Lesson test: Yielding and safety

1.[2p]
A tensile specimen of 12.5 mm diameter reaches a maximum load of 56 kN. What is its ultimate tensile strength, in MPa?

CorrectNot quite: 456

3.[2p]
Why does the engineering stress-strain curve fall after its peak?

The section is necking, and stress is still being computed on the original area

Correct

The material is softening as it is pulled

The answer is: The section is necking, and stress is still being computed on the original area

The testing machine loses grip on the specimen

The answer is: The section is necking, and stress is still being computed on the original area

The strain rate increases past the peak

The answer is: The section is necking, and stress is still being computed on the original area

4.[2p]
What is the 0.2 per cent proof stress?

The stress that leaves 0.2 per cent permanent strain, used where there is no sharp yield point

Correct

The stress at which a material has stretched by 0.2 per cent in total

The answer is: The stress that leaves 0.2 per cent permanent strain, used where there is no sharp yield point

The stress at 0.2 per cent of the ultimate strength

The answer is: The stress that leaves 0.2 per cent permanent strain, used where there is no sharp yield point

The largest stress at which the material is still perfectly elastic

The answer is: The stress that leaves 0.2 per cent permanent strain, used where there is no sharp yield point

5.[3p]
A tie carries 200 kN and is made from S355 steel with a factor of safety of 1.5 on yield. What cross-sectional area is required, in mm²?

CorrectNot quite: 845

6.[3p]
A simply supported beam of 6 m span carries 12 kN per metre of permanent load and 18 kN per metre of variable load. Using partial factors of 1.35 and 1.5, what is the design bending moment in kN m?

CorrectNot quite: 194.4

7.[3p]
Which statements distinguish a brittle material from a ductile one?

Select all that apply

It is far stronger in compression than in tension

Correct

Its strength is scattered, because it is set by the worst flaw present

Correct

It is acutely sensitive to notches and sharp corners

Correct

It absorbs more energy before fracture

The answer is: It is far stronger in compression than in tension, Its strength is scattered, because it is set by the worst flaw present, It is acutely sensitive to notches and sharp corners

8.[2p]
A member checked against yield with a factor of safety of 1.5 is thereby protected against fatigue failure.

True

The answer is: False

False

Correct

9.[3p]
Why do modern codes apply separate partial factors to permanent and variable loads?

The two are known to different accuracies, so one margin for both is either wasteful or unsafe

Correct

Permanent loads act for longer and so cause more damage

The answer is: The two are known to different accuracies, so one margin for both is either wasteful or unsafe

Variable loads are always larger than permanent ones

The answer is: The two are known to different accuracies, so one margin for both is either wasteful or unsafe

It makes the arithmetic simpler than a single factor

The answer is: The two are known to different accuracies, so one margin for both is either wasteful or unsafe

Sign in

Yielding and safety

1.[2p]
A tensile specimen of 12.5 mm diameter reaches a maximum load of 56 kN. What is its ultimate tensile strength, in MPa?

2.[2p]
A specimen with a 50 mm gauge length measures 62 mm after fracture. What is the percentage elongation?

3.[2p]
Why does the engineering stress-strain curve fall after its peak?

4.[2p]
What is the 0.2 per cent proof stress?

5.[3p]
A tie carries 200 kN and is made from S355 steel with a factor of safety of 1.5 on yield. What cross-sectional area is required, in mm²?

6.[3p]
A simply supported beam of 6 m span carries 12 kN per metre of permanent load and 18 kN per metre of variable load. Using partial factors of 1.35 and 1.5, what is the design bending moment in kN m?

7.[3p]
Which statements distinguish a brittle material from a ductile one?

8.[2p]
A member checked against yield with a factor of safety of 1.5 is thereby protected against fatigue failure.

9.[3p]
Why do modern codes apply separate partial factors to permanent and variable loads?

1.[2p] A tensile specimen of 12.5 mm diameter reaches a maximum load of 56 kN. What is its ultimate tensile strength, in MPa?

2.[2p] A specimen with a 50 mm gauge length measures 62 mm after fracture. What is the percentage elongation?

3.[2p] Why does the engineering stress-strain curve fall after its peak?

4.[2p] What is the 0.2 per cent proof stress?

5.[3p] A tie carries 200 kN and is made from S355 steel with a factor of safety of 1.5 on yield. What cross-sectional area is required, in mm²?

6.[3p] A simply supported beam of 6 m span carries 12 kN per metre of permanent load and 18 kN per metre of variable load. Using partial factors of 1.35 and 1.5, what is the design bending moment in kN m?

7.[3p] Which statements distinguish a brittle material from a ductile one?

8.[2p] A member checked against yield with a factor of safety of 1.5 is thereby protected against fatigue failure.

9.[3p] Why do modern codes apply separate partial factors to permanent and variable loads?

1.[2p]
A tensile specimen of 12.5 mm diameter reaches a maximum load of 56 kN. What is its ultimate tensile strength, in MPa?

2.[2p]
A specimen with a 50 mm gauge length measures 62 mm after fracture. What is the percentage elongation?

3.[2p]
Why does the engineering stress-strain curve fall after its peak?

4.[2p]
What is the 0.2 per cent proof stress?

5.[3p]
A tie carries 200 kN and is made from S355 steel with a factor of safety of 1.5 on yield. What cross-sectional area is required, in mm²?

6.[3p]
A simply supported beam of 6 m span carries 12 kN per metre of permanent load and 18 kN per metre of variable load. Using partial factors of 1.35 and 1.5, what is the design bending moment in kN m?

7.[3p]
Which statements distinguish a brittle material from a ductile one?

8.[2p]
A member checked against yield with a factor of safety of 1.5 is thereby protected against fatigue failure.

9.[3p]
Why do modern codes apply separate partial factors to permanent and variable loads?