Ceramics are inorganic non-metallic materials. Metal oxides are common examples of ceramics, but also other elements such as carbides and nitrides have been further embedded. Porcelain, glass, brick and refractory resources are various examples of traditional ceramics. In the past 30 years, advances in materials science have transformed once fragile ceramic material tough enough to withstand the engine environment.
Hardness is the resistance of the material to bend the plastic indentation. Occasionally hardness refers to the material's resistance to scratching and abrasion. In many cases relatively quickly and the minimum hardness test could replace the tensile test. Resistance can be measured with a small sample of the material without breaking.
Hardness is one of the most commonly measured properties of ceramics. Its value helps to characterize resistance to deformation, densification and fracture.
The resistance is important for cutting tools, wear and abrasion resistant parts, prosthetic hip joint ball and socket, optical lens glasses, ballistic armor, molds and dies, valves and seals. In fact, many ceramic hardness specifications list the minimum requirements.
hardness of ceramic tools is a property that distinguishes the size as it relates to the ability of materials to withstand the penetration of the surface through a combination of brittle fracture and plastic flow.
Often, hardness directly equated with resistance to wear. It is a mistaken notion to many metallic components and is absolutely the wrong choice criteria with regard to engineering ceramic materials.
global standards for regular ceramic resistance have different requirements to control the loading rate during indentation ciklusa.Literatura analysis suggests that loading rate may affect the measure of hardness in a few cases. Given the uncertainty of this problem, additional experiments in the range of indentation loading rates were achieved on steel, sintered silicon carbide, and aluminum oxynitride.
modern standard methods for measuring the resistance to static load application rate limits, but there is great variability in the rate limits are zahtjevima.Zahtjevi indenter movement during the loading cycle, or ambiguous statements in order to prevent the impact.
Ceramics are typically more brittle than metals and can have a similar stiffness (modulus) and similar force, especially in compression. However, the tensile test, they are likely to fail at a much lower applied stress. This is because the surface of the ceramic is almost always contain minute cracks ("Griffith cracks"), which increase the applied stress.
The oldest method of hardness testing is difficult to use the file on the test piece and see how difficult it is to remove the material. The following method is called the Rockwell hardness test. This is the most widely used test to the stamp business. Resistance can be read on two separate ljestvice.Najviše accepted the "C" scale that uses a diamond konus.Manje accepted "B" scale used by the ball is analogous to that used in the Brinell test. Brinell hardness is determined by forcing a hard steel or carbide sphere of a diameter below a certain load in the material surface and measuring the diameter indentation left after testa.Broj Brinell hardness, or simply the Brinell number obtained by dividing the output terminals, in kilograms, so the actual size indentation in square millimeters . the result is a measurement of pressure, but the units are seldom validated.
Vickers hardness test This is a standard method for measuring the resistance of metals and ceramics, especially those with extremely durable surface: the surface is subjected to a standard pressure for the standard length of time using a pyramid-shaped indentation dijamant.Dijagonalu result measured under a microscope, a Vickers Hardness value read from a conversion table.
relative microhardness of the material is determined by the Knoop indentation test. In this test, the pyramid shaped diamond indenter with apical angles of 130 and 172 30is pressed against the material. Making thombohedral impression with a diagonal seven times longer than ostalih.Tvrdoća material is determined by the depth to which penetrates Knoop indenter.
coast scleroscope measure resistance in terms of elasticity materijala.Dijamant-tipped hammer in a graduated glass tube should not fall from the known height of the sample for testing, and hardness of the amount depends on the amount by which the hammer rebounds, heavier items, jump higher. The results obtained from this test are a useful measure of relative resistance to indentation of various grades of polymers. However, Shore Hardness Durometer test does not serve as a predictor of other properties such as strength or resistance to scratches, abrasion or wear, and may not be used for product design specifications.
