This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Behaviour in Metal Forming”.
1. Which of the following can help in determining the behaviour of the material in metal forming?
a) Size of material
b) Shape of material
c) Stress-strain curve
d) Color of material
View Answer
Explanation: The behaviour of materials during metal forming can be determined by the stress-strain curve. The stress-strain curve for most of the materials is divided into an elastic region and a plastic region. In metal forming, the plastic region is the main consideration because the material is plastically deformed during the forming process.
2. A general stress-strain curve of any material represents the plasticity below the yield point.
a) True
b) False
View Answer
Explanation: In the stress-strain curve of any material exhibits plasticity or strain hardening above the yield point. And below the yield point, the area represents the elasticity of the material. Yield point is only present in the stress-strain curve of ductile materials. In brittle materials, yielding does not take place during the application of load; it directly shows the fracture failure.
3. Flow stress is defined as the instantaneous value of stress required to continue the deformation of metal.
a) True
b) False
View Answer
Explanation: Flow stress is generally defined as the instantaneous value of stress which is required to continue the deformation of metal, which means to keep the material flowing. It is also defined as the yield strength of the material as a function of strain, or the strength that determines the forces required to complete a specific forming operation.
4. The mechanical strength of the metal decreases due to the strain hardening of the metal.
a) True
b) False
View Answer
Explanation: At room temperature, the stress-strain curve of most of the materials indicates the deformation of metal. When deformation occurs, the mechanical strength increases due to the strain hardening. The stress needed for continuing the deformation should be increased to match this increase in strength.
5. By keeping the metal at higher temperature, its ductility increases with the decrease in its strength.
a) True
b) False
View Answer
Explanation: By keeping the metal at higher temperature, both the strength and strain hardening of the metal decreases. And the ductility is increased at the higher temperature. These changes are very important and essential so that any deforming operation can be easily accomplished by lower forces at high temperatures.
6. Better accuracy and surface finish is achieved by performing hot forming process instead of the cold forming process.
a) True
b) False
View Answer
Explanation: Cold forming is a metal forming process that is performed at room temperature or slightly above. It has many advantages like better surface finish, high accuracy, high strength etc. And by performing hot forming operation, the surface finish of the part is very poor, which requires heavy machining to finish the metal part.
7. In cold forming process, the fuel cost is very less as compared to that in the hot forming process.
a) True
b) False
View Answer
Explanation: In cold forming process, not much heating is required, which generally saves the fuel costs and permits higher production rate of the metal parts. And in hot forming process, the metal is subjected to very high temperature that requires lot of fuel to generate enough heat, which increases the overall cost of the hot forming operation.
8. The extent of plastic deformation of material is mainly dependent on its grain structure.
a) True
b) False
View Answer
Explanation: In the metal forming processes, the extent of plastic deformation of the material is mainly dependent on its grain structure. The deformation of metal also depends on the nature of bonding, surrounding temperature and defects like dislocation which might be present in the material during the metal forming process.
9. In general, the coefficient of friction is very low in the metal forming processes.
a) True
b) False
View Answer
Explanation: In metal forming processes, the coefficient of friction is very high. Due to this, it leads to a condition which is called as sticking friction. In this case, the surface shear stress increases the shear yield strength of the metal and the surfaces adhere to each other. In the forming operation, the metal beneath the surface experiences shear deformation.
10. In metal forming processes, the temperature rise also depends on the rate of deformation of the material.
a) True
b) False
View Answer
Explanation: In general, the temperature rise of any material is determined by using the stress-strain plot. The temperature rise also depends on the rate of deformation of the material. For slow deformation, the temperature rise of the metal is small as the heat induced gets dissipated through the surrounding air during the process.
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