Tensile Testing: Exam Questions

Question 1

Identify the basic information that can be obtained from a tensile test.

Answer 1

The following information can be obtained from a tensile test.
Youngs Modulus (A measure of stiffness)
Proof stress or Yield stress (point at which it begins to deform plastically)
Ultimate Tensile Strength (maximum stress a material can withstand)

Question 2

What is the purpose of a tensile test?

Answer 2

It finds our various properties and the ductility of a material.

Question 3

Explain in detail how a tensile test is carried out and the results we get

Answer 3

It involes putting a test specimen as shown into a tensile testing machine.
The test piece is held at both ends and stretched slowly.
As it is stretched the load (force) applied and the extension of the piece is recorded by the tensile testing machine.
These values can be then drawn into a Load / Extension diagram.

From this diagram, we can get the ductility, the ultimate tensile strength, the proof stress and the Youngs modulus of the material. These can be all used in the selection of a material for a specific job.

Question 4

Explain the difference between ductile fracture and brittle fracture.

Answer 4

Ductile Fracture-
A ductile material will stretch a lot and break in a cup and cone format. The fractured surface will have a dull appearance.

Brittle Fracture-
A brittle material will not stretch much and will have a clean break. The fractured surface will have a shiny finish.

Question 5

Factors necessary to prevent early fatigue include…(5)

Answer 5

Make allowance for potential fatigue during component design.
• Removal of sharp corners.
• Reduce vibration.
• Improve surface finish.
• Prevent or minimise corrosion