1、Designation: G134 95 (Reapproved 2010)1Standard Test Method forErosion of Solid Materials by Cavitating Liquid Jet1This standard is issued under the fixed designation G134; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEUpdated Section 3 to reflect Terminology G4010b editorially in December 2010.1. Scope1.1 This test method covers a test tha
3、t can be used tocompare the cavitation erosion resistance of solid materials. Asubmerged cavitating jet, issuing from a nozzle, impinges on atest specimen placed in its path so that cavities collapse on it,thereby causing erosion. The test is carried out under specifiedconditions in a specified liqu
4、id, usually water. This test methodcan also be used to compare the cavitation erosion capability ofvarious liquids.1.2 This test method specifies the nozzle and nozzle holdershape and size, the specimen size and its method of mounting,and the minimum test chamber size. Procedures are describedfor se
5、lecting the standoff distance and one of several standardtest conditions. Deviation from some of these conditions ispermitted where appropriate and if properly documented.Guidance is given on setting up a suitable apparatus, test andreporting procedures, and the precautions to be taken. Standardrefe
6、rence materials are specified; these must be used to verifythe operation of the facility and to define the normalizederosion resistance of other materials.1.3 Two types of tests are encompassed, one using testliquids which can be run to waste, for example, tap water, andthe other using liquids which
7、 must be recirculated, for ex-ample, reagent water or various oils. Slightly different testcircuits are required for each type.1.4 This test method provides an alternative to Test MethodG32. In that method, cavitation is induced by vibrating asubmerged specimen at high frequency (20 kHz) with aspeci
8、fied amplitude. In the present method, cavitation isgenerated in a flowing system so that both the jet velocity andthe downstream pressure (which causes the bubble collapse)can be varied independently.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are
9、included in thisstandard.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 regulatory limitations pri
10、or to use.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 WireD1193 Specification for Reagent WaterE691 Practice for Conducting an Interlaboratory
11、 Study toDetermine the Precision of a Test MethodG32 Test Method for Cavitation Erosion Using VibratoryApparatusG40 Terminology Relating to Wear and ErosionG73 Test Method for Liquid Impingement Erosion UsingRotating Apparatus2.2 ASTM Adjuncts:Manufacturing Drawings of the Apparatus33. Terminology3.
12、1 See Terminology G40 for definitions of terms relating tocavitation erosion. For convenience, definitions of some im-portant terms used in this test method are reproduced below.3.2 Definitions:3.2.1 cavitation, nthe formation and subsequent collapse,within a liquid, of cavities or bubbles that cont
13、ain vapor or amixture of vapor and gas.3.2.1.1 DiscussionCavitation originates from a local de-crease in hydrostatic pressure in the liquid, usually producedby motion of the liquid (see flow cavitation) or of a solid1This test method is under the jurisdiction of ASTM Committee G02 on Wearand Erosion
14、 and is the direct responsibility of Subcommittee G02.10 on Erosion bySolids and Liquids.Current edition approved Dec. 1, 2010. Published December 2010. Originallyapproved in 1995. Last previous edition approved in 2006 as G13495(2006). DOI:10.1520/G0134-95R10E01.2For referenced ASTM standards, visi
15、t 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.3Available from ASTM International Headquarters. Order Adjunct No.ADJG0134.1Copyright ASTM Intern
16、ational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.boundary (see vibratory cavitation). It is distinguished in thisway from boiling, which originates from an increase in liquidtemperature.3.2.1.2 DiscussionThe term cavitation, by itself, shouldnot be used to
17、 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 thatsurface. G403.2.2 cavitation erosion, nprogressive loss of originalmaterial
18、from a solid surface due to continued exposure tocavitation. G403.2.3 cumulative erosion, nin cavitation and impingementerosion, the total amount of material lost from a solid surfaceduring all exposure periods since it was first exposed tocavitation or impingement as a newly-finished surface. (More
19、specific terms that may be used are cumulative mass loss,cumulative volume loss,orcumulative mean depth of erosion.See also cumulative erosion-time curve.)3.2.3.1 DiscussionUnless otherwise indicated by the con-text, it is implied that the conditions of cavitation or impinge-ment have remained the s
20、ame throughout all exposure periods,with no intermediate refinishing of the surface. G403.2.4 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 linefrom the origin to the specifi
21、ed point on the cumulativeerosion-time curve. ( Synonym: average erosion rate) G403.2.5 cumulative erosion-time curve, nin cavitation andimpingement erosion, a plot of cumulative erosion versuscumulative exposure duration, usually determined by periodicinterruption of the test and weighing of the sp
22、ecimen. This isthe primary record of an erosion test. Most other characteris-tics, such as the incubation period, maximum erosion rate,terminal erosion rate, and erosion rate-time curve, are derivedfrom it. G403.2.6 flow cavitation, ncavitation caused by a decrease inlocal pressure induced by change
23、s in velocity of a flowingliquid. Typically, this may be caused by flow around anobstacle or through a constriction, or relative to a blade or foil.A cavitation cloud or “cavitating wake” generally trails fromsome point adjacent to the obstacle or constriction to somedistance downstream, the bubbles
24、 being formed at one placeand collapsing at another. G403.2.7 incubation period, nin cavitation and impingementerosion, the initial stage of the erosion rate-time pattern duringwhich the erosion rate is zero or negligible compared to laterstages. Also, the exposure duration associated with this stag
25、e.(Quantitatively it is sometimes defined as the intercept on thetime or exposure axis, of a straight line extension of themaximum-slope portion of the cumulative erosion-time curve.)G403.2.8 maximum erosion rate, nin cavitation and liquidimpingement erosion, the maximum instantaneous erosion ratein
26、 a test that exhibits such a maximum followed by decreasingerosion rates. (See also erosion rate-time pattern.)3.2.8.1 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
27、 maximum which persists for sometime. G403.2.9 normalized erosion resistance, Ne, nin cavitationand liquid impingement erosion, a measure of the erosionresistance of a test material relative to that of a specifiedreference material, calculated by dividing the volume loss rateof the reference materia
28、l by that of the test material, when bothare similarly tested and similarly analyzed. By “similarlyanalyzed,” it is meant that the two erosion rates must bedetermined for corresponding portions of the erosion rate timepattern; for instance, the maximum erosion rate or the terminalerosion rate.3.2.9.
29、1 DiscussionArecommended complete wording hasthe form, “The normalized erosion resistance of (test material)relative to (reference material) based on (criterion of dataanalysis) is (numerical value).” G403.2.10 normalized incubation resistance, No, nthe nomi-nal incubation period of a test material,
30、 divided by the nominalincubation period of a specified reference material similarlytested and similarly analyzed. (See also normalized erosionresistance.) G403.2.11 terminal erosion rate, nin cavitation or liquidimpingement erosion, the final steady-state erosion rate that isreached (or appears to
31、be approached asymptotically) after theerosion rate has declined from its maximum value. (See alsoterminal period and erosion rate-time pattern.) G403.3 Definitions of Terms Specific to This Standard:3.3.1 cavitating jet, na continuous liquid jet (usuallysubmerged) in which cavitation is induced by
32、the nozzle designor sometimes by a center body. See also jet cavitation.3.3.2 cavitation number, sa dimensionless number thatmeasures the tendency for cavitation to occur in a flowingstream of liquid, and that, for the purpose of this test method,is defined by the following equation.All pressures ar
33、e absolute.s5pd2 pv!12rV2(1)where:pv= vapor pressure,pd= static pressure in the downstream chamber,V = jet velocity, andr = liquid density.3.3.2.1 For liquid flow through any orifice:12r V25 pu2 pd(2)where:pu= upstream pressure.3.3.2.2 For erosion testing by this test method, the cavitat-ing flow in
34、 the nozzle is choked, so that the downstreampressure, as seen by the flow, is equal to the vapor pressure.The cavitation number thus reduces to:s5pd2 pvpu2 pv(3)which for many liquids and at many temperatures can beapproximated by:G134 95 (2010)12s5pdpu(4)sincepupdpv(5)3.3.3 jet cavitation, nthe ca
35、vitation generated in thevortices which travel in sequence singly or in clouds in theshear layer around a submerged jet. It can be amplified by thenozzle design so that vortices form in the vena contracta regioninside the nozzle.3.3.4 stand-off distance, nin this test method, the distancebetween the
36、 inlet edge of the nozzle and the target face of thespecimen. It is thus defined because the location and shape ofthe inlet edge determine the location of the vena contracta andthe initiation of cavitation.3.3.5 tangent erosion rate, nthe slope of a straight linedrawn through the origin and tangent
37、to the knee of thecumulative erosion-time curve, when the shape of that curvehas the characteristic S-shape pattern that permits this. In suchcases, the tangent erosion rate also represents the maximumcumulative erosion rate exhibited during the test.3.3.6 vena contracta, nthe smallest locally occur
38、ringdiameter of the main flow of a fluid after it enters into a nozzleor orifice from a larger conduit or a reservoir. At this point themain or primary flow is detached from the solid boundaries,and vortices or recirculating secondary flow patterns areformed in the intervening space.4. Summary of Te
39、st Method4.1 This test method produces a submerged cavitating jetwhich impinges upon a stationary specimen, also submerged,causing cavitation bubbles to collapse on that specimen andthereby to erode it. This test method generally utilizes acommercially available positive displacement pump fitted wit
40、ha hydraulic accumulator to damp out pulsations. The pumpdelivers test liquid through a small sharp-entry cylindrical-borenozzle, which discharges a jet of liquid into a chamber at acontrolled pressure. Cavitation starts in the vena contractaregion of the jet within the length of the nozzle; it is s
41、tabilizedby the cylindrical bore and it emerges, appearing to the eye asa cloud which is visible around the submerged liquid jet. Abutton type specimen is placed in the path of the jet at aspecified stand-off distance from the entry edge of the nozzle.Cavitation bubbles collapse on the specimen, thu
42、s causingerosion. Both the upstream and the downstream chamberpressures and the temperature of the discharging liquid must becontrolled and monitored. The test specimen is weighedaccurately before testing begins and again during periodicinterruptions of the test, in order to obtain a history of mass
43、loss versus time (which is not linear). Appropriate interpreta-tion of the cumulative erosion-time curve derived from thesemeasurements permits comparisons to be drawn betweendifferent materials, different test conditions, or between differ-ent liquids. A typical test rig can be built using a 2.5-kW
44、 pumpcapable of producing 21-MPa pressure. The standard nozzlebore diameter is 0.4 mm, but this may be changed if requiredfor specialized tests.5. Significance and Use5.1 This test method may be used to estimate the relativeresistances of materials to cavitation erosion, as may beencountered for ins
45、tance in pumps, hydraulic turbines, valves,hydraulic dynamometers and couplings, bearings, diesel enginecylinder liners, ship propellers, hydrofoils, internal flow pas-sages, and various components of fluid power systems or fuelsystems of diesel engines. It can also be used to compareerosion produce
46、d by different liquids under the conditionssimulated by the test. Its general applications are similar tothose of Test Method G32.5.2 In this test method cavitation is generated in a flowingsystem. Both the velocity of flow which causes the formationof cavities and the chamber pressure in which they
47、 collapse canbe changed easily and independently, so it is possible to studythe effects of various parameters separately. Cavitation condi-tions can be controlled easily and precisely. Furthermore, iftests are performed at constant cavitation number (s), it ispossible, by suitably altering the press
48、ures, to accelerate orslow down the testing process (see 11.2 and Fig. A2.2).5.3 This test method with standard conditions should not beused to rank materials for applications where electrochemicalcorrosion or solid particle impingement plays a major role.However, it could be adapted to evaluate ero
49、sion-corrosioneffects if the appropriate liquid and cavitation number, for theservice conditions of interest, are used (see 11.1).5.4 For metallic materials, this test method could also beused as a screening test for applications subjected to high-speed liquid drop impingement, if the use of Practice G73 isnot feasible. However, this is not recommended for elastomericcoatings, composites, or other nonmetallic aerospace materials.5.5 The mechanisms of cavitation erosion and liquid im-pingement erosion are not fully understood and may vary,depending on the d
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