Waterjet Machining and Peening of Metals | Part 4 Summary and Conclusions

Summary and Conclusions

An experimental study was conducted to determine the influence of material properties on the surface integrity and texture in WJ and AWJ machining of metals. Based on experiment, it can be
concluded that waterjet peening with high-pressure jet is capable of inducing surface/subsurface work hardening. The resulting compressive residual stresses were comparable to those introduced by shot peening. Both hardening and residual stresses were
functions of jet pressure and standoff distance. High-pressure water in some conditions was found to create pitlike surfaces, resulting in an increase in the surface roughness and possible subsurface damage.

Mechanisms of material removal below the initial damage zone in AWJ machining of both ductile and brittle materials do not change with cutting depth of cutting parameters, despite the distinct macro-features observed. AWJ cutting parameters influence the macro-features of the machined surface only due to their effect on jet energy. Subsurface deformation and strain hardening occurred in AWJ machining of the metals. The extent of deformation
was found to depend on the metal strain-hardening behavior and the abrasive attack angle. The largest degree of deformation occurred within the IDR due to the large abrasive attack angles at
jet impingement. Below the initial damage region, only minimal subsurface deformation was noted from hardness measurements and micro-structural analysis. The lack of deformation within the SCR and RCR results from the shallow abrasive attack angles within these regions. No differences in subsurface hardening were apparent between the SCR and RCR.

Acknowledgments
The authors are grateful to the National Science Foundation and Washington Technology Center for financial support.

References
@1# Hamatani, G., and Ramulu, M., 1990, ‘‘Machinability of High Temperature Composites by Abrasive Waterjet,’’ ASME J. Eng. Mat. Technol., 112, pp. 381–386.
@2# Ramulu, M., and Arola, D., 1993, ‘‘Waterjet and Abrasive Waterjet Cutting of Unidirectional Graphite/Epoxy Composite,’’ Composites, 24, No. 4, pp. 299–308.
@3# Hashish, M., 1984, ‘‘A Modeling Study of Metal Cutting with Abrasive Waterjets,’’ ASME J. Eng. Mater. Technol., 106, pp. 88–100.
@4# Hashish, M., 1989, ‘‘Machining of Advanced Composites with Abrasive Waterjets,’’ Manufac. Rev., 2, No. 2, pp. 142–150.
@5# Hashish, M., 1991, ‘‘Characteristics of Surfaces Machined with Abrasive Waterjets,’’ ASME J. Eng. Mater. Technol., 113, pp. 354–362.
@6# Finnie, I., 1958, ‘‘The Mechanism of Erosion of Ductile Metals,’’ Proceedings, Third National Congress of Applied Mechanics, ASME, New York, pp. 527–532.
@7# Bitter, J. G. A., 1963, ‘‘A Study of Erosion Phenomenon: Part I,’’ Wear, 6, pp. 5–21.
@8# Bitter, J. G. A., 1963, ‘‘A Study of Erosion Phenomenon: Part II,’’ Wear, 6, pp. 169–190.
@9# Arola, D., and Ramulu, M., 1993, ‘‘Mechanism of Material Removal in Abrasive Waterjet Machining in two Commonly used Aerospace Material,’’ Proceedings, 7th American Water Jet Conference, WJTA, St. Louis, MO, 1, pp. 43–64.
@10# Arola, D., and Ramulu, M., 1993, ‘‘Micro-Mechanisms of Material Removal in Abrasive Waterjet Machining,’’ Processing of Advanced Materials, 4, pp. 37–47.
@11# Arola, D., and Ramulu, M., 1995, ‘‘Abrasive Waterjet Machining of Titanium Alloy,’’ Proceedings, 8th American Waterjet Conference, WJTA, St. Louis, MO, 1, pp. 389–408.
@12# Arola, D., and Ramulu, M., 1996, ‘‘A Residual Stress Analysis of Metals Machined with the Abrasive Waterjet,’’ Proceedings, Symposium on Jetting Technology, BHRA Group, UK, pp. 269–290.
@13# Arola, D., and Ramulu, M., 1997, ‘‘Material Removal in Abrasive Waterjet Machining of Metals, Surface Integrity and Texture,’’ Wear, 210, No. 2, pp. 50–58.
@14# Arola, D., and Ramulu, M., 1997, ‘‘Material Removal in Abrasive Waterjet Machining of Metals, A Residual Stress Analysis,’’ Wear, 211, No. 2, pp. 302–310.
@15# Burnham, C. D., and Kim, T. J., 1989, ‘‘Statistical Characterization of Surface Finish Produced by a High Pressure Abrasive Waterjet,’’ Proceedings, 5th American Waterjet Conference, WJTA, pp. 165–175.
@16# Ross, R. B., 1980, Metallic Materials Specification Handbook, 3rd Edition, Chapman and Hall Publ. Ltd., UK.
@17# Metals Handbook, 1972, 8th Edition, Atlas of Microstructures of Industrial Alloys, Vol. 7, ASM, Columbus, OH.
@18# Kruszynski, B. W., and Van Luttervelt, K. A., 1989, ‘‘The Influence of Manufacturing Processes on Surface Properties,’’ Adv. Manufact. Eng., 1, pp. 30–38.
@19# Noyan, I. C., and Conen, J. B., 1987, Residual Stress: Measurement by Diffraction and Interpretation, Springer, Germany.
@20# Was, G. S., Pelloux, R. M., and Frabolot, M. C., 1981, ‘‘Effect of Shot Peening Methods on The Fatigue Behavior of Alloy 7075-T6,’’ Proceedings, First International Conference on Shot Peening, Pagamon Press Ltd., pp. 445–451.

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