1. |
Badora M., Bartosik P.^{♦}, Graziano A.^{♦}, Szolc T.A., Using physics-informed neural networks with small datasets to predict the length of gas turbine nozzle cracks,
Advanced Engineering Informatics, ISSN: 1474-0346, DOI: 10.1016/j.aei.2023.102232, Vol.58, No.102232, pp.1-16, 2023Streszczenie: We created a Physics-Informed Neural Network (PINN) to model the propagation of fatigue cracks. The analyzed object is a high-pressure Nozzle of an industrial gas turbine. The models are based on a Recurrent Neural Network with an embedded Feedforward Neural Network to estimate the stress intensity factor. The thermal stresses are calculated based on engine operational data, leveraging a Finite Element Analysis. However, the time series are available just for 54% of the start-stop cycles, and only 13 crack measures were recorded. Three separate models were trained based on ten, two, and one observation, respectively. The importance of the empirical data was regulated during the training to avoid solutions inconsistent with the underlying physics. The models generalize well and predict accurately also outside the training domain. Additionally, we propose a novel method of scaling models based on PINNs and transferring knowledge between domains. It enables predicting in the target domain, even if damage measures are unavailable. The obtained results confirm the effectiveness of this approach. Słowa kluczowe: Physics-informed neural networks , Predictive maintenance , Fatigue cracks , Regression analysis , Small data , Turbomachinery Afiliacje autorów:
Badora M. | - | IPPT PAN | Bartosik P. | - | inna afiliacja | Graziano A. | - | inna afiliacja | Szolc T.A. | - | IPPT PAN |
| | 140p. |
2. |
Hańczur P., Szolc T.A., Konowrocki R.,
Suppression of rotating machine shaft-line torsional vibrations by a driving asynchronous motor using two advanced control methods,
BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: DOI: 10.24425/bpasts.2023.147925, Vol.71, No.6 ( e147925 ), pp.1-13, 2023Streszczenie: Many industrial rotating machines driven by asynchronous motors are often affected by detrimental torsional
vibrations. In this paper a method of attenuation of torsional vibrations in such objects is proposed. Here, an asynchronous motor
under a proper control can simultaneously operate as a source of drive and actuator. Namely, by means of the proper control of
motor operation it is possible to suppress torsional vibrations in the object under study. Using this approach, transient and steady-
state torsional vibrations of the rotating machine drive system can be effectively attenuated as well as its precise operational
motions can be assured. The theoretical investigations are carried out by means of a structural mechanical model of the drive
system and an advanced circuit model of the asynchronous motor controlled using two methods: the direct torque control – space
vector modulation (DTC-SVM) and the rotational velocity controlled torque (RVCT) based on the momentary rotational velocity
of the driven machine working tool. From the obtained results it follows that by means of the RVCT technique steady-state
torsional vibrations induced harmonically and transient torsional vibrations excited by switching various types of control on and
off can be suppressed as effectively as using the advanced vector method DTC-SVM. Słowa kluczowe: rotating machine,drive system,control methods,asynchronous motor,torsional vibrations Afiliacje autorów:
Hańczur P. | - | IPPT PAN | Szolc T.A. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN |
| | 100p. |
3. |
Falkowski K.^{♦}, Kurnyta-Mazurek P.^{♦}, Szolc T., Henzel M.^{♦}, Radial magnetic bearings for rotor–shaft support in an electric jet engine,
Energies, ISSN: 1996-1073, DOI: 10.3390/en15093339, Vol.15, No.3339, pp.1-30, 2022Streszczenie: New technologies are being developed to elaborate cutting-edge electrical jet engines to replace classical constructions. These new concepts consider the possibility of using electrical machines both as starters and generators, as well as suspension systems for the turbine shafts of aircraft engines. The paper will present mathematical analysis regarding active magnetic bearing (AMB) implementation for rotor–shaft support. This technology allows the elimination of friction forces between cooperating kinematic pairs (stator and rotor), reduces the adverse effects of classic bearings, and increases operating speed range and an operational susceptibility. The mathematical and numerical analysis of active magnetic suspension systems are presented. Next, a comparison of the theoretical studies using Comsol Multiphysics software and its experimental verification are described. A discussion regarding the mathematical analysis and experimental effects is also provided. The conclusion summarizes the theoretical and experimental features of heteropolar radial active magnetic bearings in new electric aircraft engines. Słowa kluczowe: active magnetic bearings,electric jet engine,current stiffness coefficient,displacement stiffness coefficient Afiliacje autorów:
Falkowski K. | - | Military University of Technology (PL) | Kurnyta-Mazurek P. | - | Military University of Technology (PL) | Szolc T. | - | IPPT PAN | Henzel M. | - | Military University of Technology (PL) |
| | 140p. |
4. |
Szczęsny G.^{♦}, Kopeć M., Politis D.J.^{♦}, Kowalewski Z.L., Łazarski A.^{♦}, Szolc T., A review on biomaterials for orthopaedic surgery and traumatology: from past to present,
Materials, ISSN: 1996-1944, DOI: 10.3390/ma15103622, Vol.15, No.10, pp.3622-1-20, 2022Streszczenie: The principal features essential for the success of an orthopaedic implant are its shape, dimensional accuracy, and adequate mechanical properties. Unlike other manufactured products, chemical stability and toxicity are of increased importance due to the need for biocompatibility over an implants life which could span several years. Thus, the combination of mechanical and biological properties determines the clinical usefulness of biomaterials in orthopaedic and musculoskeletal trauma surgery. Materials commonly used for these applications include stainless steel, cobalt-chromium and titanium alloys, ceramics, polyethylene, and poly(methyl methacrylate) (PMMA) bone cement. This study reviews the properties of commonly used materials and the advantages and disadvantages of each, with special emphasis on the sensitivity, toxicity, irritancy, and possible mutagenic and teratogenic capabilities. In addition, the production and final finishing processes of implants are discussed. Finally, potential directions for future implant development are discussed, with an emphasis on developing advanced personalised implants, according to a patient’s stature and physical requirements. Słowa kluczowe: orthopaedic surgical procedures, biomaterials, implants, biocompatible materials, alloys, ceramic, polyethylene Afiliacje autorów:
Szczęsny G. | - | Medical University of Warsaw (PL) | Kopeć M. | - | IPPT PAN | Politis D.J. | - | Imperial College London (GB) | Kowalewski Z.L. | - | IPPT PAN | Łazarski A. | - | Medical University of Warsaw (PL) | Szolc T. | - | IPPT PAN |
| | 140p. |
5. |
Szczęsny G.^{♦}, Kopeć M., Szolc T., Kowalewski Z.L., Małdyk P.^{♦}, Deformation of the Titanium Plate Stabilizing the Lateral Ankle Fracture Due to Its Overloading in Case of the Young, Obese Patient: Case Report Including the Biomechanical Analysis,
Diagnostics, ISSN: 2075-4418, DOI: 10.3390/diagnostics12061479, Vol.12, No.6, pp.1479-1-10, 2022Streszczenie: The number of overweight and obese patients in developed countries is gradually increasing. It was reported that 1287 (64%) out of 2007 adults operated on in 2017 had a body mass index (BMI) greater than 25 kg/m2, and 26.4% even greater than 30, while the BMI of the most obese patient was as high as 57.6 kg/m2. Such distressing statistics raised an issue related to the inadequate durability of implants used for the fixation of bone fractures. Implants for the lower-extremity fractures may not be durable enough to fit the requirements of overweight and obese patients. This case report presents the history of a 23-year-old obese male with a BMI of 38.7, who bent the angularly stabile titanium plate stabilizing his broken lateral ankle and torn distal tibiofibular syndesmosis. Biomechanical analysis showed that the maximal static bending moment registered during one-leg standing was equal to 1.55 Nm. This value was circa one-third of the maximally admissible bending moment for this particular plate (5.34 Nm) that could be transmitted without its plastic deformation. Since dynamic forces exceed static ones several (3–12) times during typical activities, such as walking, climbing the stairs, running, and jumping, unpredictable forces may occur and increase the risk of loosening, bending, and even breaking implants. None of these situations should have occurred for the typical patient’s body mass of 75 kg, or even for the analyzed mass of the young patient (120 kg) who tried to avoid excessive loading during his daily routine. Subsequent implant bending and destabilization of the fracture shows that for the significantly high and still growing number of obese patients, a very strict physical regime should be recommended to prevent overabundant dynamic loads. On the other hand, the geometry of implants dedicated to these patients should be reconsidered. Słowa kluczowe: ankle injuries surgery, bone plate, obesity, postoperative complications, implant failure Afiliacje autorów:
Szczęsny G. | - | Medical University of Warsaw (PL) | Kopeć M. | - | IPPT PAN | Szolc T. | - | IPPT PAN | Kowalewski Z.L. | - | IPPT PAN | Małdyk P. | - | Medical University of Warsaw (PL) |
| | 70p. |
6. |
Badora M., Sepe M.^{♦}, Bielecki M.^{♦}, Graziano A.^{♦}, Szolc T., Predicting length of fatigue cracks by means of machine learningalgorithms in the small-data regime,
EKSPLOATACJA I NIEZAWODNOŚĆ - MAINTENANCE AND RELIABILITY, ISSN: 1507-2711, DOI: 10.17531/ein.2021.3.19, Vol.23, No.3, pp.575-585, 2021Streszczenie: In this paper several statistical learning algorithms are used to predict the maximal length of fatigue cracks based on a sample composed of 31 observations. The small-data regime is still a problem for many professionals, especially in the areas where failures occur rarely. The analyzed object is a high-pressure Nozzle of a heavy-duty gas turbine. Operating parameters of the engines are used for the regression analysis. The following algorithms are used in this work: multiple linear and polynomial regression, random forest, kernel-based methods, AdaBoost and extreme gradient boosting and artificial neural networks. A substantial part of the paper provides advice on the effective selection of features. The paper explains how to process the dataset in order to reduce uncertainty; thus, simplifying the analysis of the results. The proposed loss and cost functions are custom and promote solutions accurately predicting the longest cracks. The obtained results confirm that some of the algorithms can accurately predict maximal lengths of the fatigue cracks, even if the sample is small. Słowa kluczowe: empirical models, fatigue cracks, predictive maintenance, regression analysis, small data, statistical learning, turbomachinery Afiliacje autorów:
Badora M. | - | IPPT PAN | Sepe M. | - | inna afiliacja | Bielecki M. | - | inna afiliacja | Graziano A. | - | inna afiliacja | Szolc T. | - | IPPT PAN |
| | 140p. |
7. |
Konowrocki R., Kalinowski D., Szolc T., Marczewski A.^{♦}, Identification of safety hazards and operating conditions of the low-floor tram with independently rotating wheels with various drive control configurations,
EKSPLOATACJA I NIEZAWODNOŚĆ - MAINTENANCE AND RELIABILITY, ISSN: 1507-2711, DOI: 10.17531/ein.2021.1.3, Vol.23, No.1, pp.21-33, 2021Streszczenie: The aim of the article is to develop a method for the analysis of tram dynamics related to safety during operation. To achieve this, a mathematical model of the vehicle represented by a multibody simulation MBS system is used. Models of tram with a classic and innovative drive, based on a system of independently rotating wheels on crank axles are analyzed. A new configuration of an innovative drive control of the considered vehicle with the use of braking of independent wheels is proposed. A new geometry of test track is presented. During numerical investigation the values of 'Y' leading forces of tram wheels with the considered innovative drive proved to be lower than in the corresponding vehicle with standard wheelsets. It has been demonstrated that the active control systems are of key importance and should be applied in such innovative tram drives. Słowa kluczowe: maintenance of safety, reliability of trams, derailment of tramcar, numerical tests, drive with independently rotating wheel Afiliacje autorów:
Konowrocki R. | - | IPPT PAN | Kalinowski D. | - | IPPT PAN | Szolc T. | - | IPPT PAN | Marczewski A. | - | inna afiliacja |
| | 140p. |
8. |
Ecker H.^{♦}, Nordmann R.^{♦}, Burczyński T., Szolc T., Dynamics of rotating machinery,
BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2021.139792, Vol.69, No.6, pp.e139792-1-5, 2021, EDITORIAL | |
9. |
Kurnyta-Mazurek P.^{♦}, Szolc T., Henzel M.^{♦}, Falkowski K.^{♦}, Control system with a non-parametric predictive algorithm for a high-speed rotating machine with magnetic bearings,
BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2021.138998, Vol.69, No.6, pp.e138998-1-9, 2021Streszczenie: This paper deals with research on the magnetic bearing control systems for a high-speed rotating machine. Theoretical and experimental characteristics of the control systems with the model algorithmic control (MAC) algorithm and the proportional-derivative (PD) algorithm are presented. The MAC algorithm is the non-parametric predictive control method that uses an impulse response model. A laboratory model of the rotor-bearing unit under study consists of two active radial magnetic bearings and one active axial (thrust) magnetic bearing. The control system of the rotor position in air gaps consists of the fast prototyping control unit with a signal processor, the input and output modules, power amplifiers, contactless eddy current sensors and the host PC with dedicated software. Rotor displacement and control current signals were registered during investigations using a data acquisition (DAQ) system. In addition, measurements were performed for various rotor speeds, control algorithms and disturbance signals generated by the control system. Finally, the obtained time histories were presented, analyzed and discussed in this paper. Słowa kluczowe: magnetic bearing; predictive algorithm; high speed rotating machine Afiliacje autorów:
Kurnyta-Mazurek P. | - | Military University of Technology (PL) | Szolc T. | - | IPPT PAN | Henzel M. | - | Military University of Technology (PL) | Falkowski K. | - | Military University of Technology (PL) |
| | 100p. |
10. |
Szolc T., Konowrocki R., Research on stability and sensitivity of the rotating machines with overhung rotors to lateral vibrations,
BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2021.137987, Vol.69, No.6, pp.1-12, 2021Streszczenie: The rotating machines with overhung rotors form a wide class of devices used in many types of industry. For this kind of rotor machines in the paper there is investigated an influence of dynamic and static unbalance of a?rotor, parallel and angular misalignments of shafts as well as inner anisotropy of rigid couplings on system dynamic responses. The considerations are performed by means of a hybrid structural model of the machine rotor-shaft system, which consists of continuous beam finite elements and discrete oscillators. Numerical calculations are carried out for parameters characterizing a heavy blower applied in the mining industry. The main goal of the research is to assess a?sensitivity of the above-mentioned imperfections on excitation severity of rotor-shaft lateral vibrations and on motion stability of the machine in question. Słowa kluczowe: overhung rotor-shaft, lateral vibrations, stability and sensitivity analysis, system imperfections Afiliacje autorów:
Szolc T. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN |
| | 100p. |
11. |
Szolc T., Falkowski K.^{♦}, Kurnyta-Mazurek P.^{♦}, Design of a combined self-stabilizing electrodynamic passive magnetic bearing support for the automotive turbocharger rotor,
JOURNAL OF VIBRATION AND CONTROL, ISSN: 1077-5463, DOI: 10.1177/1077546320933486, pp.1-12, 2020Streszczenie: The purpose of this study is to create a concept for what would be a structurally simple and perationally robust support for the automotive turbocharger rotor in electrodynamic passive magnetic bearings. Because this kind of magnetic suspension-in its fundamental version-is dynamically unstable, to avoid the disadvantages contained therein, what is being proposed is the addition of external damping through the employment of the newly designed combined self-stabilizing electrodynamic passive magnetic bearing. The electromagnetic stiffness and damping characteristics of combined electrodynamic passive magnetic bearings have been determined for various shaft rotational speeds by means of the advanced 3D finite element method. In this study, a dynamic interaction between the turbocharger rotor shaft and the passive magnetic suspension is proposed as a support for both the fundamental electrodynamic passive magnetic bearings and the suggested combined self-stabilizing passive magnetic bearings. Here, the main attention is focused on the asymptotic stability of both the rotor shaft suspension variants. The additional damping magnitudes required to stabilize the most sensitive lateral eigenmodes of the object under consideration have been determined by means of the Routh-Hurwitz stability criterion. Słowa kluczowe: rotor dynamics, combined electrodynamic passive magnetic bearings, turbocharger flexible rotor shaft, stability analysis, stabilizing damping magnitude Afiliacje autorów:
Szolc T. | - | IPPT PAN | Falkowski K. | - | Military University of Technology (PL) | Kurnyta-Mazurek P. | - | Military University of Technology (PL) |
| | 70p. |
12. |
Szolc T., Falkowski K.^{♦}, Henzel M.^{♦}, Kurnyta-Mazurek P.^{♦}, Determination of parameters for a design of the stable electro-dynamic passive magnetic support of a high-speed flexible rotor,
BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpas.2018.125719, Vol.67, No.1, pp.91-105, 2019Streszczenie: Electro-dynamic passive magnetic bearings are now viewed as a feasible option when looking for support for high-speed rotors. Nevertheless, because of the skew-symmetrical visco-elastic properties of such bearings, they are prone to operational instability. In order to avoid this, the paper proposes the addition of external damping into the newly designed vibrating laboratory rotor-shaft system. This may be achieved by means of using simple passive dampers that would be found among the components of the electro-dynamic bearing housings along with magnetic dampers, which satisfy the operational principles of active magnetic bearings. Theoretical investigations are going to be conducted by means of a structural computer model of the rotor-shaft under construction, which will take into consideration its actual dimensions and material properties. The additional damping magnitudes required to stabilize the most sensitive lateral eigenmodes of the object under consideration have been determined by means of the Routh-Hurwitz stability criterion. Słowa kluczowe: rotor-dynamics, electrodynamic passive magnetic bearings, flexible rotor-shaft, active magnetic damper, stability analysis Afiliacje autorów:
Szolc T. | - | IPPT PAN | Falkowski K. | - | Military University of Technology (PL) | Henzel M. | - | Military University of Technology (PL) | Kurnyta-Mazurek P. | - | Military University of Technology (PL) |
| | 100p. |
13. |
Michajłow M.^{♦}, Jankowski Ł., Szolc T., Konowrocki R., Semi-active reduction of vibrations in the mechanical system driven by an electric motor,
OPTIMAL CONTROL APPLICATIONS & METHODS, ISSN: 0143-2087, DOI: 10.1002/oca.2297, Vol.38, No.6, pp.922-933, 2017Streszczenie: In this paper, a semi-active damping approach is used for reduction of vibrations in a laboratory drivetrain system. The considered drivetrain system is powered by an electric, asynchronous motor at the one side and loaded with a harmonically varying torque on the other side. Here, an influence of electromechanical interaction, i.e., an electromechanical coupling, between the electric motor and the mechanical system has been taken into consideration. The harmonic load signal induces torsional vibrations in the system, which in the steady-state phase of motion become periodic. The aim of the work is to determine the optimal control function for a semi-active damping element, leading to vibration reduction and considering only the steady-state phase of system motion. The optimal control is derived by using a semi-analytical approach based on the optimal control theory aided with supplementary numerical computations. The proposed methodology is fully general, and it can be directly applied to any type of a periodically oscillating system. Słowa kluczowe: electric motor, electromechanical coupling, optimal control, periodic torsional vibrations, semi-active damping Afiliacje autorów:
Michajłow M. | - | inna afiliacja | Jankowski Ł. | - | IPPT PAN | Szolc T. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN |
| | 30p. |
14. |
Konowrocki R., Szolc T., Pochanke A.^{♦}, Pręgowska A., An influence of the stepping motor control and friction models on precise positioning of the complex mechanical system,
MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2015.09.030, Vol.70-71, pp.397-413, 2016Streszczenie: This paper aims to investigate, both experimentally and theoretically, the electromechanical dynamic interaction between a driving stepping motor and a driven laboratory belt-transporter system. A test-rig imitates the operation of a robotic device in the form of a working tool-carrier under translational motion. The object under consideration is equipped with measurement systems, which enable the registration of electrical and mechanical quantities. Analytical considerations are performed by means of a circuit model of the electric motor and a discrete, non-linear model of the mechanical system. Various scenarios of the working tool-carrier motion and positioning by the belt-transporter are measured and simulated; in all cases the electric current control of the driving motor has been applied. The main goal of this study is to investigate the influence of the stepping motor control parameters along with various mechanical friction models on the precise positioning of a laboratory robotic device. Słowa kluczowe: Belt transporter system, Precise positioning, Stepping motor, Current control, Experimental verification Afiliacje autorów:
Konowrocki R. | - | IPPT PAN | Szolc T. | - | IPPT PAN | Pochanke A. | - | Politechnika Warszawska (PL) | Pręgowska A. | - | IPPT PAN |
| | 45p. |
15. |
Michajłow M.^{♦}, Konowrocki R., Szolc T., A semi-active control of lateral vibrations of the overhung rotor using dampers with the magneto-rheological fluid,
VIBRATIONS IN PHYSICAL SYSTEMS, ISSN: 0860-6897, Vol.27, pp.274-280, 2016Streszczenie: In the paper there is proposed an algorithm of an efficient semi-active control of steady-state periodic lateral vibrations of the overhung rotor-shaft system. This algorithm has been developed using fundamentals of the Optimal Control Theory. In the considered system the control is realized by means of the linear dampers withthe magneto-rheological fluid built in the bearing housing. The computational example demonstrates possibilities of the applied approach resulting in an additional reduction of out-of-resonance and near resonance harmonic oscillation amplitudes in comparison withan analogous passive control. Słowa kluczowe: overhung rotor-shaft, lateral vibrations, semi-active control, Optimal Control Theory Afiliacje autorów:
Michajłow M. | - | inna afiliacja | Konowrocki R. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
| | 5p. |
16. |
Konowrocki R., Szolc T., An analysis of the self-excited torsional vibrations of the electromechanical drive system,
VIBRATIONS IN PHYSICAL SYSTEMS, ISSN: 0860-6897, Vol.27, pp.187-194, 2016Streszczenie: This paper presents a dynamic analysis of torsional vibrations of the railway drive system. A dynamic electromechanical drive model has been created and then integrated with the railway wheelset-rail system to simulate self-excited torsional vibrations of the considered system. Results of this analysis are used in order to investigate the drive system’s sensitivity to torsional oscillations. Here, the dynamic electromechanical interaction between the electric driving motor and the rotating wheelset is considered. This investigation has proved that the torsional stiffness and damping of drivetrain system strongly affect amplitudes of the self-excited vibrations. A self-excited vibrations affecting on an energy consumption of the electric motor of the considered system are studied. Słowa kluczowe: torsional vibrations, electromechanical coupling, wheel-rail adhesion, wheelset drivetrain dynamic Afiliacje autorów:
Konowrocki R. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
| | 5p. |
17. |
Michajłow M.^{♦}, Szolc T., Jankowski Ł., Konowrocki R., Semi-Active Reduction of Vibrations of Periodically Oscillating System,
Solid State Phenomena, ISSN: 1662-9779, DOI: 10.4028/www.scientific.net/SSP.248.111, Vol.248, pp.111-118, 2016Streszczenie: Periodical vibrations are common phenomenon affecting a wide range of mechanical systems. Most frequently it affects machines designed to work in a steady-state conditions like: turbine, pump, rail vehicle, etc. In those kinds of machines it is always possible to decompose the system motion to basic average-speed constant component and oscillatory component. Usually the second term is treated as undesirable and various techniques are applied in order to minimize it as far as it is possible. These techniques refers to both the hardware selection – meaning the type of damping system (active, semi-active, passive) and the control method selection – meaning the damping system control method. Concerning the control methods, there are many algorithms available in literature devoted to transient systems. One of typical application is to use them in systems experiencing sudden, external force excitation. After destabilization of the system, caused by excitation, the role of the control algorithm is to restore the system stable position and additionally to reach the extreme of some additional criterion. Typical criterions are minimization of the time, of restoring the stable position, minimizing the consumed control energy, etc. On the other hand, considering the steady-state systems, especially based on semi-active damping elements, there are not so many control methods available.This paper focuses on developing the proper methodology for deriving the optimal control strategy of semi-active damping element, to be used in periodically vibrating mechanical system. The control strategy is developed on the basis of the Optimal Control Theory. Numerical computations are involved in order to solve the optimal control problem for the considered test system. Problem solution reveals the periodical nature of optimal control function. Słowa kluczowe: Optimal Control Theory, Periodical Vibrations, Vibration Reduction Afiliacje autorów:
Michajłow M. | - | inna afiliacja | Szolc T. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN |
| |
18. |
Konowrocki R., Pręgowska A., Szolc T., Experimental and numerical investigations for the controlled rotary damper dynamically interacting with the electromechanical rotating system,
SOLID STATE PHENOMENA, ISSN: 1012-0394, DOI: 10.4028/www.scientific.net/SSP.240.198, Vol.240, pp.198-205, 2016Streszczenie: In the paper dynamic electromechanical coupling between the structural model of the rotating machine drive system and the circuit model of the asynchronous motor has been investigated. By means of the computer model of the rotating machine drive system the results of experimental testing have been confirmed. From the obtained results of computations and measurements it follows that the coupling between the considered rotating system and the installed rotary dampers with the magneto-rheological fluid (MRF) results in effective energy dissipation leading to significant reduction of undesired torsional vibrations. Słowa kluczowe: Electromechanical Coupling, Machine Drive Systems, Rotary MRF Actuator, Torsional Vibrations, Wavelet Transform (WT) Afiliacje autorów:
Konowrocki R. | - | IPPT PAN | Pręgowska A. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
| |
19. |
Lasota R., Stocki R.^{♦}, Tauzowski P., Szolc T., Polynomial chaos expansion method in estimating probability distribution of rotor-shaft dynamic responses,
BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.1515/bpasts-2015-0047, Vol.63, No.2, pp.413-422, 2015Streszczenie: The main purpose of the study is an assessment of computational efficiency of selected numerical methods for estimation of vibrational response statistics of a large multi-bearing turbo-generator rotor-shaft system. The effective estimation of the probability distribution of structural responses is essential for robust design optimization and reliability analysis of such systems. The analyzed scatter of responses is caused by random residual unbalances as well as random stiffness and damping parameters of the journal bearings. A proper representation of these uncertain parameters leads to multidimensional stochastic models. Three estimation techniques are compared: Monte Carlo sampling, Latin hypercube sampling and the sparse polynomial chaos expansion method. Based on the estimated values of the first four statistical moments the probability density function of the maximal vibration amplitude is evaluated by the maximal entropy principle method. The method is inherently suited for an accurate representation of the probability density functions with an exponential behavior, which appears to be characteristic for the investigated rotor-shaft responses. Performing multiple numerical tests for a range of sample sizes it was found that the sparse polynomial chaos method provides the best balance between the accuracy and computational effectiveness in estimating the unknown probability distribution of the maximal vibration amplitude. Słowa kluczowe: stochastic moment estimation, sparse polynomial chaos expansion, maximum entropy principle, rotor, uncertainties, hybrid mechanical model, random unbalance distribution Afiliacje autorów:
Lasota R. | - | IPPT PAN | Stocki R. | - | inna afiliacja | Tauzowski P. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
| | 20p. |
20. |
Szolc T., Konowrocki R., Michajłow M.^{♦}, Pręgowska A., An investigation of the dynamic electromechanical coupling effects in machine drive systems driven by asynchronous motors,
MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2014.04.004, Vol.49, pp.118-134, 2014Streszczenie: In the paper dynamic electromechanical interaction between the rotating machine drive system and the electric driving motor is considered. The investigations are performed by means of the circuit model of the asynchronous motor as well as using an advanced structural hybrid model of the drive system. Using the analytical solutions applied for the electrical and the mechanical systems the electromagnetic stiffness and coefficient of damping, both generated by the electric motor rotationally interacting with the mechanical system of the given dynamic properties, were determined. By means of experimentally validated computational responses obtained for torsional harmonic excitation induced by the driven machine working tool, a modification of dynamic properties of the mechanical system by the electromagnetic flux between the stator and the rotor has been studied. Słowa kluczowe: Machine drive system, Asynchronous motor, Electromechanical coupling Afiliacje autorów:
Szolc T. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN | Michajłow M. | - | inna afiliacja | Pręgowska A. | - | IPPT PAN |
| | 40p. |
21. |
Szolc T., Kowalewski Z.L., An application of longitudinal elastic waves for investigation of materials under high strain rates using the Hopkinson bar,
VIBRATIONS IN PHYSICAL SYSTEMS, ISSN: 0860-6897, Vol.26, pp.305-310, 2014Streszczenie: In the paper there is presented a discrete - continuous model of the Split Hopkinson Pressure Bar (SHPB) for numerical simulations of a dynamic behaviour of material specimens under high strain - rates. For this purpose several material theories describing visco-elasto-plastic properties of the tested specimens can be applied. Using this model impact-type dynamic responses are sought by means of the longitudinal elastic wave analytical solution of the d’Alembert type. The proposed model enables us theoretical strength investigations for various elasto-plastic materials under great deformation velocities as well as structural parameter de termination of the real SHPB designed to play a role of the laboratory test-rig. Słowa kluczowe: Hopkinson bar, elastic wave propagation, d’Alembert solution, numerical simulation Afiliacje autorów:
Szolc T. | - | IPPT PAN | Kowalewski Z.L. | - | IPPT PAN |
| | 4p. |
22. |
Pręgowska A., Konowrocki R., Szolc T., Analysis of rotating systems using actuators with magnetorheological fluid to vibration minimization – theoretical and experimental investigation,
Symulacja w Badaniach i Rozwoju, ISSN: 2081-6154, Vol.5, No.3, pp.191-198, 2014Streszczenie: The analysis of damped rotating systems using actuators with magnetorheological fluid is the subject of interest. The main purpose of this research is minimization of vibration amplitudes in order to increase fatigue durability of the most responsible machine elements. Here, control damping torques are generated by magnetorheological fluid of adjustable viscosity.
The theoretical investigations are based on a hybrid and finite element structural model (FEM) of the mechanical structure as well as on sensitivity analysis of the response with respect to the actuators damping characteristics. The analysis performed in the paper combines experimental verification using the laboratory test rig with theoretical computations. Słowa kluczowe: rotating systems, torsional vibrations, actuators with a magnetorheological fluid, rotary actuators Afiliacje autorów:
Pręgowska A. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
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23. |
Pręgowska A., Konowrocki R., Szolc T., On the semi-active control method for torsional vibrations in electro-mechanical systems by means of rotary actuators with a magneto-rheological fluid,
JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, Vol.51, No.4, pp.979-992, 2013Streszczenie: The aim of this paper is to present a method of the semi-active control of torsional vibrations in a working machine drive system by means of rotary actuators with a magneto-rheological fluid. The simple open-loop control strategy is proposed for a mechanical system vibrating in steady-state operating conditions. This semi-active control approach is based on the principle of optimum viscous damping and frictional properties realized by the magneto-rheological fluid, where its respective parameters are determined by the applied control electric currents. The analysis is performed theoretically by means of structural electro-mechanical models of the considered drive system as well as experimentally using a laboratory test rig in the form of a rotor-shaft system co-operating with two asynchronous motors generating properly programmed driving and retarding electro-magnetic torques Słowa kluczowe: semi-active control, torsional vibrations, magneto-rheological rotary dampers Afiliacje autorów:
Pręgowska A. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
| | 15p. |
24. |
Pręgowska A., Konowrocki R., Szolc T., Semi-active vibration control using a rotary magnetorheological damper – experimental verification,
POMIARY - AUTOMATYKA - ROBOTYKA. PAR, ISSN: 1427-9126, Vol.2, pp.487-491, 2013Streszczenie: From all kinds of vibrations, torsional ones are very important as naturally associated with fundamental rotational drive system motion. The aim of this paper is to present semi-active control of torsional vibrations of the working machine drive systems, which is performed using a rotary damper with the magnetorheological fluid. The main purpose of this research is vibration amplitudes minimization in order to increase fatigue durability of the most responsible machine elements. The special control strategies are proposed for steady-state torsional vibrations suppression. The semi-active control method is based on a principle of determinational optimum current damping coefficient values, which is realized by the magneto-rheological fluid application. The analysis performed in the paper combines experimental verification using the laboratory test rig with theoretical computations. This experiment was designed in the form of the laboratory drive system co-operating with two asynchronous motors generating properly programmed driving and retarding electromagnetic torques. Słowa kluczowe: semi-active control, torsional vibrations, rotary dampers, magnetorheological fluid, electromechanical drive system Afiliacje autorów:
Pręgowska A. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
| | 4p. |
25. |
Stocki R., Szolc T., Tauzowski P., Knabel J., Robust design optimization of the vibrating rotor shaft system subjected to selected dynamic constraints,
MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2011.07.023, Vol.29, pp.34-44, 2012Streszczenie: The commonly observed nowadays tendency to weight minimization of rotor-shafts of the rotating machinery leads to a decrease of shaft bending rigidity making a risk of dangerous stress concentrations and rubbing effects more probable. Thus, a determination of the optimal balance between reducing the rotor-shaft weight and assuring its admissible bending flexibility is a major goal of this study. The random nature of residual unbalances of the rotor-shaft as well as randomness of journal-bearing stiffness have been taken into account in the framework of robust design optimization. Such a formulation of the optimization problem leads to the optimal design that combines an acceptable structural weight with the robustness with respect to uncertainties of residual unbalances – the main source of bending vibrations causing the rubbing effects. The applied robust optimization technique is based on using Latin hypercubes in scatter analysis of the vibration response. The so-called optimal Latin hypercubes are used as experimental plans for building kriging approximations of the objective and constraint functions. The proposed method has been applied for the optimization of the typical single-span rotor-shaft of the 8-stage centrifugal compressor. Słowa kluczowe: Rotor-shaft system, Robust design optimization, Lateral vibrations, Rubbing effects, Random unbalance distribution Afiliacje autorów:
Stocki R. | - | IPPT PAN | Szolc T. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Knabel J. | - | IPPT PAN |
| | 45p. |
26. |
Szolc T., Pochanke A.^{♦}, Dynamic investigations of electromechanical coupling effects in the mechanism driven by the stepping motor,
JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, Vol.50, No.2, pp.653-673, 2012Streszczenie: In the paper, an analysis of transient and steady-state electro-mechanical vibrations of a precise drive system driven by a stepping motor is performed. These theoretical investigations are based on a hybrid structural model of the mechanical system as well as on the classical circuit model of the stepping motor. The main purpose of these studies is to indicate essential differences between the torsional dynamic responses obtained for the considered object regarded respectively as electromechanically coupled and uncoupled. From the computational results, it follows that these differences are qualitatively and quantitatively essential from the viewpoint of possibly precise and reliable operation of the drive systems. Here, torsional vibrations of the drive system significantly influence the electro-mechanical coupling effects, which emphasizes the ir importance in dynamic analyses Słowa kluczowe: electro-mechanical vibrations, drive system, stepping motor,hybrid model Afiliacje autorów:
Szolc T. | - | IPPT PAN | Pochanke A. | - | Politechnika Warszawska (PL) |
| | 15p. |
27. |
Stocki R., Lasota R., Tauzowski P., Szolc T., Scatter assessment of rotating system vibrations due to uncertain residual unbalances and bearing properties,
COMPUTER ASSISTED METHODS IN ENGINEERING AND SCIENCE, ISSN: 2299-3649, Vol.19, pp.95-120, 2012Streszczenie: The main objective of the presented study is an evaluation of the effectiveness of various methods for estimating statistics of rotor-shaft vibration responses. The computational effectiveness as well as the accuracy of statistical moment estimation are essential for efficient robust design optimization of the rotor-shaft systems. The compared methods include sampling techniques, the perturbation approach, the dimension reduction method and the polynomial chaos expansion method. For comparison, two problems of the rotor-shaft vibration analysis are considered: a typical single-span rotor-shaft of the 8-stage centrifugal compressor driven by the electric motor and a large multi-bearing rotor-shaft system of the steam turbo-generator. The most important reason for the observed scatter of the rotor-shaft vibration responses is the inherently random nature of residual unbalances as well as stiffness and damping properties of the journal bearings. A proper representation of these uncertain parameters leads to multidimensional stochastic models. It was found that methods that provide a satisfactory balance between the estimation accuracy and computational effectiveness are sampling techniques. On the other hand, methods based on Taylor series expansion in most of the analysed cases fail to approximate the rotor-shaft response statistics. Słowa kluczowe: Scatter analysis, rotor-shaft vibrations Afiliacje autorów:
Stocki R. | - | IPPT PAN | Lasota R. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
| | 6p. |
28. |
Pręgowska A., Konowrocki R., Szolc T., Experimental verification of the semi-active control concepts for torsional vibrations of the electro-mechanical system using rotary magneto-rheological actuators,
VIBRATIONS IN PHYSICAL SYSTEMS, ISSN: 0860-6897, Vol.25, pp.329-334, 2012Streszczenie: In the paper semi-active control of torsional vibrations of the rotating machine drive system driven by an electric motor is performed by means of rotary actuators with the magneto-rheological fluid. The main purpose of these studies is a minimisation of vibration amplitudes in order to increase the fatigue durability of the most responsible elements, assure possibly precise motion of the driven machine working tool as well as to reduce a generated noise level. For suppression of steady-state torsional vibrations excited by dynamic external torques generated by the motor and by the driven object there are proposed control strategies based on a principle of optimum current damping coefficient values realized by the magneto-rheological fluid. The theoretical control concepts are experimentally verified using the laboratory test rig in the form of drive system co-operating with two asynchronous motors generating properly programmed driving and retarding electromagnetic torques. Słowa kluczowe: semi-active control, torsional vibrations, rotary actuators, magneto-rheological fluid Afiliacje autorów:
Pręgowska A. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
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29. |
Michajłow M.^{♦}, Konowrocki R., Szolc T., Vibration control of the rotating machine geared drive system using linear actuators with the magneto-rheological fluid,
VIBRATIONS IN PHYSICAL SYSTEMS, ISSN: 0860-6897, Vol.25, pp.279-284, 2012Streszczenie: In this paper there is proposed a semi-active control technique based on the linear actuators with the magneto-rheological fluid (MRF) connecting the drive system planetary gear housing with the immovable rigid support. Here, control damping torques are generated by means of the magneto-rheological fluid of adjustable viscosity. Such actuators can effectively suppress amplitudes of severe transient and steady-state rotational fluctuations of the gear housing position and in this way they are able to minimize dangerous oscillations of dynamic torques transmitted by successive shaft segments in the entire drive system. The general purpose of the considerations is to control torsional vibrations of the real power-station coal-pulverizer geared drive system driven by means of the asynchronous motor. The investigations have been carried out using the experimental test rig based on the real object, where the measurement results were compared with analogous theoretical ones obtained by the use of computer simulations. Słowa kluczowe: torsional vibrations, magneto-rheological dampers, semi-active control Afiliacje autorów:
Michajłow M. | - | inna afiliacja | Konowrocki R. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
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30. |
Pochanke A.^{♦}, Szolc T., Oddziaływanie elektromechaniczne w systemie napędowym z silnikiem skokowym,
PRZEGLĄD ELEKTROTECHNICZNY, ISSN: 0033-2097, Vol.87, No.11, pp.64-67, 2011Streszczenie: W pracy przedstawiono model matematyczny do badania dynamicznego oddziaływania między częściami elektromechanicznymi w systemie napędowym z hybrydowym silnikiem skokowym. W przypadku takiego systemu musi być zapewniony precyzyjny ruch obrotowy, dlatego już w procesie projektowania trzeba przewidzieć i uwzględnić efekt sprzężenia elektromechanicznego, a można to uczynić jedynie z wykorzystaniem dostatecznie dokładnych modeli matematycznych układu mechanicznego i silnika napędowego. Z przeprowadzonych obliczeń symulacyjnych wynika, że wpływ oddziaływania elektromechanicznego na właściwości systemu napędowego z silnikiem skokowym może być znaczne. Słowa kluczowe: układ napędowy, silnik skokowy, oddziaływanie elektromechaniczne, modele matematyczne Afiliacje autorów:
Pochanke A. | - | Politechnika Warszawska (PL) | Szolc T. | - | IPPT PAN |
| | 15p. |
31. |
Szolc T., Pochanke A.^{♦}, Transient and steady-state coupled elektro-mechanical vibration analysis of the micro-drive system,
VIBRATIONS IN PHYSICAL SYSTEMS, ISSN: 0860-6897, Vol.24, pp.411-416, 2010Streszczenie: In the paper there is performed an analysis of transient and steady-state electro-mechanical vibration s of the laboratory micro-drive system driven by the stepping motor. The main purpose of these studies is to indicate significant differences between the dynamic responses obtained for the considered object regarded respectively as electro-mechanically coupled and uncoupled. These theoretical investigations are based on a hybrid structural model of the mechanical system as well as on the classical circuit model of the stepping motor. From the computational results it follows that these differences are qualitatively and quantitatively essential from the viewpoint of possibly precise and reliable operation of the micro-drive systems. Słowa kluczowe: Transient coupled elektromechanical, vibration analysis, micro-drive system Afiliacje autorów:
Szolc T. | - | IPPT PAN | Pochanke A. | - | Politechnika Warszawska (PL) |
| | 6p. |
32. |
Szolc T., Tauzowski P., Knabel J., Stocki R., Nonlinear and parametric coupled vibrations of the rotor-shaft system as fault identification symptom using stochastic methods,
NONLINEAR DYNAMICS, ISSN: 0924-090X, Vol.57, pp.533-557, 2009Streszczenie: In the paper several stochastic methods for detection and identification of cracks in the shafts of rotating machines are proposed. All these methods are based on the Monte Carlo simulations of the rotor-shaft lateral-torsional-longitudinal vibrations mutually coupled by transverse cracks of randomly selected depths and locations on the shaft. For this purpose there is applied a structural hybrid model of a real cracked rotor-shaft. This model is characterized by a high practical reliability and great computational effi-ciency, so important for hundreds of thousands numerical simulations necessary to build databases used in solving the inverse problem, i.e. crack parameter identifications. In order to ensure a good identification accuracy, for creating the Monte Carlo samples of data points there are proposed special probability density functions for locations and depths of the crack. Such an approach helps in enhancing databases corresponding to the most probable faults of the rotor-shaft system of the considered rotor machine. In the presentedstudy six different database sizes are considered to compare identification efficiency and accuracy of considered methods. A sufficiently large database enables us to estimate almost immediately (usually in less than one second) the crack parameters with precision that is in most of the cases acceptable in practice. Then, as a next stage, one of the proposed fast improvement algorithms can be applied to refine identification results in a reasonable time. The proposed methods seem to provide very convenient diagnostic tools for industrial applications. Słowa kluczowe: Crack rotor dynamics, Nonlinear and parametric vibrations, Hybrid modeling, Monte Carlo simulation, Crack identification methods Afiliacje autorów:
Szolc T. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Knabel J. | - | IPPT PAN | Stocki R. | - | IPPT PAN |
| | 32p. |
33. |
Szolc T., Tauzowski P., Stocki R., Knabel J., Damage identification in vibrating rotor-shaft systems by efficient sampling approach,
MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, Vol.23, pp.1615-1633, 2009Streszczenie: In the paper a stochastic method for fault detection and identification in the shafts of rotating machines is proposed. This approach is based on the Monte Carlo simulations of rotor-shaft lateral–torsional–longitudinal vibrations mutually coupled by transverse cracks of various possible and randomly selected depths and locations on the shaft. For this purpose the structural hybrid model of a real faulty object is applied. This model is characterized by a high practical reliability and great computational efficiency, so important for many hundred thousand single numerical simulations necessary for a creation of the databases applied for inverse problem solution finally leading to crack identification. These databases are created with an arbitrary assumed probability densities of crack parameters which ensures appropriate spread of the dynamic responses of the considered faulty mechanical system. A sufficiently large database determined for the investigated object enable us to estimate almost immediately, i.e. within less than 1 s, the crack depth and axial position with identification errors not exceeding 9% and 5%, respectively. Thus, the proposed method seems to be a very convenient diagnostic tool for engineering applications in the industry. Słowa kluczowe: Rotor-shaft system, Dynamic diagnostics, Crack identification, Monte Carlo simulation, Coupled vibration analysis Afiliacje autorów:
Szolc T. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Stocki R. | - | IPPT PAN | Knabel J. | - | IPPT PAN |
| | 32p. |
34. |
Bednarek T., Sosnowski W., Szolc T., Elasto-plastic material model with damage parameter in metal fatigue,
COMPUTER METHODS IN MATERIALS SCIENCE / INFORMATYKA W TECHNOLOGII MATERIAŁÓW, ISSN: 1641-8581, Vol.9, No.4, pp.208-210, 2009Streszczenie: In this paper the numerical method for prediction of fatigue life of structure is presented. The fmite element model-ling and damage parameter calculation are based on the algorithm de-scribed originally by Chaboche (1987), Luccioni et al. (1996) and 011er et al. (2005). This al-gorithm is simplified, i.e. the Goodman relationships between the mean and stress amplitude are included. It is extended and applied for simulation of crack propagation in the rotor shaft. The mate-rial constitutive model includes plastic effects and damage. The S—N fatigue func-tions taken from experiment are modi-fied so as to be dependent on the real ratio between minimum and maximum stress in the critical zones. So the coupling between damage, plastic-ity and fatigue is taken into account. Słowa kluczowe: metal fatigue, damage mechanics Afiliacje autorów:
Bednarek T. | - | IPPT PAN | Sosnowski W. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
| | 6p. |
35. |
Szolc T., Jankowski Ł., Active control of transient torsional vibrations due to run-up of a rotor machine driven by the electric motor,
VIBRATIONS IN PHYSICAL SYSTEMS, ISSN: 0860-6897, Vol.23, pp.341-346, 2008Streszczenie: In the paper active control of transient torsional vibrations induced by the electric motor during run-ups of the radial compressor drive system is performed by means of couplings with the magneto-rheological fluid. The main purpose of these studies is a minimisation of vibration amplitudes in order to increase the fatigue durability of the most responsible elements. The theoretical investigations are based on a hybrid structural model of the vibrating mechanical system and sensitivity analysis of the response with respect to the damping characteristics of the control couplings. Słowa kluczowe: active control, transient vibrations, drive system, electric motor Afiliacje autorów:
Szolc T. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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36. |
Szolc T., Continuous elastic macro-elements as a natural alternative crack detection tool to the spectral finite element method,
ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.59, No.6, pp.365-391, 2007Streszczenie: IN THE PAPER the wave method of fault identification in rods, shafts and beams is proposed. This method is based on dynamical models consisting of structural macro-elements with continuously distributed inertial-visco-elastic properties, represented by individual segments of the investigated objects. The fault detection and identifi-cation reduces to simulations of diagnostic wave propagation and wave reflections in these models. These simulations are performed directly in time domain by means of analytical solutions of the partial differential equations of motion. In the computa-tional examples, reflected waves were sought in the cracked cantilever rod and beam. These results have been compared with the analogous findings obtained by other au-thors, using the spectral finite element method. The natural continuous character of the applied elastic macro-elements enables us to apply a straightforward simulation of wave effects, which makes the proposed approach a promising and effective tool for fault identification in various structure and mechanical systems. Słowa kluczowe: Continuous elastic macroelements, crack detection, spectral finite element method Afiliacje autorów:
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37. |
Szolc T., Sosnowski W., On partial hydrodynamic lubrication effects in the journal bearings,
COMPUTER METHODS IN MATERIALS SCIENCE / INFORMATYKA W TECHNOLOGII MATERIAŁÓW, ISSN: 1641-8581, Vol.7, No.1, pp.94-100, 2007Streszczenie: The objective of this research is to include mixed friction effects into existing models of hydrodynamic journal bearings described e.g. in [1]. The problem of partial hydrodynamic lubrication caused by roughness of sliding surfaces has been investigated for many years by numerous researchers. But majority of theoretical studies in this field were focused on very fundamental aspects taking into consideration general principles of bearing operation from the viewpoint of flow determination between sliding surfaces of various roughness description. The considerations in this paper are devoted to partial hydrodynamic lubrication effects in typical cylindrical transverse journal bearings applied for supporting of heavy rotor-shafts of the rotating machines. For this purpose there is used the average flow theory for an oil film interaction with rough journals and bushings. In order to carry out a qualitative analysis of the problem a simple mechanical model of the partially lubricated “super-bearing” is assumed. This model consists of the rigid mass rotating with constant speed and performing translational in-plane motion within the non-rotating rigid ring which is elastically suspended in this plane. The rigid mass represents the entire inertia of the rotating parts of the rotor machine and the rigid ring corresponds to the housing of such “super bearing”. Translational in-plane motion of the rigid mass is coupled with translational motion of the rigid ring by means of mass-less springs and dampers representing respectively visco-elastic properties of the oil film in the “super-bearing” with rough sliding surfaces. These visco-elastic properties of the oil film in such bearing are determined by numerical solving of the average Reynolds equation describing partial oil flow between the rough journal and bushing. Here, according to, the pressure flow factors and the shear flow factors standing in the average Reynolds equations are determined analytically using proper empirical formulae obtained by numerical simulations of the model flows between partially lubricated surfaces for various roughness geometry and average oil film thicknesses. Solving in this way the average Reynolds equation for the entire oil gap by means of the finite difference method enables us to determine resultant viscous friction retarding force as well as transverse hydrodynamic load of the bearing. For various roughness geometry the former enables us to determine the frictional power yielded by the bearing and the latter makes possible calculation of stiffness and damping coefficients of the mass-less springs representing visco-elastic properties of the oil film in the assumed model of the “super-bearing”. In the numerical examples numerous roughness amplitudes of the journal and the bushing surface as well as various directional orientations of roughness asperities, which follow from final machining of the journal and the bushing, are taken into consideration in order to investigate their influence on kineto-static and dynamic behaviour of the transverse oil-film bearing. In the next steps of research in this field, beyond the partial lubrication, also the metal-to-metal friction effects are going to be investigated, i.e. for so high loadings of the journal bearing, when the hydrodynamic lubrication theory for the oil film stops to be in force Słowa kluczowe: partial hydrodynamic lubrication, journal bearings, mixed friction effects Afiliacje autorów:
Szolc T. | - | IPPT PAN | Sosnowski W. | - | IPPT PAN |
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38. |
Szolc T., On dynamic interaction between the runway and the aircraft landing gear using the analytical approach,
Machine Dynamics Research, ISSN: 2080-9948, Vol.30, pp.73-96, 2006Streszczenie: High static and dynamic overloads caused by the aircraft landing gears moving on the airport runways are a source of uncontrolled cracking of the runway upper layers. In order to investigate this problem the proper analytical model of the runway under moving load is proposed. The finite distance of the runway upper layer is represented by the rectangular continuous Kirchhoff's plate resting on the visco-elastic foundation playing a role of dynamic interface with the runway supporting layer. The plate heterogeneity caused by the runway transverse notches has been taken into consideration in the form of fictitious external response-dependent elastic bending moments. The initial deflections of the runway upper layer due to thermal forces are induced in the model by the equivalent mechanical loads imposed to the plate. Excitation of the plate due to the aircraft landing-gear is represented by the set of moving non-inertial forces, mutual spacing and number of which correspond respectively to the structure and the total number of wheels of the real landing-gear of the assumed aircraft. Numerical simulation of dynamic interaction between the runway and the aircraft landing-gear has been performed by means of the modal approach for various running speeds of the heavy aircraft. The quantities of interests are the dynamic transverse deflections of the plate as well as the normal stress in the notch cross-sections. Słowa kluczowe: dynamic overloads, dynamic interaction, runway,aircraft landing gear, analytical approach Afiliacje autorów:
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39. |
Bogacz R., Irretier H.^{♦}, Szolc T., Transient Vibration Analysis of a continuous Model of a Turbogenerator Rotor Shaft System Using Torsional Elastic Waves,
Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.53, pp.1-33, 1988 | |