Transient Thermal Response of a Rotating Cylindrical Silicon Nitride Workpiece Subjected to a Translating Laser Heat Source, Part I: Comparison of Surface Temperature Measurements With Theoretical Results

1998 ◽  
Vol 120 (4) ◽  
pp. 899-906 ◽  
Author(s):  
J. C. Rozzi ◽  
F. E. Pfefferkorn ◽  
F. P. Incropera ◽  
Y. C. Shin
Keyword(s):  
Silicon Nitride ◽  
Surface Temperature ◽  
Material Removal ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Intense Laser ◽  
Laser Source ◽  
Beam Diameter ◽  
Laser Assisted Machining ◽  
Translational Speed

Laser-assisted machining (LAM), in which the material is locally heated by an intense laser source prior to material removal, provides an alternative machining process with the potential to yield higher material removal rates, as well as improved control of workpiece properties and geometry, for difficult-to-machine materials such as structural ceramics. To assess the feasibility of the LAM process and to obtain an improved understanding of governing physical phenomena, a laser assisted machining facility was developed and used to experimentally investigate the thermal response of a rotating silicon nitride workpiece heated by a translating CO2 laser. Using a focused laser pyrometer, surface temperature history measurements were made to determine the effect of rotational and translational speed, as well as the laser beam diameter and power, on thermal conditions. The experimental results are in good agreement with predictions based on a transient three-dimensional numerical simulation of the heating process. With increasing workpiece rotational speed, temperatures in proximity to the laser spot decrease, while those at circumferential locations further removed from the laser increase. Near-laser temperatures decrease with increasing beam diameter, while energy deposition by the laser and, correspondingly, workpiece surface temperatures increase with decreasing laser translational speed and increasing laser power, In a companion paper (Rozzi et al., 1998), the detailed numerical model is used to further elucidate thermal conditions associated with laser heating and to assess the merit of a simple, analytical model which is better suited for online process control.

Simulation and Experimental Study on Temperature Fields for Laser Assisted Machining of Silicon Nitride

2009 ◽  
Vol 419-420 ◽  
pp. 521-524
Author(s):  
Xue Feng Wu ◽  
Hong Zhi Zhang ◽  
Yang Wang ◽  
Chao Xie
Keyword(s):  
Silicon Nitride ◽  
Laser Heating ◽  
Laser Power ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Transfer Model ◽  
Beam Diameter ◽  
Power Laser ◽  
Laser Assisted Machining ◽  
Translational Speed

Laser assisted machining (LAM) is an effective method machining difficult-to-machine materials such as ceramics which uses a high power laser to focally heat a workpiece prior to material removal with a traditional cutting tool. A laser assisted machining experiment system was set up and a transient, three-dimensional heat transfer model was developed for LAM of silicon nitride using Finite Element Method to understand the thermal process of laser heating. The model was based on temperature-dependent thermophysical properties and the heat generated was neglected due to cutting which is assumed to be small compared to the heat generated by laser heating. The experiments were carried out to investigate the effects of operating parameters, such as laser power, laser translational speed, rotational speed, laser beam diameter and preheating time on temperature distribution. An infrared radiation thermometer was used to measure the surface temperature histories and the experimental results were in good agreement with predictions. The laser power and laser translational speed have the greatest influence on the temperature.

Experimental Investigation of Thermo-Mechanical Characteristics in Laser-Assisted Machining of Silicon Nitride Ceramics

1999 ◽  
Author(s):  
Shuting Lei ◽  
Yung C. Shin ◽  
Frank P. Incropera
Keyword(s):  
Silicon Nitride ◽  
Tool Wear ◽  
Material Removal ◽  
Mechanical Characteristics ◽  
Surface Damage ◽  
Workpiece Temperature ◽  
Laser Assisted Machining ◽  
Nitride Ceramics ◽  
On Line ◽  
Extent Of Damage

Abstract Laser-assisted machining (LAM) of silicon nitride (Si3N4) is evaluated for its potential to become an economically viable process in fabricating precision ceramic parts. On-line measurements of cutting force and workpiece temperature are performed, and tool wear and surface integrity are examined. Tool wear characteristics are determined as a function of workpiece temperature, which is measured on-line using a laser pyrometer. Tool wear/failure mechanisms are characterized using optical microscopy, while application of scanning electron microscopy to heated and machined surfaces, as well as to chips, is used to infer material removal mechanisms and the extent of damage caused by LAM. The sub-surface damage of parts produced by LAM is compared with that of typical ground parts.

Experimental Evaluation of the Laser Assisted Machining of Silicon Nitride Ceramics

1999 ◽  
Vol 122 (4) ◽  
pp. 666-670 ◽  
Author(s):  
Jay C. Rozzi ◽  
Frank E. Pfefferkorn ◽  
Yung C. Shin ◽  
Frank P. Incropera
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Silicon Nitride ◽  
Material Removal ◽  
Cutting Tool ◽  
Operating Conditions ◽  
Surface Cracking ◽  
Laser Assisted Machining ◽  
Wide Range

To assess the feasibility of the laser assisted machining (LAM) process for the machining of difficult-to-machine materials such as structural ceramics, experiments were performed on silicon nitride workpieces for a wide range of operating conditions. Data for cutting forces and surface temperatures indicate that the lower bound of the material removal temperature for avoidance of cutting tool and/or workpiece fracture corresponds to the YSiAlON glass transition temperature (920–970°C). As temperatures near the cutting tool increase to values above the glass transition temperature, the glassy phase softens, facilitating visco-plastic flow and, correspondingly, the production of semi-continuous or continuous chips. The silicon nitride workpiece machined had a surface roughness of Ra=0.39 μm at the nominal LAM operating condition. Examination of the machined surfaces and chips reveals no detectable sub-surface cracking or significant changes in microstructure, respectively. Relative to grinding, the most significant advantage of LAM is its ability to achieve much larger material removal rates with high workpiece surface quality and reasonable levels of tool wear. [S1087-1357(00)00704-8]

Experimental Investigation of Thermo-Mechanical Characteristics in Laser-Assisted Machining of Silicon Nitride Ceramics

2000 ◽  
Vol 123 (4) ◽  
pp. 639-646 ◽  
Author(s):  
S. Lei ◽  
Y. C. Shin ◽  
F. P. Incropera
Keyword(s):  
Silicon Nitride ◽  
Tool Wear ◽  
Material Removal ◽  
Mechanical Characteristics ◽  
Surface Damage ◽  
Workpiece Temperature ◽  
Laser Assisted Machining ◽  
Nitride Ceramics ◽  
On Line ◽  
Extent Of Damage

Laser-assisted machining (LAM) of silicon nitride Si3N4 is evaluated for its potential to become an economically viable process in fabricating precision ceramic parts. On-line measurements of cutting force and workpiece temperature are performed, and tool wear and surface integrity are examined. Tool wear characteristics are determined as a function of workpiece temperature, which is measured on-line using a laser pyrometer. Tool wear/failure mechanisms are characterized using optical microscopy, while application of scanning electron microscopy to heated and machined surfaces, as well as to chips, is used to infer material removal mechanisms and the extent of damage caused by LAM. The sub-surface damage of parts produced by LAM is compared with that of typical ground parts.

Ultrafast Laser Cleaning of Daguerreotypes

2011 ◽  
Vol 1319 ◽  
Author(s):  
Michael J. Abere ◽  
Ryan D. Murphy ◽  
Bianca Jackson ◽  
Gerard Mourou ◽  
Michel Menu ◽  
...  
Keyword(s):  
Material Removal ◽  
Silver Oxide ◽  
Laser Pulses ◽  
Silver Sulfide ◽  
Ultrafast Laser ◽  
Beam Diameter ◽  
Chemical Cleaning ◽  
Silver Substrate ◽  
Fs Laser ◽  
Lower Material

ABSTRACTAn ultrafast laser irradiation method for the removal of corrosion from Daguerreotypes without detrimentally affecting image quality has been developed. Corrosion products such as silver oxide and silver sulfide may be removed by chemical cleaning but these reactions are hard to control and are often damaging to the underlying silver, ruining the image. The Ti:Sapphire 150 fs laser pulses used in this study are focused to a beam diameter of 60 μm and are normally incident to the Daguerreotype. It was found that the corrosion layer has a lower material removal threshold than silver allowing for removal of corrosion with minimal removal of vital information contained in the silver substrate.

scholarly journals High-Fidelity Calculation of Effective Thermal Response of Composite Media With Heat Generation Source

2020 ◽  
Author(s):  
Kevin Irick ◽  
Nima Fathi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Nuclear Fuel ◽  
Heat Generation ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Unit Cell ◽  
High Fidelity ◽  
Conductive Heat

Abstract The complexity of conductive heat transfer in a structure increases with heterogeneity (e.g., multi-component solid-phase systems with a source of internal thermal heat generation). Any discontinuity of material property — especially thermal conductivity — would warrant a thorough analysis to evaluate the thermal behavior of the system of interest. Heterogeneous thermal conditions are crucial to heat transfer in nuclear fuel assemblies, because the thermal behavior within the assemblies is governed significantly by the heterogeneous thermal conditions at both the system and component levels. A variety of materials have been used as nuclear fuels, the most conventional of which is uranium dioxide, UO2. UO2 has satisfactory chemical and irradiation tolerances in thermal reactors, whereas the low thermal conductivity of porous UO2 can prove challenging. Therefore, the feasibility of enhancing the thermal conductivity of oxide fuels by adding a high-conductivity secondary solid component is still an important ongoing topic of investigation. Undoubtedly, long-term, stable development of clean nuclear energy would depend on research and development of innovative reactor designs and fuel systems. Having a better understanding of the thermal response of the unit cell of a composite that represents a fuel matrix cell would help to develop the next generation of nuclear fuel and understand potential performance enhancements. The aim of this article is to provide an assessment of a high-fidelity computational model response of heterogeneous materials with heat generation in circular fillers. Two-dimensional, steady-state systems were defined with a circular, heat-generating filler centered in a unit-cell domain. A Fortran-based finite element method (FEM) code was used to solve the heat equation on an unstructured triangular mesh of the systems. This paper presents a study on the effects of a heat-generating filler material’s relative size and thermal conductivity on effective thermal conductance, Geff, within a heterogenous material. Code verification using the method of manufactured solution (MMS) was employed, showing a second-order accurate numerical implementation. Solution verification was performed using a global deviation grid convergence index (GCI) method to assess solution convergence and estimate solution numerical uncertainty, Unum. Trend results are presented, showing variable response in Geff to filler size and thermal conductivity.

scholarly journals A COMBINED USE OF FDM AND DOE METHOD TO DERIVE A NEW TRANSIENT SIMPLIFIED SEMI-ANALYTICAL MODEL: A CASE STUDY OF ANHYDRITE RADIANT SLAB

2020 ◽  
Vol 330 ◽  
pp. 01002
Author(s):  
Abdelatif Merabtine ◽  
Abdelhamid Kheiri ◽  
Salim Mokraoui
Keyword(s):  
Surface Temperature ◽  
Analytical Model ◽  
Numerical Models ◽  
Thermal Response ◽  
Sensitivity Study ◽  
Conventional Heating ◽  
Heating Systems ◽  
Combined Use ◽  
Scale Test ◽  
Radiant Floor Heating

Radiant floor heating systems (FHS) are considered as reliable heating systems since they ensure maintaining inside air temperature and reduce its fluctuations more efficiently than conventional heating systems. The presented study investigates the dynamic thermal response of an experimental FHS equipped with an anhydrite radiant slab. A new simplified model based on an analytical correlation is proposed to evaluate the heating radiant slab surface temperature and examine its thermal behavior under dynamic conditions. In order the validate the developed analytical model, an experimental scenario, under transient conditions, was performed in a monitored full-scale test cell. 2D and 3D numerical models were also developed to evaluate the accuracy of the analytical model. The method of Design of Experiments (DoE) was used to both derive meta-models, to analytically estimate the surface temperature, and perform a sensitivity study.

Sign in / Sign up

Export Citation Format

Share Document