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# Materials Science MCQ’s – Fracture Mechanics

1 - Question

Which of the following part of mechanics deals with study of crack propagation?

a) Solid mechanics

b) Fluid mechanics

c) Applied mechanics

d) Fracture mechanics

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Answer: dExplanation: Fracture mechanics is that part of mechanics which deals with the study of propagation of cracks. Solid mechanics and fluid mechanics deal with solid body and fluid respectively.

2 - Question

Which of the following is not a mode of application of force for crack propagation? a) Opening mode b) Sliding mode c) Tearing mode d) Rolling mode

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Answer: dExplanation: The application of force for the crack to propagate can be mainly of three types which are opening mode, tearing mode, sliding mode. Rolling mode cannot be used.

3 - Question

Fractography is the study of surfaces of materials which are fractured

a) True

b) False

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Answer: aExplanation: The above statement is true and fractography is indeed the study of surfaces of materials which are fractured. They are used mainly in forensic engineering or during failure analysis.

4 - Question

What amount of actual stress would be needed to fracture bulk glass?

a) 10 MPa

b) 20 MPa

c) 100 MPa

d) 50 MPa

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Answer: cExplanation: To fracture bulk glass, a force of about 100 Mpa or 15000 psi would be needed.

5 - Question

What amount of actual stress would be needed to fracture bulk glass?

a) 1000 MPa

b) 2000 MPa

c) 10000 MPa

d) 5000 MPa

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Answer: cExplanation: To fracture bulk glass, theoretically the stress needed to break the atomic bonds of the glass would be 10000 Mpa or 1500000 psi.

6 - Question

According to Griffith if f is stress at fracture and a is flaw length then which of the following is true?

a) f*a1/2

b) f*a

c) f/a

d) f/a1/2

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Answer: aExplanation: Griffith on conducting his experiment found out that the multiplication of stress at fracture and the square root of the flaw length remains constant.

7 - Question

Which of the following scientist proposed a modification to Griffith’s theory?

a) G. R. Irwin

b) Albert Einstein

c) Isaac Newton

d) There was no modification proposed.

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Answer: aExplanation: G. R. Irwin and people working under him at the U.S. Naval Research Laboratory found out that plasticity also plays a role in fracture of material and hence they proposed a modification.

8 - Question

What is the unit of G from Griffith’s energy criterion?

a) J-m2

b) J-m

c) J/m2

d) J/m

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Answer: cExplanation: G is the surface energy and is the given by energy per unit area which can be found out by dividing J by m2 to get the final answer as J/m2.

9 - Question

For polymers close to glass transition temperature which of the following can be a value of G?

a) 1 J/m2

b) 900 J/m2

c) 1200 J/m2

d) 1400 J/m2

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Answer: bExplanation: 900 J/m2 can be value of G for polymers close to glass transition temperature as the range of the G for this case is known to be 2 J/m2 to 1000 J/m2. As the other options lie out of this range, there is only one correct answer.

10 - Question

Fracture stress decreases as fiber diameter decreases.

a) True

b) False

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Answer: bExplanation: The above statement is false as the fracture strength is known to increase when the fiber diameter decreases as observed by Griffith.