1、Designation: G 134 95 (Reapproved 2006)Standard Test Method forErosion of Solid Materials by a Cavitating Liquid Jet1This standard is issued under the fixed designation G 134; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a test that can be used tocompare the cavitation erosion resistance of solid materials.
3、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 liquid, usually water. This test methodcan also be used to compare the cavitation
4、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 selecting the standoff distance and one of several standardtest conditions. Devi
5、ation 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. Standardreference materials are specified; these must be used to verifythe operation of th
6、e 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 must be recirculated, for ex-ample, reagent water or various oils. Slightly d
7、ifferent 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 aspecified amplitude. In the present method, cavitation isgenerated in a flowing sys
8、tem 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 as thestandard. The values given in parentheses are for informationonly.1.6 This standard does not purport to address all of
9、 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 prior to use.2. Referenced Documents2.1 ASTM Standards:2A 276 Specification for
10、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 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodG32 Test Method for Cavi
11、tation Erosion Using VibratoryApparatusG40 Terminology Relating to Wear and ErosionG73 Practice for Liquid Impingement Erosion Testing2.2 ASTM Adjuncts:Manufacturing Drawings of the Apparatus33. Terminology3.1 DefinitionsSee Terminology G40 for definitions ofterms relating to cavitation erosion. For
12、 convenience, defini-tions of some important terms used in this test method arequoted below from Terminology G40 90a.3.1.1 cavitationthe formation and collapse, within a liq-uid, of cavities or bubbles that contain vapor or gas, or both.3.1.1.1 DiscussionIn general, cavitation originates from adecre
13、ase in static pressure in the liquid. It is distinguished inthis way from boiling, which originates from an increase inliquid temperature. There are certain situations where it may bedifficult to make a clear distinction between cavitation andboiling, and the more general definition that is given he
14、re is,therefore, preferred.3.1.1.2 DiscussionIn order to erode a solid surface bycavitation, it is necessary for the cavitation bubbles to collapseon or close to that surface.1This test method is under the jurisdiction of ASTM Committee G02 on Wearand Erosion and is the direct responsibility of Subc
15、ommittee G02.10 on Erosion bySolids and Liquids.Current edition approved Dec. 1, 2006. Published January 2007. Originallyapproved in 1995. Last previous edition approved in 2001 as G 134 95 (2001)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service
16、 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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, P
17、A 19428-2959, United States.3.1.2 cavitation erosionprogressive loss of original mate-rial from a solid surface due to continued exposure to cavita-tion.3.1.3 cumulative erosionthe total amount of material lostfrom a solid surface during all exposure periods since it wasfirst exposed to cavitation o
18、r impingement as a newly finishedsurface. Unless otherwise indicated by the context, it is impliedthat the conditions of cavitation or impingement have remainedthe same throughout all exposure periods, with no intermediaterefinishing of the surface.3.1.4 cumulative erosion ratethe cumulative erosion
19、 di-vided by the corresponding cumulative exposure duration, thatis, the slope of a line from the origin to a specified point on thecumulative erosion-time curve.3.1.5 cumulative erosion-time curvea plot of cumulativeerosion versus cumulative exposure time, usually determinedby periodic interruption
20、 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 ratetime curve,are derived from it.3.1.6 flow cavitationcavitation caused by a decrease instatic
21、pressure induced by changes 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 somedistan
22、ce downstream, the bubbles being formed at one placeand collapsing at another.3.1.7 incubation periodin 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 associ
23、ated with this stage.(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).3.1.8 maximum erosion ratethe maximum instantaneouserosion rate in a test that exhibits such a max
24、imum followed bydecreasing erosion rates. (Occurrence 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.)3.1.9 normalized erosion resistance, Nethe volume
25、 lossrate of a test material, divided into the rate of volume loss of aspecified reference material similarly tested and similarlyanalyzed. Similarly analyzed means that the two erosion ratesmust be determined for corresponding portions of the erosionrate-time pattern; for instance, the maximum eros
26、ion rate or theterminal erosion rate.3.1.9.1 DiscussionArecommended complete wording hasthe form, “The normalized erosion resistance of (test material)relative to (reference material) based on (criterion of dataanalysis) is (numerical value).”3.1.10 normalized incubation resistance, Nothe incuba-tio
27、n period of a test material, divided by the incubation periodof a specified reference material similarly tested and similarlyanalyzed.3.1.11 terminal erosion ratethe final steady-state erosionrate that is reached (or appears to be approached asymptoti-cally) after the erosion rate has declined from
28、its maximumvalue. This occurs in some, but not all, cavitation and liquidimpingement tests.3.2 Definitions of Terms Specific to This Standard:3.2.1 cavitating jeta continuous liquid jet (usually sub-merged) in which cavitation is induced by the nozzle design orsometimes by a center body. See also je
29、t cavitation.3.2.2 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 are absolute.s5pd2 pv!12rV2(1)where:pv= vapor pressure,pd= st
30、atic pressure in the downstream chamber,V = jet velocity, andr = liquid density.3.2.2.1 For liquid flow through any orifice12r V25 pu2 pd. (2)where:pu= upstream pressure.3.2.2.2 For erosion testing by this test method, the cavitat-ing flow in the nozzle is choked, so that the downstreampressure, as
31、seen by the flow, is equal to the vapor pressure.The cavitation number thus reduces tos5pd2 pvpu2 pv(3)which for many liquids and at many temperatures can beapproximated by:s5pdpu(4)sincepupdpv(5)3.2.3 jet cavitationthe cavitation generated in the vorticeswhich travel in sequence singly or in clouds
32、 in the shear layeraround a submerged jet. It can be amplified by the nozzledesign so that vortices form in the vena contracta region insidethe nozzle.3.2.4 stand-off distancein this test method, the distancebetween the inlet edge of the nozzle and the target face of thespecimen. It is thus defined
33、because the location and shape ofthe inlet edge determine the location of the vena contracta andthe initiation of cavitation.3.2.5 tangent erosion ratethe slope of a straight linedrawn through the origin and tangent to the knee of thecumulative erosion-time curve, when the shape of that curvehas the
34、 characteristic S-shape pattern that permits this. In suchcases, the tangent erosion rate also represents the maximumcumulative erosion rate exhibited during the test.G 134 95 (2006)23.2.6 vena contractathe smallest locally occurring diam-eter of the main flow of a fluid after it enters into a nozzl
35、e ororifice 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 Test Method4.1 This test method produces a submerged cavitating jetwhic
36、h 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 witha hydraulic accumulator to damp out pulsations. The pumpdelivers tes
37、t 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 stabilizedby the cylindrical bore and it emerges, appearing to the eye
38、 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, thus causingerosion. Both the upstream and the downstream chamberpressur
39、es 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 massloss versus time (which is not linear). Appropriate interpreta-tion o
40、f 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 pumpcapable of producing 21-MPa pressure. The standard nozzlebore di
41、ameter 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 instance in pumps, hydraulic turbines, valves,hydraulic dynamometers and
42、 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 produced by different liquids under the conditionssimulated by the test. Its
43、 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 collapse canbe changed easily and independently, so it is possible t
44、o 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 pressures, to accelerate orslow down the testing process (see 11.2 and Fig
45、. 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 erosion-corrosioneffects if the appropriate liquid and cavitation number
46、, 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 highspeedliquid drop impingement, if the use of Practice G73is notfeasible. However, this is not recommended for elastomericco
47、atings, 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 detailed nature, scale, and intensity of theliquid/solid interactions. Erosion resistance may, therefore,arise
48、from a mix of properties rather than a single property, andhas not yet been successfully correlated with other indepen-dently measurable material properties. For this reason, theconsistency of results between different test methods (forexample, vibratory, rotating disk, or cavitating jet) or underdi
49、fferent experimental conditions is not very good. Smalldifferences between two materials are probably not significant,and their relative ranking could well be reversed in anothertest.5.6 Because of the nonlinear nature of the erosion-timecurve in cavitation erosion, the shape of that curve must beconsidered in making comparisons and drawing conclusions.Simply comparing the cumulative mass loss at the samecumulative test time for all materials will not give a reliablecomparison.6. Apparatus6.1 General Arrangement:6.1.1 Fig. 1 shows an arrangement of the test cha
