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Scratch hardness test or scratch test refers to any of a number of methods of measuring scratch hardness. Resistance to abrasion is less affected by surface variations than indentation methods. Scratch hardness is measured with a sclerometer. [1] Attempting to scratch a surface to test a material is a very old technique. [2]
The principle is that an object made of a harder material will scratch an object made of a softer material. When testing coatings, scratch hardness refers to the force necessary to cut through the film to the substrate. The most common test is Mohs scale, which is used in mineralogy. One tool to make this measurement is the sclerometer.
Abrasion, under its strictest definition, is commonly confused with attrition and sometimes hydraulic action however, the latter less commonly so. Both abrasion and attrition refers to the wearing down of an object. Abrasion occurs as a result of two surfaces rubbing against each other, resulting in the wearing down of one or both of the surfaces.
One type of instrument used to get the abrasion rate and normalized abrasion rate is the abrasion scrub tester, which is made up of a mechanical arm, liquid pump, and programmable electronics. The machine draws the mechanical arm with attached brush (or sandpaper, sponge, etc.) over the surface of the material that is being tested.
Abrasion (mechanical) – Process of wearing down a surface; Backlash (engineering) – Clearance between mating components; Hysteresis – Dependence of the state of a system on its history; Tribometer – Instrument that measures friction and wear between surfaces — Equipment used to measure friction and wear
Abrasions on elbow and lower arm. The elbow wound will produce a permanent scar. A first-degree abrasion involves only epidermal injury. A second-degree abrasion involves the epidermis as well as the dermis and may bleed slightly. A third-degree abrasion involves damage to the subcutaneous layer and the skin and is often called an avulsion.
An abrasive which is too hard or too coarse can remove too much material or leave undesired scratch marks. Besides being unsightly, scratching can have other, more serious effects. Excessive abrasion or the presence of scratches may: diminish or destroy usefulness (as in the case of scratching optical lenses and compact discs or dulling knives);
Mohs hardness kit, containing one specimen of each mineral on the ten-point hardness scale. The Mohs scale (/ m oʊ z / MOHZ) of mineral hardness is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of minerals through the ability of harder material to scratch softer material.