Effect of Key Variable Combinations on the Vibration-Induced Loosening of Preloaded Fasteners

2016 ◽  
Author(s):  
Joon Ha Lee ◽  
Khalid Mahmood ◽  
Sayed A. Nassar
Keyword(s):  
Mathematical Model ◽  
Joint Stiffness ◽  
Initial Tension ◽  
Friction Coefficients ◽  
Relative Significance ◽  
Transverse Vibrations ◽  
Thread Pitch ◽  
Pitch Bearing ◽  
Bolt Loosening

This study investigates the effect of key variable combinations on the loosening performance of a preloaded threaded fastener system under harmonic transverse vibrations, using a software for bolt loosening analysis. The software is based on a mathematical model of the standard Junker test for vibration loosening. Studied variable combinations include the fastener initial tension, thread pitch, bearing and thread friction coefficients, bolt stiffness, and joint stiffness. Generated data on bolt loosening performance is analyzed for trends and relative significance of variables, and variable combinations.

Effect of Thread Pitch and Initial Tension on the Self-Loosening of Threaded Fasteners

2005 ◽  
Vol 128 (4) ◽  
pp. 590-598 ◽  
Author(s):  
Sayed A. Nassar ◽  
Basil A. Housari
Keyword(s):  
Mathematical Model ◽  
Angular Motion ◽  
The Self ◽  
Initial Tension ◽  
Transverse Loads ◽  
Threaded Fasteners ◽  
Thread Pitch ◽  
Transverse Excitation ◽  
System Properties ◽  
Number Of Cycles

A mathematical model and an experimental procedure are presented to study the self-loosening phenomenon of threaded fasteners that are subjected to cyclic transverse loads. The study investigates the effect of thread pitch, initial bolt tension, and the amplitude of the external excitation on the loosening of a single-bolt joint. The rate of drop in the joint clamp load (fastener tension) per cycle, as well as the total number of cycles that would cause the complete loss of clamp load, are monitored. In the mathematical model, the differential equations of linear and angular motion of the bolt are formulated in terms of the system properties and the external cyclic transverse excitation. Numerical integration of the equation of angular motion provides the bolt rotation in the loosening direction, which causes the partial or full loss of the clamp load. An iterative MATLAB code is developed and used for the calculation of tension loss in the fastener tension due to the self-loosening. Analytical and experimental results are discussed.

Effect of Conical Angle and Thread Pitch on the Self-Loosening Performance of Preloaded Countersunk-Head Bolts

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Amro M. Zaki ◽  
Sayed A. Nassar ◽  
Xianjie Yang
Keyword(s):  
Mathematical Model ◽  
Model Prediction ◽  
The Self ◽  
Nonlinear Mathematical Model ◽  
Transverse Loading ◽  
Load Model ◽  
Conical Angle ◽  
Thread Pitch ◽  
Gradual Loss

This paper investigates the effect of the countersunk conical angle and thread pitch on the loosening performance of preloaded countersunk-head bolts that are subjected to harmonic transverse loading. A nonlinear mathematical model is used to predict the loosening performance. Cumulative differential loosening rotation of the bolt head is converted to a gradual loss in the bolt tension and joint clamp load. Model prediction of the self-loosening behavior is experimentally validated.

Effect of Thread and Bearing Friction Coefficients on the Vibration-Induced Loosening of Threaded Fasteners

2007 ◽  
Vol 129 (4) ◽  
pp. 484-494 ◽  
Author(s):  
Basil A. Housari ◽  
Sayed A. Nassar
Keyword(s):  
Mathematical Model ◽  
The Self ◽  
Time Data ◽  
Friction Coefficients ◽  
Rotational Angle ◽  
Transverse Loads ◽  
Threaded Fasteners ◽  
Solid Film ◽  
Loosening Rate ◽  
Bearing Friction

This study provides a theoretical and experimental investigation of the effect of the thread and bearing friction coefficients on the self-loosening of threaded fasteners that are subjected to cyclic transverse loads. The friction coefficients are varied by using different types of coating and lubrication. A phosphate and oil coating and an olefin and molydisulfide solid film lubricant are used on the bolts tested. A mathematical model is developed to evaluate the self-loosening behavior in threaded fasteners when subjected to cyclic transverse loads. An experimental procedure and test setup are proposed in order to collect real-time data on the loosening rate (rate of clamp load loss per cycle) as well as the rotational angle of the bolt head during its gradual loosening. The experimental values of the friction coefficients are used in the mathematical model to monitor their effect on the theoretical results for the loosening rate. Experimentally, the friction coefficients are modified by changing the coating or the lubrication applied to the fasteners. The theoretical and experimental results are presented and discussed.

scholarly journals The calibration of an avalanche mathematical model using field data

2002 ◽  
Vol 2 (3/4) ◽  
pp. 217-220 ◽  
Author(s):  
V. Blagovechshenskiy ◽  
M. Eglit ◽  
M. Naaim
Keyword(s):  
Mathematical Model ◽  
Field Data ◽  
Travel Distance ◽  
Empirical Equations ◽  
Velocity Data ◽  
Friction Coefficients ◽  
Using Data

Abstract. The experience of calibrating Eglit’s avalanche model using data about the avalanche travel distance lengths and velocity data from the Zailiyskiy Alatau range (Kazakhstan) is discussed. Empirical equations are proposed that describe the dependence of the friction coefficients on the avalanche volume and type.

Modeling of conditions for formation of melted metal bath and weld during facing with consumable electrode and additional fi ller wire

2020 ◽  
pp. 247-255
Author(s):  
S.S. Poloskov ◽  
V.A. Erofeev ◽  
M.A. Sholokhov
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Mathematical Model ◽  
Computer Simulation ◽  
Boundary Conditions ◽  
Consumable Electrode ◽  
Metal Bath ◽  
Transverse Vibrations ◽  
Pressure Equilibrium ◽  
Melted Metal

The capabilities of computer simulation of complex multifactorial surfacing processes are discussed. Physical and mathematical model for the formation of melted metal bath and weld during consumable electrode surfacing with additional fi ller wire of parts and components of pipeline valves is presented. The basis of the model is equations system of heat transfer and pressure equilibrium on the surface of the melt. In the boundary conditions of the equations, change in the geometry of the surface due to transverse vibrations of the surfacing torch is taken into consideration. Numerical solution of the equations system showed that the main source of heat is heat from the droplets of the electrode and fi ller materials, its distribution is mainly determined by the amplitude and period of transverse vibrations. The results of process numerical simulation are presented. The results of the study are used in the development of innovative technological processes for surfacing of parts and components of pipeline valves.

Transverse Vibrations of a Cylinder Very Close to a Plane Wall

1987 ◽  
Vol 109 (1) ◽  
pp. 52-60 ◽  
Author(s):  
J. Fredso̸e ◽  
B. M. Sumer ◽  
J. Andersen ◽  
E. A. Hansen
Keyword(s):  
Mathematical Model ◽  
Lift Force ◽  
Important Influence ◽  
Plane Wall ◽  
Spring Stiffness ◽  
Transverse Vibrations ◽  
Steady Current ◽  
Series Of Experiments

The paper presents a series of experiments carried out with a cylinder suspended by springs and placed very close to a plane wall. The cylinder is exposed to a steady current. The range of gap ratios between zero and one has been studied in detail. Different combinations of spring stiffness and mass of cylinder is applied in the range of reduced velocity between 2 and 10. The proximity of the wall is shown to have important influence on the behavior of the pipe. Some of these trends are explained by a mathematical model including the effect of lift force close to the wall.

scholarly journals Mathematical Model of the Transmission Dynamics of Novel Corona Virus (COVID-19) Pandamic Disease with Optimal Control

2021 ◽  
Vol 15 ◽  
pp. 195-214
Author(s):  
Getachew Beyecha Batu ◽  
Eshetu Dadi Gurmu
Keyword(s):  
Mathematical Model ◽  
Reproduction Number ◽  
Equilibrium Points ◽  
Endemic Equilibrium ◽  
Transmission Dynamics ◽  
Relative Significance ◽  
Corona Virus ◽  
Next Generation Matrix ◽  
The Stability ◽  
Disease Free

In this paper, we have developed a deterministic mathematical model that discribe the transmission dynamics of novel corona virus with prevention control. The disease free and endemic equilibrium point of the model were calculated and its stability analysis were prformed. The reproduction number R0 of the model which determine the persistence of the disease or not was calculated by using next generation matrix and also used to determine the stability of the disease free and endemic equilibrium points which exists conditionally. Furthermore, sensitivity analysis of the model was performed on the parameters in the equation of reproduction to determine their relative significance on the transmission dynamics of COVID- 19 pandemic disease. Finally the simulations were carried out using MATLAB R2015b with ode45 solver. The simulation results illustrated that applying prevention control can successfully reduces the transmission dynamic of COVID-19 infectious disease.

Research on Self-Loosening Mechanism of Bolted Joints Under Transversal Vibration

2014 ◽  
Author(s):  
Wei Wang ◽  
Qingli Wang ◽  
Shuai Zheng ◽  
Xiaowei Liu ◽  
Haiping Liu
Keyword(s):  
Friction Coefficient ◽  
Three Dimensional ◽  
Surface Friction ◽  
The Self ◽  
Bolted Joints ◽  
Friction Coefficients ◽  
Cyclic Shear ◽  
Transversal Vibration ◽  
Thread Pitch ◽  
Bearing Friction

Bolted joints are widely used in the auto industry, energy field and Construction, and so on. Due to the wide use of the bolted joints, the degradation of bolts has significant effect on the performance of a whole machine. Under transversal vibration, the self-loosening of bolted joints, which is the biggest form of failure ranked only second to fatigue failure [1], will happen, due to the cyclic shear load. This paper is to study the mechanism of bolted joints’ self-loosening. Aiming at analyzing the self-loosening mechanism of bolted joints under vibration, a three dimensional FEA model of bolted joints, which had taken thread into consideration, was built with the application of APDL, and the preload was applied on the bolted joints by dropping temperature, then FEA transient analysis of the bolted joints under transverse cyclic excitation was conducted. Effect of transverse cyclic excitation’s amplitude, initial preload, thread and bearing friction coefficients, the joints’ surface friction coefficient, the thread pitch and the hole clearance on self-loosening was investigated. The results show that the complete thread slip occurs prior to the complete bearing surface slip under transverse vibration; the smaller amplitude, the smaller thread pitch and the smaller hole clearance is, and the greater initial preload, thread and bearing friction coefficients are, the more difficult self-loosening is to happen; the joints’ surface friction coefficient has little relationship with self-loosening, however, the larger joints’ surface friction coefficient makes the needed shearing force, which induces the transversal vibration, larger. These are of great significance for understanding of fasteners’ self-loosening and designing of bolted joints’ anti-loosening.

Transverse Oscillations of a Vertical Pile in Waves

1982 ◽  
Vol 104 (1) ◽  
pp. 46-52 ◽  
Author(s):  
F. Angrilli ◽  
V. Cossalter
Keyword(s):  
Mathematical Model ◽  
Natural Frequency ◽  
Transverse Direction ◽  
Wave Action ◽  
Simple Mathematical Model ◽  
Transverse Vibrations ◽  
Lock In Effect ◽  
Lock In ◽  
Transverse Oscillations

A cantilevered pile, flexible only in the transverse direction, has been submitted to wave action. It has been found that resonance transverse vibrations, with natural frequency fn, are induced by eddies shedding in waves having frequency fw = 1, 1/2, 1/3, 1/4 fn. A lock-in effect has been observed within the range of 0.9 fn ≤ fw ≤ 1.1 fn. Results of a simple mathematical model find reasonable support in the experiments.

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