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ISO 18265: "Metallic materials — Conversion of hardness values" (2013) ASTM E140-12B(2019)e1: "Standard Hardness Conversion Tables for Metals Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Superficial Hardness, Knoop Hardness, Scleroscope Hardness, and Leeb Hardness" (2019)
Meyer's law is often used to relate hardness values based on the fact that if the weight is quartered, the diameter of the indenter is halved. For instance, the hardness values are the same for a test load of 3000 kgf with a 10 mm indenter and for a test load of 750 kgf with a 5 mm diameter indenter.
The CBR test is a penetration test in which a standard piston, with a diameter of 50 mm (1.969 in), is used to penetrate the soil at a standard rate of 1.25 mm/minute. Although the force increases with the depth of penetration, in most cases, it does not increase as quickly as it does for the standard crushed rock, so the ratio decreases.
Based on Meyer's law hardness values from this test can be converted into Brinell hardness values, and vice versa. [3] The Meyer hardness test was devised by Eugene Meyer of the Materials Testing Laboratory at the Imperial School of Technology, Charlottenburg, Germany, circa 1908. [4] [5]
Standard penetration test blow counts do not represent a simple physical property of the soil, and thus must be correlated to soil properties of interest, such as strength or density. There exist multiple correlations, none of which are of very high quality. [3]
In the above equation, F could be in N and d in mm, giving HV in the SI unit of MPa. To calculate Vickers hardness number (VHN) using SI units one needs to convert the force applied from newtons to kilogram-force by dividing by 9.806 65 (standard gravity). This leads to the following equation: [4]
After time, the indenter on a Rockwell scale can become inaccurate as well and need replacing to ensure accurate and precise hardness measurements. [14] The equation for Rockwell Hardness is =, where d is the depth in mm (from the zero load point), and N and h are scale factors that depend on the scale of the test being used (see following ...
Thereby soil bulk density is always less than soil particle density and is a good indicator of soil compaction. [47] The soil bulk density of cultivated loam is about 1.1 to 1.4 g/cm 3 (for comparison water is 1.0 g/cm 3). [48] Contrary to particle density, soil bulk density is highly variable for a given soil, with a strong causal relationship ...