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Topic: Solid Mechanics

Problem Statement:Write short notes on the following:1. Elastic Deformation2. Plastic deformation3. True Stress4. True Strain5. Stress-Strain Curve6. Ductility© e-Assignmenthelp, 2014

Topic: Solid Mechanics

Problem Statement:Write short notes on the following:7. Charpy Test8. Slip9. Effect of cold working on material properties10.Effect of thermal annealing on material

properties11.Ductile Fracture12.Brittle Fracture© e-Assignmenthelp, 2014

Topic: Solid Mechanics

Problem Statement:Write short notes on the following:13.S-N Fatigue Curve14.Creep15. Isostress strain curve16.Isothermal strain curve

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Solutions:1. Elastic deformation is said to have occurred when the

deformation undergone by the object is reversible. In elastic deformation, the atomic bonds within the material under stress are stretched, but the relative configurations of the atoms are not changed.

2. Plastic deformation is the opposite of elastic deformation, i.e. the deformation undergone by the object is permanent. In plastic deformation, when the material is subjected to sufficient force (stress), the atoms slip past each other or the bonds may break down.

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Solutions:3. True stress is the instantaneous stress, determined by the

ratio of the instantaneous force to the effective instantaneous area.

4. True strain is defined as the instantaneous error in the change of length of the material, when subjected to a force.

5. Stress-strain curve:

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Solutions:6. Ductility is the mechanical property of a material. Ductility is

a measure of how much the material can be deformed by a deforming force before undergoing plastic failure (fracture).

7. The Charpy Test measures the Brittle-Ductile Transition Temperature (BDTT) of a material ,based on which the energy required to fracture a material can be quantitatively estimated. Its unit is K (Kelvin).

8. A slip occurs in a material when a dislocation in the relative configuration of atoms of the material causes a plastic deformation. Thus, a slip can also be called a permanent deformation in a material under the action of a force.

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Solutions:9. Cold working

i. Increases the yield strength ii. Increases the tensile strength iii. Decreases the ductilityiv. Increases the hardness

10. Thermal Annealingi. Decreases the yield strength ii. Decreases the tensile strength iii. Increases the ductility iv. Decreases the hardness

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Solutions:11. Ductile fracture is caused by extensive plastic deformation of

the material before appearance of the ‘crack’. In ductile fracture, the crack is stable, i.e. it resists further elongation unless the deforming stress is increased.

12. Brittle fracture is characterized by relatively little plastic deformation before the ‘crack’ appears in the material. In brittle deformation, the crack is prone to extension even without any increase in the deforming stress.

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Solutions:13. In an S-N fatigue curve, S is the applied stress and N refers to the number of cycles of stress.

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Solutions:14. Creep is defined as the process of time-dependent

deformation at temperatures greater than half of the absolute melting point temperature. It is measured on the Kelvin scale.

15. The time-dependent strain curve for the same value of stress and varying temperature is given by:

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Solutions:16. The time-dependent strain curve for different values of stress and isothermal conditions is given by:

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