Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Powiadomienia systemowe

Sesja wygasła!

Znaleziono wyników: 3

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Dynamic characteristics of a compliant seat coupled with the human body and a manikin during the exposure to the whole-body vibration: effect of the polyurethane foam, the track position and the measurement location

Zhang Xiaolu, Lin Sen, Song Xichen, Liu Chi, Qiu Yi

Acta of Bioengineering and Biomechanics

2024

Vol. 26, no. 2

106--114

Transmissibility is used to assess dynamic responses of the occupant-seat system, and most studies have exclusively assessed the transmissibility from the floor to the cushion or the backrest surface with the human body. In this investigation, the vertical vibration transmitted from the floor to six specific locations both on the seat surface and the frame when the seat was fixed on three positions on the track was examined utilizing an SAE J826 manikin and 12 male adults (0.25 to 20 Hz) for a duration of 120 seconds at three vibration amplitudes. The transmissibility from the floor to the headrest frame, the cushion surface, the headrest surface, the seat back frame, and the seat back surface all exhibited a principal peak frequency within 4–5 Hz. With the exception of the cushion frame, the principal peak frequency and the peak transmissibility in transmissibilities to all positions decreased with increasing vibration amplitude, indicating the non-linearity within the occupant-seat system. It was also found modifying seat track positions minimally affected the seat transmissibility to either the surface or the frame of the seat. Polyurethane foam amplified vibration at peak frequency, simultaneously enhancing static sitting comfort and reducing the vertical vibration transmission above peak frequency.

Effects of a water hammer and cavitation on vibration transients in a reservoir-pipe-valve system

Miao Yang, Qiu Zaihui, Zhang Xiaolu, Jiang Yuncheng, Pan Jun, Liu Yi, Zhang Li, Li Kun

Journal of Theoretical and Applied Mechanics

2021

Vol. 59 nr 4

611--622

An extraordinary phenomenon with violent oscillation, accompanied by an abnormal “click” sound is observed during the valve closing in a fuel feeding pipe system. A fluctuation model with flow cavitation, in which time-varying stiffness, time-varying damping coefficients and flow cavitation are comprehensively considered, is proposed. On this basis, a dynamic vibration equation is established and an expression of flow pressure at the valve port is derived. The critical displacement of the flow cavitation system is defined. When the vibration amplitude reaches the critical displacement, cavitation occurs. Based on this model, simulation of vibration displacement and flow pressure is given. The simulated transient process shows the phenomena of vibration fluctuation with cavitation. The results are compared with the experimental data measured by a pressure sensor. Under our experimental conditions, the critical displacement of vibration is 1.41mm, and the average relative pressure peak error is 0.022. The comparison between the simulation and experimental results shows that they are in an acceptable agreement.

Vibration transients of reservoir-pipe-valve system caused by water hammer

Miao Yang, Jiang Yuncheng, Qiu Zaihui, Pan Jun, Wang Lu, Han Zhenrong, Li Kun, Zhang Li, Zhang Xiaolu

Journal of Theoretical and Applied Mechanics

2020

Vol. 58 nr 4

1037--1048

A severe oscillation, accompanied with an abnormal “click” sound, of a fuel feeding pipe system during valve closing, when the feeding flowrate reaches a certain value, is observed experimentally. A fluctuation model in which stiffness and damping coefficients of the vibration system are time varying is proposed. Each coefficient is composed of two parts, one of which is constant and the other is time varying. Based on this model, simulation transients of the vibration displacement, velocity and pressure in the pipe are presented. Simulations of the pressure transients are compared with experimental data detected by pressure transducer, which shows that both have fluctuations in the transient process at a large flowrate.