In recent years, numerous methods have been developed to detect surface defects on various materials. Hardness testing is a fundamental test method used to measure the hardness of materials, usually metals. Many different tests can be used to determine the hardness of a material, depending on what properties you’re looking to measure. The Leeb Hardness Testing Method uses a conical indenter and ball indenter to measure the hardness of a material. This article explains how this method works and its applications.
I. What is the Principle of the Leeb Method?
The Leeb method principle uses a spherical tungsten carbide ball and a spring load to measure the hardness of a test piece. This method uses a rebound technique which measures the energy lost when the impact body hits the test sample. This method uses a spring load applied to the test piece at a specified velocity using the spring’s kinetic energy. The impact of the load on the test piece creates an indentation, and the spring load loses some kinetic energy during the rebound. It loses even more kinetic energy when impacting a softer test piece because it creates a larger indentation. The difference in the velocities of the spring load is used to measure the hardness value.
II. What are the Applications of the Leeb Method?
The Leeb method is commonly used to measure the hardness of large and heavy pieces of metals such as rollers and engine blocks.
The Leeb method is also used to measure small and light parts coupled to heavy metals such as screws and bolts.
This method can make measurements in all directions: vertical, horizontal, and at an angle.
This method is suitable for inspecting stationary structures such as bridge halls and the pipes used for oil and gas transport.
Related Article: What are the Advantages and Disadvantages of the Leeb Method?
Related Article: How to Perform a Leeb Hardness Test?
III. What Distinguishes the Leeb Method?
The Leeb method is distinguished from the other methods by:
- Impact unit indenter material and shape
- Velocities of the impact
Test method | Kinetic impact energy [mJ] | Impact velocity [m/s] | Rebound velocity [m/s] | Maximum distance between indenter ball and test surface [mm] | Mass of impact body [g] | Spherical radius [mm] | Material of indenter | Application range |
HLD | 11.5 | 2.05 | 0.615 – 1.8245 | 2 | 5.45 | 1.5 | WC-Co | 300 – 890 HLD |
HLS | 11.4 | 2.05 | 0.82 – 1.886 | 2 | 5.4 | 1.5 | C | 400 – 920 HLS |
HLE | 11.5 | 2.05 | 0.615 – 1.886 | 2 | 5.45 | 1.5 | PCD | 300 – 920 HLE |
HLDL | 11.95 | 1.82 | 1.1092 – 1.729 | 2 | 7.25 | 1.39 | WC-Co | 560 – 950 HLDL |
HLD+15 | 11.2 | 1.7 | 0.561 – 1.513 | 2 | 7.75 | 1.5 | WC-Co | 330 – 890 HLD+15 |
HLC | 3 | 1.4 | 0.49 – 1.344 | 2 | 3.1 | 1.5 | WC-Co | 350 – 960 HLC |
HLG | 90 | 3 | 0.9 – 2.25 | 3 | 20 | 2.5 | WC-Co | 300 – 750 HLG |
Conclusion
The Leeb method is a useful and accurate hardness testing method. The form of the impact unit is more subtle and detailed compared to other hardness testing methods, which makes it easier to determine why a test piece did not meet the desired result. The method is commonly used to measure the hardness of steel, iron, aluminum, and copper. These materials are not only used in manufacturing because they are important to transportation, oil and gas, and bridge building industries.