Question

Task (1)

You work as a material engineer at an aircraft development, manufacturing and maintenance company in the MENA region. Recently, the manufactured airplanes have been experiencing crashes after a couple of years in service. You have been assigned as a member in the investigation team to identify the main cause of the crashes.

                           

1. The shape of the designed windows of the manufactured planes is square. The investigation team suggested that this design might be the main cause of the crashes. You must provide a possible explanation of the investigation conclusion from an engineering point of view.

2. Write the properties that should be considered when designing and manufacturing the coroners of the windows from an engineering point of view.

3. You have been given a sample of a malfunctioned airplane wing, which is made of aluminium. The company offered you an access to a tensile testing equipment and magnetic particles inspection equipment to investigate the malfunctioning behaviour. The results of your experiment were as follows:

Load (KN)	Extension (mm)
13	0.2
29	0.4
56	0.7
70	0.9
95	1.5
110	2.5
132	5
147	8.5
145	10
130	12

Table 1: Tensile Testing Results (Load Extension)

1. Given that the length of the sample is 90 mm and the diameter of it is 7 mm.
   1. Draw the stress stain diagram.
   2. Find the yield stress (in KN/mm²).
   3. Find the ultimate tensile stress (in KN/mm²).
   4. At a point on the proportional section, calculate the modulus of Elasticity (Young’s modulus).

Hint: when calculating the Elasticity, use the stress strain numbers, not the force numbers

Answer 1