Manufacturing And Production Technology MCQ Questions & Answers | Mechanical Engineering

In manufacturing and production technology, tools used for cutting or shaping materials can fail in various ways. Let’s go through the options:

Option A: Cracking at the cutting edge due to thermal stresses → Correct. When a tool is used under high heat conditions, such as during high-speed cutting, thermal stresses can build up. This can lead to cracking at the cutting edge due to the sudden expansion and contraction of the material.

Option B: Chipping of the cutting edge → Correct. The cutting edge can chip due to the impact forces or the abrasive nature of the material being worked on. This is a common form of failure, especially in brittle materials.

Option C: Plastic deformation of the cutting edge → Correct. Under excessive force or high temperature, the material at the cutting edge can undergo plastic deformation, meaning it changes shape permanently. This results in a loss of the tool's sharpness and effectiveness.

Since all of the mentioned causes can lead to tool failure, the correct answer is Option D: All of these. Each of these factors contributes to the degradation of the tool's cutting edge over time.

Under fill is a type of welding defect that occurs when there is poor deposition of weld metal.

Cause: It happens due to insufficient filler material being deposited in the weld joint, often because of improper technique or incorrect welding parameters.

Appearance: The weld surface appears below the level of the adjacent base metal, leaving the joint weaker than required.

Other defects:
Porosity refers to gas pockets or voids trapped in the weld.

Undercut occurs when excessive melting leaves a groove along the weld toe.

Cracks are linear ruptures caused by stresses during solidification or cooling.

Conclusion: The defect due to poor weld metal deposition is called under fill.

The correct answer is Option C: Shear angle.
Let's break down why:

Option A: Cutting speed
While cutting speed is important in machining, it's more of a process parameter than a fundamental material property that *defines* machinability.

Option B: Feed rate
Similar to cutting speed, feed rate is a process setting.

Option C: Shear angle
The shear angle is the angle between the shear plane (where the material is deformed and separated) and the cutting direction.
- A larger shear angle generally means less force is needed to cut the material.
- Less force usually translates to better machinability (easier to cut, smoother surface finish, less tool wear).
- Think of it this way: a bigger shear angle is like slicing something with a very sharp angle; it requires less effort.

Option D: Tool geometry
Tool geometry definitely affects how well a material can be machined, but it's an external factor. The shear angle is more related to the material's response to cutting.
In summary: The shear angle directly reflects how easily a material deforms and separates during cutting, making it a key indicator of its machinability.