Study of the Human Body Vibrations for the Seated Vehicle Driver

The paper presents some aspects about the dynamic response of the human body subjected to the vertical vibration in the travel inside the auto vehicle. There is a model presented in the specialized literature. This is transformed for the given study because was necessary to realize the vertical vibration along the human body. There are two different studies: using a linear lumped parameter systems seat - human body model; using a nonlinear lumped parameter systems seat-human body model. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Responses Study of the Seated Human Body Exposed to Vertical Vibration in Various Automotive Postures

In a seated posture into an autovehicle, humans are most sensitive to whole-body vibrations under low-frequency excitation. This research is focused only on the effect of the backrest angle on the biodynamic response functions. In this paper there are present the results of investigations for 10 participants, whose mean body mass was 61.4 kg. For the biodynamic responses of a seated human body subjected to vertical vibrations, three automotive postures was study: without backrest support, with backrest inclined 7° and respectively 15°, by measurement of transmitted vibration in two different situations: with belt and respectively without this. Knowledge of human responses to vibration provides information about the position of backrest support to mitigate vibration transmitted through the body ensuring the health, comfort and performance. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Stability study of the human body-seat system into an autovehicle

The paper presents the study of the human body, as a mechanical system, seated inside an autovehicle and exposed under the vertical harmonic vibration action during the auto vehicle motion time. The human body may be roughly approximated by a linear lumped parameter at low frequencies and low vibration levels. Therefore, the model has 5 DOFs in translation, where 4 DOFs represents the human body and 1 DOF is for the seat cushion The mechanical model of the human body, in sitting position on the seat cushion of a vehicle seat, consists of four parts: pelvis, upper torso, viscera and head.. The eigenvalues for the human body – seat system and the damping ratio for the system was been calculate. The system stability analysis is given by the existence of a Lyapunov function for the system. The stability of a system can also be characterized by the eigenvalues of the system. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Vibration action on the human body into a tramway in traveling

This article presents the vibration action on the human body found in a tram travel, where made the vibration measurements. Also presented a mathematical model with two degrees of freedom. Finally a comparison was made between the results obtained from measurements and the results of integration. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the Cardiovascular Effects of Whole-Body Vibration Part II. Lateral Effects: Statistical Analysis

Lateral vibrations of vessels generate relative lateral motions between red blood cells and plasma. These relative motions would cause additional transport of longitudinal momentum between different layers and therefore would increase the viscosity. Particularly for arterioles, which play the major role for the total peripheral resistance (TPR), the lateral vibration would destroy the cell-free plasma layer near the wall if the local lateral amplitude of vibration were larger than 40 μm. Thus, if the local vibration gets stronger, one would expect TPR to increase if the vessels were not dilated. In order to test the possible dilations of vessels, a special design was made as follows. Three male subjects participated in this study. Each of them carried out a series of vibration tests on each of three vibrating devices. Accelerations at three locations on the body and various cardiovascular parameters were measured simultaneously. Each vibration test was divided into two or three parts with different body modes in a way that each change of body mode would increase the transmissibility and the local amplitudes. For the majority of changes of body mode, a decrease instead of an increase of TPR was observed. Statistical analysis ( ANOVA Within Within ) confirmed that the observed reduction of TPR during the changes of body mode was significant ( p = 0.0235). This gives indirect but clear evidences for the dilation of vessels, particularly the dilation of arterioles. Since the dilation of vessels, particularly of arterioles, is an important ability of human body to prevent the blood pressure from getting too high during strong exercises, competitions and heavy physical work, the present study suggests a potential benefit, among others, of vibration training to improve this ability.     

Vibrations Action of the Trilling Machine MA750 on the Human Operator Hand

The Work includes identifying and analyzing vibrations produced by a trilling machine MA750 within space work. To identify vibration is used a special method, which has not been used so far in identifying vibrations, with the action on the human body. For obtaining a very good identification of the human body vibrations has been used the Moiré projection method. General conditions were applied to human hand operator during working hours on a trilling machine, with different speeds of main shaft. In the paper are presented successively two methods of measuring the vibrations: the Moiré projection method and conventional method of measuring the vibrometer. The results in the booth situation (classical measurements and Moiré projection method) were in the same order of the unit scale, and the optical method named Moiré projection method can be considered a valid method for the human vibrations measurements without touch of the surface. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Development of a biomechanical model to study the horizontal vibration transmitted from shoulder to head

On daily activity a human operator is exposed to vibration in working environment. So, the human body will react in different way. The problem is how much from the initial signal will be sent to the other parts of the body and how much that motion will be damped along the studied parts. The vibrations in horizontal plane are some unexpected, so the human operator will not take any position to prevent them. In this condition the horizontal vibrations will have the higher effect possible. In this paper, the shoulder, neck and the head are modeled together like a mechanical system with four degree of freedom. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Research about moving restrictions of cervical spine under the action of mechanical vibrations

The cervical spine is very important human body part, because it sustains the head and it has a higher mobility than the other parts of human spine. The vibration could influence the work performance but also could have a negative influence on human body health. There are many elements, which could be damaged: eyes, ears, brain, mandible, neck's muscle, C1 to C7 vertebras. When the operator is exposed to vibrations for a long time, he can fill a strong pain at the neck. Injuries to the cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon. If it does occur, however, it may cause death or profound disability, including paralysis of the arms or legs. We purpose in this study to develop a biomechanical model for the cervical vertebras and identify the influence of mechanical vibrations on human cervical spine and human head. For this study is necessary to compute the entire moving system of the neck-head. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

弹性振动的闭环系统

细长体的飞行器在飞行中考虑了既有刚性运动又有弹性振动的运动,由于刚性运动对弹性振动的影响,通过安装在飞行器上面的仪表所测得的角速度作为反馈信号输入到控制器,由控制器输出端输出信号到执行机构来实现反馈控制,把刚性运动飞行器、弹性振动飞行器同时考虑作受控对象,这里我们研究了由刚性飞行器、弹性飞行器和控制器三者形成的闭环系统的弹性振动问题,得到了求闭环系统的频率和振型的公式,设计控制器使得闭环系统渐近稳定的条件和能控性、能观测性的条件。     

On the Cardiovascular Effects of Whole-Body Vibration Part I. Longitudinal Effects: Hydrodynamic Analysis

For a given direction of whole-body vibration and a given piece of blood vessel, the local vibration has in general both a longitudinal (parallel) component and a lateral (perpendicular) component. The longitudinal and lateral effects are treated in Part I and Part II, respectively. In Part I, detailed hydrodynamic analysis shows that the maximal shear stress at the wall of the vessel is considerably increased by the longitudinal component of vibration for big vessels. For example, for high frequency range 40–50 Hz, the maximal shear stress at the wall of coronary artery could increase by 35–49% even if the local longitudinal amplitude is as small as 50 μm. Potential benefits and risks associated with this effect are discussed. In Part II, statistical analysis is carried out based on the results of specially designed experiments, where accelerations at different body locations and some cardiovascular parameters were measured simultaneously. Some changes of body mode were arranged during the vibration experiments in a way that the transmissibility of vibration increased considerably during each change of body mode. Statistical analysis of the results suggests with high level of confidence (>97%) that arterioles were dilated during such changes of body mode. Potential benefits associated with this effect are discussed.     

Vibration by shocks of the human bodies in the working spaces

The paper contains the transmitted vibrations produce by shocks to the human bodies into the working space.There are the methods for measuring the vibration experiments transmitted through the shock of the human body by the foundation of forging hammer. There are the results given by the different sorts of accelerations into to special conditions of work in the working space. They are of the vibrometer adding the three directions accelerometer. In this way can be analyze taking into account the vibrations action over the human bodies under the action of the equipment in the working space produced by shocks. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

汽车车体振动系统的对称性与守恒量研究

用Lie群方法研究汽车车体振动系统的对称性,寻找其存在的守恒量.以汽车车体做上下垂直振动和绕其质心的前后俯仰振动,采用Lagrange函数的方法,构建汽车车体振动系统.以此系统为对象,引入Lie群方法,给出该振动系统的Noether对称性理论与Lie对称性理论;由此推导该汽车系统存在的Noether对称性与Lie对称性,并得到系统相应的的守恒量.该方法对车体振动问题提出了新的对称性解法,同时扩大了Lie群方法的应用范围.     

Research about transmission of the mechanical vibration done by machine-tools on the group of bones shoulder-neck-head

Different researches have shown that long–term exposure to whole–body vibration can induce different injuries like back pain, injuries of the different part of the body, disturbing the physical and intellectual activities. The resulted diseases could be occasional or could be for ever. Bearing in mind that vibration is applied on the hand or feet, the health rick can be assessed if the forces transmitted in the shoulder during vibration are known. To estimate the forces a biomechanical model has been developed in which the shoulder, neck and head are represented by rigid bodies. The bodies are connected by visco–elastic joint elements. The applied forces are resulted from experimental measurements. To assess the health risk the forces must be divised in two components, an ascendant one and a descendent one. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bi-nonlinear vibration model of tubing string in oil & gas well and its experimental verification

Fluid-induced vibration (FIV) prediction is an important prerequisite work in wear and fatigue analysis of tubing string in oil & gas well. The finite element method, energy method and Hamiltonian principle are comprehensively used to establish a single nonlinear vibration model of pipe conveying fluid, taking into account the longitudinal/lateral coupled vibration. Based on the contact/impact theory of elastic/plastic body, the nonlinear contact-impact model of tubing-casing is established and introduced into the single nonlinear vibration model to form a bi-nonlinear vibration model of tubing string in oil & gas well. The bi-nonlinear model is numerically discretized by the finite element method, solved by Newmark− β method, and verified preliminarily by a classical contact/impact example in literature in which the influence of inflow is not taken into account temporarily. A similar experiment of tubing vibration is designed and completed to further test the validity of the bi-nonlinear vibration model by comparing the frequency-domain and time-domain responses of the experiment with those from the model. The analysis shows that the bi-nonlinear model has good calculation accuracy and the vibration response law is basically consistent with the experimental results, which can provide an effective theoretical analysis tool for FIV behavior of tubing string in oil & gas well.     

Non-periodic and chaotic vibrations in a flow induced system

A flow induced system, consisting of an elastically mounted body with a pendulum attached, is considered here. The stability of the semi-trivial solution, representing the vibration of the body with the non-oscillating pendulum, is investigated. The analytical investigation shows that at a certain flow velocity, higher than the critical one, the pendulum begins to oscillate due to autoparametric resonance. For a convenient tuning, the vibration of the system can be substantially reduced. The analysis of both semi-trivial and non-trivial solutions is complemented by numerical integration of the differential equations of motion. A mapping technique based on Poincaré section, suitable for investigating the non-periodic vibrations occuring at higher flow velocities, is proposed.     

Generation of surface waves through friction: FEM investigation

Sliding friction between two bodies can generate elastic vibration. This study uses a finite-element model comprising an elastic body sliding against a flat rigid surface with constant coefficient of friction. For the elastic body a structured topography is taken into account. The model shows traveling surface waves, which depend on the asperities of the sliding surface. It can be shown that the surface structure and its inertia are the cause for elastic waves in the contact region. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Transfer matrix method for the free and forced vibration analyses of multi-step Timoshenko beams coupled with rigid bodies on springs

Multi-step Timoshenko beams coupled with rigid bodies on springs can be regarded as a generalized model to investigate the dynamic characteristics of many structures and mechanical systems in engineering. This paper presents a novel transfer matrix method for the free and forced vibration analyses of the hybrid system. It is modeled as a chain system, where each beam and each rigid body with its supporting spring are dealt with one element, respectively. The transfer equation of each element is deduced based on separation of variables method. The system overall transfer equation is obtained by substituting an element transfer equation into another. Then, the free vibration characteristics are acquired by solving exact homogeneous linear equations. To compute the forced vibration response with modal superposition method, the body dynamic equations and augmented eigenvectors are established, and the orthogonality of augmented eigenvectors is mathematically proved. Without high-order global dynamic equation or approximate spatial discretization, the free and forced vibration analyses of the hybrid system are achieved efficiently and accurately in this study. As an analytical approach, the present method is easy, highly stylized, robust, powerful and general for the complex hybrid systems containing any number of Timoshenko beams and rigid bodies. Four numerical examples are implemented, and the results show that this method is computationally efficient with high precision.     

On stability of motion of a symmetric body placed on a vibrating base

We consider the problem of stabilization of a symmetric solid body rotating about a fixed point and show that its unstable states can be stabilized by vertical vibration.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 47, No. 12, pp. 1661–1666, December, 1995.     

A finite-element mechanical contact model based on Mindlin-Reissner shell theory for a three-dimensional human body and garment

Efficient numerical methods for describing a garment’s mechanical behavior during wear have been identified as the key technology for garment simulation. This paper presents a finite-element mechanical contact model based on Mindlin-Reissner shell theory for a three-dimensional human body and garment. In this model, the human body and the garment are meshed as basic contact cells, these contact cells between the human body and the garment are defined as the contact pair to describe the contact relationship, and the mathematical formulation of the finite-element model is defined to describe the strain-stress performance of the three-dimensional human body and garment system. By using the solution given by the computer code and the programs specifically developed, the calculations of the mechanics in the basic cells of the human body and the garment have been able to be carried out. The simulation results show that the model of rationality, a good simulation results and simulation efficiency.     

A Modal Analysis of Resonance during the Whole-Body Vibration

The mechanism of resonance of a damping system of multi‐degrees of freedom such as the human body and the dependence of resonance on system parameters, particularly on the damping level, are studied in terms of detailed mathematical solutions of both the whole‐body vibrations and the eigen modes for a simple model. It is revealed that resonance would only occur near the eigen frequencies of neutral modes for which the complex eigen frequencies of the corresponding damping modes for the given damping level of the system have not moved far from the starting point (damping‐free case) along the corresponding tracks in the plane of complex eigen frequency yet. The major resonance would occur near the eigen frequency of the neutral mode where the modulus of the characteristic function of the system has the strongest, i.e., the deepest and sharpest, local minimum. For the present model, this neutral mode is the lowest neutral mode. It is found that the resonance and eigen frequencies increase with the stiffness of muscles and decrease with the body mass, with the portion of wobbling mass in the upper body, and with the portion of upper body mass in the whole body. Both the modal analysis and the analysis of the whole‐body vibration show that the phase differences among different parts of the system are still small at the unique or the lowest resonance frequency and increase dramatically only when the frequency of the vibrating source goes beyond the resonance frequency. Thus, some effects of body vibrations, e.g., internal loads, may reach their maximum not at the resonance frequency, but at a frequency somewhat higher than the resonance frequency. This may account for the fact that the frequency ranges for abdominal pain and for lumbosacral pain caused by body vibrations are not exactly the same as the frequency range for major body resonance but shifted to somewhat higher frequency ranges. It is therefore suggested that the frequency used for strength training in terms of vibrating devices should be above 20 Hz in order to avoid not only the major resonance but also the maximal internal loads.