Scope:

ASTM E110 method defines the requirements for portable instruments that measure a metal’s Rockwell or Brinell hardness by indentation tests outside of a lab when specimens cannot be tested by a standard E10 or E18 hardness tester due to their size or weight. Hardness testing at a part of the specimen does not represent the physical characteristics of the entire specimen. 

Test Procedure:

ASTM E10 and E18 are the standard tests for measuring Brinell and Rockwell hardness, respectively, but sometimes, because the specimen is too big and heavy, it cannot be tested with their fixed instruments. ASTM E110, instead, uses a portable hardness tester. But the principles used behind this test are the same as E10 and E18. 

ASTM E18 Rockwell Hardness Test Principle:

First, an indenter applies a minor load on the metal, causing a dent. The depth of the dent establishes the baseline depth. Without removing the minor load, a major load is applied for a specific time, and the depth of the indentation produced by it is measured. The harder the metal, the shallower the penetration, and vice versa. The Rockwell hardness value is derived from the difference in the two depths: the baseline depth and final depth. This distance is converted to a hardness number. 

ASTM E10 Brinell Hardness Test Principle: 

Brinell hardness is determined by forcing a hardened steel or carbide ball of known diameter under a known load into a surface and measuring the diameter of the indentation with a microscope. The diameter is used to derive the Brinell hardness value. The portable hardness tester should be verified before the ASTM E110 hardness test with the appropriate standard, E10 or E18. This is done to ensure that environmental conditions (temperature), damage during travel, and usage have not affected the ability of the test equipment to perform properly.  

Video 01: Portable hardness tester

Specimen size:

There is no standard shape or size for a Brinell test specimen, but the test specimen should conform to the following: The specimen should be thick enough that no bulge appears on the part of the specimen opposite the indentation when the load is applied. The thickness of the specimen should be at least ten times the depth of the indentation. The minimum width should conform to the requirements for indentation spacing.

Data:

The following data is calculated in ASTM E110:

1. Rockwell Hardness:   

HR = N – hd 

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. 

2. Brinell hardness number: 

BHN = Brinell hardness number

P = applied load 

D = diameter of the indenter ball in mm, and 

d = measured mean diameter of the indentation in mm

Conclusion:

ASTM E110 method defines the requirements for portable instruments that measure a metal’s Rockwell or Brinell hardness by indentation tests outside of a lab when specimens cannot be tested by a standard E10 or E18 hardness tester due to their size or weight.