Question

In which of the following process, the state of stress of the material undergoing deformation is only shear?

• A. Drawing
• B. Spinning
• C. Hobbing
• D. Blanking

Hint:

Think about how material removal or separation occurs in each process. Blanking is like using scissors on a sheet of paper – the cutting action is mainly due to shear.

Answer 1

The Correct Option is D

Step 1: Understand the state of stress in different manufacturing processes.
The state of stress in a material undergoing deformation can be complex, involving combinations of tensile, compressive, and shear stresses. The question asks for a process where the dominant state of stress leading to material separation is shear. Step 2: Analyze the state of stress in the Drawing process.
Drawing involves pulling a material through a die to reduce its cross-section. The material experiences tensile stresses along its length and compressive stresses due to the die. Shear stresses are also present due to friction and material flow, but the primary deformation mechanism involves tensile and compressive stresses. Step 3: Analyze the state of stress in the Spinning process.
Spinning is a metal forming process where a rotating disc or tube of metal is shaped over a mandrel. The material experiences complex states of stress, including tensile, compressive, and shear stresses as it is formed around the mandrel. Step 4: Analyze the state of stress in the Hobbing process.
Hobbing is a gear cutting process that uses a rotating cutter (hob) to generate gear teeth. The material removal occurs through a complex interaction involving cutting forces that induce shear, compressive, and tensile stresses in the workpiece material at the cutting zone. Step 5: Analyze the state of stress in the Blanking process.
Blanking is a sheet metal cutting operation where a punch forces a piece of metal (the blank) out of the sheet. The material separation occurs primarily due to shearing along the periphery of the punch and die. The dominant stress state in the material undergoing separation is shear stress, exceeding the shear strength of the material. Step 6: Compare the dominant stress states in the given processes.
Drawing: Primarily tensile and compressive stresses.
Spinning: Complex combination of tensile, compressive, and shear stresses.
Hobbing: Complex combination of shear, compressive, and tensile stresses leading to material removal by cutting.
Blanking: Primarily shear stress leading to material separation. Step 7: Select the process where the state of stress is only shear (dominant shear leading to separation).
In the blanking process, the material undergoes fracture primarily due to shear stress exceeding the shear strength. While other stresses might be present, the material separation is predominantly due to shear.