1、Designation: A1038 131A1038 17Standard 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, th
2、e year of 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 NOTETable 3 heading was corrected editorially in April 2016.1. Scope*1.1 This test method covers the determination of
3、comparative hardness values by applying the Ultrasonic Contact ImpedanceMethod (UCI Method).1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any,
4、associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with inter
5、nationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2A370 Te
6、st Methods and Definitions for Mechanical Testing of Steel ProductsE10 Test Method for Brinell Hardness of Metallic MaterialsE18 Test Methods for Rockwell Hardness of Metallic MaterialsE140 Hardness Conversion Tables for Metals Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness
7、,Superficial Hardness, Knoop Hardness, Scleroscope Hardness, and Leeb HardnessE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE384 Test Method for Microindentation Hardness of MaterialsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Tes
8、t Method3. Terminology and Equations3.1 Definitions:3.1.1 calibrationdetermination of the specific values of the significant operating parameters of the UCI instrument bycomparison with values indicated by a standardized workbench hardness tester or by a set of certified reference test pieces.3.1.2
9、surface finishall references to surface finish in this test method are defined as surface roughness (that is, Ra = averageroughness value).3.1.3 UCI hardness testa hardness testing method using a calibrated instrument by pressing a resonating rod with a definedindenter, for example, a Vickers diamon
10、d, with a fixed force against the surface of the part to be tested.3.1.4 UCI methodUltrasonic Contact Impedance, a hardness testing method developed by Dr. Claus Kleesattel in 1961 basedon the measurement of the frequency shift of a resonating rod caused by the essentially elastic nature of the fini
11、te area of contactbetween the indenter and the test piece during the penetration.3.1.5 verificationchecking or testing the UCI instrument to ensure conformance with this test method.1 This test method is under the jurisdiction ofASTM Committee A01 on Steel, Stainless Steel and RelatedAlloys and is t
12、he direct responsibility of Subcommittee A01.06on Steel Forgings and Billets.Current edition approved Nov. 1, 2013Nov. 1, 2017. Published March 2014December 2017. Originally approved in 2005. Last previous edition approved in 20102013 asA1038 10a.A1038 131. DOI: 10.1520/A1038-13E01.10.1520/A1038-17.
13、2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to
14、 provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof
15、 the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 Equations:3.2.1 The average x of a set o
16、f n measurements x1,x2, ., xn is calculated as:x 5x11x21.1xnn (1)where each of the individual measurements x1,x2, ., xn is the result from a single indentation.3.2.2 The error E in the performance of an ultrasonic contact impedance hardness testing instrument at each hardness level,relative to a sta
17、ndardized reference value, is calculated as an absolute percent error determined as:E 5U1003Sx 2xrefxrefDU (2)where:x = the average (see 3.2.1) of n measurements made on a standard reference block as part of a performance verification, andxref = the certified reference hardness reported for the stan
18、dard reference block.4. Significance and Use4.1 The hardness of a material is a defined quantity having many scales and being dependent on the way the test is performed.In order to avoid the creation of a new method involving a new hardness scale, the UCI method converts into common hardnessvalues,
19、for example, HV, HRC, etc.4.2 The UCI hardness test is a superficial determination, only measuring the hardness condition of the surface contacted. Theresults generated at a specific location do not represent the part at any other surface location and yield no information about thematerial at subsur
20、face locations.4.3 The UCI hardness test may be used on large or small components at various locations. It can be used to make hardnessmeasurements on positions difficult to access, such as tooth flanks or roots of gears.A. GENERAL DESCRIPTION OF INSTRUMENTS AND TEST PROCEDURE FOR UCI HARDNESS TESTI
21、NG5. Apparatus5.1 Instruments used for UCI hardness testing generally consist of (1) a probe containing a rod with a defined indenter, forexample, a Vickers diamond, attached to the contacting end per Test Method E384 (see Fig. 1), (2) vibration generating means,(3) vibration detecting means, (4) el
22、ectronic means for the numerical evaluation, and (5) a digital display, indicating the measuredhardness number.5.2 UCI ProbesThere are different probes available for UCI hardness testing. They typically cover static loads ranging from1 N to 98 N. See also Appendix X1. They come also in different siz
23、es with longer and shorter sensor rods for specials applications.And they are developed in two versions, that is, manually operated or equipped with a servo-motor for automatic testing.Legend:T = Piezo TransducerR = ReceiverO = Oscillating rodV = indenter, for example, Vickers diamondm = test materi
24、alFIG. 1 Schematic Description of the UCI ProbeA1038 1725.3 Summary of Test MethodIn conventional workbench hardness testing like Brinell or Vickers testing according to TestMethods E10 and E384, the hardness value is determined optically by the size of the indentation in the material generated by a
25、certain test load, after the indenter has been removed. In the mobile hardness test under applied load according to the UCI method,however, the size of the produced indents are not determined optically. Instead the contact area is derived from the electronicallymeasured shift of an ultrasonic resona
26、nce frequency. To carry out the UCI test, a probe containing the rod with the indenter isexcited into a longitudinal ultrasonic oscillation of about 70 kHz by piezoelectric ceramicsthe so-called zero frequency, whichoccurs when the indenter is vibrating in air.5.3.1 A spring inside the probe applies
27、 the specified test load, the vibrating tip penetrates into the material creating an elasticcontact, which results in a positive frequency shift of the resonating rod. This shift is related to the size of the indent area (contactarea of the indenter with the material). The size, in turn, is a measur
28、e for the hardness of the test material at a given modulus ofelasticity, for example, HV(UCI) according to Eq 13.5.3.2 Therefore, the frequency shift is relatively small for hard materials, because the indenter penetrates not very deep into thetest material leaving only a small indent.5.3.3 The freq
29、uency shift becomes larger if the indenter penetrates deeper into the material, indicating medium hardness, inaccordance with the larger test indentations. Analogously, the frequency shift becomes largest when soft materials are tested (seeFig. 2).5.3.4 The instrument constantly monitors the resonan
30、ce frequency, calculates the frequency shift when the specified test loadhas been reached either after the internal switch has triggered the corresponding measurement frequency in the case of handheldprobes or after a specific dwell time has been elapsed in the case of motor driven probes. The instr
31、ument carries out the evaluationand calculations, and displays instantaneously the hardness value, for example, HV(UCI).UCI Vickers (3)f 5fEeffA! and HV5FA_5.3.5 The frequency shift is a function of the indentation size of a defined indenter, for example, a Vickers diamond, at a givenmodulus of elas
32、ticity of the measurement system.5.3.6 Eq 13 describes the basic relation in comparison to the definition of the Vickers hardness value: f = Frequency shift, A= indentation area, Eeff = effective elastic modulus (contains the elastic constants of both the indenter and the test piece), HV =Vickers ha
33、rdness value, F = Force applied in the hardness test.5.4 The Influence of the Elastic ConstantsAs can be seen in Eq 13, the frequency shift not only depends on the size of thecontact area but also on the elastic moduli of the materials in contact. To allow for differences in Youngs modulus, the inst
34、rumenthas to be calibrated for different groups of materials.After calibration, the UCI method can be applied to all materials, which havethe corresponding Youngs modulus.5.4.1 As manufactured, the UCI instrument usually has been calibrated on non-alloyed and low-alloyed steel, that is, certifiedhar
35、dness reference blocks according to Test Method E384. Besides this, some instruments may be calibrated quickly, also at thetest site, for metals such as high-alloyed steels, aluminum or titanium.6. Calibration to Other Materials6.1 A test piece of the particular material is needed. The hardness valu
36、e should then be determined with a standardizedworkbench hardness tester like one for Vickers, Brinell or Rockwell according to Test Methods and Definitions A370. It isFIG. 2 Hardness Value versus Frequency Shift of the Oscillating RodA1038 173recommended to take at least five readings and calculate
37、 the average hardness value. Now carry out a set of at least five singleUCI measurements on your test material according to instructions in 10.6, adjust the displayed average value to the beforemeasured hardness of the material and thus find the calibration value which is necessary for further measu
38、rements on this particularmaterial in the desired hardness scale and range.6.1.1 Some instruments allow storing all calibration data and adjustment parameters for hardness testing of different materials.They can be recalled to the instrument as needed.7. Comparison with Other Hardness Testing Method
39、s7.1 As opposed to conventional low load hardness testers, the UCI instruments do not evaluate the indentation sizemicroscopically but electronically according to the UCI method. The UCI method yields comparative hardness measurementswhen considering the dependency on the elastic modulus of the test
40、 piece.7.2 After removing the test force, an indentation generated by the UCI probe using a Vickers diamond as indenter and mountedin a test stand is practically identical to a Vickers indentation produced by a workbench tester of the same load. The indentationcan be measured optically according to
41、the standard Vickers test if care is taken to apply the force according to Test Method E384and if aVickers indenter is used in the UCI probe. In this case special arrangements or probe attachments have to be used to provideverification of the actual test force of the UCI probe.8. Test Piece8.1 Surfa
42、ce PreparationThe applied test force (that is, the selected UCI probe) must not only match the application but alsothe surface quality and roughness of the material. While smooth, homogeneous surfaces can be tested with low test loads, rougherand coarse-grained surfaces require test loads as high as
43、 possible. However, the surface must always be free of any impurities (oil,dust, etc.) and rust.8.1.1 The surface roughness should not exceed 30 % of the penetration depth (Ra 0.3 h) with:hmm#50.0623 Force N#Hardness HV# (4)8.1.2 Penetration depth of the Vickers diamond pyramid for a certain hardnes
44、s (in HV) and test load (in N) id is shown in Eq24.8.1.3 Table 1 provides the recommended minimal surface roughness for certain UCI probes that use a Vickers indenter. Ifsurface preparation is necessary, care must be taken not to alter the surface hardness by overheating or cold working. Any paint,s
45、cale or other surface coatings shall be completely removed. Failure to provide adequate surface finish will produce unsteadyreadings. Coarse finishes will tend to lower the measured value.8.2 Minimum ThicknessThin coatings or surface layers on bulk material must have a minimum thickness of at least
46、ten timesof the indentation depth of the indenter used (see Fig. 3 for a Vickers indenter) corresponding to the Bueckles rule: Smin = 10 h.8.3 Minimum Wall ThicknessDistinct reading variations may especially occur with a specimen thickness of less than about 15mm if the test material is excited to r
47、esonance or sympathetic oscillations (for example, thin blocks, tubes, pipes, etc.). Mostdisturbing are flexural vibrations excited by the vibrating tip. These should be suppressed by suitable means. Sometimes attachingthe test piece to a heavy metal block by means of a viscous paste, grease or oil
48、film suffices to quench the flexural waves.Nevertheless, a minimum wall thickness of 2 to 3 mm is recommended.8.4 Influence of the OscillationThe UCI method is based on measuring a frequency shift. Parts less than about 300 g can gointo self-oscillating causing erroneous or erratic readings. Test pi
49、eces of weights less than the minimum or pieces of any weightwith sections less than the minimum thickness require rigid support and coupling to a thick, heavier non-yielding surface to resistthe oscillation of the UCI probe. Failure to provide adequate support and coupling will produce test results lower or higher thanthe true hardness value.8.5 Surface CurvatureTest pieces with curved surfaces may be tested on either the convex or concave surfaces providing thatthe radius of curvature of the specimens is matched to the
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