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1

Digitale Medien

Subsurface Indentation Damage and Mechanical Characterization of α-Sialon Ceramics (2004)

Xie, Z.-H. ; Hoffman, M. ; Moon, R. J. ; [weitere]

Oxford, UK : Blackwell Publishing Ltd

Journal of the American Ceramic Society 87 (2004), S. 0

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ISSN: 1551-2916

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Maschinenbau , Physik

Notizen: Two hot-pressed sintered α-sialon samples of differing microstructures, but identical chemical composition, were evaluated first, in terms of indentation hardness and modulus, by depth-sensing indentation (DSI) tests on planes parallel and normal to the hot-pressed surface. The surface and subsurface cracks created under the DSI tests have also been investigated in relation to the effect of microstructure. Subsequently, Vickers indentation tests were conducted to explore the deformation and fracture characteristics in the two samples. The effect of microstructure and grain orientation on the development of different types of cracks, in particular subsurface cracks, was revealed and analyzed. Additionally, it suggested that the focused ion beam (FIB) miller is a preferred tool, in comparison to the conventional cross-sectioning techniques, for examining subsurface crack formation and structural characteristics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1151-2916.2004.tb06368.x

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2

Digitale Medien

Densification of zirconia-containing sialon composites by Sm2O3 (1993)

Cheng, Y. -B. ; Thompson, D. P.

Springer

Journal of materials science 28 (1993), S. 3097-3102

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ISSN: 1573-4803

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Notizen: Abstract Sm2O3 was used as an additive for ZrO2/O′-sialon composites and showed remarkably good densification behaviour on sintering. Sm2O3 appeared to behave as a densification rather than a stabilization additive and the low eutectic temperature in this system facilitated densification before zircon dissociation. An important advantage is that the final sintering temperature is then determined by the minimum temperature at which full conversion from α-Si3N4 to O′-sialon can be achieved. At this temperature (1500–1550 °C), grain growth of zirconia is minimal, and this allows control of small grain size for the zirconia particles.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00354716

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3

Digitale Medien

Microstructure and mechanical properties of nanoscale SiC/Ca α-SiAlON composites (1997)

Wang, H ; Cheng, Y.-B ; Muddle, B. C ; [weitere]

Springer

Journal of materials science 32 (1997), S. 3263-3269

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ISSN: 1573-4803

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Notizen: Abstract Ceramic composites comprising nanoscale (less than 200 nm) silicon carbide particles distributed in a matrix of calcium α-SiAlON (α′) have been prepared by uniaxial hot pressing, and the reaction sequence, during densification of a sample containing 20 wt% SiC, has been investigated in the temperature range 1400–1800°C. Samples containing up to 20 wt% SiC were produced to near full density by pressure sintering at temperatures as low as 1600°C for 1 h. For samples with higher SiC contents subjected to a similar treatment, there was residual porosity which was detrimental to the mechanical properties. The SiC was preferentially distributed intergranularly within the α-SiAlON and was effective in controlling grain growth of the α-SiAlON during processing. There was an increase in the uniformity of the grain structure and a significant refinement of the grain size of the composite microstructures with increasing SiC content. The hardness and the three-point bending strength of the composite samples increased markedly with increasing SiC content up to a level of 20 wt%. For a sample containing 20 wt % SiC, the bending strength was about ∼1.5 times that of single-phase α-SiAlON. For samples with higher SiC contents, the rate of increase in hardness was diminished and the bending strength decreased because of incomplete densification. The initial improvement in fracture strength with increasing SiC content is plausibly attributable to the uniform refined grain structure of the composite materials, assuming that the maximum flaw size scales with the grain size.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1018627507245

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4

Digitale Medien

Preparation of fine-grained calcium α-sialon (1994)

Hewett, C. L. ; Cheng, Y. -B. ; Muddle, B. C. ; [weitere]

Springer

Journal of materials science 13 (1994), S. 1612-1615

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ISSN: 1573-4811

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00704517

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5

Digitale Medien

Preferred orientation in hot-pressed Ca α-SiAlON ceramics (1996)

Wang, H. ; Cheng, Y. -B. ; Muddle, B. C. ; [weitere]

Springer

Journal of materials science 15 (1996), S. 1447-1449

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ISSN: 1573-4811

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00275302

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6

Digitale Medien

Automated design and optimization of electromechanical actuators (1996)

Cheng, Y. B. ; Sykulski, J. K.

Chichester [u.a.] : Wiley-Blackwell

International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 9 (1996), S. 59-69

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ISSN: 0894-3370

Schlagwort(e): Engineering ; Electrical and Electronics Engineering

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: The paper investigates various optimization techniques and their suitability for the magnetic design of electromechanical actuators. Selected algorithms, including Gauss-Newton, Levenberg-Marquardt and Trust region, are examined and compared using 18 test functions. The Levenberg-Marquardt method is chosen for its robustness and fast convergence, and incorporated into an automated CAD optimization system (EAMON), which interfaces an external optimizer to a general purpose finite element package. The EAMON program, which is user friendly with pull-down menus, searches for constrained shape design variables that fulfil prescribed performance criteria. The electromagnetic field analysis forms part of the optimization iterative cycle. Finally, two application examples are described. First, a DC solenoid actuator with truncated cone pole face is optimized to produce a user specified force-displacement characteristic. Secondly, an actuator solenoid is optimized to produce maximum energy per stroke.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

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