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?
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?
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?
Why does the engineering stress-strain curve fall after its peak?
The answer is: The section is necking, and stress is still being computed on the original area
The answer is: The section is necking, and stress is still being computed on the original area
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?
What is the 0.2 per cent proof stress?
The answer is: The stress that leaves 0.2 per cent permanent strain, used where there is no sharp yield point
The answer is: The stress that leaves 0.2 per cent permanent strain, used where there is no sharp yield point
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?
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?
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?
Which statements distinguish a brittle material from a ductile one?
Select all that apply
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.
A member checked against yield with a factor of safety of 1.5 is thereby protected against fatigue failure.
The answer is: False
9.[3p] Why do modern codes apply separate partial factors to permanent and variable loads?
Why do modern codes apply separate partial factors to permanent and variable loads?
The answer is: The two are known to different accuracies, so one margin for both is either wasteful or unsafe
The answer is: The two are known to different accuracies, so one margin for both is either wasteful or unsafe
The answer is: The two are known to different accuracies, so one margin for both is either wasteful or unsafe