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1993

Ceramic Materials

Keyword

Articles 1 - 13 of 13

Full-Text Articles in Mechanical Engineering

Performance Characteristics Of Piezocomposite Bulk Wave Transducers, J. Hossack, B. A. Auld Jan 1993

Performance Characteristics Of Piezocomposite Bulk Wave Transducers, J. Hossack, B. A. Auld

Review of Progress in Quantitative Nondestructive Evaluation

Piezoelectric ceramic/ polymer composite materials, possessing useful characteristics unobtainable in single phase materials, have been widely investigated over the past ten years. [1]. Their superior matching to low impedance media has been recognized by manufacturers of medical ultrasound and sonar equipment. However, so far as we know, they have received little attention in the field of non-destructive examination. It is evident that they offer superior performance for the inspection of low impedance media; including concrete, wood, fiber reinforced resin composites etc. A review of the types of composite available is presented together with results indicating achievable performance.


Real-Time Ultrasonic Investigation Of Fiber-Matrix Debonding In Ceramic-Matrix Composite, Shi-Chang Wooh, Isaac M. Daniel Jan 1993

Real-Time Ultrasonic Investigation Of Fiber-Matrix Debonding In Ceramic-Matrix Composite, Shi-Chang Wooh, Isaac M. Daniel

Review of Progress in Quantitative Nondestructive Evaluation

Limitations of ceramic materials such as brittleness, low tensile strength and low fracture toughness are being overcome with the introduction of ceramic matrix composites. The mechanical behavior of these fiber-reinforced composites strongly depends on the fiber-matrix bonding condition. If the bonding is too weak, there is poor stress transfer. On the other hand, for a case of very strong bond, the material behaves in a brittle fashion. Recently, photomicroscopic observations were made and the macroscopic behavior of the material was related to the failure mechanisms and damage development under loading [1]. However, this method is destructive, limited to damage on ...


Ultrasonic Assessment Of Microcrack Damage In Ceramics, Y. C. Chu, M. Hefetz, S. I. Rokhlin Jan 1993

Ultrasonic Assessment Of Microcrack Damage In Ceramics, Y. C. Chu, M. Hefetz, S. I. Rokhlin

Review of Progress in Quantitative Nondestructive Evaluation

The inherent brittleness of ceramics often results in catastrophic failure due to microcrack damage caused by thermal treatment or mechanical loading. Extensive theoretical and experimental studies have been performed to analyze microcrack damage in ceramics caused by thermal shock [1–7]. Hasselman [1,2] proposed a simple model describing the strength behavior of ceramic materials as a function of thermal shock temperature difference ΔT. The important characteristic parameter in this model is the critical temperature difference, ΔT c . For thermal shock temperature differences less than ΔT c (stage I, Fig. 1) ceramics retain their strength. Thermal shocks with temperature differences ...


Effects Of Acoustic Scattering At Rough Surfaces On The Sensitivity Of Ultrasonic Inspection, Peter B. Nagy, Laszlo Adler, James H. Rose Jan 1993

Effects Of Acoustic Scattering At Rough Surfaces On The Sensitivity Of Ultrasonic Inspection, Peter B. Nagy, Laszlo Adler, James H. Rose

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic inspection of ordinary samples with more or less rough surfaces is an everyday problem in industrial NDE. Contact techniques require flat or other regular (e. g., cylindrical) surfaces of negligible roughness with respect to the acoustic wavelength. Immersion techniques are less susceptible to surface topography, but they still require that the surface radius be larger than the beam diameter and the surface roughness be comparable or less than the wavelength in the immersion fluid. This difference is due to the fact that in immersion inspection surface irregularities do not significantly reduce the energy transmission into the specimen but rather ...


Acoustic Microscopy Measurements To Correlate Surface Wave Velocity And Surface Roughness, Y. C. Lee, Jan D. Achenbach, Jin O. Kim Jan 1993

Acoustic Microscopy Measurements To Correlate Surface Wave Velocity And Surface Roughness, Y. C. Lee, Jan D. Achenbach, Jin O. Kim

Review of Progress in Quantitative Nondestructive Evaluation

Acoustic microscopy can be used for very localized measurements of the velocity and attenuation of surface waves, and hence is a possible technique for nondestructive evaluation of near surface damage due to fatigue, machining, friction, wear, etc. Because the frequency of operation of an acoustic microscope is high, usually above 100 MHz, the wavelength of the surface wave is relatively small, and thus the roughness of the specimen may affect the wave velocity. In most cases the specimens must be polished to a metallurgical level to ensure that the true Rayleigh wave velocity, i.e., the one for a smooth ...


Ultrasonic Sensing Simulation Of Cdte Single Crystal Growth, Yichi Lu, Haydn N. G. Wadley Jan 1993

Ultrasonic Sensing Simulation Of Cdte Single Crystal Growth, Yichi Lu, Haydn N. G. Wadley

Review of Progress in Quantitative Nondestructive Evaluation

Today’s infrared detector arrays consist of Hg1-xCdxTe deposited upon lattice matched Cd1-xZnxTe substrate wafers. Very high quality Cd1-xZnxTe crystals must be grown so that substrate wafer defects do not degrade the detector’s performance. Usually, the Cd1-xZnxTe crystals are grown by a Bridgman technique in which a charge is melted in a cylindrical quartz ampoule and slowly withdrawn from the hot zone (at ~ 1100°C) of a furnace.1 The best quality crystal is obtained from material solidified under plane front conditions.2 This is difficult to achieve, and a need has arisen for insitu sensing of the growth ...


Monte-Carlo Simulation Of Ultrasonic Grain Noise, I. Yalda-Mooshabad, Frank J. Margetan, R. Bruce Thompson Jan 1993

Monte-Carlo Simulation Of Ultrasonic Grain Noise, I. Yalda-Mooshabad, Frank J. Margetan, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

In ultrasonic inspections for small or subtle defects in metals, defect signals may be obscured by grain noise echoes which arise from the scattering of sound by the microstructure of the metal. Models for predicting microstructural noise levels are consequently essential for accurately assessing the reliability of the ultrasonic inspections. Existing noise models, like the independent scatterer model (ISM) [1], are capable of predicting only average noise characteristics, such as the root-mean-square (rms) noise level. Average noise levels, although useful, are not sufficient for assessing detection reliability. One needs to know the manner in which noise signals are distributed about ...


Modeling Ultrasonic Microstructural Noise In Titanium Alloys, Frank J. Margetan, R. Bruce Thompson, I. Yalda-Mooshabad Jan 1993

Modeling Ultrasonic Microstructural Noise In Titanium Alloys, Frank J. Margetan, R. Bruce Thompson, I. Yalda-Mooshabad

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic echoes from small or subtle defects in metals may be masked by competing “noise” echoes which arise from the scattering of sound by grains or other microstructural elements. Algorithms for estimating the detectability of such defects consequently require quantitative models for microstructural noise. In previous work [1,2] we introduced an approximate noise model for normal-incidence immersion inspections using tone-burst pulses, and we used the model to estimate signal/noise ratios for brittle (hard-alpha) inclusions in titanium alloys. In the present work we consider an extension of that noise model to inspections using broadband incident pulses. Like its predecessor ...


Relationships Between Ultrasonic Noise And Macrostructure Of Titanium Alloys, K. Y. Han, R. Bruce Thompson, Frank J. Margetan, James H. Rose Jan 1993

Relationships Between Ultrasonic Noise And Macrostructure Of Titanium Alloys, K. Y. Han, R. Bruce Thompson, Frank J. Margetan, James H. Rose

Review of Progress in Quantitative Nondestructive Evaluation

The complex microstructure of two-phase titanium alloys can produce considerable ultrasonic backscattering noise. The noise introduces problems in detecting small flaws, such as hard-alpha inclusions, by forming a background which can mask the flaw signals. Therefore better understanding of grain noise is required to quantify and increase the detectability of the small flaws. As an aid to understanding the grain noise, an independent scattering model was constructed and studied during last two years by Margetan and Thompson. In that model for the backscattered noise generated by a tone burst, the grain noise is described by following equation (1) N(t ...


Experimental Study Of Thermal Oxidation Damage In Ceramic Composites Using Ultrasonic Waves, Y.-C. Chu, S. I. Rokhlin, G. Y. Baaklini, Ramakrishna Bhatt Jan 1993

Experimental Study Of Thermal Oxidation Damage In Ceramic Composites Using Ultrasonic Waves, Y.-C. Chu, S. I. Rokhlin, G. Y. Baaklini, Ramakrishna Bhatt

Review of Progress in Quantitative Nondestructive Evaluation

One major concern about ceramic matrix composites (CMC) is their high temperature stability, especially in an oxidizing environment. In general CMC materials are composed of matrix, fiber, and interphase layers (mainly fiber coatings and/or reaction product layers). It is known [1,2] that the properties of CMC materials are dominated by the interphase. However, this interphase often suffers from oxidation reactions caused by diffusion of oxygen through the matrix [1,3]. As a result desirable properties are not retained.


Ultrasonic Characterization Of Fiber-Matrix Interphasial Properties In Ceramic Matrix Composites, Y.-C. Chu, S. I. Rokhlin Jan 1993

Ultrasonic Characterization Of Fiber-Matrix Interphasial Properties In Ceramic Matrix Composites, Y.-C. Chu, S. I. Rokhlin

Review of Progress in Quantitative Nondestructive Evaluation

The major role of the fiber-matrix interphase in ceramic matrix composites (CMC) is to increase the composite fracture resistance; thus the properties of these materials are dominated by the interphase. To achieve this, the interphase is designed to provide friction sliding contact between fiber and matrix, which prevents fracture of fibers due to matrix cracking [1,2]. Due to the relatively low stiffness of the fiber-matrix interphase compared to fiber and matrix, the interphase also has a dominant effect on the transverse and shear stiffnesses of CMC materials [3]. Therefore, to obtain optimal performance in CMC materials quantitative characterization of ...


Ultrasonic Inspection, Material Noise And Surface Roughness, Mehmet Bilgen, James H. Rose, Peter B. Nagy Jan 1993

Ultrasonic Inspection, Material Noise And Surface Roughness, Mehmet Bilgen, James H. Rose, Peter B. Nagy

Review of Progress in Quantitative Nondestructive Evaluation

The ultrasonic detection of subsurface flaws, such as cracks or voids, may be greatly degraded by the presence of rough surfaces [1,2]. The loss of signal-to-noise arises for three reasons. First, the randomization of the phase of the wave by the roughness may reduce the phase coherent signal from the flaw. Second, additional noise is generated directly by the reflection of the incident beam by the rough surface. Finally, the material noise is modified.


Theory Of Ultrasonic Backscatter From Multiphase Polycrystalline Solids, James H. Rose Jan 1993

Theory Of Ultrasonic Backscatter From Multiphase Polycrystalline Solids, James H. Rose

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasound scatters from the microscopic single crystals that constitute polycrystalline solids. The scattering originates from crystallite-crystallite variations in the density and elastic constants. For single-phase materials, each crystallite has the same density and the same crystalline symmetry. Hence, in single-phase materials scattering arises from the variation in velocity, which in turn is due to the anisotropy of the elastic constants and the more or less random orientation of the crystallites [1,2]. The situation is considerably more complicated in multiphase alloys where the density, the crystal symmetry and the elastic constants vary from crystallite to crystallite.