OBRABOTKAMETALLOV technology Vol. 27 No. 1 2025 Both static and dynamic SPD methods can be significantly improved by applying ultrasonic vibrations to the working tool [2]. This technological approach allows for a substantial increase in the degree of strain hardening and hardness, as well as a reduction in roughness and the creation of a regular microrelief. The intensification of SPD processes using ultrasound is widely applied. A significant body of work, both fundamental [4, 8, 9] and applied [14, 15, 16], is dedicated to this type of processing. Two primary schemes for ultrasonic SPD are based on the use of deforming elements that are either rigidly connected to the oscillating system or are not rigidly connected to the vibration source [23]. In 1964, I.I. Mukhanov first proposed a method of ultrasonic SPD using a working tool rigidly connected to the oscillating system [21]. Further developing this method, I.A. Stebelkov patented a type of processing using free working bodies in 1975 [22]. A rigidly connected working tool allows for more uniform processing and results in lower surface roughness than processing with a free deforming element [3, 6]. However, processing with a free deforming element can achieve a greater degree of strain hardening and a deeper hardened layer [25]. One of the main areas of research in ultrasonic SPD is the study of the influence of this processing method on the structure and properties of various materials based on iron [5, 7], titanium, aluminum, etc. [11–13]. Recently, this trend has been devolving in the field of nanotechnology [20, 26]. Most technical solutions for ultrasonic SPD are based on transmitting longitudinal vibrations to the working tool. Ultrasonic smoothing, used to achieve the lowest possible roughness, can be implemented according to three processing schemes, as shown in Fig. 1. S x î m 3 F N 2 1 n S x 3 FN 1 î m 2 n 2 3 FN î m n a b с Fig. 1. Surface plastic deformation (SPD) processing schemes: a – with normal vibrations; b, c with tangential vibrations (1 – chuck, 2 – workpiece, 3 – tool) The processing of curved surfaces, including those produced by additive manufacturing technologies, presents the greatest challenges [33–36]. When the oscillating system with the tool moves rectilinearly along a curved surface, their force interaction can vary significantly. The tool axis deviates from the normal to the surface, and the static pressing force F is decomposed into components (Fig. 2). When the tool axis is positioned at an angle of α = 90° and the static pressing force is F, there is only a normal component of this force FN, i.e., F = FN. When α ≠ 90°, in addition to the normal component FN, a tangential component Fτ also appears. In this case, FN = F∙sinα, and Fτ = F∙cosα. The periodic force generated by the tool changes in the same way. The nature of the impact on the surface also changes accordingly. At α = 90° and FN = FNmax, each vibration of the tool leaves a spherical imprint on the surface, with the maximum normal strain occurring at the center of the imprint (Fig. 3, a). At α ≠ 90° and with the presence of the component Fτ, the tool slides along the surface, and the imprints are elongated. Normal strains dominate at the beginning of the imprint, while shear strains dominate at the end (Fig. 3, b). That is, by analogy with static methods of SPD, at α = 90° the process is carried out according to a smoothing scheme, while at α ≠ 90° it is carried out according to a vibrational smoothing scheme.
RkJQdWJsaXNoZXIy MTk0ODM1