# ASTM C674-13

Designation: C674 − 13Standard Test Methods forFlexural Properties of Ceramic Whiteware Materials1This standard is issued under the fixed designation C674; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover determination of the modulusof rupture and the modulus of elasticity of fired ceramicwhitewares bodies, formed by any fabrication method, and areapplicable to both glazed and unglazed test specimens.1.2 The values stated in inch-pound units are to be regardedas the standard. The metric equivalents of inch-pound unitsmay be approximate.1.3 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 prior to use.2. Summary of Test Methods2.1 The specimens, either cylindrical, or rectangular, aresupported on knife edges over a suitable span and a direct loadis applied at the midpoint between the supports at a uniformrate until breakage occurs. The modulus of elasticity may bedetermined by halting the applied load at definite intervals andmeasuring the deflection of the specimen at the midpoint to thenearest 0.001 in. (0.025 mm).3. Significance and Use3.1 These test methods provide a means for determining themodulus of rupture and the modulus of elasticity, which maybe required in product specifications.4. Apparatus4.1 Testing Machine—Any suitable testing machine may beused, provided uniform rates of direct loading can be main-tained.4.1.1 For all specimens the loading rate should be such thatthe specimen should fail in approximately 1 min. Table 1 listsloading rates that shall be used for each size specimen. Forstrengths of specimens intermediate of those specified, inter-polation can be used to obtain the equivalent loading rate.4.1.2 For the prescribed rectangular specimens the loadingrate shall be 1000 6 150 lbs (454 6 68 kg)/min.4.2 Bearing Edges—For the support of the test specimen,two steel (or high-strength ceramic) knife edges rounded to aradius of 0.125 in. (3.18 mm) shall be provided. The load shallbe applied by means of a third steel knife edge rounded to aradius of 0.125 in. When testing rectangular specimens, thesupporting members for the bearing edges shall be constructedto provide a means for alignment of the bearing surfaces withthe surfaces of the test specimen (it being possible that therectangular specimen may be wedge-shaped or twisted). Theapparatus shown in Figs. 1 and 2 are suggested as suitabledevices for ensuring proper spacing and alignment of thebearing edges for rectangular test specimens.5. Test Specimens5.1 Preparation of Specimens—Form, fire, and finish thespecimens by the appropriate methods, following practicesused in actual production.5.2 Dimensions—The specimens shall be approximately1.125 in. (28.6 mm), 0.750 in. (19.2 mm), 0.500 in. (12.7 mm),or 0.250 in. (6.4 mm) in diameter, whichever diameter is mostcomparable to that of the finished product. The length shall be6 6 0.50 in. (153 6 12.7 mm) to permit an overhang of at least0.25 in. (6.4 mm) at each end when mounted on the supports.Note that the 0.25-in. specimens may be 3.75 6 0.25 in. (95 67 mm) long.5.2.1 The dry-pressed specimens shall be rectangular barsapproximately 1 in. (25.4 mm) by 0.50 in. (12.7 mm) in crosssection and at least 4.50 in. (114 mm) in length to permit anoverhang of at least 0.25 in. at each end when mounted on thesupports.5.3 Handling—Observe all due precautions in the forming,drying, and firing to produce straight test specimens of uniformcross section.5.4 Storage—Cool test specimens taken warm from the kilnin a desiccator. If the testing must be delayed, store the bars inthe desiccator, or in an electric oven at 110°C, and then cool ina desiccator before testing. When removing specimens from ahot kiln, take care to avoid thermal shock which will lead toerroneous results.1These test methods are under the jurisdiction of ASTM Committee C21 onCeramic Whitewares and Related Productsand are the direct responsibility ofSubcommittee C21.03 on Methods for Whitewares and Environmental Concerns.Current edition approved March 1, 2013. Published March 2013. Originallyapproved in 1971. Last previous edition approved in 2006 as C674 – 88 (2006).DOI: 10.1520/C0674-13.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1MODULUS OF RUPTURE6. Procedure6.1 Test at least ten dry specimens at room temperature.NOTE 1—The modulus of elasticity may be determined as described inSections 10–11on the same type specimens used for the modulus ofrupture test.6.2 Place the cylindrical specimen on the bearing edges,spaced 5 in. (127 mm) 6 2 % between centers, with thespecimen overhanging each end by at least 0.25 in. (6.4 mm).Apply the load at a right angle to the specimen and midway(62 %) between the supporting edges. Apply the load uni-formly at the appropriate rate for the specimen size (see 4.1.1)until failure occurs. Measure the diameter at four approxi-mately equidistant points at the break and take the average tothe nearest 0.001 in. (0.0254 mm) for calculation purposes.Break the 0.25-in. diameter rods between 3-in. (76-mm)centers and note this in the report.6.2.1 Place the rectangular test specimen on the bearingedges, spaced 4.0 in. (102 mm) between centers, with thespecimen overhanging at each end by at least 0.25 in. (6.4mm). Apply the load at a right angle to the 1-in. (25.4-mm)TABLE 1 Loading Rates for SpecimensSpecimen Size, in. (mm)Span, in. (mm)Nominal MOR, ksi (MPa)10 (69) 30 (207) 50 (345)Loading Rate, lb/min (kg/s)1.125 (28.6) diameter 5 (127) 1100 (8.32) 3400 (25.70) 5600 (42.34)0.750 (19.2) “ 5 (127) 300 (2.27) 1000 (7.56) 1700 (12.85)0.500 (12.7) “ 5 (127) 100 (0.76) 300 (2.27) 500 (3.76)0.250 (6.4) “ 3 (76) 20 (0.15) 60 (0.45) 100 (0.76)1 by 0.50 (25.4 by 12.7) 4 (102) 400 (3.02) 1250 (9.45) 2100 (15.88)FIG. 1 Suggested Bearing Edge and Specimen SupportFIG. 2 Alternative Suggested Bearing Edge and Specimen SupportC674 − 132surface of the specimen and midway between the supportingedges. Break specimens glazed on only one of the 1-in.surfaces with the glazed surface either up or down, but breakall of the specimens from any one lot in the same position andrecord this position. Apply the load uniformly at the rate of1000 6 150 lbs (454 6 68 kg)/min, until failure occurs.Measure the width and thickness at the break to the nearest0.001 in. (0.0254 mm).7. Calculation7.1 Calculate the modulus of rupture of each circular crosssection specimen as follows:M 5 8PL/πd3(1)where:M = modulus of rupture, psi (or MPa);P = load at rupture, lbf (or N);L = distance between supports, in. (or mm);d = diameter of specimen, in. (or mm).7.1.1 Calculate the modulus of rupture of each rectangularspecimen as follows:M 5 3 PL/2bd2where:M = modulus of rupture, psi (or MPa);P = load at rupture, lbf (or N);L = distance between supports, in. (or mm);b = width of specimen, in. (or mm); andd = thickness of specimen, in. (or mm).8. Report8.1 Report the following information:8.1.1 Identification of the material tested,8.1.2 Data and computed modulus of rupture for eachspecimen,8.1.3 The adjusted average of the computed modulus ofrupture values (discarding those values from the bars which,upon inspection, show obvious defect), and8.1.4 In the case of glazed specimens, the position of theglazed surface or surfaces, with respect to the applied load.8.2 The report may also include:8.2.1 A description of type of fracture and the behavior ofeach specimen under load,8.2.2 Name and rating of the machine used to make the test,and8.2.3 A graph showing the individual values of modulus ofrupture arranged in ascending order.9. Precision and Bias9.1 Precision:9.1.1 Interlaboratory Test Data—An interlaboratory testwas run in 1978 in which randomly drawn samples of fivematerials were tested in each of four laboratories. One operatorin each laboratory tested ten specimens of each material. Thecomponents of variance for flexural strength results expressedas coefficients of variation were calculated as follows:Single-operator component 2.42 % of the averageBetween-laboratory component 18.79 % of the average9.1.2 Critical Differences—For the components of variancereported in 9.1.1, two averages of observed values should beconsidered significantly different at the 95 % probability levelif the difference equals or exceeds the following criticaldifferences listed below:Critical Difference, % of GrandAverageANumber of Obser-vations in EachAverageSingle-OperatorPrecisionBetween-LaboratoryPrecision10 6.72 52.10__________AThe critical differences were calculated using t = 1.960 which is based on infinitedegrees of freedom.9.1.3 Confidence Limits—For the components of variancenoted in 9.1.1, single averages of observed values have thefollowing 95 % confidence limits:Width of 95 % Confidence Limits,Percent of the Grand AverageANumber of Obser-vations in EachAverageSingle-OperatorPrecisionBetween-LaboratoryPrecision10 ±4.75 ±36.84____________AThe confidence limits were calculated using t = 1.960 which is based on infinitedegrees of freedom.9.2 Bias—No justifiable statement on bias is possible sincethe true value of flexural strength of ceramic whitewarematerials cannot be established and will be different for eachspecific material.MODULUS OF ELASTICITY10. Procedure10.1 Support the specimen in the same way as for themodulus of rupture determination. Set any type of deflectome-ter capable of indicating to 0.001 in. (0.0254 mm) to measuredeflection at mid-span relative to the ends of the span. Applythe load uniformly (see either 4.1.1 or 4.1.2) in accordancewith the shape of the specimen. Stop the loading at 15 %increments of the expected total breaking load, as may previ-ously have been determined in the modulus of rupture tests,and record the corresponding deflections.11. Calculation11.1 Plot the load-deflection readings to a convenient scaleand draw a straight (stress-strain) line to represent, as nearly aspossible, the average of the plotted points below the elasticlimit. (In some materials, increasing departures from a straightline may be noted at the higher stress. Such evidence of plasticflow, or of non-recoverable strain, indicates that the elasticlimit has been exceeded.) If the line does not pass through thezero point, draw a corrected line through this point parallel tothe stress-strain line.11.1.1 Calculate the modulus of elasticity, E, for rectangularspecimens from the coordinates of some convenient point onthe corrected line as follows:E 5 W1L3/4∆bd3(2)C674 − 133where:W1= load coordinate of the selected point, lbf (or N);L = length of span, in. (or mm);∆ = deformation coordinate of the selected point, in. (ormm);b = width of specimen at the center, in. (or mm); andd = thickness of specimen at the center, in. (or mm).11.1.2 Calculate the modulus of elasticity, E, for circularcross-section specimens from the coordinates of some conve-nient point on the corrected line as follows:E 5 4W1L3/3π∆d4(3)where:W1= load coordinate of the selected point, lbf (or N);L = length of span, in. (or mm);∆ = deformation coordinate of the selected point, in. (ormm); andd = diameter of specimen, in. (or mm).12. Report12.1 Report the following information:12.1.1 Identification of the material tested,12.1.2 Stress-strain data and modulus of elasticity for eachspecimen, and12.1.3 In the case of glazed specimens the position of theglazed surface or surfaces.13. Precision and Bias13.1 Measurements of Modulus of Elasticity are inherentlymore precise than measurements of Modulus of Rupturebecause of unaccounted-for material effects during rupture (seeSection 9).14. Keywords14.1 ceramic whiteware materials; flexural propertiesASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. 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