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7.1 Distinguish between the Brinnell and Rockwell hardness testers that are used to determine the hardness of a metal - NSC Mechanical Technology Fitting and Machining - Question 7 - 2020 - Paper 1
Question 7
7.1 Distinguish between the Brinnell and Rockwell hardness testers that are used to determine the hardness of a metal. Use neat, labelled drawings to indicate the di... show full transcript
Worked Solution & Example Answer:7.1 Distinguish between the Brinnell and Rockwell hardness testers that are used to determine the hardness of a metal - NSC Mechanical Technology Fitting and Machining - Question 7 - 2020 - Paper 1
Step 1
7.1 Distinguish between the Brinnell and Rockwell hardness testers that are used to determine the hardness of a metal. Use neat, labelled drawings to indicate the differences.
Answer
The Brinnell hardness tester uses a steel ball under a specific load to create an indentation on the surface of the metal sample, indicating hardness through the diameter of the indentation. The larger the indentation, the softer the material.
The Rockwell hardness tester, on the other hand, employs a diamond cone or a hard steel ball to penetrate the surface of the material. The depth of the penetration is measured, and this directly correlates to the hardness of the material. Typically, the Rockwell method provides a quicker result than the Brinnell method and is favored for its simplicity and speed.
Step 2
7.2 Describe the function of a tensile tester.
Answer
A tensile tester is designed to evaluate the tensile properties of materials by applying a uniaxial tensile load until failure. It measures key parameters such as tensile strength, yield strength, and elongation, thus providing essential data on how materials behave under tension.
Step 3
7.3 A vernier caliper is used to do precision measuring of an outside diameter, an inside diameter and the depth of a hole. Name THREE other precision measuring instruments that can be used for precision measuring these dimensions.
Answer
- Outside micrometer - Used for measuring external dimensions with a high degree of accuracy.
- Inside micrometer - Specifically designed to measure the internal dimensions of holes and spaces.
- Depth micrometer - Used for measuring the depth of holes, slots, or recesses.
Step 4
7.4 State THREE properties of a metal which can be determined by using a tensile tester to conduct a tensile test on a metal.
Answer
- Tensile strength - The maximum stress a material can withstand while being stretched or pulled before breaking.
- Elasticity - The ability of a material to return to its original shape after the removal of a load.
- Ductility - The extent to which a material can be deformed without fracture, often measured in terms of percentage elongation.
Step 5