Browsing by Author "Sopanen, Jussi"
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Item Adapting geometry-based polygonal contacts for simulating faulty rolling bearing dynamics(Elsevier Ltd, 2024-02) Vehviläinen, Milla; Rahkola, Pekka; Keränen, Janne; Halme, Jari; Sopanen, Jussi; Liukkonen, Olli; Holopainen, Antti; Tammi, Kari; Belahcen, Anouar; Department of Mechanical Engineering; Department of Electrical Engineering and Automation; School services, ELEC; Mechatronics; Computational Electromechanics; VTT Technical Research Centre of Finland; LUT University; ABB GroupRolling bearings are a leading cause of equipment breakdowns in electrical machines, underscoring the significance of predictive maintenance strategies. However, the given methods require high-quality big data, which is challenging to acquire, especially for faulty cases. Simulation models offer an alternative by generating large data sets to complement experimental data. However, bearings involve complex contact-related phenomena, such as slipping and clearance. Therefore, generating realistic data comparable to the real-world necessitates accuracy. Our study presents a multibody simulation system of a motor bearing, incorporating a geometry-based polygonal contact method (PCM), which accurately captures nonlinear bearing dynamics and allows for the simulation of various contact geometries. We introduce a systematic approach to adjust the PCM contact properties for rolling bearings, referencing the well-established Hertzian theory. Both healthy and faulty bearings with a local outer ring fault were simulated. The simulated output was a relative shaft displacement, experimentally validated using a capacitive sensor. Our model successfully demonstrates the potential to employ geometry-based contacts for generating realistic data on faulty bearings with the aim of predictive maintenance.Item Development and verification of frequency domain solution methods for rotor-bearing system responses caused by rolling element bearing waviness(Academic Press Inc., 2022-01-15) Choudhury, Tuhin; Kurvinen, Emil; Viitala, Raine; Sopanen, Jussi; Department of Mechanical Engineering; Mechatronics; LUT UniversityIn rotordynamic simulations, rolling element bearing waviness is often accounted using nonlinear models that are solved with a numerical integration scheme in time domain. This approach generates accurate system response, but the method is limited in terms of computational efficiency. This study proposes two novel methods for solution of the responses caused by the bearing waviness excitation in frequency domain, and compares the result with a previously developed, time domain based numerical simulation. The first method known as Base Excitation Method (BEM) considers the waviness as base excitation whereas the second method, known as Bearing Kinematics Augmented Base Excitation Method (BKA-BEM), utilizes a four degree of freedom, quasi-static model to include the bearing kinematics and refine the base excitations due to waviness. The methods are validated with a test case, in which measured low order waviness components of the bearing inner ring roundness profile were used as source for excitation. The accuracy and robustness of the proposed methods in calculating the subcritical harmonic response frequencies and amplitudes are examined for different roundness profiles. The results show that the proposed methods performed relatively well compared to previously developed, time domain solution based numerical model and experimental results. Furthermore, the frequency domain solutions significantly reduce the computational time which makes them easily applicable to simulation-based transfer learning, iterative inverse problems and optimization solutions.Item Model-based initial residual unbalance identification for rotating machines in one and two planes using an iterative inverse approach(Palac Kultury i Nauki, 2021-12) Bastakoti, Satish; Choudhury, Tuhin; Viitala, Risto; Kurvinen, Emil; Sopanen, Jussi; LUT University; Mechatronics; Department of Mechanical EngineeringTo achieve acceptable dynamical behavior for large rotating machines operating at subcritical speeds, the balancing quality check at the planned service speed in the installation location is often demanded for machines such as turbo-generators or high-speed machines. While most studies investigate the balancing quality at critical speeds, only a few studies have investigated this aspect using numerical methods at operational speed. This study proposes a novel, model-based method for inversely estimating initial residual unbalance in one and two planes after initial grade balancing for large flexible rotors operating at the service speeds. The method utilizes vibration measurements from two planes in any single direction, combined with a finite element model of the rotor to inversely determine the residual unbalance in one and two planes. This method can be practically used to determine the initial and residual unbalance after the balancing process, and further it can be used for condition-based monitoring of the unbalance state of the rotor.Item Simulation Model to Investigate Effect of Support Stiffness on Dynamic Behaviour of a Large Rotor(2020) Kurvinen, Emil; Viitala, Risto; Choudhury, Tuhin; Sopanen, Jussi; Department of Mechanical Engineering; LUT UniversityIn this study, the effect of support stiffness on the dynamic behaviour of a large industrial rotor is studied using simulation models and experimental test setup having a mechanical apparatus for changing the horizontal support stiffness. Two different simulation models with different levels of complexity were created to simulate the behaviour of the system. Such verified simulation models can be used to predict the critical speeds and minimum vibration operating speed areas. The achievements of this paper could be utilized in the industries using large rotors when operating conditions can be taken into consideration already in rotor system development.Item Simulation of Subcritical Vibrations of a Large Flexible Rotor with Varying Spherical Roller Bearing Clearance and Roundness Profiles(MDPI AG, 2020-06) Kurvinen, Emil; Viitala, Raine; Choudhury, Tuhin; Heikkinen, Janne; Sopanen, Jussi; Department of Mechanical Engineering; LUT UniversityIn large rotor-bearing systems, the rolling element bearings act as a considerable source of subcritical vibration excitation. Simulation of such rotor bearing systems contains major sources of uncertainty contributing to the excitation, namely the roundness profile of the bearing inner ring and the clearance of the bearing. In the present study, a simulation approach was prepared to investigate carefully the effect of varying roundness profile and clearance on the subcritical vibration excitation. The FEM-based rotor-bearing system simulation model included a detailed description of the bearings and asymmetricity of the rotor. The simulation results were compared to measured responses for validation. The results suggest that the simulation model was able to capture the response of the rotor within a reasonable accuracy compared to the measured responses. The bearing clearance was observed to have a major effect on the subcritical resonance response amplitudes. In addition, the simulation model confirmed that the resonances of the 3rd and 4th harmonic vibration components in addition to the well-known 2nd harmonic resonance (half-critical resonance) can be significantly high and should thus be taken into account already in the design phase of large subcritical rotors.Item Simulation-Based Transfer Learning for Support Stiffness Identification(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2021-09-08) Bobylev, Denis; Choudhury, Tuhin; Miettinen, Jesse; Viitala, Risto; Kurvinen, Emil; Sopanen, Jussi; Department of Mechanical Engineering; Mechatronics; LUT UniversityThe support structures of a rotating machine affect its overall dynamic behavior. The stiffness of the support structures often differs at the actual sites compared to the test rigs, which leads to uncertain dynamics. In this research, a novel method is developed to identify the support stiffness for an in-situ machine using a simulation-data-driven, deep learning algorithm. In this transfer learning approach, a deep learning algorithm is trained with a simulation model and then tested with measured vibration of a rotor-bearing-support system. To validate the algorithm for multiple cases, an experimental test rig with variable horizontal support stiffness is used. The results from the deep learning algorithm are compared with Linear regression (LR), Artificial Neural Network (ANN), and Support vector regression (SVR) for benchmarking. The models are trained with filtered frequency domain response, and challenges due to measurement uncertainty are analyzed. With the proposed pre-processing steps of the frequency domain response and outlier elimination, the deep learning-based virtual sensor can predict the support stiffness with reasonable accuracy, where the limiting factor is the data quality and lack of excitation at critical speed frequencies.Item Unbalance Estimation for a Large Flexible Rotor Using Force and Displacement Minimization(MDPI AG, 2020-07-14) Choudhury, Tuhin; Viitala, Risto; Kurvinen, Emil; Viitala, Raine; Sopanen, Jussi; Department of Mechanical Engineering; LUT UniversityMass unbalance is one of the most prominent faults that occurs in rotating machines. The identification of unbalance in the case of large flexible rotors is crucial because in industrial applications such as paper machines and roll grinders, high vibrations can adversely affect the quality of the end product. The objective of this research is to determine the unbalance location, magnitude and phase for a large flexible rotor with few measured coordinates. To this end, an established force-based method comprising of modal expansion and equivalent load minimization is applied. Due to the anisotropic behavior of the test rotor, the force method required at least six measured coordinates to predict the unbalance with an error of 4 to 36%. To overcome this limitation, an alternate method, eliminating the use of modal expansion, is proposed. Here, displacements generated by varying the location of a reference unbalance along the rotor axis, are compared to measured displacements to detect the unbalance location. Furthermore, instead of force-based fault models, the minimization of displacements at measured locations determines the unbalance parameters. The test case in this study is the guiding roll of a paper machine and its different unbalance states. The algorithm is tested initially with a simulation-based model and then validated with an experimental set up. The results show that the displacement method can locate the unbalance close to the actual location and it can predict the unbalance magnitude and phase with only two measured coordinates. Lastly, using measured data from 15 measurement points across the tube section of the test rotor, a comparison shows how the selection of the two measured locations affects the estimation accuracy.Item Vibration analysis of paper machine’s asymmetric tube roll supported by spherical roller bearings(2018-05-01) Heikkinen, Janne E.; Ghalamchi, Behnam; Viitala, Raine; Sopanen, Jussi; Juhanko, Jari; Mikkola, Aki; Kuosmanen, Petri; Department of Mechanical Engineering; LUT UniversityAbstract This paper presents a simulation method that is used to study subcritical vibrations of a tube roll in a paper machine. This study employs asymmetric 3D beam elements based on the Timoshenko beam theory. An asymmetric beam model accounts for varying stiffness and mass distributions. Additionally, a detailed rolling element bearing model defines the excitations arising from the set of spherical roller bearings at both ends of the rotor. The results obtained from the simulation model are compared against the results from the measurements. The results indicate that the waviness of the bearing rolling surfaces contributes significantly to the subcritical vibrations while the asymmetric properties of the tube roll have only a fractional effect on the studied vibrations.