1、Designation: A1038 10Standard Practice 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 of la
2、st 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 practice covers the determination of comparativehardness values by applying the Ultrasonic Contact ImpedanceMethod
3、 (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 standard to
4、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 MaterialsE18
5、 Test Methods for Rockwell Hardness of Metallic Ma-terialsE92 Test Method for Vickers Hardness of Metallic Materi-alsE140 Hardness Conversion Tables for Metals RelationshipAmong Brinell Hardness, Vickers Hardness, RockwellHardness, Superficial Hardness, Knoop Hardness, andScleroscope HardnessE177 Pr
6、actice for Use of the Terms Precision and Bias inASTM 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 h
7、ard-ness testing method developed by Dr. Claus Kleesattel 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
8、testing practice using acalibrated instrument by pressing 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 in
9、strument bycomparison with values indicated by a standardized workbenchhardness tester or by a set of certified reference test pieces.3.1.4 verificationchecking or testing the UCI instrumentto ensure conformance with this practice.3.1.5 surface finishall references to surface finish in thispractice
10、are defined as surface roughness (that is, Ra = averageroughness 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 practiceinvolving a new hardness scale, t
11、he UCI method converts intocommon hardness values, 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 notrepresent the part at any other surface location a
12、nd yield noinformation about the material at subsurface locations.1This practice is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloys and is the direct responsibility of SubcommitteeA01.06 on Steel Forgings and Billets.Current edition approved May 15, 2010. Pub
13、lished June 2010. Originallyapproved in 2005. Last previous edition approved in 2008 as A1038 08. DOI:10.1520/A1038-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer
14、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, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.3 The UCI hardness test may be used on large or smallcompon
15、ents at various locations. It can be used 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
16、(1) a probe containing a rod with a defined indenter,for example, a Vickers diamond, attached to the contacting endper Test Method E92 and Test Method E384, (2) vibrationgenerating means, (3) vibration detecting means, (4) electronicmeans for the numerical evaluation, and (5) a digital display,indic
17、ating the measured hardness number.5.2 UCI ProbesThere are 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 develop
18、ed in two versions, that is,manually operated or equipped with a servo-motor for auto-matic testing.5.3 Summary of PracticeIn conventional workbenchhardness testing like Brinell or Vickers testing according toTest Methods E10, E92, and E384, the hardness value isdetermined optically by the size of t
19、he indentation in thematerial generated by a certain test load, after the indenter hasbeen removed. In the mobile hardness test under applied loadaccording to the UCI method, however, the size of theproduced indents are not determined optically. Instead thecontact area is derived from the electronic
20、ally measured shiftof an ultrasonic resonance frequency. To carry out the UCI test,a probe containing the rod with the indenter is excited into alongitudinal ultrasonic oscillation of about 70 kHz by piezo-electric ceramicsthe so-called zero frequency, which occurswhen the indenter is vibrating in a
21、ir.5.3.1 A spring inside the probe applies the specified testload, 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 m
22、aterial). The size, inturn, is a measure for the hardness of 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 leavin
23、g only a small indent.5.3.3 The frequency shift becomes larger 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 inst
24、rument constantly monitors the resonancefrequency, calculates 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 cas
25、e of motor driven probes. The instrumentcarries out the evaluation 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 Vic
26、kers diamond, ata given modulus of elasticity of the measurement 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
27、 and the test piece), HV= Vickers hardness value, F = Force applied 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 differe
28、nces in Youngs modulus, theLegend:T = Piezo TransducerR = ReceiverO = 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 102instrument has to be calibrated for
29、different groups of materi-als. After calibration, the UCI method 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 accor
30、ding to Test Method E92.Besides this, some instruments may 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
31、 a standardizedworkbench hardness tester like one for Vickers, 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 accord
32、ing to instruc-tions in 10.6, adjust the displayed average 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 c
33、alibration dataand adjustment parameters for hardness testing 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 sizemicr
34、oscopically but electronically according to the UCImethod. 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
35、andmounted in a test stand is practically identical to a Vickersindentation 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 E92 and if a Vickers indenter is use
36、din the UCI probe. In this case special arrangements or probeattachments 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 surfac
37、e quality and roughness of the material. Whilesmooth, homogeneous 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 sho
38、uld not exceed 30 % ofthe penetration depth (Ra# 0.3 3 h) 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 UC
39、I probes that use a Vickers indenter. Ifsurface preparation 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
40、. Coarse finishes will tend to lowerthe measured value.8.2 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
41、h.8.3 Minimum Wall ThicknessDistinct reading variationsmay 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 excite
42、d bythe vibrating tip. These should be suppressed by suitablemeans. 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 Infl
43、uence of the OscillationThe UCI method is basedon measuring 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
44、support and coupling to a thick, heavier non-yieldingsurface 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
45、the convex or concave surfacesproviding that the radius of 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. Ho
46、wever, if theprobe is exposed to elevated temperature for 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
47、periodthe instrument shall be verified as specified in Part 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 an
48、d the instrument is turnedTABLE 1 Surface Finish for Different Test LoadsTest Load 98 N 50 N 10 N 3 NRa # 15 m # 10 m # 5m # 2.5 mA1038 103on. 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
49、hands to achieve the bestpossible result. Carefully exert 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 per
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