1、Designation: C 1525 04Standard Test Method forDetermination of Thermal Shock Resistance for AdvancedCeramics by Water Quenching1This standard is issued under the fixed designation C 1525; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, the year 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 describes the determination of theresistance of advanced ceramics to thermal shock
3、by waterquenching. The method builds on the experimental principle ofrapid quenching of a test specimen at an elevated temperaturein a water bath at room temperature. The effect of the thermalshock is assessed by measuring the reduction in flexuralstrength produced by rapid quenching of test specime
4、ns heatedacross a range of temperatures. For a quantitative measurementof thermal shock resistance, a critical temperature interval isdetermined by a reduction in the mean flexural strength of atleast 30 %. The test method does not determine thermalstresses developed as a result of a steady state te
5、mperaturedifferences within a ceramic body or of thermal expansionmismatch between joined bodies. The test method is notintended to determine the resistance of a ceramic material torepeated shocks. Since the determination of the thermal shockresistance is performed by evaluating retained strength, t
6、hemethod is not suitable for ceramic components; however, testspecimens cut from components may be used.1.2 The test method is intended primarily for dense mono-lithic ceramics, but may also be applicable to certain compos-ites such as whisker- or particulate-reinforced ceramic matrixcomposites that
7、 are macroscopically homogeneous.1.3 Values expressed in this standard test method are inaccordance with the International System of Units (SI) andStandard IEEE/ASTM SI 10.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibilit
8、y 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:2C 373 Water Absorption, Bulk Density, Apparent Porosity,and Apparent Specific Gravity of Fired White
9、ware Prod-uctsC 1145 Terminology of Advanced CeramicsC 1161 Test Method for Flexural Strength of AdvancedCeramics at Ambient TemperatureC 1239 Practice for Reporting Uniaxial Strength Data andEstimating Weibull Parameters for Advanced CeramicsC 1322 Practice for Fractography and Characterization ofF
10、racture Origins in Advanced CeramicsE 4 Practice for Force Verification of Testing MachinesE 6 Terminology Relating to Methods of Mechanical Test-ingE 616 Terminology Relating to Fracture TestingIEEE/ASTM SI 10 Standard for Use of the InternationalSystem of Units (SI): The Modern Metric System2.2 Eu
11、ropean Standard:EN 820-3 Advanced Technical CeramicsMonolithicCeramicsThermomechanical PropertiesPart 3: Deter-mination of Resistance to Thermal Shock by WaterQuenching33. Terminology3.1 DefinitionsThe terms described in TerminologiesC 1145, E 6, and E 616 are applicable to this standard testmethod.
12、 Specific terms relevant to this test method are asfollows:3.1.1 advanced ceramic, na highly engineered, high per-formance, predominately non-metallic, inorganic, ceramic ma-terial having specific functional attributes. C 11451This test method is under the jurisdiction of ASTM Committee C28 onAdvanc
13、ed Ceramics and is the direct responsibility of Subcommittee C28.01 onProperties and Performance.Current edition approved May 1, 2004. Published June 2004. Originallyapproved in 2002. Last previous edition approved in 2003 as C 1525 - 03.2For referenced ASTM standards, visit the ASTM website, www.as
14、tm.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 CEN, 36, rue de Stassart, B-1050 Brussels, Belgium, ww-w.cenorm.be.1Copyright ASTM International, 100 Barr
15、Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.2 critical temperature difference, DTc, ntemperaturedifference between the furnace and the ambient temperaturewater bath that will cause a 30 % drop in the average flexuralstrength.3.1.3 flexural strength, sf, na measure
16、of the ultimatestrength of a specified beam specimen in bending determined ata given stress rate in a particular environment.3.1.4 fracture toughness, na generic term for measures ofresistance to extension of a crack. E 6163.1.5 slow crack growth (SCG), nsubcritical crack growth(extension) which may
17、 result from, but is not restricted to, suchmechanisms as environmentally-assisted stress corrosion ordiffusive crack growth.3.1.6 thermal shock, na large and rapid temperaturechange, resulting in large temperature differences within oracross a body. C 11453.1.7 thermal shock resistance, nthe capabi
18、lity of materialto retain its mechanical properties after exposure to one ormore thermal shocks.4. Summary of Test Method4.1 This test method indicates the ability of an advancedceramic product to withstand the stress generated by suddenchanges in temperature (thermal shock). The thermal shockresist
19、ance is measured by determining the loss of strength (ascompared to as-received specimens) for ceramic test specimensquickly cooled after a thermal exposure. A series of rectangularor cylindrical test specimen sets are heated across a range ofdifferent temperatures and then quenched rapidly in a wat
20、erbath. After quenching, the test specimens are tested in flexure,and the average retained flexural strength is determined foreach set of specimens quenched from a given temperature. The“critical temperature difference” for thermal shock is estab-lished from the temperature difference (exposure temp
21、eratureminus the water quench temperature) that produces a 30 %reduction in flexural strength compared to the average flexuralstrength of the as-received test specimens.5. Significance and Use5.1 The high temperature capabilities of advanced ceramicsare a key performance benefit for many demanding e
22、ngineeringapplications. In many of those applications, advanced ceramicswill have to perform across a broad temperature range withexposure to sudden changes in temperature and heat flux.Thermal shock resistance of the ceramic material is a criticalfactor in determining the durability of the componen
23、t undertransient thermal conditions.5.2 This test method is useful for material development,quality assurance, characterization, and assessment of durabil-ity. It has limited value for design data generation, because ofthe limitations of the flexural test geometry in determiningfundamental tensile p
24、roperties.5.3 Appendix X1 (following EN 820-3) provides an intro-duction to thermal stresses, thermal shock, and criticalmaterial/geometry factors. The appendix also contains a math-ematical analysis of the stresses developed by thermal expan-sion under steady state and transient conditions, as dete
25、rminedby mechanical properties, thermal characteristics, and heattransfer effects.6. Interferences6.1 Time-dependent phenomena such as stress corrosion orslow crack growth may influence the strength tests. This mightespecially be a problem if the test specimens are not properlydried before strength
26、testing.6.2 Surface preparation of test specimens can introducemachining flaws which may have a pronounced effect on themeasured flexural strength. The surface preparation may alsoinfluence the cracking process due to the thermal shockprocedure. It is especially important to consider surface con-dit
27、ions in comparing test specimens and components.6.3 The results are given in terms of a temperature differ-ence between furnace and quenching bath (DT). However, it isimportant to notice that results may be different for the sameDT but different absolute temperatures. It is therefore specifiedin thi
28、s test method to quench to room temperature.6.4 The formulae presented in this test method apply strictlyonly to materials that do not exhibit R-curve behavior, but havea single-valued fracture toughness. If the test material exhibitsa strong R-curve behavior, i.e., increase in fracture toughnesswit
29、h increasing crack length, caution must be taken in inter-preting the results.6.5 Test data for specimens of different geometries are notdirectly comparable because of the effect of geometry on heattransfer and stress gradients. Quantitative comparisons ofthermal shock resistance for different ceram
30、ic compositionsshould be done with equivalent test specimen geometries.7. Apparatus7.1 Test Apparatus:7.1.1 The test method requires a thermal exposure/quenching system (consisting of a furnace, specimen handlingequipment, and a quench bath) and a testing apparatus suitablefor measuring the flexural
31、 strength of the test specimens.7.1.2 The test method requires a furnace capable of heatingand maintaining a set of test specimens at the requiredtemperature to 6 5K(6 5C). The temperature shall bemeasured with suitable thermocouples located no more than 2mm from the midpoint of the specimen(s) in t
32、he furnace.Furnaces will usually have an open atmosphere, because airexposure is common during the transfer to the quench bath.NOTE 1If air exposure is detrimental, a special furnace-quenchsystem can be set up in which both the furnace and the quench unit arecontained within an inert atmosphere cont
33、ainer. A common design forsuch a system consists of a tube furnace positioned vertically above thequench tank, so that the test specimen drops directly into the tank from thefurnace.7.1.3 The method requires a test specimen handling equip-ment designed so that the test specimen can be transferred fr
34、omthe furnace to the quenching bath within 5 s.7.1.4 A water bath controlled to 293 6 2 K (20C 6 2C)is required. The water bath must have sufficient volume toprevent the temperature in the bath from rising more than 5 K(5C) after test specimen quenching. It is recommended thatthe bath be large enoug
35、h for the test specimens to have cooledsufficiently before reaching the bottom of the bath, or containa screen near the bottom to prevent the test specimens fromresting directly on the bottom of the bath.C15250427.1.5 The universal test machine used for strength testing inthis test method shall conf
36、orm to the requirements of PracticeE 4. Specimens may be loaded in any suitable test machineprovided that uniform test rates, either using load-controlled ordisplacement-controlled mode, can be maintained. The loadsused in determining flexural strength shall be accurate within6 1.0 % at any load wit
37、hin the selected load rate and loadrange of the test machine as defined in Practice E 4.7.1.6 The configuration and mechanical properties of thetest fixtures shall be in accordance with Test Method C 1161for use with the standard four-point flexure specimens. If largertest pieces (sizes A or C below
38、) are employed, the test fixtureshall be scaled accordingly. There are currently no standardfixtures for testing cylindrical rods in flexure; however, thefixtures to be used shall have the appropriate articulation. Testfixtures without appropriate articulation shall not be permitted;the articulation
39、 of the fixture shall meet the requirementsspecified in Test Method C 1161.7.1.7 The method requires a 393 K (120C) drying oven toremove moisture from test specimens before (if needed) andafter quench testing.7.1.8 A micrometer with a resolution of 0.002 mm (or0.0001 in.) or smaller should be used t
40、o measure the test piecedimensions. The micrometer shall have flat anvil faces. Themicrometer shall not have a ball tip or sharp tip since thesemight damage the test piece if the specimen dimensions aremeasured prior to fracture. Alternative dimension measuringinstruments may be used provided that t
41、hey have a resolutionof 0.002 mm (or 0.0001 in.) or finer and do no harm to thespecimen.8. Test Specimens8.1 The ceramic test specimens shall be pieces specificallyprepared for this purpose from bulk material or cut fromcomponents.8.1.1 Specimen SizeThree specimen geometries are de-fined for use in
42、this test method:8.1.1.1 Type ARods 10 6 0.13 mm in diameter, 120 mmlong.8.1.1.2 Type BBars 3 6 0.13 mm 3 4 6 0.13 mm in crosssection, minimum 45 mm long with chamfered edges, inaccordance with type B in Test Method C 1161.8.1.1.3 Type CBars 10 6 0.13 mm 3 10 6 0.13 mm incross section, 120 mm long,
43、with chamfered edges.NOTE 2The test specimens of A and C type are intended to be largeenough to produce a materials ranking that is basically independent ofspecimen size and appropriate for larger test specimens (1,2). Testspecimens of B type may require greater quenching temperature differ-ences in
44、 order to produce strength reduction. These test specimens maynot correctly rank the relative behavior of larger components. Only TypeB coincides with Type B in Test Method C 1161.NOTE 3Under some circumstances the edges of prismatic test speci-mens or the ends of cylindrical test specimens may be d
45、amaged byspallation during the quench test. These specimens should be discardedfrom the batch used for strength testing if the damage will interfere withthe strength test. In any case such spallation must be noted in the report.Spallation problems can be alleviated by chamfering sharp edges.NOTE 4Th
46、e parallelism tolerances on the four longitudinal faces are0.015 mm for B and C and the cylindricity for A is 0.015 mm.8.2 Test Specimen PreparationDepending on the intendedapplication of the thermal shock data, one of the four testspecimen preparation methods described in Test MethodC 1161 may be u
47、sed: As-Fabricated, Application-MatchedMachining, Customary Procedures, or Standard Procedures.8.3 Handling PrecautionsCare shall be exercised in stor-ing and handling of test specimens to avoid the introduction ofrandom and severe flaws, such as might occur if test specimenswere allowed to impact o
48、r scratch each other.8.4 Number of Test SpecimensA minimum of 10 speci-mens shall be used to determine as-received strength at roomtemperature. A minimum of 30 is required if estimates regard-ing the form of the strength distribution is to be determined (forexample a Weibull modulus). A minimum of 5
49、 specimens shallbe used at each thermal shock temperature. It is recommendedthat as DTcis established, additional 5 specimens be tested atthis as well as the adjacent temperature intervals. This willallow for determination of the mean and standard deviation. Ifestimates regarding the form of the strength distribution at theDTcand adjoining temperature intervals are desired (forexample, Weibull analysis) additional specimens must betested at these temperature intervals. See Practice C 1239 forguidance on estimating Weibull parameters.9. Procedure9.1 Test Exposu
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