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71:. The geometry of this indenter is an extended pyramid with the length to width ratio being 7:1 and respective face angles are 172 degrees for the long edge and 130 degrees for the short edge. The depth of the indentation can be approximated as 1/30 of the long dimension. The Knoop hardness
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The advantages of the test are that only a very small sample of material is required, and that it is valid for a wide range of test forces. The main disadvantages are the difficulty of using a microscope to measure the indentation (with an accuracy of 0.5
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point is pressed into the polished surface of the test material with a known (often 100 g) load, for a specified dwell time, and the resulting indentation is measured using a
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275:{\displaystyle HK={{{\text{load}}(\mathrm {kgf} )} \over {{\text{impression area}}(\mathrm {mm} ^{2})}}={P \over {C_{\text{p}}L^{2}}}}
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used particularly for very brittle materials or thin sheets, where only a small indentation may be made for testing purposes. A
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Variables such as load, temperature, and environment, may affect this procedure, which have been examined in detail.
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HK values are typically in the range from 100 to 1000, when specified in the conventional units of kg
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is the correction factor related to the shape of the indenter, ideally 0.070279
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408:"A Sensitive Pyramidal-Diamond Tool for Indentation Measurements"
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and colleagues at the
National Bureau of Standards (now
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Journal of
Research of the National Bureau of Standards
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292:is the length of indentation along its long axis
88:Comparison between the Mohs and the Knoop scales
56:is a microhardness test – a test for mechanical
406:F. Knoop, C.G. Peters and W.B. Emerson (1939).
395:"Microhardness Test", Surface Engineering Forum
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20:Angles of a Knoop hardness test indenter
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418:(1): 39–61 (Research Paper RP1220).
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81:is then given by the formula:
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370:Leeb Rebound Hardness Test
365:Knoop hardness of ceramics
326:The test was developed by
439:Czemuska, J. T. (1984).
323:⋅mm = 9.80665 MPa.
488:Dental hardness tables
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360:Vickers hardness test
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441:Proc. Br. Ceram. Soc
425:10.6028/jres.023.022
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375:Meyer hardness test
315:⋅mm. The SI unit,
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26:Knoop hardness test
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128:Tooth enamel
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307:is the load
447:: 145–156.
382:References
344:micrometre
69:microscope
62:pyramidal
497:Category
353:See also
98:Material
58:hardness
285:where:
158:Diamond
65:diamond
483:efunda
317:pascal
138:Quartz
107:Dentin
162:7000
152:2480
466:help
336:ASTM
332:NIST
189:load
142:820
132:343
119:foil
117:Gold
24:The
420:doi
122:69
111:68
101:HK
78:KHN
75:or
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73:HK
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321:f
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305:P
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296:C
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265:2
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241:=
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230:2
225:m
222:m
217:(
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203:f
200:g
197:k
193:(
182:=
179:K
176:H
52:/
49:p
43:n
40:ˈ
37:ə
34:k
31:/
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