On Crack Control Strategy in Near-Field Microwave Drilling of Soda Lime Glass Using Precursors

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Nitin Kumar Lautre ◽  
Apurbba Kumar Sharma ◽  
Shantanu Das ◽  
Pradeep Kumar
Keyword(s):  
Thermal Stresses ◽  
Near Field ◽  
Flow Characteristics ◽  
Soda Lime ◽  
Power Input ◽  
Local Heat ◽  
High Heat ◽  
Soda Lime Glass ◽  
High Heat Flux ◽  
Cracking Behavior

Processing of glass is indeed challenging owing to its chemical passivity; it is prone to cracking while processing through mechanical and thermal modes without appropriate strategies. Near-field microwave drilling is a thermal-ablation based material removal technique of generating high heat flux in the targeted area. Glasses tend to fail quite frequently during this processing owing to thermal stresses (shock). It was therefore important to develop suitable strategies to minimize cracking during this potentially pragmatic process for microdrilling. Accordingly, in the present work, an attempt was made to change the medium of the interface at the target drilling zone through application of seven different surface precursors to influence the local heat-flow characteristics. The cracking behavior of the soda lime glass during microwave drilling in a customized applicator under controlled power input (90–900 W) at 2.45 GHz was investigated. The heat was generated inside the applicator by creating a plasma sphere in the drilling zone through a metallic concentrator. The thermal shock on the glass specimen was found reduced by the combination of a good dielectric precursor and microwave concentration for hotspot formation, which in turn, reduces the cracking/crazing tendency. Trials were carried out while drilling holes on 1.2 mm thick glass plates at various duty cycles (DCs) to study the crack intensity and pattern. The near-field microwave drilling condition was also simulated to obtain the contours of the induced stresses. The results so obtained were compared with the cracking signatures of the experimental outputs; a good correlation could be obtained. It was found that both solid and liquid fluxes as precursor could be effective to control cracking during microwave drilling.

Thermo-Fluid-Stress-Deformation Analysis of Two-Layer Microchannels for Cooling Chips With Hot Spots

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Abas Abdoli ◽  
George S. Dulikravich ◽  
Genesis Vasquez ◽  
Siavash Rastkar
Keyword(s):  
Heat Flux ◽  
Thermal Stresses ◽  
Hot Spot ◽  
Heat Removal ◽  
High Heat ◽  
Heat Transfer Analysis ◽  
Deformation Analysis ◽  
High Heat Flux ◽  
Cooling Design ◽  
Microchannel Cooling

Two-layer single phase flow microchannels were studied for cooling of electronic chips with a hot spot. A chip with 2.45 × 2.45 mm footprint and a hot spot of 0.5 × 0.5 mm in its center was studied in this research. Two different cases were simulated in which heat fluxes of 1500 W cm−2 and 2000 W cm−2 were applied at the hot spot. Heat flux of 1000 W cm−2 was applied on the rest of the chip. Each microchannel layer had 20 channels with an aspect ratio of 4:1. Direction of the second microchannel layer was rotated 90 deg with respect to the first layer. Fully three-dimensional (3D) conjugate heat transfer analysis was performed to study the heat removal capacity of the proposed two-layer microchannel cooling design for high heat flux chips. In the next step, a linear stress analysis was performed to investigate the effects of thermal stresses applied to the microchannel cooling design due to variations of temperature field. Results showed that two-layer microchannel configuration was capable of removing heat from high heat flux chips with a hot spot.

Numerical Investigation of Thermofluid Flow Characteristics With Phase Change Against High Heat Flux in Porous Media

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Kazuhisa Yuki ◽  
Jun Abei ◽  
Hidetoshi Hashizume ◽  
Saburo Toda
Keyword(s):  
Heat Flux ◽  
Solid Phase ◽  
Flow Characteristics ◽  
High Heat ◽  
High Heat Flux ◽  
Phase Flow ◽  
Two Phase ◽  
Thermal Nonequilibrium ◽  
Phase Mixture ◽  
Flow Case

This study numerically evaluates thermofluid flow characteristics in porous medium by a newly developed “modified two-phase mixture model” applying Ergun’s law and a two-energy model instead of a one-energy model. In a single-phase flow case, thermal nonequilibrium between a solid phase and a fluid phase is observed in the area where imposed heat conducts from a heating wall and further convective heat transfer is more active. The degree of thermal nonequilibrium has a positive correlation with the increase in flow velocity and heat flux input. In the case of two-phase flow, the thermal nonequilibrium is remarkable in the two-phase region because the solid-phase temperature in this region is far beyond saturation temperature. A difference between these two models is obvious especially in the two-phase flow case, so that the numerical simulation with the modified two-phase mixture model is indispensable under the high heat flux conditions of over 1MW∕m2.

scholarly journals Evaluation of Sinking-In and Cracking Behavior of Soda-Lime Glass under Varying Angle of Trigonal Pyramid Indenter

2016 ◽  
Vol 3 ◽  
Author(s):  
Satoshi Yoshida ◽  
Ken Wada ◽  
Takahiro Fujimura ◽  
Akihiro Yamada ◽  
Mitsuo Kato ◽  
...  
Keyword(s):  
Soda Lime ◽  
Soda Lime Glass ◽  
Cracking Behavior ◽  
Trigonal Pyramid

scholarly journals Solar Cooker Glass Failure Analysis

2009 ◽  
Vol 4 (2) ◽  
pp. 20-33
Author(s):  
Peter Kolis ◽  
Margaret Pinnell
Keyword(s):  
Thermal Stresses ◽  
Cutting Tools ◽  
Soda Lime ◽  
Fracture Pattern ◽  
Soda Lime Glass ◽  
Cause Of Failure ◽  
Glass Panels ◽  
Glass Cutting ◽  
Cutting Processes ◽  
Tools And Methods

The failure of a pane of glass from a solar box cooker made and used in Sabana Grande, Nicaragua, was analyzed to determine the cause of failure and to recommend possible solutions. Background research into solar box cookers, the environment in which the failure occurred, characteristics of glass and wood, methods of fractography, and glass cutting tools and methods was carried out. The type of glass used in the solar cooker was unknown, so the observable physical properties, an energy dispersive spectroscopic scan, and thermal analysis of the glass were used to identify the glass as soda-lime glass. The properties of the glass, the conditions of use, and an analysis of the fracture pattern and fracture surfaces were used to determine that the glass had been weakened by cutting processes and that the fracture occurred as a result of thermal stresses. Several recommendations were presented including altering the design of the solar cooker to provide more clearance for the glass panels, incorporating the use of improved glass cutting techniques and sanding the edges of the glass.

Fracture Strength of Laser Etched Glass

2011 ◽  
Author(s):  
Joshua D. Browne ◽  
Ronald A. L. Rorrer
Keyword(s):  
Fracture Strength ◽  
Thermal Stresses ◽  
Failure Process ◽  
Soda Lime ◽  
Soda Lime Glass ◽  
Stress Concentrations ◽  
Laser Etching ◽  
Laser Ablation Process ◽  
Nominal Strength ◽  
Point Bend

The effect of CO2 laser etching on the strength of soda lime plate glass has been investigated. The majority of common beverage glassware is comprised of soda lime glass. Laser etching is used to create patterns on such glassware for aesthetic reasons. Various etching conditions have been investigated in order to compare to the strength of un-etched glass. Three point bend tests were used to determine strength values. The resulting fracture strength of etched glass is based upon the flaws and resulting stress concentrations created during the laser ablation process. In addition to stress concentrations, the thermal history and residual thermal stresses play a role in the failure process. Samples were also cyclically washed to determine the effect of water and thermal cycling. Results were documented and compared via Weibull analysis. Nominal strength values were 114 MPA for unetched, 83 MPa for wash cycled, 43 MPa for etched, and 33 MPa for etched and wash cycled.

Non-Fourier Effects at High Heat Flux

1973 ◽  
Vol 95 (2) ◽  
pp. 284-286 ◽  
Author(s):  
M. J. Maurer ◽  
H. A. Thompson
Keyword(s):  
Heat Flux ◽  
Surface Heat Flux ◽  
Thermal Stresses ◽  
High Heat ◽  
Step Change ◽  
Surface Heat ◽  
High Heat Flux ◽  
High Flux ◽  
Relaxation Model ◽  
Fourier Model

This brief investigates analytically non-Fourier effects in high flux conditions using the relaxation model for heat conduction. Unlike the Fourier model, the relaxation model predicts an instantaneous jump in the surface temperature of solids subjected to a step change in the surface heat flux. Under sufficiently high flux, 107 w/cm2, this jump in temperature may be several hundred degrees in magnitude, resulting in severe thermal stresses at the surface.

An Integrated Nano-Structured Heat Spreader for High Heat Flux Electronic Systems

2010 ◽  
Author(s):  
Siddharth Bhopte ◽  
Seshu B. Desu ◽  
Bahgat Sammakia
Keyword(s):  
Thermal Conductivity ◽  
Thermal Management ◽  
Thermal Stresses ◽  
High Heat ◽  
High Thermal Conductivity ◽  
Thermal Interface Material ◽  
High Heat Flux ◽  
Heat Spreader ◽  
Ongoing Research ◽  
Electronic Package

With the increase in power densities and decrease in chip and electronic package dimensions, their thermal management is a challenge and is a focus of several ongoing research efforts. To achieve the desired thermal management for optimal device operation, heat generated by the chip has to be effectively transferred to the ambient via several structures of the electronic package. Hence the need for development of high thermal conductivity structures is of prime importance. Heat spreaders quickly spread the heat generated by the chips over a larger area from where it is conducted to the ambient via heat sink. Heat-spreading research from a materials view point involves direct combination of high thermal conductivity materials within the microprocessor substrate. In this paper, a novel nano heat spreader design is proposed. Highly conductive graphene layer is integrated on a silicon carbide substrate on one side and thin films of carbon nano tubes as thermal interface material on the other side. Analytical solutions and case studies are presented to show that the proposed approach for the heat spreader design can yield very high effective thermal conductivity while remaining mechanically flexible, as required for reducing thermal stresses.

Methods for Determining the Mode I and Mode II Fracture Toughness of Glass Using Thermal Stresses

1990 ◽  
Vol 112 (2) ◽  
pp. 151-156 ◽  
Author(s):  
J. T. Gillanders ◽  
R. A. Riddle ◽  
R. D. Streit ◽  
I. Finnie
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Thermal Stresses ◽  
Soda Lime ◽  
Soda Lime Glass ◽  
Mode I ◽  
Mode Ii ◽  
Average Value ◽  
Mode Ii Fracture Toughness ◽  
Free Environment

The fracture toughness of soda-lime glass was measured by applying thermal stresses to center-cracked plates. Mode I cracking was achieved by chilling the crack faces. The stress intensity factor was obtained by combining temperature measurements with a finite element solution. The average value of KIC = 0.77 MN/m3/2 based on three tests agrees well with values in the literature for a water-free environment. Mode II cracking was achieved by applying a temperature gradient normal to the crack. A value KIIC = 1.6 MN/m3/2 was obtained in two tests using a finite element computation based on the temperature distribution computed from the specimen’s thermal boundary conditions.

Prediction of J-Integrals at Defects in W-9CR Steel Sandwich-Type Cooling Pipes

2021 ◽  
Author(s):  
Tristan Calvet ◽  
Yiqiang Wang ◽  
Minh-Son Pham ◽  
Catrin M. Davies
Keyword(s):  
Thermal Stresses ◽  
Structural Integrity ◽  
High Heat ◽  
High Heat Flux ◽  
Finite Element Analyses ◽  
First Wall ◽  
Sandwich Type ◽  
Brazed Joints ◽  
Rafm Steel ◽  
Cooling Pipes

Abstract Sandwich-type cooling pipes of the first wall of future fusion nuclear reactors (i.e. DEMO) will likely consist of tungsten brazed to a Reduced Activation Ferritic Martensitic (RAFM) steel. Under a high heat flux (HHF) (1–5 MW/m2) the mismatch in thermal expansion between tungsten and steel results in significant thermal stresses in the brazing region. These stresses can cause crack initiation and growth and thus compromise the structural integrity of such pipes. Finite element analyses have been performed on the brazed joints of a reference cooling assembly under HHF. Thermal stresses and resulting plastic strains were estimated for both the braze interlayer and parent materials. As images of brazed joints revealed, brazing processes are very likely to induce defects near the edges of the joints. A crack is therefore introduced in the brazed region where simulated stresses and strains are found to be the highest. J-integrals were calculated for cracks growing from an edge to the center of the considered piping assembly. The results are discussed in relation to the current sandwich-type piping design of the DEMO reactor.

Numerical Investigation of Thermofluid Flow Characteristics With Phase Change Against High Heat Flux in Porous Media

2005 ◽  
Author(s):  
K. Yuki ◽  
J. Abei ◽  
H. Hashizume ◽  
S. Toda
Keyword(s):  
Heat Flux ◽  
Solid Phase ◽  
Flow Characteristics ◽  
High Heat ◽  
Energy Model ◽  
High Heat Flux ◽  
Phase Flow ◽  
Two Phase ◽  
Thermal Nonequilibrium ◽  
Flow Case

This study numerically evaluates thermofluid flow characteristics in porous media by a newly developed “modified two-phase mixture model” applying a two-energy model instead of an one-energy model. In a single-phase flow case, thermal nonequilibrium between a solid phase and a fluid phase is observed in the area where inlet heat conducts from a heating wall and further convective heat transfer is more active. Though the degree of thermal nonequilibrium has a positive correlation with the increase in flow velocity and inlet heat flux, the degree is very low and can be ignored, from an engineering perspective. In a case of two-phase flow, the thermal nonequilibrium is remarkable in the two-phase region because the solid-phase temperature in this region is far beyond saturation temperature. A difference between these two models is obvious especially in the two-phase flow case, so that the numerical simulation with the two-energy model is indispensable under the high heat flux conditions of over 1MW/m2.

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