Knoop hardness test is used to measure the hardness of brittle or fragile materials. It is a micro-indentation test that uses a diamond indenter to create an impression in the material being tested. The Knoop test is similar to the Vickers test, but the Knoop indenter has a longer, more pointed shape that allows for more precise testing of small or thin samples.

Headings:
- What is Knoop hardness test?
- How does Knoop hardness test work?
- What materials can be tested using Knoop hardness test?

What is Knoop hardness test?
Knoop hardness test is a type of micro-indentation test used to measure the hardness of brittle or fragile materials. It was developed by Frederick Knoop in the 1930s and is widely used in materials science and engineering.

How does Knoop hardness test work?
Knoop hardness test works by pressing a diamond indenter into the surface of the material being tested. The indenter creates a small, elongated impression in the material, which is then measured under a microscope. The length of the impression is used to calculate the hardness of the material, which is expressed in Knoop hardness number (KHN).

What materials can be tested using Knoop hardness test?
Knoop hardness test is particularly useful for testing brittle or fragile materials, such as ceramics, glasses, and thin films. It is also used to test the hardness of harder materials, such as metals and alloys, at low loads. Knoop hardness test is less commonly used for testing soft materials, such as rubber, as the indentation can be difficult to measure accurately.