Quiz 3

Question 1

What is the definition of Yield Strength?

Answer 1

The stress after which material deform plastically.

Question 2

What happens to the material after necking point in the tensile curve?

Answer 2

Material deforms inhomogenesously.

Question 3

Material A has Young´s modulus of 100GPa and material B has Young´s modulus of 50 GPa. Which material is stiffer?

Answer 3

A

Question 4

If we deform a metal plastically at room temperature and unload it before fracture, what happens to the Yield strength (YS) if we deform it again at room temperature? and why?

Answer 4

YS increases due to work hardening

Question 5

What is the difference between toughness and stiffness?

Answer 5

Thoughness is the energy required to fracture a material but stiffness is the resistance to elastic deformation.

Question 6

In plastic region, the True Stress value is normally [—–] than/as the engineering stress.

Answer 6

higher

Question 7

During the fatigue testing, at relatively high stresses (low fatigue life), which parameter is the main dominant factor for determining the fatigue life?

Answer 7

Crack propagation

Question 8

What is the meaning of fatigue limit (endurance) in S-N curves.

Answer 8

The stress level, below which material has fatigue life-time of infinity.

Question 9

What is the effect of mean stress on fatigue life?

Answer 9

Fatigue life decreases with increasing the mean stress.

Question 10

What is the definition of low cycle fatigue?

Answer 10

Low number of cycle to failure.