Pulsed lasers are used in a variety of materials processing applications that range from heating for metallurgical transformation to scribing vehicle identification numbers on anodized aluminum strips. These lasers are commonly configured to deliver a large quantity of heat energy in very short time intervals and over very small areas due to the manner in which radiant energy is stored within, and then released from, the laser resonator. At the present time, little is known about the effect of pulse duration on thermomechanical distortion during heating without phase change. To explore this issue, a boundary element method was developed to calculate temperature, displacement, and thermal stress fields in a layer that is rigidly bonded to an inert semi-space. The layer absorbs thermal energy from a repetitively pulsed laser in the plane of its free surface. The effects of two pulse durations, which differ by four-orders-of-magnitude, were examined in this work. The temporal profiles of ultrafast pulses of the order of ten picoseconds (such as those emitted by a mode-locked laser), and pulses of the order of tens-of-nanoseconds (such as those emitted by a Q-switched Nd:YAG laser) were mathematically modeled using a rectified sine function. The spatial profile of each pulse was shaped to approximate a Gaussian strip source. The equations of coupled thermoelasticity, wherein the speed of mechanical distortion due to material expansion during heat absorption is finite, but the speed of heat propagation within the layer is infinite, were solved for both pulse durations. The resulting temperature and stress fields were compared with those predicted in the limit of no thermomechanical coupling.

Issue Section:
Technical Papers
Keywords:
thermal stresses, heat treatment, boundary-elements methods, thermoelasticity, laser beam effects, thermal expansion
Topics:
Boundary element methods, Displacement, Heat, Heating, Lasers, Stress, Temperature, Thermal stresses, Thermoelasticity, Absorption, Trains, Thermomechanics
1.
Maiman
,
T. H.
,
1960
, “
Stimulated Optical Radiation in Ruby
,”
Nature (London)
,
187
, p.
493
493
.
2.
Yamawaki
,
H.
, and
Saito
,
T.
,
1992
, “
Computer Simulation of Laser-Generated Elastic Waves in Solids
,”
Nondestr. Test. Eval.
,
7
, pp.
165
–
177
.
3.
Qui
,
T.
,
Tien
,
C.-L.
,
Shannon
,
M. A.
, and
Russo
,
R. E.
,
1994
, “
Thermal and Mechanical Responses of Gold Films During Nanosecond Laser-Pulse Heating
,”
Exp. Heat Transfer
,
7
, pp.
175
–
188
.
4.
Zhou
,
Y. C.
,
Duan
,
Z. P.
, and
Yang
,
Q. B.
,
1998
, “
Failure of SiC Particulate-Reinforced Metal Matrix Composites Induced by Laser Thermal Shock
,”
Metall. Mater. Trans. A
,
29A
, pp.
685
–
692
.
5.
Mortia
,
N.
,
Watanabe
,
T.
, and
Yoshida
,
Y.
,
1991
, “
Crack-Free Processing of Hot-Pressed Silicon Nitride Ceramics Using Pulsed YAG Laser
,”
JSME Int. J., Ser. III
,
34
, pp.
149
–
153
.
6.
Kostrubiec
,
F.
, and
Walczak
,
M.
,
1994
, “
Thermal Stresses in the Tungsten and Molybdenum Surface Layer Following Laser Treatment
,”
J. Mater. Sci. Lett.
,
13
, pp.
34
–
36
.
7.
Masse
,
J.-E.
, and
Barreau
,
G.
,
1993
, “
Residual Stresses in Steel by Laser Shock Treatment
,”
C. R. Acad. Sci., Ser. II: Mec., Phys., Chim., Sci. Terre Univers
,
317
, pp.
1015
–
1018
.
8.
Ashby
,
M. F.
, and
Easterling
,
K. E.
,
1984
, “
The Transformation Hardening of Steel Surfaces by Laser Beams—I. Hypo-eutectoid Steels
,”
Acta Metall.
,
32
, pp.
1935
–
1948
.
9.
Welsh
,
L. P.
,
Tuchman
,
J. A.
, and
Herman
,
J. P.
,
1988
, “
The Importance of Thermal Stresses and Strains Induced in Laser Processing with Focused Gaussian Beams
,”
J. Appl. Phys.
,
64
, pp.
6274
–
6286
.
10.
Uglov
,
A. A.
,
Kulik
,
A. N.
,
Makorkin
,
I. N.
, and
Senik
,
A. P.
,
1994
, “
On the Calculation of Metallic Cylinder Thermal Stressed State Under Periodic Pulsed Laser Heating
,”
Fiz. Khim. Obrab. Mater.
,
4
, pp.
12
–
18
(in Russian).
11.
Germanovich
,
L. N.
,
Kill
,
I. D.
, and
Tsodokova
,
N. S.
,
1988
, “
Thermoelastic Stresses in a Half-Space Heated by Concentrated Energy Flux
,”
Appl. Math. Mech.
,
52
, pp.
525
–
533
(in Russian).
12.
Suh
,
C. S.
, and
Burger
,
C. P.
,
1998
, “
Thermoelastic Modeling of Laser-Induced Stress Waves in Plates
,”
J. Therm. Stresses
,
21
, pp.
829
–
847
.
13.
Cohen
,
S. S.
,
Bernstein
,
J. B.
, and
Wyatt
,
P. W.
,
1992
, “
The Effect of Multiple Laser Pulses on Damage to Thin Metallic Films
,”
J. Appl. Phys.
,
71
, pp.
630
–
637
.
14.
Fesenko
,
V. M.
,
1995
, “
Thermal-Stressed State of a Tetragonal Symmetry Crystal Under the Laser Radiation Effect
,”
Inzh.-Fiz. Zh.
,
68
, pp.
160
–
161
(in Russian).
15.
Hector
, Jr.,
L. G.
, and
Hetnarski
,
R. B.
,
1996
, “
Thermal Stresses Due to a Laser Pulse: Elastic Solution
,”
ASME J. Appl. Mech.
,
63
, pp.
38
–
46
.
16.
Kim
,
W. S.
,
Hector
, Jr.,
L. G.
, and
Hetnarski
,
R. B.
,
1997
, “
Thermoelastic Stresses in a Bonded Layer Due to Repetitively Pulsed Laser Radiation
,”
Acta Mech.
,
125
, pp.
107
–
128
.
17.
Tehrani
,
P. H.
, and
Eslami
,
M. R.
,
1998
, “
Two-Dimensional Time Harmonic Dynamic Coupled Thermoelasticity Analysis by BEM Formulation
,”
Eng. Anal. Boundary Elem.
,
22
, pp.
245
–
250
.
18.
Nowacki, W., 1986, Thermoelasticity, 2nd ed., Pergamon, New York.
19.
Nowacki, W., 1975, Dynamics Problems of Thermoelasticity, P. H. Francis and R. B. Hetnarski, eds., Noordhoff International Publishers, Leyden.
20.
Timoshenko, S. P., and Goodier, J. N., 1970, Theory of Elasticity, 3rd ed., McGraw-Hill, New York.
21.
Hector
, Jr.,
L. G.
,
Kim
,
W.-S.
, and
Ozisik
,
M. N.
,
1992
, “
Propagation and Reflection of Thermal Waves in a Finite Medium Due to Axisymmetric Surface Sources
,”
Int. J. Heat Mass Transf.
,
35
, pp.
897
–
912
.
22.
Chandrasekaraiah
,
D. S.
,
1989
, “
Thermoelasticity With Second Sound: A Review
,”
Appl. Mech. Rev.
,
39
, pp.
355
–
376
.
23.
Sparks
,
M.
,
1976
, “
Theory of Laser Heating of Solids
,”
J. Appl. Phys.
,
47
, pp.
837
–
849
.
24.
Hector
, Jr.,
L. G.
,
Kim
,
W.-S.
, and
Osizik
,
M. N.
,
1992
, “
Hyperbolic Heat Conduction due to a Mode Locked Laser Pulse Train
,”
Int. J. Eng. Sci.
,
30
, pp.
1731
–
1744
.
25.
Koechner, W., 1991, Solid State Laser Engineering, 2nd ed., Springer-Verlag, New York.
26.
Hecht, J., 1992, The Laser Guidebook, 2nd ed., McGraw-Hill, New York.
27.
Lim
,
G. C.
,
1982
, “
Measurement of the Temporal and Spatial Power Distribution of a High-Power CO2 Laser Beam
,”
Opt. Laser Technol.
,
14
, pp.
149
–
153
.
28.
Steen, W. M., 1991, Laser Material Processing, Springer-Verlag, New York.
29.
Dominguez, J., 1993, Boundary Elements in Dynamics, Computational Mech., Boston.
30.
Watson, G. N., 1966, A Treatise on the Theory of Bessel Functions, Cambridge University Press, New York.
31.
Brebbia, C. A., Telles, J. C. F., and Wrobel, L. C., 1984, Boundary Element Techniques, Springer-Verlag, New York.
32.
Durbin
,
F.
,
1974
, “
Numerical Inversion of Laplace Transforms: An Efficient Improvement to Dubner and Abate’s Method
,”
Comput. J.
,
17
, pp.
371
–
376
.
33.
Incropera, F. P., and DeWitt, D. P., 1981, Fundamentals of Heat Transfer, John Wiley and Sons, New York.
34.
Apollonov
,
V. V.
,
Barchukhov
,
A. I.
,
Prokhorov
,
A. M.
,
1972
, “
Thermoelastic Deformations of a Solid Surface by a Laser Beam
,”
JETP Lett.
,
15
, pp.
172
–
174
.
35.
Nonhof, C. J., 1988, Materials Processing With Nd with Nd-Lasers, Electrochemical Publications Ltd., Ayr, Scotland.
36.
Powell, J., 1993, CO2 Laser Cutting, Springer-Verlag, New York.
37.
Wefers, K., and Misra, C., 1987, “Oxides and Hydroxides of Aluminum,” Alcoa Technical Paper No. 19, Revised. Alcoa Technical Center, Alcoa Center, PA.
38.
Krokhin, O., 1972, “Generation of High Temperature Vapors and Plasmas by Laser Radiation,” Laser Handbook, F. T. Arrechi, and E. O. Schulz-Dubois, eds., North-Holland, Amsterdam, Chapter 2.
39.
Zehr, R. L., 1991, “Thermocapillary Convection in Laser Melted Pools During Material Processing,” Ph.D. thesis, Mechanical Engineering Department, University of Illinois at Urbana-Champaign, University of Microfilms International, Ann Arbor, MI.
40.
Hector
, Jr.,
L. G.
, and
Sheu
,
S.
,
1993
, “
Focused Energy Beam Work Roll Surface Texturing Science and Technology
,”
J. Mater. Process. Manuf. Sci.
,
2
, pp.
63
–
117
.
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