MCQ’s On Mechanical Working of Metals
Q. Which of the following forming Processes is suitable for making utensils and cup shaped objects?
A. Forging
B. Rolling
C. Deep drawing
D. Wire drawing
.
.Answer: C
Explanation: Process Deep drawing Process is also known as cup drawing, which is a part of sheet metal forming Process. It is widely used for making products like utensils, cup shaped objects, pressure vessels, gas cylinders, cans etc. In this method, a blank is placed on a die cavity and then held in a position using a holding plate and pressed against the die cavity by using a punch.
Q. In the deep drawing Process, a clearance is provided between the punch and die to succeed the forming operation.
A. True
B. False
.
.Answer: A
Explanation: Process During deep drawing operation of metal sheet into the die, there is thickening of the metal sheet up to 12%. Therefore, a clearance is provided between the punch and die to succeed the forming operation. The radial clearance is provided which is almost equal to the thickness of metal sheet plus the thickening of sheet.
Q. Deep drawing Process can also be possible by having shearing operation instead of bending operation.
A. True
B. False
.
.Answer: B
Explanation: Process Shearing operations like blanking or punching basically includes cutting of metal sheet, which does not required in deep drawing Process. In deep drawing, the flat section of the metal sheet under the holding plate moves towards the die axis and then bending occurs over the die profile. After bending, the metal sheet unbends to flow in downward direction along the side wall.
Q. In deep or cup drawing, maximum tensile stress is caused near the end of punch.
A. True
B. False
.
.Answer: A
Explanation: Process In deep or cup drawing, the tensile stress is generally generated on the sheet at several locations within the die cavity. Maximum tensile stress is induced near the end of punch, at the profile of punch, because the metal sheet bends over the edge of punch due to inducing of tensile stresses in the punch.
Q. Necking phenomena do not occur in the Process of a cup or deep drawing.
A. True
B. False
.
.Answer: B
Explanation: Process In deep drawing, necking of metal sheet is a very common phenomena, which occurs near the punch profile due to inducement of tensile stresses in the punch material. The metal sheet under the holding plate experiences compressive hoop stresses and radial tensile stresses due to blank holding plate. In this method, thickness of the cup wall generally increases from the bottom side to the top side.
Q. In metal forming, deep drawing Process is completely different from wire drawing Process.
A. True
B. False
.
.Answer: A
Explanation: Process Deep drawing Process is completely different from wire drawing Process. In wire drawing, metallic bar is pulled to form wires, while in deep drawing Process; a flat metal sheet is converted into a concave shape part. This operation is basically performed by stretching the metal for which a blank-holder is used to clamp the blank on the die, and then a punch is used which pushes the metal sheet.
Q. In deep drawing, the drawing force required decreases as strain increases on the metal.
A. True
B. False
.
.Answer: B
Explanation: Process In the deep or cup drawing Process, the drawing force required generally increases linearly with the punch stroke as the strain increases on the metal. This mainly occurs due to strain hardening of material, which makes the forming material less ductile and the strength of the material substantially increases due to strain hardening.
Q. Excessive blank holding force may lead to stretching of sheet metal instead of drawing it.
A. True
B. False
.
.Answer: A
Explanation: Process In deep drawing, if the blank holding force is too high, then the metal around the punch may start to stretch instead of being drawn. This can cause localized necking or diffuse necking, which basically depends on the sensitivity of strain rate, and lubrication, and geometry of punch. If the blank holding force decreases then it may cause free flow of metal into the die cavity.
Q. In deep drawing, the metal at the bottom side of the punch only undergoes longitudinal tensile stresses.
A. True
B. False
.
.Answer: B
Explanation: Process In deep drawing Process, the metal at the bottom of the punch is basically subjected to circumferential tensile stresses and longitudinal tensile stresses also. The punching force applied on the bottom of the cup is transferred to the side of the metal cup. And a narrow ring is present just above the bottom of the metal cup, which undergoes plane strain condition.
Q. The difference between the radius of punch and die basically represents occupied length of metal in the die cavity.
A. True
B. False
.
.Answer: A
Explanation: Process In the deep drawing Process, the metal sheet which occupies the length in the die cavity is mainly represented by the difference between the radius of punch and die, which experiences wrinkling and folding due to inducing of hoop compressive stresses in the sheet material. This may be due to the fact that the diameter of the blank becomes small.
Q. In metal forming, cold rolling Process is completely different from the work hardening Process.
A. True
B. False
.
.Answer: B
Explanation: Process In metal forming, cold working or rolling Process is also known as work hardening Process, which basically defined as the Process of strengthening a material by plastic or permanent deformation. Plastic deformation occurs when a material is altered after its elastic region, this Process makes the material hard and strong.
Q. Cold rolling Process only affects the tensile strength of the material which being rolled.
A. True
B. False
.
.Answer: B
Explanation: Process Cold rolling Process is a very important Process because it allows altering of desired mechanical properties of the material. Cold rolling not only affects the tensile strength, but it also affects the hardness, yield strength, tensile strength and ductility of the material. This Process is very economical as the heating cost is excluded from the Process.
Q. The dislocation density of the material increases during the Process of cold rolling or work hardening.
A. True
B. False
.
.Answer: A
Explanation: Process In cold rolling or work hardening Process, dislocations contact with each other and accept configurations which prevent the movement of other dislocations in the material. During the Process, the dislocation density increases, this also makes increase in the flow stress of the material. Flow stress is defined as the instantaneous value of stress required to continue the plastic or permanent deformation.
Q. The dislocations in the material only act as strong obstacles to the movement of other dislocations.
A. True
B. False
.
.Answer: B
Explanation: Process In general, the dislocations in the material can be acts as either strong or weak obstacles to the movement of other dislocations of the material, which basically depends on the type of interaction that occurs between the movements of dislocations. This Process is mainly considered for strengthening the material which being rolled during the Process.
Q. The dislocation density of the material is defined as the ratio of total dislocation length per unit volume of the material.
A. True
B. False
.
.Answer: A
Explanation: Process In general, the dislocation density of a material is defined as the ratio of total dislocation length per unit volume of the material. It is also defined as the number of dislocations that intersect a unit area of a random part of the material. The dislocation density mainly determines the strength of the material.
Q. Cold rolling is a Process of permanent deformation of material below its re-crystallization temperature.
A. True
B. False
.
.Answer: A
Explanation: Process Cold rolling or working is a Process of permanent or plastic deformation of materials below the re-crystallization temperature, and this Process is generally performed at the room temperature. This Process is widely used for producing products of better surface finish with superior dimensional control.
Q. In cold rolling Process, no any residual stresses are induced in the material during the operation.
A. True
B. False
.
.Answer: B
Explanation: Process In cold rolling Process, strain hardening occurs during the expansion or compression of metal plate, which increases the value of flow stress, so that the required rolling force increases, which further lead to inducing of residual stresses in the material. This residual stresses then can be removed from the material by the annealing Process.
Q. Which of the following methods of heat treatment is best suitable for treating the output of cold rolling?
A. Quenching
B. Case hardening
C. Annealing
D. Cyanide hardening
.
.Answer: C
Explanation: Process The plastic deformation of metal plate in cold rolling includes changing of grain shape, increase in dislocation density and strain hardening of the material. These changes make the metal plate hard and ductile less. So, annealing is a Process of heat treatment in which material regains its softness and relieves all its residual stresses.
Q. The cold rolling Process requires very heavy forces for the accomplishment of rolling operation.
A. True
B. False
.
.Answer: A
Explanation: Process In the cold rolling Process, the metal plate is compressed between the gaps of two large heavy rollers. This Process does not require much of heating the metal plate, so it becomes very difficult to alter the shape of material as the temperature of a material is less than its re-crystallization temperature, and strain hardening also occurs which further makes the metal hard. Hence, this Process requires very heavier forces for the accomplishment of rolling operation.
Q. Over work hardening of material can induce high brittleness in the material.
A. True
B. False
.
.Answer: A
Explanation: Process When the material is Processed by cold rolling then it loses its ductility by increasing its strength. The Process includes strain hardening of the material which induces stresses in the material and when the Process is continued and crosses the limit, then the material becomes very hard and brittle, which can only be overcome by annealing Process.
Q. In fatigue failure, the behaviour of material under cyclic load generally differs from that under monotonic load.
A. True
B. False
.
.Answer: A
Explanation: Process The study of behaviour of material in its fatigue failure is very important to understand for the design and manufacturing purpose. The behaviour of material under cyclic load generally differs from that under monotonic load. Fatigue in the form of initiation of a defect is followed by its growth till the operating load is reached to rupture condition.
Q. In cyclic loading of material, the crack is generally initiated by a sudden or abrupt failure of the material.
A. True
B. False
.
.Answer: B
Explanation: Process In a work-piece subjected to cyclic loading, a fatigue crack is generally initiated on a microscopically small scale which further followed by the growth of crack to a macroscopic size. And in last cycle, the material or specimen fails due to fatigue and fracture occurs which defines complete failure of the work-piece.
Q. The quality of the metal surface is a very important consideration, which greatly affects the fatigue life of the material.
A. True
B. False
.
.Answer: A
Explanation: Process The fatigue phenomenon is generally considered as a mechanism which occurs in metallic materials. The study of the fatigue phenomenon is very necessary for considering several technical conditions which affects the fatigue life and fatigue crack growth in the material, such as the material surface quality, residual stress etc.
Q. Decarburization is a Process which can increase the fatigue limit of the material in case of cyclic loading.
A. True
B. False
.
.Answer: B
Explanation: Process In case of cyclic loading, decarburization is a Process which is defined as the depletion of carbon from the surface of steel alloy. It can significantly reduce the fatigue limit of the steel material. For testing the materials, a batch of similar specimens is selected and then the fatigue strength is determined by considering free surface of the material.
Q. Fabrication methods of materials greatly affect the geometry of defects in the material.
A. True
B. False
.
.Answer: A
Explanation: Process The geometry of defects in the material is greatly influenced by the fabrication methods and also by the quality control procedures which involved the manufacturing of products. Fatigue is a general type of failure, and thus the defect geometry has a significant effect on the fatigue life of the material.
Q. The fatigue limit or strength of the material can change with respect to time.
A. True
B. False
.
.Answer: B
Explanation: Process In many experiments, it has been concluded that the fatigue limit or strength of the material after a long period of time of a metallic material which does not heat up and which surface is not reacted with any other substance chemically during a test remains constant for almost all the practical conditions or purposes.
Q. Environmental conditions can affect the fatigue life of material more severely than the sharp stress concentration conditions.
A. True
B. False
.
.Answer: A
Explanation: Process Environmental conditions can greatly affect the fatigue condition of materials which may be more severe than the sharp stress concentrations conditions. In general, corrosion and temperature are the two main environmental factors which greatly influence the fatigue behaviour of material structures.
Q. Corrosion fatigue is very small problem and it has negligible effects on the material properties.
A. True
B. False
.
.Answer: B
Explanation: Process Fatigue under corrosion is called as corrosion fatigue which is a very complex problem. It mainly refers to the combination of corrosive environment and repeated stress, which can be more detrimental than the other conditions. Repeated stress accelerates the corrosion in material which further accelerates the fatigue conditions in the material.
Q. At low temperature condition of the material, its fracture toughness decreases substantially.
A. True
B. False
.
.Answer: A
Explanation: Process The fracture toughness of the material substantially decreases at low temperature. But at high or elevated temperature, the mean or average stress conditions are extremely complex because of the interactions between fatigue and environmental conditions. At high temperature, the material is plastically deformed with less force.
Q. Neutralization of preexisting defects in the material can lower the chances of fatigue failure.
A. True
B. False
.
.Answer: A
Explanation: Process The fatigue life of material can be improved by various treatments which generally includes grinding, shot peening, spot heating, hammer peening, heat treatment etc. And also by considering strateg
