DYNAMICS OF COMPOSITE MATERIALS CUTTING

S u m m a r y The paper presents stability analysis of milling process of epoxide polymer composite material with carbon fibres. In order to determine zones of stable milling , times series of cutting forces are applied. Next, recurrence quantification analysis is conducted which can define three stability indexes: recurrence rate, ratio of recurrence rate to determinism, and recurrence time. Finally, stability lobs diagram for the composite material is proposed. Keywords: milling stability, recurrence quantification analysis Dynamika skrawania materiałów kompozytowych S t r e s z c z e n i e W pracy zaprezentowano wyniki badania stabilności procesu frezowania kompozytu epoksydowo--polimerowego wzmacnianego włóknem węglowym. Określono obszary skrawania stabilnego. Prowadzono analizę przebiegów czasowych sił skrawania opartą na kwantyfikatorach wykresów rekurencyjnych. Stosowano trzy z nich: recurrence rate, proporcję recurrence rate i determinizmu oraz czas rekurencji. Opracowano wykres stabilności frezowania materiału kompozytowego. Słowa kluczowe: stabilność frezowania, wykresy rekurencyjn

Ball Bearing Fault Diagnosis Using Recurrence Analysis

This paper presents the problem of rolling bearing fault diagnosis based on vibration velocity signal. For this purpose, recurrence plots and quantification methods are used for nonlinear signals. First, faults in the form of a small scratch are intentionally introduced by the electron-discharge machining method in the outer and inner rings of a bearing and a rolling ball. Then, the rolling bearings are tested on the special laboratory system, and acceleration signals are measured. Detailed time-dependent recurrence methodology shows some interesting results, and several of the recurrence indicators such as determinism, entropy, laminarity, trapping time and averaged diagonal line can be utilized for fault detection

Modification of Electromechanical Coupling in Electromagnetic Harvester

This paper focuses on the modelling and analysis of electromechanical coupling in a magnetic levitation energy harvester. A prototype harvester is built and its performance is tested with a shaker under resonance conditions. In order to modify the electromechanical coupling, a specially designed coil stack consisting of four independent coils is proposed. The configuration of the coil and the gap between them change the shape of the electromechanical coupling function. The results obtained show that the proper configuration of the modular coil allows one to modify the shape of the electromechanical coupling, increasing the recovered energy, and widens the resonance operating bandwidth

Theoretical and Experimental Investigations of a Pseudo-Magnetic Levitation System for Energy Harvesting

The paper presents an analytical, numerical and experimental analysis of the special designed system for energy harvesting. The harvester system consists of two identical magnets rigidly mounted to the tube’s end. Between them, a third magnet is free to magnetically levitate (pseudo-levitate) due to the proper magnet polarity. The behaviour of the harvester is significantly complicated by a electromechanical coupling. It causes resonance curves to have a distorted shape and a new solution from which the recovered energy is higher is observed. The Harmonic Balance Method (HBM) is used to approximately describe the response and stability of the mechanical and electrical systems. The analytical results are verified by a numerical path following (continuation) method and experiment test with use of a shaker. The influence of harvester parameters on the system response and energy recovery near a main resonance is studied in detail

Effect of variable friction on electromagnetic harvester dynamics

The paper presents a numerical and experimental analysis of an electromagnetic energy harvester. The concept is based on the oscillation of a permanent cylindrical magnet in a coil wrapped on the tube. A new model of variable friction due to magnetic interactions is proposed and analysed. A comparison between different friction coefficients is made for selected cases. Results demonstrate that friction causes decrease in recovered power, as well as affects stability response

Modeling and energy recovery from a system with two pseudo-levitating magnets

In this paper, a model of an electromagnetic system with two levitating magnets is presented. Modeling was performed using the results of experiments. The data obtained make it possible to fit the magnetic forces between two magnets using a 5th order polynomial. The time series show that dry friction constitutes an important part of damping forces. The differential equations of motion consider strong nonlinearities of magnetic and damping forces. These terms cause the nonlinear hardening effect. The energy recovered by magnetic induction is dissipated in the resistors. Numerical simulations show that resistance has an impact on magnet dynamics and energy recovery. From the resonance characteristics obtained, optimal resistance is determined when energy recovery is the highest

Ball Bearing Fault Diagnosis Using Recurrence Analysis

This paper presents the problem of rolling bearing fault diagnosis based on vibration velocity signal. For this purpose, recurrence plots and quantification methods are used for nonlinear signals. First, faults in the form of a small scratch are intentionally introduced by the electron-discharge machining method in the outer and inner rings of a bearing and a rolling ball. Then, the rolling bearings are tested on the special laboratory system, and acceleration signals are measured. Detailed time-dependent recurrence methodology shows some interesting results, and several of the recurrence indicators such as determinism, entropy, laminarity, trapping time and averaged diagonal line can be utilized for fault detection

Cutting force response in milling of Inconel: analysis by wavelet and Hilbert-Huang Transforms

We 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