Threaded Components Under Axial Harmonic Vibration, Part 1: Experiments

1996 ◽  
Vol 118 (3) ◽  
pp. 417-422 ◽  
Author(s):  
D. P. Hess ◽  
K. Davis
Keyword(s):  
Kinematic Model ◽  
Harmonic Vibration ◽  
Static Equilibrium ◽  
Physical Parameters ◽  
Design Element ◽  
Equilibrium Conditions ◽  
Critical Design ◽  
Threaded Fasteners ◽  
Series Of Experiments ◽  
Theoretical Analyses

Threaded components have found ubiquitous use in many systems and structures. Although frequently overlooked, they represent a complex and often critical design element. One can identify numerous instances where such elements are subjected to vibratory conditions, yet their behavior in such an environment is still poorly understood. In this paper, we report on a series of experiments that were run to examine the motions of threaded fasteners subjected to axial harmonic vibration. The components are loaded by gravity and excited over a broad range of conditions. It is found that significant relative twisting motion can occur both with and against the load. This indicates that threaded components may loosen or tighten in the presence of vibration. It is shown that the direction of twist depends on the frequency and amplitude of the vibratory input as well as various physical parameters. Previous theoretical analyses of threaded components under vibration are based on static equilibrium conditions, and only predict a loosening action, i.e., twist with load. In Part 2 of this paper, a kinematic model is developed which predicts twisting both with and against load as observed in the experiments.

Vibration-Induced Loosening and Tightening of Threaded Fasteners

1995 ◽  
Author(s):  
Daniel P. Hess
Keyword(s):  
Dynamic Model ◽  
Nonlinear Interaction ◽  
Low Frequency ◽  
Harmonic Vibration ◽  
Static Equilibrium ◽  
Equilibrium Conditions ◽  
System Parameters ◽  
Threaded Fasteners

Abstract Previous analyses of threaded fasteners under vibration are based on static equilibrium conditions with supporting data limited to low frequency loading. Such analyses predict only a net loosening action. This paper presents a dynamic model of a single-bolt assembly with moderate pre-load subjected to axial harmonic vibration. Simulations with this model predict that threaded fasteners can, on the average, loosen or tighten in the presence of vibration; and that the applied vibration, as well as other system parameters, can be tuned so that either action occurs. The model elucidates the nonlinear interaction of friction and vibration of such systems. Measurements from a single-bolt assembly apparatus are presented and compared with the simulations.

Dynamic Loosening and Tightening of a Single-Bolt Assembly

1997 ◽  
Vol 119 (3) ◽  
pp. 311-316 ◽  
Author(s):  
D. P. Hess ◽  
S. V. Sudhirkashyap
Keyword(s):  
Dynamic Model ◽  
Low Frequency ◽  
Harmonic Vibration ◽  
Static Equilibrium ◽  
Equilibrium Conditions ◽  
System Parameters ◽  
Threaded Fasteners

Previous analyses of threaded fasteners under vibration are based on static equilibrium conditions with supporting data limited to low frequency loading. Such analyses predict only a net loosening action. This paper presents a dynamic model of a single-bolt assembly with moderate pre-load subjected to axial harmonic vibration. Simulations with this model predict that threaded fasteners can, on the average, loosen or tighten in the presence of vibration; and that the applied vibration, as well as other system parameters, can be tuned so that either action occurs. Measurements from a single-bolt assembly apparatus are presented and compared with the simulations.

Experimental and Theoretical Investigation of Inorganic Scale Deposition in Carbonated Micromodels

2009 ◽  
Author(s):  
Negar Mosavati ◽  
Riyaz Kharrat ◽  
Seyed Amir Farzaneh ◽  
Mohammad Hossein Ghazanfari
Keyword(s):  
Flow Rate ◽  
Barium Sulphate ◽  
Physical Parameters ◽  
Equilibrium Conditions ◽  
Gradual Process ◽  
Glass Micromodel ◽  
Series Of Experiments ◽  
Brine Concentration ◽  
Scale Deposition ◽  
Observation Results

In this study, a series of experiments have been conducted on glass micromodel to investigate the effect of different parameters on the gradual process of Barium Sulphate precipitation. Due to the visual nature of the glass micromodel, the shape, size and distribution of scaling formation in a carbonate-rock-look-alike pattern with water-wet characteristics is precisely observable. In addition, an exponential functionality (correlation) was proposed which incorporates all physical parameters affecting the behavior of the system in a dimensionless form. Reynolds number and deviation from equilibrium conditions are the backbones of this correlation. The adjustable exponents of the equation were determined by using a suitable optimization algorithm. This meaningful correlation can also predict the core extracted data with reasonable accuracy. The microscopy observation results confirmed that the deposition is initiated and extended in the middle space of pores and throats. In addition, by increasing the temperature and brine concentration as well as by decreasing the flow rate, the size of crystals was grown. Moreover, the experimental results indicated that by increasing the temperature and brine concentration as well as by decreasing the flow rate, the scaling tendency was increased.

scholarly journals Kinetostatic analysis and solution classification of a class of planar tensegrity mechanisms

Robotica ◽  
2018 ◽  
Vol 37 (7) ◽  
pp. 1214-1224 ◽  
Author(s):  
P. Wenger ◽  
D. Chablat
Keyword(s):  
Static Equilibrium ◽  
Equilibrium Conditions ◽  
Geometric Conditions ◽  
Equilibrium Configurations ◽  
Groebner Base ◽  
Systematic Solution ◽  
Alternative Designs ◽  
Interesting Alternative ◽  
Solution Classification

SUMMARYTensegrity mechanisms are composed of rigid and tensile parts that are in equilibrium. They are interesting alternative designs for some applications, such as modeling musculo-skeleton systems. Tensegrity mechanisms are more difficult to analyze than classical mechanisms as the static equilibrium conditions that must be satisfied generally result in complex equations. A class of planar one-degree-of-freedom tensegrity mechanisms with three linear springs is analyzed in detail for the sake of systematic solution classifications. The kinetostatic equations are derived and solved under several loading and geometric conditions. It is shown that these mechanisms exhibit up to six equilibrium configurations, of which one or two are stable, depending on the geometric and loading conditions. Discriminant varieties and cylindrical algebraic decomposition combined with Groebner base elimination are used to classify solutions as a function of the geometric, loading, and actuator input parameters.

Obstacle negotiation analysis of track-legged robot based on terramechanics

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Zhu Hongbiao ◽  
Yueming Liu ◽  
Weidong Wang ◽  
Zhijiang Du
Keyword(s):  
Kinematic Model ◽  
Interaction Model ◽  
Experimental Results ◽  
Physical Parameters ◽  
Negotiation Analysis ◽  
Content Type ◽  
Practical Applications ◽  
Loose Soil ◽  
Key Steps ◽  
Drawbar Pull

Purpose This paper aims to present a new method to analyze the robot’s obstacle negotiation based on the terramechanics, where the terrain physical parameters, the sinkage and the slippage of the robot are taken into account, to enhance the robot’s trafficability. Design/methodology/approach In this paper, terramechanics is used in motion planning for all-terrain obstacle negotiation. First, wheel/track-terrain interaction models are established and used to analyze traction performances in different locomotion modes of the reconfigurable robot. Next, several key steps of obstacle-climbing are reanalyzed and the sinkage, the slippage and the drawbar pull are obtained by the models in these steps. In addition, an obstacle negotiation analysis method on loose soil is proposed. Finally, experiments in different locomotion modes are conducted and the results demonstrate that the model is more suitable for practical applications than the center of gravity (CoG) kinematic model. Findings Using the traction performance experimental platform, the relationships between the drawbar pull and the slippage in different locomotion modes are obtained, and then the traction performances are obtained. The experimental results show that the relationships obtained by the models are in good agreement with the measured. The obstacle-climbing experiments are carried out to confirm the availability of the method, and the experimental results demonstrate that the model is more suitable for practical applications than the CoG kinematic model. Originality/value Comparing with the results without considering Terramechanics, obstacle-negotiation analysis based on the proposed track-terrain interaction model considering Terramechanics is much more accurate than without considering Terramechanics.

scholarly journals Extraction of the deterministic ingredient of a dynamic geodetic control network

2012 ◽  
Vol 2 (1) ◽  
pp. 68-75 ◽  
Author(s):  
L. Shahar ◽  
G. Even-Tzur
Keyword(s):  
Kinematic Model ◽  
Simultaneous Estimation ◽  
Physical Parameters ◽  
Control Network ◽  
Deformation Parameters ◽  
Free Network ◽  
Geodetic Control ◽  
Definition Of ◽  
Minimum Constraints ◽  
Entire Network

Extraction of the deterministic ingredient of a dynamic geodetic control networkA minimum constraints solution, which resolves the datum defect of a control network, is an arbitrary solution that may result in a systematic error in the estimation of the deformation parameters. This error is not derived from measurements and is usually inconsistent with the geophysical reality. A free network is affected only by errors of measurement and, therefore, a free network is an accepted way of coping with this problem. Study of deformations, which is based on the use of geodetic measurements, is usually performed today by defining a kinematic model. Such a model, when used to describe a complex geophysical environment, can lead to the partial estimation of the deterministic dynamics, which characterize the entire network. These dynamics are themselves expressed in measurements, as the adjustment systems' residuals. The current paper presents an extension of the definition of the parameters that are revalued. This extension enables the cleaning of measurements by means of the extraction of datum elements that have been defined by geodetic measurement. This cleaning minimizes the effects of these elements on the revaluated deformation. The proposed algorithm may be applied to achieve the simultaneous estimation of the physical parameters that define the geophysical activity in the network.

scholarly journals Determination of the Strain-Free Configuration of Multispan Cable

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Chuancai Zhang ◽  
Qiang Guo ◽  
Xinhua Zhang
Keyword(s):  
Finite Element ◽  
Geometric Model ◽  
Static Equilibrium ◽  
Equilibrium Conditions ◽  
Constraint Equations ◽  
Asymptotic Shape ◽  
Geometric Conditions ◽  
End Conditions

For building a reasonable finite element geometric model, a method is proposed to determine the strain-free configuration of the multispan cable. The geometric conditions (the end conditions and the unstretched length conditions) as constraints for the configuration of multispan cable are given. Additionally, asymptotic static equilibrium conditions are given for determining the asymptotic shape of the multispan cable. By solving these constraint equations, a set of parameters are determined and then the strain-free configuration of multispan cable is determined. The method reported in this paper provides a technique for building reasonable FEA geometric model of multispan cables. Finally, a three-span cable is taken as example to illustrate the effectiveness of the method, and the computed results are validated via the software ADINA.

scholarly journals Parity: A key measure of confounding in data-linkage studies of outcomes after medically assisted reproduction

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Georgina M Chambers ◽  
Christos A Venetis ◽  
Louisa R Jorm ◽  
Claire M Vajdic
Keyword(s):  
Assisted Reproduction ◽  
Data Linkage ◽  
Population Based ◽  
Linkage Study ◽  
Design Element ◽  
Medically Assisted Reproduction ◽  
Critical Design ◽  
First Child ◽  
Hormone Sensitive ◽  
Universal Health

Parity is a potential confounder of the association between medically assisted reproduction (MAR) and health outcomes. This concept paper describes a population-based record linkage study design for selecting MAR-unexposed women matched to the parity of MAR-exposed women, at the time of the first exposure to MAR. Women exposed to MAR were identified from claims for government subsidies for relevant procedures and prescription medicines, linked to perinatal records. Women unexposed to MAR were identified from linked perinatal and death records, matched to exposed women by age, rurality, age of first child (if any) and parity at the date of first MAR. The availability of a longitudinal, whole-of-population dataset (“population spine”) based on enrolments in Australia’s universal health insurance scheme was a critical design element. The example application examines cancer risk in women after exposure to MAR. Parity is a confounder in this setting because it is associated with MAR and hormone-sensitive cancers.

scholarly journals Electron Trapping and Precipitation in Asymmetric Solar Flare Loops

2000 ◽  
Vol 195 ◽  
pp. 375-376
Author(s):  
M. J. Aschwanden ◽  
L. Fletcher ◽  
T. Sakao ◽  
T. Kosugi ◽  
H. Hudson
Keyword(s):  
Solar Flares ◽  
Pitch Angle ◽  
Kinematic Model ◽  
Physical Parameters ◽  
Loss Cone ◽  
X Ray ◽  
Flare Loops ◽  
Gyrosynchrotron Emission ◽  
Flight Delay ◽  
Energy Dependent

Acceleration, propagation, and energy loss of particles energized in solar flares cannot be studied separately because their radiative signatures observed in the form of hard X-ray bremsstrahlung or radio gyrosynchrotron emission represent a convolution of all these processes. We analyze hard X-ray emission from solar flares using a kinematic model that includes free-streaming electrons (having an energy-dependent time-of-flight delay) as well as temporarily trapped electrons (which are pitch-angle scattered by Coulomb collisional scattering) to determine various physical parameters (trapping times, flux asymmetry, loss-cone angles, magnetic mirror ratios) in flare loops with asymmetric magnetic fields.

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