ASTM G32-2010 Standard Test Method for Cavitation Erosion Using Vibratory Apparatus《使用振动装置检测气蚀侵蚀的标准试验方法》.pdf

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1、Designation: G32 10Standard Test Method forCavitation Erosion Using Vibratory Apparatus1This standard is issued under the fixed designation G32; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision.Anumber in p

2、arentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the production of cavitationdamage on the face of a specimen vibrated at high frequencywhile immersed in a liquid. The vibra

3、tion induces the forma-tion and collapse of cavities in the liquid, and the collapsingcavities produce the damage to and erosion (material loss) ofthe specimen.1.2 Although the mechanism for generating fluid cavitationin this method differs from that occurring in flowing systemsand hydraulic machine

4、s (see 5.1), the nature of the materialdamage mechanism is believed to be basically similar. Themethod therefore offers a small-scale, relatively simple andcontrollable test that can be used to compare the cavitationerosion resistance of different materials, to study in detail thenature and progress

5、 of damage in a given material, orbyvarying some of the test conditionsto study the effect of testvariables on the damage produced.1.3 This test method specifies standard test conditionscovering the diameter, vibratory amplitude and frequency ofthe specimen, as well as the test liquid and its contai

6、ner. Itpermits deviations from some of these conditions if properlydocumented, that may be appropriate for some purposes. Itgives guidance on setting up a suitable apparatus and coverstest and reporting procedures and precautions to be taken. Italso specifies standard reference materials that must b

7、e used toverify the operation of the facility and to define the normalizederosion resistance of other test materials.1.4 A history of this test method is given in Appendix X4,followed by a comprehensive bibliography.1.5 The values stated in SI units are to be regarded asstandard. The inch-pound unit

8、s given in parentheses are forinformation only.1.6 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 establish appro-priate safety and health practices and determine the applica-bility of regu

9、latory limitations prior to use. For specific safetywarning information, see 6.1, 10.3, and 10.6.1.2. Referenced Documents2.1 ASTM Standards:2A276 Specification for Stainless Steel Bars and ShapesB160 Specification for Nickel Rod and BarB211 Specification for Aluminum and Aluminum-AlloyBar, Rod, and

10、 WireD1193 Specification for Reagent WaterE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE960 Specification for Laboratory Glass BeakersG40 Terminology Relating to Wear and Erosi

11、onG73 Test Method for Liquid Impingement Erosion UsingRotating ApparatusG117 Guide for Calculating and Reporting Measures ofPrecision Using Data from Interlaboratory Wear or Ero-sion TestsG119 Guide for Determining Synergism Between Wear andCorrosionG134 Test Method for Erosion of Solid Materials by

12、 Cavi-tating Liquid Jet3. Terminology3.1 Definitions:3.1.1 See Terminology G40 for definitions of terms relatingto cavitation erosion. For convenience, important definitionsfor this standard are listed below; some are slightly modifiedfrom Terminology G40 or not contained therein.3.1.2 average erosi

13、on rate, na less preferred term forcumulative erosion rate.3.1.3 cavitation, nthe formation and subsequent collapse,within a liquid, of cavities or bubbles that contain vapor or amixture of vapor and gas.3.1.3.1 DiscussionIn general, cavitation originates from alocal decrease in hydrostatic pressure

14、 in the liquid, producedby motion of the liquid (see flow cavitation) or of a solidboundary (see vibratory cavitation). It is distinguished in thisway from boiling, which originates from an increase in liquidtemperature.1This test method is under the jurisdiction of ASTM Committee G02 on Wearand Ero

15、sion and is the direct responsibility of Subcommittee G02.10 on Erosion bySolids and Liquids.Current edition approved Dec. 1, 2010. Published February 2011. Originallyapproved in 1972. Last previous edition approved in 2009 as G3209. DOI:10.1520/G0032-10.2For referenced ASTM standards, visit the AST

16、M 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Unite

17、d States.3.1.3.2 DiscussionThe term cavitation, by itself, shouldnot be used to denote the damage or erosion of a solid surfacethat can be caused by it; this effect of cavitation is termedcavitation damage or cavitation erosion. To erode a solidsurface, bubbles or cavities must collapse on or near t

18、hatsurface.3.1.4 cavitation erosion, nprogressive loss of originalmaterial from a solid surface due to continued exposure tocavitation.3.1.5 cumulative erosion, nthe total amount of materiallost from a solid surface during all exposure periods since itwas first exposed to cavitation or impingement a

19、s a newlyfinished surface. (More specific terms that may be used arecumulative mass loss, cumulative volume loss,orcumulativemean depth of erosion. See also cumulative erosion-timecurve.)3.1.5.1 DiscussionUnless otherwise indicated by the con-text, it is implied that the conditions of cavitation or

20、impinge-ment have remained the same throughout all exposure periods,with no intermediate refinishing of the surface.3.1.6 cumulative erosion rate, nthe cumulative erosion ata specified point in an erosion test divided by the correspond-ing cumulative exposure duration; that is, the slope of a linefr

21、om the origin to the specified point on the cumulativeerosion-time curve. (Synonym: average erosion rate)3.1.7 cumulative erosion-time curvea plot of cumulativeerosion versus cumulative exposure duration, usually deter-mined by periodic interruption of the test and weighing of thespecimen. This is t

22、he primary record of an erosion test. Mostother characteristics, such as the incubation period, maximumerosion rate, terminal erosion rate, and erosion rate-time curve,are derived from it.3.1.8 erosion rate-time curve, na plot of instantaneouserosion rate versus exposure duration, usually obtained b

23、ynumerical or graphical differentiation of the cumulativeerosion-time curve. (See also erosion rate-time pattern.)3.1.9 erosion rate-time pattern, nany qualitative descrip-tion of the shape of the erosion rate-time curve in terms of theseveral stages of which it may be composed.3.1.9.1 DiscussionIn

24、cavitation and liquid impingementerosion, a typical pattern may be composed of all or some ofthe following “periods” or “stages”: incubation period, accel-eration period, maximum-rate period, deceleration period,terminal period, and occasionally catastrophic period. Thegeneric term “period” is recom

25、mended when associated withquantitative measures of its duration, etc.; for purely qualitativedescriptions the term“ stage” is preferred.3.1.10 erosion threshold time, nthe exposure time re-quired to reach a mean depth of erosion of 1.0 m.3.1.10.1 DiscussionA mean depth of erosion of 1.0 m isthe lea

26、st accurately measurable value considering the precisionof the scale, specimen diameter, and density of the standardreference material.3.1.11 flow cavitation, ncavitation caused by a decrease inlocal pressure induced by changes in velocity of a flowingliquid, such as in flow around an obstacle or th

27、rough aconstriction.3.1.12 incubation period, nthe initial stage of the erosionrate-time pattern during which the erosion rate is zero ornegligible compared to later stages.3.1.12.1 DiscussionThe incubation period is usuallythought to represent the accumulation of plastic deformationand internal str

28、esses under the surface, that precedes significantmaterial loss. There is no exact measure of the duration of theincubation period. See related terms, erosion threshold timeand nominal incubation period.3.1.13 maximum erosion rate, nthe maximum instanta-neous erosion rate in a test that exhibits suc

29、h a maximumfollowed by decreasing erosion rates. (See also erosion rate-time pattern.)3.1.13.1 DiscussionOccurrence of such a maximum istypical of many cavitation and liquid impingement tests. Insome instances it occurs as an instantaneous maximum, inothers as a steady-state maximum which persists f

30、or sometime.3.1.14 mean depth of erosion (MDE), nthe average thick-ness of material eroded from a specified surface area, usuallycalculated by dividing the measured mass loss by the density ofthe material to obtain the volume loss and dividing that by thearea of the specified surface. (Also known as

31、 mean depth ofpenetration or MDP. Since that might be taken to denote theaverage value of the depths of individual pits, it is a lesspreferred term.)3.1.15 nominal incubation time, nthe intercept on thetime or exposure axis of the straight-line extension of themaximum-slope portion of the cumulative

32、 erosion-time curve;while this is not a true measure of the incubation stage, itserves to locate the maximum erosion rate line on the cumu-lative erosion versus time coordinates.3.1.16 normalized erosion resistance, Ne, na measure ofthe erosion resistance of a test material relative to that of aspec

33、ified reference material, calculated by dividing the volumeloss rate of the reference material by that of the test material,when both are similarly tested and similarly analyzed. By“similarly analyzed” is meant that the two erosion rates mustbe determined for corresponding portions of the erosion ra

34、tetime pattern; for instance, the maximum erosion rate or theterminal erosion rate.3.1.16.1 DiscussionA recommended complete wordinghas the form, “The normalized erosion resistance of (testmaterial) relative to (reference material) based on (criterion ofdata analysis) is (numerical value).”3.1.17 no

35、rmalized incubation resistance No, nthe nominalincubation time of a test material, divided by the nominalincubation time of a specified reference material similarlytested and similarly analyzed. (See also normalized erosionresistance.)3.1.18 tangent erosion rate, nthe slope of a straight linedrawn t

36、hrough the origin and tangent to the knee of thecumulative erosion-time curve, when that curve has the char-acteristic S-shaped pattern that permits this. In such cases, thetangent erosion rate also represents the maximum cumulativeerosion rate exhibited during the test.G321023.1.19 terminal erosion

37、 rate, nthe final steady-state ero-sion rate that is reached (or appears to be approached asymp-totically) after the erosion rate has declined from its maximumvalue. (See also terminal period and erosion rate-time pattern.)3.1.20 vibratory cavitation, ncavitation caused by thepressure fluctuations w

38、ithin a liquid, induced by the vibrationof a solid surface immersed in the liquid.4. Summary of Test Method4.1 This test method generally utilizes a commerciallyobtained 20-kHz ultrasonic transducer to which is attached asuitably designed “horn” or velocity transformer. A specimenbutton of proper ma

39、ss is attached by threading into the tip ofthe horn.4.2 The specimen is immersed into a container of the testliquid (generally distilled water) that must be maintained at aspecified temperature during test operation, while the specimenis vibrated at a specified amplitude. The amplitude andfrequency

40、of vibration of the test specimen must be accuratelycontrolled and monitored.4.3 The test specimen is weighed accurately before testingbegins and again during periodic interruptions of the test, inorder to obtain a history of mass loss versus time (which is notlinear). Appropriate interpretation of

41、this cumulative erosion-versus-time curve permits comparison of results betweendifferent materials or between different test fluids or otherconditions.5. Significance and Use5.1 This test method may be used to estimate the relativeresistance of materials to cavitation erosion as may be encoun-tered,

42、 for instance, in pumps, hydraulic turbines, hydraulicdynamometers, valves, bearings, diesel engine cylinder liners,ship propellers, hydrofoils, and in internal flow passages withobstructions.An alternative method for similar purposes is TestMethod G134, which employs a cavitating liquid jet to prod

43、uceerosion on a stationary specimen. The latter may be moresuitable for materials not readily formed into a preciselyshaped specimen. The results of either, or any, cavitationerosion test should be used with caution; see 5.8.5.2 Some investigators have also used this test method as ascreening test f

44、or materials subjected to liquid impingementerosion as encountered, for instance, in low-pressure steamturbines and in aircraft, missiles or spacecraft flying throughrainstorms. Test Method G73 describes another testing ap-proach specifically intended for that type of environment.5.3 This test metho

45、d is not recommended for evaluatingelastomeric or compliant coatings, some of which have beensuccessfully used for protection against cavitation or liquidimpingement of moderate intensity. This is because the com-pliance of the coating on the specimen may reduce the severityof the liquid cavitation

46、induced by its vibratory motion. Theresult would not be representative of a field application, wherethe hydrodynamic generation of cavitation is independent ofthe coating.NOTE 1An alternative approach that uses the same basic apparatus,and is deemed suitable for compliant coatings, is the “stationar

47、y speci-men” method. In that method, the specimen is fixed within the liquidcontainer, and the vibrating tip of the horn is placed in close proximity toit. The cavitation “bubbles” induced by the horn (usually fitted with ahighly resistant replaceable tip) act on the specimen. While severalinvestiga

48、tors have used this approach (see X4.2.3), they have differed withregard to standoff distances and other arrangements. The stationaryspecimen approach can also be used for brittle materials which can not beformed into a threaded specimen nor into a disc that can be cemented toa threaded specimen, as

49、 required for this test method (see 7.6).5.4 This test method should not be directly used to rankmaterials for applications where electrochemical corrosion orsolid particle impingement plays a major role. However,adaptations of the basic method and apparatus have been usedfor such purposes (see 9.2.5, 9.2.6, and X4.2). Guide G119may be followed in order to determine the synergism betweenthe mechanical and electrochemical effects.5.5 Those who are engaged in basic research, or concernedwith very specialized applications, may need to vary some ofthe test