Question

Match the defects in Column I with corresponding metal forming techniques in Column II.
Column I
(P) Cold shut
(Q) Zipper breaks
(R) Stretcher strains
(S) Center burst
Column II
(1) Rolling
(2) Sheet metal forming
(3) Drawing
(4) Forging

• A. P – 4, Q – 1, R – 2, S – 3
• B. P – 4, Q – 2, R – 3, S – 1
• C. P – 1, Q – 4, R – 2, S – 3
• D. P – 3, Q – 1, R – 4, S – 2

Hint:

In matching questions, identify the most definite and well-known pairs first (e.g., Cold shut with Forging). Use these certain matches to eliminate incorrect options, which can often lead you to the correct answer even if one pairing seems unusual.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Different metal forming processes create unique stress and material flow conditions, which can lead to specific types of defects. The task is to match each defect with the process in which it most commonly occurs.
Step 2: Detailed Analysis of Each Defect:
- (P) Cold shut: This is a surface defect that occurs in forging. It forms when two streams of molten or semi-molten metal flow together but fail to fuse completely, creating a crack-like discontinuity. This happens when metal flows around a die contour and meets on the other side at too low a temperature. Thus, P matches with 4.
- (R) Stretcher strains: Also known as Lüders bands or Piobert lines, these are localized bands of plastic deformation that appear on the surface of some metals (like low-carbon steel) during sheet metal forming operations like stretching or drawing. They create an unsightly elongated pattern. Thus, R matches with 2.
- (S) Center burst: This is an internal defect, also known as chevron cracking. It is caused by high hydrostatic tensile stresses at the centerline of the workpiece during extrusion, drawing, or sometimes rolling. Among the given choices, it is a well-known defect in drawing. Thus, S matches with 3.
- (Q) Zipper breaks (or Zipper cracks): This defect is most characteristically associated with the deep drawing of cups, where a vertical crack propagates down the cup wall. However, examining the options, if we lock in P-4, R-2, and S-3, we are left with Q-1.
Step 3: Matching based on the Options:
Let's check the given options with our most certain matches: P-4 and R-2.
- Option (A): P-4, Q-1, R-2, S-3. (Contains P-4 and R-2)
- Option (B): P-4, Q-2, R-3, S-1. (Contains P-4 but not R-2)
- Option (C): P-1, Q-4, R-2, S-3. (Contains R-2 but not P-4)
- Option (D): P-3, Q-1, R-4, S-2. (Contains neither)
Only option (A) contains both of the most certain matches (P-4 and R-2). It also correctly matches Center Burst (S) with Drawing (3). The only unusual pairing is Zipper breaks (Q) with Rolling (1). Given that the other three matches in option (A) are strong, this is the intended correct answer.
The final matching is:
- (P) Cold shut \(⇒\) (4) Forging
- (Q) Zipper breaks \(⇒\) (1) Rolling
- (R) Stretcher strains \(⇒\) (2) Sheet metal forming
- (S) Center burst \(⇒\) (3) Drawing
Step 4: Why This is Correct:
Option (A) provides the most accurate set of matches. Cold shut in forging, stretcher strains in sheet metal forming, and center burst in drawing are all classic defect-process pairings.