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Elasticity modulus of grinding wheels and its impact on their in-process behavior,
W. König, H. Föllinger, Technical University of Aachen, Lehrstuhl für Technologie der Fertigungsverfahren
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Grinding wheel screening by the GrindoSonic method
C.H. Shen, General Motors, Technical Centre Warren
A series of experiments were performed to evaluate the Grindo Sonic method which purported to measure the elastic modulus of a wheel non-destructively. The modulus measurements showed that identically labelled wheels might have very different modulus readings. Grinding tests using these wheel indicated that the grinding performance in terms of wheel wear could be correlated successfully with the elastic modulus.
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GrindoSonic device, checking grinding wheel grade,
Ford Bordeaux, Tool Engineering Developments
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Honing stone testing pays big dividends,
Cummins
By using stones of similar bond hardness for each honing operation on diesel engine parts, one company has impoved the component’s surface finish, reduced stone consumption considerably, and cut overall manufacturing costs. Arthur Barker reveals that the savings are archieved with a device which tests and classifies the stones.
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Interoffice Memorandum : GrindoSonic selection of honing stones (cylinder liners) and checking of E-modulus on cam grinding wheels,
A.A. Hunter
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Practical application of the sonic testing to determine the grade of grinding wheels,
S. Okada, Meguro Steel Works, a division of Mitsui Mining and Smelting Co.
A bonded abrasive is composed of abrasive grains and bonding material. As it is mostly used in a shape of a disk, the name “grinding wheel” has been used in a broad sense inclusive of a grinding stick.
Grade or hardness is one of the most important characteristics of a grinding wheel, because it is closely related to the grinding performance at work. Although numerous methods for testing grade of a grinding wheel have been in use up to now, a conclusive method has not yet been agreed upon to the satisfaction of all.
Most of grinding wheel manufacturers employ their own mechanical graders such as scratching and sand-blasting testers. In recent years the sonic method has gradually been in use, because the measuring procedure is handy and non-destructive, and the measured value has a real physical significance.
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Recent advances in grinding,
P. Guenther Werner, Massachusetts Institute of technology
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Sonic testing of resinoid grinding wheels,
Shojiro Okada, Mitsui Grinding Wheel Co.
The grade is one of the most important characteristics of grinding wheels and generally determined by a mechanical device such as the Okoshi grade tester. The E-modulus as a measure of the wheel grade has a persuasive power to both grinding researchers and wheel manufacturers because of its real physical significance. This handy and non-destructive sonic method is already of considerable use for the vitrified grinding wheel but not yet satisfactorily applied to the resinoid one, because this method is supposed to be improper to determine the E-modulus of the resin by reason of its damping nature.
In this test, the Grindo-Sonic was adopted as a testing device to determine the E-modulus because of the measuring rapidness and the accuracy of the results. At the same time, the bending test was carried out using the same specimens.
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Surface finish treatise in relation to Cylinder Liners,
Eric Willis, GKN Sheepbridge Stokes Ltd
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The evaluation of NDT techniques for abrasive wheels,
R.L. Smith, NDT Centre of AERE Harwell
A study into the techniques available for the non-destructive testing of abrasive wheels was carried out for the Health and Safety Executive. These included X-radiographic, ultrasonic and resonance techniques. A series of fracture studies was also carried out to estimate the typical critical crack sizes for abrasive wheels in use and the results used as an aid to assessing the applicability of each technique. An ultrasonic pitch-catch technique was developed which can achieve the required resolution and is readily adaptable to practical situations. However, in the opinion of the manufacturers and users of abrasive wheels the current practice during manufacture and recommended operating procedures for use are sufficient to ensure the integrity of such wheels.
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The Structure and Bonding of Highly Stressed Vitrified Bonded Cutting Tools, Aufbau und Bindungsmatrix hochbeanspruchter keramisch gebundener Zerspanungswerkzeuge
H.J. Padberg
Vitrified bonds consist of clays, kaolins, feldspas, frits and other additives. Depending on the bond type, the firing process, the requirements of the grinding task (characterized by the grinding process, grinding machine and workpiece to be machined), the abrasives, the rotation speeds and firing temperatures, the ratio of these components can be varied and modified according to specific requirements. Characteristic criteria for the different bond types – which like fused bonds possess a glassy character-, or which like the sintered bonds possess a porcelain-like character – are the so-called sinter point and hemispherical temperature (HKP), which can be determined with the help of a heating microscope. Practical examples will be given illustrating how considerable improvements in effectivity can be achievd by the modification of the bond matrix to correspond the specific requirements of the grinding task.
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A non-destructive method of determining rock strength,
Robert J. Allison, University of Durham, Department of Geography
Rock material strength is an important componet of many geomorphological studies. Current methods for determining this parameter result in sample destruction, preventing further analysis. A new non-destructive technique is described for indirectly determining material strength, by measuring Dynamic Young’s Modulus. Tests have been conducted on Jurassic Portland Limestone and Upper Cretacious Chalk to assess the apparatus. Young’s Modulus is becoming an increasingly important rock material property.
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Non-destructive determination of Young's modulus and its relationship with compressive strength, porosity and density,
R.J. Allison, University of Durham, Department of Geography
The Grindosonic apparatus, new equipment capable of indirectly determining rock compressive strength, is discussed. This utilizes the principle that elasticity theory can be applied to rock masses (Attewell & Farmer 1976; Selby 1982) and directly measures the fundamental vibration frequency of a rock sample of regular dimensions following shock excitation. Dynamic Young’s modulus and a variety of other parameters can be established.
Samples of Upper Cretaceous Chalk en Upper Jurassic Portlend Limestone are used to demonstrate the apparatus and ist application. Test specimens were prepared and analysis conducted on material extracted at a number of locations throughout the Isle of Purbeck in Dorset, UK. Samples suitable for deformation in traxial compression were also prepared and correlations drawn between compressive strength, dynamic Young’s modulus, porosoty and density.
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The Relations between Modulus of Elasticity and Temperature in the Context of the experimental Simulation of Rock Weathering by Fire,
A.S. Goudie, R.J. Allison, S.J. McLaren
Fires occur frequently in many biomes and generate high temperatures on the ground surface. There are many field examples of fire causing rock disintegration. The simulation of fire in the laboratory (using a furnace) and the monitoring of changes in rock modulus of elasticity (with a Grindosonic apparatus), reveal that different rocks respond differently to heating. Significant decreases in elasticity occur at temperatures as low as 200°C and granites display particularly marked reductions. Extended periods of heating are not required for significant reductions to occur. It is postulated that the degree of change in elasticity as a result of simulated fire is such that rock outcrops subjected to real fires are likely to be sufficiently modified as to increase their susceptibility to erosion and weathering processes.
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Geotechnical Properties of Rock Masses : their Control on Slope Form and Mechanisms of Change along the Napier Range, Western Australia,
R.J. Allison, A.S. Goudie, N.J. Cox
Slope form and the mechanism of change which slope profiles exhibit are frequently subject to scrutiny by geomorphologists. However, the majority of studies do not consider fundamental material properties and rock mass geotechnical characteristics. The results presented highlight the importance of synthesising standard geomorphological site investigation techniques with quantifiable rock geotechnical parameters, in order to understand slope form and development. Field research has been undertaken along the Napier Range of the Kimberley Region, Western Australia. The Napiers are an extensive, upraised, Devonian limestone reef, alon which a number of characteristic slope profiles can be identified. Laboratory studies of yield strength, stress-strain characteristics, elastic properties and discontinuity parameters have been conducted on material sampled at sites representative of each slope profile type. The results suggest that highly concave slopes have formed in limestone which exhibits little deformation before yield, has a high modulus of elasticity and few irregular fractures. Convexo-concave slopes, on the other hand, are characteristic of material which displays a greater ability to strain below yield, a relatively low modulus of elasticity and a pronounced discontinuity pattern. It is the combination of the field investigations and laboratory study which most successfully explains variations in slope form.
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The Form of Rock Slopes in Tropical Limestone and their Association with Rock Mass Strength,
R.J. Allison, A.S. Goudie
The form of rock slopes has been studied in a tropical limestone environment. Investigations have concentrated on the Napier Range, an upper Devonian fringing and barrier reef complex, in the Kimberley region of Western Australia. Seven different characteristic slope forms occur along the Range. A minimum of three profiles have been analysed for each type of slope, using a high-length integral. A rock mass classification has been completed on each surveyed transect. The rock mass classification technique has not been previously applied to tropical limestone slopes. Results indicate that by aggregating data for individual slope units along a profile, associations can be drawn between profile shape and the geometrical characteristics of the rock mass as determined by its mass strength. A continuum of slope profile types has been defined for the Napeir Range and within the continuum, the importance of specific rock mass properties in determining spatial variations in slope form have been identified.
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Critical degree of saturation as a threshold moisture level in frost weathering of limestones
Angélique Prick, Université de Liège
The moisture content has a deciding impact on the behaviour of a rock undergoing frost action. A particular critical degree of saturation Scr characterizes each material; only when the moisture content exceeds Scr will the material be damaged by frost. This parameter was defined for ten French limestones by measuring their dynamic Young’s modulus. Scr values depend on porosimetric characteristics of the rocks, especially their trapped porosity. The critical degree of saturation accounts for the various rock dilatometrical behaviours during freeze-thaw cycle.
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Correlating Process Parameters Using NDT,
Mark S. Love, Florida Tile
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Non-destructive testing of boron nitride,
Ruth Engel, Armco Inc.
Hexagonal boron nitride (BN) is the material of choice for manufacturing break rings for the horinzontal continuous casting steel. Due to the criticality of this application, only a 100% acceptance level can be tolerated. A non-destructive testing method was successfully developed to accomplish this. Comparison of this method with more traditional non-destructive tests showed it to be comparable.
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Chemically vapor deposited silicon carbide (SiC) for optical applications
Michael A. Pickering, Raymond L. Taylor, Joseph T. Keeley of Morton International, George A. Graves of University of Dayton Research Institute
In this paper we present important physical, thermal, mechanical and optical properties of cubic silicon carbide produced via a bulk chemical vapor (CVD) process developed at CVD Incoporated. This CVD SiC has been identified as the leading mirror material for high energy synchrotron radiation because of its high thermal conductivity, low thermal expansion, high polishability, and high reflectance in the vacuum UV. However, it has been difficult to obtain high quality, monolithic. CVD SiC mirrors in large sizes i.e. greater than 10-20 cm. Recently, CVD Incorparated has been successful in scaling an SiC CVD process to produce large monolithic pieces of SiC up to 60 cm (24 in.) in diameter and plates up to 76 cm (30 in.) long by 46 cm (18 in.) wide with thicknesses up to 13 mm (0.5 in.). The properties of this material that can make it attractive for optical applications, such as synchrotron optics, will be discussed.
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Non-destructive Analysis of Ceramic Packages using Resonant Frequency, Sheera Knecht, Joyce Hyde and Teri Giverson, Digital Equipment Corp.
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Processing and Properties of TiZrC and TiZrB2 Solid Solution Materials
Cathleen Mroz, Advanced Refractory Technologies Inc.
TiZrC and TiZrB2 solid solution materials were synthesized by conventional powder production methods. These materials exhibited non-linear, and generally superior, mechanical properties when compared to end member constituents.
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Elastic Properties of Polycrystalline Cubic Boron Nitride and Diamond by Dynamic Resonance Measurements
Mark. P. D’Evelyn, Kornelija Zgonc
The elastic properties of ceramic materials are important to their performance in severe abrasion and wear applications and also provide a useful, quantitative measure of quality. We have measured the Young’s modulus E, shear modulus G, and Poisson’s ratio n of several commercial polycrystalline cubic boron nitride and diamond products, in the form of free-standing disks, using the dynamic resonance method. The latter method is accurate and fast enough for routine quality control. Measurements on polycrystalline cBN yielded values of E, G, and n in the ranges of 630-770 GPa, 270-340 GPa, and 0.14-0.18, respectively, depending on the volume fraction of superabrasive, binder phase and microstructure. As a point of comparison, the orientation-averaged values of E, G, and n for pure, equiaxed, polycrystalline cBN are calculated as 909 GPa, 405 GPa, and 0.12, respectively. Measured values of E, G, and n for sintered diamond lay in the ranges of 915-990 GPa, 415-450 GPa, and 0.10-0.11, respectively. The modulus results are compared to selected additional material properties.
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Alumina additions affect elastic properties of electrical porcelains
S. Bribiesca Vazquez, J.C. Mejia Velasquez, J. Reyes Casga
The partial substitution of alumina for feldspar in an electrical porcelain leads to an increase in Young’s modulus from 38.27 to 62 Gpa, reaching the maximum value when the firing temperature is 1350°C.
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Elastic modulus versus bond length in lanthanum chromite ceramics
Charles S. Montross, Advanced Ceramic Development Center, University of Queensland
The elastic moduli of both oxidized and reduced MgO, CaO and SrO doped lanthanum chromites were measured by the dynamic Young’s Modulus method. The elastic modulus was also measured as a function of the CaO content in both the oxidized and reduced states. From Reitveld fitting of the X-ray diffraction data, corresponding cation to anion atomic distances were calculated and compared. Changes in the elastic modulus correspond to changes in the Cr+3 to O-2 average interatomic distance for the dopants used.
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The porosity dependence of flexural modulus and strength for capsule-free hot isostatically pressed porous alumina
Y.B.P. Kwan, D.J. Stephenson, J.R. Alcock
Structural properties such as flexural moduli and strength have been measured for a range of porous alumina specimens of different initial powder sizes and final porosities, sintered using the capsule-free hot isostatic pressing method. This processing method produces a porous body in which the closed porosity is negligible. The relationship of these structural properties to total porosity has been investigated. The results indicate that both a power and an exponential function could adequately describe the porosity dependence of flexural strength. The strength values obtained were test method dependent, and were significantly lower for specimens with sintering aids. A power law model based on a critical porosity, as proposed by Phani, gave the best fit for the modulus measurement data. No dependence of mechanical properties on particle size was observed. The strength measurement results did not appear to support suggestions that better strength could be obtained by the capsule-free hot isostatic pressing method than conventional sintering, as reported elsewhere.
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Flexural and torsional resonances of ceramic tiles via impulse excitation of vibration
A.A. Wereszczak, R.H. Kraft, J.J. Swab, U.S. Army Research Laboratory
A practice was demonstrated that could independently determine, with high resolution, bulk E, G and ν of a disk, square, hexagonal, and half-hexagonal ceramic tiles or plates. The method combines modal finite element analysis and the flexural and torsional resonance values (measured by impulse excitation of vibration) for a given geometry and material. The consideration of both resonances is important in this practice because ν is able to be explicitly determined as a consequence and its value does not need to be assumed to determine E and G (as would occur when only one of their resonant frequency values is known).
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Correlation between the breaking strength during flexion vs. the GrindoSonic reading for tile
Grafieken
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Effect of Sintering Aid Composition on the Processing of Si3N4/BN Fibrous Monolithic Ceramics
Rodney W. Trice,† and John W. Halloran
Si3N4/BN fibrous monoliths were prepared with 4 wt% Y2O3 added as a sintering aid to the Si3N4. Residual carbon, present in the billet before hot-pressing, was shown to influence the final microstructure. The sintering aid glass, known to migrate into the BN cell boundaries during hotpressing, was not sufficient in quantity to prevent premature shear failure when samples were tested in flexure. Increasing the hot-pressing temperature alleviated this problem. For flexure samples tested at 1400°C, fibrous monoliths fabricated with 4 wt% Y2O3 demonstrated linear-elastic loading behavior at a greater stress than fibrous monoliths fabricated with 6-wt%-Y2O3/2-wt%-Al2O3 sintering aids.
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Mode I Fracture Toughness of a Small-Grained Silicon Nitride: Orientation, Temperature, and Crack Length Effects
Rodney W. Trice,† and John W. Halloran
The Mode I fracture toughness (KIC) of a small-grained Si3N4 was determined as a function of hot-pressing orientation, temperature, testing atmosphere, and crack length using the single-edge precracked beam method. The diameter of the Si3N4 grains was <0.4 µm, with aspect ratios of 2–8. KIC at 25°C was 6.6 ± 0.2 and 5.9 ± 0.1 MPa.m1/2 for the T–S and T–L orientations, respectively. This difference was attributed to the amount of elongated grains in the plane of crack growth. For both orientations, a continual decrease in KIC was observed through 1200°C, to ?4.1 MPa.m1/2, before increasing rapidly to 7.5–8 MPa.m1/2 at 1300°C. The decrease in KIC through 1200°C was a result of grain-boundary glassy phase softening. At 1300°C, reorientation of elongated grains in the direction of the applied load was suggested to explain the large increase in KIC. Crack healing was observed in specimens annealed in air. No R-curve behavior was observed for crack lengths as short as 300 µm at either 25° or 1000°C.
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Mechanical properties of directionally solidified Al2O3–ZrO2(Y2O3) eutectics
J.Y. Pastor, P. Poza, J. LLorca, J.I. Peňa, R.I. Merino, V.M. Orera
The relationship between microstructure and mechanical properties was studied in Al2O3–ZrO2 eutectic rods. The material, produced by directional solidification using the laser-heated float zone method, was formed mainly of colonies consisting of a fine interpenetrating or ordered network of ZrO2 and a-Al2O3 surrounded by a thick boundary region that contained pores and other defects. The flexure strength of the eutectic rods was excellent (>1.1 GPa) owing to the small critical defect size and the high toughness (7.8 MPa.m1/2). No microstructural changes were observed after about 1 h of exposure at 1700 K, and the eutectic oxide maintained a very high strength up to this temperature. The nature of the critical defects that led to fracture, the toughening micromechanisms, and the differences between the longitudinal and transverse strength are discussed in the light of the microstructural features of the material.
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Hertzian Testing of Ceramics
S.G. Roberts, British Ceramic Proceedings 59, edited by W. Lee and B. Derby (Institute of Materials, 1999), 45-60.
The paper reviews recent work on the fracture mechanics of ring crack formation, from pre-existing small surface cracks, when a hard sphere is pressed elastically against a hard surface. It summarises the ways in which data from these “Hertzian” tests may be used to determine the extent of surface cracking damage, the materials fracture toughness, and the strength of any residual stress in the surface. Examples are given of experiments applying these test methods.
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Crack Deflection and Propagation in Layered Silicon Nitride/Boron Nitride Ceramics
Desiderio Kovar, M. D. Thouless, and John W. Halloran, University of Michigan.
Crack deflection and the subsequent growth of delamination cracks can be a potent source of energy dissipation during the fracture of layered ceramics. In this study, multilayered ceramics that consist of silicon nitride (Si3N4) layers separated by boron nitride/silicon nitride (BN/Si3N4) interphases have been manufactured and tested. Flexural tests reveal that the crack path is dependent on the composition of the interphase between the Si3N4 layers. Experimental measurements of interfacial fracture resistance and frictional sliding resistance show that both quantities increase as the Si3N4 content in the interphase increases. However, contrary to existing theories, high energy absorption capacity has not been realized in materials that exhibit crack deflection but also have moderately high interfacial fracture resistance. Significant energy absorption has been measured only in materials with very low interfacial fracture resistance values. A method of predicting the critical value of the interfacial fracture resistance necessary to ensure a high energy-absorption capacity is presented.
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Influence of Microstructure and Temperature on the Interfacial Fracture Energy of Silicon Nitride/Boron Nitride Fibrous Monolithic Ceramics
Rodney W. Trice and John W. Halloran, University of Michigan.
The microstructure and interfacial fracture energy of silicon nitride/boron nitride fibrous monoliths, GBN, were determined as a function of starting silicon nitride composition and temperature using the method described by Charalambides. The glassy phase created by the sintering aids added to the silicon nitride cells was shown to migrate into the boron nitride cell boundaries during hot-pressing. The amount of glassy phase in the boron nitride cell boundaries was shown to strongly influence GBN at room temperature, increasing the fracture energy with increasing amounts of glass. Similar trends in the interfacial fracture energy as a function of temperature were demonstrated by both compositions of fibrous monoliths, with a large peak in GBN observed over a narrow temperature range. For silicon nitride cells densified with 6 wt% yttria and 2 wt% alumina, the room-temperature interfacial fracture energy was 37 J/m2, remaining constant through 950°C. A sharp increase in GBN, to 60 J/m2, was observed between 1000° and 1050°C. This increase was attributed to interactions of the crack tip with the glassy phase in the boron nitride cell boundary. Measurements at 1075°C indicated a marked decrease in GBN to 39 J/m2. The interfacial fracture energy decreased with increasing temperature in the 1200° to 1300°C regime, plateauing between 17 to 20 J/m2. A crack propagation model based on linkup of existing microcracks and peeling/cleaving boron nitride has been proposed.
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Y-TZP ceramics with tailored toughness
B. Basu, J. Vleugels and O. Van Der Biest, Key Engineering Materials Vols. 206-213 (2002) pp. 1185-1188
Despite the considerable improvement in the understanding of transformation toughening accomplished in the last three decades, it remains an important challenge to be able to control and tune the tetragonal ZrO2 phase transformability and associated toughness of polycrystalline tetragonal zirconia (Y-TZP) ceramics. The problem of controlling the toughness of Y-TZP is investigated in the present paper by comparing the mechanical behaviour of a number of ceramics derived from commercial co-precipitated and yttria-coated zirconia starting powders as well as a range of experimental powder mixtures, obtained by mixing monoclinic and 3 mol % yttriastabilised powders. Based on the experimental results, a simple route to tailor the toughness of YTZP ceramics is reported. The effectiveness of this approach was investigated and the microstructural origin influencing transformation toughening is elucidated. The difference in toughness is explained in terms of the tetragonal grain size and the overall amount and distribution of yttria in the sintered ceramics. The overall yttria stabiliser content is of primary importance, the yttria distribution however was found to be an additional important microstructural variable influencing the transformation toughness of the investigated Y-TZP ceramics.
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Kinetics study of ab-plane crack propagation by a modulus measurement in single domain YBa2Cu3Ox
D. Shi, P. Odier, A. Sulpice, D. Isfort, X. Chaud, R. Tournier, P. He, R. Singh, Physica C 384 (2003) 149–158
Young’s modulus experiments have been carried out to study the kinetics of ab-plane crack propagation in single domain YBa2Cu3Ox (YBCO) during a prolonged oxygen heat treatment at 400ºC up to 188 h. It has been found that the modulus value experiences a rapid fall between the annealing time 48 and 96 h. X-ray difraction (XRD) experiments have been carried out to investigate the structural phase transition during the oxygenation process. Consistently, a difraction peak shift has been observed in this region that indicates a massive tetragonal-to-orthorhombic (T-to-O) transition. SQUID magnetization measurements of annealed samples have shown clear oxygen inhomogeneity in this regime suggesting a T-to-O phase boundary in the crystal. A physical model is provided to describe the operating mechanism of crack propagation in single domain YBCO.
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Mechanical Properties of Textured Bi2Sr2CaCu2O8+d High-Temperature Superconductors
Jose Ygnacio Pastor, Pedro Poza, and Javier Llorca, Polytechnic University of Madrid, J. Am. Ceram. Soc., 82 [11] 3139–44 (1999)
The mechanical properties of Bi2Sr2CaCu2O8+d fibers produced via laser-induced directional solidification at different growth rates were determined through longitudinal and transverse tension tests, as well as flexure tests. In addition, polished sections of as-received fibers and the fracture surfaces of the broken samples were examined using scanning electron microscopy to elucidate the relationship between the microstructure and the mechanical properties. The fibers were anisotropic, and the transverse fiber strength was very low, because of early failure via cleavage of the grains perpendicular to the c-axis. The longitudinal strength and the degree of anisotropy increased as the fiber growth rate decreased, whereas the transverse strength followed the opposite trend. This behavior was due to changes in the porosity and the alignment of the crystals along the fiber axis.
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Determination of Young's modulus of dental composites : a phemenological model,
M. Braem, V.E. Van Doren, P. Lambrechts, G. Vanherle
The Young’s Moduli of isotropic dental restorative composites are determined with a non-destructive dynamic method, which is based on the measurement of the duration of the fundamental period for the first harmonic of a freely oscillating sample. Statistical analysis of these results yields a phenomenological model in which Young’s modulus is given by an exponential rule of mixtures of the matrix phase and the filler phase of the composites. It is found that this phenemenological rule is substantiated empirically.
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The impact of composite structure on its elastic response,
M. Braem, P. Lambrechts, V. Van Doren and G. Vanherle
The non-destructive determination of Young’s modulus of dental composites by measn of the fundamental period was found to be reliable and accurate. Post-polymerization effects could clearly be detected. Exponential regression analysis showed a correlation coefficient of 0.92, after logarithmic transformation, with volumetric filler content.
The high accuracy and reliability of the measurments themselves are reflected in low standard deviations. The results are in excellent agreement with those of other investigations. Furthermore, the ease and speed of operation make this new procedure a powerful laboratory tool for material-testing and practical large-scale investigations.
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The relationship between test methodology and elastic behavior of composites,
M. Braem, C.L. Davidson, G. Vanherle, V. Van Doren and P. Lambrechts
Comparisons were made of the Young’s moduli obtained with tests that impose static, low-frequency, or high-frequency elastic deformations on dental composite systems.
The frequency of the imposed stress was reflected in the absolute value of Young’s modulus. However, the values obtained at different test frequencies could be compared and understood by taking into account this frequency dependence. It was thus found that the composite structure largely determined the type of reaction to the imposed stress. The fundamental period test permitted the greatest differentiation in the classic behavior of the investigated composites.
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Alternate Test Methods for Determining Mechanical Properties of Graphite Epoxy Materials,
Michael J. Viens, Goddard Space Flight Center
The work performed for this memorandum investigated the use of three devices which could potentially reduce both cost and turn around time for testing graphite epoxy (Gr/Ep) tensile coupons. Gr/Ep test coupons are typically tabbed to facilitate load transfer to the test coupon and are strain gauged to determine stiffness and strain at failure of the test coupon. The implementation of the aforementioned devices would eliminate the need for both test tabs and the strin gauges.
The tensile loading of tabless coupons was performed using hydraulic grips with hybrid wedge surfaces to transfer load the test coupons. The strain in the test coupons was monitored using a laser extensometer. The coupon stifness was measured prior to tensil testing with a sonic resonance measurement system. This memorandum reports the results of these tests and compares the strength results to that of prvious tests and the strain results obtained using strain gauges.
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Determination of Elastic Moduli of Fiber-Resin Composites Using an Impulse Excitation Technique
Michael J. Viens, Jeffrey J. Johnson
The elastic moduli of graphite/epoxy and graphite/cyanate ester composite specimens with various laminate lay-ups was determined using an impulse excitation/acoustic resonance technique and compared to those determined using traditional strain gauge and extensometer techniques. The stiffness results were also compared to those predicted from laminate theory using unaxial properties. The specimen stiffness interrogated ranged from 12 to 30 Msi. The impulse excitation technique was found to be a relatively quick and accurate method for determining elastic moduli with minimal specimen preparation and no requirement for mechanical loading frames. The results of this investigation showed good correlation between the elastic modulus determined using the impulse excitation technique, strain gauge and extensometer techniques, and modulus predicted from laminate theory. The flexural stiffness determined using the impulse excitation was in good agreement with that predicted from laminate theory. The impulse excitation/acoustic resonence interrogation technique has potential as a quality control test.
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Particulate-Reinforced Titanium Alloy Composites Economically formed by Combined Cold and Hot Isostatic Pressing,
Stanley Abkowitz, Paul F. Weihrauch, Susan M. Abkowitz
Dynamic Young's Modulus Measurements in Metallic Materials : Results of an Interlaboratory Testing program,
A. Wolfenden, M.R. Harmouche, G.V. Blessing, Y.T. Chen, P. Terranova, V. Dayal, V.K. Kinra, J.W. Lemmens, R.R. Philips, J.S. Smith, P. Mahmoodi and R.J. Wann
The results of a round-robin testing study are presented for measurements of dynamic Young’s modulus in two nickel-based alloys. The Interlaboratory Testing Program involved six types of apparatus, six different organisations, and specimens from a well-ducumented source. All the techniques yielded values of dynamic Young’s modulus that agreed within 1.6% of each other. For Inconel alloy 600 the dynamic modulus was 213.5 Gpa with a standard deviation of 3.6 Gpa; For Incoloy alloy 907 the corresponding values were 158.6 and 2.2 Gpa, respectively. No significant effect of frequency over the range 780 Hz to 15MHz was found.
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Resonant frequency measurements for the determination of elastic properties of powder metallurgy components
C.J. Yu, R.J. Henry, T. Prucher, S. Parthasarathi, J. Jo of Concurrent Technologies Corporation
The resonant frequency technique has proven to be a valuable tool for measuring, nondestructively, the elastic properties of powder metallurgy materials. This paper reports the results of a study on the use of resonant frequency techniques to determine elastic moduli of a wide range of pressed and sintered P/M materials. Resonant frequency techniques that were utilized included sine wave excitation, random signal excitation and impulse excitation. Results show good agreement between the elastic moduli determined dynamically and those obtained from mechanical testing (as published in MPIF Standard 35). The variation of elastic moduli with density is also presented. Also, an effort has been made to evaluate the accuracy of frequency measurements and the calculated elastic moduli for various testing techniques. These results suggest the use of nondestructive resonant frequency techniques as alternative tool to monitor elastic properties of P/M materials.
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Mechanical properties of Nylon bonded Nd–Fe–B permanent magnets
Monika G. Garrell, Albert J. Shih, Bao-Min Ma, Edgar Lara-Curzio, Ronald O. Scattergood, Journal of Magnetism and Magnetic Materials 257 (2003) 32–43
Tensile and flexural strengths as well as Young’s modulus of Polyamide-11 (Nylon-11) based injection molded Nd–Fe–B magnets have been determined from _401C to 1001C. Two types of Nd–Fe–B powders were included in this study. One is the conventional melt spun powder of irregular shape, the other is the atomized powder of spherical morphology. It was found that the tensile strength varies significantly with both test temperature and morphology of Nd–Fe–B powder. For a fixed volume fraction of magnet powder, the tensile strength decreases with increasing temperature. For bonded magnets made of melt spun powder, the tensile strength increases with increasing volume fraction of magnet powder. Specimens made of spherical atomized powders exhibit much lower tensile strength and better flexibility when compared to those made of melt spun powder. Scanning electron microscopy (SEM) analysis indicated that the debonding at the Nd–Fe–B powder and Nylon interface is the main cause of failure at 23ºC and 100ºC. At -40ºC, a different failure mechanism with the fracture of Nd–Fe–B particle was observed on magnets prepared from melt spun powders. For the specimen containing 59.7 vol% of melt spun powder, a bending strength of 41MPa and dynamic Young’s modulus of 12.7 GPa were obtained.
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Relation between Young’s modulus of set plaster and complete wetting of grain boundaries by water
Elisabeth Badens, Stéphane Veesler, Roland Boistelle, Dominique Chatain, CRMC2-CNRS Marseille
The mechanical behavior of set plaster has been studied in humid atmospheres. This material is made of entangled needle-shaped gypsum crystals. At room temperature, Young’s modulus of set plaster decreases as the coexistence of gypsum and water is approached by increasing the humidity of the surrounding air. Simultaneously, the thickness of the absorbed water layer at the grain boundaries between the gypsum crystals is shown to diverge. It is suggested that the gypsum crystals are able to slide along certain grain boundaries because the viscosity of the water film approaches that of bulk liquid water. Small additions of D,L-tartaric acid prevent both the adsorption of water at grain boundaries of gypsum and the decrease of the Young’s modulus of set plaster.
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ASSESSMENT OF THE CHLORIDE MIGRATION COEFFICIENT, INTERNAL FROST RESISTANCE, SALT FROST SCALING AND SULPHATE RESISTANCE OF SELF-COMPACTING CONCRETE - with some interrelated properties
Bertil Persson, Lund University.
In this project the objectives were to investigate the chloride migration coefficient, D, defined by Tang, to determine the salt frost scaling, the internal frost resistance and the sulphate resistance of SCC that contains increased amount of filler, different types of casting and air content. The objective was also to compare the result of salt frost scaling, internal frost resistance, sulphate resistance and chloride ingress of SCC with the corresponding properties of normal concrete, NC, with the same water-cement ratio, w/c = 0.39. Finally the objective was to give recommendations how to produce a SCC durable to frost and chlorides.
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A method for thermal cycling refractories and an appraisal of its effect by a non-destructive technique,
T.J. Coppack, Morgan Refractories Ltd.
The use of the ribbon test method in conjunction with measurement of M.O.E. by transient vibration has proved of significant assistance in the comparison of various refractory grades for thermal shock resistance and is now proving a useful tool in the development of new products. It is hoped that, once the parameters of the test are more fully understood and standardised, it will be only necessary to measure elastic modulus before and after 10 cycles or perhaps even 5 cycles will be sufficient.
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Prediction of refractory Strength using non-destructive sonic measurements
Fawzy Aly and C.E. Semler, Refractories Research Center, The Ohio State University
Mathematical relations were evaluated and equations are presented correlating non-destructive sonic measurements, using either ultrasonic velocity or modulus of elasticity, with modulus of rupture for five representative fired refractory product types, including high alumina (90%), mullite (70% alumina), super-duty fireclay (42% alumina), vitreous silica (99% silica) and carbon. The experimental relations were tested for additional brands and found to yield predicted strengths that were within 0.5% to 6% of the actuals strengths for refractory products having properties similar to the model refractory product used to develop the correlation equation. For refractory products with properties that were dissimilar to the model refractory, the predicted strengths differed from the actual strengths by >20%.
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Resonant frequency testing for refractories
American Ceramic Bulletin, Vol. 70, No. 2
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Sonic Technique Tests Refractory Quality,
G. Boiche, M. Chatre, B. Goublaire, J.C. Gourlaouen and G. Poirson, Minerals & Refractories Laboratories
The impulse excitation technique has been used sucessfully for many years to determine the hardness of grinding wheels and honing stones. Investigations were carried out at the Minarals & Refractories Laboratories to determine if this method could be used to access the quality of refractories.
This nondestructive method uses an instrument originally developed to determine the modulus of elasticity of grinding wheels. Because it measures the frequency of fundamental vibrations, the instrument also should provide excellent results in testing refractory products.
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Sonic Testing of Refractory Brick,
Dr. Jean Petit, Sacilor-Sollac Steelworks
Tests were performed with random batches from three suppliers of ladle brick to determine linear relationships between physical characteristics and the modulus of elasticity. This testing method is of prime importance for studying parts whose proper in-service behavior is essential.
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The significance of the modulus of elasticity for refractory materials and engineering,
J.A.M. Butter, Hoogovens Groep BV
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Practical use of a non-destructive method for testing refractories
T. Richter
The accuracy and advantages of the non-destructive resonant frequency technique (impulse excitation technique) for the final inspection of conventional refractory products are discussed. Mathematical models and correlations for alumina brands are presented.
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Kiln Furniture for Oxide Ceramics : Technical Properties for Increasing Demands
G. Senftleben, H.U. Dorst
SiC-based kiln furniture has a maximum service temperature of 1600°C. Beyond that point, mullite-corundum materials are required. Here it is important that high hot bending strength resp. thermal fatigue in conjunction with adequate thermal shock resistance be achieved through selectively designed microstructures and appropriate raw materials.
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Overview of Refractory Problems in Industry,
C.E. Semler
Refractories are the “Backbone of Industry”. Despite their great importance, refractories are frequently misunderstood, overlooked, and/or abused. The results can be extremely disruptive, costly, and even tragic. This paper defines seven main reasons for refractories problems in industry, and notes seven other contributing factors. Many practical examples are included. Based on an improved understanding of the reasons for refractories problems, as well as a thorough review of all related factors, it is possible to reduce or eliminate unnecessary and unexpected major expenses.
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Technical Memorandum about GrindoSonic,
National Refractories & Minerals
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Processing TiZrC and TiZrB2
Cathleen Mroz, Advanced Refractories Technologies Inc.
TiZrC and TiZrB2 solid-solution materials were synthesized by conventional powder production methods. These materials exhibited nonlinear, and generally superior, mechanical properties when compared to the end-member constituents.
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Evaluation of the modulus of elasticity of refractories
W. Schulle, F. Tomsu, J. Ulbricht
The knowledge of the modulus of elasticity (MoE) of refractories and its dependence on the temperature is necessarily for
° the calculation of the stress-deformation state of kiln linings as a basis for optimizing the kiln construction and for calculating of the allowable speed op the heat up and cool downs.
° the non-destructive quatlity control.
To determine the MoE (ultrasound or resonance frequency) dynamic or static
( dependence of the stress on the deformation by measurement of the mechanical strength) methods are used. The different measurement methods deliver deviant results. To understand these differences, experiments with the following four different refractories were carried out :
° two different mullite bonded corundum refractories – without/with ZrO2 addition
° two different magnesia refractories – with/without ZrO2 addition.
For all four the MoE were measured by different dynamic and static methods. According to the measurement method different values of MoE were received. This is caused by the rheological behaviour of the refractories. At room temperature there is a nearly elastic behaviour. At elevated temperatures non-elastic irreversible time dependent deformations appear. In the application of the MoE values in practice, above all the time coarse of the loading must be taken into account.
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The influence of wood moisture content on dynamic modulus of elasticity measurements in durability testing
L. Machek, H. Militz, R Sierra-Alvarez
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The use of an acoustic technique to assess wood decay in laboratory soil-bed tests
L. Machek, H. Militz, R. Sierra-Alvarez
This study assesses the changes in elastic behaviour (i.e. modulus of elasticity –MOE) and mass loss of different hardwood and softwood species exposed to decay in laboratory soil-bed tests. Elasticity moduli were determined using conventional static methods as well as a dynamic method based on flexural vibration. The results obtained show a high correlation between dynamic and static bending measurements for all the timber species tested at different stages of fungal decay. Furthermore, the non-destructive MOE assessment proved to be a good tool for the early detection of wood decay.
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An appraisal of the GrindoSonic Material Tester
P.J. Emerson, BCIRA
A limited number of tests have been carried out on iron test bars and castings with the Grindo-Sonic material tester. This instrument measures the resonant frequency of the component being tested. It has been found that the Grindo-Sonic readings correspond with the BCIRA sonic test equipment, and hence this instrument could have use in iron foundries. For foundry use, however, the instrument would have to be more robust, and the hand operation used in laboratory tests might not be satisfactory.
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Impulse excitation technique for dynamic flexural measurements at moderate temperature,
K. Heritage, Clayton Frisby and Alan Wolfenden, Texas A & M University, Mechanical Engineering Department
The impulse excitation technique (IET), which is presently a precise and reliable technique for measuring dynamic moduli at room temperature, has been adapted to measure dynamic flexural modulus at temperatures in the range of 25° to 300°C. This modified technique involves a sensitive microphone and electronics to record and analyze the sound waves emitted from a specimen vibrating in the fundamental flexural mode. The fundamental resonant frequency and geometry of the specimen are used to obtain the modulus. The location of the microphone relative to the specimen is critical and is major factor once the specimen is placed within the heated environment. Problems were identified and solved, and test data for aluminum are presented to support the modification of the IET for use at elevated temperatures.
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New Technique for measuring the dynamic Young's modulus between 295 and 6 K,
J. Zhang, A. Nyilas, and B. Obst, Karlsruhe Nuclear Research Centre
A transducer system based on train gauge technology was developed and applied to bar type specimens to determine the dynamic Young’s modulus. The system was installed in a continuous flow cryostat working in the temperature range 295-6K. The adapted technique is the remote mechanical excitation of the bar as a cantilever beam and the on-line determination of the fundamental free vibration frequency using a commercially available electronic instrument. This simple and economic method is able to measure the material’s dynamic Young’s modulus, E, and shear modulus, G, with a high degree of accuracy (error < ± 2.0%). The Poisson’s ratio, ν, can therefore be determined, according to the measured values of E and G. Six different engineering materials were characterized with respect to their elastic properties between 295 and 6 K. The dynamic Young’s modulus versus temperature measurements were compared with the results of static stress – strain measurements carried out in the same test facility.
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Use of an ultrasonic resonance technique to measure the in-plane Young's modulus of thin diamond films deposited by a DC plasma-jet, L. Chandra and T.W. Clyne, University of Cambridge, Department of Materials Science and Metallurgy
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Research Technique in non-destructive testing,
R.S. Sharpe
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An Evaluation of Three Methods to Measure the Dynamic Elastic Modulus of Steel,
A. Wolfenden, W. Schwanz, Texas A & M University, Mechanical Engineering Dept.
An evaluation is made of three methods used to determine the dynamic elastic modulus of steel. The three methods make use of the Grindo-Sonic machine, the Modul-r machine, and the Piezoelectric Ultrasonic Composite Oscillator Technique.
Testing of specimens, all from the same piece of stock, was done using each method and a comparison was performed. Since the assumption that all specimens had the same elastic modulus was not valid, a comprehensive statistical comparison could not be done. Still, all methods produced results that were highly repeatable. In addition, it was determined that long thin specimens did not vibrate in their fundamental mode when tested with the Grindo-Sonic machine and that testing specimens with the Modul-r machine heats the internal coils of the machine which affects the determined modulus values. The width tolerance needed for the Modul-r specimens could not be maintained, and the results of tests on these specimens are not completely valid. The overall mean elastic modulus was 207.1 Gpa with a standard deviation of 2.75 GPa.
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Determination of the elastic moduli of materials at high temperatures by means of a non-contact sensor
F. Lostak, W. Vandermeulen
The determination of the elastic moduli of materials by means of the measurment of the frequencies of the elastic modes has become a celebrated technique (pulse excitation technique). Its non-destructive character and its ease of use in almost all circumstances make it very attractive for research as well as industrial environments. This work describes the state of the art and reports on the development of a non-contact laser-based sensor to detect the elastic deformations of materials even at temperatures up to 1200°C.
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Evaluation of the Elastic and Plastic Properties of Si3N4 by depth sensing indentation
R. Berriche, R.T. Holt, Institute for Aerospace Research, National Research Council of Canada
A high resolution instrument, called the nanomechanical probe, which permits continuous monitoring of load and depth of penetration during indentation and scratch tests have been developed at IAR/NRC. Its principle of operation, specifications and capabilities are discussed. Indentation tests on HIPed silicon nitride samples with densities ranging from about 82 to 99.7% theoretical density have been performed. Hardness values for each sample have been calculated from load vs. depth plots using a new method involving the plastic work dissipated during the indentation process. The elastic properties of the samples have been determined from the slope of the unloading curve using the elastic punch model. The results are compared to those obtained to those by conventional methods.
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Elastic Properties of CVD Diamond via Dynamic Resonance Measurements
Mark P. D'Evelyn, David E. Slutz, Bradley E. Williams, General Electric Corporate R & D, General Electric Superabrasives
Control of the mechanical properties of CVD diamond is essential to achiev optimal performance in various applications. While several methods have been applied to the measurement of Young’s modulus of thick-film CVD diamond, in general these methods are not suitable for diamond characterization on a production scale. In addition, many of these methods cannot determine the shear modulus (or Poisson’s ratio), which is necessary for a complete description of the elastic properties. We have developed a simple dynamic resonance method for determining both the Young’s modulus and shear modulus of free standing CVD diamond in the shape of rectangular plates or round discs. The specimen is supported along nodal lines of flexural or torsional modes. Oscillations are induced by impact from a falling ceramic bead, are senses by a microphone, and the resonant frequencies are determined by a signal analyzer. The Young’s and shear modulus are calculated from the frequencies of the fundamental flexural and torsional modes, respectively, using quasi-analytic formulas. CVD diamond grown by several methods routinely achieves Young’s and shear modulus values above 1000 Gpa and 500 Gpa, respectively, in good accord with theoretical values for pure polycrystalline diamond.
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Determination of the moduli of elasticity of rocks,
B. Christaras, F. Auger, E. Mosse, Aristotle Univerity of Thessaloniki, Poitiers University
In the present investigation, dynamic methods for the determination of moduli of elasticity were compared with direct static methods. The dynamic moduli of rocks, such as Young’s modulus (E) and Poisson’s ratio (ν) were determined, using both mechanical resonance frequency and classic P and S wave ultrasonic velocity techniques. For this purpose rock samples from different areas of France, covering a wide range of velocity values, were used. The mechanical resonance frequencies were investigated using a Grindo-Sonic machine while the P and S wave ultrasonic velocities were measured using a Pundit ultrasonic machine, connected to an oscilloscope. The static moduli were determined using deformation gauges. Statistical inter pretation of the test results indicated significant correlation between these dynamic and static methods. Accordingly, the above non-destructive dynamic methods are suitable for the determination of static moduly of elasticity.
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Evaluation of the GrindoSonic Analyzer for Characterisation of our Chemical Products
Atul C. Sarma, Ph D, Whip Mix Corporation A study on gypsum products, phosphate die refractory materials and phosphate investments by impulse excitation of sonic vibration
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On the measurement of the elastic modulus of a vitreous coating on a titanium substrate by the resonance method
P. Van Landuyt, J.M. Streydio, F. Delannay, E. Munting, Université Catholique de Louvain
We have synthesized a biocompatible glass that, when used as a glaze, allows wetting and adhesion on a titanium substrate. The elastic modulus of this glaze cannot be measured isolately. It is possible to calculate the modulus of the vitreous coating by measuring the resonant frequencies of a titanium plate before and after the deposition of the glaze. The values obtained can be compared to the modulus of elasticity of bulk glass. The evolution and the dispersion of the calculated modulus values are followed in function of the density for three different coatings.
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GrindoSonic : test on tubes, applicability of the system to detect cracks
Lucent Technologies
The GrindoSonic measurement by itself does not provide an indication of cracks. However, calculating ratio’s from two different vibration modes can provide an indication of a problem. Indeed, if we have a defect, it is very unlikely that two independent vibration patterns will shift to the same extent. In this case we will measure the longitudinal vibration mode and the flexural vibration mode. Both results are used to calculate the modulus of elasticity. Because the formulas are totally independent we expect some small variation between the two results that can be expressed in a ratio. This ratio has to be constant. Any significant deviation is an indication of defects. In addition, the GrindoSonic instrument will not provide a repeatable measurement for seriously cracked tubes.
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Master’s Thesis – Non-destructive testing of particleboard with ultra sound and eigen frequency methods
Fredrik Grundström
In the production of particleboard, different properties of the board have to be measured in order to keep the board quality within required limits. Non-destructive methods for this purpose include ultra-sonic testing and eigen frequency testing. These methods have been proposed for measuring the strength of the board after pressing, for process control purposes. The ultra sound velocity and eigen frequency have been proved to be good instruments for doing this. The results show that Young’s modulusand bending strength can be predicted with high accuracy with these methods. Internal bond can only be predicted with poor to fair accuracy with normal regression models. The use of multivariate models most often give better predictions of the internal bond. Multivariate models are best suited for complex predictions if the prediction variables are weak.
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ELASTIC CONSTANTS - THEIR DYNAMIC MEASUREMENT AND CALCULATION
Bernd Weiler, Christian U. Grosse
The modulus of elasticity and the shear modulus can be calculated from the free vibrations of bar-shaped specimens. Therefore, a review of the theoretical bases for the calculation of the moduli is given. Measurements using the Grindo-Sonic device and a device developed at the FMPA were carried out and compared. Both devices turned out to be very efficient, although their features are quite different.
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The Stiffness of Plasma Sprayed Zirconia Top Coats in TBCs
J.A. Thompson, T.W. Clyne, University of Cambridge, Cambridge, UK.
Yttria-stabilised zirconia coatings have been deposited onto nickel superalloy substrates by air plasma spraying (APS). Free standing layers were then obtained by chemical dissolution techniques. The in-plane Young’s modulus values exhibited by these layers were measured using the techniques of cantilever ending and ultrasonic resonant frequency testing during flexural vibration. Young’s modulus data were also obtained by nanoindentation of regions remote from microcracks. The values obtained by bending and frequency measurement were found to be considerably lower than that expected for bulk zirconia, whereas those obtained by the nanoindentation experiments were much closer to that of the bulk ceramic. Tests were also performed on samples which had been heat treated at 1100°C and 1300°C. It was found that the stiffness rose significantly after such treatments. This is attributed to sintering processes which generated extensive healing of microcracks.
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