongation" = Change in length/Original length
Yield strength - Answers :S "sub y"
Tensile strength - Answers :S "sub u"
Shear test - Answers :Increase force on a sample until breaking
Force is parallel to the fractured surface
Note: If Shear stress is (> or equal to) Shear strength then material fails catastrophically
, Shear stress - Answers :"Tao" = P/A "sub s"
Shear strain - Answers :"tao"
Shear strength - Answers :S "sub s"
Relationship between shear strength and tensile strength - Answers :Shear strength =
0.577 Tensile strength
or approximately
0.5 Tensile strength
Harness test - Answers :a) Force a hard indenter @ preset force, time onto a surface
b) Measure indentation
c) Calculate hardness. The hardness depends on applied force, indenter geometry, and
the resulting indentation
Brinell method - Answers :10 mm diameter ball
load of 500, 1500 or 3000 kgf
Brinell method (equation) - Answers :IN BOOK
HB = Brinell hardness number
F = load (kgf)
D "sub b" = ball diameter (mm)
D "sub f" = indentation diameter (mm)
Rockwell method - Answers :Different Rockwell scales depending on the material
hardness; named Rockwell A-scale (R "sub a") through Rockwell H-scale (R "sub h").
Does not depend on the surface indentation, but the depth recovery of an indenter after
removing the major load.
Vicker method - Answers :Uses a 136 degree square pyramid to indent a surface at
various loads
Vicker method (equation) - Answers :IN BOOK
HV = Vicker hardness number
F = load (kgf)
D = average diagonal of indentation (mm)
Knoop method - Answers :Uses a pyramid shape indenter with 7:1 length to width ratio
and a load in the range from 25g to 3.6 kg
Knoop method (equation) - Answers :IN BOOK
HK = Knoop hardness number
F = load (kgf)
D = long diagonal of indentation (mm)
Strain - Answers :The controllable stretch or deformation on a specimen
Stress - Answers :The controllable ratio force/area on a specimen
ductility or elongation - Answers :The maximum strain before fracture of a material is the
material
material strength - Answers :The maximum stress before fracturing of a material
Normal stress - Answers :"sigma" = F/A = applied force/cross sectional area
Force is perpendicular to cross sectional area
Shear stress - Answers :"tao" = Fs/As = applied shear force/sheared area
Shear force is parallel to sheared area
Small strain - Answers :"metal"
% stretching
"Elongation" = Change in length/Original length = (Final length - Initial length) / Initial
length
Large strain - Answers :"plastics, rubber"
"Elongation" = ln (Final length/Initial length)
Shear strain - Answers :distortion
"y"
Tensile test - Answers :Increase force on a sample until breaking
Force is 90 degrees to the fractured surface
Note: If Normal stress is (> or equal to) Tensile strength then material fails
catastrophically
Normal stress - Answers :"sigma" = F/A
Small strain - Answers :"Elongation" = Change in length/Original length
Yield strength - Answers :S "sub y"
Tensile strength - Answers :S "sub u"
Shear test - Answers :Increase force on a sample until breaking
Force is parallel to the fractured surface
Note: If Shear stress is (> or equal to) Shear strength then material fails catastrophically
, Shear stress - Answers :"Tao" = P/A "sub s"
Shear strain - Answers :"tao"
Shear strength - Answers :S "sub s"
Relationship between shear strength and tensile strength - Answers :Shear strength =
0.577 Tensile strength
or approximately
0.5 Tensile strength
Harness test - Answers :a) Force a hard indenter @ preset force, time onto a surface
b) Measure indentation
c) Calculate hardness. The hardness depends on applied force, indenter geometry, and
the resulting indentation
Brinell method - Answers :10 mm diameter ball
load of 500, 1500 or 3000 kgf
Brinell method (equation) - Answers :IN BOOK
HB = Brinell hardness number
F = load (kgf)
D "sub b" = ball diameter (mm)
D "sub f" = indentation diameter (mm)
Rockwell method - Answers :Different Rockwell scales depending on the material
hardness; named Rockwell A-scale (R "sub a") through Rockwell H-scale (R "sub h").
Does not depend on the surface indentation, but the depth recovery of an indenter after
removing the major load.
Vicker method - Answers :Uses a 136 degree square pyramid to indent a surface at
various loads
Vicker method (equation) - Answers :IN BOOK
HV = Vicker hardness number
F = load (kgf)
D = average diagonal of indentation (mm)
Knoop method - Answers :Uses a pyramid shape indenter with 7:1 length to width ratio
and a load in the range from 25g to 3.6 kg
Knoop method (equation) - Answers :IN BOOK
HK = Knoop hardness number
F = load (kgf)
D = long diagonal of indentation (mm)
