This study presents a novel method for estimating the surface integrity of end-milled workpieces. It is well known that the mechanical properties of machined surfaces in cutting affect the quality of the final product. In particular, hardness and residual stress often require strict control; however, nondestructive inspection remains a challenge. This study proposes a method to estimate the hardness and residual stress of end-milled surfaces by analyzing cutting forces and images of the tool during machining to obtain approximate temperature and stress distributions. These state quantities are highly correlated with the dislocation density and its distribution on the machined surface, which in turn is strongly correlated with residual stress and surface hardness. Despite this strong correlation, few research studies have been conducted on the topic. In the proposed method, cutting forces, measured by a dynamometer, are analyzed to estimate the specific cutting forces and edge force coefficients. Simultaneously, the flank wear width is recorded using an image-based on-machine measuring device installed in the machine tool. From this information, the average stresses at the primary and tertiary cutting zones are estimated, while the cutting temperature in the primary cutting zone is roughly estimated by considering the traditional shear-angle prediction theory. Using these estimations, hardness and residual stress are calculated based on a simple linear regression model. Parameter identification for the model is performed based on measured hardness and residual stress in end-milling experiments. The model was validated against experimental measurements, which showed that the proposed method can accurately estimate hardness and residual stress, although it was observed that the selection of explanatory variables has a significant effect on accuracy.

1. [1] M. F. Garwood, H. H. Zurburg, and M. A. Erickson, “Correlation of laboratory tests and service performance, interpretation of tests and correlation with service,” American Society for Metals, pp. 1-77, 1951.
2. [2] P. G. Forrest, “Fatigue of metals,” Pergamon Press, 1962.
3. [3] H. Sasahara, “The effect on fatigue life of residual stress and surface hardness resulting from different cutting conditions of 0.45%C steel,” Int. J. of Machine Tools and Manufacture, Vol.45, Issue 2, pp. 131-136, 2005. https://doi.org/10.1016/j.ijmachtools.2004.08.002
4. [4] E. K. Henriksen, “Residual stress in machined surface,” Trans. ASME, Vol.73, No.1, pp. 69-76, 1951.
5. [5] E. Brinksmeier, J. T. Cammett, W. Konig, P. Leskovar, J. Peters, and H. K. Jonshoff, “Residual stresses—measurement and causes in machining process,” CIRP Ann., Vol.31, Issue 2, pp. 491-509, 1982. https://doi.org/10.1016/S0007-8506(07)60172-3
6. [6] J. Yin et al., “Formation mechanism and annealing behavior of nanocrystalline ferrite in pure Fe fabricated by ball milling,” ISIJ Int., Vol.41, No.11, pp. 1389-1396, 2001. https://doi.org/10.2355/isijinternational.41.1389
7. [7] İ. Ucun and K. Aslantas, “Numerical simulation of orthogonal machining process using multilayer and single-layer coated tools,” Int. J. Adv. Manuf. Technol., Vol.54, Issue 9, pp. 899-910, 2011. https://doi.org/10.1007/s00170-010-3012-9
8. [8] Y. Ma, P. Feng, J. Zhang, Z. Wu, and D. Yu, “Prediction of surface residual stress after end milling based on cutting force and temperature,” J. of Materials Processing Technology, Vol.235, pp. 41-48, 2016. https://doi.org/10.1016/j.jmatprotec.2016.04.002
9. [9] X.-D. Huang, X.-M. Xhang, J. Leopold, and H. Ding, “Analytical model for prediction of residual stress in dynamin orthogonal cutting process,” J. Manuf. Sci. Eng., Vol.140, Issue 1, pp. 1-17, 2018. https://doi.org/10.1115/1.4037424
10. [10] Y. Altintas, “Manufacturing Automation: Metal Cutting Mechanics, Machine Tool Vibrations, and CNC Design,” Cambridge University Press, 2012.
11. [11] K. Takahei, S. Miwa, E. Shamoto, and N. Suzuki, “Parameter identification for linear model of the milling process using spindle speed variation,” Precision Engineering, Vol.79, pp. 16-33, 2023. https://doi.org/10.1016/j.precisioneng.2022.08.011
12. [12] E. Shamoto and Y. Altintas, “Prediction of shear angle in oblique cutting with maximum shear stress and minimum energy principles,” J. Manuf. Sci. Eng., Vol.121, No.3, pp. 399-407, 1999. https://doi.org/10.1115/1.2832695
13. [13] P. L. B. Oxley, “Mechanics of machining, an Analytical Approach to Assessing Machinability,” Ellis Horwood Limited, 1989.
14. [14] T. Özel and E. Zeren, “A methodology to determine work material flow stress and tool-chip interfacial friction properities by using analysis of machining,” J. Manuf. Sci. Eng., Vol.128, No.1, pp. 119-129, 2006. https://doi.org/10.1115/1.2118767
15. [15] ASM Handbook Committee, “ASM Handbook: Volume 15: Casting,” ASM Int., pp. 468-481, 2008.
16. [16] H. Ding and Y. Shin, “A metallo-thermo-mechanically coupled analysis of orthogonal cutting of AISI 1045 steel,” Proc. of the ASME 2012 Int. Manufacturing Science and Engineering Conf. MSEN 2012, June 4–8, Notre Dame, Indiana, USA, 2012. https://doi.org/10.1115/MSEC2012-7300
17. [17] T.-P. Hung, H.-E. Shi, and J.-H. Kuang, “Temperature modeling of AISI 1045 steel during surface hardening processes,” Materials, Vol.11, No.10, pp. 1815-1835, 2018. https://doi.org/10.3390/ma11101815