A Mathematical Model for Vibration-Induced Loosening of Preloaded Threaded Fasteners

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Sayed A. Nassar ◽  
Xianjie Yang
Keyword(s):  
Mathematical Model ◽  
Shear Force ◽  
Bending Moment ◽  
Friction Torque ◽  
Shear Forces ◽  
Cyclic Shear ◽  
Threaded Fasteners ◽  
Bolt Preload ◽  
Transverse Excitation ◽  
The Relationship

A mathematical model is proposed for studying the vibration induced loosening of threaded fasteners that are subjected to harmonic transverse excitation, which often causes slippage between the contact surfaces between engaged threads and under the bolt head. Integral equations are derived for the cyclic shear forces as well as the bearing and thread friction torque components. They depend on the ratio of the relative rotational to translational velocities. The relationship between the dynamic thread shear force and bending moment is developed. When the external transverse excitation is large enough, it causes the threaded fasteners to loosen. Numerical results show that the dynamic transverse shear forces on the underhead contact surface, and between the engaged threads, decrease the bearing, and thread friction torque components. The effect of bolt preload, bearing and thread friction coefficients, the amplitude of the harmonic transverse excitation, and the bolt underhead bending on the bolt loosening are investigated. Experimental verification of the analytical model results of the bolt twisting torque is provided.

scholarly journals Deformation Control Method of the Antislide Pile under Trapezoidal Load in the Zhangjiawan Landslide

2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Hao Wang ◽  
Zhiying Lv ◽  
Hongyu Qin ◽  
Jianwei Yue ◽  
Jianwei Zhang
Keyword(s):  
Driving Force ◽  
Shear Force ◽  
Control Method ◽  
Slip Surface ◽  
Quadratic Function ◽  
Bending Moment ◽  
Site Investigation ◽  
Horizontal Displacement ◽  
Pile Head ◽  
The Relationship

Antislide piles are set in the Zhangjiawan landslide area, where the general features of the bedrock below the slip surface include upper weak and lower hard strata. Based on a site investigation, the horizontal displacement of the antislide pile head is 14.8 cm, which is not conducive to the stability of the landslide. In the study, a displacement calculation method for the pile under trapezoidal load is proposed for a colluvial landslide controlling. Furthermore, factors affecting the deformation and internal forces of the pile were also studied. The results indicated that (1) when the embedded length of an antislide pile increases, the horizontal displacement on the pile and maximum absolute shear force decrease, while the bending moment of the pile exhibits opposite trends; (2) the relationship between maximum shear force and maximum bending moment is linear with increasing driving force of landslide; and (3) increase in the ratio of the driving force between the pile head and slip surface (q0/q1) steadily increases the horizontal displacement of the pile. The relationship between the distribution of the driving force (q0/q1) and the reasonable embedded length of a pile is a quadratic function, which can be used to determine the reasonable embedded length of a pile under the action of rectangular or triangular loads. It is very useful to use the above method to guide the design of antislide piles in similar areas.

Load-bearing capacity and characteristic forms of destruction of furniture joints made with rastex 15 and P-10 clamex fasteners

2019 ◽  
Vol 106 ◽  
pp. 38-48
Author(s):  
Maciej Sydor ◽  
PIOTR POHL
Keyword(s):  
Bearing Capacity ◽  
Load Capacity ◽  
Bending Moment ◽  
Shear Forces ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Angular Deflection ◽  
Maximal Load ◽  
Rigidity Coefficient ◽  
The Relationship

Load-bearing capacity and characteristic forms of destruction of furniture joints made with rastex 15 and P-10 clamex fasteners. The study tested the relationship between the load and angular deflection in furniture joints. The tests were carried out for two types of fasteners and five types of materials: chipboard, MDF, hardwood plywood, glued pine boards and glued oak boards. The furniture joint samples contained two fasteners preloaded only with a bending moment (without application of shear forces). The results were converted per single fastener specifying: its maximal load capacity, 50 mrad (2.9°) limit deflection and rigidity coefficient. It was found that rigidity is a better structural property of the tested joint types than their load capacity. As far as rigidity is concerned, the most durable is the combination of oak glued board – rastex 15 fastener (13.2 Nm bending moment per fastener), while the least durable combination is chipboard – clamex P-10 fastener (4.8 Nm bending moment per fastener). Photographic documentation of damaged furniture joint samples was prepared and analysed. In case of chipboard and MDF combinations (where the load is determined by the combined material), the combined boards suffer a disastrous damage, while in combinations of plywood boards and pine or oak glued boards, (where the capacity is determined by the fastener), both clamex P10 and rastex 15 fasteners are damaged.

Effect of Fastener Under Head Contact on the Early Stage of Self-Loosening of Preloaded Countersunk Fasteners Subjected to Cyclic Shear Loading

2014 ◽  
Author(s):  
Amro M. Zaki ◽  
Sayed A. Nassar
Keyword(s):  
Early Stage ◽  
Three Dimensional ◽  
Element Model ◽  
Shear Loading ◽  
Cyclic Shear ◽  
Fea Model ◽  
Threaded Fasteners ◽  
Transverse Excitation ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Three dimensional Finite Element model is used to investigate the loosening behavior of countersunk threaded fasteners subjected to cyclic shear loading applied through prescribed transverse excitation to the fastener head. Fasteners with conical head profile require precision machining of both the fastener head and the mating joint hole. Any mismatch between the head and the joint conical angles affects the torque tension relationship as well as the loosening performance. Investigation focuses on the loosening behavior in its early stages. Factors investigated include the effect of the bolt head/joint hole contact location, joint elastic modulus, and tapped hole clearance for different combinations of thread fit, on the loosening performance of preloaded countersunk-head bolts. The FEA model prediction of the self-loosening behavior is experimentally validated.

A Method for Calculating the Amount of the Deflection and Force-Energy Parameters for Copper-Clad Steel Tube in the Process of Straightening

2013 ◽  
Vol 477-478 ◽  
pp. 137-140
Author(s):  
Liang Yu Xia ◽  
Dong Ming Sun ◽  
Gui Rong Kang ◽  
Jian Sun
Keyword(s):  
Mathematical Model ◽  
Engineering Application ◽  
Bending Moment ◽  
Scientific Basis ◽  
Steel Tube ◽  
Elastic Plastic ◽  
Energy Parameters ◽  
Continuous Bending ◽  
Clad Steel ◽  
The Relationship

Based on Roller Straightening Theory and Elastic-Plastic Beam Research, A Appropriate Mathematical Model of Straightening has Set up.The Author Regards the Tube as a Continuous Bending Beam and Discuss in Detail the Relationship between the Straightening Force and the Bending Moment. Calculating the Amount of Deflection for Tube. in this way ,it Provided a Scientific Basis for the Copper-Clad Steel Tube Straightening Parameter Set and Engineering Application.

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.

A New Approach to Analyzing Reactions and Deflections of Beams: Formulation and Examples

2006 ◽  
Author(s):  
I. C. Jong ◽  
J. J. Rencis ◽  
H. T. Grandin
Keyword(s):  
Boundary Conditions ◽  
Shear Force ◽  
Flexural Rigidity ◽  
Bending Moment ◽  
Bending Moments ◽  
Shear Forces ◽  
Concentrated Force ◽  
New Approach ◽  
Concentrated Forces ◽  
The Right

This paper is aimed at developing a new approach to analyzing statically indeterminate reactions at supports, as well as the slopes and deflections, of beams. The approach uses a set of four general formulas, derived using singularity functions. These formulas are expressed in terms of shear forces, bending moments, distributed loads, slopes, and deflections of a beam having a constant flexural rigidity and carrying typical loads. These loads include (a) a bending moment and a shear force at the left, as well as at the right, end of the beam; (b) a concentrated force, as well as a concentrated moment, somewhere on the beam; and (c) a uniformly, as well as a linearly varying, distributed force over a portion of the beam. The approach allows one to treat reactions at supports (even supports not at the ends of a beam) as concentrated forces or moments, where corresponding boundary conditions at the points of supports are to be imposed. This feature allows one to readily determine reactions at supports as well as slopes and deflections of beams. A beam needs to be divided into segments for study if it contains discontinuities in slope at hinge connections or different flexural rigidities in different segments. Several examples are included to illustrate the new approach.

Evaluation of Torque vs. Closure Bolt Preload for a Typical Containment Vessel Under Service Conditions

2010 ◽  
Author(s):  
Allen C. Smith
Keyword(s):  
Internal Pressure ◽  
Radioactive Material ◽  
Impact Loads ◽  
Extensive Literature ◽  
Radioactive Materials ◽  
Threaded Fasteners ◽  
Bolt Preload ◽  
Pressure Impact ◽  
Service Conditions ◽  
The Relationship

Radioactive material package containment vessels typically employ bolted closures of various configurations. Closure bolts must retain the lid of a package and must maintain required seal loads, while subjected to internal pressure, impact loads and vibration. The need for insuring that the specified preload is achieved in closure bolts for radioactive materials packagings has been a continual subject of concern for both designers and regulatory reviewers. The extensive literature on threaded fasteners provides sound guidance on design and torque specification for closure bolts. The literature also shows the uncertainty associated with use of torque to establish preload is typically between 10 and 35%. These studies have been performed under controlled, laboratory conditions. The ability to insure required preload in normal service is, consequently, an important question. The study described here investigated the relationship between indicated torque and resulting bolt load for a typical radioactive materials package closure using methods available under normal service conditions.

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 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.

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