Brinell Hardness Number Calculator
Find the Brinell hardness number (BHN).
The Brinell test presses a hard ball into a surface and measures the dent.
How the Math Works
The Brinell Hardness Number (BHN) is calculated using the formula BHN = 2F ÷ (πD(D − √(D² − d²))). This equation determines hardness by measuring how a material resists indentation. Here, F represents the applied force in kilograms-force (kgf), D is the diameter of the steel ball indenter in millimeters, and d is the diameter of the resulting indentation hole. The formula works by dividing twice the applied force by the surface area of the indented cone-shaped region, effectively calculating force per unit area to quantify the material's resistance to deformation.
Practical Applications
To apply this calculation practically, engineers and material scientists first conduct a standardized test where a hardened steel ball of known diameter (D) is pressed against the test material under a specific load (F) for 10-15 seconds. After the load is released, the diameter of the indentation (d) is measured using a microscope or optical projector. These three measured values are then plugged into the BHN formula to determine the hardness number. This process is commonly performed on metal samples in quality control labs, manufacturing facilities, and research institutions to verify material properties meet specified standards.
Day-to-Day Use
Understanding Brinell hardness helps ensure the materials used in everyday products are suitable for their intended applications. For example, knowing the BHN of steel components in your car's engine ensures they won't wear down prematurely, while hardness measurements of kitchen knives guarantee they maintain their edge sharpness. Construction workers rely on hardness testing to select appropriate materials for concrete reinforcement, and manufacturers use BHN values to choose the right metals for everything from smartphone casings to airplane parts, ensuring safety and durability in the products we use daily.
Worked example
3000 kgf, 10 mm ball, 4 mm dent → about 229 HB.
FAQ
Brinell vs Vickers?
Both measure hardness; Vickers uses a diamond pyramid and suits harder materials.