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(a) The diagram illustrates a hardness testing machine - Leaving Cert Engineering - Question 2 - 2009
Question 2
(a) The diagram illustrates a hardness testing machine. (i) Identify the hardness test shown. (ii) Describe the main features of this mechanical test. (b) T... show full transcript
Worked Solution & Example Answer:(a) The diagram illustrates a hardness testing machine - Leaving Cert Engineering - Question 2 - 2009
Step 1
Step 2
Describe the main features of this mechanical test.
Answer
The Vickers hardness test employs a diamond indenter that is pressed into the surface of the test material under a measured load. The depth of the indentation produced correlates to the hardness, making the test suitable for a variety of materials. The indenter's angle is 136°, facilitating precise measurements suitable for hard materials.
Step 3
Step 4
Describe, with the aid of diagrams, the shape of the test specimen at point B and the shape of the test specimen at point C.
Answer
At point B, the specimen will have thinned uniformly as strain increases up to this point, exhibiting a clear necking behavior during elongation.
At point C, the specimen will show a distinctive 'cup and cone' fracture. One side features a rough cone shape, while the opposite side displays a hollow cup shape.
Step 5
Outline two reasons why non-destructive tests are used in the manufacture of cast motorcycle engines.
Answer
- Casting engines are often expensive; non-destructive testing (NDT) allows for thorough evaluation without damaging the components.
- NDT methods are deployable on each engine to ensure all acceptable parts are thoroughly checked.
Step 6
Describe, with the aid of a suitable diagram, a non-destructive test for locating surface flaws on aluminium castings.
Answer
One common non-destructive testing method is the use of penetrant tests, which involve applying a dye to the surface. After a brief period, excess dye is removed, and a developer is added to enhance visibility of any surface cracks or flaws. The flaws can be identified by the contrasting colors displayed in the imperfections.