Publications in journals ranked by Journal Citation Reports (JCR) 
Publications in other journals ranked by Ministry of Science and Higher Education
Conference publications indexed in the Web of Science Core Collection
Publications in other journals and conference proceedings
Affiliation to IPPT PAN

1.Opiela K.C., Zieliński T.G., Microstructural design, manufacturing and dual-scale modelling of an adaptable porous composite sound absorber, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2020.107833, Vol.187, pp.107833-1-13, 2020
Opiela K.C., Zieliński T.G., Microstructural design, manufacturing and dual-scale modelling of an adaptable porous composite sound absorber, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2020.107833, Vol.187, pp.107833-1-13, 2020

Abstract:
This work investigates a porous composite with modifiable micro-geometry so that its ability to absorb noise can be accommodated to different frequency ranges. The polymeric skeleton of the composite has a specific periodic structure with two types of pores (larger and smaller ones) and two types of channels (wide and narrow ones), and each of the large pores contains a small steel ball. Depending on the situation, the balls block different channels that connect the pores, and therefore alter the visco-inertial phenomena between the saturating air and solid skeleton which take place at the micro-scale level and are responsible for the dissipation of the energy of acoustic waves penetrating the porous composite. All this is studied numerically using advanced dual-scale modelling, and the results are verified by the corresponding experimental tests of 3D-printed samples. Particular attention is paid to the prototyping and additive manufacturing of such adaptive porous composites.

Keywords:
porous composite, adaptive sound absorber, microstructure-based modelling, additive manufacturing

2.Zieliński T.G., Venegas R., Perrot C., Červenka M., Chevillotte F., Attenborough K., Benchmarks for microstructure-based modelling of sound absorbing rigid-frame porous media, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2020.115441, Vol.483, pp.115441-1-38, 2020
Zieliński T.G., Venegas R., Perrot C., Červenka M., Chevillotte F., Attenborough K., Benchmarks for microstructure-based modelling of sound absorbing rigid-frame porous media, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2020.115441, Vol.483, pp.115441-1-38, 2020

Abstract:
This work presents benchmark examples related to the modelling of sound absorbing porous media with rigid frame based on the periodic geometry of their microstructures. To this end, rigorous mathematical derivations are recalled to provide all necessary equations, useful relations, and formulae for the so-called direct multi-scale computations, as well as for the hybrid multi-scale calculations based on the numerically determined transport parameters of porous materials. The results of such direct and hybrid multi-scale calculations are not only cross verified, but also confirmed by direct numerical simulations based on the linearised Navier-Stokes-Fourier equations. In addition, relevant theoretical and numerical issues are discussed, and some practical hints are given.

Keywords:
porous media, periodic microstructure, wave propagation, sound absorption

3.Wasilewski M., Pisarski D., Adaptive semi-active control of a beam structure subjected to a moving load traversing with time-varying velocity, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2020.115404, Vol.481, pp.115404-1-20, 2020
Wasilewski M., Pisarski D., Adaptive semi-active control of a beam structure subjected to a moving load traversing with time-varying velocity, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2020.115404, Vol.481, pp.115404-1-20, 2020

Abstract:
A novel method for adaptive semi-active vibration control of structures subjected to a movingload is studied. The velocity of the load is assumed to be time-varying. The controller consistsof an internal model of the moving load, which is being frequently updated to accommodatechanges in the load's velocity. The control method relies on a near-optimal switching con-trol law that is based on the solution to the algebraic Lyapunov equation. The infinite-horizonformulation of the control problem enables us to use efficient numerical algorithms for adap-tive recomputing of the control signal. The asymptotic stability of the closed-loop system andperformance improvement in comparison to the passive method are analysed and formallyproven. The controller is tested by means of numerical experiments involving a flexible beamequipped with a set of semi-active viscous dampers. We investigate three distinct simulationscenarios, which correspond to highly non-uniform motions of the load that consist of accel-eration, deceleration and temporary halt phases. The results of the simulations are comparedto passive and optimal open-loop strategies.

Keywords:
vibration control, adaptive control, semi-active control, moving load, stabilisation

4.Błachowski B., Świercz A., Ostrowski M., Tauzowski P., Olaszek P., Jankowski Ł., Convex relaxation for efficient sensor layout optimization in large‐scale structures subjected to moving loads, Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12553, pp.1-16, 2020
Błachowski B., Świercz A., Ostrowski M., Tauzowski P., Olaszek P., Jankowski Ł., Convex relaxation for efficient sensor layout optimization in large‐scale structures subjected to moving loads, Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12553, pp.1-16, 2020

Abstract:
This paper proposes a computationally effective framework for load‐dependent optimal sensor placement in large‐scale civil engineering structures subjected to moving loads. Two common problems are addressed: selection of modes to be monitored and computational effectiveness. Typical sensor placement methods assume that the set of modes to be monitored is known. In practice, determination of such modes of interest is not straightforward. A practical approach is proposed that facilitates the selection of modes in a quasi‐automatic way based on the structural response at the candidate sensor locations to typical operational loads. The criterion used to assess sensor placement is based on Kammer's Effective Independence (EFI). However, in contrast to typical implementations of EFI, which treat the problem as a computationally demanding discrete problem and use greedy optimization, an approach based on convex relaxation is proposed. A notion of sensor density is applied, which converts the original combinatorial problem into a computationally tractable continuous optimization problem. The proposed framework is tested in application to a real tied‐arch railway bridge located in central Poland.

Keywords:
optimal sensor placement, effective independence method, Fisher information matrix

5.Jankowski Ł., Quality over quantity: the case of a model journal, Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12560, pp.649-649, 2020
6.Pisarski D., Konowrocki R., Jankowski Ł., Scalable distributed optimal control of vibrating modular structures, STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2502, Vol.27, No.4, pp.e2502-1-21, 2020
Pisarski D., Konowrocki R., Jankowski Ł., Scalable distributed optimal control of vibrating modular structures, STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2502, Vol.27, No.4, pp.e2502-1-21, 2020

Abstract:
A scalable optimal control method for structural vibration mitigation is studied. The method relies on a structure's partitioning that leads to a set of dynamically interconnected subsystems. Each subsystem is operated with an individual subcontroller that collects the local state information and collaborates with the neighboring subcontrollers to estimate a short time prediction of the interconnecting forces defining the subsystem's boundary conditions. Using the extended model that represents the subsystem's dynamics together with the evolution of its boundary conditions, each subcontroller computes the control decision based on the solution to a finite‐time horizon optimal control problem. In order to cope with the changes in the boundary conditions, the optimal solution is computed repetitively according to the receding horizon scheme. The method is validated numerically for a cantilever structure equipped with actively controlled electromagnetic actuators and subjected to a variety of initial condition scenarios. The performance of the designed controller is tested by comparisons to the centralized and isolated decentralized controllers. The introduced system partitioning and distributed controller allow performing parallel computing which makes the method fully scalable and applicable to large‐scale structures. The computational complexity of the designed distributed control is studied for different settings in the modeling of the subsystem's boundary conditions.

Keywords:
active control, distributed control, modular structure, scalable optimization, stabilization

7.Hou J., Li Z., Jankowski Ł., Wang S., Estimation of virtual masses for structural damage identification, STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2585, Vol.27, No.8, pp.e2528-1-21, 2020
Hou J., Li Z., Jankowski Ł., Wang S., Estimation of virtual masses for structural damage identification, STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2585, Vol.27, No.8, pp.e2528-1-21, 2020

Abstract:
Adding a virtual mass is an effective method for damage identification. It can be used to obtain a large amount of information about structural response and dynamics, thereby improving the sensitivity to local damage. In the current research approaches, the virtual mass is determined first, and then the modal characteristics of the virtually modified structure are identified. This requires a wide frequency band excitation; otherwise the crucial modes of the modified structure might be out of the band, which would negatively influence the modal analysis and damage identification. This paper proposes a method that first determines the target frequency and then estimates the corresponding value of the additional virtual mass. The target frequency refers to the desired value of the natural frequency after the virtual mass has been added to the structure. The virtual masses are estimated by tuning the frequency response peaks to the target frequencies. First, two virtual mass estimation methods are proposed. One is to directly calculate the virtual mass, using the frequency‐domain response at the target frequency point only, whereas the second method estimates the mass using a least‐squares fit based on the frequency‐domain response around the target frequency. Both proposed methods utilize merely a small part of the frequency domain. Therefore, an impulse, a simple harmonic, or a narrow spectral excitation can be used for damage identification. Finally, a numerical simulation of a simply supported beam and experiments of a frame structure and a truss structure are used to verify the effectiveness of the proposed method.

Keywords:
damage identification, frequency response, structural health monitoring (SHM), virtual distortion method (VDM), virtual mass

8.Konowrocki R., Chojnacki A., Analysis of rail vehicles' operational reliability in the aspect of safety against derailment based on various methods of determining the assessment criterion, EKSPLOATACJA I NIEZAWODNOŚĆ - MAINTENANCE AND RELIABILITY, ISSN: 1507-2711, DOI: 10.17531/ein.2020.1.9, Vol.22, No.1, pp.73-85, 2020
Konowrocki R., Chojnacki A., Analysis of rail vehicles' operational reliability in the aspect of safety against derailment based on various methods of determining the assessment criterion, EKSPLOATACJA I NIEZAWODNOŚĆ - MAINTENANCE AND RELIABILITY, ISSN: 1507-2711, DOI: 10.17531/ein.2020.1.9, Vol.22, No.1, pp.73-85, 2020

Abstract:
The article features the results of computer and experimental research on operational issues in the aspect of safety in relation to a freight wagon derailment on a railway track. It presents the knowledge regarding the methods of assessing the operational safety of rail vehicles on railroad tracks for the purpose of comparative analysis. The theoretical analyses were performed based on several methods that assess the safety of their derailments, qualifying for operational reliability, comparing them with the results obtained from experimental research. For the purpose of the research, a computer model of rail vehicle- railway track was created. It took into consideration dynamic parameters of elements used in the real track and rail vehicle. The results obtained from theoretical analyses were validated with experimental tests carried out on real objects (freight vehicle - test track, freight wagon - test rig). As part of the research, new test track geometry for testing rail vehicles was proposed. The results obtained in this way allowed estimating the conditions threatening the operation of a freight vehicle while running on the test rail infrastructure with different assessment criteria and to compare them.

Keywords:
operational safety, rail vehicle dynamics, derailment, experimental tests, numerical investigations

9.Hou J., Li Z., Zhang Q., Jankowski Ł., Zhang H., Local mass addition and data fusion for structural damage identification using approximate models, International Journal of Structural Stability and Dynamics, ISSN: 1793-6764, DOI: 10.1142/S0219455420501242, pp.1-24, 2020
Hou J., Li Z., Zhang Q., Jankowski Ł., Zhang H., Local mass addition and data fusion for structural damage identification using approximate models, International Journal of Structural Stability and Dynamics, ISSN: 1793-6764, DOI: 10.1142/S0219455420501242, pp.1-24, 2020

Abstract:
In practical civil engineering, structural damage identification is difficult to implement due to the shortage of measured modal information and the influence of noise. Furthermore, typical damage identification methods generally rely on a precise Finite Element (FE) model of the monitored structure. Pointwise mass alterations of the structure can effectively improve the quantity and sensitivity of measured data, while the data fusion methods can adequately utilize various kinds of data and identification results. This paper proposes a damage identification method that requires only approximate FE models and combines the advantages of pointwise mass additions and data fusion. First, an additional mass is placed at different positions throughout the structure to collect the dynamic response and obtain the corresponding modal information. The resulting relation between natural frequencies and the position of the added mass is sensitive to local damage, and it is thus utilized to form a new objective function based on the modal assurance criterion (MAC) and l1-based sparsity promotion. The proposed objective function is mostly insensitive to global structural parameters, but remains sensitive to local damage. Several approximate FE models are then established and separately used to identify the damage of the structure, and then the Dempster-Shafer method of data fusion is applied to fuse the results from all the approximate models. Finally, fractional data fusion is proposed to combine the results according to the parametric probability distribution of the approximate FE models, which allows the natural weight of each approximate model to be determined for the fusion process. Such an approach circumvents the need for a precise FE model, which is usually not easy to obtain in real application, and thus enhances the practical applicability of the proposed method, while maintaining the damage identification accuracy. The proposed approach is verified numerically and experimentally. Numerical simulations of a simply supported beam and a long-span bridge confirm that it can be used for damage identification, including a single damage and multiple damages, with a high accuracy. Finally, an experiment of a cantilever beam is successfully performed.

Keywords:
structural health monitoring (SHM), damage identification, adding mass, data fusion, objective function, modal assurance criterion (MAC)

10.Zhang Q., Hou J., Jankowski Ł., Bridge damage identification using vehicle bump based on additional virtual masses, SENSORS, ISSN: 1424-8220, DOI: 10.3390/s20020394, Vol.20, No.2, pp.394-1-23, 2020
Zhang Q., Hou J., Jankowski Ł., Bridge damage identification using vehicle bump based on additional virtual masses, SENSORS, ISSN: 1424-8220, DOI: 10.3390/s20020394, Vol.20, No.2, pp.394-1-23, 2020

Abstract:
Structural damage identification plays an important role in providing effective evidence for the health monitoring of bridges in service. Due to the limitations of measurement points and lack of valid structural response data, the accurate identification of structural damage, especially for large-scale structures, remains difficult. Based on additional virtual mass, this paper presents a damage identification method for bridges using a vehicle bump as the excitation. First, general equations of virtual modifications, including virtual mass, stiffness, and damping, are derived. A theoretical method for damage identification, which is based on additional virtual mass, is formulated. The vehicle bump is analyzed, and the bump-induced excitation is estimated via a detailed analysis in four periods: separation, free-fall, contact, and coupled vibrations. The precise estimation of bump-induced excitation is then applied to a bridge. This allows the additional virtual mass method to be used, which requires knowledge of the excitations and acceleration responses in order to construct the frequency responses of a virtual structure with an additional virtual mass. Via this method, a virtual mass with substantially more weight than a typical vehicle is added to the bridge, which provides a sufficient amount of modal information for accurate damage identification while avoiding the bridge overloading problem. A numerical example of a two-span continuous beam is used to verify the proposed method, where the damage can be identified even with 15% Gaussian random noise pollution using a 1-degree of freedom (DOF) car model and 4-DOF model.

Keywords:
structural health monitoring, damage identification, vehicle bump, additional virtual mass, bridge

11.Olaszek P., Wyczałek I., Sala D., Kokot M., Świercz A., Monitoring of the static and dynamic displacements of railway bridges with the use of inertial sensors, SENSORS, ISSN: 1424-8220, DOI: 10.3390/s20102767, Vol.20, No.10, pp.2767-1-24, 2020
Olaszek P., Wyczałek I., Sala D., Kokot M., Świercz A., Monitoring of the static and dynamic displacements of railway bridges with the use of inertial sensors, SENSORS, ISSN: 1424-8220, DOI: 10.3390/s20102767, Vol.20, No.10, pp.2767-1-24, 2020

Abstract:
In the case of the monitoring of bridges, the determination of vertical displacements is one of the most important issues. A new measuring system has been developed and implemented for assessment of railway bridges based on measurements of the structural response to passing trains. The system uses inertial sensors: Inclinometers and accelerometers that do not need any referential points. The system records signals related to the passage of a train over a monitored bridge. The signals from inclinometers before the train's entry are used to determine the static movement. Integrated signals from inclinometers and accelerometers are used to determine dynamic displacements when the train goes through the bridge. Signals from inclinometers are used to determine the so-called "quasi-static" component of the displacement and signal from the accelerometer to determine the dynamic component. Field tests have been carried out on a viaduct along a high-speed railway line. Periodic comparative measurements are carried out using a Total Station to verify static measurements and using inductive sensors to verify dynamic measurements. Tests of the system carried out so far have proven its usefulness for monitoring bridges in a high-speed railway (up to 200 km/h) with high accuracy while determining dynamic displacements.

Keywords:
bridge monitoring, dynamic and static displacements, inertial sensors, total station, indirect measurement

12.Faraj R., Mikułowski G., Wiszowaty R., Study on the state-dependent path-tracking for smart pneumatic shock-absorber, SMART MATERIALS AND STRUCTURES, ISSN: 0964-1726, DOI: 10.1088/1361-665X/ab9adc, pp.1-25, 2020
Faraj R., Mikułowski G., Wiszowaty R., Study on the state-dependent path-tracking for smart pneumatic shock-absorber, SMART MATERIALS AND STRUCTURES, ISSN: 0964-1726, DOI: 10.1088/1361-665X/ab9adc, pp.1-25, 2020

Abstract:
The paper presents an analysis of the state-dependent path-tracking method devoted to mitigation of dynamic response of systems and structures under impact excitations. The objective of the study is an evaluation of the adaptive performance and robustness of the novel control method. Robust and adaptive control methods are intensively developed by researchers and control engineers. Progress in the field influences various areas including mechanical engineering, within which these methods are applied for control of industrial processes as well as mitigation of structure dynamic response. Commonly solved problems relate especially to mitigation of vibrations, e.g. for protection of seismically excited structures. Another closely related area is the field of impact absorption, which is still challenging because of short time periods of energy absorption and number of process uncertainties. Nevertheless, due to higher and higher performance of smart sensors and actuators, as well as increasing efficiency of data processing systems, novel high- performance solutions also for impact mitigation problems can be proposed. This fact is reflected in the paper and important contribution to the field of Adaptive Impact Absorption is demonstrated. The importance of presented study results from the fact that applied smart absorber controlled with the use of kinematics-based approach ensures efficient mitigation of the impact excitation and automatic adaptation to various loading conditions. In contrast to shock-absorbers developed so far, the system implemented in laboratory provides adaptation to unknown impact conditions and compensates the influence of unpredictable perturbations. Within the paper an experimental validation of the novel control method is discussed and the system robustness to contact conditions, as well as to different values of operational medium parameters, is demonstrated. Possible extension of the method is analyzed and directions of further research are indicated.

Keywords:
adaptive impact absorption, experimental study, kinematic feedback control, pneumatic absorber, self-adaptive system, smart shock-absorber

13.Błachowski B., Tauzowski P., Lógó J., Yield limited optimal topology design of elastoplastic structures, STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/s00158-019-02447-9, pp.1-24, 2020
Błachowski B., Tauzowski P., Lógó J., Yield limited optimal topology design of elastoplastic structures, STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/s00158-019-02447-9, pp.1-24, 2020

Abstract:
This study is devoted to a novel method for topology optimization of elastoplastic structures subjected to stress constraints. It should be noted that in spite of the classical solutions of the different type of elastoplastic topology problems are more than 70 years old, the integration of the Prandtl-Reuss constitutive equations into the topology optimization process is not very often investigated in the last three decades. In the presented methodology where the classical variational principles of plasticity and the functor-oriented programming technique are applied in topology design, the aim is to find a minimum weight structure which is able to carry a given load, fulfills the allowable stress limit, and is made of a linearly elastic, perfectly plastic material. The optimal structure is found in an iterative way using only a stress intensity distribution and a return mapping algorithm. The method determines representative stresses at every Gaussian point, averages them inside every finite element using the von Mises yield criterion, and removes material proportionally to the stress intensities in individual finite elements. The procedure is repeated until the limit load capacity is exceeded under a given loading. The effectiveness of the methodology is illustrated with three numerical examples. Additionally, different topologies are presented for a purely elastic and an elastoplastic material, respectively. It is also demonstrated that the proposed method is able to find the optimal elastoplastic topology for a problem with a computational mesh of the order of tens of thousands of finite elements.

Keywords:
topology optimization, elastoplastic structures, minimum-weight design, stress constraints

14.Knap L., Graczykowski C., Holnicki-Szulc J., Wołejsza Z., Strategies for reduction of energy consumption during ascending and descending process of modern telescopic HAPS aerostats, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2020.131833, Vol.68, No.1, pp.155-168, 2020
Knap L., Graczykowski C., Holnicki-Szulc J., Wołejsza Z., Strategies for reduction of energy consumption during ascending and descending process of modern telescopic HAPS aerostats, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2020.131833, Vol.68, No.1, pp.155-168, 2020

Abstract:
In this article, the authors propose and investigate a new concept of HAPS aerostat design in a modular form, which allows for sequential increasing or decreasing of the total volume, up to the desired size. In its initial form, the aerostat has relatively small dimensions but its central cylindrical part is multi-segmented and can be easily extended. The application of controllable construction couplings enables precise control of the aerostat expansion process and significantly improves its vertical mobility. The paper describes details of telescopic aerostat construction, presents a mathematical model of its vertical motion and investigates numerically two volume control strategies aimed at maximization of operation efficiency and minimization of operation cost. The results obtained reveal the main problems that have to be addressed and the factors that play a key role in design of such telescopic aerostats and control of their vertical mobility.

Keywords:
helium airship, control of vertical mobility, reduced energy consumption, optimum ascending and descending path

15.Hou J., Wang H., Xu D., Jankowski Ł., Wang P., Damage identification based on adding mass for liquid-solid coupling structures, Applied Sciences, ISSN: 2076-3417, DOI: 10.3390/app10072312, Vol.10, No.7, pp.2312-1-20, 2020
Hou J., Wang H., Xu D., Jankowski Ł., Wang P., Damage identification based on adding mass for liquid-solid coupling structures, Applied Sciences, ISSN: 2076-3417, DOI: 10.3390/app10072312, Vol.10, No.7, pp.2312-1-20, 2020

Abstract:
Damage identification for liquid–solid coupling structures remains a challenging topic due to the influence of liquid and the limitation of experimental conditions. Therefore, the adding mass method for damage identification is employed in this study. Adding mass to structures is an effective method for damage identification, as it can increase not only the experimental data but also the sensitivity of experimental modes to local damage. First, the fundamental theory of the adding mass method for damage identification is introduced. After that, the method of equating the liquid to the attached mass is proposed by considering the liquid–solid coupling. Finally, the effectiveness and reliability of damage identification, based on adding mass for liquid–solid coupling structures, are verified through experiments of a submerged cantilever beam and liquid storage tank.

Keywords:
structural health monitoring, damage identification, liquid-solid coupling, adding mass, sensitivity

16.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, 2020
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, 2020

Abstract:
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.

Keywords:
rotor dynamics, combined electrodynamic passive magnetic bearings, turbocharger flexible rotor shaft, stability analysis, stabilizing damping magnitude

17.Ostrowski M., Błachowski B., Jankowski Ł., Pisarski D., Modal energy transfer by controlled structural connections, DIAGNOSTYKA, ISSN: 1641-6414, DOI: 10.29354/diag/116692, Vol.21, No.1, pp.61-70, 2020
Ostrowski M., Błachowski B., Jankowski Ł., Pisarski D., Modal energy transfer by controlled structural connections, DIAGNOSTYKA, ISSN: 1641-6414, DOI: 10.29354/diag/116692, Vol.21, No.1, pp.61-70, 2020

Abstract:
This paper describes a semi-active control strategy that allows to transfer the vibration energy from an arbitrarily induced to a selected structural mode. The intended aim of the proposed control strategy is energy harvesting from structural vibrations. Another potential application is related to structural safety. In the paper, a mathematical model is first introduced to describe the phenomenon of vibrational energy transfer, and then, based on this model, an efficient semi-active control strategy is proposed. Finally, some problems related to measurement techniques are discussed. The effectiveness of the proposed methodology is demonstrated in an example of energy transfer between vibrational modes of a three-bar planar frame structure.

Keywords:
vibration energy, modal control, lockable joint, modal coupling