| Simulation of Thermal Stability and Friction: A Lubricant Confined Between Monolayers of Wear Inhibitors on Iron Oxide |
2003 |
7 pages |
| Authors:
Tahir Cagin; Y. Zhou; E. S. Yamaguchi; R. Frazier; A. Ho; CALIFORNIA INST OF TECH PASADENA DIV OF CHEMISTRY AND CHEMICAL ENGINEERING
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 | To understand antiwear phenomena in motor engines at the atomic level and provide evidence in selecting future ashless wear inhibitors, we studied the thermal stability of the self-assembled monolayer (SAM) model for dithiophosphate (DTP) and dithiocarbamate (DTC) molecules on the iron oxide surface using molecular dynamics. The interactions for DTP, DTC and Fe2O3 are evaluated based on a force field derived from fitting to ab initio quantum chemical calculations of ... |
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| Computer Simulation of R-Curve Behaviour in ZrO2-Y2O3 Ceramics |
92 |
|
| Authors:
Y. Zhou; Y. J. Tang; T. C. Lei; HARBIN INST OF TECH (CHINA) DEPT OF METALLIC MATERIAL AND TECHNOLOGY*
|
 | A computer program has been developed which simulates the process of stress-induced phase transformation and micro-cracking in two-phase (t+m) ZrO2- Y2O3 ceramics. The procedure accounts for the complex interactions which occur between a propagation crack, particles produced by stress-induced t-m transformation and the transformation-induced micro-cracks. The transformation of particles and formation of microcracks lead to some changes of the stress field at the crack tip and, as a result, a ... |
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| Grain Growth and Phase Separation of ZrO2-Y2O3 Ceramics Annealed at High Temperature |
92 |
|
| Authors:
Y. Zhou; T. C. Lei; Y. X. Lu; HARBIN INST OF TECH (CHINA) DEPT OF METALLIC MATERIAL AND TECHNOLOGY*
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| The behavior of grain growth and phase separation of sintered ZrO2-2- 8 mol% Y2O3 ceramics annealed at high temperatures were investigated by means of SEM, EPMA, XRD and quantitative metallography. The results show that the grain size increases with increasing Y2O3 content and annealing time. The grain growth is very slow in the single tetragonal phases region and very fast in the single cubic phase region. However, in the c+t ... |
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| Diffusional Cubic-to-Tetragonal Phase Transformation and Microstructural Evolution in ZrO2-Y2O3 Ceramics |
91 |
|
| Authors:
Y. Zhou; Q. L. Ge; T. C. Lei; T. Sakuma; HARBIN INST OF TECH (CHINA) DEPT OF METALLIC MATERIAL AND TECHNOLOGY*
|
| The diffusional cubic-to tetragonal (c-t) phase transformation and microstructural evolution were studied on ZrO2-Y2O3 ceramic with 4 to 6 mol% Y2O3 annealed in the two phase (c + t) region for longer periods of time. It was shown that in early stages of annealing a "tweed" structure of t-ZrO2 was developed. With increasing time this tweed structure becomes coarser and changes into internally twinned "colony" structure. The "colonies" can grow ... |
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| Mechanical Properties and Toughening Mechanism of SiC(w)/Al2O3 Ceramic Composites |
91 |
|
| Authors:
T. C. Lei; W. Z. Zhu; Y. Zhou; HARBIN INST OF TECH (CHINA) DEPT OF METALLIC MATERIAL AND TECHNOLOGY*
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| Microstructure, mechanical properties and toughening mechanisms of hot pressed SiC(w)/Al2O3 ceramic composites were investigated by means of XDR, SEM, TEM, and EPMA. Experimental results show that fracture toughness and Vickers hardness of composites increase with increasing SiC(w) content. With 20 wt% whiskers a fracture toughness of 9 MPa.square root of m was obtained which is nearly twice that of the matrix. Grain size of the matrix has also an influence ... |
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| Microstructure and Mechanical Properties of Hot Pressed Al2O3-ZrO2 Ceramics Prepared from Ultrafine Powders |
91 |
|
| Authors:
Q. L. Ge; T. C. Lei; Y. Zhou; HARBIN INST OF TECH (CHINA) DEPT OF METALLIC MATERIAL AND TECHNOLOGY*
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| Interlayer Selection and Thermal Stresses in Brazed Si3N4-Steel Joints |
91 |
|
| Authors:
Y. Zhou; F. H. Bao; J. L. Ren; T. H. North; TORONTO UNIV (ONTARIO) DEPT OF METALLURGY AND MATERIALS SCIENCE
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| The influence of Cu, Kovar, Mo and W interlayers on the magnitude, distribution of thermal stresses and on the tensile strength of brazed Si3N4- steel joints is examined using finite element modeling (FEM) calculations and direct experiment. The FEM takes into account plastic flow and changes of mechanical properties of the interlayer, the steel substrate, and the filler metal as temperature decreases following the brazing operation. Joints made using low ... |
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| Microstructure and Mechanical Properties of ZrO2-2 mol% Y2O3 Ceramics |
90 |
|
| Authors:
Y. Zhou; Q. L. Ge; T. C. Lei; T. Sakuma; HARBIN INST OF TECH (CHINA) DEPT OF METALLIC MATERIAL AND TECHNOLOGY*
|
| The microstructure and mechanical properties of ZrO2-2 mol% Y2O3 ceramics were studied on samples prepared by cold isostatic pressing and pressureless sintering. It was shown that the density of the alloy increases with increasing sintering temperature. The Vickers hardness decreases the appearance of the monoclinic phase and increasing its content. Compared with the single tetragonal phase, the (t+m) dual-phase structure with microcracks has a much higher fracture toughness because of ... |
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| Effect of Sintering Processes on Microstructure and Properties of Al2O3- ZrO2 Ceramics |
90 |
|
| Authors:
T. C. Lei; Y. Zhou; HARBIN INST OF TECH (CHINA)*
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| Al2O3-ZrO2 ceramics with 10, 15 and 20% ZrO2 were prepared by nonpressure sintering at 1650, 1700 and 1650-1700 C. The microstructure of the specimens was examined by XRD, SEM and EPMA techniques. Density, hardness and dynamic fracture energy were measured. It was shown that with increasing sintering temperature and ZrO2 content the amount of t-ZrO2 decreases. For 1650 C sintered specimens the density is lower and the toughness increases with ... |
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| The Earth Synchronous Satellite Carrier Rocket |
26 JAN 1984 |
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| Authors:
Y. Zhou; FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OH
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| FAST ITERATIVE ALGORITHMS FOR INVERSE SCATTERING SOLUTIONS OF THE HELMHOLTZ AND RICCATI WAVE EQUATIONS |
OCT 83 |
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| Authors:
S. A. Johnson; Y. Zhou; M. K. Tracy; M. J. Berggren; F. Stenger
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| this paper describes further progress in the development of new methods for solving the inverse scattering problem for the helmholtz wave equation. one method demonstrated by the authors is based on solving systems of nonlinear algebraic equations that are derived by applying the method of moments to a sinc basis function expansion of the fields and scattering potential. the new methods are based on fft convolution and the concept of ... |
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| Vibratory Cavitation Tests at 200-kPa (2-Bar) Suppression Pressure |
MAR 83 |
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| Authors:
Y. Zhou; F. G. Hammitt
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| Cavitation erosion of 1100-0 and 2024-T4 aluminum, 1018 carbon steel, 316 stainless steel, and 3% carbon cast iron was measured in tap water by vibratory horn at 200-kPa (2-bar) suppression pressure, at various temperatures and amplitudes. Erosion rate (MDPR) and incubation period (IP) were computed according both to total specimen area and to actual area eroded. Maximum damage depth penetration rate D(sub m)PR was also measured. Actual eroded area and ... |
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| Least-Squares Reconstruction of Spatially Limited Objects Using Smoothness and Non-Negativity Constraints. |
APR 1982 |
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| Authors:
Y. Zhou; C. K. Rushforth; UTAH UNIV SALT LAKE CITY DEPT OF ELECTRICAL ENGINEERING
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| This paper describes an approach to reconstructing an optical object which has been subjected to low pass spatial-frequency filtering. The object is assumed to be of limited and known spatial extent and is further known to be non-negative and reasonably smooth. The smoothness constraint is incorporated into a regularizing matrix in a novel way. This matrix defines a regularized version of the original imaging equation, which is then solved using ... |
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