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.

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.

Three Dimensional Microstructures from Metal Carbonyls

1998 ◽  
Vol 542 ◽  
Author(s):  
Jan-Erik Lind ◽  
Olli Nyrhila ◽  
Juha Kotila ◽  
Tatu Syvanen
Keyword(s):  
Laser Power ◽  
Growth Parameters ◽  
Three Dimensional ◽  
Spot Size ◽  
Layer By Layer ◽  
Metal Carbonyls ◽  
Power Laser ◽  
Iron Carbonyls ◽  
Scan Speed ◽  
Gas Pressures

Abstract3D-LCVD of nickel and iron carbonyls was studied in order to grow 3-D metal forms under static or scanning Nd:YAG-laser beam. In addition to growth, emphasis was also placed on the prevention of the simultaneous decomposition of carbon monoxide, which interferes with the metal growth process. This was essential, because the fairly high precursor gas pressures of the metal carbonyls are very tempting for the 3D-LCVD. Parameters to be optimized included precursor pressure, laser power, laser scan speed and spot size. In order to optimize the growth parameters, the microstructures of the resulting forms were studied using SEM. Comparison between static and scanning growth is presented with the building philosophy in mind, e.g. whether to build structures layer by layer, from modules or in conjunction with another process to compensate for their shortcomings. The substrates used included steel, graphite and porous bronze.The results indicated different microstructures for iron and nickel, which were dependent on the total/precursor pressure. In the scanning experiments, nickel produced very thin films of high reflectivity, whereas iron produced a structure which could be described as a crystalline spider's web. The static experiments produced solid rods in the case of nickel, whereas with iron, the rods were hollow, even with same spot sizes. Moreover, an evident change in the microstructure of the nickel forms as a function of pressure was observed. The 3-D growth rate of the static experiments seemed very promising for the forthcoming scanning experiments.

Numerical Analysis on the Temperature Field in Laser-Plasma Hybrid Welding of an Aluminum Alloy

2008 ◽  
Vol 580-582 ◽  
pp. 279-282
Author(s):  
Zhi Ning Li ◽  
Bao Hua Chang ◽  
Dong Du ◽  
Hua Zhang
Keyword(s):  
Heat Transfer ◽  
Aluminum Alloy ◽  
Laser Plasma ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Transfer Model ◽  
Heat Sources ◽  
Hybrid Welding ◽  
Plasma Arc ◽  
Simulation Results

A three dimensional heat transfer model on laser-plasma hybrid welding has been proposed, that takes into account the interaction between laser beam and plasma arc. Through FEM computation, the temperature fields were computed and analyzed for an Al-Li alloy during laserplasma hybrid welding with different distances between the two heat sources. The simulation results are in agreement with the experimental results.

Laser-Assisted Machining of Reaction Sintered Mullite Ceramics

2001 ◽  
Author(s):  
Patrick A. Rebro ◽  
Yung C. Shin ◽  
Frank P. Incropera
Keyword(s):  
Cutting Force ◽  
Laser Heating ◽  
Laser Power ◽  
Material Removal ◽  
Operating Conditions ◽  
Laser Assisted Machining ◽  
Feed Force ◽  
Grinding Tool ◽  
Continuous Chip ◽  
Mullite Ceramics

Abstract The present study focuses on the evaluation of the laser-assisted machining (LAM) of pressureless sintered mullite ceramics. Due to mullite’s low thermal diffusivity and tensile strength, a new method for applying laser power is devised to eliminate cracking and fracture of the workpiece during laser heating. The LAM process is characterized by means of cutting force and surface temperature measurements for a variety of operating conditions. Estimated material removal temperatures and the ratio of the feed force to the main cutting force are used to determine material removal mechanisms and regimes for brittle fracture and semi-continuous and continuous chip formation. Surface roughness and subsurface damage are compared for typical parts produced by LAM and grinding. Tool wear characteristics are investigated for variations in laser power, and hence material removal temperature, during LAM of mullite with carbide tools.

Thermal Modeling for Laser-Assisted Machining of Silicon Nitride Ceramics with Complex Features

2005 ◽  
Vol 128 (2) ◽  
pp. 425-434 ◽  
Author(s):  
Yinggang Tian ◽  
Yung C. Shin
Keyword(s):  
Silicon Nitride ◽  
Thermal Model ◽  
Three Dimensional ◽  
Infrared Camera ◽  
Ceramic Materials ◽  
Industrial Applications ◽  
Laser Assisted Machining ◽  
Nitride Ceramics ◽  
Complex Features ◽  
Fabrication Costs

The feasibility of laser-assisted machining (LAM) and its potential to significantly reduce fabrication costs and improve product quality have been shown experimentally for various ceramic materials. However, no systematical investigation has been performed to expand LAMs capability to parts with complex features, although such capability is essential for industrial applications. This paper presents a transient, three-dimensional thermal model developed for LAM of workpieces with complex geometric features and its validation by in-process surface temperature measurements with an infrared camera. It is shown that the LAM experiments designed based on the predictions by the thermal model successfully produced silicon nitride parts with complex features, thus demonstrating the capabilities of LAM in fabricating ceramic parts suitable for industrial implementation.

Scratch Tests on Granite Using Micro-Laser Assisted Machining Technique

2015 ◽  
Author(s):  
Hossein Mohammadi ◽  
John A. Patten
Keyword(s):  
Laser Heating ◽  
Laser Power ◽  
Single Point ◽  
Brittle Materials ◽  
Past Research ◽  
Depth Of Cut ◽  
Shear Stresses ◽  
Granite Sample ◽  
Laser Assisted Machining ◽  
Scratch Tests

In this study, micro-laser assisted machining (μ-LAM) technique is used to perform scratch test on a granite sample. Rocks are generally considered as brittle materials with poor machinability and severe fracture can be resulted when trying to cut them due to their low fracture toughness. Due to increasing demand for these materials in industry with many applications, finding a fast and cost effective process with higher product quality seems essential. In past research in our research group, it has been demonstrated that machining of brittle materials such as semiconductors and ceramics in ductile regime is possible due to the high pressure phase transformation (HPPT) occurring in the material caused by the high compressive and shear stresses induced by a single point diamond tool tip. Scratch tests were performed on the granite sample and to further augment the process, traditional cutting is coupled with the laser to soften the material and get the higher depth of cut. In this research, results of scratch tests done on granite, with and without laser heating have been compared. The effect of laser heating was studied by verifying the depths of cuts for scratch tests with varying the laser power during the process. Microscopic images and three-dimensional profiles of cuts taken by using a white light interferometer were investigated. Results show that using laser can increase depth of cut and with 15 W laser power it is increased — for different regions of granite sample — from 25% to 95%.

Numerical Simulation of Transient Temperature Fields in Solids Irradiated by Moving Gaussian and Donut Sources

2011 ◽  
Vol 312-315 ◽  
pp. 959-964
Author(s):  
Oronzio Manca ◽  
Sergio Nardini ◽  
Daniele Ricci ◽  
Salvatore Tamburrino
Keyword(s):  
Power Distribution ◽  
Three Dimensional ◽  
Axial Direction ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Transfer Model ◽  
Finite Width ◽  
Infinite Length ◽  
Laser Material Processing ◽  
Motion Direction

This work presents a three-dimensional heat transfer model developed for laser material processing with a moving Gaussian and donut heat sources, using Comsol Multhiphysics 3.5 code. The laser beam, having a defined power distribution, strikes the surface of an opaque substrate of semi infinite length but finite width and depth moving with a uniform velocity in the positive axial direction. The solid dimension along the motion direction is assumed to be infinite or semi-infinite, while a finite width and thickness are considered. Thermal properties are considered temperature dependent. Surface heat losses toward the ambient are taken into account. The results are presented in terms of temperature profiles and thermal fields are given for some Biot and material thicknesses at a constant Peclet number.

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