(a) (i) Distinguish between metal fatigue and metal creep - Leaving Cert Engineering - Question 2 - 2011

1. Name of Tests:

   • Hardness Test A: Brinnell hardness test or Rockwell Ball test.

   • Hardness Test B: Vickers hardness test or Knoop hardness test.

   2. Method of Measurement:

   • Hardness Test A uses a Brinnell indenter that measures the diameter of the indentation caused by a specific load.

   • Hardness Test B employs different indenters with varying loads for measuring the depth or size of the indentation.

   3. Test Material Suitability:
   • Hardness Test A is typically suited for softer materials, while Hardness Test B is applicable to harder materials due to its ability to make finer indentations.

To find Young's modulus of elasticity, use the formula:
$E = \frac{\text{Stress}}{\text{Strain}}$
From the data provided, selecting the linear portion of the graph lets us calculate:
$E = \frac{110 \text{ N/mm}^2}{1.25 \cdot 10^{-3}} = 88.8 \text{ kN/mm}^2$

The 0.1% proof stress can be determined from the plotted graph. At a strain of 1.0 (<1000) in the graph, the corresponding stress is found to be 325 N/mm².

1. Manufacturing Cost: Non-destructive tests can be costly, as processes such as casting require careful inspections to ensure component quality, thus minimizing waste.

2. Material Integrity: NDTs are essential to ensure that each acceptable component meets quality standards without causing damage in the testing process.

Ultrasonic testing involves a quartz crystal that generates high-frequency vibrations that are directed into the material being tested. The ultrasonic waves reflect back to a receiver that displays any defects or flaws.

A diagram illustrating a Pulse/Receiver setup with waves being transmitted into a test material would typically show the detection of flaws based on wave reflection.