Roman Zajac

RESEARCH INTERESTS

vibration and noise

Scopus Publications

Modal properties diagnostics of the high-pressure fuel injection pipes in off-road diesel engine
Václav Otipka, Roman Zajac, Aleš Prokop, and Kamil Řehák
JVE International Ltd.



Gear Shift Investigation Using Virtual Prototype
Aleš Prokop, Kamil Rehak, Roman Zajac, and Václav Otipka
Springer International Publishing



Vibroacoustic Diagnostics Based on the Experimental and Numerical Approach
Roman Zajac, Václav Otipka, Aleš Prokop, and Kamil Řehák
Springer International Publishing
During the last decade, many developers in the engineering industry are focusing on diagnostics and effective eliminating of the vibration and noise. The vibration and acoustic emissions are directly related to each other. Based on this fact, it is important to take into consideration the original vibration sources (engine, gearbox), but also the radiated noise to the environment. Current time brings unprecedented possibilities in the field of laboratory measurements and computational simulations in terms of hardware and software. In the issue of vibroacoustic diagnostics, the combination of these two approaches is very often required. In the first phase, the modal properties of the structure are usually examined, and the material properties are defined according to the mutual validation from both approaches. Subsequently, the amplitudes in structural (normal acceleration of the surface) and acoustic domain (sound power level—SWL, sound pressure level—SPL) are monitored during the operating conditions. In laboratory conditions, the structure is often excited by a mode exciter. In this case, the maximum amplitudes at the specific locations are primarily recorded on the structure. This article systematically describes the vibroacoustic diagnostics of the rectangular plate. Two approaches are explained in the paper: experimental and computational—based on the finite element method (FEM). In the text below, the individual procedures of the two methodologies are described. The obtained results from modal and harmonic response analyses are validated and compared with each other.


Numerical Dynamic Analysis of Gearbox Behaviour
Václav Otipka, Roman Zajac, Kamil Rehak, and Aleš Prokop
Springer International Publishing



Acoustic and Vibration Response Analysis of Heavy-Duty Gearbox
Kamil Rehak, Aleš Prokop, Roman Zajac, and Václav Otipka
Springer International Publishing



Determination of the modal parameters on the thin flat structures
Roman Zajac, Aleš Prokop, and Kamil Řehák
JVE International Ltd.
This paper presents the investigation of modal parameters using the different approaches. The object of the examination is the simple structure such as flat rectangle plate is. Before starting the measurement, there have been calculated natural frequencies of the plate by analytical approach. Subsequently, the experiment part is performed. The appropriate measuring apparatus has to be applicated for the experimental analysis. First, there are evaluated modal parameters of the specimen, the so-called “frequency sweep” is used as the input signal for excitation. After that, the experimental harmonic analysis is performed according the obtained eigen frequencies from the modal analysis. In the final stage, the data from simulations and experimental measurement are compared.


Investigation of the harmonic response on the simple structure in structural and acoustic domain by experimental and numerical approach