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A raised crossing (RC), as an alternate to the current form of level crossings to minimise risks of wheel-rail contact failure under frontal collision of trains onto stuck trucks, has been recently formulated by the authors (Engineering Failure Analysis, 80 (2017) 403–415) to mitigate the severity of accidents at road-rail crossings. The aim of the present paper is to assess the effectiveness of the profile of the RC to minimise the risk of speeding through and minimise the peak vertical acceleration of the passing road vehicle below the threshold level for discomfort and safety of its occupants. For this purpose, a simplified two-dimensional multibody dynamic simulation modelling method has been formulated and validated using a detailed three-dimensional industry standard model. The validated model has then been used to optimise the geometric profile of the RC by minimising the peak vertical accelerations of the occupants below the safety threshold of 0.7 g. It is shown that the optimised profile of the RC increases the peak acceleration with the increase in speed of travel of the road vehicles whilst the LC does the opposite. This finding confirms that the RC has the potential to reduce the risk of speeding, which is vital to the safety of the train and road vehicles at rail – road crossings.

We characterize the mechanical recovery of compliant silicone gels following adhesive contact failure. We establish broad, stable adhesive contacts between rigid microspheres and soft gels, then stretch the gels to large deformations by pulling quasi-statically on the contact. Eventually, the adhesive contact begins to fail, and ultimately slides to a final contact point on the bottom of the sphere. Immediately after detachment, the gel recoils quickly with a self-similar surface profile that evolves as a power law in time, suggesting that the adhesive detachment point is singular. The singular dynamics we observe are consistent with a relaxation process driven by surface stress and slowed by viscous flow through the porous, elastic network of the gel. Our results emphasize the importance of accounting for both the liquid and solid phases of gels in understanding their mechanics, especially under extreme deformation.

To effectively predict the life of high voltage dc power relay, the authors design the structure of the relay to extending its life. The contact failure mechanism of relay products is analyzed by observing the appearance of several contact failures. The electromagnetic-thermal field coupling model is established and the state of heat flow and distribution of temperature increase between electrical and thermal coupling contacts are analyzed through simulations and experiments. An adaptive neural network control system is established to conduct sample training, obtain the best stiffness coefficient of the main spring, and optimize the design of the main spring structure composed of composite springs. The action voltage, release voltage, contact resistance, contact pressure, action time, and release time as characteristic parameters, and the relative error, correlation degree, variance ratio, and small error probability of each characteristic parameter, are calculated. The precision grade index of contact resistance and action time is defined as level 1. The two characteristic parameters are selected as the prediction variables to establish the life-prediction model based on gray theory. The relative error between the predicted and test life is 5.31%–5.6%, indicating that the life-prediction model has high accuracy. The test results show that the combined main spring structure can extend the life of a relay by 18.15%.

Fretting wear is a common cause of failure of an electrical contact (EC). In this study, we analyzed in detail the failure of EC induced especially by sliding using the representative electrical terminals. Furthermore, combining the friction energy dissipation theory, we proposed a prediction model to evaluate the electrical connector endurance (ECE) based on the contact stress and geometrical changes during the wear process obtained from a numerical model. The study helps establish that the friction energy dissipation theory is a powerful tool to analyze a contact failure due to wear. The proposed model proves to be effective in predicting the ECE for all considered cases such as micro-slip amplitude, contact force, overturning angle, superficial layer thickness, and friction/wear coefficients.

In this study, we investigated the cause of the contact failure phenomenon of an oil temperature sensor whose signal error occurred intermittently as the vehicle in which it was installed was driving. The electrical contact failed sensor was disassembled and the contact surfaces observed with a scanning electron microscope (SEM). In this present oil temperature sensor, the difference in the thermal expansion coefficient of the male-female terminal and vibration during driving which arose when the vehicle was driven caused fretting corrosion at the contact area. The fretting corrosion caused an intermittent signal error. It is judged that the lead wire of the flexible thin plate is structurally vulnerable to vibration during driving, which further causes fretting of the contact point. Therefore, it is necessary to design an additional structural supplement to fix the flexible terminal of the sensor system.

Derailments of trains often occur due to the wheel-rail contact failure caused by the impact of the trains with road vehicles at road-rail crossings. Frontal collisions of passenger trains onto stuck road vehicles occur frequently at such road-rail crossings even where active warning systems are installed. Such collisions are often fatal and cause significant damages to vehicles and the infrastructure especially when they incur derailments. Innovations in passive railway infrastructure designs for mitigating the severity of collision induced derailments are rare. This paper presents a formulation for a passive road-rail crossing involving stiffened edges of the raised road pavement to minimise the risk of failure of wheel–rail contact using a nonlinear three-dimensional multibody dynamics model. Severe derailment scenarios of trains passing through the passive and normal road-rail crossings have been analysed and presented. The innovative design of the road-rail crossing with passive track structure presented in the paper is shown to reduce the failure of the wheel-rail contact and hence the train-truck frontal collision derailment potential.

Usually, when electrical connectors operate in vibration environments, fretting will be produced at the contact interfaces. In addition, serious environmental pollution particles will affect contact resistance of the connectors. The fretting will worsen the reliability of connectors with the pollutant particles. The combined effects of fretting and quartz particles on the contact resistance of the gold plating connectors are studied with a fretting test system. The results show that the frequencies have obvious effect on the contact resistance. The higher the frequency, the higher the contact resistance is. The quartz particles cause serious wear of gold plating, which make the nickel and copper layer exposed quickly to increase the contact resistance. Especially in high humidity environments, water supply certain adhesion function and make quartz particles easy to insert or cover the contact surfaces, and even cause opening resistance.

The type test of CuW/CuCrZr arc contact used for ultra-high voltage system capacitor bank switch was conducted. Through the comparative analysis of morphologies, compositions, properties and microstructures of the contact materials before and after failure, it can be found that the abnormal open of moving arc contact and the arc erosion and mechanical wear of static arc contact are the major reasons affecting the arc contact failure. The failure mechanism and main affecting factors were investigated in detail. The results showed that arc erosion and mechanical wear are the two main factors that affect the service lifetime of arc contacts used for ultra-high voltage transmission lines and cannot be ignored. Therefore, improving the arc erosion resistance and mechanical wear resistance simultaneously is the key to prepare the arc contact materials with longer lifetime.

International audience; Presence of white etching cracks has been widely associated with early failures of rolling bearings in a number of applications, with wind turbine gearbox bearings being the most frequently cited and practically significant example. Despite the recent research efforts, there is yet no universal agreement on the mechanisms of formation of these cracks and little direct evidence of their significance to bearing reliability. In an attempt to address this, this paper proposes a new theory on the origins and significance of white etching cracks. The paper provides systematic experimental evidence in support of this theory through rolling contact fatigue tests performed with AISI 52100 bearing steel specimens on a triple-disc machine over a wide range of contact conditions. The test results show that white etching cracks can be formed with base oils as well as commercially formulated transmission and engine oils. WECs were generated under slide-roll-ratios ranging from 0.05 to 0.3, under positive and negative sliding, different contact pressures and specific film thicknesses ranging from 0.1 to 0.7. No white etching areas were ever observed without the associate crack being present, and it was also shown that white etching areas themselves can be produced in a pure rubbing contact of bearing steels under both lubricated and unlubricated conditions. These results provide direct evidence that the steel transformations that exhibit themselves as white etching areas are formed through rubbing of the existing crack faces, and that the chemical composition of the lubricant and the magnitude and direction of sliding are not the primary driver of WEC formation, in contrast to literature. Instead, the results presented here show that WECs are formed through the action of a specific stress history in time via the following mechanism: (i) Short-lived high contact stresses, which can be caused by a number of factors, act in the initial stages of the component life to initiate early fatigue cracks, (ii) These high stresses cease and the contact subsequently operates under a relatively moderate nominal stress so that the early-formed cracks propagate relatively slowly and their faces rub and beat together for a prolonged period, (iii) White etching areas are formed around the existing cracks through this crack-face rubbing, (iv) Eventual contact failure occurs through pitting which can be caused by a white etching or a non-white etching crack depending on its location and propagation rate. Standard contact fatigue life models are unable to account for the adverse effects of this specific stress sequence owing to their use of linear damage accumulation rules, which leads to such failures being termed as ‘premature’. The proposed theory asserts that the white etching cracks are not the cause of ‘premature’ bearing failures, but that both the WECs and the earlier-than-predicted bearing failures are caused simultaneously by a third factor: a specific time history of applied contact stress.

In this paper, we propose a method for estimating heart rate from pulse wave measured through conductive fibers mounted on forearms. In recent years, heart rate is an effective index for describing mental and physical condition. Accordingly, many types of wearable heart rate measuring devices have been developed. However, there are problems such as uncertainty in the measured waveform caused by contact failure and large burdens on subjects brought by wearing oppression. Hence, it is necessary to have a device that brings less burdens and can measure stably. In this research, we propose a forearm-mounted pulse wave measuring device made of stretchable conductive fibers that can be comfortably worn and can reduce contact failure. In addition, we propose a method for estimating heart rate from pulse wave measured by proposed device. In order to evaluate the effectiveness of the proposed method, we show the accuracy of measuring heart rate and the sample entropy of the heart rate variability waveform. As a result, it was confirmed that pulse wave can be measured stably irrespective of both rest and moving state.

The typical characteristics of the change in contact resistance and tangential force with fretting cycles are compared with different fretting frequencies. Intermittent phenomena or short duration discontinuities during each fretting cycle are recorded explicitly. The instantaneous higher contact resistance values that appeared at the contact zones continuously corresponded to the distorted tangential force between contacts. Fretting frequency was determined as the crucial parameter that influenced the intermittent contact resistance. Subsequently, the contact failure mechanism of frictionally heated electrical contacts during high-frequency fretting was explained by introducing the electrical contact theory and thermoelastic instability model.

The selection of slewing bearings is based on the static load-carrying capacity. In this sense, manufacturers provide selection curves in their catalogues. However, little information is given about their origin. This work develops new and more versatile selection curves for four contact point slewing bearings, with a clear explanation of their background, scope and limitations. The new curves take into account the two possible static failure types, the ball-raceway contact failure and the bolted joint failure.

In Kyoto downtown district, the ‘Road Contact Failure’ of the traditional Alley space is considered as a big hazard, regarding the disaster prevention and evacuation. This paper has focused on the transformation process of the Road Contact Failure area, by clarifying the changes in the road contact conditions, the site form as well as the relationship between each other. Further discussion is given on the challenges point towards the rescue techniques applied in Road Contact Failure area by revealing the factor which caused the changes in the road contact condition and the site form, not only in a comprehensive city level, but also in a specific site level. To conclude, it is found that there is a mutual relation between the road contact conditions in the target site and the ones in the peripheral site. Moreover, regarding the application of the deregulation, it was pointed out that the existing road contact conditions in both the target site and the peripheral site should be considered.

Summary Tectonic tremor and low-frequency earthquakes (LFE) have been identified globally, but the physical mechanisms responsible for different types of LFE recurrence patterns are still elusive. Here we use a brittle ductile friction model to study the frictional conditions leading to different LFE recurrence patterns observed in central California. We do a comprehensive search of the friction parameters, including the brittle contact failure length and ductile damping strength to generate synthetic LFE bursts that match three different occurrence patterns of LFE bursts. We find that the output synthetic LFE burst recurrence type varies under different frictional conditions. The chaotic recurrence LFE sources require a higher brittle-to-ductile friction ratio, consistent with the observation that they are mainly at shallower part of the brittle-ductile transition zone. The tri-modal recurrence LFE sources require a wide distribution of asperity sizes, indicating that the segment of deep SAF between Monarch Peak and Parkfield is likely to be more fragmented and weaker than the surrounding segments.

A numerical solution of thermal elastohydrodynamic lubrication (TEHL) of finite line contacts for axially profiled and tilted cylindrical roller is presented. The effects of tilting angle, entrainment velocity and slide-roll ratio on the lubricating performance and the subsurface stress field have been investigated specifically from the point of view of the von Mises stress as it provides a better criterion for rolling contact failure and material damage. The results show that tilting angle, entrainment velocity and slide-roll ratio influence the pressure, temperature and von Mises stress distributions. As tilting angle increases, the maximum von Mises stress becomes larger. As entrainment velocity and slide-roll ratio change, the maximum von Mises stress changes in different routes.

In this article, the corrosion behavior of the gold plating and the silver plating specimens are studied. It is found that the airtightness have effects on the contact properties of the different plating specimens. The surface morphology of specimens is observed by stereoscopic microscope and scanning electron microscope (SEM). Chemical constitution was examined by X-ray energy spectrum. The contact resistances were measured by four-point method. The experiment results show that the corrosion appearance of the silver plating is severer than that of the gold plating one after airtightness test. The corrosion degree of plating specimens decreased with the increase of the coatings thickness. The static contact resistances of corrosive spots appear higher contact resistance than normal value. It is found the high and unstable contact resistance of the corrosion products is more likely to cause contact failure. The influencing factor of the corrosion products with different plating has an important influence on the airtightness test and the contact failure of electric connector.

A series of ballistic tests were performed to investigate the bulletproof performance of UHMWPE composites. The temporal evolution of the UHMWPE composite plate back-face bulge height and diameter were captured by high-speed photography. The experiments show the composite plate were perforated when the impact velocity greater than 880m/s. The maximum bulge height and diameter can reach to 3.63-8.23mm and 37-64.5mm at the experimental velocity range , respectively. After that, the numerical model was built with composite material model MAT59 in LS-DYNA and stress based contact failure between plies were adopted to model the delamination mechanism. The number of plies of numerical model shows a strong dependency on the numerical results. Comparisons between numerical predictions and experimental results in terms of bulge height and diameter are presented and discussed. The maximum bulge diameter is good agreement with experiment, but the computational results under predict the maximum bulge height. The computational analysis show the damage development of the plate penetration by the projectile is shearing dominated at first, then the plate undergoes delamination and stretching in the later part of the impact process. The von mises stress at front and back face of the plate were also studied.

To solve the problem of contact failure for heavy-duty cycloid reducers, the teeth mesh was originally studied as a Non-Hertz elastic contact problem. An analysis method called non-Hertz flexibility matrix method (NHFMM) for the teeth contact was developed for the teeth profile modification of pin gear. The NHFMM analysis shows that the edge concentrated pressure calculated by non-Hertz method is 2.11 times of that by Hertz method on the pin teeth without profile modification. In the end, the analysis results of NHFMM were verified by a specially designed photo-elastic experiment.

In this paper, we presented the results from three related analysis performed by adopting the failure models, which provided an explanation of performance influencing factors caused by different number of contact cores, for the purpose of measuring the temperature change and deformation value, which were the factors causing contact failure. The failures were localized in contact parts of the connectors. Performed investigations included thermal analysis, modal analysis, harmonic response analysis and contact failure analysis. From the results of these simulations, related temperature and vibration analysis nephograms were got respectively. And the correctness of results of thermal analysis was verified by Fourier law. The research results of this paper provide a reference for thermal analysis and vibration analysis of electrical connectors, which is important for ensuring the reliability and safety of electrical connectors.

This study analyzes spatial structure of Kyoto by using large scale maps of the city from the year 1951. The authors aim to make reappearance the structure of the city through the usage of maps at the time when the establishment of the Building Standard Law. The distribution of the situation of road contact failure the part alley space will be compared with that of the current alley space. As the results, this study will help the authors to clarify the reason of the alley transformation in sixty years time.

This study examines legal interpretation of the alley space of Kyoto. What kind of situation is the small alley where a traditional landscape is left in by a current law. In the site connected to the alley, a building is often impossible. A purpose of this article is to consider update possibility by examining what kind of correspondence is taken when the application to the city is considered to be it in road contact failure. The width of the alley often does setback to become 4m, but the narrowness that is one of the qualities of alley will be in this way lost in future. Safe inspection is necessary to promote technique to maintain a small alley.

In recent years, there has been increasing demand to miniaturize wiring harness connectors in automobiles due to the increasing volume of electronic equipment and so on. With this demand, contact failure caused by the fretting corrosion seems to become a serious problem in the future. In this report, three-dimensional observations using Focused Ion Beam (FIB)-SEM method have been made for tin plated fretting contacts before and after the contact resistance increase with tin plating thickness 5µm. With these observations, the three dimensional structural transition from tin to tin oxide have been examined.

Due to their high isolation, low insertion loss, high linearity, and low power consumption, microelectromechanical systems (MEMS) switches have drawn much attention from researchers in recent years. In this paper, we introduce the research status of MEMS switches in different bands and several reliability issues, such as dielectric charging, contact failure, and temperature instability. In this paper, some of the following methods to improve the performance of MEMS switches in high frequency are summarized: (1) utilizing combinations of several switches in series; (2) covering a float metal layer on the dielectric layer; (3) using dielectric layer materials with high dielectric constants and conductor materials with low resistance; (4) developing MEMS switches using T-match and π-match; (5) designing MEMS switches based on bipolar complementary metal–oxide–semiconductor (BiCMOS) technology and reconfigurable MEMS’ surfaces; (6) employing thermal compensation structures, circularly symmetric structures, thermal buckle-beam actuators, molybdenum membrane, and thin-film packaging; (7) selecting Ultra-NanoCrystalline diamond or aluminum nitride dielectric materials and applying a bipolar driving voltage, stoppers, and a double-dielectric-layer structure; and (8) adopting gold alloying with carbon nanotubes (CNTs), hermetic and reliable packaging, and mN-level contact.