Numerical Simulations of an Active-Stressing Technique for Delaying Fracture During Cutting of Alumina

[+] Author and Article Information
R. Akarapu

Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802

A. E. Segall

Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802aesegall@psu.edu

J. Manuf. Sci. Eng 128(4), 921-927 (Mar 02, 2006) (7 pages) doi:10.1115/1.2335849 History: Received July 26, 2005; Revised March 02, 2006

During a variety of high-speed cutting operations that can include both laser and traditional saw methods, full workpiece support is not always practical or even possible. As a result, costly premature fractures and associated damage such as chips, burrs, and cracks (ranging from the micro- all the way to the macroscale) can result. In most instances, the resulting stresses are primarily mechanical in nature and arise from the bending and/or twisting moments from the still attached scrap. Under these conditions, mixed-mode fracture is all but inevitable since the supporting section is continuously diminishing as the cut progresses. Given the predominantly mechanical, and therefore predictable, nature of the resulting stresses, it is conceivable that intentionally induced, compressive stresses due to an off-focus laser might be used to control (or at least, delay) such fractures. In this paper, the possibility of using a tailored laser-heating scenario ahead of a progressing cut to “actively” induce compressive thermal stresses to control fracture of a cantilevered plate was numerically investigated. A simulation of this active-stressing approach was achieved by using a customized finite-element formulation that was previously employed to model dual-beam laser machining. However, in this instance probabilistic fracture mechanics was used to quantify the influence of the induced compressive stresses on the time and nature of the fracture. The effect of important parameters such as CO2 beam diameter, incident power density, positioning of the laser with respect to cut, as well as timing were then studied with respect to the goal of reducing and/or delaying the likelihood of fracture.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Plate and cut geometry with coordinate system

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Figure 2

Typical temperature profiles (Celsius) acting at the cut front during active stressing

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Figure 3

Typical crack-opening principal (σ22) stresses in Pascals acting at cut front

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Figure 4

Simulated surface failure probabilities in the region of the cutting front

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Figure 5

Effect of laser diameter on probability of fracture (power=10W, x=0, and y∕L=0.9)

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Figure 6

Effect of power of laser on probability of fracture (diameter=15mm, x=0, and y∕L=0.9)

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Figure 7

Effect of active-stressing beam location on the probability of fracture (power=10W, diameter=3mm)

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Figure 8

Advantageous effects of simultaneous surface laser heating or active stressing on the overall fracture probability



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