Abstract

A micro-indent method is used to evaluate different residual stress states, which were generated in samples of AA 7075-T6 aluminium alloy milled at low, medium and high speed. The milling tests were carried out in order to introduce, in each new surface, two different zones from asymmetries in the orientation of the cutting edge. The results obtained in samples subjected to different combinations of process parameters reveal, in both cutting zones, compressive normal components regardless of the evaluated direction. This study includes a comprehensive analysis of the medium normal component of residual stress. This component is the most representative of the stress tensor since it is independent of the diameter of the stress circle, commonly denominated Mohr's circle. In addition, this component is associated to those directions where tangential components reach their maximum. From the sensitivity of the used method, it was possible to detect differences generated between the levels reached by the medium component in the evaluated zones. It is noteworthy that the detected differences are independent of the cutting speed and feed rate. This significant fact, finally, would indicate similar differences in the combination of local plastic deformation and heat conducted to the new surface between both cutting zones, which is valid for different combinations of process parameters evaluated in this study.

Keywords:

Aluminium alloy, indent method, milling, mohr's circle, residual stresses,

References

1. Abrão, A.M., J. Silva Ribeiro and J. Paulo Davim, 2011. Surface Integrity. In: Paulo Davim, J. (Ed.), Machining of Hard Materials. Springer-Verlag, London, pp: 115-141.
   CrossRef    
2. Brinksmeier, E., 1987. Residual stresses in hard metal cutting. Residual Stresses Sci. Technol., 2: 839-847.
   
3. Brinksmeier, E., J.T. Cammett, W. König, P. Leskovar, J. Peters and H.K. Tönshoff, 1982. Residual stresses-measurement and causes in machining processes. Ann. CIRP, 31: 491-510.
   CrossRef    
4. Capello, E., 2005. Residual stresses in turning. Part I: Influence of process parameters. J. Mater. Process. Tech., 160: 221-228.
   CrossRef    
5. Curtis, M.A. and F.T. Farago, 1994. Handbook of Dimensional Measurement. Industrial Press Inc., New York.
   
6. Díaz, F.V. and C. Mammana, 2012. Study of Residual Stresses in Conventional and High-speed Milling. In: Filipovic, L. (Ed.), Milling: Operations, Applications and Industrial Effects. Nova Science Publishers Inc., New York, pp: 127-155.
   
7. Díaz, F.V., R. Bolmaro, A. Guidobono and E. Girini, 2010. Determination of residual stresses in high speed milled aluminium alloys using a method of indent pairs. Exp. Mech., 50: 205-215.
   CrossRef    
8. Díaz, F.V., C. Mammana and A. Guidobono, 2012. Evaluation of residual stresses induced by high speed milling using an indentation method. Modern Mech. Eng., 2: 143-150.
   CrossRef    
9. Dotson, C.L., R. Harlow and R. Thompson, 2003. Fundamentals of Dimensional Metrology. 5th Edn., Thompson Delmar Learning, New York.
   
10. Fuh, K.H. and C. Wu, 1995. A residual stress model for the milling of aluminium alloy (2014-T6). J. Mater. Process. Tech., 51: 87-105.
    CrossRef    
11. Gere, J.M., 2001. Mechanics of Materials. 5th Edn., Brooks/Cole, Pacific Grove, CA.
    PMCid:PMC4781630    
12. Henriksen, E.K., 1951. Residual stress in machined surfaces. Trans. ASME, 73: 265-278.
    
13. Jacobus, K., S.G. Kapoor and R.E. DeVor, 2001. Experimentation on the residual stresses generated by endmilling. J. Manuf. Sci. E-T. ASME, 123: 748-753.
    CrossRef    
14. Mammana, C.A., F. Díaz, A. Guidobono and R. Bolmaro, 2010. Study of residual stress tensors in high-speed milled specimens of aluminium alloys using a method of indent pairs. Res. J. Appl. Sci. Eng. Technol., 2: 749-756.
    Direct Link
15. Mao, W., 2003. Recrystallization and Grain Growth. In: Totten, G.E. and D. MacKenzie, (Eds.), Handbook of Aluminum. Physical Metallurgy and Processes. Marcel Dekker Inc., New York, 1: 211-258.
    CrossRef    
16. Özel, T. and E. Zeren, 2004. Determination of flow material stress and friction for FEA of machining using orthogonal cutting tests. J. Mater. Process. Tech., 153: 1019-1025.
    CrossRef    
17. Schwach, D.W. and Y. Guo, 2006. A fundamental study on the impact of surface integrity by hard turning on rolling contact fatigue. Int. J. Fatigue, 28: 1838-1844.
    CrossRef    
18. Withers, P.J., 2007. Residual stress and its role in failure. Rep. Prog. Phys., 70: 2211-2264.
    CrossRef    
19. Wyatt, J.E. and J. Berry, 2006. A new technique for the determination of superficial residual stresses associated with machining and other manufacturing processes. J. Mater. Process. Tech., 171: 132-140.
    CrossRef    

Competing interests

The authors have no competing interests.

Open Access Policy

This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Copyright

The authors have no competing interests.