Chapter – 1

Questions zone

Answer all the questions precisely to the point.

Set-1

1. Define homogeneous material and isotropic material.

2. Define the modulus of elasticity E.

3. At room temperature, mild steel is a ductile material. State true or false?

4. As the temperature increases the modulus of elasticity will increase. State true or false?

5. Define shear strain and Poisson’s ratio. Give the values of poison’s ratio for structural materials. Can the Poisson’s ratio have a negative value? If so explain and give an example.

Set-2

1. Distinguish true stress and engineering stress. Give relation.

2. Distinguish true strain and engineering strain. Give relation.

3. What do you mean by true stress strain curve? Why the true stress strain curve of the steel is not used in the design? Explain elaborately.

4. What do you mean by strain hardening?

5. What is strain softening?

6. What do you mean by permanent set?

7. Explain briefly the difference between the proportionality limit and elastic limit.

8. What is ductility? What is malleability? Give examples for ductile and malleable materials.

9. Does the carbon content influence the strength and ductility in steel?

10. What do you mean by upper yield point and lower yield point?

Set-3

1. How do you determine the yield stress in aluminium?

2. Why HYSD steel does not have a definite yield point?

3. What do you mean by proof stress?

4. What do you mean by a brittle material? Explain with stress strain curve. Give some examples.

5. Explain the terms creep, relaxation and fatigue.

6. Draw the stress strain curve for mild steel when it subjected to tension and compression. Do both look alike? Is there any significant reason for not using stress strain curve in compression?

7. Explain briefly why the true stress in compression is lower than the nominal stress?

8. Give a greater than or less than or equal to relationship for the true ultimate stress and nominal fracture stress for a brittle material subjected to tension. Explain briefly why.

9. Draw and explain briefly the stress strain curve for glass subjected to tension.

10. Explain the terms elasticity and plasticity.

Set-4

State whether the following statements are true or false and justify your answer briefly in a point.

1. You can measure stress directly with an instrument that you measure your temperature by a thermometer.

2. There can only be one normal stress component acting on the surface of an imaginary cut.

3. If a shear stress component on the left surface of an imaginary cut is upward, then on the right side it will be downward.

4. If a normal stress component puts the left surface of an imaginary cut in tension, then the right surface will be in compression.

5. Stress on the surface is same as the pressure on a surface as both the quantities have the same units.

Set-5

1. What is the difference between proportionality limit and yield point?

2. What is the difference between the linear material behaviour and elastic material behaviour?

3. What is the difference between strain energy and strain energy density?

4. What is resilience? What is proof resilience? What is the difference between modulus of resilience and modulus of toughness?

5. What is the difference between a strong material and tough material? Explain using curves.

6. What is elastic strain, offset strain and plastic strain?

7. What is the difference between displacement and deformation?

8. Is the value of E always greater than G, less than G, or does it depends on the material? Justify your answer.

9. What is the number of independent material constants needed in a linear stress strain relationship for an isotropic and an anisotropic material?

10. Explain briefly stress concentration.