Modle 2 : Hardness tests Flashcards
Name four types of hardness tests?
Brinell, Vickers, Rockwell and Shore scleroscope
What is the Brinell hardness test?
A hardened steel ball is forced into an object under specified load conditions.
The hardness number is determined by measuring the depth and surface area of the impression and by using a formula, which also incorporates the load.
What is the Vickers hardness test?
A small pyramid is forced into a test piece under specified load conditions.
The hardness number is derived from a formula that contains the load and area of the indentation.
More useful for thin metals as the loads are lower and the indentor is smaller.
What is the Rockwell hardness test?
A diamond cone (or sphere) is forced into a test piece under specified load conditions and a reading is displayed on the dial.
There are different scales for different loads depending on the material used.
There is no formula as it is a number from 100-500.
What is the Shore Scleroscope hardness test?
This test involves a small striker in a tube.
The tube is placed over an item and the striker is dropped, the height the striker rebounds from the item is the measure of the hardness.
What is the definition of hardness
The resistance of a material to localised plastic deformation.
What is the definition of toughness
The measurement of a materials resistance of fracture when subjected under stress
Define the Izod impact test
A pendulum is swung from a height and fractures the material and the energy absorbed is measured
What is the importance of hardness testing in the car market
Parts of cars are designed specifically to crush under force to reduce the impact impact force of high speed crashing, these are called “crumple zones”
How will a low toughness metal break or fracture
A low toughness metal will generally fracture in a brittle manner in which the crack is able to propagate without the absorption of additional energy
