1、Designation: A1038 10aStandard Test Method forPortable Hardness Testing by the Ultrasonic ContactImpedance Method1This standard is issued under the fixed designation A1038; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of compara-tive hardness values by applying the Ultrasonic ContactImpedan
3、ce Method (UCI Method).1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this sta
4、ndard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A370 Test Methods and Definitions for Mechanical Testingof Steel ProductsE10 Test Method for Brinell Hardness of Metallic Mat
5、erialsE18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE140 Hardness Conversion Tables for Metals RelationshipAmong Brinell Hardness, Vickers Hardness, RockwellHardness, Superficial Hardness, Knoop Hardness, andScleroscope HardnessE177 Practice for Use of the Terms Precision and Bias inA
6、STM Test MethodsE384 Test Method for Knoop and Vickers Hardness ofMaterialsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 UCI methodUltrasonic Contact Impedance, a hard-ness testing method developed by Dr. Claus Kle
7、esattel in 1961based on the measurement of the frequency shift of a resonat-ing rod caused by the essentially elastic nature of the finite areaof contact between the indenter and the test piece during thepenetration.3.1.2 UCI hardness testa hardness testing method using acalibrated instrument by pre
8、ssing a resonating rod with adefined indenter, for example, a Vickers diamond, with a fixedforce against the surface of the part to be tested.3.1.3 calibrationdetermination of the specific values ofthe significant operating parameters of the UCI instrument bycomparison with values indicated by a sta
9、ndardized workbenchhardness tester or by a set of certified reference test pieces.3.1.4 verificationchecking or testing the UCI instrumentto ensure conformance with this test method.3.1.5 surface finishall references to surface finish in thistest method are defined as surface roughness (that is, Ra
10、=average roughness value).4. Significance and Use4.1 The hardness of a material is a defined quantity havingmany scales and being dependent on the way the test isperformed. In order to avoid the creation of a new methodinvolving a new hardness scale, the UCI method converts intocommon hardness value
11、s, for example, HV, HRC, etc.4.2 The UCI hardness test is a superficial determination,only measuring the hardness condition of the surface con-tacted. The results generated at a specific location do not1This test method is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Rel
12、ated Alloys and is the direct responsibility of SubcommitteeA01.06 on Steel Forgings and Billets.Current edition approved Nov. 1, 2010. Published November 2010. Originallyapproved in 2005. Last previous edition approved in 2010 as A1038 10. DOI:10.1520/A1038-10A.2For referenced ASTM standards, visit
13、 the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 1
14、00 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.represent the part at any other surface location and yield noinformation about the material at subsurface locations.4.3 The UCI hardness test may be used on large or smallcomponents at various locations. It can be use
15、d to makehardness measurements on positions difficult to access, such astooth flanks or roots of gears.A. GENERAL DESCRIPTION OF INSTRUMENTSAND TEST PROCEDURE FOR UCI HARDNESSTESTING5. Apparatus5.1 Instruments used for UCI hardness testing generallyconsist of (1) a probe containing a rod with a defi
16、ned indenter,for example, a Vickers diamond, attached to the contacting endper Test Method E384, (2) vibration generating means, (3)vibration detecting means, (4) electronic means for the numeri-cal evaluation, and (5) a digital display, indicating the mea-sured hardness number.5.2 UCI ProbesThere a
17、re different probes available forUCI hardness testing. They typically cover static loads rangingfrom1Nto98N.Seealso Appendix X1. They come also indifferent sizes with longer and shorter sensor rods for specialsapplications. And they are developed in two versions, that is,manually operated or equippe
18、d with a servo-motor for auto-matic testing.5.3 Summary of Test MethodIn conventional workbenchhardness testing like Brinell or Vickers testing according toTest Methods E10 and E384, the hardness value is determinedoptically by the size of the indentation in the material generatedby a certain test l
19、oad, after the indenter has been removed. Inthe mobile hardness test under applied load according to theUCI method, however, the size of the produced indents are notdetermined optically. Instead the contact area is derived fromthe electronically measured shift of an ultrasonic resonancefrequency. To
20、 carry out the UCI test, a probe containing the rodwith the indenter is excited into a longitudinal ultrasonicoscillation of about 70 kHz by piezoelectric ceramicstheso-called zero frequency, which occurs when the indenter isvibrating in air.5.3.1 A spring inside the probe applies the specified test
21、load, the vibrating tip penetrates into the material creating anelastic contact, which results in a positive frequency shift of theresonating rod. This shift is related to the size of the indent area(contact area of the indenter with the material). The size, inturn, is a measure for the hardness of
22、the test material at a givenmodulus of elasticity, for example, HV(UCI) according to Eq1.5.3.2 Therefore, the frequency shift is relatively small forhard materials, because the indenter penetrates not very deepinto the test material leaving only a small indent.5.3.3 The frequency shift becomes large
23、r if the indenterpenetrates deeper into the material, indicating medium hard-ness, in accordance with the larger test indentations. Analo-gously, the frequency shift becomes largest when soft materialsare tested (see Fig. 2).5.3.4 The instrument constantly monitors the resonancefrequency, calculates
24、 the frequency shift when the specifiedtest load has been reached either after the internal switch hastriggered the corresponding measurement frequency in the caseof handheld probes or after a specific dwell time has beenelapsed in the case of motor driven probes. The instrumentcarries out the evalu
25、ation and calculations, and displays instan-taneously the hardness value, for example, HV(UCI).UCI Vickers (1)Df 5 fEeff A! and HV 5FA_5.3.5 The frequency shift is a function of the indentationsize of a defined indenter, for example, a Vickers diamond, ata given modulus of elasticity of the measurem
26、ent system.5.3.6 Eq 1 describes the basic relation in comparison to thedefinition of the Vickers hardness value: Df = Frequency shift,A = indentation area, Eeff= effective elastic modulus (containsthe elastic constants of both the indenter and the test piece), HV= Vickers hardness value, F = Force a
27、pplied in the hardnesstest.5.4 The Influence of the Elastic ConstantsAs can be seenin Eq 1, the frequency shift not only depends on the size of thecontact area but also on the elastic moduli of the materials incontact. To allow for differences in Youngs modulus, theLegend:T = Piezo TransducerR = Rec
28、eiverO = Oscillating rodV = indenter, for example, Vickers diamondm = test materialFIG. 1 Schematic Description of the UCI ProbeFIG. 2 Hardness Value versus Frequency Shift of the OscillatingRodA1038 10a2instrument has to be calibrated for different groups of materi-als. After calibration, the UCI m
29、ethod can be applied to allmaterials, which have the corresponding Youngs modulus.5.4.1 As manufactured, the UCI instrument usually has beencalibrated on non-alloyed and low-alloyed steel, that is, certi-fied hardness reference blocks according to Test Method E384.Besides this, some instruments may
30、be calibrated quickly, alsoat the test site, for metals such as high-alloyed steels, aluminumor titanium.6. Calibration to Other Materials6.1 A test piece of the particular material is needed. Thehardness value should then be determined with a standardizedworkbench hardness tester like one for Vicke
31、rs, Brinell orRockwell according to Test Methods and Definitions A370.Itis recommended to take at least 5 readings and calculate theaverage hardness value. Now carry out a set of at least 5 singleUCI measurements on your test material according to instruc-tions in 10.6, adjust the displayed average
32、value to the beforemeasured hardness of the material and thus find the calibrationvalue which is necessary for further measurements on thisparticular material in the desired hardness scale and range.6.1.1 Some instruments allow storing all calibration dataand adjustment parameters for hardness testi
33、ng of differentmaterials. They can be recalled to the instrument as needed.7. Comparison with Other Hardness Testing Methods7.1 As opposed to conventional low load hardness testers,the UCI instruments do not evaluate the indentation sizemicroscopically but electronically according to the UCImethod.
34、The UCI method yields comparative hardness mea-surements when considering the dependency on the elasticmodulus of the test piece.7.2 After removing the test force, an indentation generatedby the UCI probe using a Vickers diamond as indenter andmounted in a test stand is practically identical to a Vi
35、ckersindentation produced by a workbench tester of the same load.The indentation can be measured optically according to thestandard Vickers test if care is taken to apply the forceaccording to Test Method E384 and if a Vickers indenter isused in the UCI probe. In this case special arrangements orpro
36、be attachments have to be used to provide verification of theactual test force of the UCI probe.8. Test Piece8.1 Surface PreparationThe applied test force (that is, theselected UCI probe) must not only match the application butalso the surface quality and roughness of the material. Whilesmooth, homo
37、geneous surfaces can be tested with low testloads, rougher and coarse-grained surfaces require test loads ashigh as possible. However, the surface must always be free ofany impurities (oil, dust, etc.) and rust.8.1.1 The surface roughness should not exceed 30 % ofthe penetration depth (Ra# 0.3 3 h)
38、with:hmm 5 0.062 3Force NHardness HV(2)8.1.2 Penetration depth of the Vickers diamond pyramid fora certain hardness (in HV) and test load (in N) id is shown inEq 2.8.1.3 Table 1 provides the recommended minimal surfaceroughness for certain UCI probes that use a Vickers indenter. Ifsurface preparatio
39、n is necessary, care must be taken not to alterthe surface hardness by overheating or cold working. Anypaint, scale or other surface coatings shall be completelyremoved. Failure to provide adequate surface finish willproduce unsteady readings. Coarse finishes will tend to lowerthe measured value.8.2
40、 Minimum ThicknessThin coatings or surface layers onbulk material must have a minimum thickness of at least tentimes of the indentation depth of the indenter used (see Fig. 3for a Vickers indenter) corresponding to the Bueckles rule:Smin=103 h.8.3 Minimum Wall ThicknessDistinct reading variationsmay
41、 especially occur with a specimen thickness of less thanabout 15 mm (58 in.) if the test material is excited to resonanceor sympathetic oscillations (for example, thin blocks, tubes,pipes, etc.). Most disturbing are flexural vibrations excited bythe vibrating tip. These should be suppressed by suita
42、blemeans. Sometimes attaching the test piece to a heavy metalblock by means of a viscous paste, grease or oil film suffices toquench the flexural waves. Nevertheless, a minimum wallthickness of 2 to 3 mm (332 to18 in.) is recommended.8.4 Influence of the OscillationThe UCI method is basedon measurin
43、g a frequency shift. Parts less than about 300 g cango into self-oscillating causing erroneous or erratic readings.Test pieces of weights less than the minimum or pieces of anyweight with sections less than the minimum thickness requirerigid support and coupling to a thick, heavier non-yieldingsurfa
44、ce to resist the oscillation of the UCI probe. Failure toprovide adequate support and coupling will produce test resultslower or higher than the true hardness value.8.5 Surface CurvatureTest pieces with curved surfacesmay be tested on either the convex or concave surfacesproviding that the radius of
45、 curvature of the specimens ismatched to the appropriate probe and probe attachment in orderto ensure a perpendicular positioning of the probe.8.6 TemperatureThe temperature of the test piece mayaffect the results of the UCI hardness test. However, if theprobe is exposed to elevated temperature for
46、only the time ofmeasurement, measurements are possible at temperatureshigher than room temperature, without influencing the perfor-mance of the UCI instrument.9. Verification of the Apparatus9.1 Verification MethodPrior to each shift or work periodthe instrument shall be verified as specified in Par
47、t B. Any UCIhardness testing instrument not meeting the requirements ofPart B shall not be used for the acceptance testing of products.10. Procedure10.1 Test ProcedureTo perform a hardness test, the probeis connected to the indicating unit and the instrument is turnedTABLE 1 Surface Finish for Diffe
48、rent Test LoadsTest Load 98 N 50 N 10 N 3 NRa # 15 m # 10 m # 5m # 2.5 mA1038 10a3on. The probe is held firmly (using a probe grip if needed) withits axis in a perpendicular position relative to the test piecesurface. Hold the probe with both hands to achieve the bestpossible result. Carefully exert
49、 steady pressure against the testpiece during the loading phase. Make sure that the verticalprobe position is maintained as long as the load is effective.Some instruments indicate the end of the measurement by anacoustic signal and display the hardness value instantaneously.10.2 AlignmentTo prevent errors from misalignmentmove the UCI probe with slow and steady speed. The probeshould be perpendicular with respect to the surface. Themaximum angular deviation from the perpendicular positionshould be less than 5 degrees. Avoid t
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1