Wavelet-Based Scalogram Analysis of Surface Texture and Technological Heredity in Turning and Burnishing

Machined surfaces can retain features from preceding operations, complicating the identification of their processing history. This study develops a wavelet-based method to identify routes and quantify technological heredity (process-history effects) from surface profiles. Profiles from 40-mm-diameter shafts made of 12Kh18N10T stainless steel (broadly comparable to AISI 321) were analyzed using the continuous wavelet transform with a complex Morlet wavelet. Scalograms were partitioned into nine Taguchi L9 regions and described by five features: peak intensity, relative peak intensity, relative spatial and period coordinates of the peak, and relative high-energy area S75. Robustness was evaluated using the Taguchi signal-to-noise metric at artificial noise levels up to 50%. Discrimination was assessed using principal component analysis (PCA), Fisher scores, and nearest-centroid and k-nearest-neighbor classification. Two-way analysis of variance (ANOVA) quantified technological heredity; the unexplained variance ratio (SSIJ+SSerr)/SStot represented the variability not explained by the main effects of period and spatial position. Classification performance depended on the route group: for Group 2, profile-level 1-nearest-neighbor validation gave 7/18 correct classifications from the scalogram descriptors and 18/18 from Ra, Rq, and Rz. Routes involving burnishing exhibited lower unexplained variance and more compact PCA clusters, whereas routes combining rough and finish turning showed stronger heredity signatures and more complex scalogram structures. The framework therefore provides complementary scale-resolved information and a descriptive assessment of process-history-related variability; general route identification requires further validation. The proposed scalogram descriptors are intended to complement, rather than replace, conventional roughness parameters such as Ra, Rz, and Rq, by providing additional information on the scale- and position-resolved structure of the machined surface.