Journal ArticleDOI
A Fracture‐Mechanics Study of ZnSe for Laser Window Applications
A. G. Evans,H. Johnson +1 more
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Fracture-mechanics studies of chemically vapor-deposited ZnSe show that this material has a low fracture toughness and is susceptible to water-dependent slow crack growth as mentioned in this paper.Abstract:
Fracture-mechanics studies of chemically vapor-deposited ZnSe show that this material has a low fracture toughness and is susceptible to water-(moisture-) dependent slow crack growth. Investigations of biaxial flexural strength indicate that fracture (in this configuration) is controlled primarily by surface flaws and that macrofracture mechanics adequately describe the propagation of typical preexisting flaws in this ZnSe. Crack growth can be detected consistently by the acoustic emission technique; fracture in air is preceded by precursor events which occur up to 2 s prior to catastrophic propagation. Failure diagrams generated from the slow-crack-growth parameters show that the lifetime requirements of the laser window can be achieved by overload proof-testing to a proof ratio of 1.35 when the proper proof-test precautions are implemented.read more
Citations
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Quasi-static solid particle damage in brittle solids—I. Observations analysis and implications
Anthony G. Evans,T.R. Wilshaw +1 more
TL;DR: In this paper, an approximate stress analysis has indicated the importance of both the impression radius and the ratio of the hardness to the fracture toughness in the development of the observed fractures, which has been used to examine several important consequences of indentation fracture.
Journal ArticleDOI
Room temperature Young's modulus, shear modulus, Poisson's ratio and hardness of PbTe–PbS thermoelectric materials
Jennifer E. Ni,Eldon D. Case,Kristen N. Khabir,Ryan C. Stewart,Chun I. Wu,Timothy P. Hogan,Edward J. Timm,Steven N. Girard,Mercouri G. Kanatzidis +8 more
TL;DR: In this paper, a Vickers indentation mean hardness of 1.18 ± 0.09 GPa was measured for hot pressed specimens Pb 0.95 Sn 0.05 Te-PbS 8% while the mean hardness for cast specimens was 0.68± 0.0 GPa.
Journal ArticleDOI
Probing the Soft and Nanoductile Mechanical Nature of Single and Polycrystalline Organic–Inorganic Hybrid Perovskites for Flexible Functional Devices
TL;DR: In this article, the authors predict the elastic constant matrix and various elastic properties of CH3NH3PbI3 using atomistic simulations, and they find that single-crystalline MAPbI-3 is much stiffer and exhibits higher ultimate tensile strength than poly-crystaline samples, but the latter exhibit unexpected, greatly enhanced nanoductility and fracture toughness, resulting from extensive amorphization during the yielding process.
Journal ArticleDOI
Infra-red transmitting materials
I. W. Donald,P. W. McMillan +1 more
TL;DR: In this paper, a review of inorganic glasses suitable for application in the 1 to 6μm spectral range are reviewed with reference to existing materials and fabrication techniques, and problems associated with water absorption which may limit the useful transmission of many glasses can be minimized by such techniques as vacuum melting.
Journal ArticleDOI
Influence of Microstructure on Crack Propagation in ZnSe
TL;DR: The rate of crack propagation as a function of the stress intensity factor, K1, for chemically vapor-deposited (CVD) ZnSe was significantly larger in H2O than in air as mentioned in this paper.
References
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Journal ArticleDOI
Proof testing of ceramic materials—an analytical basis for failure prediction
TL;DR: In this article, an analysis is presented which permits the accurate prediction of component lifetimes after proof testing, which applies to crack propagation controlled fracture but can be used as a conservative prediction when crack initiation is predominant.
Journal ArticleDOI
Failure Prediction in Structural Ceramics Using Acoustic Emission
A. G. Evans,M. Linzer +1 more
TL;DR: In this paper, two types of acoustic emission are detected: slow growth of the fracture-initiating flaw; the emission rate depends primarily on crack velocity; and cracking associated with second-phase particles, as a result of the combined action of the applied stress and local thermal and mechanical stresses.
Journal ArticleDOI
Acoustic emission and crack propagation in polycrystalline alumina
TL;DR: In this paper, the authors measured acoustic emission during the fracture of polycrystalline alumina and showed that acoustic emission is obtained during macrocrack growth, which can be used for failure indication.
Journal ArticleDOI
Thermal fracture studies in ceramic systems using an acoustic emission technique
TL;DR: In this article, an acoustic emission technique for measuring the failure time in thermal shock experiments is described, which offers a unique opportunity to measure the heat-transfer coefficient of the test system and hence, to obtain a fully quantitative measure of the peak surface stress generated during the test.
Thermal Electrical, and Physical Property Measurements of Laser Window Materials
John C Wurst,Thomas P Graham +1 more
TL;DR: In this paper, various II-VI and alkali halide compounds were subjected to a comprehensive evaluation to determine their relative effectiveness in a CO2 laser window application, focusing on the thermal, electrical, mechanical, and physical properties which must be considered in the design of a practical window configuration.