ASTM C848-88(R2020) pdf free download

ASTM C848-88(R2020) pdf free download.Standard Test Method for Young’s Modulus, Shear Modulus, and Poisson’s Ratio For Ceramic Whitewares by Resonance
1. Scope
1.1 This test method covers the determination of the elastic properties of ceramic whiteware materials. Specimens of these materials possess specific mechanical resonance frequencies which are defined by the elastic moduli, density, and geometry of the test specimen. Therefore the elastic properties of a material can be computed if the geometry, density, and me- chanical resonance frequencies of a suitable test specimen of that material can be measured. Young’s modulus is determined using the resonance frequency in the flexural mode of vibra- tion. The shear modulus, or modulus of rigidity, is found using torsional resonance vibrations. Young’s modulus and shear modulus are used to compute Poisson’s ratio, the factor of lateral contraction. 1.2 All ceramic whiteware materials that are elastic, homogeneous, and isotropic may be tested by this test method. 2 This test method is not satisfactory for specimens that have cracks or voids that represent inhomogeneities in the material; neither is it satisfactory when these materials cannot be prepared in a suitable geometry. N OTE 1—Elastic here means that an application of stress within the elastic limit of that material making up the body being stressed will cause an instantaneous and uniform deformation, which will cease upon removal ofthe stress, with the body returning instantly to its original size and shape without an energy loss. Many ceramic whiteware materials conform to this definition well enough that this test is meaningful. N OTE 2—Isotropic means that the elastic properties are the same in all directions in the material. 1.3 A cryogenic cabinet and high-temperature furnace are described for measuring the elastic moduli as a function of temperature from −195 to 1200 °C. 1.4 Modification of the test for use in quality control is possible. A range of acceptable resonance frequencies is determined for a piece with a particular geometry and density. Any specimen with a frequency response falling outside this frequency range is rejected. The actual modulus of each piece need not be determined as long as the limits of the selected frequency range are known to include the resonance frequency that the piece must possess if its geometry and density are within specified tolerances. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.6 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
4. Apparatus
4.1 The test apparatus is shown in Fig. 1. It consists of a variable-frequency audio oscillator, used to generate a sinusoi- dal voltage, and a power amplifier and suitable transducer to convert the electrical signal to a mechanical driving vibration. A frequency meter monitors the audio oscillator output to provide an accurate frequency determination. A suitable suspension-coupling system cradles the test specimen, and another transducer acts to detect mechanical resonance in the specimen and to convert it into an electrical signal which is passed through an amplifier and displayed on the vertical plates ofan oscilloscope. Ifa Lissajous figure is desired, the output of the oscillator is also coupled to the horizontal plates of the oscilloscope. If temperature-dependent data are desired, a suitable furnace or cryogenic chamber is used. Details of the equipment are as follows: 4.2 Audio Oscillator, having a continuously variable fre- quency output from about 100 to at least 20 kHz. Frequency drift shall not exceed 1 Hz/min for any given setting. 4.3 Audio Amplifier, having a power output sufficient to ensure that the type oftransducer used can excite any specimen the mass of which falls within a specified range. 4.4 Transducers—Two are required; one used as a driver may be a speaker ofthe tweeter type or a magnetic cutting head or other similar device, depending on the type of coupling chosen for use between the transducer and the specimen. The other transducer, used as a detector, may be a crystal or magnetic reluctance type ofphonograph cartridge. Acapacitive pickup may be used if desired. The frequency response of the transducer shall be as good as possible with at least a 6.5-kHz bandwidth before 3-dB power loss occurs. 4.5 Power Amplifier, in the detector circuit shall be imped- ance matched with the type of detector transducer selected and shall serve as a prescope amplifier. 4.6 Cathode-ray Oscilloscope, shall be any model suitable for general laboratory work.