Dynamic Resonance Method Research Articles

Elastic properties of translucent polycrystalline cubic boron nitride as characterized by the dynamic resonance method

Cubic boron nitride (cBN) is second only to diamond in a number of extreme material properties, and its performance exceeds diamond in many applications involving contact with ferrous alloys and/or high temperatures. However, its properties are less well understood. We have sintered cBN powder (2–4 μm or 8–12 μm particle size) into pure, translucent, polycrystalline compacts by pressing at a pressure of 7.7 GPa and temperatures from 2100 to 2350°C without any sintering agent. We have determined the Young's modulus E, shear modulus G, and Poisson's ratio ν of a number of translucent polycrystalline cBN compacts, in the form of free-standing disks, using the dynamic resonance method. The measured values for E, G, and ν lay in the ranges of 665–895 GPa, 295–405 GPa, and 0.11–0.15, respectively, depending on the grain size of the cBN starting material and the sintering temperature. These values may be compared with the theoretical values of E, G, and ν for pure, equiaxed, cBN of 909 GPa, 405 GPa, and 0.12, respectively. Combining the Young's modulus with previous Vickers hardness measurements, the fracture toughness KIC of well-sintered translucent PCBN is evaluated as 6.8 MPa m1/2. The dependence of the elastic properties on the synthesis conditions is discussed in the context of the microstructure and of related material properties.

Ultrasonic logging as a method of evaluating the static deformation characteristics of real media

The physical causes promoting a difference in the values of the moduli of elasticity determined by static and dynamic (ultrasonic and resonance) methods of investigation were examined. On the basis of analyzing these causes formulas were proposed for calculating longitudinal wave velocities in mutually perpendicular directions for loaded and unloaded states of the object of investigation. The possibility of estimating the static parameters of deformability of a real (not idealized) medium directly from the data of ultrasonic investigations, in particular, from ultrasonic logging data, was shown.

Elastic properties of polycrystalline cubic boron nitride and diamond by dynamic resonance measurements

Abstract 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 ν 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 c-BN yielded values of E, G , and ν 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 ν for pure, equiaxed, polycrystalline c-BN are calculated as 909 GPa, 405 GPa, and 0.12, respectively. Measured values of E, G , and ν 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.

Thermal shock behaviour of unidirectional, 0°/90°, and 2-D woven fibre-reinforced CVI SiC matrix composites

The thermal shock behaviour of NicalonTM fibre-reinforced chemical vapour infiltrated SiC matrix composites with three different types of fibre architecture, unidirectional, 0°/90°, and 2-D woven, has been studied using the water quench technique. Thermal shock induced damage was characterized by the destructive four-point flexure technique and the nondestructive technique of Young's modulus measurement by the dynamic resonance method. It was shown that the unidirectional and 0°/90° composites did not possess satisfactory mechanical properties or resistance to thermal shock because these fibre architectures prevented the composites from attaining high density during infiltration. Excess carbon coating was also found in the unidirectional and 0°/90° composites. Oxidation of this carbon coating contributed to the property degradation at high quench temperature difference. By contrast, the composite with 2-D woven fibre architecture created using the 0°/30°/60° cloth lay-up showed superior mechanical properties and thermal shock resistance. The nondestructive technique of Young's modulus measurement by the dynamic resonance method was successfully used in detecting the thermal shock damage.

Thermal Shock Behavior of Two‐Dimensional Woven Fiber‐Reinforced Ceramic Composites

The thermal shock behavior of three types of two‐dimensional woven, continuous fiber‐reinforced (NextelTM 312 (3M Co., St. Paul, MN) or NicalonTM (Nippon Carbon, Tokyo, Japan)) ceramic matrix (silicon carbide matrix that had been processed by chemical vapor infiltration or polymer impregnation and pyrolysis) composites was studied using the water‐quench technique. Thermal‐shock‐induced damage was characterized by a destructive technique of four‐point flexure and a nondestructive technique of Young's modulus measurement by the dynamic resonance method. Compared with monolithic ceramics, the continuous fiber‐reinforced ceramic composites were capable of preventing catastrophic failure that was caused by thermal shock. Analysis of the results that were based on the stresses that were generated by thermal shock and the mismatch of thermal expansion between fibers and matrices suggested possible mechanisms of the thermal shock damage. Preliminary results showed evidence of matrix cracking and delamination because of the thermal shock damage. The feasibility of using the nondestructive technique to detect thermal shock damage also was demonstrated.

Anisotropy of elastic properties in various aluminium-lithium sheet alloys

Anisotropic elastic properties of recrystallized and unrecystallized Al Li sheets have been experimentally studied and compared with theoretically predicted results. A conventional AA2024 alloy in the annealed condition as a reference material has also been investigated. A concept of lithium equivalent has been proposed in order to calculate single crystal elastic constants C 11 , C 12 and C 44 for commercial Al sheet alloys. Subsequently, these calculated single crystal elastic constants were applied to predict the Young's modulus, using Bunge's method with quantitative texture data which were determined by X-ray and neutron diffraction techniques. To calculate the shear modulus the Bunge's method was extended. It is shown that elastic properties of the alloys can be essentially predicted on the basis of Bunge's method with calculated single crystals C ij . The measurement results of the Young's modulus and shear modulus of polycrystalline Al Li alloys were carried out using a dynamic resonance method. They were found to be in fair agreement with calculated curves using the neutron texture data with the calculated single crystal elastic constants C ij . The results showed that elastic properties depend strongly on testing direction due to the crystallographic texture and grain shape. The texture gradients also strongly affected the elastic properties of Al Li alloys, but only slightly affected those of the conventional 2024 Al alloy. A slight stretch reduces the modulus of Al Li by a small amount.

Elastic Properties of CVD Diamond Via Dynamic Resonance Measurements

ABSTRACTControl of the mechanical properties of CVD diamond is essential to achieve optimal performance in various applications. While several methods have been applied to the measurement of the 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 and shear modulus of free-standing CVD diamond in the shape of rectangular plates or round disks. The specimen is supported along nodal lines of flexural or torsional modes. Oscillations induced by impact from a falling ceramic bead are sensed 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.

Measurements and calculations of the elastic moduli of ODS and cast Ni-based superalloys

For the directionally recrystallized alloys MA 6000 and MA 760 a comparison of measured and calculated elastic moduli was performed. For each material the orientation distribution function (ODF) was determined. Both materials exhibit a strong but different texture. Using the ODF and single-crystal compliances of a similar alloy the elastic moduli were calculated according to the Voigt-Reuss-Hill method between 25 and 1150 °C. The elastic moduli were determined by a dynamic resonance method. Good agreement is found between the measured and the calculated data. The elastic moduli of four different conventionally cast alloys were examined. The comparison of the measured moduli and the values calculated by Kröner's method shows that the two materials MAR-M200 and MAR-M247 LC HIP exhibit nearly isotropic behaviour. For the materials IN 713 LC HIP and IN 738 LC HIP deviations of the measured moduli from the isotropic values are observed. By the simulation of a texture with components of <100> fibre texture adapted to the measured elastic moduli at 25 °C these deviations can be explained and the elastic moduli at higher temperatures can be derived.

Dynamics of phosphatidylcholine-cholesterol mixed model membranes in the liquid crystalline state

The effects of cholesterol on the dynamics of cholestane spin probe (CSL) in various phosphatidylcholine-cholesterol mixed model membranes are examined. The lateral diffusion, D of CSL in DMPC/POPC/cholesterol ternary mixtures, is measured utilizing an improved dynamic imaging electron spin resonance method. It shows a factor of two decrease at 10 mol % and 25 degrees C, whereas it shows only a 40% decrease at 50 mol % and 50 degrees C. A comparison with results in POPC/cholesterol mixtures, which show a stronger effect of cholesterol on D, indicates that acyl chain unsaturation leads to stronger self association of cholesterol in PC model membranes. An S2CSL dependence of the activation energy for D, has been confirmed for the DMPC/POPC/cholesterol mixtures. Here SCSL is the order parameter for CSL. A similar correlation of R perpendicular, the perpendicular component of the rotational diffusion coefficient, with SCSL, which is true for all three mixtures (DMPC/cholesterol, POPC/cholesterol, and DMPC/POPC/cholesterol) we have studied, is also found. These are associated with the effects of enhanced local ordering on the free volume needed for translation and reorientation. Such correlations of dynamic properties D and R perpendicular with the thermodynamic quantity S, as well as the consistent interpretations of the effect of acyl chain unsaturation on the dynamics in terms of the activity coefficients, strongly emphasize the interrelation between the dynamic structure and the thermodynamics of the PC/cholesterol mixtures.

Repulsive gauche conformational effect. Analysis of seven-membered rings containing endo and exo sulfur atoms

The so-called repulsive gauche conformational effect associated with sulfur is investigated through a study of 3-methylthio-1,5-benzodioxepin (1) and 3-methylthio-1-benzoxepin (2), together with 3-fluoro- and 3-chloro-1,5-benzodithiepins (3 and 4), by 13C and 1H dynamic nuclear magnetic resonance methods. The results show that, while compounds 2, 3, and 4 exhibit a large amount of the Ce conformation, the TB form predominates for compound 1. Intramolecular stereoelectronic σ–σ* orbital interactions are analyzed, together with several other factors (steric, electrostatic, and solvation), to explain the observed conformational behaviour. Keywords: gauche effect, seven-membered rings, 1,5-benzodithiepins, variable temperature NMR, orbital interactions.

High-field proton and carbon-13 nuclear magnetic resonance studies of the conformational dynamic properties of seven-membered rings. 1,5-Benzodithiepin and 3-substituted derivatives

The conformational and dynamic properties of 1,5-benzodithiepin (1), its 3,3-dimethyl (2), 3-methyl (3), and 3-methoxy (4) derivatives have been investigated by high-field 1H and 13C dynamic nuclear magnetic resonance methods. Analyses of the spectra at low temperatures indicate that, in CS2, both 1 and 2 exist as a mixture of C and TB forms (97:3 for 1; 63:37 for 2). In contrast, both 3 and 4 exist as a mixture of three equilibrating conformations Ce, Ca, and TB in ratios of 55:25:20 and 88:8:4 respectively. Comparison with analogues derived from 1,5-benzodioxepins (1a–4a) indicates that the replacement of O by S decreases the amount of the TB form for all four compounds studied. The observation that Ce is the most abundant form for 4 while it is not observed for 4a can be explained by a repulsive S/O gauche interaction in 4 compared to an attractive O/O interaction in 4a.

A modified resonance method for determining elastic moduli

This preliminary investigation deals with the correlation of the measured resonance frequencies of cylinders and their elastic properties. By using signals which are generated directly by the materials upon collision in rotating beds of samples, constraints inherent to the usual dynamic resonance methods are eliminated; in particular, concern for the practical limitations to specimen size is eliminated. The availability of modern signal processing equipment provides the means for deriving the elastic moduli of rigid materials with ease, speed, accuracy and precision. Further investigations of this direct method of frequency analysis, on specimens with varying configuration ratios and over an extended frequency range, would seem to provide a significant improvement to existing resonance methods.

Investigation of the formation of gelatin gel structure based on the dynamic shear modulus measured by the resonance method

The dynamic resonance method of measuring the shear modulus G′, the dynamic viscosity η′ and the tangent of the dielectric loss angle (tan δ) has been applied to gelatin gels and to some commercial grade photoemulsions. It has been found possible to observe the kinetics of gel formation and its temperature dependence and the effect of additions of coloured (purple) components and of commercial photoemulsions. Gelatin gels have low dynamic viscosities, but high values of η′ were obtained for the gels containing additions of coloured components.

Temperature dependence of adhesion strength and elasticity of some heat-resistant coatings

Translated from Probl. Prochnosti; 5: No. 1, l15-118(Jan 1973). The dynamic resonance method was used to determine the temperature dependence of the modulus of elasticity of W, Mo, NiCr, and ZrO₂ coatings applied by the plasma spraying method. An increase in test temperature was found to cause a monotonic decrease in the modulus of elasticity. The absolute value of the modulus of elasticity for plasma-sprayed materials is lower than the corresponding value for the same materials applied by other methods (electron- beam melting, arc melting, and powder metallurgy methods). For W and Mo this difference, for example, was 15 to 20% which may be attributed to a difference in porosity, which also depends on coatmg thickness for plasma-sprayed material. It has been noted that the temperature dependence of the modulus of elasticity has two sections with different temperature coefficients. Thus, investigation results showed that the static adhesion strength of the combination base metal-- coating obtained by the method of continuous plasma spraying, depends on the test temperature and coating thickness. It was shown that the modulus of elasticity of coating materials decreases during the temperature rise to 1200 deg C by 25 to 60% thereby affecting the cohesion strength ofmore » the combination. (auth)« less

A systematic investigation of elastic moduli of Wc-Co alloys

Measurements of Young’s modulus, shear modulus, compression modulus, and Poisson’s ratio on WC-(1 ~ 30) wt pct Co alloys were carried out by dynamic resonance method. The effects of volume fraction of the WC phase, the carbon content, and the WC particle-size on the elastic moduli were investigated in some detail. The result shows that the various elastic moduli of the alloys depend solely on volume fractions of the constituent phases and they invariably fall within Hashin and Shtrikman’s bounds. Moreover, the moduli are found to be approximated by Paul’s “strength of materials” type formulas. It is concluded that elastic behavior of the alloys can be essentially predicted on the basis of a simplified geometrical model of WC particles embedded in continuous cobalt matrix.

Relaxation Behavior of Polymers at Low Temperatures

Abstract The relaxation behavior of polymers at low temperatures, as studied by dynamic mechanical, dielectric, and nuclear magnetic resonance methods, is reviewed. Modulus values at 4 and 77°K are tabulated for a variety of both crystalline and amorphous polymers and are compared to room temperature values as well as to theoretical values deduced from intermolecular force constants. Specific attention is given to polymers that show a δ-type relaxation. At low frequencies, this relaxation occurs in the temperature region below 100°K. The δ-processes are shown to arise from reorientational motion of side chain methyl groups, as in PMMA or PVA, side chain ethyl groups, as in PEMA or PVPr, and side chain phenyl or phenyl-substituted groups, as in PS or PmCIS. Linear polymers, such as PE and PTFE, that have no side chain groups exhibit no δ-type relaxation. Consideration is also given to the effect of various internal and external variables on the low-temperature relaxation behavior. These variables include c...

Comparison of Measured and Predicted Bulk Moduli of Tantalum and Tungsten at High Temperatures

The elastic constants of tantalum have been determined from room temperature to 500°C by means of a dynamic resonance method to obtain the adiabatic bulk modulus at elevated temperature. The adiabatic bulk modulus (Bs) of tantalum is found to be 1897 kbar at room temperature and it decreases almost linearly with a slope (dBs/dT) of −0.11 kbar/°C as temperature rises. The calculation of the Grüneisen constant γ and a parameter δ, defined as − (dBs/dT)/αBs, from the present data shows that both parameters are almost independent of the temperature (1.57 for γ and 3.1 for δ). The constancy of γ and δ at high temperatures has also been tested for tungsten by using the recent data of Lowrie and Gonas [J. Appl. Phys. 36, 2189 (1965)]. The results indicate that both γ and δ are virtually constant at high temperature. The applicability of the following equation to estimate the bulk-modulus-temperature relationship for the refractory metals Ta and W has also been tested: BsT=Bs25−(δγ/V)(HT−H25), where H is the enthalpy and the superscripts indicate values at 25° and T°C.

Relaxation phenomena of polyoxymethylene obtained from solid‐state polymerization

AbstractA highly oriented crystal of polyoxymethylene was prepared by solid‐state polymerization of trioxane single crystals. The relaxation phenomena of this sample were investigated by the dynamic viscoelastic and nuclear magnetic resonance methods from −180°C. to the melting point and were compared with those of single crystals obtained from a dilute solution in cyclohexanol and a bulk‐crystallized sample. The β absorption at about −70°C. completely disappeared, and a new absorption peak with a low intensity appeared at about −100°C. at a frequency of 138 cycles/sec. The crystalline absorption at about 150°C. also remarkably decreased in intensity. This viscoelastic behavior was confirmed by the results of a broad line NMR measurement.

The determination of poisson's ratio and the dynamic modulus of elasticity from the frequencies of natural vibration in thick circular plates

By using a dynamic resonance method, the elastic properties of materials can be examined in a non-destructive manner, by measuring the frequencies of natural vibration in test specimens of various shapes. In particular the thick, circular plate is a body which can be examined in this way, and may occur in practice. Practical examples of such plates include samples obtained by core-drilling from concrete slabs and other two-dimensional structures, or from various rocks, or abrasive wheels being checked for quality.

Temperature dependence of the elastic constants of thoria specimens of varying porosity

The temperature dependence of Young's and the shear modulus of 18 thoria specimens of porosities ranging from 3.7 to 39.4 percent was measured by the dynamic resonance method. The temperature range of the measurements was from 25 to 1300 c- C. The moduli decreased with increasing temperature in general accordance with the pattern observed for other polycrystalline materials. The relative decrease in modulus with temperature for all the materials was essentially independent of porosity up to about 800 c- C. Above this temperature the relative decrease in modulus for the high porosity specimens tended to be more rapid than for the low porosity specimens. Also, Poisson's ratio for any particular specimen remained constant over the entire temperature range of measurement. (auth)