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1

Analysis of scaffolding harmonic excitation

Bęc Jarosław, Błazik-Borowa Ewa, Szer Jacek

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 1

art. no. e144577

EN

Scaffolding is equipment usually used at construction sites. A scaffolding structure is lightweight and made of elements used many times. The characteristics of scaffolding make it susceptible to dynamic actions present at the structure or occurring nearby. A scaffolding structure of medium size was subjected to analysis in this paper. The structure FEM model was loaded with single force harmonic excitation with various frequencies ranging from 1 Hz to 12 Hz applied in one of many selected points on the scaffolding façade. In the first step, natural frequencies and mode shapes of the analyzed structure were calculated. Then the full dynamic analysis was carried out to obtain maximum displacements of selected control points. The relation of excitation force frequency and location to the amplitudes of generated displacement was observed. It was found that low excitation frequencies close to the natural frequencies of the structure produced vibrations ranging to large areas of the scaffolding surface. Higher excitation frequencies are usually less propagated at the scaffolding but still may produce some discomfort to the structure users in the vicinity of the excitation force location. Scaffolding is equipment usually used at construction sites. A scaffolding structure is lightweight and made of elements used many times. The characteristics of scaffolding make it susceptible to dynamic actions present at the structure or occurring nearby. A scaffolding structure of medium size was subjected to analysis in this paper. The structure FEM model was loaded with single force harmonic excitation with various frequencies ranging from 1 Hz to 12 Hz applied in one of many selected points on the scaffolding façade. In the first step, natural frequencies and mode shapes of the analyzed structure were calculated. Then the full dynamic analysis was carried out to obtain maximum displacements of selected control points. The relation of excitation force frequency and location to the amplitudes of generated displacement was observed. It was found that low excitation frequencies close to the natural frequencies of the structure produced vibrations ranging to large areas of the scaffolding surface. Higher excitation frequencies are usually less propagated at the scaffolding but still may produce some discomfort to the structure users in the vicinity of the excitation force location.

2

Experimental study of precision angle encoder

Uvarovas Povilas, Kavaliauskas Vilius, Kilikevičienė Kristina, Kilikevičius Artūras, Svilainis Paulius, Matijošius Jonas, Więckowski Dariusz

Archiwum Motoryzacji

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2020

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Vol. 90, nr 4

5--14

EN

The application of new and advanced production processes plays an important role in the development of the manufacturing industry. This trend is especially relevant to the automotive industry, where each element must ensure high quality requirements. Therefore, automating the automotive manufacturing process is necessary to ensure the highest level of control methods. For this purpose, various sensors are used, the signals of which are analyzed and the control plan itself is adjusted. Experimental investigations of a precision angle encoder were performed in the work. During the research, the dynamic characteristics of the created stand were determined. Experimental studies yielded the results of an experimental study of a precision angle encoder when the system is subjected to shock and harmonic excitation. In order to elucidate the effect of oscillations on the accuracy of a high-resolution coded precision angle encoder, primary electrical signals and their change under oscillations were recorded. Studies have shown that high-resolution code-precision angle encoders have different design responses to dynamic effects depending on the direction of the vibrations acting.

3

Investigation of the piezoelectric thimble tactile device operating modes

Bansevicius R., Dragasius E., Grigas V., Jurenas V., Mazeika D., Zvironas A.

Acta of Bioengineering and Biomechanics

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2014

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Vol. 16, no. 3

135--143

EN

A multifunctional device to transfer graphical or text information for blind or visually impaired is presented. The prototype using tactile perception has been designed where information displayed on the screen of electronic device (mobile phone, PC) is transferred by oscillating needle, touching the fingertip. Having the aim to define optimal parameters of the fingertip excitation by needle, the computational analysis of different excitation modes has been carried out. A 3D solid computational finite element model of the skin segment, comprising four main fingertip skin layers (stratum corneum, epidermis, dermis and hypodermis) was built by using ANSYS Workbench FEA software. Harmonic analysis of its stress–strain state under excitation with different frequency (up to 10000 Hz) and harmonic force (0.01 N), acting outer stratum corneum layer in normal direction at one, two or three points has been performed. The influence of the mode of dynamic loading of skin was evaluated (in terms of the tactile signal level) on the basis of the normal and shear elastic strain in dermis, where mechanoreceptors are placed. It is shown that the tactile perception of information, delivered by three vibrating pins, may be influenced by configuration of excitation points (their number and phase of loading) and the frequency of excitation.

4

Refined Approach to Electrically Excited Vibration of a Rectangular Plate with Piezoelectric Layers

Tylikowski A.

Machine Dynamics Problems

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2006

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Vol. 30, No. 1

97-111

EN

The purpose of this analytical work is to present a general model of the electro-mechanical response of a simply supported laminated plate to excitation by piezoelectric embedded actuators. The dynamic plate transverse displacement and the electric field to the excitation by the applied voltage term are determined from the solution of boundary value problem. The distribution of the piezoelectric potential is obtained by including the Maxwell electrostatics equation in the formulation. Coupled dynamics equations with respect to a plate displacement and an electric field are derived using Hamilton principle. Dynamic equations, joints conditions between sections with and without active layers as well as the mechanical and electrical boundary conditions at the plate edges form the boundary value problems. The steady-state frequency and space characteristics due to sinusoidal voltage applied to actuators are presented. The analysis generalizes previous results obtained under neglecting the in-plane components of electric displacement.

5

Charakterystyki dynamiczne zapór ziemnych i obwałowań

Kuboń P., Tatara T.

Czasopismo Techniczne. Budownictwo

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2005

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R. 102, z. 12-B

51--66

PL

W niniejszym artykule przedstawiono metodykę badań dynamicznych in situ zapór ziemych i obwałowań z zastosowaniem wibrosejsu MARK3. Rozważono również dobór dynamicznego modelu wybranych zapór ziemnych i obwałowań. Wykonano obliczenia z uwzględnieniem zastanego poziomu piętrzenia wody podczas badań dynamicznych in situ analizowanych obiektów. Model analizowanych konstrukcji przyjęto w postaci sprężystej tarczy pracującej w płaskim stanie odkształcenia. W pracy omówiono także kilka wariantów modelu dynamicznego. W poszczególnych wariantach uwzględniano odpowiednio: stałe materiałowe przyjęte na podstawie danych z literatury, naprężenia efektywne w gruncie wynikające z ciężaru wody i ciężaru gruntu, stopnie nasycenia gruntu wodą oraz masę wody związanej.

EN

The paper deals with methodology of dynamic investigation of earth dams and embankments with vibrator MARK3 as well as selection of dynamic model of chosen structures. Calculations were executed with regard of existing water level during dynamic investigation in situ of analyzed structures. In the study several variants of dynamic model have been considered. The model of analyzed structures has been assumed as elastic shield in plain strain. In particular variants of model there have been assumed: material data properties taken from literature, effective stresses in soil resulting from weights of water and soil, saturation ratio and mass of bounded water.

6

Badania odpowiedzi układu wyciągowego na wymuszenia harmoniczne

Tejszerska D.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2001

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z. 17

207-212

PL

Celem analizy częstotliwościowej jest określenie zakresu częstotliwości rezonansowych a przede wszystkim możliwego poziomu amplitud sił, naprężeń, przyspieszeń i przemieszczeń, które mogą wystąpić w systemie wyciągowym pod wpływem wymuszeń harmonicznych. W artykule przedstawiono zastosowaną metodę analizy, polegającą na automatycznym wykonywaniu ciągu symulacji ruchu układu wyciągowego pod wpływem wymuszeń harmonicznych, definiowanych w ten sposób, by zapewnić stabilizację drgań i pełną porównywalność drgań, powstających przy kolejnych częstościach wymuszeń, odpowiednio zagęszczonych w strefach rezonansowych. Załączono przykładowe rezultaty analizy, w postaci wykresów, przedstawiających charakterystyki amplitudowo-częstotliwościowe i szczegółowe przebiegi czasowe. Określono rozkład częstości rezonansowych, możliwy wzrost amplitud, wskazujący na stosunkowo niewielkie zagrożenie rezonansowe oraz stopień zróżnicowania amplitud poszczególnych parametrów przy różnych częstościach.

EN

Frequency analysis is aimed at determination of the range of resonance frequencies and chiefly of the possible level of amplitudes of forces, stresses, accelerations and displacements, which can appear in the harmonically excited hoisting system The paper presents applied method of analysis, consisting in automatic performing of many simulations of motion of the hoist, caused by harmonie excitations, defined in such manner as to ensure stabilisation of simulated vibrations and full comparability of oscillations oceurring at successive freąuencies of excitation, adequately condensed in the resonance regions. The exemplary results of analysis are included in the form of graphs, showing frequency characteristics or detailed time transients. The distribution of resonance frequencies, possible growth of amplitudes, characterising the relatively low extent of resonance hazard, and the level of diversification of changes of amplitudes of different parameters in different frequencies were determined.