Hardness measurement is a key test used to assess the suitability of metallic materials for suitability in various applications.This method uses a portable Leeb tester which measures the hardness of a test piece. The reading given by the Leeb tester is a ‘hardness number’ corresponding to a specific surface or material hardness. This article will explain how you can read and represent the Leeb hardness value in your report.
I. Why Use the Leeb Hardness Scale?
The Leeb hardness scale was developed in 1975 to provide an alternative for portable testing of metallic materials. This scale provides an alternative to the traditional hardness testing methods, which use complex equipment. Other traditional methods such as the Brinell, Rockwell, and Vickers use complex machines fixed in laboratory workstations. The Leeb hardness test uses a portable and automatic device that is non-destructive. This makes hardness testing easier and reduces the cost of inspecting materials.
II. How is the Leeb Hardness Calculated?
The Leeb hardness is computed by using the formula: HL = (Vr/Vi) x 1000
HL = Leeb hardness in Kilograms per square millimeter
Vr = Rebound velocity
Vi = Impact velocity
The Leeb hardness test is measured in three phases. An impact body is accelerated towards the test piece in the first phase using a spring load. In the second phase, the impact body directly contacts the test piece. The force of the impact body elastically deforms the test piece, and the test piece completely stops the impact body. This is known as the impact phase. In the final test phase, the rebound phase, the spring load on the impact body uses the impact force to rebound from the test piece. The difference in the velocities of the impact phase and the rebound phase is then used to calculate the Leeb hardness of the test piece.
The Leeb hardness test is the most widely used method of measuring the resistance of materials to indentation.
III. How do you Read Leeb Hardness Value?
The Leeb hardness value has three major parts. These are a numeric value representing hardness, two letters abbreviation “HL” representing the Leeb hardness, and a scale designation that defines the load applied and other test parameters.
IV. Example of How to Represent and Read Leeb Hardness Value
Below is an example of a Leeb hardness value and the breakdown of each part.
780 HL D
780 is the numeric value representing the hardness
HL is an abbreviation representing Leeb hardness
D represents a tungsten carbide ball indenter with a 1.5mm radius and a load of 5.45g.
Related Article: How to Read and Represent Rockwell Hardness Value?
Related Article: How to Read and Represent Vickers Hardness Value?
With the Leeb hardness value, you can easily quantify the surface hardness level and make notes on its suitability for a specific purpose. The Leeb value can also be used to compare the hardness of different materials. This method was developed to provide simplicity and portability of hardness testing with the portable Leeb hardness testers.