Identify the correct statements from the following: P. 0.2% yield strength of a material implies 0.2% of the yield strength. Q. Von-Misses yield criterion implies that yielding occurs when the distortion energy reaches a critical value. R. Radius of the cylinderical Von-Misses yield surface increases as the grain, size of a single phase material decreases. S. Tresca's yield criterion gives a circular cylinderical surface in the space of the three principal stresses.

Tresca or maximum-shear stress criteria assumes that yielding occurs when the maximum shear stress reaches a value of the shear stress in the uniaxial tension test. Assume the principal stress being σ1, σ2, σ3 where σ1 is largest, and σ3 is the smallest principal stresses. Find the value of minimum shear stress to cause yielding, given that yield stress in tension is equal to σo?

A

τ = σo

B

τ = σo/2

C

τ = σo/3

D

τ = σo/4

A body starts yielding when it is subjected to stress state with principal stresses of 250 MPa, 50 MPa and - 50 MPa. What is the yield strength of the material. in MPa, if Tresca yield criterion is obeyed?

A

100

B

200

C

300

D

400

In order to double its yield strength, the grain size of a steel of ASTM grain size number 2 should be changed to ASTM grain size number (neglect friction stress)

A

1

B

4

C

6

D

8

The largest size of immobilised segment of dislocation in a Frank Read (FR) source contained in a polycrystalline material is of the order of grain size. In a metal of 10 μm grain size, the shear stress required to operate such a FR source is 100 MPa. If the grain size in the same metal is reduced to 10 μm, the shear stress required to operate such FR source would be . . . . . . . . MPa.

A

102

B

103

C

105

D

106

Stress analysis of structural material for the submarine gives the state of stress as shown in the figure. The yield strength of the material is 450 MPa. Using Von-mises yielding criteria determine whether yielding will occur or not? If not, what is the factor of safety?

A

Yielding will not occur

B

Yielding will occur, and the factor of safety is 2.5

C

Yielding will occur, and the factor of safety is 1.53

D

Yielding will occur, and the factor of safety is 1.28

Stress analysis of structural material for the submarine gives the state of stress as shown in the figure. The yield strength of the material is 450 MPa. Using Tresca’s yielding criteria determine whether yielding will occur or not? If not, what is the factor of safety?

A

Yielding will not occur

B

Yielding will occur, and the factor of safety is 1.125

C

Yielding will occur, and the factor of safety is 1.53

D

Yielding will occur, and the factor of safety is 1.28

Physical Meaning of von-mises yielding criteria is that yielding occurs when the _____________ reaches a critical value.

A

distortion energy

B

strain energy

C

potential energy

D

kinetic energy

The effect of grain size on the fatigue strength is predominant in material with high stacking fault energy while the effect of grain size is negligible in low stacking fault energy material.

A

True

B

False

In the following sentence the word principal' occurs three times "The principal (1) aim of the principal (2) of the college was to help build new roads to link the area's principal (3)schools" Indicate the use(s) in which the meaning of the word “Principal is ‘chief or main',

A

Use (1)

B

Use(2)

C

Use (3)

D

Both (1) & (3)

For a cylinderical vessel of moderate height, the weld joint efficiency for joints parallel to the cylinderical axis is given as 1.0, while for joints along the girth (circumference) it is given as 0.8. In calculating the shell wall thickness using code formula for an internally pressurised cylinderical vessel, what value of weld joint efficiency should be used?

A

0.8

B

0.9

C

1.0

D

(0.8)0.5