Hardness Testing Basics
Hardness, as applied to most materials, and in particular metals, is a valuable, revealing, and commonly employed mechanical test that has been in use in various forms for more than 250 years. As a material property, its value and importance cannot be understated; the information from a hardness test can be used to provide critical material performance information and insight to the durability, strength, flexibility, and capabilities of a variety of component types from raw materials to prepared specimens, and finished goods. Hardness testing is widely used in a multitude of industries and plays particular significance in structural, aerospace, automotive, quality control, failure analysis, and many other forms of manufacturing.
What is indentation hardness testing? The most basic and commonly used definition is the resistance of a material to permanent, plastic deformation. It is measured by loading an indenter of specified geometry and properties onto the material for a specified length of time, and measuring either the depth of penetration or dimensions of the resulting indentation or impression. Rockwell testing is the most commonly used method by virtue of the quick results generated and is typically used on metals and alloys. It generates a value based on indentation depth or un-recovered indentation.
Importance of good practice
Paramount to accurate and reliable Rockwell hardness results is ensuring that the operators and the methods used are following proper test technique and practice. The precise nature and exactness of a Rockwell test require following strict hardness protocol and adherence to standards. With the unit of measurement for one regular Rockwell point equal to only 0.002 mm (approx. 0.00008 inch) it becomes obvious that such exact measurement requires a very precise measuring system and process. Failure to properly prepare and execute a Rockwell hardness test can result in compromised test data or false readings, potentially contributing to the production and delivery of substandard product. This could have detrimental and catastrophic effects on the performance and the integrity of the goods they are used in.
Rockwell Test Techniques - Test Scale
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