MMET 207 EXAM 1 QUESTIONS AND ANSWERS
Types of Hardness Testing (3) - Answers :Rockwell, Brinell, Vickers or Knoop
Rockwell Hardness Testing (process) - Answers :Apply minor load, apply major load,
remove loads, calculate the difference of the indentions
Rockwell Hardness Testing (Indentors) - Answers :1/16" Tungsten Carbide Ball for B&T
120 degree Diamond Cone or Brale for C, A, & N (EX: HRC)
Rockwell Regular loads - Answers :Minor: 10 kg
Major: 60kg, 100kg, 150kg
Rockwell Superficial loads - Answers :Minor: 3kg
Major: 15kg, 30 kg, 45kg
What does a major load mean? - Answers :Load that makes the second indention
Differences between regular and superficial loads - Answers :regular - prefer to use this
superficial - use if material is really thin or soft
Rockwell: difference between Beuler and Wilson? - Answers :They are just different
brands, same type of rockwell hardness test
Brinell Hardness Test - Answers :Uses 10mm ball as indentor
Smash ball into metal surface and measure diameter of the indention
What are the mechanical properties of metals? - Answers :- strength
- formability
- stiffness
- toughness
- durability
Strength - Answers :Material's ability to accommodate stress
Properties of Strength (6) - Answers :- tensile
- yield
- compression
- flexural
- shearc
- creep
Formability - Answers :The easiness to shape a metal; can I bend this w/o breaking it?
Properties of Formability (3) - Answers :- % elongation
- % reduction in area
, - bend radius
Toughness - Answers :The energy required to fracture the volume of a material
(measured in foot pounds)
Properties of Toughness (2) - Answers :- impact strength
- notch sensitivity
Durablilty - Answers :Wear resistance
Properties of Durability - Answers :- Hardness
- Wear resistance
- Fatigue strength
Stress - Answers :-A force distributed over an area or object
-Stress = F/Ao
-Units: (lb/in2) or (psi or ksi) or (N/m2)
Strain - Answers :-Percentage size change of a material in a particular direction when
subjected to a force in that direction
-Strain (Es) = Lf - Lo / Lo
-Units: none or (in/in) or (m/m)
Ultimate tensile strength - Answers :The maximum stress that can be applied to a
material before it breaks
Elastic limit/Yield Point - Answers :point where a material goes from elastic to plastic;
last point on linear part of graph
Break point - Answers :End of plastic behavior; where a material breaks
What is 0.2% offset yield (Engineering yield strength) - Answers :the stress at which a
material exhibits a specified deviation from proportionality of stress/strain. Also, it hard
to determine precisely so yield point is considered at an offset strain of 0.2%
How to find 0.2% offset yield - Answers :determining .002 strain and traveling parallel to
modulus of elasticity
Modulus of Elasticity
(What is it?, formula, where on stress/strain curve, tell about the material?) - Answers :-
A measure of rigidity ( or stiffness)
- Slope of linear line
- delta stress/ delta strain (Es)
- tells a material's stiffness
Modulus of Elasticity of Steel - Answers :E(steel) = 30x10^6 psi
Types of Hardness Testing (3) - Answers :Rockwell, Brinell, Vickers or Knoop
Rockwell Hardness Testing (process) - Answers :Apply minor load, apply major load,
remove loads, calculate the difference of the indentions
Rockwell Hardness Testing (Indentors) - Answers :1/16" Tungsten Carbide Ball for B&T
120 degree Diamond Cone or Brale for C, A, & N (EX: HRC)
Rockwell Regular loads - Answers :Minor: 10 kg
Major: 60kg, 100kg, 150kg
Rockwell Superficial loads - Answers :Minor: 3kg
Major: 15kg, 30 kg, 45kg
What does a major load mean? - Answers :Load that makes the second indention
Differences between regular and superficial loads - Answers :regular - prefer to use this
superficial - use if material is really thin or soft
Rockwell: difference between Beuler and Wilson? - Answers :They are just different
brands, same type of rockwell hardness test
Brinell Hardness Test - Answers :Uses 10mm ball as indentor
Smash ball into metal surface and measure diameter of the indention
What are the mechanical properties of metals? - Answers :- strength
- formability
- stiffness
- toughness
- durability
Strength - Answers :Material's ability to accommodate stress
Properties of Strength (6) - Answers :- tensile
- yield
- compression
- flexural
- shearc
- creep
Formability - Answers :The easiness to shape a metal; can I bend this w/o breaking it?
Properties of Formability (3) - Answers :- % elongation
- % reduction in area
, - bend radius
Toughness - Answers :The energy required to fracture the volume of a material
(measured in foot pounds)
Properties of Toughness (2) - Answers :- impact strength
- notch sensitivity
Durablilty - Answers :Wear resistance
Properties of Durability - Answers :- Hardness
- Wear resistance
- Fatigue strength
Stress - Answers :-A force distributed over an area or object
-Stress = F/Ao
-Units: (lb/in2) or (psi or ksi) or (N/m2)
Strain - Answers :-Percentage size change of a material in a particular direction when
subjected to a force in that direction
-Strain (Es) = Lf - Lo / Lo
-Units: none or (in/in) or (m/m)
Ultimate tensile strength - Answers :The maximum stress that can be applied to a
material before it breaks
Elastic limit/Yield Point - Answers :point where a material goes from elastic to plastic;
last point on linear part of graph
Break point - Answers :End of plastic behavior; where a material breaks
What is 0.2% offset yield (Engineering yield strength) - Answers :the stress at which a
material exhibits a specified deviation from proportionality of stress/strain. Also, it hard
to determine precisely so yield point is considered at an offset strain of 0.2%
How to find 0.2% offset yield - Answers :determining .002 strain and traveling parallel to
modulus of elasticity
Modulus of Elasticity
(What is it?, formula, where on stress/strain curve, tell about the material?) - Answers :-
A measure of rigidity ( or stiffness)
- Slope of linear line
- delta stress/ delta strain (Es)
- tells a material's stiffness
Modulus of Elasticity of Steel - Answers :E(steel) = 30x10^6 psi
