A series of experiments were conducted to determine the influence of workpiece thickness, cutting speed, and beam power on the onset of fracture in aluminum oxide (Al2O3) during continuous wave CO2 laser cutting. Samples of Coors AD-96 substrate of thickness 0.040, 0.050, and 0.080 in. thick, respectively, were cut at combinations of feed rates and power levels to determine the conditions at which fracture of this ceramic occurs with respect to these two parameters. Plots of the lowest value of feed rate producing a fracture-free cut at a given power were constructed for each material thickness.

To explain the results qualitatively, a simplified thermal analysis of the problem was conducted. The two-dimensional temperature field resulting from a moving line source was calculated analytically to determine the maximum temperature gradient expected in the workpiece as a function of power and feedrate. A similar numerical computation was carried out for a moving distributed cylindrical source, to simulate a laser spot, accounting in addition for the variation of thermal conductivity of the workpiece with temperature. Both models successfully predicted the trends observed in the experimental study where increasing feedrates at a given power and workpiece thickness resulted in increasing temperature gradients while decreasing power ata given feedrate and workpiece thickness resulted in increasing temperature gradients.

Topics
Thermal conductivity, Thermodynamic states and processes, Laser cutting, Solid state lasers, Oxides, Thermal analysis, Ceramics
1.
Lumley
,
R.M.
 (
1969
), “
Controlled Separation of Brittle Materials Using a Laser
,”
Amer. Ceramics Soc. Bull
.
48
:
850
–
854
.
Google Scholar
 
2.
Morita
,
N.
,
S.
Isshida
,
Y.
Fujimori
, and
K.
Ishikawa
 (
1988
), “
Pulsed Laser Processing of Ceramics in Water
,”
Appl. Phys. Lett
.
52
:
1965
–
1966
.
https://doi.org/10.1063/1.99591
Google Scholar
Crossref
Search ADS
 
3.
Lynch
,
J.F.
,
C.G.
Ruderer
, and
W.H.
Duckworth
 (
1966
),
Engineering Properties of Selected Ceramic Materials
,”
The American Ceramics Society
,
Ohio
, pp.
5.4.0
–
1-27
.
Google Scholar
 
4.
Satyamurthy
,
K.
Singh
,
J.P.
,
D.P.H.
Hasselman
, and
M.P.
Kamat
 (
1980
), “
Effect of Spatially Varying Thermal Conductivity on the Magnitude of Thermal Stress in Brittle Ceramics Subjected to Convective Heating
,”
J. Amer. Ceramic Soc
.
63
:
363
–
367
.
https://doi.org/10.1111/j.1151-2916.1980.tb10193.x
Google Scholar
Crossref
Search ADS
 
5.
Kingery
,
W.D.
 (
1955
), “
Factors Affecting Thermal Stress Resistance of Ceramic Materials
,”
J. Amer. Ceramic Soc
.
38
:
3
–
15
.
https://doi.org/10.1111/j.1151-2916.1955.tb14545.x
Google Scholar
Crossref
Search ADS
 
6.
Hasselman
,
D.P.H.
 (
1970
), “
Thermal Stress Resistance Parameters for Brittle Refractory Ceramics: A Copmpendium
,”
Ceramics Bull
.
49
:
1033
–
1037
Google Scholar
 
7.
Carslaw
,
H.S.
 and
J.C.
Jeager
 (
1959
),
Conduction of Heat in Solids
,
Clarendon Press
,
Oxford
.
Google Scholar
 
8.
Gonsalves
,
J.N.
 and
W.W.
Duley
, (
1972
), “
Cutting Thin Metal Sheets with the CW CO2 Laser
,”
J AppI. Phys
.
43
:
4684
–
4687
.
https://doi.org/10.1063/1.1660989
Google Scholar
Crossref
Search ADS
 
9.
Bunting
,
K.A.
 and
G.
Cornfield
 (
1975
), “
Toward a General Theory of Cutting: A Relationship Between the Incident Power Density and the Cut Speed
”,
ASME J. Heat Transfer
97
:
116
–
122
.
https://doi.org/10.1115/1.3450258
Google Scholar
Crossref
Search ADS
 
10.
Cline
,
H.E.
 and
T.R.
Anthony
 (
1977
), “
Heat Treating and Melting Material with Scanning Laser or Electron Beam
”,
J. Appl. Phys
.
48
:
3895
–
3900
.
https://doi.org/10.1063/1.324261
Google Scholar
Crossref
Search ADS
 
11.
Modest
,
M.F.
 and
H.
Abrakians
 (
1986
), “
Heat Conduction in a Moving Semi-infinite Solid Subjected to Pulsed Laser Irradiation
,”
ASME J. Heat Transfer
108
:
116
–
122
.
Google Scholar
 
12.
Ramanathan
,
S.
 and
Modest
,
M.F.
, (
1990
), “Effects of Variable Thermal Properties on Evaporative Cutting with a Moving CW Laser,”
Heat Transfer in Space Systems, ASME HTD-135
,
ASME
,
New York
,
101
–
108
.
Google Scholar
 
13.
Mazumder
,
J.
 and
W.M.
Steen
 (
1980
), “
Heat Transfer Model for CW Laser Material Processing
,”
J. AppI. Phys
.
51
:
941
–
947
.
https://doi.org/10.1063/1.327672
Google Scholar
Crossref
Search ADS
 
14.
Surprenant
,
R.P.
 (
1991
), “Fracture Characteristics of an Aluminum Oxide Ceramic During Continuous Wave CO2 Laser Cutting,” M.S. Thesis,
Rensselaer Polytechnic Institute
,
Troy, NY
.
15.
Neimeyer
,
R.
,
R.N.
Smith
 and
D.A.
Kaminski
 (
1990
), “Effects of Operating Parameters on Surface Quality for Laser Cutting of Mild Steel,”
Fundamental Issues in Machining
,
B.E.
Klamecki
 and
K.J.
Weinmann
, Editors, ASME PED-Vol.
43
,
ASME
,
New York
,
337
–
346
.
Google Scholar
 
16.
Patankar
,
S.V.
 (
1980
),
Numerical Heat Transfer and Fluid Flow
,
Hemisphere Publishing Corp.
,
New York
,
79
–
105
.
Google Scholar
 
This content is only available via PDF.
© 1992 Laser Institute of America.
1992
Laser Institute of America
You do not currently have access to this content.