Janko Slavič - Academia.edu (original) (raw)

Papers by Janko Slavič

Additive manufacturing, Jul 1, 2023

Polymer Testing, Aug 1, 2023

This a formal release of the version 0.24

Mechanical Systems and Signal Processing, May 1, 2023

SAE International Journal of Materials and Manufacturing, Jun 30, 2014

Mechanical Systems and Signal Processing, Mar 1, 2023

Model updating improves the correlation between the response of the real structure and the respon... more Model updating improves the correlation between the response of the real structure and the response of the finite-element (FE) model; however, the selection of the updating parameters (parametrization) is crucial for its success. Using full-field modal shapes, a large number of parameters can be updated, e.g., the Young's moduli of all the finite elements; however, the structural response is not necessarily sensitive to an arbitrary parameter, making the optimization problem ill-conditioned. Additionally, the computation of the full sensitivity matrix is not feasible for relatively large FE models. Not all locations are equally important for model updating; at locations of the highest mechanical loads, more focus is required. In this research, the updating parameters are based on the curvature of the 3D full-field experimental shape, where locations with high curvature are associated with high sensitivity. The assumption is initially researched with the Euler-Bernoulli beam elements and second-order tetrahedrons. The proposed method is investigated on numerical and real experiments, where successful updating was confirmed. With the proposed parametrization and updating approach, a geometrically complex structure is parametrized and the parameters updated without significant user input, generalizing the model-updating procedure.

Polymers, Dec 29, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Mechanical Systems and Signal Processing, Mar 1, 2022

Mechanical Systems and Signal Processing, 2018

Vibration measurements using optical full-field systems based on high-speed footage are typically... more Vibration measurements using optical full-field systems based on high-speed footage are typically heavily burdened by noise, as the displacement amplitudes of the vibrating structures are often very small (in the range of micrometers, depending on the structure). The modal information is troublesome to measure as the structure's response is close to, or below, the noise level of the camera-based measurement system. This paper demonstrates modal parameter identification for such noisy measurements. It is shown that by using the Least-Squares Complex-Frequency method combined with the Least-Squares Frequency-Domain method, identification at high-frequencies is still possible. By additionally incorporating a more precise sensor to identify the eigenvalues, a hybrid accelerometer / high-speed camera mode shape identification is possible even below the noise floor. An accelerometer measurement is used to identify the eigenvalues, while the camera measurement is used to produce the full-field mode shapes close to 10 kHz. The identified modal parameters improve the quality of the measured modal data and serve as a reduced model of the structure's dynamics.

SAE Technical Paper Series, Aug 31, 2021

International Journal of Mechanical Sciences, Jul 1, 2017

The design of a damping layout can result in a frequency-focused reduction of vibration responses... more The design of a damping layout can result in a frequency-focused reduction of vibration responses. Theoretical approaches that relate the spatial-damping parameters with the frequency content of the damping are limited. This research introduces a theoretical approach to damping-layout design (location and size) with frequency-content control. Initially, the frequency-response functions (measured or simulated) are modified to obtain the required damping layout via spatial-damping identification methods. The use of these methods provides a straightforward relationship between the frequency responses and the targeted spatial damping. The Lee-Kim spatial-damping identification method is used in the presented numerical and experimental case studies. The numerical and experimental results show that the approach is capable of providing the desired frequency content. This approach can be a valuable tool for a damping-layout assessment as high damping can be achieved with a reduced amount of damping material in a single-step solution.

Strojniški vestnik, Jul 15, 2016

IEEE Transactions on Magnetics, Nov 1, 2013

Journal of Sound and Vibration, Nov 1, 2018

High-speed camera measurements are increasingly being used in modal analysis to instantaneously m... more High-speed camera measurements are increasingly being used in modal analysis to instantaneously measure full-field structural responses by extracting the displacement information from images using digital-image-correlation and other optical-flow methods. High-speed cameras capable of filming full frame at high frame rates can be very expensive and produce image resolutions of only approximately 1 mega pixel, which is why this research aims at measuring and identifying the full-field response using cheaper, still-frame cameras with a higher image and intensity resolution, such as digital singlelens reflex (DSLR) and mirrorless cameras. Using spectral optical flow imaging (SOFI) full-field operational shapes can be acquired using still-frame cameras. This study demonstrates the hybrid modal-parameter identification of full-field mode shapes using an accelerometer and a DSLR camera for responses far above the DSLR camera's frame rate (demonstrated up to 1 kHz).

Mechanical Systems and Signal Processing, Jun 1, 2023

International Journal of Fatigue, Jun 1, 2023