This paper is aimed at the investigation of the diffusion boundary layer near the cooled casting surface encountered in the horizontal continuous casting process of carbon steel. The strip casting process is a relatively new continuous casting process. This process makes it possible to produce high-quality flat steel products directly, without using hot rolling. This explains why this process is very attractive for industry. Extensive numerical simulations under equilibrium and nonequilibrium assumptions provide valuable insight into the physics of diffusion boundary layer.
{"title":"Numerical Modeling of Diffusion Boundary Layer in Strip Casting Process of Carbon Steel","authors":"A. Kuznetsov","doi":"10.1115/imece2000-1487","DOIUrl":"https://doi.org/10.1115/imece2000-1487","url":null,"abstract":"\u0000 This paper is aimed at the investigation of the diffusion boundary layer near the cooled casting surface encountered in the horizontal continuous casting process of carbon steel. The strip casting process is a relatively new continuous casting process. This process makes it possible to produce high-quality flat steel products directly, without using hot rolling. This explains why this process is very attractive for industry. Extensive numerical simulations under equilibrium and nonequilibrium assumptions provide valuable insight into the physics of diffusion boundary layer.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"232 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121071410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper investigates the effect of ablation of absorbing dielectrics by two successive ultra short pulses from an excimer laser source. The numerical model is based on two photon absorption followed by thermal degradation and diffusion. Unlike most previous studies the present formulation considers the transient nature of laser propagation within the medium. Heating of the material is dependent on light absorption by chromophores while ablation occurs through sublimation of the material from the surface. The mathematical formulation takes into consideration the saturation effects within the framework of a three level system of the electronic structure of chromophores. This involves solving a set of coupled rate equations, heat diffusion equation, and the transient radiative transport equation, using Fromm’s scheme. Results for the temperature distribution and ablation depth are obtained for different laser parameters and material properties. Parametric study of the delay time between two successive pulses, laser pulse width, laser fluence, activation energy, and the relaxation time is only performed in this paper for the purpose of brevity. The results obtained by the consideration of the transient radiative transfer equation are compared with the steady state formulation and significant differences are observed in the temperature profiles and the ablation depth.
{"title":"Parametric Study of the Ablation Characteristics of Absorbing Dielectrics by Short Pulse Laser","authors":"S. George, K. Mitra","doi":"10.1115/imece2000-1475","DOIUrl":"https://doi.org/10.1115/imece2000-1475","url":null,"abstract":"\u0000 This paper investigates the effect of ablation of absorbing dielectrics by two successive ultra short pulses from an excimer laser source. The numerical model is based on two photon absorption followed by thermal degradation and diffusion. Unlike most previous studies the present formulation considers the transient nature of laser propagation within the medium. Heating of the material is dependent on light absorption by chromophores while ablation occurs through sublimation of the material from the surface. The mathematical formulation takes into consideration the saturation effects within the framework of a three level system of the electronic structure of chromophores. This involves solving a set of coupled rate equations, heat diffusion equation, and the transient radiative transport equation, using Fromm’s scheme. Results for the temperature distribution and ablation depth are obtained for different laser parameters and material properties. Parametric study of the delay time between two successive pulses, laser pulse width, laser fluence, activation energy, and the relaxation time is only performed in this paper for the purpose of brevity. The results obtained by the consideration of the transient radiative transfer equation are compared with the steady state formulation and significant differences are observed in the temperature profiles and the ablation depth.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116943923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper discusses the properties of an improved thermoplastic composite by alignment of vapor grown carbon fiber (VGCF) suspended in a polypropylene matrix. VGCF provides improved mechanical and electrical properties in composites. In this study an extruder was used to shear mix and extrude VGCF/polypropylene mixtures containing fiber volume fractions of 2.5%, 7% and 11% through a converging-annular die which produces a high degree of fiber alignment along the flow direction. X-ray diffraction analysis performed on the extruded composite strands showed that the fibers were oriented approximately ± 23.7, ± 28.15 and ± 30.0 degrees along the preferred direction for the 2.5%, 7% and 11% specimens, respectively. Tensile tests were done in both the preferred and transverse directions of samples reinforced with pyrolytically stripped VGCF. When compared to polypropylene, there was a 36.5%, 69.4% and 82.0% increase in tensile strength, and a 94.9%, 173.7% and 218.2% increase in modulus for the 2.5%, 7% and 11% VGCF mixtures along the preferred direction, respectively. The tensile strength and modulus in the transverse direction increased as the fiber volume content increased, however, all values were well below that of polypropylene. This behavior could be attributed to stress concentrations in the composite material. Electrical resistivity measurements were made on samples reinforced with two types of VGCF. The results concluded that the electrical conductance of the polymer strands reinforced with a heat-treated VGCF was far superior to those reinforced with a pyrolytically stripped VGCF.
{"title":"Improved Thermoplastic Composite by Alignment of Vapor Grown Carbon Fiber","authors":"Rex J. Kuriger","doi":"10.1115/imece2000-1493","DOIUrl":"https://doi.org/10.1115/imece2000-1493","url":null,"abstract":"\u0000 This paper discusses the properties of an improved thermoplastic composite by alignment of vapor grown carbon fiber (VGCF) suspended in a polypropylene matrix. VGCF provides improved mechanical and electrical properties in composites. In this study an extruder was used to shear mix and extrude VGCF/polypropylene mixtures containing fiber volume fractions of 2.5%, 7% and 11% through a converging-annular die which produces a high degree of fiber alignment along the flow direction. X-ray diffraction analysis performed on the extruded composite strands showed that the fibers were oriented approximately ± 23.7, ± 28.15 and ± 30.0 degrees along the preferred direction for the 2.5%, 7% and 11% specimens, respectively. Tensile tests were done in both the preferred and transverse directions of samples reinforced with pyrolytically stripped VGCF. When compared to polypropylene, there was a 36.5%, 69.4% and 82.0% increase in tensile strength, and a 94.9%, 173.7% and 218.2% increase in modulus for the 2.5%, 7% and 11% VGCF mixtures along the preferred direction, respectively. The tensile strength and modulus in the transverse direction increased as the fiber volume content increased, however, all values were well below that of polypropylene. This behavior could be attributed to stress concentrations in the composite material. Electrical resistivity measurements were made on samples reinforced with two types of VGCF. The results concluded that the electrical conductance of the polymer strands reinforced with a heat-treated VGCF was far superior to those reinforced with a pyrolytically stripped VGCF.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122736498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The present work investigates the efficiency of the multigrid numerical method applied to solve two-dimensional laminar velocity and temperature fields inside a rectangular domain. Numerical analysis is based on the finite volume discretization scheme applied to structured orthogonal regular meshes. Performance of the correction storage (CS) multigrid algorithm is compared for different inlet Reynolds number (Rein) and number of grids. Up to four grids were used for both V- and W-cycles. Simultaneous and uncoupled temperature-velocity solution schemes were also applied. Advantages in using more than one grid is discussed. Results further indicate an increase in the computational effort for higher Rein and an optimal number of relaxation sweeps for both V- and W-cycles.
{"title":"Multigrid Numerical Solutions of Non-Isothermal Laminar Recirculating Flows","authors":"M. D. de Lemos, Maximilian S. Mesquita","doi":"10.1115/imece1999-1089","DOIUrl":"https://doi.org/10.1115/imece1999-1089","url":null,"abstract":"\u0000 The present work investigates the efficiency of the multigrid numerical method applied to solve two-dimensional laminar velocity and temperature fields inside a rectangular domain. Numerical analysis is based on the finite volume discretization scheme applied to structured orthogonal regular meshes. Performance of the correction storage (CS) multigrid algorithm is compared for different inlet Reynolds number (Rein) and number of grids. Up to four grids were used for both V- and W-cycles. Simultaneous and uncoupled temperature-velocity solution schemes were also applied. Advantages in using more than one grid is discussed. Results further indicate an increase in the computational effort for higher Rein and an optimal number of relaxation sweeps for both V- and W-cycles.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122927325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work investigates photon-counting measurements during pulsed laser heating of an Al2O3-TiC substrate. The excitation source is a Nd:YAG laser operating at a fundamental wavelength of 1064 nm. The laser fluence is varied in the range from 0.272 J/cm2 to 0.839 J/cm2. The emission spectra, captured by single photon counting, are related to temperature by Planck’s distribution. The suitability of this method is discussed. Pulse exposure, the number of pulses that a given surface location receives, is found to be a vitally important parameter. Numerical simulations of transient heat conduction support the results of high pulse exposure measurements. Low pulse exposure experiments exhibit higher temperatures due to chemical reactions at the surface and grain boundary effects.
{"title":"Photon Counting Temperature Measurements During Pulsed Laser Heating of Al2O3-TiC Ceramics","authors":"T. M. Harms, Xianfan Xu","doi":"10.1115/imece1999-1076","DOIUrl":"https://doi.org/10.1115/imece1999-1076","url":null,"abstract":"\u0000 This work investigates photon-counting measurements during pulsed laser heating of an Al2O3-TiC substrate. The excitation source is a Nd:YAG laser operating at a fundamental wavelength of 1064 nm. The laser fluence is varied in the range from 0.272 J/cm2 to 0.839 J/cm2. The emission spectra, captured by single photon counting, are related to temperature by Planck’s distribution. The suitability of this method is discussed.\u0000 Pulse exposure, the number of pulses that a given surface location receives, is found to be a vitally important parameter. Numerical simulations of transient heat conduction support the results of high pulse exposure measurements. Low pulse exposure experiments exhibit higher temperatures due to chemical reactions at the surface and grain boundary effects.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123339805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High Knudsen (Kn) number flows are found in vacuum and micro-scale systems. Such flows are characterized by non-continuum behavior. For gases, the flows are usually in the slip or transition regimes. In this paper, the direct simulation Monte Carlo (DSMC) method has been applied to compute low pressure, high Kn flow fields in partially heated channels. Computations were carried out for nitrogen, argon, hydrogen, oxygen and noble gas mixtures. Variation of the Kn is obtained by reducing the pressure while keeping the channel width constant. Nonlinear pressure profiles along the channel centerline are observed. Heat transfer from the channel walls is also calculated and compared with the Graetz solution. The effects of varying pressure, inlet flow and gas transport properties (Kn, Reynolds number, Re and the Prandtl number, Pr respectively) on the wall heat transfer (Nu) were examined. A simplified correlation for predicting Nu¯ as a function of Pe¯ and Kn¯ is presented.
{"title":"Computations of Low Pressure Fluid Flow and Heat Transfer in Ducts Using Direct Simulation Monte Carlo Method","authors":"Fang Yan, B. Farouk","doi":"10.1115/imece1999-1063","DOIUrl":"https://doi.org/10.1115/imece1999-1063","url":null,"abstract":"\u0000 High Knudsen (Kn) number flows are found in vacuum and micro-scale systems. Such flows are characterized by non-continuum behavior. For gases, the flows are usually in the slip or transition regimes. In this paper, the direct simulation Monte Carlo (DSMC) method has been applied to compute low pressure, high Kn flow fields in partially heated channels. Computations were carried out for nitrogen, argon, hydrogen, oxygen and noble gas mixtures. Variation of the Kn is obtained by reducing the pressure while keeping the channel width constant. Nonlinear pressure profiles along the channel centerline are observed. Heat transfer from the channel walls is also calculated and compared with the Graetz solution. The effects of varying pressure, inlet flow and gas transport properties (Kn, Reynolds number, Re and the Prandtl number, Pr respectively) on the wall heat transfer (Nu) were examined. A simplified correlation for predicting Nu¯ as a function of Pe¯ and Kn¯ is presented.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133921438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. N. Husain, J. Seyed-Yagoobi, Jefferson W. Wirtz
Infrared (IR) radiation is used for heating/drying of moist paper owing to its penetration characteristic inside porous media, and a high absorptivity of water in the infrared wavelength range. A series of experiments has been conducted along with the development of a theoretical model to study IR drying characteristics. Paper samples are instrumented with thermocouples in the thickness direction to obtain transient temperature profiles along with moisture data. The experimental results confirm IR energy penetration into the paper sheet. The numerical model predicts the experimental transient temperature profile for thinner samples fairly well but tends to under predict the temperatures with progressively thicker samples. Theoretical depth of IR penetration, as a function of sample initial moisture content, has been calculated and was found to decrease with increasing moisture content.
{"title":"Theoretical and Experimental Study of Heating/Drying of Paper Sheet With Gas Heated Infrared Emitter","authors":"A. N. Husain, J. Seyed-Yagoobi, Jefferson W. Wirtz","doi":"10.1115/imece1999-1083","DOIUrl":"https://doi.org/10.1115/imece1999-1083","url":null,"abstract":"\u0000 Infrared (IR) radiation is used for heating/drying of moist paper owing to its penetration characteristic inside porous media, and a high absorptivity of water in the infrared wavelength range. A series of experiments has been conducted along with the development of a theoretical model to study IR drying characteristics. Paper samples are instrumented with thermocouples in the thickness direction to obtain transient temperature profiles along with moisture data. The experimental results confirm IR energy penetration into the paper sheet. The numerical model predicts the experimental transient temperature profile for thinner samples fairly well but tends to under predict the temperatures with progressively thicker samples. Theoretical depth of IR penetration, as a function of sample initial moisture content, has been calculated and was found to decrease with increasing moisture content.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131427499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper successfully proposes a novel model to predict nugget development during resistance spot welding (RSW) of binary Al-alloys. The model employs a coupled thermal-electrical-mechanical analysis, and also accounts for phase change and convective transport in weld pool. Faying surface contact area and its pressure distribution are simulated from coupled thermal-mechanical model using a finite element method. Temperature dependent thermal, electrical and mechanical properties are used. The proposed model can successfully calculate most of the RSW response in term of nugget diameter and thickness, the extent of heat affected zone, etc. The calculated nugget shape based on the thermal model agrees well with the experimental data. Convection effect due to the interactions between phases in the porous mushy zone and the buoyancy force arising from the temperature difference is determined to be not significant for the weld-nugget formation. The proposed model can be used to optimize RSW process parameters for industrial welding.
{"title":"Numerical Study of Thermal Modeling of Resistance Spot Welding Utilizing Coupled Thermal-Electrical-Mechanical Analysis","authors":"Lijun Xu, J. Khan, Y. Chao, K. Broach","doi":"10.1115/imece1999-1097","DOIUrl":"https://doi.org/10.1115/imece1999-1097","url":null,"abstract":"\u0000 This paper successfully proposes a novel model to predict nugget development during resistance spot welding (RSW) of binary Al-alloys. The model employs a coupled thermal-electrical-mechanical analysis, and also accounts for phase change and convective transport in weld pool. Faying surface contact area and its pressure distribution are simulated from coupled thermal-mechanical model using a finite element method. Temperature dependent thermal, electrical and mechanical properties are used. The proposed model can successfully calculate most of the RSW response in term of nugget diameter and thickness, the extent of heat affected zone, etc. The calculated nugget shape based on the thermal model agrees well with the experimental data. Convection effect due to the interactions between phases in the porous mushy zone and the buoyancy force arising from the temperature difference is determined to be not significant for the weld-nugget formation. The proposed model can be used to optimize RSW process parameters for industrial welding.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133736872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Richard P. Feynman introduced the field of microscale and nanoscale engineering in 1959 by giving a talk on how to make things very small. Feynman’s premise was that no fundamental physical laws limit the size of a machine down to the microscopic level. Is this true for all types of machines? Are micro thermal devices fundamentally different than mechanically-based machines with respect to their scaling laws? This paper demonstrates that micro thermal engines do indeed suffer serious performance degradation as their characteristic size is reduced. A micro thermal engine, and more generally, any thermally-based micro device, depends on establishing a temperature difference between two regions within a small structure. In this paper, the performance of a micro thermal engine is explored as a function of the characteristic length parameter, L. In the development, the important features of thermal engines are discussed in the context of developing simple scaling laws predicting the dependency of the operating efficiency on L. After this is accomplished, a general model is derived for a heat engine operating between two temperature reservoirs and having both intrinsic and extrinsic sources of irreversibility, i.e. thermal conductances and heat leakage paths for the heat flow. With this model and typical numerical values for the conductances, micro heat engine performance is predicted as the characteristic size is reduced. This paper demonstrates that under at least one particular formulation of the problem, there may indeed be some room at the bottom. However, heat transfer does play a critical role in determining micro engine performance and depending on how the heat transfer through the engine is modeled, vanishingly small efficiencies can result as the characteristic engine size goes to zero.
1959年，理查德·p·费曼(Richard P. Feynman)在一次关于如何使物体变得非常小的演讲中，引入了微尺度和纳米尺度工程领域。费曼的前提是，没有基本的物理定律将机器的大小限制在微观水平。这是否适用于所有类型的机器?就其标度定律而言，微热装置与基于机械的机器有根本的不同吗?本文论证了微热机的特性尺寸减小时，其性能确实会受到严重的影响。一个微热机，或者更一般地说，任何基于热的微型装置，都依赖于在一个小结构中建立两个区域之间的温差。本文将微型热机的性能作为特征长度参数l的函数进行了探讨。在发展过程中，通过建立预测运行效率与l的依赖关系的简单标度定律，讨论了热机的重要特征。在此基础上，推导了在两个温度储层之间工作的热机的通用模型，该模型具有内在和外在的不可逆性。即热流的导热系数和热泄漏路径。利用该模型和典型的电导数值，预测了特征尺寸减小时微热机的性能。本文证明，在问题的至少一种特殊表述下，可能确实存在一些底部空间。然而，传热确实在决定微型发动机性能方面起着至关重要的作用，并且取决于如何对发动机的传热进行建模，当特征发动机尺寸趋近于零时，效率就会变得微乎其微。
{"title":"Micro Thermal Engines: Is There Any Room at the Bottom?","authors":"R. Peterson","doi":"10.1115/imece1999-1065","DOIUrl":"https://doi.org/10.1115/imece1999-1065","url":null,"abstract":"\u0000 Richard P. Feynman introduced the field of microscale and nanoscale engineering in 1959 by giving a talk on how to make things very small. Feynman’s premise was that no fundamental physical laws limit the size of a machine down to the microscopic level. Is this true for all types of machines? Are micro thermal devices fundamentally different than mechanically-based machines with respect to their scaling laws? This paper demonstrates that micro thermal engines do indeed suffer serious performance degradation as their characteristic size is reduced. A micro thermal engine, and more generally, any thermally-based micro device, depends on establishing a temperature difference between two regions within a small structure. In this paper, the performance of a micro thermal engine is explored as a function of the characteristic length parameter, L. In the development, the important features of thermal engines are discussed in the context of developing simple scaling laws predicting the dependency of the operating efficiency on L. After this is accomplished, a general model is derived for a heat engine operating between two temperature reservoirs and having both intrinsic and extrinsic sources of irreversibility, i.e. thermal conductances and heat leakage paths for the heat flow. With this model and typical numerical values for the conductances, micro heat engine performance is predicted as the characteristic size is reduced. This paper demonstrates that under at least one particular formulation of the problem, there may indeed be some room at the bottom. However, heat transfer does play a critical role in determining micro engine performance and depending on how the heat transfer through the engine is modeled, vanishingly small efficiencies can result as the characteristic engine size goes to zero.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133774498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lasers are emerging as a valuable tool for shaping and cutting hard and brittle ceramics. Unfortunately, the large, concentrated heat flux rates that allow the laser to efficiently cut and shape the ceramic also result in large localized thermal stresses in a small heat-affected zone. These notable thermal stresses can lead to micro-cracks, a decrease in strength and fatigue life, and possibly catastrophic failure. In order to assess where, when, and what stresses occur during laser scribing, an elastic stress model has been incorporated into a three-dimensional scribing and cutting code. First, the code predicts the temporal temperature fields and the receding surface of the ceramic. Then, using the scribed geometry and temperature field, the elastic stress fields are calculated as they develop and decay during the laser scribing process. The analysis allows the prediction of stresses during continuous wave and pulsed laser operation, a variety of cutting speeds and directions, and various shapes and types of ceramic material. The results of the analysis show substantial tensile stresses develop over a thick layer below and parallel to the surface, which may be the cause of experimentally observed subsurface cracks.
{"title":"Transient Elastic Stress Development During Laser Scribing of Ceramics","authors":"Thomas M. Mallison, M. Modest","doi":"10.1115/imece1999-1081","DOIUrl":"https://doi.org/10.1115/imece1999-1081","url":null,"abstract":"\u0000 Lasers are emerging as a valuable tool for shaping and cutting hard and brittle ceramics. Unfortunately, the large, concentrated heat flux rates that allow the laser to efficiently cut and shape the ceramic also result in large localized thermal stresses in a small heat-affected zone. These notable thermal stresses can lead to micro-cracks, a decrease in strength and fatigue life, and possibly catastrophic failure. In order to assess where, when, and what stresses occur during laser scribing, an elastic stress model has been incorporated into a three-dimensional scribing and cutting code. First, the code predicts the temporal temperature fields and the receding surface of the ceramic. Then, using the scribed geometry and temperature field, the elastic stress fields are calculated as they develop and decay during the laser scribing process. The analysis allows the prediction of stresses during continuous wave and pulsed laser operation, a variety of cutting speeds and directions, and various shapes and types of ceramic material. The results of the analysis show substantial tensile stresses develop over a thick layer below and parallel to the surface, which may be the cause of experimentally observed subsurface cracks.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121943939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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