Testing of Materials

Question 1

X-ray

Answer 1

Non-destructive; used to determine if cavities are present. Operates on the same principles as medical x-rays - if there is a cavity, the x-rays will pass through that area more easily and hence more x-rays will reach the film.

Question 2

Dye Penetrant

Answer 2

Non-destructive; aids in finding small surface cracks. Works by placing a dye on the surface, applying a developer and then examining after cleaning (UV may be used).

Question 3

Ultrasonic

Answer 3

Non-destructive; ultrasonic pulses are used to determine if cavities are present. Functions in a similar way to x-ray, but high frequency radio waves are used instead. A transmitter sends ultrasonic waves through an object which are reflected back to the sender; the signals are then recorded by a display. Height of the wave on the display is proportional to thickness, so if a cavity is detected, the wave will reflect early and the height will be lower.

Question 4

Tensile

Answer 4

Destructive; used to determine the tensile strength of the material. The piece is stretched and load and extension are recorded.

Question 5

Compressive

Answer 5

Destructive; used to determine the compressive strength of the material. The piece is compressed and load and deformation are recorded.

Question 6

Transverse

Answer 6

Destructive; used to determine a material’s performance when undergoing bending and shear. The material is supported at either end and is loaded in the centre or at intervals along the beam in the OPPOSITE DIRECTION.

Question 7

Torsion

Answer 7

Destructive; used on a material to see how they will cope with twisting forces (couples).