ASTM G32-2016 Standard Test Method for Cavitation Erosion Using Vibratory Apparatus《使用振动装置的空隙腐蚀的标准试验方法》.pdf

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1、Designation: G32 16Standard 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-AlloyRolled or Col

10、d Finished Bar, Rod, and 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 Re

11、lating to Wear and ErosionG73 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 Erosi

12、on of Solid Materials by 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 the

13、rein.3.1.2 average erosion 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

14、 in hydrostatic pressure in the liquid, produced1This test method is under the jurisdiction of ASTM Committee G02 on Wearand Erosion and is the direct responsibility of Subcommittee G02.10 on Erosion bySolids and Liquids.Current edition approved Feb. 1, 2016. Published March 2016. Originallyapproved

15、 in 1972. Last previous edition approved in 2010 as G32 10. DOI:10.1520/G0032-16.2For 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 to the standards Document Summary page

16、 onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1by 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

17、increase in liquidtemperature.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

18、collapse on or near thatsurface.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 cavita

19、tion or impingement as 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 thecontext, it is implied that the condition

20、s of cavitation orimpingement have remained the same throughout all exposureperiods, 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

21、slope of a linefrom 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 thesp

22、ecimen. This is the 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, u

23、sually obtained bynumerical 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.

24、9.1 DiscussionIn 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

25、“period” is recommended 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 o

26、f 1.0 m isthe least 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

27、an obstacle or through 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 deformatio

28、nand internal stresses 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

29、that exhibits such 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

30、 which persists for 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 surfac

31、e. (Also known as 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 the timeor exposure axis of the straight-line extension of the maximum-slope portion

32、 of the cumulative erosion-time curve; while thisis not a true measure of the incubation stage, it serves to locatethe maximum erosion rate line on the cumulative erosionversus time coordinates.3.1.16 normalized erosion resistance, Ne,na measure ofthe erosion resistance of a test material relative t

33、o that of aspecified 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

34、 the erosion ratetime 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 va

35、lue).”3.1.17 normalized 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 straig

36、ht linedrawn through the origin and tangent to the knee of theG32162cumulative 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.3.1.19 te

37、rminal erosion 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

38、fluctuations within 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 specimenbutto

39、n of proper mass 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

40、 andfrequency 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 inte

41、rpretation of 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

42、encountered, for instance, in pumps, hydraulic turbines, hy-draulic dynamometers, valves, bearings, diesel engine cylinderliners, ship propellers, hydrofoils, and in internal flow passageswith obstructions. An alternative method for similar purposesis Test Method G134, which employs a cavitating liq

43、uid jet toproduce erosion on a stationary specimen. The latter may bemore suitable 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 as

44、creening test for 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

45、This test method 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 liq

46、uid cavitation 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

47、 the “stationary 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 s

48、everalinvestigators 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 thread

49、ed specimen, as 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