Materiały konferencyjne, referaty (WM)

Stały URI dla kolekcji


Ostatnie zgłoszenia

Teraz wyświetlane 1 - 20 z 36
  • Pozycja
    Ogólnopolska Konferencja Naukowa Inżynieria Materiałowa - Materiały i Technologie
    (Wydawnictwo Politechniki Łódzkiej, 2022) Sawicki, Jacek - Redaktor naukowy
  • Pozycja
    Numerical analysis of the dynamic thread stretching process
    (Wydawnictwo Politechniki Łódzkiej, 2022) Prążyńska, Aleksandra; Mikołajczyk, Zbigniew; Kuchar, Maciej
    The subject of the paper is the analysis of the dynamic thread stretching process under extreme conditions of the excitation speed with the physical phenomena described in terms of rheological models. The analysis was carried out using three basic models relating to viscoelastic bodies, i.e. the Maxwell, Kelvin-Voigt and Standard 2 models. The relationships between the reaction forces of the stretched threads and the input parameters of the process were included both in an analytical form and in a numerical model. The theoretical analysis was related to the experimental tests carried out on polyester threads with a linear mass of 84, 110 and 334 dtex, assuming the tensile speed ranging from 0.6 to 1.5 m / s. The experiment was carried out on a custom designed test stand. In the conclusion of the obtained research, it can be stated that the most appropriate model for the description of the analysed thread stretching process is the Standard model 2 and it should be emphasized that the traditional analysis based on analytical relationships coincides with the results of numerical analysis. This proves the correctness of the adopted numerical model with specific boundary conditions.
  • Pozycja
    1D, 2D and 3D dosimetry – a brief overview of the DosLab group’s research work
    (Wydawnictwo Politechniki Łódzkiej, 2022) Sąsiadek-Andrzejczak, Elżbieta; Jaszczak, Malwina; Maras, Piotr; Dudek, Mariusz; Piotrowski, Michał; Kozicki, Marek
    DosLab is a research group from the Lodz University of Technology, Poland. The research topics carried out by the DosLab group are innovative and interdisciplinary, covering the area of textile engineering, materials engineering, radiation chemistry and medical physics. This study is intended to present an overview of the group's work related to 1D, 2D and 3D dosimetry of UV and ionizing radiation.
  • Pozycja
    Investigation of wettability measurements of protective gloves materials
    (Wydawnictwo Politechniki Łódzkiej, 2022) Irzmańska, Emilia; Adamus-Włodarczyk, Agnieszka; Jastrzębska, Aleksandra; Litwicka, Natalia
    Wettability measurements of the polymeric materials that are designed to be used for protective gloves are the key aspect in the evaluation of their potential safety of use. The gloves made of polymeric materials that will be resistant to chemical or biological contamination should exhibit low wettability and good adhesive properties to reduce the possibility of accumulation of hazardous substances on the surfaces of the gloves together with losing dexterity of hand movement during work. Currently, in laboratory practice, there is no method to investigate thoroughly the wetting properties of polymeric surfaces taking into consideration parameters like water permeability index, non-wettability index, and absorption index. The presented research concerns the novel way of measuring the wettability of polymeric protective gloves, and the validation of the proposed method. Based on the series of performed measurements, a thorough assessment of the uncertainty budgets for individual components of performed metrological analysis of obtained results was performed. Based on these findings, the measurement errors that could affect the reliability, repeatability, and quality of the performed investigation have been identified.
  • Pozycja
    Dynamics of Energy Harvesting Mechanical System in the Vicinity of 1:1 Resonance
    (Wydawnictwo Politechniki Łódzkiej, 2021) Puzyrov, Volodymyr; Awrejcewicz, Jan; Losyeva, Nataliya
    Energy harvesting provides a useful way to power electronic devices without using batteries or electrical wiring. Energy harvesting can be defined as the conversion of environmental energy, such as mechanical, thermal, light energies into usable electrical energy. Conventional mechanical energy harvesting devices use a line harvester to generate electricity through vibrations or other mechanical motion. However, linear generators generate significant power in a narrow band around resonance, and the power is limited by the internal damping factor and the driving force at the resonant frequency. Such devices implementing a linear (resonant) generator cannot generate sufficient specific power. In present paper the mechanical system is considered which consists of two coupled oscillators (nonlinear absorber connected with primary mass) and a piezoelectric element attached. Two goals are pursued: the mitigation of the responses of the main mass and maximizing the amount of energy extracted from vibrations. The influence of nonlinear stiffness's component is discussed. It is shown that the piezoelectric element allows the effective energy harvesting and at the same has very limited influence on reducing the amplitude of oscillations of the main mass.
  • Pozycja
    Influence of a relatively high frequency structure vibrations on the dynamics of real stick-slip motion
    (Wydawnictwo Politechniki Łódzkiej, 2021) Olejnik, Paweł; Górniak vel Górski, Adrian; Cebulak, Maciej; Awrejcewicz, Jan
    The work concerns the research on the impact of structure vibrations on the dynamics of frictional contact of bodies moving in relation to each other and remaining in frictional contact, causing a stick-slip motion. A literature review was carried out, describing mainly the phenomena concerning friction, but also the dynamics of vibrations and non-ideal energy sources that induce system oscillations. In the next step an experimental station for investigation of friction equipped with a new subsystem inducing high-frequency vibrations is presented to propose a modified physical model of the investigated frictional system. After analysing the most important factors influencing the behavior of the tested system, a mathematical description was prepared, which in theory showed the potential influence of the attached subsystem on the dynamics of the movement of the tested object - the frictional connection. Various methods of implementing the unbalance of rotors, being the source of highfrequency excitation, have been considered. At the final stage, a series of measurements of the displacement of the vibrating block on the moving belt was performed with the highfrequency excitation turned on and off. The prepared graphs were used to analyse the dynamics of frictional contact and the impact of non-autonomous vibrations on the occurrence of the stick-slip phenomenon.
  • Pozycja
    Determination of global damping and stiffness coefficients of journal foil bearing
    (Wydawnictwo Politechniki Łódzkiej, 2021) Łagodziński, Jakub; Tkacz, Eliza; Kozanecki, Zbigniew
    For the few last years, in modern low-power generation systems, a demand for oilfree compressors has appeared. The development of reliable bearing technology for this relatively high-speed small turbomachinery could be crucial. In order to implement this technology more widely, a selection of the optimal design from the viewpoint of machine reliability must be conducted. A high speed turbomachinery with nominal speed of tens of thousands rpm strongly depends on the proper rotordynamic design. This is especially important when the foil bearings are taken to consideration. These compliant surface gas bearings are a class of hydrodynamic bearings that use the ambient gas as their working fluid and, thus, require no dedicated lubrication system. On the other hand, due to their relatively low damping, a designer should analyze thoroughly the dynamics of the rotor-bearing-casing system in the whole operating rpm range. A correctly operating rotor supported in foil bearings is a design solution that have wide possibilities of applications, unavailable for conventionally supported one. In the turbomachinery, a dynamic behaviour of the machine is related mostly to the stiffness and damping coefficients of system components like rotor, bearings and casing. The foil bearings, although simple in design, indicate complex behaviour resulting from Coulomb friction between their elements. This Coulomb friction affects the damping and stiffness of a given bearing support. Gas film, as a bearing part with relatively high stiffness, plays less role in the rotordynamics than the elastic structure of corrugated foils. So far, many more or less reliable numerical models of this phenomenon have been built and their experimental verification results have been described in literature. The research approach presented in this paper is different. The authors suggested obtaining the data experimentally from the bearing isolated on a test bench, where, the shaft is stationary (fixed), and the gas film is not present. The shaker excites the bearing sleeve while the damping and stiffness are provided to the system by the foil structure. The test bench can be described mathematically as system with single degree of freedom with damping and external forcing. The information collected about the bearing’s global coefficients can be implemented afterwards to the rotordynamic software as a tabular data. This will allow to prepare reliable models that will shorten the design process of newly developed compressors with these oilfree supports.
  • Pozycja
    Higher order asymptotic homogenization for dynamical problems
    (Wydawnictwo Politechniki Łódzkiej, 2021) Awrejcewicz, J.; Andrianov, I.I.; Diskovsky, A.A.
    In general, asymptotic homogenization methods are based on the hypothesis of perfect scale separation. In practice, this is not always the case. The problem arises of improving the solution in such a way that it becomes applicable if inhomogeneity parameter is not small. Our study focuses on the higher order asymptotic homogenization for dynamical problems. Systems with continuous and piecewise continuous parameters, discrete systems, and also continuous systems with discrete elements are considered. Both low-frequency and highfrequency vibrations are analyzed. For low-frequency vibrations, several approximations of the asymptotic homogenization method are constructed. The influence of the boundary conditions, the system parameters is investigated.
  • Pozycja
    Anisotropic friction sliding rule influence on the mechanical systems dynamics
    (Wydawnictwo Politechniki Łódzkiej, 2021) Wijata, Adam; Stańczyk, Bartosz; Awrejcewicz, Jan
    Anisotropic friction can produce friction force which is not collinear with a sliding direction. How much friction deviates from a sliding direction is described with a so-called sliding potential or equivalently a sliding rule. A sliding potential is often described with an ellipse or a superellipse. In this paper we propose an oval curve which provides piecewise continuous mathematical description for a sliding rule and fits better to the experimental results than a typical superepllipse. For an exemplary mechanical system it is shown, that an anisotropic sliding potential can lead to an unstable equilibrium position in the system. Furthermore, for what parameters the unstable equilibrium occurs differs between sliding potential models. We have tested four different geometrical models of sliding potential in this regard.
  • Pozycja
    Estimation the Domain of Attraction for a System of Two Coupled Oscillators with Weak Damping
    (Wydawnictwo Politechniki Łódzkiej, 2021) Awrejcewicz, Jan; Puzyrov, Volodymyr; Losyeva, Nataliya; Savchenko, Nina; Nikolaieva, Oksana
    When solving a wide class of problems of nonlinear dynamics, the stability property of a given system regime is a prerequisite for design. An important role is played by the concept of the domain of attraction (DoA) of the equilibrium point (or limit cycle). However, as a rule, this domain is difficult to find and describe in explicit form. Therefore, the search for DoA estimate has been a fundamental problem in the control theory since the middle of the last century. Currently, methods based on Lyapunov functions predominate in the literature. We have studied the problem of obtaining the estimates of the DoA for equilibrium of the mechanical systems. The method for using Lyapunov function of special kind for a system with polynomial right-hand side to find the estimates for DoA is proposed. This procedure is illustrated by the example of a mechanical system which consists of two coupled nonlinear oscillators with weak damping.
  • Pozycja
    Dynamic analysis of functionally graded sandwich shells resting on elastic foundations
    (Wydawnictwo Politechniki Łódzkiej, 2021) Tetyana, Shmatko; Lidiya, Kurpa; Awrejcewicz, Jan
    Free vibrations of sandwich shallow shells resting on elastic foundations are investigated. It is assumed that shell consists of three layers of the different thickness. Different schemes of arrangement of layers are considered. Namely, the core is made of ceramics or metals , and the upper and lower layers are made of FGM. The volume fractions of metal and ceramic are described by the power law. Shear deformation shell theory of the first (FSDT) that includes interaction with elastic foundations is applied. To study shells with an arbitrary plan form the R-functions theory combined with the variational Ritz method are used. Validation of the proposed method and developed software has been examined on test problems for FG shell with rectangular plan form. New results for shallow shells with complex plan form were obtained. Effects of the power law index, boundary conditions, thickness of core and face sheet layers, elastic foundations on fundamental frequencies are studied in this work.
  • Pozycja
    Bionic hand control using EMG signals
    (Wydawnictwo Politechniki Łódzkiej, 2021) Sencerek, Jędrzej; Zagrodny, Bartłomiej
    Abstract. 3D printed prototype a human hand which is controled by sEMG signal was created to simulate two types of fingers motions. The first one includes fingers flexion/extension and the second one is focused on opposing the thumb. These two types of motions are executed by one pair of biological muscles, by the meaning of sEMG signals. The recruting electrodes are attached to both biceps brachii. One of them is responsible for fingers flexion/thumb abduction, and the other is for fingers extension/thumb adduction. The simultaneous contraction of both muscles couses a change in the mode of movement ( fingers - thumb). Control is based on the Arduino microcontroller extended by two EMG Olimex shields and two servos. The main idea behind this project was to create an easy and cheap alternative to commercial prosthetic solutions.
  • Pozycja
    Construction and 3D model of stand for investigating a non-ideal forcing in a nonlinear chain dynamics of self-excited oscillators with friction
    (Wydawnictwo Politechniki Łódzkiej, 2021) Rogala, Patryk; Olejnik, Paweł; Awrejcewicz, Jan
    The research involves application and research on a non-ideal forcing to modelling and identification of vibrating systems with friction. It is still an innovative approach in the numerical analysis of vibrations of mechatronic machines and devices. This will allow to make a much real numerical modelling and more efficient identification of nonlinear dynamic phenomena observed in vibrating systems with friction, and thus, a better modelling of such phenomena in computer programs. To obtain the goal, initial 3D model of the mechanical stand was made in the CAD software. Based on the 3D model, real stand will be built, and experiments will be held to obtain data that will be necessary to ensure correctness of the mathematical model, which also will be studied and developed.
  • Pozycja
    Mathematical Modelling of an extended Swinging Atwood Machine
    (Wydawnictwo Politechniki Łódzkiej, 2021) Yakubu, Godiya; Olejnik, Paweł; Awrejcewicz, Jan
    An extended model for a variable-length pendulum’s mechanical application is being derived from the Swinging Atwood Machine (SAM). An electrical component consisting of an electromagnet and armature coil is attached on the link connected to the counterweight mass on the left-hand side of the modified SAM to provide an excitation force for the system when an electric current is induced. The extended SAM presents a novel SAM concept being derived from a variable-length double pendulum with a suspension between the two pendulums. The equations of motion are simulated to see the trajectory of the two pendulums. The results of original numerical simulations show some compact regions of attraction at some regimes. Therefore, the extended SAM’s nonlinear dynamics presented in the current work can be thoroughly studied, and more modifications can be achieved. The new technique can reduce residual vibrations through damping when the desired level of the crane is reached. It can also be used in simple mechatronic and robotic systems.
  • Pozycja
    Geometrically nonlinear vibrations of double-layered nanoplates
    (Wydawnictwo Politechniki Łódzkiej, 2021) Awrejcewicz, Jan; Mazur, Olga
    The geometrically nonlinear vibrations of simply supported double-layered graphene sheet systems are considered in the presented manuscript. The interaction between layers is taken into account due to van der Waals forces. The investigation is based on the nonlocal elasticity theory, Kirchhoff plate theory and von Kármán theory. The governing equations are used in mixed form by introducing the stress Airy function. The analytical presentation of the nonlinear frequency ratio for in-phase vibration and anti-phase vibration modes is presented. It is shown that the nonlocal parameter included in the compatibility equation can significantly change the vibrating characteristics.
  • Pozycja
    Thermal waves in composite membrane with circular inclusions in hexagonal lattice structures
    (Wydawnictwo Politechniki Łódzkiej, 2021) Andrianov, I.V.; Awrejcewicz, J.; Starushenko, G.A.; Kvitka, S.A.
    Non-stationary heat conduction in the fibre composite materials is studied. 2D сomposite media consists of matrix with circular inclusions in hexagonal lattice structures. The perfect contact between different materials is assumed on the boundary of the fibres. The local temperature field in the unit cell is modeled by the heat equation. Time variable excludes from the original boundary value problem using of Laplace transform. Asymptotic homogenization method allows to reduce original problem for multiply-connected domain to the sequence of boundary value problems in simply-connected domains. Composite material is supposed densely-packed with a high-contrast. In this case, the local boundary value problem includes a small parameter equal to the ratio of the distance between the inclusions to the characteristic cell size. Using of additional small parameter and thin layer asymptotics allows to solve local problem analytically. Closed form expression for effective heat conductivity is obtained.
  • Pozycja
    Design and simulation of a lower limb exoskeleton with linear electric actuators
    (Wydawnictwo Politechniki Łódzkiej, 2021) Grzelczyk, Dariusz; Jarzyna, Olga; Awrejcewicz, Jan
    In the present study, we proposed and investigated a relatively simple and inexpensive construction of a lower limb exoskeleton driven by linear electric actuators and controlled by an Arduino microcontroller board. Moreover, to study crucial kinematic and dynamic parameters of the proposed device, we developed a general, three-dimensional simulation model of the exoskeleton in Mathematica software. To control individual joints of the investigated exoskeleton, we employed time histories of human joint angles in normal gait, recorded with the use of a motion capture system. As a result, we developed a novel human gait generator, which can be used to produce rhythmic movements in hip, knee and ankle joints of both limbs. Finally, the developed control approach was verified with the use of the constructed prototype of the exoskeleton.
  • Pozycja
    Conditions Regulating Tumor Cell Behaviour in Biological Systems with Memory of States
    (Wydawnictwo Politechniki Łódzkiej, 2021) Dzyubak, Larysa; Dzyubak, Oleksandr; Awrejcewicz, Jan
    For biological systems with memory of states there were found conditions which regulate tumor cell behaviour. These conditions depend on parameters of the multi-parametric space. Based on the Masing–Bouc-Wen’s framework, the state memory in the biological system was simulated by means of supplemental state variables (internal variables). The additional state variables were introduced into the generalized non-linear multi-scale diffusion cancer invasion model and the chaotic cancer attractors were found. To quantify chaotic cancer attractors, the technique based on the wandering trajectories analysis was applied.
  • Pozycja
    Drive-by-wire of a converted into electric car Syrena 105 enabling Hardware-In-Loop tests of driving
    (Wydawnictwo Politechniki Łódzkiej, 2021) Adamski, Paweł; Olejnik, Paweł
    In this work, replacing an electronic throttle pedal and a driver in an electric car converted into electric by a hardware-in-loop workbench is described, highlighting the advantage of drive-by-wire feature that appeared after conversion. Drive-by-wire facilitates replacing a driver by Hardware-In-Loop (HIL) workbench, as instead of simulating a mechanical pedal depression by a servomechanism, electric signals can be transmitted directly from the workbench. Thanks to one-pedal-driving feature of the motor controller used in the car, there is a possibility of performing a variety of road tests replacing only the electronic throttle pedal. Hardware interventions in the car are described and sample HIL test results are presented.
  • Pozycja
    Magnetic oscillator under excitation with controlled initial phase
    (Wydawnictwo Politechniki Łódzkiej, 2021) Polczyński, Krystian; Bednarek, Maksymilian; Awrejcewicz, Jan
    The work contains the results of numerical simulations of the dynamics of a magnetic pendulum system subjected to excitation with a varying initial phase. A magnetic pendulum consists of a magnet fixed to the end of its arm and an electric coil below it. The initial phase of the excitation is presented as a linear function of the dynamic variable of the system, which is the angular position of the pendulum. The obtained basins of attraction indicate the occurrence of multi-periodic solutions in the system depending on the changes in the parameters of this system. The periodicities of the observed solutions are quantified mostly by odd numbers.