OPOWER ENGINEERING - 2A2
(CHAPTER 5) QUESTIONS AND 100%
CORRECT VERIFIED ANSWERS /GRADE
A
What are the two main categories of material testing? - Destructive testing
Non-destructive testing / Non-destructive examination (NDE)
What are the four methods of destructive testing? - Tensile Tests
Hardness Tests
Impact Tests
Proof Tests
In a tensile test, how is the shape of the specimen determined? - The shape is defined by the standards
established by ASTM
In a tensile test, why is the shape of the specimen important? - So that the beak occurs in the "gauge
length" section.
What is the mechanism called that is used for performing tensile tests? - An extensometer
When performing tensile tests, what are the five stress points plotted? - Proportional Limit
Yield stress
Proof Stress
Ultimate tensile Strength
,Final instability point
What is the proportional limit as it pertains to tensile tests? - The stress point at which slip (or glide) due
to dislocation movement occurs.
What is yield stress as it pertains to tensile tests? - The stress at which yielding occurs across the whole
specimen.
At this point, deformation is purely plastic (non-reversible)
What is proof stress as it pertains to tensile tests? - The point at which a specimen has undergone a
certain value of permanent strain. Usually 0.2%
What is the ultimate tensile strength (UTS) as it pertains to tensile tests? - It is the point at which plastic
deformation becomes unstable and a narrow region (a neck) forms in the specimen.
What is the final instability point as it pertains to tensile tests? - It is the failure point, at which fracture
occurs.
What are the two main types of strain? - Elastic strain
Plastic strain
Explain elastic strain - Elastic strain is the stretching of material within its elastic limit. It will return to its
original dimensions when the stress is removed.
Explain plastic strain - Plastic strain happens once the material has exceeded its elastic limit. It is the
irreversible deformation of a material.
What is engineering strain? - This is the one outlined in the academic supplement.
Strain=ΔL/Original L
, What is true strain? - It is similar to engineering strain but based on the instantaneous length of the
specimen as the test progresses.
Instantaneous length
True Strain = ln --------------------------
Original length
What is the hardness measurement? - The resistance of a material to surface indentation.
What are the four common hardness testing methods? - Brinell
Rockwell
Vickers
Knoop
Describe the Brinell Hardness Test. - Specimen placed on an anvil
Load applied through a plunger and ball
Held for 10 to 30 seconds
Diameter measured twice offset by 90° to get mean diameter
Hardness number calculated
What is the most widely used hardness test? Why? - The Rockwell hardness test
Because it's simple to perform
What do Rockwell hardness testers use as an indentor? - Either a diamond cone or ball
What are the letters that follow the numerical value for a Rockwell hardness test? What do they mean? -
1234 H R (B or C)
(CHAPTER 5) QUESTIONS AND 100%
CORRECT VERIFIED ANSWERS /GRADE
A
What are the two main categories of material testing? - Destructive testing
Non-destructive testing / Non-destructive examination (NDE)
What are the four methods of destructive testing? - Tensile Tests
Hardness Tests
Impact Tests
Proof Tests
In a tensile test, how is the shape of the specimen determined? - The shape is defined by the standards
established by ASTM
In a tensile test, why is the shape of the specimen important? - So that the beak occurs in the "gauge
length" section.
What is the mechanism called that is used for performing tensile tests? - An extensometer
When performing tensile tests, what are the five stress points plotted? - Proportional Limit
Yield stress
Proof Stress
Ultimate tensile Strength
,Final instability point
What is the proportional limit as it pertains to tensile tests? - The stress point at which slip (or glide) due
to dislocation movement occurs.
What is yield stress as it pertains to tensile tests? - The stress at which yielding occurs across the whole
specimen.
At this point, deformation is purely plastic (non-reversible)
What is proof stress as it pertains to tensile tests? - The point at which a specimen has undergone a
certain value of permanent strain. Usually 0.2%
What is the ultimate tensile strength (UTS) as it pertains to tensile tests? - It is the point at which plastic
deformation becomes unstable and a narrow region (a neck) forms in the specimen.
What is the final instability point as it pertains to tensile tests? - It is the failure point, at which fracture
occurs.
What are the two main types of strain? - Elastic strain
Plastic strain
Explain elastic strain - Elastic strain is the stretching of material within its elastic limit. It will return to its
original dimensions when the stress is removed.
Explain plastic strain - Plastic strain happens once the material has exceeded its elastic limit. It is the
irreversible deformation of a material.
What is engineering strain? - This is the one outlined in the academic supplement.
Strain=ΔL/Original L
, What is true strain? - It is similar to engineering strain but based on the instantaneous length of the
specimen as the test progresses.
Instantaneous length
True Strain = ln --------------------------
Original length
What is the hardness measurement? - The resistance of a material to surface indentation.
What are the four common hardness testing methods? - Brinell
Rockwell
Vickers
Knoop
Describe the Brinell Hardness Test. - Specimen placed on an anvil
Load applied through a plunger and ball
Held for 10 to 30 seconds
Diameter measured twice offset by 90° to get mean diameter
Hardness number calculated
What is the most widely used hardness test? Why? - The Rockwell hardness test
Because it's simple to perform
What do Rockwell hardness testers use as an indentor? - Either a diamond cone or ball
What are the letters that follow the numerical value for a Rockwell hardness test? What do they mean? -
1234 H R (B or C)
