This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Deep Drawing”.
1. 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
View Answer
Explanation: 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.
2. In the deep drawing process, a clearance is provided between the punch and die to succeed the forming operation.
a) True
b) False
View Answer
Explanation: 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.
3. Deep drawing process can also be possible by having shearing operation instead of bending operation.
a) True
b) False
View Answer
Explanation: 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.
4. In deep or cup drawing, maximum tensile stress is caused near the end of punch.
a) True
b) False
View Answer
Explanation: 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.
5. Necking phenomena do not occur in the process of a cup or deep drawing.
a) True
b) False
View Answer
Explanation: 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.
6. In metal forming, deep drawing process is completely different from wire drawing process.
a) True
b) False
View Answer
Explanation: 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.
7. In deep drawing, the drawing force required decreases as strain increases on the metal.
a) True
b) False
View Answer
Explanation: 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.
8. Excessive blank holding force may lead to stretching of sheet metal instead of drawing it.
a) True
b) False
View Answer
Explanation: 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.
9. In deep drawing, the metal at the bottom side of the punch only undergoes longitudinal tensile stresses.
a) True
b) False
View Answer
Explanation: 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.
10. The difference between the radius of punch and die basically represents occupied length of metal in the die cavity.
a) True
b) False
View Answer
Explanation: 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.
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