Download or read book Compressive Strength Hardness and Identification Damage in Ceramic Materials written by James Lankford (Jr) and published by . This book was released on 1982 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hardness and compressive strength of several strong ceramics are measured from room temperature to 1000 C. Similarities in behavior, and the results of microscopic examination, are interpreted in terms of the relative contributions of microplasticity and microfracture to material failure during compression testing and microhardness indentation. It is shown that microplasticity alone is an insufficient basis upon which to relate material response under the two test conditions, and that tensile microfracture is a significant contributor both to compressive failure and to subsurface indentation deformation, hence to hardness. Previous determinations of the strengths of several ceramics subject to impulsive loads were interpreted in terms of a theory based on material inertia. Recent experiments are described, which show that the dynamic strengthening mechanism is athermal, as required by the inertial theory, and that microcrack growth, rather than initiation, is suppressed by the inertial effect. Indentation microfracture measurements in the low load, near threshold regime were carried out using scanning electron microscopy. Results were interpreted in terms of existing theoretical treatments.
Download or read book Compressive Strength and Damage Mechanisms in Ceramic Materials written by James Lankford and published by . This book was released on 1980 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compressive strength measurements as a function of temperature and loading rate, and microhardness measurements as a function of temperature, have been carried out for Al2O3, SiC, and Si3N4. Results are correlated in terms of current theories connecting compressive strength, hardness, fracture toughness, and indentation microfracture. It is found that while high loading rates can suppress high temperature intergranular compressive fracture in SiC, this is not true in Al2O3. The threshold crack size for indentation microfracture as a function of temperature seems to correlate at least as well (if not better) with compressive strength as with hardness, and temperature-controlled compressive fracture mechanisms seem to operate during indentation fracture at corresponding temperatures. (Author).
Download or read book Compressive Strength and Damage Mechanisms in Ceramic Materials I The Role of Subcritical Tensile Microfracture Processes in Compression Failure of Ceramics II Electron Channeling Study of Fracture in Alumina Evidence for Crack Tip Plasticity written by James Lankford and published by . This book was released on 1981 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: The compressive strength of SiC, Si3N4, and Al2O3 is investigated over wide ranges in temperature and loading rate. Several distinct damage regimes are identified, all based upon tensile microfracture processes. Two aspects of the work are of special interest. The first is the identification of a high strain rate regime in which material inertial effects are responsible for unusually rapid strengthening; the basis for the effect is increased difficulty in either crack nucleation or extension. Secondly, it is found that at low loading rates, subcritical tensile microcrack growth is responsible for a thermally activated strength dependence. Selected area electron channeling experiments lead to the conclusion that the thermal activation process may involve crack tip plasticity. (Author).
Download or read book Ceramic Hardness written by I.J. McColm and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the utilization of ceramic materials is developing at a great pace, so too is the science of ceramics improving the understanding we have about these high-technology materials. New and improved ways of examining and investigating monolithic ceramics and ceramic composites are also being developed and reported at a great pace in a wide-ranging area of the scientific and technical literature. This book has been written with the aim of increas ing the awareness of the general materials worker of developments in modern ceramics and of bringing to a focus how much the study of their hardness can contribute to our understanding of them and lead to technical data that can be of considerable use in this fast-growing field. The readership will consist of materials scientists, metallurgists, and engineers moving into the new worlds of advanced ceramics and ceramic-containing composites. Detailed works on hardness are to be found in the metallurgical area, where much of the theory and early applications were developed. This book does not overly stress this early development of theory and practice, but concentrates wherever possible on the ceramics and glasses. Thus Chapter 1 introduces the general subject area to those whose interest may have been blunted in the past by the emphasis on one area of materials. Subjects raised in the first chapter are developed more fully in later chapters.
Download or read book Compressive Strength and Damage Mechanisms in Ceramic Materials I Temperature Strain Rate Dependence of Compressive Strength and Damage Mechanism in Aluminum Oxide II Threshold Microfracture During Elastic Plastic Indentation of Ceramics written by James Lankford and published by . This book was released on 1980 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of compression tests of Al2O3 performed over a wide range in temperature and strain rate are interpreted in terms of dominant damage mechanisms. It is shown that compressive failure in Al2O3 is caused by one of three different mechanisms, each based on tensile (Mode I) growth of predominantly axial microcracks, and each characteristic of a specific temperature-strain rate regime. The concepts developed should be applicable to other strong ceramics. In addition, indentation experiments were carried out for a variety of ceramics. It is found that the threshold for microfracture during elastic-plastic indentation corresponds to radial, rather than subsurface median, crack formation. This is contrary to the fundamental assumption of existing models for threshold crack nucleation by sharp indenters or particles; the results indicate the need to modify the stress field calculations used in these models. (Author).
Download or read book Structural Ceramics and Testing of Brittle Materials written by Samuel J. Acquaviva and published by . This book was released on 1968 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Compressive Strength and Indentation Damage in Ceramic Materials written by James Lankford (Jr) and published by . This book was released on 1978 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: The threshold loads and crack sizes for indentation cracking were investigated for a number of ceramics using scanning electron microscopy and acoustic emission. It was found that the cracking behavior could be predicted, using a fracture mechanics/dimensional analysis approach modified to take into account the stress field at an elastic-plastic indentation. Selected area electron channeling was used to characterize the extent of subsurface damage produced in ceramics during grinding and polishing operations. It was found that polishing damage depths can be correlated using a simple model based on a sliding elastic-plastic indenter. Finally, the effect of temperature and strain rate upon material removal and cracking threshold was analyzed, using recent experimental compressive strength and crack growth measurements as inputs to current predictive models. The results are shown to have surprising implications with regard to dynamic, high temperature indentation (particle impact). (Author).
Download or read book Ceramic Hardness written by Ian McColm and published by Springer. This book was released on 2013-01-12 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the utilization of ceramic materials is developing at a great pace, so too is the science of ceramics improving the understanding we have about these high-technology materials. New and improved ways of examining and investigating monolithic ceramics and ceramic composites are also being developed and reported at a great pace in a wide-ranging area of the scientific and technical literature. This book has been written with the aim of increas ing the awareness of the general materials worker of developments in modern ceramics and of bringing to a focus how much the study of their hardness can contribute to our understanding of them and lead to technical data that can be of considerable use in this fast-growing field. The readership will consist of materials scientists, metallurgists, and engineers moving into the new worlds of advanced ceramics and ceramic-containing composites. Detailed works on hardness are to be found in the metallurgical area, where much of the theory and early applications were developed. This book does not overly stress this early development of theory and practice, but concentrates wherever possible on the ceramics and glasses. Thus Chapter 1 introduces the general subject area to those whose interest may have been blunted in the past by the emphasis on one area of materials. Subjects raised in the first chapter are developed more fully in later chapters.
Download or read book Mechanical Properties of Ceramics written by John B. Wachtman and published by John Wiley & Sons. This book was released on 2009-04-20 with total page 479 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Comprehensive and Self-Contained Treatment of the Theory and Practical Applications of Ceramic Materials When failure occurs in ceramic materials, it is often catastrophic, instantaneous, and total. Now in its Second Edition, this important book arms readers with a thorough and accurate understanding of the causes of these failures and how to design ceramics for failure avoidance. It systematically covers: Stress and strain Types of mechanical behavior Strength of defect-free solids Linear elastic fracture mechanics Measurements of elasticity, strength, and fracture toughness Subcritical crack propagation Toughening mechanisms in ceramics Effects of microstructure on toughness and strength Cyclic fatigue of ceramics Thermal stress and thermal shock in ceramics Fractography Dislocation and plastic deformation in ceramics Creep and superplasticity of ceramics Creep rupture at high temperatures and safe life design Hardness and wear And more While maintaining the first edition's reputation for being an indispensable professional resource, this new edition has been updated with sketches, explanations, figures, tables, summaries, and problem sets to make it more student-friendly as a textbook in undergraduate and graduate courses on the mechanical properties of ceramics.
Download or read book Ceramics written by Dietrich Munz and published by . This book was released on 1999-03-11 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamic Compressive Responses and Flow Behavior of Damaged Ceramics Under High Confinement written by and published by . This book was released on 2005 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We developed a novel dynamic loading/reloading experimental technique modified from a split Hopkinson pressure bar (SHPB) to determine the dynamic properties and to record the damage/failure modes in the ceramic specimen, in which a ceramic specimen was loaded by two consecutive stress pulses. The first pulse determines the dynamic response of the intact ceramic material and then crushes the specimen to a desired damage level. The second pulse then determines the dynamic compressive constitutive behavior of the damaged but still interlocked ceramic specimen. The first pulses were slightly varied to control the damage levels in the ceramic specimen while the second pulse was maintained identical. The damage modes in a hot-pressed silicon carbide (SiC-N) specimen have been correlated to its dynamic compressive response at high strain rates. The results show that the compressive strengths of damaged ceramics depend on a critical level of damage, below which the specimen retains its load-bearing capacity and only axial cracks are observed in the specimen. When the specimen is critically damaged, axial cracks and isolated pulverized regions are observed. When the specimen id damaged beyond the critical level, the ceramic specimen is crushed into cracked particles with pulverized (comminuted) materials along the particle boundaries, which displays a granular flow behavior in its stress-strain curve.
Download or read book Fracture in Ceramic Materials written by A. G. Evans and published by William Andrew. This book was released on 1984 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Contact Damage on the Strength of Ceramic Materials written by S. M. Wiederhorn and published by . This book was released on 1981 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contents: Effect of Contact Damage on the Strength of Ceramic Materials and Effect of Materials Parameters on the Erosion Resistance of Brittle Materials.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 602 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Download or read book Dynamic Testing and Characterization of Pre fractured Ceramic written by and published by . This book was released on 1993 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nearly all of the mechanical behavior studies of armor ceramics, to date, havc involved the characterization and testing of pristine ceramic material. However, balhstic impact causes a strong shock front to propagate rapidly through the ceramic before much penetration can occur. A strong shock wave can result in localized compressive failure and fragmentation of the ceramic before its amplitude is amnuated below the compressive strength of the ceramic. Goals of this effort were to creatc shock-fractured ceramic using test assemblies which maintain the intergranular coupling and high density of the ceramic, characterize the extent and homogeneity of the fragmentation and dilatation of the ceramic, and test the compressive dynamic behavior of the shock-fractured ceramic under conditions of confining pressure. This effort will provide data to support models of the penetration resistance of fractured ceramics including degraded moduli, failure strength-strain, and post-failure characterization of the erosive properties of comminuted ceramic and penetratot materials.
Download or read book Using Plasticity Values Determined From Systematic Hardness Indentation Measurements for Predicting Impact Behavior in Structural Ceramics A New Simple Screening Technique written by and published by . This book was released on 2008 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: In general, it has long been known that the hardness of ceramics correlates with gross impact performance, however, not to a degree useful for materials development. Wilkins, Cline and Honodel, 1969, were the first to point out the apparent importance of ceramic "plasticity" or inelastic deformation mechanisms in BeO and AlN in impact performance. More recently, Lundberg et al., 2000, have made compelling arguments that the compressive yield strength (related to hardness) augmented by the amount of Obstacle Avoidance Obstacle Avoidance "plasticity" in ceramics correlates well to transitional velocities (dwell), i.e. the velocity (or impact pressure) where penetration begins. However, a direct measure of plasticity has not been determined. Hardness comparisons between materials are problematic since the values vary with the applied load, however, the full hardness-load curve can provide much more information on material behavior than hardness alone measured at a single load. In this work, several methods for curve fitting hardness-load data have been compared for both Knoop and Vickers hardness on several ceramic materials: aluminum oxynitride (AlON), silicon carbide, aluminum oxide and boron carbide. A power-law equation (H = kF[exp c]) is shown to fit the Knoop data quite well. A plot of log10 (HK) vs. log10 (F) yielded easily comparable straight lines, whose slope and intercept data might be useful parameters to characterize the materials. It is shown on a series of hot pressed SiC variants that the absolute value of the reciprocal of the slope is a measure of plasticity and that the sum of this value with the calculated Knoop hardness at 1 N is a useful parameter to predict impact transitional velocity.
Download or read book Characterization of Mechanical Damage Mechanisms in Ceramic Composite Materials written by and published by . This book was released on 1988 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-strain rate compressive failure mechanisms in fiber-reinforced ceramic matrix composite materials have been characterized. These are contrasted with composite damage development at low-strain rates, and with the dynamic failure of monolithic ceramics. It is shown that it is possible to derive major strain-rate strengthening benefits if a major fraction of the fiber reinforcement is aligned with the load axis. This effect considerably exceeds the inertial microfracture strengthening observed in monolithic ceramics, and non-aligned composites. Its basis is shown to be the trans-specimen propagation time period for heterogeneously-nucleated, high-strain kink bands. A brief study on zirconia has focussed on the remarkable inverse strength-strain rate result previously observed for both fully and partially-stabilized zirconia single crystals, whereby the strength decreased with increasing strain rate. Based on the hypothesis that the suppression of microplastic flow, hence, local stress relaxation, might be responsible for this behavior, fully stabilized (i.e., non-transformable) specimens were strain-gaged and subjected to compressive microstrain. The rather stunning observation was that the crystals are highly microplastic, exhibiting plastic yield on loading and anelasticity and reverse plasticity upon unloading. These results clearly support the hypothesis that with increasing strain rate, microcracking is favored at the expense of microplasticity. Keywords: Compressive strength; Partially stabilized zirconia; Temperature effects; Composite materials; Fracture mechanisms; Ceramics; Plastic flow; Glass matrix ceramics; Cavitation. (sdw).
