Laser shock processing of copper using focused laser beam size about ten microns is investigated for its feasibility and capability to impart desirable residual stress distributions into the target material in order to improve the fatigue life of the material. Shock pressure and strain/stress are properly modeled to reflect the micro scale involved, and the high strain rate and ultrahigh pressure involved. Numerical solutions of the model are experimentally validated in terms of the geometry of the shock-generated plastic deformation on target material surfaces as well as the average in-depth strains under various conditions. The residual stress distributions can be further influenced by shocking at different locations with certain spacing. The potential of applying the technique to micro components, such as micro gears fabricated using MEMS is demonstrated. The investigation also lays groundwork for possible combination of the micro scale laser shock processing with laser micromachining processes to offset the undesirable residual stress often induced by such machining processes.

Issue Section:
Technical Papers
Keywords:
laser materials processing, shock wave effects, copper, high-pressure effects, laser beam effects, plastic deformation, laser beam machining
Topics:
Copper, Lasers, Shock (Mechanics), Pressure, Laser hardening, Stress, X-ray diffraction, Simulation, Deformation, Geometry, Laser beams
1.
White
,
R. M.
,
1963
, “
Elastic Wave Generation by Electron Bombardment or Electromagnetic Wave Absorption
,”
J. Appl. Phys.
,
34
, pp.
2123
–
2124
.
2.
Clauer, A. H., and Holbrook, J. H., 1981, “Effects of Laser Induced Shock Waves on Metals,” Shock Waves and High Strain Phenomena in Metals-Concepts and Applications, New York, Plenum, pp. 675–702.
3.
Peyre
,
P.
,
Scherpereel
,
X.
,
Berthe
,
L.
, and
Fabbro
,
R.
,
1998
, “
Current Trends in Laser Shock Processing
,”
Surf. Eng.
,
14
, No.
5
, pp.
377
–
380
.
4.
Walraven, J. A., Mani, S. S., Fleming, J. G., Headley, T. J., Kotula, P. G., Pimentel, A. A., Rye, M. J., Tanner, D. M., and Smith, N. F., 2000, “Failure Analysis of Tungsten Coated Polysilicon Micromachined Microengines,” MEMS Reliability for Critical Applications, Proceedings of SPIE, Vol. 4180, pp. 49–57.
5.
Frederick, Kevin M., and Fedder, Gary K., 2000, “Mechanical Effects of Fatigue and Charge on CMOS MEMS,” MEMS Reliability for Critical Applications, Proceedings of SPIE, Vol. 4180, pp. 108–116.
6.
Fox
,
J. A.
,
1974
, “
Effect of Water and Paint Coatings on Laser-Irradiated Targets
,”
Appl. Phys. Lett.
,
24
, No.
10
, pp.
461
–
464
.
7.
Fabbro
,
R.
,
Fournier
,
J.
,
Ballard
,
P.
,
Devaux
,
D.
, and
Virmont
,
J.
,
1990
, “
Physical Study of Laser-Produced Plasma in Confined Geometry
,”
J. Appl. Phys.
,
68
, No.
2
, pp.
775
–
784
.
8.
Peyre
,
P.
,
Fabbro
,
R.
,
Berthe
,
L.
, and
Dubouchet
,
C.
,
1996
, “
Laser Shock Processing of Materials, Physical Processes Involved and Examples of Applications
,”
J. Laser Appl.
,
8
, pp.
135
–
141
.
9.
Assay, James R., and Shahipoor, Mohsen, 1992, High-Pressure Shock Compression of Solids, New York, Springer-Verlag, pp. 78–82.
10.
Meyer, L. W., 1992, “Constitutive Equations at High Strain Rates,” Shock-wave and High-Strain-Rate Phenomena in Metals, Marcel Dekker, Inc., New York, pp. 49–68.
11.
Johnson
,
G. R.
,
Hoegfeldt
,
J. M.
,
Lindholm
,
U. S.
, and
Nagy
,
A.
,
1983
, “
Response of Various Metals to Large Torsional Strain Over a Large Range of Strain Rates
,”
J. Eng. Mater. Technol.
,
105
, pp.
42
–
53
.
12.
Steinberg
,
D. J.
,
Cochran
,
S. G.
, and
Guinan
,
M. W.
,
1980
, “
A Constitutive Model for Metals Applicable at High-Strain Rate
,”
J. Appl. Phys.
,
51
, No.
3
, pp.
1498
–
1504
.
13.
Noyan, I. C., and Cohen, J. B, 1986, Residual Stress, Springer-Verlag New York, Inc., New York, pp. 135.
Copyright © 2002
 by ASME
You do not currently have access to this content.