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Mechanical fastening is widely used in joining metals, particularly in automotive, aerospace, building and construction industries. However, the main concern on mechanical fastening is the issue of corrosion. An effective way to prolong the service life of steel fasteners is to apply protective coatings onto these components. This paper reviews and compares a few common coating deposition techniques, i.e., electroplating, hot-dip galvanizing, ion vapour deposition and mechanical plating, in terms of their characteristics. Compositional and microstructural properties including morphology and porosity, corrosion resistance performance and frictional performance of the coatings formed by each process are discussed in details. Hydrogen embrittlement, a premature failure often occurred on high strength steel fasteners, is also reviewed. The key results of recent studies of various metallic coatings on fasteners are presented to provide a fundamental understanding of the evolving topics, and the research gaps have been identified for further investigation. [ABSTRACT FROM AUTHOR]

The clamping bolts and bolt-holes can be employed to stack the steel laminations in permanent magnet machines. Their influence on the electromagnetic performance is analyzed in this paper, including the electromagnetic torque, open-circuit torque, phase back-EMFs, and circulating current loss. A restraining method of dummy bolt-hole is proposed to achieve both balanced phase back-EMFs and zero circulating currents in bolts. The ratio of bolt-hole edge thickness to bolt-hole radius is optimized to compensate the reduction of stator yoke caused by bolt-holes. Besides, a method of open bolt-hole edge is proposed to restrain the circulating currents. Furthermore, structure analyses are conducted to prove the reliability of the electromagnetic design. The proposed method is verified by experiments on a prototype machine. [ABSTRACT FROM AUTHOR]

The most important components of the internal nut thread inspection process are measuring the pitch and pitch diameter value and comparing these with their respective specifications, as a test nut is considered to be abnormal when its pitch or pitch diameter does not meet specifications. This paper focuses on defects arising when the pitch diameter does not meet its specification. Because conventional contact strategies are not suited to the real-time inspection of internal thread defects, there have been a number of recent attempts to develop noncontact methods for real-time measurement. Some approaches have applied laser triangulation techniques in which reflected light is used to measure the z-axis depth on an object’s surface. Although point lasers have been shown to be highly precise in measuring pitch diameter, the optical architecture involved in these approaches is complicated and, as the laser must be scanned in a pointwise manner to derive cross-sectional measurements, the measurement process is too long to be compatible with real-time defect inspection. In this papere, an image-based method employing a line laser projector was used to develop a real-time image-based nut pitch diameter defect inspection system. The proposed method, which improves upon the conventional, widely used template-matching method for rapid defect detection, was shown to be effective through experimental validation. [ABSTRACT FROM AUTHOR]

Split pins (SPs) play an important role in fixing joint components on catenary support devices (CSDs) of high-speed railway. The occurrence of loose and missing defects of SPs could make the structure of CSDs unstable. In this paper, we present a three-stage automatic defect inspection system for SPs mainly based on an improved deep convolutional neural network (CNN), which is called PVANET++. First, SPs are localized by PVANET++ and the Hough transform & Chan–Vese model, and then, three proposed criteria are applied to detect defects of SPs. In PVANET++, a new anchor mechanism is applied to produce suitable candidate boxes for objects, and multiple hidden layer features are combined to construct discriminative hyperfeatures. The performance of PVANET++ and several recent state-of-the-art deep CNNs is compared in a data set that is collected from a 60-km rail line. The results show that our model is superior to others in accuracy, and has a considerable speed. [ABSTRACT FROM AUTHOR]

Cross-laminated timber (CLT) panels, when used as shear walls or diaphragms, are commonly connected with multiple (n) doweltype fasteners in a row. For such connections, it is frequently observed that the load-carrying capacity of multiple fasteners is less than the sum of the individual fastener capacities, a phenomenon referred to as the group effect. The research presented in this paper investigated the group effect in self-tapping screw (STS) shear connections between CLT panels. Different joint types (surface splines with STS in shear, and half-lap and butt joints with STS in either shear or withdrawal) were evaluated in a total of 175 quasi-static monotonic and reversed cyclic tests, with the number of STS in one row varied between 2 and 32. The results showed that the group effect for the joint capacity (strength) can be expressed as neff = 0.9n for all joints under static loading, where neff is the effective number of fasteners. In case of cyclic loading, a more pronounced group effect was observed that can be expressed as neff = n0.9. These reductions are significantly less conservative than the current Canadian design provisions for lag screws. For the reduction in stiffness and ductility, neff = n0.8 and neff = n0.9 can be used for all joints under static and cyclic loading, respectively. Finally, the capacity, ductility, and stiffness for joints under cyclic loading where the STS acted in withdrawal were on average 10% lower compared with the static values. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) built-up members are formed by connecting several single members by fasteners. This paper presents experimental, numerical and analytical studies on the effect of fastener configurations on the flexural rigidity of built-up sections. In this research, two zinc-coated steel C-sections are connected back-to-back to form a double-web built-up I-section, which is subject to weak-axis bending. A closed-formed expression for the flexural rigidity of built-up sections as a function of fastener stiffness, number and position of fasteners, and section geometry is then derived. This is validated against the tests and finite element modelling, and can be adapted more generally to determine the stiffness and global strength of CFS built-up members in bending. • The study is about how fastener configurations affect the effective flexural rigidity of cold-formed steel built-up sections. • Tested fasteners are screws, bolts and welds. • The effective flexural rigidity is a function of fastener stiffness, number and position of fasteners, and section geometry. • Effective flexural rigidity affects stiffness and strength of built-up members in bending and members subject to buckling. [ABSTRACT FROM AUTHOR]

This paper introduces a new type of reluctance-based magnetic lead screw (RBMLS) that is attractive for many potential applications. The proposed topology presents the implementation of discretized permanent magnets (PMs) and ferromagnetic semi-rings. The proposed RBMLS has PMs in only one of its movable parts, making it suitable for long-stroke applications. The proposed RBMLS is analyzed through the 2-D and 3-D finite-element method in order to test its topology and obtain the force produced per PM volume. Detailed design features are presented for the realization of a prototype. [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]

The paper presents a simulation of the Airbus A350-900 wing-to-fuselage assembly process. The latter is a complex multistage process where the compliant parts are being joined by riveting. The current research analyzes the quality of the temporary fastener arrangement. The fastener arrangement is being checked to ensure that the residual gap between joined parts is small, and the fastener loads closing the gap are calculated. The deviations of the part shape from nominal are modeled via initial gaps. A cloud of initial gaps is generated based on the statistical analysis of the available measurements assuming the stochastic nature of local gap roughness. Through the reduction of the corresponding contact problem to a quadratic programming (QP) problem and the use of efficient QP algorithms together with the task-level parallelism, the mass contact problem solving on refined grids is accomplished. [ABSTRACT FROM AUTHOR]

This paper presents the methodology for the design and control of a high-stiffness fast tool servo (FTS) system for practical application in diamond machining of freeform surfaces. The electromechanical model of the FTS system is established by combining the piezoelectric actuator and the flexure hinge mechanism for the formulation of the control methodology. In order to accommodate the system nonlinearity, cutting force disturbances as well as to realize fast and accurate tracking of designated tool path required for diamond machining of freeform surfaces, a novel adaptive terminal sliding mode (NATS) control strategy capable of online self-tuning of the system gain and reach time related parameters are developed. Stability analysis of the proposed NATS controller is performed. The convergence behavior of tracking error in the presence of model parameter variations and cutting force disturbance is analyzed. Experimental verification was conducted to validate the effectiveness and robustness of the NATS control. By comparing with other related control methods, it shows significantly improved performance. The percentage of tracking error was only 0.1% for the varying trajectories on machining water-drop surface. Taking advantage of the excellent tracking performances of the FTS prototype on a diamond turning machine, various freeform surfaces were successfully produced with high quality. [ABSTRACT FROM AUTHOR]

Accurate classification of Electroencephalogram (EEG) signals plays an important role in diagnoses of different type of mental activities. One of the most important challenges, associated with classification of EEG signals is how to design an efficient classifier consisting of strong generalization capability. Aiming to improve the classification performance, in this paper, we propose a novel multiclass support matrix machine (M-SMM) from the perspective of maximizing the inter-class margins. The objective function is a combination of binary hinge loss that works on C matrices and spectral elastic net penalty as regularization term. This regularization term is a combination of Frobenius and nuclear norm, which promotes structural sparsity and shares similar sparsity patterns across multiple predictors. It also maximizes the inter-class margin that helps to deal with complex high dimensional noisy data. The extensive experiment results supported by theoretical analysis and statistical tests show the effectiveness of the M-SMM for solving the problem of classifying EEG signals associated with motor imagery in brain–computer interface applications. [ABSTRACT FROM AUTHOR]

• An analytical calculation method for displacement and force at the transition. • Comparison on the derived calculation scheme for three different conditions. • Study on effects of the maximum temperature gradient ratio. • Study on effects of the maximum fastener resistance on longitudinal displacement. The rails at the transition between a bridge or subgrade and a tunnel tend to creep longitudinally because of a temperature gradient on the rail, which can cause irregularity in the track. The longitudinal temperature distribution along the rail and the longitudinal resistance of the fasteners are the main influences on rail creep. In this paper, the linear and nonlinear models of longitudinal temperature distribution on rails and the longitudinal resistance of fasteners are tested for their accuracy in predicting rail creep. By researching the rail at the temperature-transition zone, differential equations for the longitudinal displacement and force of the rail are established. To predict the changes that a rail will experience in a temperature-transition zone, expressions for the longitudinal displacement and force are derived from these differential equations. The derived calculation scheme is tested for three conditions: linear models of both rail temperature and longitudinal resistance, linear rail temperature and nonlinear resistance, and nonlinear models of both rail temperature and displacement. The maximum longitudinal rail displacement and the maximum longitudinal additional force in all three conditions are compared to reveal the influence of the maximum temperature force gradient multiple and the maximum fastener resistance on longitudinal displacement. [ABSTRACT FROM AUTHOR]

Based on the unique advantages of fiber Bragg (FBG) in the field of vibration monitoring, a 2-D FBG accelerometer based on multi-axis flexure hinge is proposed. With the adoption of symmetrical multi-axis flexure hinges, the sensing probe has the same sensitivity in two measuring directions. The differential arrangement of the two couple FBGs can eliminate the influence of temperature, and in addition, its sensitivity is twice that of single FBG. The structure and principle of the sensor are explained, and its acceleration sensitivity and resonance frequency are analyzed theoretically in this paper. On this basis, the simulation analysis is carried out and two kinds of sensors for different occasions are made finally. Experimental studies show that the sensors can pick up the vibration signal accurately and have preferably temperature self-compensation effect under the condition form 20 °C to 90 °C. The stable frequency band of the max-sensor is 5 to 170 Hz, the acceleration sensitivity is up to 220 pm/g, the cross-interference in two measuring directions is not exceeding 4%, and the resonant frequency is 279.2 Hz. The min-sensor has a wide flat range from 20 to 600 Hz with an acceleration sensitivity of 40 pm/g. Its cross-interference is less than 3.5%, and the resonant frequency is 814.3 Hz. [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]

Neural networks with rectified linear unit (ReLU) activation functions (a.k.a. ReLU networks) have achieved great empirical success in various domains. Nonetheless, existing results for learning ReLU networks either pose assumptions on the underlying data distribution being, e.g., Gaussian, or require the network size and/or training size to be sufficiently large. In this context, the problem of learning a two-layer ReLU network is approached in a binary classification setting, where the data are linearly separable and a hinge loss criterion is adopted. Leveraging the power of random noise perturbation, this paper presents a novel stochastic gradient descent (SGD) algorithm, which can provably train any single-hidden-layer ReLU network to attain global optimality, despite the presence of infinitely many bad local minima, maxima, and saddle points in general. This result is the first of its kind, requiring no assumptions on the data distribution, training/network size, or initialization. Convergence of the resultant iterative algorithm to a global minimum is analyzed by establishing both an upper bound and a lower bound on the number of non-zero updates to be performed. Moreover, generalization guarantees are developed for ReLU networks trained with the novel SGD leveraging classic compression bounds. These guarantees highlight a key difference (at least in the worst case) between reliably learning a ReLU network as well as a leaky ReLU network in terms of sample complexity. Numerical tests using both synthetic data and real images validate the effectiveness of the algorithm and the practical merits of the theory. [ABSTRACT FROM AUTHOR]

This paper presents a combined experimental and numerical study on bolted L-stub connections under simultaneous bending and axial excitation from a cyclic separating load, which has not been reported in the open literatures. The reduction of the clamping force is found from experiments. Additionally, the thread damage is analysed using an optical microscope, a white light interferometer, a scanning electron microscope (SEM) and an energy dispersive X-ray (EDX). The effects of the eccentricity, the excitation level and the initial clamping force on the reduction of clamping force and the damage of threads are also studied in experiments. It is found from the experimental results that the degrees of the thread damage and self-loosening increase with the increases of the excitation level and the eccentricity, and they decrease with the increasing initial clamping force. A three-dimensional finite element model is created to analyse the contact stress and the relative slip between the threads of the bolt and the nut, and the finite element results agree with the experimental measurements. • This work is the first attempt to study the self-loosening of a bolted joint under simultaneous bending and axial excitation from a cyclic separating load. • The wear mechanisms of the thread surfaces were investigated. • Experimental observations were further explained using finite element method. [ABSTRACT FROM AUTHOR]

In this paper, we present KULEX-hand, a novel underactuated hand exoskeleton for grasping power assistance for patients having a partially paralyzed hand or the elderly with weakened muscle strength. This mechanism consists of an underactuated finger for grasp motion generation, a spherical four-bar linkage for power transmission, and a passive thumb link with a flexure hinge structure. Based on the natural closing motion of the human index finger, the motion generation linkage was synthesized as a planar five-bar in which two input links were coupled with a four-bar linkage. Therefore, after contact occurs on the proximal link, the synthesized linkage can mimic the grasping motion of the human middle and distal phalanges. The kinetoelastic relation of the underactuated finger was derived using the theory of screws. Based on this relation, guidelines were proposed for selecting the springs for achieving a stable pinch grasp. A prototype was designed, and the naturalness of motion was evaluated from an experiment with five subjects. [ABSTRACT FROM AUTHOR]

This paper introduces a contact resistance model of bolt structures based on virtual material method. The main idea of the model is to interpose a virtual layer between the overlapped bus bar and define properties including equivalent resistivity and equivalent modulus of elasticity to describe the dynamic characteristics of the distributed contact resistance. The determining method of these properties is introduced, and the validity of the model is demonstrated by comparing the calculated contact resistance with the measured results. The model is further applied to the coupled electromagnetic–stress–thermal finite-element calculation to analyze the thermal stability of the bolt structure. The temperature rise process inside the bolt structure is studied, and the strengthening effect of the electrodynamic force on the thermal field is revealed. Besides, the influences of contact loosening and oxidation are also researched with the method. [ABSTRACT FROM AUTHOR]

Abstract Pull-through failure of steel roof batten to rafter connections is one of the critical failures observed in cold-formed steel roofs during tropical cyclones. Although design equations are available for steel roof battens subject to static pull-through failures, no suitable design equations are available for fatigue pull-through failures. Currently, a Low-High-Low (LHL) cyclic test method based on expensive and time consuming large scale prototype tests is being used to design roof battens for fatigue pull-through failures. Therefore, this research study proposes suitable design equations based on both linear and nonlinear damage models to determine the fatigue life and capacity of steel roof battens by understanding the fatigue behaviour of steel roof battens subject to variable amplitude cyclic wind suction loading. This was achieved through a series of multi-level cyclic tests, including LHL cyclic tests, conducted on roof battens made of different steel grades and thicknesses and fastened with different screw fasteners. This paper presents the details of the experimental study and its results, and proposes suitable fatigue pull-through design equations based on linear and nonlinear fatigue damage models. Highlights • Investigated the fatigue pull-through failure of roof battens under variable amplitude cyclic loading. • Examined the use of linear damage model for the fatigue pull-through failure of roof battens. • Investigated the sequence effect using multi-level cyclic tests. • Proposed a nonlinear damage model for the fatigue pull-through capacity by including sequence effect. • Investigated the suitability of linear and nonlinear damage models to replace the LHL cyclic test. [ABSTRACT FROM AUTHOR]

A novel two-dimensional (2-D) linear piezoelectric stepping platform using two parallel longitudinal-bending hybrid piezoelectric actuators is proposed in this paper. The proposed platform is moved in theX-direction by combing the vertical and horizontal bending motions of the parallel actuators, whereas the movement in theY-direction is realized by the vertical bending and longitudinal hybrid motions. The platform is designed and its operating principles in two orthogonal directions are described. The finite-element method simulations are performed to verify the operating principles of the 2-D platform. Two piezoelectric actuators are fabricated and a prototype of the platform is assembled. The measured results of mechanical output performance indicate that the velocities of the platform are 101.7 and 124.2 μm/s inX- andY-directions when the voltage and frequency are ${\text{400}\,\text{V}}_{{\text{p-p}}}$ and 5 Hz, respectively, which verifies the feasibility of the proposed mechanism for the 2-D stepping platform. [ABSTRACT FROM AUTHOR]

Abstract The railway track fasteners play a critical role in fixing the track on the ballast bed. Achieving full automation of the fastener defect detection is significant in terms of ensuring track safety, and reducing maintains cost. In this paper, innovative and intelligent methods using image processing technologies and deep learning networks are proposed. In the first part, the traditional fastener positioning method based on image processing is reconsidered. In addition, a novel fastener defect detection and identification method using Dense-SIFT features is proposed which can achieve a better performance than the methods available in the literature. In the second part, VGG16 is trained for fastener defect detection and recognition. The result demonstrates that it is possible to carry out the defect detection of fasteners with CNN. Finally, Faster R-CNN is used for fastener defect detection to advance detection rate and efficiency. The fastener positioning and recognition can be carried out simultaneously. The time for the defect detection and classification is only one-tenth of the other methods mentioned above. Highlights • The Dense-SIFT, spatial pyramid decomposition and BOVW techniques are applied to the classification and this method achieves classification accuracy of 99.26%. • The DCNN method uses only one network for fastener defects detection and achieves a sound classification accuracy of 97.14%. • Faster R-CNN based method realizes the positioning and classification of the fasteners simultaneously and the time spent by Faster R-CNN is only about 10% of the time spent by the other methods. [ABSTRACT FROM AUTHOR]

Continuous gesture recognition aims at recognizing the ongoing gestures from continuous gesture sequences and is more meaningful for the scenarios, where the start and end frames of each gesture instance are generally unknown in practical applications. This paper presents an effective deep architecture for continuous gesture recognition. First, continuous gesture sequences are segmented into isolated gesture instances using the proposed temporal dilated Res3D network. A balanced squared hinge loss function is proposed to deal with the imbalance between boundaries and nonboundaries. Temporal dilation can preserve the temporal information for the dense detection of the boundaries at fine granularity, and the large temporal receptive field makes the segmentation results more reasonable and effective. Then, the recognition network is constructed based on the 3-D convolutional neural network (3DCNN), the convolutional long-short-term-memory network (ConvLSTM), and the 2-D convolutional neural network (2DCNN) for isolated gesture recognition. The “3DCNN-ConvLSTM-2DCNN” architecture is more effective to learn long-term and deep spatiotemporal features. The proposed segmentation and recognition networks obtain the Jaccard index of 0.7163 on the Chalearn LAP ConGD dataset, which is 0.106 higher than the winner of 2017 ChaLearn LAP Large-Scale Continuous Gesture Recognition Challenge. [ABSTRACT FROM AUTHOR]

This paper presents a novel piezoelectrically actuated dual-axis micromanipulator with an asymmetric compliant structure. The mechanical design of the micromanipulator is first presented. A novel guiding bridge-type mechanism was proposed and utilized in the left part of the micromanipulator to improve the dynamic performance of the micromanipulator. The analytical model has been established based on the pseudorigid-body model and matrix-based compliance modeling method. The kinematic and the precision of the micromanipulator have been analyzed, and the input and output couplings have been investigated. The prototype of the micromanipulator has been fabricated by wire electrodischarge machining. Then, open-loop experimental tests have been performed. The experimental results match well with the analytical calculation, and the amplification ratios are 11.12 and 4.64 for the left part and right part, respectively. Proportional-integral controller has been used to regulate the output displacement and grasping force, and a series of closed-loop experiments have been conducted to investigate the performance of the micromanipulator. The results show that the position resolution for both the right and left parts is 0.15 μm, and the force resolution is 4 mN. [ABSTRACT FROM AUTHOR]

Robotic ankle prostheses can imitate the biomechanical function of intact legs at the cost of a larger weight and size compared to conventional passive prostheses. Unfortunately, increased weight and size negatively affect comfort and socket stability, ultimately limiting their clinical viability. Alternatively, a nonbackdrivable transmission system can be used to actively regulate the ankle position during nonweight bearing activities only. This semiactive design can be made smaller and lighter as a result of the lower actuation power requirements. However, the transmission system must withstand high loads during stance and standing. Thus, available semiactive prostheses are still significantly heavier and have a larger build height than passive ankle prostheses. In this paper, we present the design, development, and validation of a semiactive ankle prosthesis with a nonbackdrivable cam-follower mechanism designed to lower the load on moving components and align with the foot longitudinally as necessary to reduce the prosthesis weight and size. The proposed ankle mechanism is ∼50% shorter, has ∼40% wider range of motion (ROM), and is estimated to be ∼27% lighter than available semiactive prostheses. Experiments with a transtibial subject show that the semiactive prosthesis can increase foot clearance up to 142% and reduce the load on the residual limb as low as 32% compared to passive prostheses. [ABSTRACT FROM AUTHOR]

A typical aircraft panel is the assembly consisting of a multitude of thin and lightweight compliant parts. In panel assembly process, part-to-part locating scheme has been widely adopted in order to reduce fixtures. By this locating scheme, a part is located onto the pre-fixed part/subassembly by determinant assembly (DA) holes, and temporary fasteners (e.g., spring pin) are used for joining these DA hole-hole pairs. The temporary fasteners can fasten DA hole-hole pairs in the axial and radial directions of DA holes. The fastening in the radial directions is realized by the expansion of temporary fasteners. Although the usage of temporary fasteners helps reduce the positional differences between hole-hole pairs, their clamping forces thereby may lead to elastic deformation of compliant parts/subassemblies. Limited research has been conducted on such elastic deformation produced by temporary fastener and its influence on assembly dimensional quality. This paper proposes a novel rigid-compliant variation analysis method for aircraft panel assembly, incorporating the deformation in part-to-part locating process. Based on the kinematic theory and linear elasticity deformation assumption, the variation propagation through the locating process, as well as the entire assembly process of an aircraft panel, is formulated. Then, the statistical variation analysis is performed with Monte Carlo (MC) simulation. Finally, the proposed method is validated by a case study. The result shows the deformation in the part-to-part locating process significantly impacts the assembly variations, and our method can provide a more accurate and reliable prediction. [ABSTRACT FROM AUTHOR]

Heavy-haul railway has been developed rapidly in many countries in the world due to its great social and economic benefits. One of the key technologies for heavy-haul railway is the reduction of vibration on the track structures and its surrounding due to impact load induced by the train in service. The vibration behaviors of two kinds of low-vibration track (LVT) systems for heavy-haul railway are investigated in this paper. Firstly, two indoor full-scale low-vibration track models (new LVT and traditional LVT), which include rail, fastener, bearing block, rubber boot, track slab, and foundation base, were constructed according to design drawings. Secondly, the vibration responses of the different track components under the impact excitation of a dropping wheelset were measured. Thirdly, the time-domain characteristics of each track component of the two LVTs were compared by the acquired vibration time-history curves. Finally, the frequency-domain distribution was analyzed, and the vibration reduction performance was evaluated by the comprehensive time-frequency analysis results. The results show the new LVT has lower vibration acceleration, shorter duration of vibration period, lower vibration frequency of track components, and most importantly an obvious vibration reduction effect on the ground. The research results are useful to further optimize the design of LVT to reduce the vibration under train impact load. [ABSTRACT FROM AUTHOR]

Abstract Environmentally induced degradation is a serious issue governing the use of titanium alloy fasteners for marine applications. The workhorse alloy Ti6Al4V which has been the most used titanium alloy till date as fastener material has its limitations and search has been on for improved titanium-based materials. This paper deals with researches aimed at evaluating the metastable beta titanium alloy Ti15V3Cr3Al3Sn (Ti15-3) in solution annealed condition as a fastener material for medium strength applications. A variety of tests was carried out to rate the resistance of the alloy in this condition to seawater environments slow strain rate testing (SSRT), crevice corrosion testing, potentiodynamic polarization studies, and immersion testing. Limited SSRT was also done on Ti6Al4V for the sake of comparison. Analysis of test results shows that solution annealed Ti15-3 offers itself as a good candidate material for medium strength fastener applications in marine environments. Highlights • Slow strain rate testing indicates that alloy Ti15-3 shows excellent resistance to sea environment. • The alloy Ti15-3 in solution annealed condition shows excellent resistance to crevice corrosion. • Lower corrosion rates of Ti15-3 in 3.5% NaCl compared to Ti6Al4V. [ABSTRACT FROM AUTHOR]

This paper reports on a unique tactile microprobe based on a parallelogram kinematic made from monocrystalline silicon. This kinematic, made out of an orthogonal cascade assembly of three identical parallelograms, provides an isotropic behavior to the microprobe. Each parallelogram deflects in only one direction thanks to thin elastic silicon membrane hinges and their displacements are recognized using piezoresistors integrated into these hinges. Wide deflection ranges, isotropic behavior, and low mechanical stiffness of the new microprobe, as predicted by simulations, could be verified in experiments. The fabrication, the assembly, and the contacting of the first microprobe prototype was optimized to allow very compact integration into a Ø11 mm housing. This make it suitable for metrology research laboratories and industries equipped with conventional coordinate measurement machines and even for a variety of other 3-D force/displacement measurements. [2018-0157] [ABSTRACT FROM AUTHOR]

This paper studies the stability control of a target towed by a space-tug via a tether in orbital transfer. The attitude of the towed target is controlled by thrust regulation at the tug with the consideration of the coupling effect between the attitudes of the tug and towed target and the motion of the flexible and elastic tether. A model-based control scheme is proposed, where the tug and towed target are assumed as rigid bodies and the tether is approximated as a series of extensible but incompressible rods connected by spherical hinges. The governing equations of motion of the coupled rigid–flexible multibody system are derived based on the recursive dynamics algorithm. The attitude motion of the tug with the presence of tether tension disturbance is controlled by a simple proportional–derivative torque controller. The attitude motion of the towed target and the elongation oscillation of the tether are stabilized simultaneously via the tether tension by regulating the thrust at the tug. The thrust control is achieved by first designing an optimal trajectory considering the system constraints based on a reference model, and then the trajectory is tracked by a robust global terminal sliding-mode controller with the consideration of thrust saturation and tether slackness avoidance. Finally, numerical simulation is carried out to demonstrate the effectiveness of the proposed attitude control law based on the thrust regulation. [ABSTRACT FROM AUTHOR]

Abstract: Dowel-type fastener connections perpendicular to grain may fail in either a ductile or a brittle fashion. Whether the failure mechanism should be classified as ductile, depends on the definition of ductility utilized. Generally, the load–slip response is considered as a means of ductility quantification. In this respect, the elastic potential energy is calculated (being the area underneath the load–slip response) or the ratio of the ultimate slip and the slip at the onset of yielding is used, amongst others. Another approach relates to the European Yield Model which is commonly adopted in design standards to calculate the load-bearing capacity of dowel-type fastener connections. In this respect, ductility may be considered to be associated with plastic deformation of the steel fasteners solely since the deformation ability of connections with dowel-type fasteners at yield is much larger compared to situations with non-yielding fasteners. In the case of connections with rigid dowel-type fasteners, it therefore may be suggested that less ductility is exhibited although it is recognized that timber in compression perpendicular to grain exhibits plastic capabilities as well. Whether these connections behave either brittle or ductile is related to the spacing requirements as well. In this paper, first an overview of potential fracture and failure mechanisms of dowel-type fastener connections is provided. Experimental results of a variety of connections and corresponding failure mechanisms are presented. Based on mechanical models to predict the load-bearing capacity, classification of these connections in terms of ductility is provided, and the governing parameters involved are distinguished. This paper does not intend to provide a quantification procedure of ductility. Yet, an extensive overview of failure mechanisms and an analytical analysis of parameters involved are given providing expressions to calculate the failure mechanism being governing. [Copyright &y& Elsevier]

This paper presents structure thermal mechanics analysis of spindle disk assembly used in spinning magnetic data storage hard disk drives (HDDs). With the view toward understanding the underlying physics and to minimize the corresponding repeatable run-out (RRO) of track following position error signal (PES) in high track per inch (TPI) magnetic disk drives, analytical representation of thermal expansion mismatch between disk and spindle hub structure formulated in form of operators and finite element analyses (FEA) are employed in this paper. Parameter studies with analyses taken at different operational temperatures suggest that RRO can be minimized significantly when location of spindle notch, which is can be the internal feature used to position bearings to the hub structure, is properly located. RRO harmonics resulted from the thermal expansion mismatch and structure misalignments having ramping characteristics from disk outer diameter to inner diameter are studied and concluded with simple algebraic expression related to number of fasteners used in disk-spindle assembly. [ABSTRACT FROM AUTHOR]

The bolted or riveted lap joint is a common fastening technology for structural members. When a joint becomes worn the joined members can move in a nonlinear fashion relative to each other as well as impact each other and the lap joint plates. For low frequency bending modes, the system can experience sticking or frictional sliding motion at a finite number of contact points in the joint. The work presented herein is the fifth paper in a series of papers used for the development and verification of a hybrid parameter modeling methodology applied to the analysis of damaged structures. By utilizing an experimental test bed suitable for providing excitations up to 60 Hz, this research further validates a low order frictional contact impact mathematical model of a typical loose bolted joint that was developed and partially validated the aforementioned companion papers published in this journal. For each of the different contact and motion regimes experienced by the jointed beam, experimental estimations of the damping and other parameters were determined. Contact patches, strain gauges, a force transducer, and accelerometers were used to measure the response of the experimental test bed model of a bolted joint cantilever beam. The simulation results were then compared to the experimental results using spectral and time domain techniques. Animations of the simulated joint motion were compared to a high-speed video of the experimental joint motion. The results indicate good correlation between the model and reality, thus the results presented in this paper provide supporting evidence of the efficacy of the underlying low order modeling techniques. [ABSTRACT FROM PUBLISHER]

Single-sided punched metal plate fasteners have been used in construction industry for a few decades. However, its double-sided version is relatively new and is increasingly attracting more users due to its advantages on fire resistance and aesthetics. Owing to complex nature of such fastener, limited research has been undertaken up to date. In this paper, a finite element method-based inverse modelling technique was developed for optimization analyses of a prototype double-sided fastener. The non-unique nature of inverse model solutions makes assessment of model sensitivity to input material properties imperatively. This paper uses validated numerical models for sensitivity analysis of joint modelling output. Joint stiffness is most sensitive to wood elastic moduli. Ultimate strength is significantly influenced by steel yield strength and wood embedding strength and shear strength. The coefficient of friction, steel yield strength, wood shear and embedding strengths have significant effects on joint slip. [ABSTRACT FROM AUTHOR]

This paper presents a lightweight (328 g) anthropomorphic robot hand that can exert a large grasping force. We propose a mechanism combining flexion drives and a force-magnification drive for a cable-driven multifingered robot hand. The flexion drive consisting of a feed screw enables quick finger motion, and the force-magnification drive, consisting of an eccentric cam, a bearing, and a pulley, enables a firm grasp. This paper also proposes a 3-D linkage for the thumb. This linkage consists of four links and is driven by a feed screw. It can oppose to a large force exerted by the force-magnification drive. These mechanisms are compact enough to be installed in the developed lightweight hand. We experimentally verify that the maximum fingertip force of the hand exceeds 20 N and that the thumb can hold a large force of 100 N. The time to fully close the hand using the flexion drives is 0.47 s. After the fingers make contact with an object, the time to achieve a firm grasp using the grasp-magnification drive is approximately 1 s. [ABSTRACT FROM PUBLISHER]

Abstract: Embedding strength is recognized as a very important property in any dowel type timber joints since it affects bearing performance, load carrying capacity and failure mode of the joint. In this paper, using an inverse modelling technique effective flat nail embedding strengths of double-sided nail plate joints were predicted based on single-tooth 3-D finite element models. In those models, timber was treated as an orthotropic elasto-perfect plastic material, and steel nail as a rigid body. The predicted embedding strengths were compared with experimental ones and good correlation was obtained. Using the predicted embedding strength, the overall joint behaviour was simulated and validated against the corresponding experimental results. This paper presents a new approach to obtain embedding strength of double-sided nail plate joints. [ABSTRACT FROM AUTHOR]

This paper reports on the behavior of simply supported (I-shaped cross section) steel beams prestressed by tendons. It is well known that this typology of beams has successfully been used mainly in the past. Prestressed steel beams are lighter than traditional ones that have the same length and vertical load capacity; this aspect could make them economically advantageous and a viable solution in many practical situations. This paper analyzes prestressed steel beams having a medium span ranging from 35 to 45 m and which are to be used as roof structural elements. This study focuses on two parameters that are considered two of the fundamental items for the design: the number of deviators and the value of the prestressing force. This study has been carried out with nonlinear finite-element analyses that take into account both mechanical and geometrical nonlinearities. In particular, the behavior of these beams has been investigated up to failure during tensioning and during loading (after tensioning). The effect on the structural response of bracing, which can be only at the top flange of the beams or at the top and bottom flanges of the beams, also has been considered. [ABSTRACT FROM AUTHOR]

The estimation of the frictional and clamping forces is one of the key issues in the design and implementation of the electromechanical brake (EMB) system. In this paper, a clamping-force control algorithm is presented along with a consideration of the frictional characteristics and the estimation of the clamping force for a planetary reduction gear-type EMB. The frictional model is developed by including the frictional effect of the motor, the planetary gear, and the screw thread. Since the clamping-force estimation requires the distance of the contact gap between the pad and the disk, an initial gap-distance control algorithm that uses the gradient change of the motor torque is proposed. This paper is concluded with a discussion of the performance of the control algorithm by comparing the simulation results with the experimental results. [ABSTRACT FROM PUBLISHER]

The article presents information on a research paper which evaluates the effectiveness of locking or staking of fasteners with epoxy material systems to avoid loss of preload in aerospace environments. The paper uses a quantitative experimental method for evaluating the use of epoxy material systems, Epon 828 epoxy and 3M Scotch-Weld Epoxy 2216, under varying dynamic and thermal loads. The specific design parameters are examined with the help of a statistical design of experiments. The results reveal that epoxy application can provide satisfactory fastener locking and Epon 828 epoxy is better than 3M Scotch-Weld Epoxy 2216.

This paper presents a review of the design provisions for screw-fastened cold-formed steel connections in the United States, including criteria for testing and evaluating the strength of screw fasteners. In addition, the paper examines the relationship between the connected elements/components computed connection strength and the strength of the connector (screws). Fastener strength test data from three independent manufacturers is presented and it is shown that as the thickness or yield strength of the connected elements/components is increased, the ratio of the fastener strength to the bearing/tilting strength decreases to values less than one-half in some cases. Analysis of the test data showed that even when the 2001 North American Specification (NASPEC) for the Design of Cold-Formed Steel Structural Members statistical requirements for distribution of the test data are met, the computed safety and resistance factors can exceed the recommended limits in Section E4 of the 2001 NASPEC. On this basis, it is recommended that the current language in the 2001 NASPEC be revised to specify, if necessary, limits on manufacturer computed safety and resistance factors. Finally, it is recommended that fastener tilt during screw shear strength tests be eliminated to facilitate an accurate evaluation of the shear strength of a fastener. [ABSTRACT FROM AUTHOR]

Roof wind design consist of three parts: determination of wind loads, evaluation of wind uplift resistance and correlating the resistance with the design load such that the resistance is higher than the load requirement. Wind uplift resistance of a system with its respective components is evaluated in laboratory testing. This paper presents a novel approach to estimate wind uplift resistance when components are substituted during field application. Wind dynamics, on a mechanically attached single-ply roofing assembly, lift the membrane and cause fluttering, introducing stresses at the attachment locations. In such assemblies, the fastener–deck interface is a critical design factor. First, by taking steel deck as a component this paper systematically characterizes the various steel decks that are commonly used in low slope application. Second component, namely the fasteners and its engagement strength with deck have been quantified for variations of its design, size and sources. Based on this component characterization, fastener pullout resistance (FPR) is identified as a verification factor for system wind resistance estimation. When variations occur in the fastener–deck interface between the proposed and the existing configurations, the present research through case studies has proved that: “as long as the FPR of the proposed configuration is higher than the existing configuration then wind uplift ratings can be maintained”. This is valid as long as both the configurations have all the remaining roofing components similar with comparable layout. Based on this verification, the study recommends that the testing lab should report the FPR along with the wind uplift resistance such that FPR can be used as a verification factor to accept design/field alternatives. [Copyright &y& Elsevier]

Abstract: A mechanically attached roof system has flexible membranes that are exposed to environmental elements to achieve the waterproofing function. Wind induced loads can lift the roof membrane between attachment locations and cause fluttering. The membrane under tension induced by wind forces transfers stresses through fasteners at the attachment locations. By characterizing the membrane deformation with its slope and using a force-vector diagram, one can predict the critical forces on fasteners. This paper presents the use of a three-dimensional finite element (3D-FE) model for predicting membrane deformation. To validate the model, a series of benchmark experiments have been performed at the Dynamic Roofing Facility of the National Research Council of Canada. The experimental data are also used to evaluate the validity of a mechanical model. From this comparative exercise between the existing model and the newly developed one, the paper offers the designer the limitations at which the simplified mechanical model can be used. [Copyright &y& Elsevier]

This paper focuses on bra damage, specifically damage observed in hook and eye fasteners that are generally located at the backstraps of bras. We describe bra design including the method by which hook and eye fasteners are generally constructed. We assess bra damage in two situations where the damage observed was unexpected given the case scenarios. These were: (i) the complainant of an alleged rape attributed damage to her bra hooks to force during a struggle and (ii) the complainant had earlier manipulated her bra hooks in an incident not related to her complaint. Steriomicroscopy and reconstruction experimentation were necessarily used to assess the bra damage. A systematic approach to damage analysis was employed by the forensic practitioners to correctly identify damage as being a result of mechanical manipulation and therefore as falsified. This paper suggests that more examples of falsified damage should be documented. [ABSTRACT FROM AUTHOR]

Wind dynamics on a mechanically attached single-ply roofing assembly can lift the membrane and cause fluttering, introducing stresses at the attachment locations. To identify a component in a system that has the weakest resistance against wind uplift forces, a dynamic evaluation method is beneficial. Over the past 10 years, a number of mechanically attached systems were constructed and exposed to simulated dynamic wind uplift forces using the Dynamic Roofing Facility at the National Research Council of Canada. This paper presents data from this ongoing investigation that will help system designers to maximize wind uplift ratings by choosing the appropriate roof components at the early design stage or by replacing/adding components during reroofing to improve uplift resistance. By diagnosing roof system failures, one can identify the weakest link and select design alternatives that can improve the wind resistance. Through a case study, this paper concludes with a procedure for system optimization. [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]

Purpose - This paper aims to highlight the importance of the design for disassembly (DFD) concept and to consider the key DFD principles. Design/methodology/approach - This paper first considers the motivations for applying DFD. It then identifies and discusses the key DFD principles. Findings - This paper shows that legislation and consumer pressure are driving product recycling and that DFD is a critical enabling technology. It shows that a series of simple design rules concerning product architecture, materials and fasteners can be used to implement DFD. It highlights the benefits arising from this strategy which include compliance with legislation and reduced component counts and material inventories. Originality/value - This paper provides an insight into the motivations behind the use of DFD and describes the techniques used in its implementation. [ABSTRACT FROM AUTHOR]

STUDY DESIGN.: Focus paper. OBJECTIVE.: To evaluate the current evidence-based medicine (EBM) literature in the use of pedicle screw constructs in patients with adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND.: EBM has evolved over the past 20 years to provide a framework for the evaluation of therapy and the application of that assessment to a particular patient or a disease. Application of EBM analysis to spinal instrumentation, and specifically to pedicle screw constructs, is challenging. METHODS.: Cochrane database, Ovid Medline, and PubMed were searched using the terms “pedicle screws” and “adolescent idiopathic scoliosis.” The reference list of the major papers by authors Lenke, Suk, and Kim were hand searched. Relevant articles were retained if they described a pedicle screw construct to correct AIS or compared pedicle screw constructs with another technique. Articles that did not have patients with adolescent idiopathic scoliosis in their subject groups or did not use pedicle screws as a part of their deformity correction were excluded from the study. RESULTS.: Based on the search strategy described above, 40 articles met the inclusion criteria and were selected for review in this manuscript. Of these, 32 studies are retrospective reviews including 2 studies that do not define their data collection technique. Six studies have a prospective study design, 1 is a case report, and 1 is a cadaveric study. CONCLUSION.: In the absence of evidence from randomized trials, surgeons must rely on the best available information to guide patient management decisions. Although there have been many publications on the topic of all pedicle screw constructs in AIS, evidence regarding the advantage of all pedicle screw constructs remain limited to case series, biomechanical studies, and expert opinions. [ABSTRACT FROM AUTHOR]

Abstract: The analytical model for reinforced concrete beams strengthened using mechanically-fastened fiber reinforced polymer (MF-FRP) pultruded strips is discussed in this paper. In this method, FRP strips, reinforced with a combination of carbon and E-glass unidirectional fibers and continuous strand mats, are fastened to the concrete with steel powder-actuated (PA) fasteners and expansion anchors (EA). The model predicts the ultimate strength and failure modes of MF-FRP strengthened beams and was developed based on results of tests on over 75 RC beams of many different sizes using the MF-FRP method, that have been conducted over the last five years. These tests have explored numerous different failure modes and factors affecting the behavior of MF-FRP strengthened beams. The analytical model can be used to proportion the strengthening system for an RC beam so as to cause the beam to fail in a unique ductile failure mode. This procedure was used to proportion strengthening systems for large-scale beams (7.3m long by 51cm×51cm) that were used to verify the analytical procedure. The strengthened RC beams were designed to fail in a ductile manner. In the test results presented in this paper, the strengthened beams showed increases in yield and ultimate moments of up to 25% and 58%, respectively over an unstrengthened beam. All strengthened beams failed, as intended, in a ductile manner with the ultimate failure mode due to concrete compression failure at large deflections with the FRP strip still firmly attached. Comparisons between the analytical predictions and the experimental results show good agreement. [Copyright &y& Elsevier]

This paper evaluates the effect that uncertainties in measurements of time, weight, and surface area have on the determination of the corrosion rate of metal fasteners in contact with wood. Three different types of nails were driven into alkaline copper quaternary (ACQ)-treated wood and exposed to 26.7°C (80°C) at 100 % relative humidity environment for up to 1 year. It was observed that uncertainties in measurement of corrosion rate of less than 5 % could be obtained in 6 months of testing. This paper gives a description of the methods used as well as recommendations for future corrosion exposure tests in wood. [ABSTRACT FROM AUTHOR]

The floor joists of cold-formed steel (CFS) structures often require large web openings. Reinforcement of such openings may mitigate the detrimental effects of such web openings. This paper is based on an experimental investigation that considered 203 mm deep (base thickness 1.89 mm) galvanized, lipped channel sections with circular, square, and rectangular openings and two associated reinforcement schemes (screw fastening of 31.8 mm × 1.1 mm thick bridging channel). Since the focus of this investigation was on the flexural strength of such joists, the test specimens were simply supported and were subjected to two equal point loads at equal distance from the supports. Two lipped channel sections were set face-to-face to form the test specimen assembly. Based on 11 sets of three identical flexural tests, it was determined that (i) the tension zones of the web with a large opening need not be reinforced, (ii) closely spaced screw fastening of reinforcements (bridging channel) is essential, and (iii) the reinforcements need to be fastened as close as possible to the compression edges of the opening to minimize local buckling of these edges. This paper demonstrates that it is possible to establish cost-effective reinforcement schemes for CFS sections with large web openings. [ABSTRACT FROM AUTHOR]

Numerical model of the wood-framed with sheathing structure and selected results of experimental tests are presented in the paper. Wall and floor diaphragms as the three-dimensional composite structure are modelled applying plane shell elements representing framing and sheathing and beam element describing the fasteners. Experimental tests were conducted on typically disposed the wood-framed wall and floor diaphragms in residential housing in Poland. Associated tests of materials and connections and their results are also included in the paper. Non-linear behaviour of fasteners is examined in the numerical model. Results obtained from model and experiments are coincident. [ABSTRACT FROM AUTHOR]