Indentation Crack Initiation and Ductile to Brittle Transition Behavior of Fused Silica

To provide a fundamental knowledge for the high efficiency grinding and ultra-precision grinding of fused silica, ductile mode and brittle mode material removal mechanisms were investigated by conducting micro/nanoindentation experiments in the range of 4.9 mN - 1960 mN. Before observing cracks and determining the ductile to brittle transition penetration depth, the samples were etched with hydrofluoric acid to expose cracks. The typical damage morphology of fused silica was discussed by observing the surface and cross-section of indentations, and the depth of SSD was found to be determined by the cone cracks or borderline cracks in the different load range. The ductile to brittle transition penetration depth of fused silica under Vickers indentation was 180 nm.

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Ductile and Brittle Mode Grinding of Fused Silica

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.447-448.21 ◽

2010 ◽

Vol 447-448 ◽

pp. 21-25 ◽

Cited By ~ 9

Author(s):

Peng Yao ◽

Nobuhito Yoshihara ◽

Nobuteru Hitomi ◽

Ji Wang Yan ◽

Tsunemoto Kuriyagawa

Keyword(s):

Surface Integrity ◽

High Efficiency ◽

High Surface ◽

Ground Surface ◽

Fused Silica ◽

Wheel Speed ◽

Depth Of Cut ◽

Creep Feed ◽

Ductile Mode ◽

Brittle Mode

There is a demand for high-efficiency and high surface integrity grinding of fused silica. Ductile grinding is an ideal method for producing a mirror finished surface on hard and brittle materials to significantly decrease polishing time. However, the fused silica is still difficult to ductile grind because of its high brittleness. A creep feed taper grinding method was applied to investigate the relationship between maximum grit depth of cut and surface integrity of fused silica. Ductile mode grinding was achieved on fused silica. When the depth of cut exceeds the critical wheel depth of cut, the surface suddenly changes from the ductile mode to the brittle mode. At the same ratio of wheel speed and table speed, the critical wheel depth of cut is noticeably increased by increasing the wheel speed which caused an increase in the temperature at the interface of grains and workpiece. The depth of subsurface damage (SSD) was investigated by polishing the ground surface. The experiment results show that the depth of SSD is deepest in transition mode and stables in brittle mode.

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Thermal Analysis of Laser Irradiation of Fused Silica

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.314-316.1960 ◽

2011 ◽

Vol 314-316 ◽

pp. 1960-1964 ◽

Cited By ~ 1

Author(s):

Peng Yao ◽

Ya Dong Gong ◽

Suo Xian Yuan ◽

Tian Feng Zhou ◽

Ji Wang Yan ◽

...

Keyword(s):

Thermal Analysis ◽

Surface Roughness ◽

Laser Irradiation ◽

Fused Silica ◽

Maximum Temperature ◽

Precision Grinding ◽

Micro Cracks ◽

Ductile Mode ◽

Ultra Precision ◽

Simulation Results

To grind fused silica in ductile mode, surface and subsurface micro cracks (SSMC) on ground fused silica should be repaired by CO2 laser irradiation before ultra-precision grinding. In this paper, 2D thermal analysis of single pass laser irradiation of fused silica was conducted, and the simulation results were discussed by comparing with the experiment results. To repair SSMC and decrease the surface roughness of ground fused silica simultaneously, the maximum temperature on the surface during laser irradiation should be controlled higher than 3280 K and lower than 3550 K.

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Thermal Analysis of Multi-Pass Laser Irradiation on Fused Silica

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.565.621 ◽

2012 ◽

Vol 565 ◽

pp. 621-626

Author(s):

Peng Yao ◽

Chuan Zhen Huang ◽

Jun Wang ◽

Tunemoto Kuriyagawa

Keyword(s):

Thermal Analysis ◽

Laser Irradiation ◽

Silica Surface ◽

Fused Silica ◽

Precision Grinding ◽

Micro Cracks ◽

Ductile Mode ◽

Raster Scan ◽

Ultra Precision ◽

Simulation Results

A rough ground fused silica surface can be ground in a ductile mode by ultra-precision grinding after repairing the surface and subsurface micro cracks (SSMC) by CO2 laser irradiation. In this paper, 2D finite element thermal analysis of unidirectional multi-pass laser irradiation on fused silica was conducted, and the simulation results were compared with the thermal analysis and experiments results of single pass laser irradiation. Thermal analysis results show that the SSMC on the ground fused silica can be repaired and surface roughness can be decreased simultaneously by unidirectinal laser raster scan with a power of 10.5 W, a scan velocity of 0.2 m/s and a scan spacing of 40 μm.

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ZVS Auxiliary Circuit for a 10 kW Unregulated LLC Full-Bridge Operating at Resonant Frequency for Aircraft Application

Energies ◽

10.3390/en12101850 ◽

2019 ◽

Vol 12 (10) ◽

pp. 1850 ◽

Cited By ~ 1

Author(s):

Yann E. Bouvier ◽

Diego Serrano ◽

Uroš Borović ◽

Gonzalo Moreno ◽

Miroslav Vasić ◽

...

Keyword(s):

Resonant Frequency ◽

Power Density ◽

High Efficiency ◽

Harmonic Approximation ◽

Maximum Efficiency ◽

Voltage Gain ◽

Load Range ◽

Transition Analysis ◽

Aircraft Application ◽

Auxiliary Circuit

In modern aircraft designs, following the More Electrical Aircraft (MEA) philosophy, there is a growing need for new high-power converters. In this context, innovative solutions to provide high efficiency and power density are required. This paper proposes an unregulated LLC full-bridge operating at resonant frequency to obtain a constant gain at all loads. The first harmonic approximation (FHA) model is not accurate enough to estimate the voltage gain in converters with high parasitic resistance. A modified FHA model is proposed for voltage gain analysis, and time-based models are used to calculate the instantaneous current required for the ZVS transition analysis. A method using charge instead of current is proposed and used for this ZVS analysis. Using this method, an auxiliary circuit is proposed to achieve complete ZVS within the whole load range, avoiding a gapped transformer design and increasing the efficiency and power density. A 28 Vdc output voltage prototype, with 10 kW peak output power, has been developed to validate the theoretical analysis and the proposed auxiliary circuit. The maximum efficiency (96.3%) is achieved at the nominal power of 5 kW.

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The ductile-to-brittle transition and ductile failure envelopes of orthotropic ice under biaxial compression

Acta Metallurgica et Materialia ◽

10.1016/0956-7151(95)90149-3 ◽

1995 ◽

Vol 43 (10) ◽

pp. 3661-3668 ◽

Cited By ~ 37

Author(s):

E.M. Schulson ◽

S.E. Buck

Keyword(s):

Ductile Failure ◽

Biaxial Compression ◽

Brittle Transition ◽

Failure Envelopes ◽

Ductile To Brittle Transition

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Size dependence of ductile to brittle transition of Zr-based metallic glasses under multiaxial loading

Journal of Materials Research and Technology ◽

10.1016/j.jmrt.2021.07.002 ◽

2021 ◽

Author(s):

Xiangkui Liu ◽

Jian Kong ◽

Xinxiang Song ◽

Shuai Feng ◽

Qipeng Wang ◽

...

Keyword(s):

Metallic Glasses ◽

Size Dependence ◽

Multiaxial Loading ◽

Brittle Transition ◽

Ductile To Brittle Transition

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The nucleation of the Izmit and Düzce earthquakes: Some mechanical logic on where and how ruptures began

Geophysical Journal International ◽

10.1093/gji/ggab040 ◽

2021 ◽

Author(s):

Michel Bouchon ◽

Hayrullah Karabulut ◽

Mustafa Aktar ◽

Serdar Özalaybey ◽

Jean Schmittbuhl ◽

...

Keyword(s):

Strike Slip ◽

Seismic Events ◽

Fault Geometry ◽

Brittle Transition ◽

The North ◽

Impending Rupture ◽

Natural Tendency ◽

Ductile To Brittle Transition ◽

Mechanical Logic ◽

Rupture Speed

Summary In spite of growing evidence that many earthquakes are preceded by increased seismic activity, the nature of this activity is still poorly understood. Is it the result of a mostly random process related to the natural tendency of seismic events to cluster in time and space, in which case there is little hope to ever predict earthquakes? Or is it the sign that a physical process that will lead to the impending rupture has begun, in which case we should attempt to identify this process. With this aim we take a further look at the nucleation of two of the best recorded and documented strike-slip earthquakes to date, the 1999 Izmit and Düzce earthquakes which ruptured the North Anatolian Fault over ∼200 km. We show the existence of a remarkable mechanical logic linking together nucleation characteristics, stress loading, fault geometry and rupture speed. In both earthquakes the observations point to slow aseismic slip occurring near the ductile-to-brittle transition zone as the motor of their nucleation.

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