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In this paper, a real-time railway fastener detection system using a high-speed laser range finder camera is presented. First, an extensive analysis of various methods based on pixel-wise and histogram similarities are conducted on a specific railway route. Then, a fusing stage is introduced which combines least correlated approaches also considering the performance upgrade after fusing. Then, the resulting method is tested on a larger database collected from a different railway route. After observing repeated successes, the method is implemented on NI LabVIEW and run real-time with a high-speed 3-D camera placed under a railway carriage designed for railway quality inspection. [ABSTRACT FROM PUBLISHER]

Emerging applications of robots with direct physical interactions with humans have led to the development of a variety of series elastic actuators (SEAs) which are compliant, force controllable, and back drivable. The performance of current SEAs is mainly dependent on the specific stiffness of the spring. In our previous work, a compliant actuator with two-stage stiffness has been designed to overcome the performance limitations in current SEAs. The key novelty is that a low-stiffness spring and a high-stiffness spring are employed instead of a single spring in current SEAs, which has the advantages of high fidelity, low output impedance, and also large force range and bandwidth. In this paper, a tracking control scheme is proposed for the compliant actuator with two-stage stiffness. Although the overall stiffness is discontinuous, the proposed controller is continuous by integrating different control modes for two springs into a single one. The transition between control modes is smooth and embedded inside the controller, and it is also automatically realized by monitoring the output force of the actuator. The stability and convergence of the closed-loop system are analyzed, and experimental results are presented to demonstrate the effectiveness of the proposed control scheme.

Note to Practitioners—An SEA is developed by placing an elastic element into the actuator; this elasticity gives SEAs several unique properties including low mechanical output impedance, tolerance to impact loads, and passive mechanical energy storage, which makes it suitable for human–robot interaction. The performance of existing SEAs is highly dependent on the stiffness of a single spring. To overcome the limitations, a novel SEA with two-stage stiffness was proposed in our previous work. This paper suggests a continuous tracking control method for the proposed compliant actuator. Although the overall stiffness is discontinuous, the transition between different control modes for two springs is smooth and automatically realized. Experimental results show that the output force of the actuator is bounded. In future research, uncertainties in actuator dynamics will be considered, such that system identification or calibration is not required. [ABSTRACT FROM AUTHOR]

The fastener system is an important component of the ballastless track, and the fastener looseness threatens the safety of the railway track. This paper proposes a Bayesian model updating method integrated with a Python–Abaqus interface framework to identify the fastener partial looseness of the ballastless track via vibration data. By following the technical standards of Chinese Railway Industry, a laboratory scaled ballastless track model was constructed for the demonstration and verification of the proposed methodology. Not only the damage location can be accurately identified, but also the damage severity can be evaluated. In addition, the associated posterior uncertainties of the identified results can be quantified by calculating the posterior probability density functions of all uncertain model parameters, which can provide valuable information to engineers for ballastless track system damage detection. [ABSTRACT FROM AUTHOR]

Because of their superior mechanical properties, preformed helical fittings are widely used in UHV transmission lines. However, they easily slip and become loose under extreme environments, so it is very important to study the fastening characteristics of preformed helical fittings. According to the stress characteristics of preformed helical fittings, a parametric finite element model including a core and preformed armor rods was established. Finally, the finite element model calculation was verified by comparing it with the test results. In this paper, the influences of the preformed armor rod diameter, pitch, length and forming aperture on the fastening characteristics were investigated. The numerical simulation results showed that the smaller the forming aperture of preformed armor rods, the larger the grip force. However, a small forming aperture is inconvenient to install, and too large of a grip force on the core easily leads to core damage. With the increase in the preformed armor rod length, the grip force increased gradually and linearly, and the increase slowed after the pitch number reached 9. The larger the pitch, the smaller the grip force of the preformed helical fittings. The fastening characteristics of preformed armor rods with slightly larger diameters were better and the fourth power of the diameter of the preformed armor rods has a linear relationship with the grip force. [ABSTRACT FROM AUTHOR]

In tolerance analysis, the effect of clearance fits is especially difficult to estimate because the mating parts are not necessarily in actual contact and can take an infinite number of relative positions. The treatment of these situations is allowed in most of the available methods, possibly introducing additional elements in the dimension chains with appropriate statistical assumptions. The paper provides a similar extension for the static analogy, a previously proposed method that converts the tolerance analysis problem into an equivalent problem of force analysis. The procedure represents each fit, possibly between patterns of features (e.g., fasteners and holes), with a proper constraint in the equivalent static model. The ability of the constraint to transmit forces and torques is determined according to the types and directions of misalignments allowed by the joint clearance. With simple rules, this avoids complications in the static model, which must include only the constraint between parts rather than the geometric details of the mating features. The extended method, currently limited to 2D dimension chains, is demonstrated on examples involving both dimensional and geometric tolerances. The comparison with existing methods shows the correctness of the proposed procedure. The simplicity of the workflow confirms the possibility, already demonstrated for the static analogy, of avoiding numerical simulations or even the use of computer-based tools. [ABSTRACT FROM AUTHOR]

Railway track is a linearly inhomogeneous object that consists of geometrical and elastic discontinuities such as bridges, transition zones, rail joints and crossings. The zones are subjected to the development of local instabilities due to quicker deterioration than the other tracks. Until now, there have been no efficient approaches that could fully exclude the problem of accelerated differential settlements in the problem zones. Many structural countermeasures are directed at controlling the sleeper/ballast loading with the help of fastenings/under-sleeper pad elasticities, sleeper forms and additional bending stiffness reinforcements. However, the efficiency of the methods is difficult to compare. The current paper presents a systematic approach in which the loading distribution effect in the rail support by application of two bending reinforcement methods is compared: auxiliary rail and under-sleeper beam. The study considers only the static effects to reach a clear understanding the influence of the main factors. The track equivalent bending stiffness criterion is proposed for comparing reinforcement solutions. The analysis shows that the activation of the bending stiffness of the reinforcement beams depends on the relative ratio of the rail fastenings stiffness and track support stiffness under sleepers (or under the under-sleeper beam). The comparison demonstrates that conventional auxiliary rail reinforcement solutions are ineffective due to their weak bending because of the high elasticity of fastening clips and the main rail fastenings. The share of an auxiliary rail is maximally 20% in the track bending stiffness and cannot be significantly improved by additional rails. The under-sleeper beam-based reinforcement solutions show noticeably higher efficiency. The highest effect can be achieved by the activation of the horizontal shear interaction between the under-sleeper beam and the rail. The additional track bending stiffness of the under-sleeper-based solutions is about 3.5 times more of the rail one and could be potentially increased to 6–10 times. [ABSTRACT FROM AUTHOR]

Threaded fastening operations are widely used in assembly and are typically time-consuming and costly. In low-volume, high-value manufacturing, fastening operations are carried out manually by skilled workers. The existing approaches are found to be less flexible and robust for performing assembly in a less structured industrial environment. This paper introduces a novel algorithm for detecting the position and orientation of threaded holes and a new method for tightening bolts. First, the elliptic arc fitting method and the three-point method are used to estimate the initial position and orientation of the threaded hole, and the force impact caused by switching from the free space to the constrained space during bolt tightening is solved. Second, by monitoring the deformation of passive compliance, the position information is introduced into the control process to better control the radial force between the bolt and the threaded hole in the tightening process. The constant force controller and orientation compliance controller are designed according to the adaptive control theory. A series of experiments are carried out. The results show that the proposed method can estimate the initial position and orientation of an M24 bolt with an average position error of 0.36 mm, 0.43 mm and 0.46 mm and an orientation error of 0.65°, 0.46° and 0.59°, and it can tighten the bolt with a success rate of 98.5%. [ABSTRACT FROM AUTHOR]

Quality assessment of stiffness and load-carrying capacity of composite connections is of great importance when it comes to designing timber–concrete composite structures. The new European regulation intended explicitly for timber–concrete structures has made a significant contribution to this field, considering that until today there was no adequate design standard. Due to the proposed general expressions for determining the stiffness and load-carrying capacity of composite connections made with dowel-type fasteners, which are incapable of describing most of the commonly applied fasteners, engineering, and scientific practice remained deprived of a quality assessment of the essential mechanical properties of the connection. In order to overcome this problem, this paper proposes a numerical model of the connection suitable for determining the whole load–slip curve, allowing it to estimate the stiffness and load-carrying capacity of the connection. The model was developed by considering the non-linear behavior of timber and fasteners, which is determined through simple experimental tests. For the numerical model validation, experimental tests were carried out at the level of the applied materials and on the models of the composite connection. Through numerical simulations, analysis of obtained results, and comparison with experimental values, it can be confirmed that it is possible to simulate the pronounced non-linear behavior of the timber–concrete connection using the proposed model. The estimated values of stiffness and load-carrying capacity are in agreement with the conducted experimental testing. At the same time, the deviations are much less than the ones obtained from recommendations given by the new regulation. Additionally, apart from evaluating the value and the simulation of the complete curve, it is possible to determine local effects, such as the crushing depth in timber and concrete, the fastener's rotation, and the participation of forces in the final capacity of the connection. [ABSTRACT FROM AUTHOR]

To this day, most of the papers related to hybrid joints were focused on single and double lap joints in which shear deformation and degradation was the dominant phenomenon. However, in real constructions, complex state of loads can be created by: a) torsion with shear, b) bending with shear, c) torsion with tensile. Analytical and numerical computation for simple mechanical joints is known, however, the introduction of an adhesive layer to this joint makes the load transferred both through: (1) the adhesive and (2) mechanical fasteners. There is also an interaction between the amount and stiffness of mechanical fasteners and the strength of the adhesive layer. The paper presents the results of numerical calculations for the bending with shear type of load for the hybrid structural joint and corresponding simple joints by: (1) pure adhesion and (2) rivets with different quantity maintaining the same cross-sectional area. A total of 9 simulations were performed for: (1) 4 types of pure rivets connections, (2) pure adhesive joint and (3) 4 kinds of hybrid joints. The surface-based cohesive behavior was used for creation of the adhesive layer, whereas the rivets were modelled by connector type fasteners, which simplify complexity of the numerical model. The use of connectors allowed for effort assessment taking into account damage in both types of connections. Application of connector elements can be useful for larger structures modelling, e.g. aircraft fuselage, where the number of mechanical joints is significant and complex load conditions occur. [ABSTRACT FROM AUTHOR]

This paper is an investigation in the performance of two types of magnetic screws (MSs). The first is the magnet to magnet and consists of permanent magnet (PM) nut and PM screw and the second is a magnet to reluctance and consists of PM nut and a double-start reluctance screw. It is argued that for cost sensitive and long stoke applications, a magnet-to-reluctance MS may be the preferred option. It is also shown that capacitor discharge magnetization techniques can be employed for imprinting helical magnetization distributions on cylindrical PMs, significantly reducing the complexity and facilitating the practical realization of MS systems. [ABSTRACT FROM AUTHOR]

This paper presents a gain-enhanced circularly polarized (CP) patch antenna, where 3-D printing and computer numerical control machining technologies are employed for the fabrication of its dielectric and metal parts, respectively. In order to assemble the whole structure effectively and accurately, a hybrid strategy and pin-loaded example are here proposed to deal with the detached dielectric and metal. On the one hand, asymmetrically 3-D printed substrate with the mesh-grid architecture is formed with resin chunks to introduce the perturbation and produce the CP radiation. On the other hand, its metal part likewise possesses the 3-D structure with four metal screws to be symmetrically placed in the two diagonals of square patch, thus making the patch and ground as a whole. More importantly, the screws have dual functions, which can not only integrate the dielectric and metal parts, but also work as shorting pins. Therefore, due to the shunt inductive effect of shorting pins, the dominant mode of patch is excited at higher frequency, resulting in the enlarged antenna area and enhanced gain. As a result, the gain-enhanced CP patch antenna is realized, and an antenna prototype is then fabricated and tested, exhibiting a high CP gain of about 10 dBic. [ABSTRACT FROM AUTHOR]

This paper reports on mechanical design, optimization, and experimental testing of a novel piezo-actuated elliptical vibration-assisted cutting (EVC) system constructed by flexure hinges. The stroke and natural frequency were analyzed based on the theoretical modeling. An enhanced central composite design was chosen as the design of experiments methodology to reduce the modeling error, and a nondominated sorted genetic algorithm-II (NSGA-II) was adopted for structure optimization. The optimized EVC generator was manufactured and experimentally tested to investigate practical properties of the proposed EVC system. It shows that the stroke of input end can reach to 30 μ m with a motion resolution of 10 nm, and the first natural frequency can reach to 2600 Hz without considering the manufacturing error. Besides, a relatively small cross-axis coupling ratio (within 0.21%) can be effectively obtained. The developed EVC system is advantageous not only to being equipped with machine tools with various configurations, but also to easily achieving arbitrary vibrations in three-dimensional space through two actuators, which is especially important for the generation of complex structured surfaces. With this paper, it is of great significance to promote industrial application of EVC techniques. [ABSTRACT FROM AUTHOR]

The Hessian matrix, one of the most pivotal parts in a robotic system's acceleration model, is a prerequisite for dynamic modeling and control of parallel robots. Aimed at providing a straightforward and effective way for modeling, design, and control of parallel robots, a new approach to formulate the Hessian matrix using the finite and instantaneous screw theory is presented in this paper. The new approach is generalizable in that it can be used to formulate the Hessian matrix of any parallel robot in a simple and concise manner. It also provides a theoretical foundation for the dynamic control of industrial robotic systems with parallel structures. The new approach is verified through comparison with the traditional exponential matrix method. The Exechon parallel robot and a hybrid serial-parallel robot are used as examples to further detail the procedures of this approach. The acceleration model formulated in this paper is closely related with the topological and parametric models, resulting in a unified mathematical framework for modeling and control of parallel robots. [ABSTRACT FROM AUTHOR]

This paper presents a new type electromagnetic lead screw (EMLS) intended for wave energy application. Similar to the mechanical lead screw, this electromagnetic version can transfer slow linear motion to high-rotational motion, offering gearing effects. Compared with the existing pure magnetic lead screw (MLS) employing permanent magnets only, the new EMLS proposed uses dc current to provide the required helical-shape magnetic field, offering a much simpler, robust structure compared with the MLS. The working principle and the performances of this EMLS are analyzed in this paper. Comparison with PM-type lead screw is given. In addition to this, the theoretical analysis to support the use of a 2-D finite element model to analyze the 3-D magnetic-type lead screw is given, which has not been well covered in the existing literature. [ABSTRACT FROM AUTHOR]

Bolts constitute a very important subset of mechanical fasteners. In order to tighten bolts, a degree of bolt preload scatter is to be expected. Since the torque control of tightening bolts is the most popular means of controlling the preload, an appropriate tightening torque becomes pivotal. This paper investigates the torque control problem of bolt tightening process. This process is not as simple as it looks because the inherently nonlinear process contains many uncertainties. To conquer the adverse effects of the uncertainties, this paper designs an adaptive-gain second-order sliding mode controller. Theoretically, such design can guarantee that the bolt tightening process has the closed-loop stability in the sense of Lyapunov. From the aspect of practice, the control method is carried out by a platform. Some comparisons illustrate the feasibility and effectiveness of the designed controller. [ABSTRACT FROM AUTHOR]

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The railway fastener, as a crucial component of railway tracks, directly influences the safety and stability of a railway system. However, in practical operation, fasteners are often in low-light conditions, such as at nighttime or within tunnels, posing significant challenges to defect detection equipment and limiting its effectiveness in real-world scenarios. To address this issue, this study proposes an unsupervised low-light image enhancement algorithm, CES-GAN, which achieves the model's generalization and adaptability under different environmental conditions. The CES-GAN network architecture adopts a U-Net model with five layers of downsampling and upsampling structures as the generator, incorporating both global and local discriminators to help the generator to preserve image details and textures during the reconstruction process, thus enhancing the realism and intricacy of the enhanced images. The combination of the feature-consistency loss, contrastive learning loss, and illumination loss functions in the generator structure, along with the discriminator loss function in the discriminator structure, collectively promotes the clarity, realism, and illumination consistency of the images, thereby improving the quality and usability of low-light images. Through the CES-GAN algorithm, this study provides reliable visual support for railway construction sites and ensures the stable operation and accurate operation of fastener identification equipment in complex environments. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method based on continuum damage mechanics (CDM) and machine learning (ML) models to evaluate the vibration fatigue behavior of W1‐type railway fastener clips subjected to high‐frequency vibration. Firstly, static and fatigue tests are conducted on 60Si2Mn spring steel to acquire elastic modulus, tensile strength, and P‐S‐N curves. Subsequently, a CDM model is established, and numerical simulations are performed under various working conditions to obtain the fatigue characteristics of the clips. Finally, the ML model is trained using numerical simulation results, thereby establishing a mapping model between the working conditions and fatigue characteristics. The developed ML model demonstrates high accuracy in predicting the vibration fatigue life of the clips. Moreover, the Shapley Additive Explanations (SHAP) algorithm is employed to elucidate the ML model, revealing that the vibration frequency has a greater impact on the fatigue life of the clips compared to the vibration displacement. Highlights: A novel approach is developed for vibration fatigue assessment of fastener clip.The approach effectively combines the continuum damage model and ML (ANN) model.Static and fatigue tests of 60Si2Mn spring steel are conducted.Fatigue characteristic of clips subjected to high‐frequency vibration is studied. [ABSTRACT FROM AUTHOR]

A rod fastening rotor is the core component of gas turbines, which affects the working stability and service life of the whole machine. The characterization of the contact mechanism of a joint's interface is a key problem in dynamic prediction. The aim of this paper is to gain insight into the influence of the joint's interface on the dynamic characteristics of the rod fastening rotor system. According to the equivalent bending stiffness of the joint's interface, the natural frequency of the system is obtained by the analytical method, where the normal contact stiffness of the joint's interface related to the frequency index is established on the theory of fractal contact analysis. After that, the effects of key parameters on the contact stiffness are discussed in detail. Finally, the variations in the vibration frequency are further revealed as well. [ABSTRACT FROM AUTHOR]

In this paper, the torsional moment of the right-angle fastener bolt is taken as the main research parameter, and the torsional stiffness performance of the right-angle fastener under different working conditions is studied experimentally. By establishing the moment–rotation relationship model of the node, the mechanical performance and rotation characteristics of the semirigid connection of the node are studied. According to the joint stiffness value determined by the experimental study and the theory of semirigid connection frame with lateral displacement, the calculation formulas of the stiffness correction coefficient α u of the transverse bar and the constraint coefficient K at the end of the vertical bar are derived, and the effective length coefficient μ of the vertical bar and the theoretical value of the stable bearing capacity of the vertical bar under different working conditions are given. Compared with the current standard values, it is found that the theoretical calculation results of the percentage increase of the stable bearing capacity of the vertical bar are 3 to 4 times larger than the standard calculation results when the step distance is reduced. The theoretical calculation method can better consider the semirigid characteristics of the joint and the influence of adjacent members on the stable bearing capacity of the vertical bar. [ABSTRACT FROM AUTHOR]

In the traditional pre-joining technology of aircraft panels, bolts are generally employed for pre-joining. Due to the length and width of panels, bilateral manual operations are required to operate bolts. In this case, there are problems such as low work efficiency, unstable quality, cumbersome operation, and inconvenient installation-removal. This paper takes a temporary fastener with one-side installation-removal as a research object and conducts in-depth research on three levels of quick-pressing: unloading, stable self-locking, and easy automatic installation. Firstly, by coordinating the ratchet and the spring, the restoring force of the spring is used to make the cylindrical top-rod rotary and realize the telescopic function to achieve quick loading and unloading of fasteners; subsequently, through the cooperation between the buckle and the spring, loading and unloading self-locking is attained; afterwards, through the threaded joining and the same cylinder design between the external profile components, the convenience of fasteners for automatic transportation is realized. When assembling two thin-walled parts of the aircraft, only continuous one-side pressing of fasteners is needed to carry out the tightening and unloading work, namely, one-pressing installation and one-pressing removal, which could solve the problems caused by the bilateral operation of traditional bolts and part tolerances. After the application of the fasteners into the pre-joining process of aircraft panels, the experiment results have shown that this temporary fastener provided a good clamping effect, could be quickly and efficiently installed and removed by continuous one-pressing, and avoided the problems of complexity and high cost for pre-joining processes. [ABSTRACT FROM AUTHOR]

Electrical resistance is among the characteristics that fastening systems must meet to ensure the proper functioning of signaling systems in railway infrastructure. The EN 13146-5:2012 standard specifies a laboratory testing method for determining the electrical resistance under wet conditions between running rails provided by a fastening system on steel or concrete sleepers. In urban railway tracks, the electrical resistance of fastening systems affects the stray current; however, there is no standardized electrical resistance measuring method. There is also no definition for the minimum value that the electrical resistance of fastening systems must satisfy to prevent stray currents. For this reason, this paper analysis the possibility of using the standard EN 13146-5:2012 for the measurement and analysis of the electrical resistance of fastening systems in urban railway tracks. In this study, the electrical resistance of different fastening systems used in urban railway tracks was measured. Based on the tests results, the modifications needed in the EN 13146-5 standard for it to be suitable for urban railway tracks were identified. The proposed modifications include the use of a DC current source. The test should be performed on a rail sample fastened to the concrete base, and the current circuit should be closed by the reference electrode installed in the base. Spraying water from nozzles is not applicable for this measurement. The test should be performed under dry conditions and at different water levels (water on the top of the concrete base and on the top of the levelling layer). Different water levels were used to simulate the most common conditions in urban railway tracks built as part of the road surface, where the track-drying process is very slow. The test should not be performed when the rails are immersed in water, because the current flows directly from the rail into the water in such case, and the fastening system has no influence on the measured electrical resistance value. In addition to describing the proposed changes, the calculation of the minimum electrical resistance value that fastening systems in urban railway tracks must satisfy is also presented. [ABSTRACT FROM AUTHOR]

The fire resistance of fasteners needs to be verified for all failure modes applicable at ambient conditions. Generally, in most cases, for unprotected fasteners loaded in tension, steel failure mode is decisive. But for fasteners made of stainless steel and/or larger (bolt) sizes, concrete cone failure may be the decisive failure mode for small anchorage depths. Due to practical difficulties associated with loading an anchor during a fire test, very limited experimental data is available in literature and that to for relatively small embedment depths. The paper presents the results (6 nos) of the fire tests conducted on expansion anchors (made of stainless steel) with sizes M12 (hef = 70 mm) and M20 (hef = 100 mm). Moreover, the paper also compares the reduction in the concrete cone capacity with exposure duration, predicted as per the current design guidelines and the new set of experimental data obtained in this study. [ABSTRACT FROM AUTHOR]

This paper proposes a mechatronic suspension system with capabilities of energy regeneration and semi-active control [i.e., skyhook (SK)], incorporated into the mechanism. The system overcomes the trade-off between energy consumption and ride handling/comfort in a semi-active/active suspension system. Central to the concept is the development of a switched-mode rectifier (SMR) capable of providing either a positive or negative damping ratio by controlling the electric current to alternate between regenerative and motoring modes. Using the implemented circuit, a regenerative SK control strategy is utilized to provide a continuous variable damping force that significantly improves the vibration isolation. Simulation results are presented to demonstrate power flow in both regenerating and motoring modes by utilizing a current controller. Furthermore, experimental results are presented highlighting performance of the regenerative suspension prototype in terms of power regeneration, sprung mass absolute acceleration, and relative displacement. In addition, both theoretical and experimental power conversion efficiencies in various segments of the mechatronic suspension are analyzed and reported. [ABSTRACT FROM PUBLISHER]

A novel substrateless power amplifier module realized by ridge gap waveguide (RGW) technology is proposed in Ka-band. Up to our knowledge, this is the first time that an active device is directly integrated with an RGW structure. No substrate is used in the RF section of the implemented power amplifier and the whole structure is made by machining a piece of metal. The amplifier was made of two pieces and was easily assembled without needing a precise contact between the two sections. The cavity resonance of the amplifier is suppressed using a pining structure. The fabricated amplifier module is self-packaged and does not need any packaging. It is shown that the simulated and measured results are in good agreement. This paper shows the capability of RGW technology for implementing the whole RF frontend in microwave- and millimeter-wave systems. [ABSTRACT FROM PUBLISHER]

For the safety of railways, well-trained workers are required to check the fastener constantly, which shows the disadvantage of large time cost, huge labor cost and might being dangerous to workers. To address this and achieve automatic detection, an inspection model based on deep convolutional neural network (DCNN) is adopted in this paper. However, the inspection model suffering from the unbalanced training samples of defective vs normal due to defective fasteners are far less than normal fasteners in real railways. To tackle this problem, a novel sample generation method is proposed to generate defective fastener samples using the normal fasteners to realize sample augmentation. The comprehensive experiments are conducted on the collected real fastener samples and generated samples. The experimental results show that our method has good performance for fastener inspection on unbalanced samples and outperforms other state-of-the-art methods. [ABSTRACT FROM AUTHOR]

This paper investigated the potential applicability of the specification equation for the shear pull-out strength of a power-actuated fastener (PAF) connection to nail connections between steel sheets thinner than 2.9 mm. The tested G300, G450, and G550 specimens had thicknesses ranging from 0.6 to 2.4 mm, connected with 2.5- or 3.6-mm helically knurled nails. The pull-out strength is a function not only of the thickness of the member not in contact with the fastener head, but also of the other member's thickness. The member thicknesses have greater influence than the nail diameter on the pull-out strength, contrary to the design equation. Based on the test results of 93 shear nailed connections failing in pull-out, the paper proposes a design equation that is applicable to connections using helically knurled nails of steel sheets thinner than 2.9 mm. A group effect factor of 0.75 is suggested for serial nail connections based on the test results of 19 multiple nail connections. A resistance factor of 0.55 is recommended for use with the proposed equation for determining the pull-out strength of shear nailed connections in thin steel sheets. An additional finding is that the current design equation for the bearing and tilting strength of a PAF connection is applicable to connections in which the member not in contact with the fastener head is much thinner than the specification minimum of 3.2 mm, and in which the fastener diameter is smaller than the specification minimum of 3.7 mm. [ABSTRACT FROM AUTHOR]

Light gauge metal decking is commonly used in the building and bridge industries for concrete formwork. In addition to supporting the wet concrete, the metal forms also improve the lateral-torsional buckling capacity of the beams or girders they are fastened to since they behave as a shear diaphragm and restrain the warping deformation of the top flange. The design requirements for shear diaphragm bracing are not well established. This is the second part of a two-part paper. The first part of the paper focused on the general stability bracing behavior for shear diaphragms connected to the top flanges of adjacent beams or girders. This part of the paper outlines the design requirements for shear diaphragm bracing and focuses on both the stiffness and strength requirements for beam stability. Design expressions are presented for the stiffness and strength requirements as well as a model that can be used to estimate the forces in the fasteners that connect the diaphragms to the top flanges of the beams. An example is presented at the end of the paper demonstrating the use of the design expressions. [ABSTRACT FROM AUTHOR]

Screwed‐head fastener is the common fabricated hold‐down bolt for steel structures and machine foundations. Although different models are available for evaluating its structural behavior, there are still aspects that need to be investigated. In particular, conflicting approaches for the design can be found among the European design‐oriented documents. Within this context, a comprehensive experimental study on screwed‐head fasteners under tensile loading was recently carried out at Milan Polytechnic. In this paper, some results are presented and commented which include (a) the presence of cracks and (b) the presence of supplementary reinforcement. In the discussion, predictive models are recalled demonstrating the need for a specific design approach, which should consider the geometry and the resistance of the fastening system, including that of the concrete member. Some design recommendations end the paper as useful guidance for the structural designer. [ABSTRACT FROM AUTHOR]

Disassembly is a vital step in any treatment stream of waste electrical and electronic equipment (WEEE), preventing hazardous and toxic chemicals and materials from damaging the ecosystem. However, the large variations and uncertainties in WEEE is a major limitation to the implementation of automation and robotics in this field. Therefore, the advancement of robotic and automation intelligence to be flexible in handling a variety of situations in WEEE disassembly is sought after. This paper presents an ontology-based cognitive method for generating actions for the disassembly of WEEE, with a focus on LCD monitors, handling uncertainties throughout the disassembly process. The system utilizes reasoning about relationships between a typical LCD monitor product, component features, common fastener types, and actions that the system is capable of, to determine 4 key stages of robotic disassembly: component identification, fastener identification, disassembly action generation, and identification of disassembly extent. Further uncertainties in the form of possible failure of action execution is reasoned about to provide new actions, and any unusual scenarios that result in incorrect reasoning outputs are rectified with user-demonstration as a last resort. The proposed method is trialed for the disassembly of LCD monitors and a product unknown to the system, in the form of a DVD-ROM drive. [ABSTRACT FROM AUTHOR]

This paper proposes a weighted large margin nearest center (WLMNC) distance-based human depth recovery method for tele-immersive video interaction systems with limited bandwidth consumption. In the remote stage, the proposed method highly compresses the depth data of the remote human into skeletal block structures by learning the WLMNC distance, which is equivalent to downsampling the human depth map at $64{\times}$ the sampling rate. In the local stage, the method first recovers a rough human depth map based on a WLMNC distance augmented clustering approach and then obtains a fine depth map based on a rough depth-guided autoregressive model to preserve the depth discontinuities and suppress texture copy artifacts. The proposed WLMNC distance is learned by the large margin clustering problem with a weighted hinge loss to balance the clustering accuracy and depth recovery accuracy and is verified to be able to preserve depth discontinuities between skeletal block structures with occlusion. A theoretical analysis is conducted to verify the effectiveness of using the weighted hinge loss. Furthermore, a novel data set containing various types of human postures with self-occlusion is built to benchmark the human depth recovery methods. The quantitative comparison with the state-of-the-art depth recovery methods on the introduced benchmark data set demonstrates the effectiveness of the proposed method for human depth recovery with such a high upsampling rate. [ABSTRACT FROM AUTHOR]

In this paper, we develop a stress wave-based active-sensing approach using piezoceramic transducers to detect the bolt looseness-induced damage in steel truss arch structures. A specimen of a steel tress arch structure was designed and fabricated. The structure consisted of top chords, bottom chords, Web members, and gusset plates, which were all connected by bolted connections. To implement the active sensing approach, the lead zirconate titanate (PZT) transducer bonded on the gusset plate was used as an actuator to generate stress waves, and the PZT transducers mounted on the other parts, such as top chords, bottom chords, and Web members, were used as sensors to detect the propagated stress waves. Based on the tightness of the bolts, the specimen had three different states: the healthy state, damage state I, and damage state II. The signals received by the PZT sensors were analyzed using the wavelet packet analysis. In addition, the structure stiffness was also considered as a comparative approach in this paper. The experimental results illustrate that when the initial looseness-induced damage occurs, the structure stiffness is not significantly reduced while the wavelet packet energy changes significantly, revealing the advantage of the proposed approach over the stiffness-based method. These research results demonstrated that the developed piezoceramic-based active-sensing approach has potentials to identify the initial bolt looseness occurrence for steel truss arch structures. [ABSTRACT FROM AUTHOR]

Controlled force–torque exertion by a small-scaled free-flying space robot will be potentially required for future on-orbit assembly missions. This paper presents a hybrid controller to achieve the desired end-effector motion and contact forces required for driving a screw into a floating target. Attitude of the spacecraft base is controlled simultaneously. Postcapture control to stabilize the entire system is also addressed in this paper. Simulation results have demonstrated the effectiveness of the proposed control laws. [ABSTRACT FROM AUTHOR]

The objective of this paper is to use electromagnetic-based computer-aided design (CAD) tools to investigate the maximum tuning range of channel filters, typically used in satellite payloads. Both circular and rectangular waveguide technologies are investigated. The results of the investigation show that single-mode rectangular waveguide implementations offer substantially wider tuning range, as opposed to classical dual-mode circular waveguide implementations. In addition to simulations, measurements are also presented indicating very good agreement with theory, thereby fully validating the CAD procedure. [ABSTRACT FROM PUBLISHER]

It is known a priori that vibrations that occur in the elements of the track structure during the passage of a train load are a superposition of free and forced mechanical vibrations. It has been established that the range of oscillation frequencies of the elements of the track superstructure includes oscillations with a frequency from tens to hundreds and thousands of hertz. However, the influence of vibrations on the track and their dependence, in turn, on the design of the track, has not been fully studied, which causes controversy between specialists in this matter. There is an opinion that in intermediate fastenings, the main role is played by an elastic gasket, which ensures the vertical rigidity of the rail-sleeper assembly. It has been experimentally established that in the frequency range below the frequency of free oscillations of rail fastenings, the force applied to the upper surface of the elastic gasket is transferred to the lower surface in an unchanged form. The article discusses the vibrations that occur in the elements of the upper structure of the track (rails, sleepers, rail fastenings, ballast base) during the passage of a moving load, which significantly affect the strength, and, consequently, the durability of both the elements themselves and the railway track generally. Vibrograms, oscillograms, accelerograms of rail oscillations and their spectra during the passage of TALGO are presented. At present, the VOSSLOH fastening, developed in Germany, has been widely used in the construction of tracks on high-speed railways of the Republic of Kazakhstan. In this regard, there is a need for a comprehensive study of the operation of this type of fastening under a train load. [ABSTRACT FROM AUTHOR]

This paper presents the results of twenty‐one fire tests on unprotected steel‐to‐timber connections with dowel‐type fasteners and one or two slotted‐in steel plates. The experimental results of this type of connections available in existing studies have been mostly limited to a fire resistance duration of 60 min. The tests performed in this study target a significant increase of fire resistance to reach 90 and 120 min. Two configurations of connections with one and two slotted‐in steel plates, i.e., two or four shear planes, were tested. The temperatures were measured at different locations in the wood members and along the steel plates. Two load levels for fire tests were determined on the basis of tests performed at ambient temperature. The experimental results show that the specimens proposed for steel‐to‐timber connections with dowel‐type fasteners are suitable for achieving fire resistance of 90 and 120 min. [ABSTRACT FROM AUTHOR]

This paper is focused on the electrical and mechanical performance of aluminum-copper hybrid busbars subjected to corrosion over time. Two different types of hybrid busbars with joints produced by conventional fastening with M8 hexagonal socket head bolt-nut pairs made from medium carbon steel and by a new injection lap riveting process with semi-tubular rivets made from the material of the softer conductor are used and subjected to salt spray and electrochemical tests. Electrical resistance measurements performed on hybrid busbars taken from the corrosion testing cabinet at the end of each exposure period allow concluding that the new injection lap riveted hybrid busbars have a better electrical performance over time due to the elimination of fasteners with a higher electrical resistivity than aluminum and copper and to the elimination of the aluminum-steel and copper-steel galvanic pairs. The capability of the injection lap riveted hybrid busbars to withstand shear forces after corrosion testing also revealed to be adequate and like those of the original (uncorroded) hybrid busbars. [ABSTRACT FROM AUTHOR]

Aging aircraft is susceptible to cyclic fatigue cracks around ferrous fasteners in multilayer aluminum wing lap joints, as found on Canadian Military aircraft CP-140 Aurora and CC-130 Hercules. Current methods of crack detection utilize bolt hole eddy current, requiring fastener removal, a time consuming process that also has the potential to result in collateral damage. In this paper, pulsed eddy currents (PECs) are induced in the aluminum wing structure by a probe centered over a ferrous fastener. The response signals are analyzed using a modified principal components analysis (PCA) and cluster analysis to show separation of groups of PCA scores from fasteners with and without notches in the bore hole. The Mahalanobis distance (MD), a cluster analysis method, is used to obtain a relative distance measurement between scores associated with cracks from those without cracks. The MD evaluation provides confidence intervals for detection of cracks, which range in extent from fastener holes from 0.9 to 5.5 mm, and a means of potentially sizing larger (>3 mm) second layer cracks. In this paper, 100% of the cracks in the sample were detectable. The results demonstrate PEC as a viable technique for second layer crack detection with ferrous fasteners present. [ABSTRACT FROM PUBLISHER]

Under long-term temperature loading, long bridges stretch and deform, causing the beam and rail to move relative to each other. This phenomenon could cause a gradual slide of the rail relative to the fastener composite pad and ultimately results in the slipping out of the fastener pad at the end of the ballastless track bridge changes. The slipping out of the fastener composite pad changes the longitudinal resistance of the fastener and causes shock of the train on the rail structure due to direct contact between the rail and the tie, thus inhibiting the normal use of the line. In this paper, a reciprocating tensile test was carried out on a WJ-8 small resistance fastener to explore the breaking process of the fastener composite pad, identify the interaction mechanism of the fastener composite pad under the rail, and ultimately determine the influence of the pad on the longitudinal resistance of the fastener. The results show that the two factors that affect the longitudinal resistance of the fastener under reciprocating loading are the surface roughness and displacement of the fastener composite pad. While the surface roughness of the fastener composite pad is the main influencing factor in the early stage, the displacement of the composite pad has a greater impact on the later stage. The research results of this paper can provide an important reference for the maintenance and repair of ballastless track fasteners on bridges. [ABSTRACT FROM AUTHOR]

Ocean waves provide a promising and abundant renewable energy resource. One reason wave energy technology is still not mature enough for commercialization is the high unit cost of generated electricity. This needs to be improved by a combination of device and associated controller design. A multi-float and multi-mode-motion wave energy converter (M-WEC) enables much higher energy conversion compared with a single-float, single-mode WEC (S-WEC); however, the added complexity in dynamics of a M-WEC makes the corresponding controller design more challenging. While the majority of current WEC control research has been based on the control of S-WECs it has shown that control can significantly improve energy conversion. This paper aims to design a linear non-causal optimal controller for a M-WEC to demonstrate that this improvement also applies to more complex WEC systems. We choose a multi-body attenuator type M-WEC called M4 as a case study for which the desirable feature of predominantly linear dynamics has been demonstrated. This means that a linear controller can be designed based on a linear hydrodynamic model without introducing an intractable computational burden for real-time controller implementation. Numerical results show that the linear non-causal optimal controller can significantly improve the power capture of M4 over a broad range of peak spectral wave periods by $\text{40}{\%}$ to $\text{100}{\%}$. [ABSTRACT FROM AUTHOR]

The electro-mechanical brake booster (EMBB) is a kind of mechatronic actuator, which is developed to suit the brake assist requirement of electric vehicles. In this paper, we report on the design of an EMBB system consisting of a dc motor, a two-state reduction of a gear and ball screw, a servo body, and a reaction disk. Considering the inconvenience of installation and high price of the pedal force sensor, we translate the control problem of brake power assist control to position tracking control. Meanwhile, a nonlinear control method for position tracking is presented to solve the problem of power assist braking, which is formalized as three parts: the steady-state control, feed-forward control based on reference dynamics, and state-dependent feedback control. The benefit of the nonlinear control method is that it offers a concise control law and performs well in engineering implementations. In addition, a second-order filter was designed to do the signal processing and obtain a higher-order derivative. Finally, the bench tests based on rapid control prototyping environment were designed and implemented to verify the performance of the controller. Test results show that both the position tracking performance and response time of the EMBB system performed well. [ABSTRACT FROM AUTHOR]

The performance of distance-based classifiers heavily depends on the underlying distance metric, so it is valuable to learn a suitable metric from the data. To address the problem of multimodality, it is desirable to learn local metrics. In this short paper, we define a new intuitive distance with local metrics and influential regions, and subsequently propose a novel local metric learning algorithm called LMLIR for distance-based classification. Our key intuition is to partition the metric space into influential regions and a background region, and then regulate the effectiveness of each local metric to be within the related influential regions. We learn multiple local metrics and influential regions to reduce the empirical hinge loss, and regularize the parameters on the basis of a resultant learning bound. Encouraging experimental results are obtained from various public and popular data sets. [ABSTRACT FROM AUTHOR]