ASTM G32-2006 Standard Test Method for Cavitation Erosion Using Vibratory Apparatus《使用振动装置对气泡浸蚀的标准试验方法》.pdf

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1、Designation: G 32 06Standard Test Method forCavitation Erosion Using Vibratory Apparatus1This standard is issued under the fixed designation G 32; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision.Anumber in

2、 parentheses indicates the year of last reapproval.Asuperscriptepsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method produces cavitation damage on the faceof a specimen vibrated at high frequency while immersed in aliquid. The vibration induces

3、the formation and collapse ofcavities in the liquid, and the collapsing cavities produce thedamage to and erosion (material loss) of the specimen.1.2 Although the mechanism for generating fluid cavitationin this method differs from that occurring in flowing systemsand hydraulic machines (see 5.1), t

4、he 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 of damage in

5、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 container. Itpermits

6、 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 be used toverif

7、y the operation of the facility and to define the normalizederosion resistance of other test materials.1.4 The values stated in SI units are to be regarded asstandard. The inch-pound units given in parentheses are forinformation only.1.5 This standard does not purport to address all of thesafety con

8、cerns, 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 regulatory limitations prior to use. For specific safetyprecautionary information, see 6.1, 10.3, and 10.6.1.2. Refer

9、enced Documents2.1 ASTM Standards:2A 276 Specification for Stainless Steel Bars and ShapesB 160 Specification for Nickel Rod and BarB211 Specification for Aluminum and Aluminum-AlloyBar, Rod, and WireD 1193 Specification for Reagent WaterE 177 Practice for Use of the Terms Precision and Bias inASTM

10、Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 960 Specification for Laboratory Glass BeakersG40 Terminology Relating to Wear and ErosionG73 Practice for Liquid Impingement Erosion TestingG117 Guide for Calculating and Reporting Measure

11、s ofPrecision Using Data from Interlaboratory Wear or Ero-sion TestsG 134 Test Method for Erosion of Solid Materials by aCavitating Liquid Jet3. Terminology3.1 Definitions:3.1.1 See Terminology G40for definitions of terms relatingto cavitation erosion. For convenience, important definitionsfor this

12、standard are listed below; some are slightly modifiedfrom Terminology G40or not contained therein.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 amixt

13、ure of vapor and gas.3.1.3.1 DiscussionIn general, cavitation originates from alocal decrease in hydrostatic pressure 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 f

14、rom an increase in liquidtemperature.1This 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 Dec. 1, 2006. Published January 2007. Originallyapproved in 1972.

15、 Last previous edition approved in 2003 as G 3203.2For 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 onthe ASTM website.1Copyright

16、ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United 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

17、 or cavitation erosion. To erode a solidsurface, bubbles or cavities must 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 sol

18、id surface during all exposure periods since itwas first exposed to cavitation 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 Discussion

19、Unless otherwise indicated by the con-text, it is implied that the conditions of cavitation or 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

20、test divided by the correspond-ing cumulative exposure duration; that is, the 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,

21、usually deter-mined by periodic interruption of the test and weighing of thespecimen. 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 rat

22、e-time curve, na plot of instantaneouserosion rate versus exposure duration, usually 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

23、rate-time curve in terms of theseveral stages of which it may be composed.3.1.9.1 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

24、period,terminal period, and occasionally catastrophic period. Thegeneric term “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

25、 a mean depth of erosion of 1.0 m.3.1.10.1 DiscussionA mean depth of erosion of 1.0 m isthe least accurately measurable value considering the precisionof the scale, specimen diameter, and density of the standardreference material.3.1.11 incubation period, nthe initial stage of the erosionrate-time p

26、attern during which the erosion rate is zero ornegligible compared to later stages.3.1.11.1 DiscussionThe incubation period is usuallythought to represent the accumulation of plastic deformationand internal stresses under the surface, that precedes significantmaterial loss. There is no exact measure

27、 of the duration of theincubation period. See related terms, erosion threshold timeand nominal incubation period.3.1.12 maximum erosion rate, nthe maximum instanta-neous erosion rate in a test that exhibits such a maximumfollowed by decreasing erosion rates. (See also erosion rate-time pattern.)3.1.

28、12.1 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 for sometime.3.1.13 mean depth of erosion (MDE), nthe average thick-ness of material eroded

29、 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 mean depth ofpenetration or MDP. Since that might be taken to denote theaverage value of

30、the depths of individual pits, it is a lesspreferred term.)3.1.14 nominal incubation time, nthe intercept on thetime or exposure axis of the straight-line extension of themaximum-slope portion of the cumulative erosion-time curve;while this is not a true measure of the incubation stage, itserves to

31、locate the maximum erosion rate line on the cumu-lative erosion versus time coordinates.3.1.15 normalized erosion resistance, Ne, na measure ofthe erosion resistance of a test material relative to that of aspecified reference material, calculated by dividing the volumeloss rate of the reference mate

32、rial 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 ratetime pattern; for instance, the maximum erosion rate or theterminal erosion rate.3.1.15.

33、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).”3.1.16 normalized incubation resistance No, nthe nominalincubation time of a test material, divided

34、 by the nominalincubation time of a specified reference material similarlytested and similarly analyzed. (See also normalized erosionresistance.)3.1.17 tangent erosion rate, nthe slope of a straight linedrawn through the origin and tangent to the knee of thecumulative erosion-time curve, when that c

35、urve 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.3.1.18 terminal erosion rate, nthe final steady-state ero-sion rate that is reached (or appears to be approached asymp-

36、totically) after the erosion rate has declined from its maximumvalue. (See also terminal period and erosion rate-time pattern.)3.1.19 vibratory cavitation, ncavitation caused by thepressure fluctuations within a liquid, induced by the vibrationof a solid surface immersed in the liquid.G320624. Summa

37、ry 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 mass is attached by threading into the tip ofthe horn.4.2 The specimen is immersed into a co

38、ntainer 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 of vibration of the test specimen must be accuratelycontrolled and monitored.4.3 The test

39、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 this cumulative erosion-versus-time curve permits comparison of results betweendifferent m

40、aterials 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, for instance, in pumps, hydraulic turbines, hydraulicdynamometers, valves, bearings, dies

41、el engine cylinder liners,ship propellers, hydrofoils, and in internal flow passages withobstructions.An alternative method for similar purposes is TestMethod G 134, which employs a cavitating liquid jet toproduce erosion on a stationary specimen. The latter may bemore suitable for materials not rea

42、dily 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 for materials subjected to liquid impingementerosion as encountered, for instance, in low-

43、pressure steamturbines and in aircraft, missiles or spacecraft flying throughrainstorms. Practice G73describes another testing approachspecifically intended for that type of environment.5.3 This test method is not recommended for evaluatingelastomeric or compliant coatings, some of which have beensu

44、ccessfully 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 induced by its vibratory motion. Theresult would not be representative of a field application,

45、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 “stationary speci-men” method. In that method, the specimen is fixed within the liquidcontainer, and the

46、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 severalinvestigators have used this approach (see X3.2.3), they have differed withregard to standoff distances

47、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 required for this test method (see 7.6).5.4 This test method should not be directly used to ra

48、nkmaterials 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, X3.2).5.5 Those who are engaged in basic research, or concernedwith very specialized applica

49、tions, may need to vary some ofthe test parameters to suit their purposes. However, adherenceto this test method in all other respects will permit a betterunderstanding and correlation between the results of differentinvestigators.5.6 Because of the nonlinear nature of the erosion-versus-time curve in cavitation and liquid impingement erosion, theshape of that curve must be considered in making comparisonsand drawing conclusions. See Section 11.5.7 The results of this test may be significantly affected bythe specimens surface preparation. This must be co