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In this paper, we study the stability of a high speed milling process of nickel superalloys Inconel 713C by methods used in nonlinear dynamics. Stability Lobe Diagram was a result of modal analysis and next verified by recurrence plots, recurrence quantification analysis and classical nonlinear methods. A stability lobes diagram shows the indistinct boundary between chatter-free stable machining and unstable processes. Nevertheless, some recurrence quantification analysis measures give interesting results.

This paper presents vibration analysis of an autoparametric pendulum-like mechanism subjected to harmonic excitation. To improve dynamics and control motions, a new suspension composed of a semiactive magnetorheological damper and a nonlinear spring is applied. The influence of essential parameters such as the nonlinear damping or stiffness on vibration, near the main parametric resonance region, are carried out numerically and next verified experimentally in a special experimental rig. Results show that the magnetorheological damper, together with the nonlinear spring can be efficiently used to change the dynamic behaviour of the system. Furthermore, the nonlinear elements applied in the suspension of the autoparametric system allow to reduce the unstable areas and chaotic or rotating motion of the pendulum.

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The modern massive production cannot most often exist without the machining technology. The problems of dynamical instabilities of cutting process and associated harmful chatter vibrations were known for many years.The recent development of cutting and milling concepts and techniques gave way to improve the process stability in fairly high speed cutting [1]. Consequently, identification of the chatter oscillations, and their elimination or even stabilization on some low level have become a high interest in science and technology [2][3][4][5][6][7]. Altintas [2] presented vibration and experimental modal analysis of the machine-tool system in a cutting process. A special focus was placed on chatter vibration generation by the regenerative effect. Additionally, the selection of drive actuators, feedback sensors, the design of real time trajectory generation and interpolation algorithms were discussed. Warminski et al [3] considered a model of the metal cutting process in the context of an approximate analysis of the resulting non-linear differential equations of motion. The technological parameters for the avoidance of primary chatter were presented. Insperger and Mann [4] analyzed the stability conditions for upand down-milling operations using the semi-discretization method. The authors restricted their study to a single degree-of-freedom milling model with a linear cutting force and a single cutting tooth. The method of temporal finite elements was applied in the paper [5]. The periodic chatter- AbstractWe study the milling process of Inconel. By continuously increasing the cutting depth we follow the system response and appearance of oscillations of larger amplitude. The cutting force amplitude and frequency analysis has been done by means of wavelets and Hilbert-Huang transform. We report that in our system the force oscillations are closely related to the rotational motion of the tool and advocate for a regenerative mechanism of chatter vibrations. To identify vibrations amplitudes occurrence in time scale we apply wavelet and Hilbert-Huang transforms.

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