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The purpose of this paper is to propose a bolt loosening detection approach which integrates piezoelectric ceramics with active sensor technology.

When the ultrasonic wave propagates across the contact surface at the bolted joints, because of the existence of imperfect interface, only part of the ultrasonic wave energy is passed through it. According to the Hertz contact theory, the passed energy depends on the true contact area which is decided by the bolt pretension. Hence, by measuring the received energy with the sensing piezoelectric material, the bolt pretension or bolt loosening can be detected.

The experiment revealed that the wave energy propagated across the interface is strongly correlated to the torque level. This relationship will be a good indicator to detect the status of bolted joints. The presented method has a potential application for the monitoring of bolt load loss in-site. Moreover, some factors which will affect the propagation of ultrasonic wave across the bolted joints are discussed in this paper.

This paper provides a good criterion to detect bolt load loss.

The purpose of this paper is to give a brief introduction of helical spring locked washer along with extensive literatures survey on role of helical spring locked washer in bolted joint analysis. It is very small component of bolted joint assembly, but it play vital role in holding the assembly components together. Helical shape of it produces spring effect in the assembly which is used for keeping the assembly in tension and that is lock the assembly under dynamic loading due to vibrations to avoid the accident.

The critical literatures survey identifies role of helical spring locked washer in different areas such as design optimization, mechanism of loosening-resistant components, bolted joint analysis, finite element-based modeling, analysis and simulation. The related literatures show contribution of helical spring washers in evaluation of anti-loosening performance of assemblies as compare to other types of washers.

It proposed that design optimization of helical spring locked washer is needed as it improves the performance in the form of load-deflection characteristics, load bearing capacity and provides the best locking force for optimize functionality.

The originality or value of this paper is to finding research gaps in literatures by dividing literatures into seven different research areas and concentrating the only on role of helical spring locked washer in bolted joint analysis.

In order to connect a fiberglass composite structure to a steel structure, a hybrid composite made of glass and steel fibers has been studied. The hybrid composite has one end section with all glass fibers and the opposite end section with all steel fibers. As a result, it contains a transition section in the middle of the hybrid composite changing from glass fibers to steel fibers. The purpose of this paper is to examine interface strength at the glass to steel fiber transition section, in order to evaluate the effectiveness of the hybrid composite as a joining technique between a polymer composite structure and a metallic structure.

The present micromechanical study considers two types of glass to steel fiber joints: butt and overlap joints. For the butt joint, the end shape of the steel fiber is also modified to determine its effect on interface strength. The interface strength is predicted numerically based on the virtual crack closure technique to determine which joint is the strongest under various loading conditions such as tension, shear and bending. Numerical models include resin layers discretely. A virtual crack is considered inside the resin, at the resin/glass‐layer interface, and at the resin/steel‐layer interface. The crack is located at the critical regions of the joints.

Overall, the butt joint is stronger than the overlap joint regardless of loading types and directions. Furthermore, modification of an end shape of the middle fiber layers in the butt joint shifts the critical failure location.

The paper describes one of a few studies which investigated the interface strength of the hybrid joint made of fiberglass and steel‐fiber composites. This joint is important to connect a polymeric composite structure to a metallic structure without using conventional mechanical joints.

The purpose is to predict the distribution of the residual pretightening force of the bolt group under the action of any initial pretightening force, and to achieve the final residual pretightening force as the target to solve the initial pretightening force value to be applied.

Based on the finite element method and the elastic interaction theory between bolt group, this paper establishes a prediction model for the residual pretightening force distribution of bolt group for one-step pretightening and multi-step pretightening of gasketless flange connection systems. In addition, using the general modeling method given in this paper, the prediction model of residual pretightening force of long plate bolt connection system is established, and compared with reference, which fully proves the effectiveness and universality of the general prediction model of residual pretightening force of bolt group.

The appropriate pretightening sequence, increasing the number of pretightening steps and variable amplitude loading can effectively reduce the influence of elastic interaction and improve the uniformity of residual pretightening force of the bolt group. And the selection of material, number of bolts and connected thickness of bolt connection system also has a great influence on the distribution of residual pretightening force of bolt groups.

The general prediction model for the residual pretightening force of bolt group of connecting structural components considering elastic interaction given in this paper can provide a reference for the design and optimization of the bolt assembly process of the rotor system and the casing system in aero-engine and the prediction of the performance of the connecting system.

In this paper, the author seeks to present in easy‐to‐understand diagrams the effect of external loads on the pretensioned bolt in a bolted joint. In most cases, bolted joints are tightened up with little thought for the size of the external loads that may later be imposed upon them. Since external loads always change the preload in the bolt, it is important to know by how much the bolt load changes. Too much preload leaves too little margin for the external or working load; too little preload and the cyclic stresses cause the bolt to fatigue, assuming the bolted joint is subjected to frequent working loads. No two bolts are alike, even under the most rigorous quality control production methods, but with more sophisticated nut and bolt tightening equipment coming onto the market, better results can be achieved. The use of these diagrams will help engineers and designers understand what is happening in the bolted joint.

The prevention of fatigue in bolts by controlled pre‐tensioning is investigated theoretically. It is shown that the effect of pre‐tension is to reduce the alternating load in the bolt and that the stiffness of the fitting plays an important part in this reduction. Fatigue tests on ¾‐in. B.S.F. bolts with various amounts of pre‐tension show how this reduction in alternating load can prevent fatigue failure. A warning is given against relying on the benefits of pre‐tensioning without ensuring that pre‐tension is maintained in service.

This paper aims to address a need for improving the structural resilience to multi-hazard threats including fire and progressive collapse caused by the loss of a column.

The focus is on a steel moment frame that uses welded-unreinforced flange-bolted web connections between the beams and columns. A three-dimensional finite element (FE) model was created in ABAQUS with temperature-dependent properties for steel based on the Eurocode. The model was validated against experimental data at ambient and elevated temperature.

The failure mechanisms in the FE model were consistent with experimental observations. Two scenarios were considered: fixed load with increasing temperature (i.e. simulating column failure prior to fire) and fixed temperature with increasing load (i.e. simulating column failure during fire).

A macro element (or component-based) model was also introduced and validated against the FE model and the experimental data, offering the possibility of analyzing large-scale structural systems with reasonable accuracy and improved computational efficiency.

Bolted joints are the most common type of mechanical connections, and improving the anti-loosening performance of bolts for the reliable performance of mechanical and building structures is highly significant.

Because of the lack of sufficient theoretical basis for the evaluation and design of anti-loosening bolts, a quantitative evaluation model exhibiting the following two evaluation criteria for anti-loosening bolts is introduced: bolt rotation angular acceleration criterion and critical transverse load criterion. Based on the relationship among bolt tension, transverse load and bolt rotation angular acceleration, a critical transverse load calculation model is put forward, and the mechanism by which the critical transverse load increases with the increase of bolt tension is revealed.

Based on the above model, a new type of anti-loosening bolt is designed, which generates additional bolt tension when the transverse load increases, and then improves the critical transverse load of the bolt. The effectiveness of the new type of anti-loosening bolt is verified by theoretical calculations and experiments.

The proposed model and method set a preliminary theoretical foundation for the evaluation of bolt anti-loosening performance and the design of a new anti-loosening bolt.

The behaviour of bolt connections is illustrated by an example of eccentrically loaded plate strip, examined on a FE model with a description of the beam model of this connection. The development of a general‐purpose beam model is described with particular emphasis being given to experimental justification, comparison with similar computing methods, and design applications of the model. The restrictions in the use of the model which are dependent on external dimensions of connected parts and their basic form are also mentioned.

Threaded fasteners appear to be the best low cost option for applying a desired clamp load to assemble a joint, which can be disassembled, if necessary, at a low cost. A large number of joint failures are due to inadequate tension on the joint. Most conventional tightening methods only provide a vague indication of the bolt tension. In this paper we will discuss the development of the A‐BOLT™ system, which can measure the tension in the mechanical bolt to ±1 per cent accuracy of the proof load. The key element of the system is a specially designed mechanical bolt with a top‐mounted sensor to measure the bolt elongation. We will also describe the development of different generations of the A‐BOLT™ system and its industrial applications. Finally we will present an overview of research on the cluster based networking of wireless sensors to minimize energy consumption in a network of sensors.