Wyniki wyszukiwania - BazTech

1

Experimental study of the influence of using polyurethane cushion to reduce vibration received by a wheelchair user

Chwalik-Pilszyk Gabriela, Dziechciowski Zygmunt, Kromka-Szydek Magdalena, Kozień Marek S.

Acta of Bioengineering and Biomechanics

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2023

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Vol. 25, no. 1

137--149

EN

The aim of this experimental study was to compare the ability of polyurethane cushions of three arbitrary selected thicknesses to minimize vibrations transmitted from the wheelchair to its user. Methods: Measurements were made during passive motion on five different surfaces often found in public spaces. Two tests were carried out during the measurements. In the first test, the sensor was located directly on the surface of the wheelchair seat. In the second test, a polyurethane cushion was placed on the seat, on which the measuring sensor was then placed. Results: The study showed that regardless of the surface on which the wheelchair user moves, the threshold defined in the ISO standard for frequencies in the range of 4–40 Hz was exceeded. However, thanks to the use of polyurethane cushions, vibration damping was visible for frequencies ranging from 10 to 40 Hz. The impact of the user’s weight on the magnitude of the perceived vibrations was also observed. Conclusions: Studies show that wheelchair users are exposed to whole body vibration that can negatively affect their health. Cushions made of polyurethane seem to be a promising solution to reduce whole body vibration in the frequency range that is burdensome and harmful to human health.

2

Using X-ray diffraction in characterization of bone remodeling and nanocomposites in ovariectomized rats osteopenia model

Kostyshyn Nazar, Gzhegotskyi Mechyslav, Kostyshyn Liubov, Yarova Oksana, Kulyk Yuriy, Mudry Stepan

Polish Journal of Medical Physics and Engineering

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2021

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Vol. 27, Iss. 2

157--163

EN

Sedentary lifestyle and physiological menopause are among the risk factors of osteopenia, especially in elderly people. However, bone mineral density decrease can also be observed in young individuals, for instance, due to deficiency of female sex hormones after surgical interventions, particularly ovariectomy. Our research enabled us to assess the efficacy of whole-body vibration in preventing the loss of bone mineral density in the ovariectomy rat osteopenia model. Thus, whole-body vibration with acceleration level 0.3 g and frequency 50 Hz was used on young female rats, which had been subjected to ovariectomy (n = 18). It had been conducted for 24 weeks, exposure time – 30 minutes per day, 5 times a week. Assessment of mineral component loss of the tibia was performed by means of X-ray diffraction. Bone remodeling was assessed by determining hormones: parathyroid hormone and calcitonin, Ca and P in the blood. X-ray diffraction is an effective method, which enables the evaluation a nanocomposites structure of the bone tissue in the experiment. In the article, we applied this method to determine the loss of bone mineral mass after ovariectomy and the impact of wholebody vibration under such conditions. In the ovariectomy group, the volume of a mineral component significantly decreased starting already from the 16th week (р<0.05) versus control. However, in the group with ovariectomy + wholebody vibration, the loss of a mineral component was insignificant during 8-16 weeks of the investigation, compared with the control group. On the 24th day, the spectrums almost did not differ from ovariectomized rats group. Meanwhile, hormone levels changed in ovariectomized rats group. It should be emphasized that the aforementioned whole-body vibration parameters do not cause severe bone damage or further negative consequences.

3

Drgania o ogólnym działaniu na wybranych stanowiskach pracy w firmach zajmujących się przeróbką surowców mineralnych - wyniki badań własnych

Zając Jacek, Kowalski Piotr, Rejman Małgorzata

Bezpieczeństwo Pracy : nauka i praktyka

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2020

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nr 5

26-28

PL

W artykule przedstawiono wyniki badań drgań działających w sposób ogólny na 30 stanowiskach pracy związanych z przeróbką surowców mineralnych. Analiza narażenia na drgania ogólne wykazała, że na tego typu stanowiskach pracy mogą wystąpić przekroczenia wartości dopuszczalnych. Na 7 spośród zbadanych stanowisk ryzyko zawodowe ze względu na drgania ogólne oszacowano jako duże. Na 6 stanowiskach pracy wyznaczone wartości dziennych ekspozycji przekraczały 0,5 NDM (ryzyko średnie), także na 6 stanowiskach nie przekraczały 0,5 NDN (ryzyko małe). Na 11 stanowiskach ryzyko zawodowe oszacowano jako pomija/lne małel (wartości dziennych ekspozycji nie przekraczają 0,2 NDN). Uzyskane wyniki badań wskazują na potrzebę przeprowadzania pomiarów kontrolnych i oceny drgań ogólnych na stanowiskach pracy związanych z przeróbką surowców mineralnych.

EN

The paper presents the results of whole-body vibration research at 30 workstations associated with the processing of raw minerals. Measurements of the acceleration of mechanical vibrations were carried out at selected workstations located in places where the person supervising the machine/equipment works. Based on the results of the measurements, daily exposure levels to whole-body vibration and occupational risk were determined. The risk was large at 7 workstations. At 6 workstations the daily exposure values exceeded 0.5 the threshold limit value (TLV) (medium risk), at 6 workstations did not exceed 0.5 TLV(low risk). At 11 workstations daily exposure values do not exceed 0.2 TLV (negligible risk). Obtained research results indicate the need to carry out control measurements and WBV assessment at workstations associated with the processing of mineral raw materials.

4

Computational method for shaping the vibro-isolation properties of semi-active and active systems

Krzyżyński T., Maciejewski I.

Archives of Mechanics

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2019

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Vol. 71, nr 4-5

291--313

EN

The paper deals with an original methodology for modelling and control system design of the semi-active and active systems. At first a generalised simulation model of the vibration reduction system is formulated in such a way that it represents the dynamics of human body exposed to mechanical vibration. Then a novel control system design is proposed in order to adjust force characteristics of the fundamental elements included in the suspension system and consequently to reduce the harmful effects of vibration. Finally, a computational method is experimentally verified by selecting the vibro-isolation properties of an exemplary horizontal seat suspension for a specific input vibration.

5

Noise and Vibration Risk Assessment for the Operators of Crawler Loaders

Carletti Eleonora, Pedrielli Francesca

Archives of Acoustics

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2019

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Vol. 44, No. 4

761--773

EN

During work, earth-moving machines generate significant levels of noise and vibration that can be harmful for the operators; therefore the analysis of the noise and vibration conditions at the driving position is of great importance for the risk assessment. Compact loaders have become a pressing challenge as they are extremely hazardous referring to noise and vibration emissions, especially in their crawler version where further relevant noise and vibration are generated by the hard contact between track belt and ground. This paper reports the results of investigations carried out on three crawler compact loaders in different operating conditions. The main purpose was to investigate the noise and vibration values transmitted to the operators in some working conditions and use these data to obtain reliable estimates of the exposure to noise, to whole-body and to hand-arm transmitted vibrations, as well as to evaluate the related risk levels. Vibration signals transmitted to the operator were acquired on the seat and the machine control lever in accordance with the procedures specified in ISO 2631-1 and ISO 5349-1. At the same time, noise signals were acquired at the operator’s ear following the procedure reported in ISO 11201. Vibration signals were also acquired on the cabin floor with the main purpose to evaluate the effectiveness of the machine seats in reducing the vibration transmission. Finally, the noise and vibration exposure risks were evaluated on the basis of the health and safety requirements established in 2003/10/EC and 2002/44/EC Directives.

6

Wpływ rodzaju podłoża oraz zmiany środka ciężkości użytkownika na komfort jazdy wózkiem inwalidzkim

Chwalik G., Kromka-Szydek M., Dziechciowski Z.

Aktualne Problemy Biomechaniki

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2017

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z. 12

15--20

PL

Celem pracy była ocena komfortu jazdy użytkownika uniwersalnego wózka inwalidzkiego. Dokonano oceny ryzyka związanego z krótkotrwałym działaniem drgań mechanicznych na osobę znajdującą się na wózku w zależności od rodzaju nawierzchni, po której się poruszała (badanie przeprowadzono na 13 różnych nawierzchniach). Przeanalizowano również wpływ zmiany środka ciężkości osoby na wózku, jaki ma miejsce przy zmianie postawy w trakcie jazdy czynnej i biernej.

EN

This study examined the effect of changes the centre of gravity and road surface types on using of a wheelchair. Users comfort, while using wheelchair, was specified during vibration measurement tests. The vibration was measured in each of three axes. For the purpose of this thesis the universal folding wheelchair Budget 9.050 of Meyra company was used. The measurements were performed on 13 different surfaces. Each test was executed twice for two different positions of wheelchair’s user. In the first test, user was sitting on a wheelchair and was pushed by the operator. In the second attempt, user was driving wheelchair by himself.

7

Contribution of individual components of a job cycle on overall severity of whole-body vibration exposure: a study in Indian mines

Mandal B. B., Mansfield N. J.

International Journal of Occupational Safety and Ergonomics

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2016

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Vol. 22, No. 1

142--151

EN

Drivers of earth-moving machines are exposed to whole-body vibration (WBV). In mining operations there can be a combination of relatively high magnitudes of vibration and long exposure times. Effective risk mitigation requires understanding of the main aspects of a task that pose a hazard to health. There are very few published studies of WBV exposure from India. This paper reports on a study that considered the contribution of the component phases of dumper operations, on the overall vibration exposure of the drivers. It shows that vibration magnitudes are relatively high, and that haulage tasks are the main contributor to the exposure. It is recommended that driver speed, haul road surfaces and vehicle maintenance/selection are optimized to ensure minimization of vibration. If this is not sufficient, operation times might need to be reduced in order to ensure that the health guidance caution zone from Standard No. ISO 2631-1:1997 is not exceeded.

8

Latest developments in international standardization of whole-body and hand-arm vibration

Liedtke M., Rissler J., Kaulbars U.

Archives of Acoustics

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2013

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Vol. 38, No. 4

555--558

EN

Latest developments in international standardization of whole-body and hand-arm vibration are pre- sented. In addition, two German projects are presented that might have impact on international work programs in the next years.

9

Research on Simultaneous Impact of Hand–Arm and Whole-Body Vibration

Kowalski P., Zając J.

International Journal of Occupational Safety and Ergonomics

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2012

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Vol. 18, No. 1

59--66

EN

This article presents the results of laboratory tests on the combined effect of whole-body vibration (WBV) and hand–arm vibration (HAV). The reactions of subjects exposed to various combinations of vibration were recorded. The vibrotactile perception threshold (VPT) test identified changes caused by exposure to vibration. Ten male subjects met the criteria of the study. There were 4 series of tests: a reference test and tests after exposure to HAV, WBV, and after simultaneous exposure to HAV and WBV. An analysis of the results (6000 ascending and descending VPTs) showed that the changes in VPTs were greatest after simultaneous exposure to both kinds of vibration. The increase in VPT, for all stimulus frequencies, was then higher than after exposure to HAV or WBV only.

10

A Design of Experiments for Statistically Predicting Risk of Adverse Health Effects on Drivers Exposed to Vertical Vibrations

Ayari H., Thomas M., Dore S.

International Journal of Occupational Safety and Ergonomics

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2011

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Vol. 17, No. 3

221--232

EN

An injury risk factor (IRF), which indicates the risk of adverse health effect to lumbar rachis arising from mechanical vibrations, is developed. Experiments have been conducted that consider acceleration levels at the seat of drivers, posture, morphology, density, damping rate and body mass as independent variables. A parametric finite-element model of the lumbar rachis has been generated. It is shown that the IRF increases with ageing and an IRF of 30% is proposed as a threshold for fatigue purposes. This level is reached if a peak acceleration level greater than 3 m/s2 is applied to a light (55 kg) and an old driver with a low bone density and a damping rate of 20%. This vibration threshold must be reduced to 2.7 m/s2 if the driverʼs weight increases to 75 kg and to 2 m/s2 if the driver is heavy (98 kg).

11

Occupational Exposure to Mechanical Vibration: The Italian Vibration Database for Risk Assessment

Nataletti P., Marchetti E., Lunghi A., Pinto I., Stacchini N., Santini F.

International Journal of Occupational Safety and Ergonomics

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2008

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Vol. 14, No. 4

379--386

EN

The Italian vibration database is presented. It is hosted by a web server at the National Institute of Occupational Prevention and Safety (ISPESL) in Rome, Italy (http://www.ispesl.it/vibrationdatabase). It supports in risk assessment employers who have to comply with Legislative Decree 187/05, now replaced by Legislative Decree 81/08, which transposes into law Vibration Directive 2002/44/EC. The database currently contains measurements and EC-declared values from over 980 hand-held power tools (such as pneumatic and electric hammers, chainsaws, grinders, drills, sanders and saws) and from over 420 vehicles (such as buses, forklifts and wheel tractors). The database is continuously updated as soon as new experimental and declared data are acquired.

12

Energetyczna transmitancja struktury biodynamicznej człowieka poddanego działaniu wibracji ogólnej

Dobry M. W., Grygorowicz M.

Diagnostyka

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2004

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Vol. 30, T. 1

147--150

PL

Badania przepływu energii w biodynamicznej strukturze ciała ludzkiego w pozycji siedzącej przy pobudzeniu do kinematycznych drgań siedziska umożliwiły zdefiniowanie i obliczenie wartości energetycznej transmitancji w funkcji częstotliwości pasma normowego oraz wartości transmitancji dla wszystkich punktów redukcji modelu dynamicznego badanej struktury. Transmitancja wykazała pasma częstotliwości i miejsca wzmocnienia oraz redukcji przepływu energii.

EN

Investigations of energy flow in biodynamical structure of the human body in sitting position during kinematical excitation of seat allows defining and calculating values of energy transmissibility as a function of the frequency standard band and points of reduction of the dynamical model of studied structure. Transmissibility has shown bands of frequencies and points of amplification and reduction of energy flow.

13

Transmitancja mocy struktury biodynamicznej człowieka poddanego działaniu wibracji ogólnej w pozycji siedzącej

Dobry M. W., Grygorowicz M.

Czasopismo Techniczne. Mechanika

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2004

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R. 101, z. 5-M

81--89

PL

W niniejszej pracy przestawiono rezultaty badań rozdziału mocy w biodynamicznej strukturze ciała człowieka w pozycji siedzącej. Badany rozdział mocy był wywołany kinematycznymi drganiami harmonicznymi siedziska operatora. W badaniach symulacyjnych dynamiki systemu biomechanicznego o 28 stopniach swobody zastosowano Pierwszą Zasadę Rozdziału Mocy w Systemie Mechanicznym. Rezultaty tych badań przedstawiono w postaci zdefiniowanej transmitancji mocy w funkcji częstotliwości i położenia punktów redukcji biodynamicznego modelu człowieka. Analiza wartości transmitancji mocy wykazała punkty redukcji o największym energetycznym obciążeniu (kręgi lędźwiowe: Kręg L2 i Kręg L1) oraz pasma częstotliwości wzmocnienia (od 1 do 3,16 Hz - maksymalne wzmocnienie dla 2,5 Hz) i redukcji przepływu energii (od 5 do 80 Hz) w zakresie częstotliwości normowych.

EN

Results of power distribution in biodynamical structure of human body in sitting position have been presented in the paper. The investigated power distribution has been caused by kinematical harmonic vibrations of a human-operator seat. The First Principle of Power Distribution in Mechanical System has been applied in simulation investigations of dynamics of the biomechanical system with 28 degrees of freedom. The results of the investigations of dynamics have been shown in form of defined transmissibility of power as a function of frequency and places of reduction points of the biodynamical model of a human. The analysis of values of the power transmissibility has shown the reduction points with the biggest energy load (lumbar vertebras: L2 and L1) an frequency bans of amplification (from 1 to 3,16 Hz - maximal for 2,5 Hz). Reduction of energy flow has been observed from 5 to 80 Hz of the standard frequency ban.