Lesson test: Combined stress

1.[3p]
A masonry pier is 600 mm deep. How far from the centroid may an axial load act before tension appears at the far face, in mm?

CorrectNot quite: 100

2.[2p]
Why can an axial stress and a bending stress simply be added, while an axial stress and a shear stress cannot?

The first pair act in the same direction on the same plane, and the second pair do not

Correct

Bending stress is always smaller than axial stress

The answer is: The first pair act in the same direction on the same plane, and the second pair do not

Shear stresses are not real stresses, only reactions

The answer is: The first pair act in the same direction on the same plane, and the second pair do not

Superposition applies only to moments

The answer is: The first pair act in the same direction on the same plane, and the second pair do not

3.[3p]
At a point, $σ_{x} = 100$ MPa, $σ_{y} = 20$ MPa and $τ_{x y} = 40$ MPa. What is the larger principal stress, in MPa?

CorrectNot quite: 116.6

5.[3p]
A point carries a normal stress of 60 MPa and a shear stress of 40 MPa. What is the von Mises equivalent stress, in MPa?

CorrectNot quite: 91.7

6.[3p]
A point is in pure shear of magnitude $τ$ . What are its principal stresses?

$+ τ$ and $- τ$ , on planes at 45 degrees to the shear planes

Correct

$τ$ and zero, on the shear planes themselves

The answer is: $+\tau$ and $-\tau$, on planes at 45 degrees to the shear planes

Both zero, since there is no normal stress anywhere

The answer is: $+\tau$ and $-\tau$, on planes at 45 degrees to the shear planes

$2 τ$ and zero, on planes at 45 degrees

The answer is: $+\tau$ and $-\tau$, on planes at 45 degrees to the shear planes

7.[3p]
A stick of chalk twisted until it breaks fails on a helical surface at 45 degrees. Why?

Chalk is brittle and fails on the plane of maximum tensile stress, which lies at 45 degrees to the axis

Correct

Chalk is ductile and fails on the plane of maximum shear

The answer is: Chalk is brittle and fails on the plane of maximum tensile stress, which lies at 45 degrees to the axis

The helix is where the torque is largest

The answer is: Chalk is brittle and fails on the plane of maximum tensile stress, which lies at 45 degrees to the axis

Chalk has a natural grain running at 45 degrees

The answer is: Chalk is brittle and fails on the plane of maximum tensile stress, which lies at 45 degrees to the axis

8.[2p]
The Tresca criterion is always at least as conservative as the von Mises criterion.

True

Correct

False

The answer is: True

9.[3p]
Which statements about Mohr's circle are correct?

Select all that apply

Its centre is at the average of the two normal stresses

Correct

Its radius equals the maximum shear stress at the point

Correct

Rotating the cutting plane by an angle moves the point round the circle by twice that angle

Correct

Its radius is zero for a state of pure shear

The answer is: Its centre is at the average of the two normal stresses, Its radius equals the maximum shear stress at the point, Rotating the cutting plane by an angle moves the point round the circle by twice that angle

Sign in

Combined stress

1.[3p]
A masonry pier is 600 mm deep. How far from the centroid may an axial load act before tension appears at the far face, in mm?

2.[2p]
Why can an axial stress and a bending stress simply be added, while an axial stress and a shear stress cannot?

3.[3p]
At a point, $σ_{x} = 100$ MPa, $σ_{y} = 20$ MPa and $τ_{x y} = 40$ MPa. What is the larger principal stress, in MPa?

4.[3p]
For the same point, what is the maximum shear stress, in MPa?

5.[3p]
A point carries a normal stress of 60 MPa and a shear stress of 40 MPa. What is the von Mises equivalent stress, in MPa?

6.[3p]
A point is in pure shear of magnitude $τ$ . What are its principal stresses?

7.[3p]
A stick of chalk twisted until it breaks fails on a helical surface at 45 degrees. Why?

8.[2p]
The Tresca criterion is always at least as conservative as the von Mises criterion.

9.[3p]
Which statements about Mohr's circle are correct?

1.[3p] A masonry pier is 600 mm deep. How far from the centroid may an axial load act before tension appears at the far face, in mm?

2.[2p] Why can an axial stress and a bending stress simply be added, while an axial stress and a shear stress cannot?

3.[3p] At a point, σx=100 MPa, σy=20 MPa and τxy=40 MPa. What is the larger principal stress, in MPa?

4.[3p] For the same point, what is the maximum shear stress, in MPa?

5.[3p] A point carries a normal stress of 60 MPa and a shear stress of 40 MPa. What is the von Mises equivalent stress, in MPa?

6.[3p] A point is in pure shear of magnitude τ. What are its principal stresses?

7.[3p] A stick of chalk twisted until it breaks fails on a helical surface at 45 degrees. Why?

8.[2p] The Tresca criterion is always at least as conservative as the von Mises criterion.

9.[3p] Which statements about Mohr's circle are correct?

1.[3p]
A masonry pier is 600 mm deep. How far from the centroid may an axial load act before tension appears at the far face, in mm?

2.[2p]
Why can an axial stress and a bending stress simply be added, while an axial stress and a shear stress cannot?

3.[3p]
At a point, $σ_{x} = 100$ MPa, $σ_{y} = 20$ MPa and $τ_{x y} = 40$ MPa. What is the larger principal stress, in MPa?

4.[3p]
For the same point, what is the maximum shear stress, in MPa?

5.[3p]
A point carries a normal stress of 60 MPa and a shear stress of 40 MPa. What is the von Mises equivalent stress, in MPa?

6.[3p]
A point is in pure shear of magnitude $τ$ . What are its principal stresses?

7.[3p]
A stick of chalk twisted until it breaks fails on a helical surface at 45 degrees. Why?

8.[2p]
The Tresca criterion is always at least as conservative as the von Mises criterion.

9.[3p]
Which statements about Mohr's circle are correct?