Distinct Element Simulation of Laser Assisted Machining of Silicon Nitride Ceramics: Surface/Subsurface Cracks and Damage

2005 ◽  
Author(s):  
X. Shen ◽  
S. Lei
Keyword(s):  
Silicon Nitride ◽  
Distinct Element ◽  
Rake Angle ◽  
Effect Of Temperature ◽  
Depth Of Cut ◽  
Surface Cracks ◽  
Laser Assisted Machining ◽  
Subsurface Cracks ◽  
Element Simulation ◽  
Nitride Ceramics

This paper applies distinct element method (DEM) to simulate the material removal process of laser assisted machining of silicon nitride ceramics and show the formation and propagation of surface/sub-surface cracks and damage. A synthetic specimen is created using particle clusters to approximate the granular microstructure of β-type silicon nitride ceramics. The effect of temperature on machining is considered by its influence on the material properties. In addition, some other parameters such as rake angle, depth of cut, local damping coefficient and cluster size are also considered in a parametric study. It shows that all these parameters influence surface/sub-surface cracks and chip formation of silicon nitride ceramics in laser assisted machining.

Microstructural Modeling and Dynamic Process Simulation of Laser-Assisted Machining of Silicon Nitride Ceramics With Distinct Element Method

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Xinwei Shen ◽  
Budong Yang ◽  
Shuting Lei
Keyword(s):  
Silicon Nitride ◽  
Dynamic Process ◽  
Distinct Element ◽  
Subsurface Damage ◽  
Distinct Element Method ◽  
Laser Assisted Machining ◽  
Nitride Ceramics ◽  
Chip Size ◽  
Distinct Element Code ◽  
Element Method

The distinct element method (or discrete element method, DEM) is applied to simulate the dynamic process of laser-assisted machining (LAM) of silicon nitride ceramics. This is motivated by the fact that LAM of ceramics shows a few complicated characteristics such as spontaneous crack formation, discontinuous chips, etc. Thus, using the two-dimensional distinct element code, PFC2D, the microstructure of a β-type silicon nitride ceramic is modeled, and the resulting temperature-dependent synthetic specimens are created first, and then, machining simulations are conducted. The DEM model is validated through comparing the predicted results with those from the experiments under different cutting temperatures in terms of cutting force, chip size, and depth of subsurface damage. Furthermore, the mechanisms of LAM are analyzed from the aspects of material removal, chip segments, surface/subsurface damage, as well as crack initiation, propagation, and coalescence.

Cutting Simulation of Laser Assisted Milling of Silicon Nitride Ceramics Using PFC2D

2009 ◽  
Author(s):  
Xinwei Shen ◽  
Shuting Lei
Keyword(s):  
Silicon Nitride ◽  
Distinct Element ◽  
Cutting Temperature ◽  
Two Dimensions ◽  
Particle Flow Code ◽  
Temperature Dependent ◽  
Cutting Simulation ◽  
Nitride Ceramics ◽  
Ceramic Machining ◽  
Distinct Element Code

Since laser assisted milling (LAMill) exhibits complicated characteristics in ceramic machining, this paper applies a distinct-element code, PFC2D (Particle Flow Code in Two-Dimensions), to conduct cutting simulation of laser assisted slab milling and explore its machining mechanism. The microstructure of a β-type silicon nitride ceramic (β-Si3N4) is modeled at grain scale. Clusters are used to simulate the rod-like grains of β-Si3N4. Parallel bonds are employed to represent the connection between intergranular glass phase and grains. A temperature-dependent PFC specimen is created for simulation of LAMill. A special milling cutter is designed for improving the computing efficiency. Simulation results show that the cutting force is strongly related to crack formation and propagation. The specific cutting energy decreases as the cutting temperature increases.

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.

scholarly journals Effect of temperature on dielectric response in X-band of silicon nitride ceramics prepared by gelcasting

AIP Advances ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 075127 ◽  
Author(s):  
Shiyu Shao ◽  
Heng Luo ◽  
Lianwen Deng ◽  
Jun He ◽  
Shengxiang Huang
Keyword(s):  
Silicon Nitride ◽  
Dielectric Response ◽  
Effect Of Temperature ◽  
X Band ◽  
Nitride Ceramics

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.

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