Vibration-Induced Loosening Performance of Preloaded Threaded Fasteners

2010 ◽  
Author(s):  
Xianjie Yang ◽  
Sayed Nassar
Keyword(s):  
Nonlinear Model ◽  
Excitation Amplitude ◽  
The Self ◽  
Transverse Displacement ◽  
Transverse Loading ◽  
Threaded Fasteners ◽  
Bolt Preload ◽  
Proposed Model ◽  
Number Of Cycles ◽  
Insight Into

In an effort to establish a theoretical outline of a criterion for preventing the vibration-induced loosening of preloaded threaded fasteners, this paper provides an experimental and analytical insight into the effect of the initial bolt preload and the excitation amplitude on the self loosening performance of cap screw fastener. A nonlinear model is used for predicting the clamp load loss caused by the vibration-induced loosening of cap screw fasteners under cyclic transverse loading. Experimental verification was conducted on the twisting torque variation and the effect of the preload level and transverse displacement amplitude. Comparison of the experimental and analytical results on the clamp load loss with the number of cycles verifies that the proposed model accurately predicts self-loosening performance.

Analytical and Experimental Investigation of Self-Loosening of Preloaded Cap Screw Fasteners

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Xianjie Yang ◽  
Sayed Nassar
Keyword(s):  
Experimental Investigation ◽  
Excitation Amplitude ◽  
The Self ◽  
Transverse Displacement ◽  
Transverse Loading ◽  
Threaded Fasteners ◽  
Bolt Preload ◽  
Proposed Model ◽  
Number Of Cycles ◽  
Insight Into

In an effort to establish a theoretical outline of a criterion for preventing the vibration-induced loosening of preloaded threaded fasteners, this paper provides an experimental and analytical insight into the effect of the initial bolt preload and the excitation amplitude on the self-loosening performance of a cap screw fastener. A nonlinear model is used for predicting the clamp load loss caused by the vibration-induced loosening of cap screw fasteners under cyclic transverse loading. Experimental verification was conducted on the twisting torque variation and the effect of the preload level and transverse displacement amplitude. Comparison of the experimental and analytical results on the clamp load loss with the number of cycles verifies that the proposed model accurately predicts self-loosening performance.

Criterion for Preventing Self-Loosening of Preloaded Countersunk Head Threaded Fasteners

2011 ◽  
Author(s):  
Amro M. Zaki ◽  
Sayed A. Nassar ◽  
Xianjie Yang
Keyword(s):  
Test Procedure ◽  
Analytical Formula ◽  
Threshold Value ◽  
Excitation Amplitude ◽  
The Self ◽  
Bolted Joint ◽  
Minimum Threshold ◽  
Threaded Fasteners ◽  
Bolt Preload ◽  
Bearing Friction

This study develops an analytical formula for determining the minimum initial preload required to prevent the self-loosening of preloaded countersunk fasteners that are subjected to cyclic transverse loading. The formula is based on mathematical modeling of the self-loosening behavior of the fastener. The accurate prediction of the minimum bolt preload required for preventing loosening would reliably enable the use of that minimum threshold preload as a primary locking feature in critical bolted joint applications. An experimental setup and test procedure is established to compare the model prediction with the experimental data. The focus of this paper is to investigate the effect of thread pitch, excitation amplitude, as well as the bearing friction coefficient on the threshold value of the bolt preload that would prevent loosening.

Self-Loosening of Threaded Fasteners Due to Cyclic Transverse Loads

2005 ◽  
Author(s):  
S. A. Nassar ◽  
B. A. Housari
Keyword(s):  
Mathematical Model ◽  
The Self ◽  
External Loading ◽  
Transverse Displacement ◽  
Transverse Loads ◽  
Threaded Fasteners ◽  
Transverse Excitation ◽  
Set Up ◽  
Number Of Cycles ◽  
The Mathematical Model

A mathematical model and an experimental procedure are presented for studying the self-loosening phenomenon of threaded fasteners that are subjected to cyclic transverse loads. The effect of thread and underhead friction coefficients, the hole clearance, and the frequency and the amplitude of the transverse excitation are investigated. The experimental set up is made of a single-bolt joint, which is subjected to a cyclic transverse displacement or force. For each variable, the drop in the fastener tension and the joint clamp load versus the number of cycles is recorded and analyzed. In the mathematical model, the linear and angular motion of the bolt head is formulated in terms of the system properties and the external cyclic transverse excitation. The mathematical model 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 drop-off in the fastener tension due the self-loosening. Mathematical and experimental results are compared for various levels of system and external loading variables.

Effect of Thread Profile Angle and Geometry Clearance on the Loosening Performance of a Preloaded Bolt-Nut System Under Harmonic Transverse Excitation

2011 ◽  
Author(s):  
Xianjie Yang ◽  
Sayed A. Nassar
Keyword(s):  
Mathematical Model ◽  
Analytical Model ◽  
Experimental Verification ◽  
Good Accuracy ◽  
Profile Angle ◽  
Bolt Preload ◽  
Transverse Excitation ◽  
Proposed Model ◽  
Thread Profile ◽  
Number Of Cycles

A mathematical model is proposed for investigating the effect of the thread profile angle, thread and hole clearances on the loosening behavior of a preloaded bolt-nut system that is subjected to cyclic transverse excitation. Experimental verification of the analytical model results is provided for various levels of the initial bolt preload and frictional characteristics. Comparison of the experimental and analytical results on the clamp load decay with the number of cycles verifies that the proposed model predicts the loosening performance with good accuracy.

scholarly journals Experimental investigation on self-loosening of a bolted joint under cyclical temperature changes

2021 ◽  
Vol 13 (8) ◽  
pp. 168781402110394
Author(s):  
Oybek Maripjon Ugli Eraliev ◽  
Yi-He Zhang ◽  
Kwang-Hee Lee ◽  
Chul-Hee Lee
Keyword(s):  
Experimental Investigation ◽  
Stainless Steel ◽  
Temperature Variation ◽  
The Self ◽  
Experimental Results ◽  
Bolted Joints ◽  
Bolted Joint ◽  
Temperature Changes ◽  
Threaded Fasteners ◽  
Bolt Preload

The most commonly used part in engineering fields is threaded fasteners. There are a lot of advantages of fasteners. One of them is that they can be easily disassembled and reused, but a bolted joint can loosen easily when a transversal load is applied. The clamp load of a bolted joint can also loosen slowly when subjected to repeated temperature changes. This paper presents an experimental investigation of the self-loosening of bolted joints under cyclical temperature variation. Experiments are carried out under several cyclical temperature changes with different bolt preloads. Rectangular threaded bolted joints with M12 × 1.75 bolts and nuts are tested in a specially designed testing apparatus. Material of bolt, nut, and plates is a stainless steel. The experimental results show that the high initial bolt preload may prevent the joint from self-loosening and the bolted joint has loosened significantly in the first cycle of temperature changes. From this investigation, the loosening of the bolted joint can be considered as a first stage self-loosening.

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.

Formulation of a Criterion for Preventing Self-Loosening of Threaded Fasteners Due to Cyclic Transverse Loading

2010 ◽  
Author(s):  
Xianjie Yang ◽  
Sayed Nassar ◽  
Zhijun Wu
Keyword(s):  
Test Procedure ◽  
Closed Form Solution ◽  
Form Solution ◽  
The Self ◽  
Experimental Setup ◽  
Transverse Loading ◽  
System Parameters ◽  
Threaded Fasteners ◽  
Transverse Excitation ◽  
Key Variables

In the paper, a novel criterion is developed for preventing the self-loosening of preloaded threaded fasteners under cyclic transverse loading. For a known cyclic excitation, the system parameters are used in the formulation of a closed form solution for the minimum fastener preload required for preventing self-loosening. The effect of several key variables is investigated; this includes bearing and thread friction coefficients, bolt grip length, thread pitch, material, and the cyclic amplitude of the transverse excitation. An experimental setup and test procedure is established. Comparison between the experimental and analytical clamp load variation results shows that the proposed criterion can accurately predict the requirements for preventing self-loosening.

The Relationship between Seeker and Spiritual Guide as portrayed in contemporary Western Sufi Autobiographies

2011 ◽  
Vol 5 (2) ◽  
pp. 297-332
Author(s):  
Kate Zebiri
Keyword(s):  
Life Writing ◽  
New Age ◽  
The Self ◽  
Individual Autonomy ◽  
Religious Authority ◽  
The Face ◽  
The Relationship ◽  
Insight Into ◽  
Continuity And Discontinuity

This article aims to explore the Shaykh-mur?d (disciple) or teacher-pupil relationship as portrayed in Western Sufi life writing in recent decades, observing elements of continuity and discontinuity with classical Sufism. Additionally, it traces the influence on the texts of certain developments in religiosity in contemporary Western societies, especially New Age understandings of religious authority. Studying these works will provide an insight into the diversity of expressions of contemporary Sufism, while shedding light on a phenomenon which seems to fly in the face of contemporary social and religious trends which deemphasize external authority and promote the authority of the self or individual autonomy.

Die Eigen-Werte der Literatur

2009 ◽  
Vol 54 (1) ◽  
pp. 103-119
Author(s):  
Matthias Bickenbach
Keyword(s):  
The Self ◽  
Literary Writing ◽  
Self Organisation ◽  
Insight Into

Eine der zentralen Fragen moderner Poetik ist, wie der Werkentstehungsprozeß von kreativer Materialfülle zur ästhetischen Bestimmtheit des Erzählten als autonomem Kunstwerk übergeht. Sten Nadolnys Poetikvorlesung gibt überraschende Einsichten in die Selbstorganisation von Steuerungsbewegungen, die noch unterhalb der Ebene des Schreibens liegen und die als Theorie der Eigenwerte in der Literatur herauszustellen ist. One of the central questions in modern poetics is, how literary writing proceeds from the creative richness of its material to an aesthetic determination as autonomous art. Sten Nadolnys lectures on his poetics enable an astonishing insight into the self-organisation of operations beyond writing, which can be considered as a theory of self-values in literature.

Speed vs. comfort: Testing the efficacy of a single question for predicting transit users’ route choices

2019 ◽  
Author(s):  
Joseph John Pyne Simons ◽  
Ilya Farber
Keyword(s):  
Data Collection ◽  
Efficient Method ◽  
Choice Task ◽  
The Self ◽  
Self Report ◽  
Model Parameters ◽  
Single Item ◽  
Alternative Approach ◽  
Single Question ◽  
Insight Into

Not all transit users have the same preferences when making route decisions. Understanding the factors driving this heterogeneity enables better tailoring of policies, interventions, and messaging. However, existing methods for assessing these factors require extensive data collection. Here we present an alternative approach - an easily-administered single item measure of overall preference for speed versus comfort. Scores on the self-report item predict decisions in a choice task and account for a proportion of the differences in model parameters between people (n=298). This single item can easily be included on existing travel surveys, and provides an efficient method to both anticipate the choices of users and gain more general insight into their preferences.

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