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Yayın Investigation of residual stresses induced by milling of compacted graphite iron by x-ray diffraction technique(Springer, 2024-04) Kara, Mehmet Emre; Kuzu, Ali Taner; Bakkal, MustafaThis study investigates the relationship between residual stresses, cutting parameters, and machining performance in the milling process of compacted graphite iron (CGI). X-ray diffraction (XRD) analysis is employed to measure residual stresses on the cast and milled surfaces, while cutting force modeling is utilized to calculate the tangential force, power, and active work. The results demonstrate that tensile residual stresses are predominant on the milled surfaces, attributed to the both mechanical and thermal loads generated during milling. By analyzing various cutting conditions, it is observed that lower feeds contribute to reduced plastic deformation, resulting in lower residual stress levels. Additionally, higher cutting speeds lead to higher temperatures, but due to the shorter machining time, heat accumulation is limited, resulting in higher residual stresses, especially at low feeds. At high feeds, residual stresses decreased as the cutting speed increased. The interplay between cutting parameters and residual stresses highlights the need for optimizing cutting conditions to enhance fatigue strength in CGI components. These findings provide valuable insights for process optimization and quality control in the milling of CGI materials.Yayın Investigation of residual stresses induced by turning of hot forged and heat treated AA7075(Springer Science and Business Media Deutschland GmbH, 2024-12) Tok, Görkem; Kuzu, Ali Taner; Bakkal, MustafaThis study investigates the impact of cutting parameters on residual stress in components made from AA7075 material, which were hot forged and subsequently subjected to T6 heat treatment. Using the Taguchi experimental design, two distinct cutting cases—face turning and circumferential turning—were devised to assess residual stress at different sections of the part. During the turning process, force measurements were conducted with a dynamometer, and residual stress was subsequently measured using the X-ray diffraction method. The results indicate that both mechanical and thermal loadings significantly influence residual stress. Notably, spindle speed has the most substantial effect on residual stress in both face turning and circumferential turning, with an observed increase of up to 30% and 20%, respectively, in tensile residual stress for Case 1 and Case 2. When thermal loads are predominant, residual stress tends to be tensile, with measurements reaching as high as 89 MPa.Yayın Predictive modelling of surface roughness and residual stress induced by milling of hot forged and heat treated AA7075(Springer Nature, 2025-11-03) Tok, Görkem; Dinçer, Ammar Tarık; Kuzu, Ali Taner; Bakkal, MustafaThis study investigates the influence of cutting parameters on residual stress and surface roughness during the milling of hot-forged and T6 heat-treated AA7075 components. Using Taguchi L9 and full-factorial experimental designs and regression modelling, the research highlights important relationships between cutting parameters (cutting speed, feed rate, and depth of cut), residual stress and surface roughness. Higher cutting speeds (350 m/min) and lower feed rates (0.1 mm/tooth) significantly minimized residual stresses, with hoop stress values decreasing from 108.7 MPa at lower speeds (150 m/min) to approximately 73.4 MPa at higher speeds, and axial stress values ranging from 45.9 MPa to 88.5 MPa. Surface roughness (Ra) was most influenced by feed rate, with measurement values varying between 0.25 mu m and 0.92 mu m. Support Vector Regression (SVR) demonstrated better accuracy for predicting residual stress (MAPE: 11.5%) and surface roughness (MAPE: 7%), outperforming Lasso and Ridge regression models. These findings provide a consistent framework for optimizing cutting parameters and enhancing residual stress and surface roughness in AA7075 machining processes, offering practical implications for improving component performance and manufacturing efficiency.Yayın Investigation and prediction of surface integrity induced by milling of hot forged and heat treated AA7075(Motto, 2024-11-03) Tok, Görkem; Dinçer, Ammar Tarık; Kuzu, Ali Taner; Bakkal, Mustafa; Saklakoğlu, İ. EtemThis study examines the influence of cutting parameters on surface integrity, focusing on residual stress and surface roughness, in hot-forged and T6 heat-treated AA7075 components post-milling. Using the Taguchi L9 DOE method, orthogonal cutting milling experiments were performed, with residual stress measured via nondestructive X-ray diffraction (XRD). The analysis indicated that lower cutting speeds reduce residual stress, with down milling causing compressive and up milling causing tensile stresses. A proposed model showed a significant correlation between cutting force and residual stress—higher cutting forces increased residual stress. Surface roughness assessment revealed that feed rate greatly impacts residual stress, with lower feed rates reducing roughness. These insights will aid in developing a regression model for predicting outcomes in future experiments, enhancing the understanding and control of surface integrity in milling AA7075 components.Yayın Energy-based characterization of drilling-induced residual stresses in AA7075-T6(Multidisciplinary Digital Publishing Institute (MDPI), 2026-01) Tok, Görkem; Dinçer, Ammar Tarık; Bakkal, Mustafa; Kuzu, Ali TanerThis study examines the influence of drilling parameters on thrust force, torque, active work, and axial residual stress formation in hot-forged and T6-treated AA7075, a critical high-strength aluminum alloy. A full factorial design was applied using three spindle speeds (800, 1000, 1200 rpm) and three feed rates (0.05, 0.10, 0.15 mm/rev). Cutting force and torque signals were measured using a dynamometer, and axial residual stresses were determined by X-ray diffraction at two locations along the hole depth, namely, the hole entrance (Point A) and the hole exit (Point B). The results show that feed rate is the dominant factor influencing drilling mechanics and residual stress formation, whereas spindle speed mainly affects the thermal and frictional conditions governing stress relaxation. A consistent asymmetry was observed between the two measurement locations, with the exit side exhibiting stronger stress relaxation behavior associated with breakthrough mechanics. Finally, the relationship between active work and axial residual stress is discussed using a qualitative, energy-based interpretation, highlighting active work as a physically meaningful indicator for drilling-induced residual stress evolution.
