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A novel frame-embedded track (NFET) with additional beams between the prefabricated rail seats before was proposed, but its geometric parameters need to be further optimized, in order to solve the problem of difficulty in adjustment, due to the independence of the two prefabricated rail seats during the construction of tram. Based on the finite element method, the geometric parameters of the NFET structure are systematically studied and optimized. The research shows: (1) As the width of the beams and the thickness of the lower slab increases, the mechanical characteristics of the NFET structure does not change significantly; therefore, the recommended design reference value for these two are 240 and 80 mm, respectively. (2) When considering the cable and the drainage facilities, the stress state of the NFET structure is less affected (or even improved), which proves that the layout of the cable and the drainage facilities is feasible. (3) According to the analysis during different construction stages, the stress of the NFET rail seats is generally greater than the stress of the cast-in-place concrete. It is recommended that the intensity of the cast-in-place concrete should be greater than that of the prefabricated frame structure. [ABSTRACT FROM AUTHOR]

In view of the problems present in the construction process of the embedded track structure of modern tram, we have designed a Novel Fastener Type Ballastless Track (NFTBT) for tram. To optimize the size of the NFTBT's structure, the finite element model of the NFTBT's structure in the tram running stage is built, the mechanical characteristics of the NFTBT's structure are calculated, and the geometric parameters of the NFTBT's structure are systematically studied. The research results are as follows: (1) As the size of the track slab increases, the displacement differences of the middle part of the NFTBT are similar, and the size of the track slab has little effect on the displacement. (2) The stress difference of the NFTBT's structure under the different distances between the centers of the adjacent grouting holes' conditions is small. Although a larger distance between the centers of the adjacent grouting holes can reduce the number of grouting holes in the track slab, the distance should not be too large to reduce the peak stress at the bottom of the NFTBT. (3) When the distance between the adjacent fasteners of the NFTBT changes within a certain range, the rail is greatly affected by the uneven settlement of the subgrade, and the track irregularity will be aggravated. (4) The NFTBT does not require the implementation of cable passages at intervals, which facilitates the passage and fixation of the cables in the tram operation section and can reduce the difficulty of adjusting the geometry of the track structure, thus accelerating the construction progress. [ABSTRACT FROM AUTHOR]

Rail fasteners are among the key components of ballasted track of high-speed railway due to their functionality of fixing rails to sleepers. The failure of rail fastening system hinders the transmission of train loads to underlying track substructure and therefore endangers the operation safety and longevity of ballasted track. This paper first established a three-dimensional (3D) numerical model of the train-ballasted track-subgrade coupling system by integrating multibody dynamics (MBD) and finite element method (FEM). Numerical simulations were then performed to investigate the effects of different patterns of rail fastener failure (i.e., consecutive single-side, alternate single-side, and consecutive double-side) on critical dynamic responses of track structures, train running stability, and operation safety. The results show that the resulting influences of different patterns of rail fastener failure descend in the order of consecutive double-side failure, consecutive single-side failure, and alternate single-side failure. As the number of failed fasteners increases, the range where dynamic responses of track structures are influenced extends, and the failure of two consecutive single-side fasteners exerts a similar influence as that of four alternate single-side fasteners. The failure of single-side fasteners affects dynamic responses of the intact side of track structures relatively insignificantly. The influence of rail fastener failure on track structures exhibits hysteresis, thus indicating that special attention needs to be paid to locations behind failed fasteners during track inspection and maintenance. The occurrence of the failure of two or more consecutive fasteners demands timely maintenance work in order to prevent aggravated deterioration of track structures. The findings of this study could provide useful reference and guidance to smart track condition assessment and condition-based track maintenance. [ABSTRACT FROM AUTHOR]

With the gradual increase of the cargo weight of heavy-haul trains, the traditional ballasted track with the accumulation of stone and ballast has been unable to meet its structural safety requirements. From the comparison of the three common ballastless tracks in China, it can be seen that the low-vibration track (LVT) has the advantages of reasonable structure, low cost, and easy maintenance. Therefore, the design and research of heavy-haul railways are focused on, and it is urgent to study the applicability of LVT in heavy-haul railways. Method: By improving the slope of the short side of the LVT support block, the support block has a better load bearing capacity, so as to achieve the purpose of bearing a larger axle load. Through 1:1 full-scale model test and finite element simulation, the static mechanical properties of Improved LVT (ILVT) and Traditional LVT (TLVT) are compared and analyzed. Result: Compared with TLVT, ILVT has smaller vertical displacement and track gauge changes when subjected to the same load. The proven and reliable finite element model also shows that ILVT's load sharing is less affected. In the case of achieving the same deformation, ILVT can withstand greater vertical and lateral loads. Conclusions: Compared with the TLVT, the ILVT design can reduce the vertical displacement of the rail and the supporting block, better control the track subsidence, and improve the driving safety of the LVT. At the same time, ILVT improves the anti-overturning ability of the rail and support block under lateral load, reduces the expansion of the gauge and the lateral spacing of the support block, and improves the stability of the track structure. ILVT can also be considered for the weight of 40t and other large axle load, and has broad application prospects. [ABSTRACT FROM AUTHOR]

Low-Vibration Tracks (LVTs) are widely used in subway tunnels for their excellent performance, but the application in heavy-duty railways still requires a lot of feasibility studies. In this study, the statics performance of LVT under different axle loads, load direction, and load position is explored using the finite element software Abaqus. The Timoshenk beam element and nonlinear spring element 3D solid element are used to represent rails, fasteners, and the other track structure respectively. The paper established the finite element model of LVT to study the mechanical characteristics of low vibration track structure under varying loading condition. The applied loads are determined according to the Heavy-Haul Railway Track Structure Design Code. The results shows: (1) The deformation and stress of the LVT structure show a linear relationship with the increase of the axle load. (2) Slab end loading and lateral load are more unfavorable to the stress and deformation of the track structure. When slab end is loaded with vertical load, the vertical load is distributed on four supporting blocks along the longitudinal direction with a ratio of 1:4:4:1, and the lateral direction is mainly borne by two adjacent fastener nodes with the total load proportion of 47% and 47% respectively. (3) The LVT structure can guarantee the safety of static performance under 30 t axle load and the maximum axle load should not exceed 36 t. The paper provides a guideline for the construction and maintenance of LVT structure in heavy haul railway. [ABSTRACT FROM AUTHOR]

Based on a bistable mechanism, a novel low- ${g}$ MEMS inertial switch with dual functions of self-locking and reverse-unlocking is presented, along with its fabrication and verification. This MEMS switch is fabricated on a Silicon-On-Insulator (SOI) wafer by using deep reactive ion etching (DRIE), Bosch processing, and wafer bonding technologies. A two-level system is proposed to realize dual functions of this switch, which mainly consists of a spring-mass-damping system as the first level and a bistable structure as the second level. According to the finite element analysis (FEA), the theoretical formula of the bistable structure has been successfully verified to deduce the static mechanical properties. Under positive and negative acceleration excitations, the dynamic response characteristics of the switch has been systematically simulated further. Furthermore, this inertial switch has been tested by using a centrifugal acceleration turntable, and its self-locking threshold and reverse unlocking threshold are 8 ${g}$ and 105 ${g}$ , respectively. Finally, the contact resistance of this MEMS switch is measured about $0.75~\Omega $ by a probe station. [2020-0302] [ABSTRACT FROM AUTHOR]

• An integrated model for investigating the train-induced cumulative deformation of subgrade is established. • The subgrade deformation is regarded as the time-varying excitation of train-track-subgrade interaction system. • The time-varying dynamic response of train-track-subgrade interaction system is described by this integrated model. This work focuses on two research projects. The first project deals with the prediction of the train-induced cumulative deformation of the high-speed railway subgrade based on the train-track-subgrade dynamic model, and the second project deals with the long-term performance of the train-track-subgrade interaction system subject to the permanent deformation of the subgrade. The train-track-subgrade interaction is established as the model fundament, and the empirical model of soil cumulative deformation prediction is introduced to realize the joint analysis of the train-induced cumulative deformation of the subgrade and its effect on the performance of the time-varying dynamic system. From the numerical results, the train-induced cumulative deformation of subgrade shows a fast and then slow trend, and the deformation has periodic distribution in the longitudinal direction. Although the cumulative deformation of the subgrade for the ballastless track is small compared with that of ballasted track, its effect on the vertical response of the train-track-subgrade interaction system is obvious. With the development of cumulative deformation of subgrade, the vibrations of the car body are excited in the frequency band of 0∼100 Hz. Furthermore, the maximum car body vertical accelerations, the wheel-rail vertical forces, and the vertical accelerations of track and subgrade increase by about 34∼48.4%, 125 %, 400 %, and 66.7 %, respectively. [ABSTRACT FROM AUTHOR]

Abstract In view of low sensitivity of traditional stethoscope and valuableness of existing intelligent electronic stethoscope, a T-type MEMS heart sound sensor with high sensitivity, low cost and high SNR is designed, which is combined with MEMS technology, bionic principle, piezoresistive principle and Wheatstone bridge detection principle. Firstly, working principle of T-type MEMS heart sound sensor is introduced; Secondly, theoretical model of T-type sensitive microstructure is established, and its performance is simulated and analyzed by ANSYS finite element simulation software, then the size of T-type sensitive microstructure is determined and T-type MEMS heart sound sensor is made. Finally, T-type MEMS heart sound sensor prototype is tested. The results of tests show that: sensitivity and working frequency band of T-type MEMS heart sound sensor are respectively -183dB@500 Hz and 0–1000 Hz, which have verified correctness and practicability of T-type microstructure. In addition, the acoustic properties of S1 and S2 are analyzed from time domain and frequency domain, which indicates that heart sound signals detected by T-type MEMS heart sound sensor are highly consistent with that of 3200-type electronic stethoscope of 3 M company. Moreover, SNR of T-type MEMS heart sound sensor is 7.9 dB higher than 3200-type electronic stethoscope of 3 M company. The above shows that the T-type MEMS heart sound sensor can provide a powerful basis for early accurate diagnosis of cardiovascular disease and has broad prospects in the field of heart sound detection. [ABSTRACT FROM AUTHOR]

• Design of a MEMS electronic stethoscope with working bandwidth 20–811 Hz. • The feasibility of electronic stethoscope is proved with theory and experiment. • Test on this electronic stethoscope is found that basically consistent with the 3 M. • The SNR of the electronic stethoscope is higher than 3 M. In this paper, a bat-shape electronic stethoscope based on MEMS technology is presented. The detector microstructure in bat-shape electronic stethoscope is designed by combining theoretical analysis and finite element method. Visual heart sound signal processing includes circuit and upper computer design. The frequency of the clinical heart sound signal is mostly in the range of 20–600 Hz. The sensitivity of the microstructure, its work-bandwidth and the SNR of the system are the key points of this design. And the final test results showed that the sensitivity of the sensor is −180.7 dB@500 Hz and SNR is 38 dB (17 dB higher than the 3 M electronic stethoscope). Based on theoretical analysis and test results, the bat-shape MEMS electronic stethoscope designed in this paper features small size, high sensitivity, high SNR and easy processing, and has broad prospects in the field of heart sound detection. [ABSTRACT FROM AUTHOR]

We report on a comprehensive method for analyzing landslide stability and the mitigation effect of countermeasures in this paper. The proposed method is a combination of theoretical method and numerical method. To address the uncertainties of the soil strength parameters, the rational values of these parameters are comprehensively determined by the back-analysis result of the reliability method and the result by the quantitative method, as well as the in-situ geological test. To evaluate the slope stability, the limit analysis using the 2D upper bound method and the FEM simulation using strength reduction method are performed, respectively. In order to illustrate the presented method, the so-called Lanmuxi landslide in China is selected as a case study. Results demonstrated that the stress and strain majorly concentrated at the toe and crown of the slope. According to the analysis results, countermeasures consisting of anchor lattice beams, landslide piles, and cracks filling, are suggested to reduce the failure risk of the landslide. Effect assessment based on the FEM analysis verifies the feasibility and effectiveness of the recommended countermeasures. [ABSTRACT FROM AUTHOR]

• The SIFs of cracks in the track slab are calculated by fracture mechanics theory and XFEM to judge the type of cracks. • The SIFs of cracks with different lengths and depths in the track slab under temperature loads are evaluated. • After freeze–thaw deterioration, the crack expansion possibilities in the track slab under temperature loads are analyzed. In seasonal frozen region, the Chinese Rail Track System (CRTS) III slab track is subject to temperature loads and freeze–thaw deterioration, which may lead to further expansion of microcracks in track slabs. Mechanical parameters of track structure materials after freeze–thaw cycles are obtained through the experimental tests in this study. A finite element model of CRTS III slab track on subgrade section is then established by ABAQUS. Based on fracture mechanics theory, the types of cracks generated in track slabs under temperature loads and freeze–thaw deterioration, and crack expansion law are analyzed by using extended finite element method. The results show that under temperature loads, the expanded cracks in track slab are mainly Mode Ⅰ - Opening mode. There is the possibility of expansion for transverse cracks with larger size on the upper surface of track slab under negative temperature gradient load. Vertical capillary cracks at the location where track slab is bonded to self-compacting concrete are more likely to expand. Freeze-thaw deterioration will reduce the difference between the SIFs of cracks and fracture toughness of track slab material, which has a certain promotion effect on crack expansion. [ABSTRACT FROM AUTHOR]

Highlights: [•] A two steps analytical approach is presented to analyze the interaction mechanics for excavation–soil–tunnels. [•] 3D numerical analysis is conducted and the simplified analytical method can overcome complex simulation. [•] Galerkin’s method is used to convert the differential equation into finite element equation. [•] The excavation unloading effects of bottom and surrounding walls can be fully considered. [•] The parametric analyses are presented to investigate the effects of excavation-induced unloading on tunnels. [Copyright &y& Elsevier]

The paper comparatively investigates the microstructures and mechanical properties of Inconel 718 superalloy manufactured by selective laser melting (SLM) and casting. The finite element analysis (FEA) method is used to simulate the temperature fields during SLM and casting processes. Driven by ultra-high temperature gradient and ultra-fast cooling rate during SLM process, the fine grains (average grain size of 48 µm) and dispersed fine precipitation in SLM-ed sample even after HSA (homogenization + solution + aging) and HA (homogenization + aging) heat treatment significantly enhance its mechanical properties, which far exceeds that of casting with average grain size of 1300 µm, and is comparable to that of forging. The microstructure of casting with coarse irregular Laves phases, acicular δ precipitates and globular carbides in the interdendritic zones after HSA heat treatment and some defects existed possibly result in premature failure of tensile samples. The microstructure without δ phases but only some globular carbides in the grain boundary of SLM-ed sample after HA heat treatment possesses higher mechanical properties than that after HSA heat treatment, in which there is only some finer needle-like δ phase and few carbides are precipitated in the grain boundaries. The analysis shows the large amounts of δ phase precipitated in the matrix will deteriorate the plasticity of SLM-ed IN718 superalloy, the appropriate reduction of the δ phase will improve the strength and plasticity of material simultaneously. [ABSTRACT FROM AUTHOR]