Fastening Force Research Articles

Experimental study on new structure teeth in a high-temperature environment.

In high-temperature drilling, especially in high-temperature geothermal drilling, cone bits often experience common and severe tooth loss. This issue significantly reduces the cone bit's service life and has a detrimental impact on drilling efficiency. The quality of the fixed teeth plays a crucial role in the performance of the cone bit. In high-temperature environments, conventional methods fail to meet the requirements for securing the cone bit's teeth. Therefore, to address the tooth loss problem in high-temperature drilling, a new tapered tooth structure is proposed. Laboratory experiments were conducted to secure teeth with varying tapers at both normal and high temperatures. The results revealed that the maximum fastening force increased progressively with the degree of taper, reaching its peak at C50. Compared to conventional cylindrical teeth, the maximum fastening force increased by approximately 88.6%-271.1% at different temperatures. The tapered structure demonstrated superior tooth-fixing strength. The maximum fastening force is the smallest at 300 °C, approximately 23.7%-61.2% lower than at normal temperature. Under the same interference conditions, the maximum fastening force increased with greater taper. With interference values of 0.075, 0.095, and 0.115, the maximum fastening force increased by 48.9%-175.1%, 14%-141.6%, and 53%-271.1%, respectively, when compared to cylindrical teeth with C300, C200, C100, and C50 tapers. The tapered structure exhibited superior tooth-fixing strength and significantly enhanced tooth retention strength at high temperatures.

Dynamic Analysis of Slab Track with Crack Considering Rail Corrugation

To investigate the dynamic response of ballastless slab track with crack in the rail corrugation area under the load of urban rail vehicle, this study establishes a vertical coupling dynamic model of the vehicle-rail-slab track, considering crack and rail corrugation. The exact closed-form solution of the vibration mode of the Euler Bernoulli beam with crack is introduced. Furthermore, a finite element model of the slab track is developed, and the vertical dynamic model's fastening force is applied to the slab track at the rail corrugation frequency to calculate the surface compressive stress of the slab track. The results indicate that, under rail corrugation conditions of varying magnitudes, the presence of crack induces higher vertical acceleration amplitudes in the slab track at low frequencies. As the wave depth increases, the acceleration of the slab track at the crack gradually intensifies. Moreover, with an increasing wavelength, the corresponding frequency to the acceleration amplitude of the slab track at the crack gradually decreases. Notably, when the wave depth is 0.2 mm and the wavelength is 50 mm, the axle load transfer rate exhibits the greatest increase. These research findings offer valuable insights for the maintenance of urban rail transit slab track systems.

Mechanical strength enhancement of natural fibre composites via localized hybridization with stitch reinforcement

Abstract Stress concentration is an unavoidable phenomenon during the fabrication of composite structures. This research focuses on reducing stress concentration. Circular holes made on the composite structural member induce stress-concentrated regions. These stress-concentrated regions around the circular hole (considered as a weak section) were strengthened by adding synthetic fibre (local hybridization) in the form of fibre stitches (locked loop stitch). Through conducting a single fibre pull-out test, the present study analysed the impact of incorporating synthetic fibres in stitch form and the enhancement of Interfacial Shear Strength (IFSS). The load acting on the broken warp fibres is distributed to the broken weft fibres when the number of concentric stitches increases. The increment of concentric stitches resulted in the increase of IFSS due to localized hybridization. The tensile test results also show a significant improvement with 110 Nmm axial fastening force, from 6.749 MPa (for the natural fibre composite) to 76.91 MPa (for locally hybridized with eight concentric stitches). A simple bolted lap joint with local hybridization around the hole has been evaluated for different clamp-up forces. The best combinations of the clamp-up force and the extent of hybridization have been identified. SEM images illustrate the reduced voids and the reduced fibre pull-out due to the local hybridization around delamination-prone areas.

Analysis of the significance of the imparted fastening forces and material properties of plates on the fatigue life of bolted joints using FEM

The present study attempts to analyze the significance of imparted fastening forces, the friction induced and the material of the plates on the fatigue life (Nf) of double-lap bolted joints with the aid of numerical analysis. The three-dimensional FE models of the joints were created and subjected to four distinct fastening forces on the bottom face of the bolt stem and a cyclic load with a constant maximum stress for plates made of Aluminium alloy - Al 2024-T3 and Magnesium alloy - Mg AZ31B. The dispersion of stress and strain in the plates stimulated by the imparted fastening forces and the applied cyclic load was assessed utilizing finite element (FE) method with the help of ANSYS software. The order and the combination of parameters to execute the simulations and to ascertain the main effects were formulated using Taguchi’s L8 array. The outcomes from the FE analyses were utilized to appraise the fatigue lives of the bolted joints using the Smith-Watson-Topper multi-axial fatigue criterion. The outcomes of the FE analysis made clear that the fastening forces and the fatigue life of the joints were positively co-related. The results also revealed the effect of material strength and alloy composition on the fatigue life.

MSWasm: Soundly Enforcing Memory-Safe Execution of Unsafe Code

Most programs compiled to WebAssembly (Wasm) today are written in unsafe languages like C and C++. Unfortunately, memory-unsafe C code remains unsafe when compiled to Wasm—and attackers can exploit buffer overflows and use-after-frees in Wasm almost as easily as they can on native platforms. Memory- Safe WebAssembly (MSWasm) proposes to extend Wasm with language-level memory-safety abstractions to precisely address this problem. In this paper, we build on the original MSWasm position paper to realize this vision. We give a precise and formal semantics of MSWasm, and prove that well-typed MSWasm programs are, by construction, robustly memory safe. To this end, we develop a novel, language-independent memory-safety property based on colored memory locations and pointers. This property also lets us reason about the security guarantees of a formal C-to-MSWasm compiler—and prove that it always produces memory-safe programs (and preserves the semantics of safe programs). We use these formal results to then guide several implementations: Two compilers of MSWasm to native code, and a C-to-MSWasm compiler (that extends Clang). Our MSWasm compilers support different enforcement mechanisms, allowing developers to make security-performance trade-offs according to their needs. Our evaluation shows that on the PolyBenchC suite, the overhead of enforcing memory safety in software ranges from 22% (enforcing spatial safety alone) to 198% (enforcing full memory safety), and 51.7% when using hardware memory capabilities for spatial safety and pointer integrity. More importantly, MSWasm’s design makes it easy to swap between enforcement mechanisms; as fast (especially hardware-based) enforcement techniques become available, MSWasm will be able to take advantage of these advances almost for free.

接触剛性によるボルト締結モデルと透過超音波パルスを用いた定量評価

Evaluation of bolt tightening plays an important role to keep a performance of a mechanical structure. Lack of the fastening force induces slack and falling of the tightening bolt. Excessive fastening force induces a plastic deformation of screw thread and causes the decline of the fastening force. Therefore, guarantee of the bolt tightening is an important subject in order to secure the mechanical structure against unforeseen accidents. However, most of preceding studies are restricted within qualitative evaluation of the slackness. In the field of industrial manufacturing, quantitative evaluation of the bolt tightening is strongly required. In this paper, the authors propose a technique for quantitative evaluation of bolt tightening, and in this technique, the flank of the screw thread is assumed to contact through a contact stiffness. The transmissivity and reflectivity of an ultrasonic pulse wave through the flank are derived as a function of contact stiffness, and the contact stiffness is capable of being identified from experimentally acquired amplitude of ultrasonic pulse wave. The contact stiffness is quantitatively identified and the surface pressure on the screw thread is estimated by the identified contact stiffness through the results of the preceding study. The proposed technique treats an ultrasonic pulse perpendicularly transmits a fastening bolt, and is applied to an experimentally acquired ultrasonic pulse which enters a side surface of nut and transmits a bolt-nut fastening element. The identified contact stiffness is shown to be adequate for the given fastening force to the bolt-nut fastening element, and validity of the proposed technique is demonstrated.

Quantification of longitudinal fastener stiffness and the effect on fastening system loading demand

Over the past 20 years, there have been at least 10 derailments due to spike fastener fatigue failures in North America. These fatigue failures have been considered a moderate to severe challenge that require manual walking inspections that are both time and labor intensive. These fatigue failures have been found to result from spike overloading due to lateral and longitudinal loads. To date, there has been limited quantification of the vertical, lateral, and longitudinal fastener forces in track. This paper quantifies the effect of fastener type on fastener load to account for various track types and locations. Laboratory experimentation was performed to quantify the stiffness of multiple fastening systems and this data was input into a previously validated analytical model to quantify the effect of stiffness on fastener loading. Additional laboratory experimentation was performed to quantify the relationships between both fastening system type and vertical loading and spike strain. While the laboratory data indicate a significant variance in stiffness between fastening systems, the model results indicate that the load transferred to the fastening system is less sensitive. However, spike strain data indicate the load path was affected by fastener type and vertical load. The characterization of longitudinal stiffness of multiple fastening systems and the relationship to spike load as presented can be used to advance track mechanistic-empirical design and improve rail neutral temperature prediction and track buckling models.

Analytical Nonlinear Modeling of Rail and Fastener Longitudinal Response

Comparatively little attention has been given to the quantification of fastener demands, especially in the longitudinal direction. Research quantifying fastener demands is justified by the more than 250 FRA reportable derailments on mainlines and sidings in the United States caused by “defective or missing spikes or rail fasteners” over the last 20 years. Failed fasteners are rarely caused by loads acting from a single direction (vertical, lateral, or longitudinal); they occur from a combination of these loads. A literature review identified that though multiple models have been developed for analyzing track, they were not designed to quantify fastener demands, especially those in the longitudinal direction, and some make assumptions that could be improved on based on more recent research into the mechanics of fastening system behavior. This paper advances the mechanistic–empirical (M-E) track analysis and design approach through the development, validation, and application of a 3D nonlinear parametric track model that quantifies longitudinal fastener demands. Key research findings include: bilinear approximations, in combination with considering the interaction between vertical loads and slip, were necessary to accurately quantify fastener forces; ballast and fastener stiffness had a direct logarithmic relationship on fastener load; and for well-supported sleepers, changes in component resistance to slip produced minimal changes in fastener demands because the vertical applied load increased the required load to produce slip. Going forward, this validated model could be used to quantify fastener and track demands for additional loading and operational scenarios to further optimize component design for improved track safety and reliability.

Study on Influence of Ballast Spring Modulus on Track Structure Based on Finite Element Method

The finite element method is used to simulate the orbital structure, and the finite element model of "rail - sleepers - ballast" can be established. The model of the elastic modulus of different ballast and sleeper is calculated, and the rail displacement, the sleeper stress and the fastening force are deduced. The results show that the elastic modulus of the ballast can be increased to reduce the displacement of the rail and the supporting force of the fastener, but the stress of the sleeper will be increased. When the modulus of elasticity increases, the rail displacement, small.

Mapping Relation between Rail and Bridge Deformation Considering Nonlinear Contact of Interlayer.

This paper examines the effect of structural deformation on the unit slab-type ballastless track structure of high-speed railway. The principle of stationary potential energy was used to map the relation between girder vertical deformation and rail deformation considering the effect of subgrade boundary conditions and the nonlinear contact of interlayer. The theoretical model was verified by comparing with the finite element analysis and experimental results. The theoretical model was used to analyze the effects of several key parameters on the rail deformation, such as vertical deformation amplitude, elastic modulus of the mortar layer, and vertical stiffness of the fasteners. The results show that the track slabs suffered significant disengagement, which makes the deformation of the track structure at the position of the beam joint tend to be gentle when nonlinear contact between the mortar layer and the track slabs was considered. The track slabs disengagement mainly occurs near the beam joints (the side of the deformed beam). As the deflection amplitude of the girder increases, the track deformation, the fastener forces and the disengagement length of the track slabs are obviously nonlinear. When the vertical stiffness of the fastener and/or the elastic modulus of the mortar layer increase, the fastener force and the track plate disengagement length increase monotonically and nonlinearly, which will adversely affect the life and safety of the track structure.

Experimental and numerical study on the anti-sliding performance of full-lock coil cable clamps

The full-lock coil cable clamp node is an important joint in cable structures, and its sliding will reduce the bearing capacity and stability of the structure. Based on cable clamp node slide resistance tests and finite element analyses, the bolt pre-tightening force, cable tensioning sequence, and parameters such as the cable diameter were investigated to determine their influence on the cable clamp slide resistance. The stress distribution and variation in cable in the process of cable clamp sliding with steel wire was obtained. The main conclusions are as follows. (1) The bolt fastening force is basically proportional to the ultimate anti-slide bearing capacity of the cable clamp. The reduction coefficients for an 80 mm cable with initial fastening forces of 125 kN, 175 kN, and 225 kN are 0.49, 0.56, and 0.61, respectively. (2) Tensioning the cable first and then tightening the bolt can effectively improve the ultimate anti sliding bearing capacity of the cable clamp. The ultimate anti sliding bearing capacity of the cable clamp tested in this paper is increased by 38%. (3) Under the condition of the same initial fastening force, with increasing cable diameter, the sliding bearing capacity decreases linearly. (4) During cable clamp sliding, the stress of the cable in the slide direction of the cable clamp decreases, while the stress of the cable on the other side increases. (5) A calculation equation for the slide resistance ultimate bearing capacity of full-lock coil cable clamps considering the cable diameter and cable clamp length is obtained.

Influence of different ultrasonic transducers on the precision of fastening force measurement

In the assembly process of aero-engines, the accurate measurement of bolt fastening force is particularly important, which is related to the normal operation of the entire system. Ultrasonic non-destructive testing has been applied to bolt fastening force measurement and has a broad application background. The core device of the ultrasonic transducer is a piezoelectric ceramic wafer, and the normal operation of the wafer is affected by the power frequency and external stress. For the same type of bolt with the same nominal diameter, the ultrasonic transducer wafers of different diameters will cause the transducer wafers to be subjected to different external stresses. According to the acoustoelastic effect, the relationship between the variation of time of flight (TOF) and bolt fastening force of different types of ultrasonic transducers is established. Then the measurement errors of various models are calculated and analyzed. The experimental results show that when the nominal diameter of the bolt is close to the diameter of the wafer of the ultrasonic transducer, the fastening force measurement accuracy of the bolt is the highest. When small or large size transducer is used, the measurement accuracy will be reduced due to energy and external stress. When a transducer with a higher center frequency is used to measure the fastening force of the bolt rod, the accuracy of the model established due to the faster attenuation of the sound wave is reduced, and the accuracy of the measurement result is reduced. Therefore, in order to ensure the accuracy of the fastening force measurement in the aerospace field, when selecting an ultrasonic transducer, the impact of the transducer size and center frequency should be fully considered.

The research on the fixation strength of tapered cone bit teeth

In view of the tooth dropping phenomenon caused by the complex formation and other factors of the cone bit, a taper structure tooth is proposed. Experimental research on the strength of the proposed taper tooth was performed to study the influence of taper, interference, and transverse force on tooth fixation strength. The experimental results show that for different tapers (C50, C100, C200, C300, and C400), the maximum fastening force corresponds to an interference of 0.095 mm, and is 5.39–85.36% higher than that of a conventional cylindrical tooth, and the maximum fastening force is 30.25 kN for a C50 taper. Simulation results by the finite element method, were within 10% of the experimental results, verifying the simulation model. Through the numerical simulation of the tapered and cylindrical teeth at different temperatures, it is concluded that tapered teeth have better fixation strength than the cylindrical teeth, which can greatly improve the drilling efficiency of the cone bit in conventional and high-temperature drilling.

Taming Tech Giants with a Per-Se Rules Approach? The Digital Markets Act from the "Rules vs. Standard" Perspective

From the vs. standard approach (in law & economics) the regulatory approach of the DMA proposal of the EU Commission, which requires that all gatekeepers have to com-ply with the same set of obligations with regard to all core platform services, can be seen as a strict per-se rule regime enacted by the legislator, which tries to minimize investigations and assessments by the Commission for avoiding the problems of traditional competition law. It breaks in a radical way with the long-term evolution towards a standard-based rule of reason approach in competition law (with its focus on the effects on consumer welfare), which is widely seen as ineffective for digital markets. This article analyzes the DMA and its manifold problems from the perspective of the benefits and costs of using rules or standards in competition law (error costs analysis). It shows that the DMA runs into a number of difficult problems, partly through the per-se rules approach itself, partly through the incomplete specification of many obligations, the lack of an analysis of the aggregate effects of all obligations, and the lack of a clear assessment approach that can be used for investigations in the DMA. The vs. standard approach can also be used for discussing the proposals of introducing more flexibility within the DMA for achieving a better balancing between fast enforcement and the advantages of a more differentiated approach. The article concludes with some recommendations, e.g. also to be cautious about introducing too much flexibility, because this might lead back to the well known problems of the application of traditional competition law in digital markets.

Evaluation of quality parameters of the torque transmission connections of the multi-purpose machine spindle joints

The article presents the results of theoretical studies of a multi-purpose machine when assembling an HSK spindle-mandrel connection for accuracy, contact stiffness and strength. Studies were based on the developed original mathematical program complex for assessing the quality parameters of machine connections. They have been carried out with respect to HSK spindle-mandrel connections under conditions of multiple tool changes. Simulation of the coupling of connection parts for different values of the fastening (assembly) forces showed that HSK-type connections have a static uncertainty of basing under external loading conditions. Analysis of the stress-strain state of the connection joints was based on the finite element method when using software in the FEMAP 11.1 with NX NASTRAN. It showed that an unorganized change of bases occurs under the influence of external conditional load. It has been established that for tool mandrels of the HSK-63 type with a fixing force of 900 to 23000 N, the elastic displacements at the end of the mandrel vary from 1.5 to 0.6 μm under the condition of an external conditional load of 1732 N and, accordingly, from 8.0 to 2.5 μm with an external load of 6070 N. It was established that with a limiting value of the mandrel clamping force equal to 23000 N under conditions of external loading an unorganized change of bases occurs, namely: the end faces of the contact of the tool mandrel and the spindle are pressed, which reduces the geometric accuracy of a multi-purpose machine with a CNC.

Measurement of fastening force using dry-coupled ultrasonic waves

The accurate measurement of assembly fastening force of the high-pressure compressor rotor is of great significance to improve the structural connection quality and comprehensive performance of aero-engine. To solve the problem that liquid couplant reduces the measurement accuracy and causes the surface of the bolt to rust and corrode, a method of measuring the fastening force with dry-coupled ultrasonic wave was proposed in this paper. The measurement model of the fastening force including the thickness of the protective film of the ultrasonic transducer and the couplant was established, and the influence of the thickness variation in the couplant on the measurement accuracy of the fastening force was analyzed. Based on the propagation model of the ultrasonic wave on the heterogeneous interface and the principle of ultrasonic dry coupling, a coupling device was designed. At last, the experiment of fastening force measurement based on dry coupling and liquid coupling ultrasonic wave was carried out and compared. The experimental results show that the average relative errors of the fastening force measurement based on dry coupling and liquid coupling ultrasonic wave are 2.13% ± 0.42% and 3.15% ± 0.80%, respectively. Therefore, the dry coupling method can be as good or better in measuring the accuracy of the fastening force. Furthermore, it also overcomes the limitations of the liquid coupling method, which should make it more suitable to the measurement of fastening force in the aerospace field.

The study on tooth failure and fixation strength of cone bits under high temperature

A high temperature drilling cone bit is more likely to experience tooth shedding because of the high bottom-hole temperature. This study analyzes such tooth loss. An experimental study and a numerical simulation are conducted of the tooth fixation strength in high temperature environments. The effects of temperature, amount of interference, tooth diameter, and lateral force on the tooth setting strength are studied. The experimental results show that the maximum fastening force is 1149.29 kg and occurs when the tooth diameter is 16 mm at 180 °C and 0.095 mm interference. The strength decreases with an increase in temperature at all three values of interference with a tooth with a 16 mm diameter. At the same temperature, the maximum fastening force is the highest and the deformation of the tooth hole is the least at 0.095 mm interference. Choosing a tooth diameter of 16 mm and 0.095 mm interference is more likely to guarantee the strength of the teeth. The results of the numerical simulation show that the maximum fastening force is highest with a 16 mm tooth diameter and 0.095 mm interference; these values also give the smallest tooth hole deformation at different temperatures. The error between the simulation results and the experimental results is less than 10%; the experimental results verify the correctness of the simulation model.

Study on effect of wheel polygonal wear on high-speed vehicle-track-subgrade vertical interactions

Wheel polygonal wear, as a form of wheel surface damage, is of great concern and potential threat to the deterioration and safety of railway systems. The experimentally measured polygonal wear can be treated as a superimposed wave with different harmonic orders, phases and wave depths, accordingly various frequency components are included. Most of the previous research is focused on vehicle-track vibrations caused by wheel polygon, while its influence on subgrade performance is rarely referred. With this consideration, a vertical model for vehicle-track-subgrade dynamic interactions is established by the Green function method with high accurateness and efficiency. In the numerical analysis, three types of excitations are considered, i.e., the measured polygon, the harmonic polygon and the track random irregularity. Numerical results show that the short wavelength excitation originated from the measured wheel polygon induce high-frequency wheel-rail interactions, which intensify the wheel and rail vibrations and have additional effects on the vibration modes of the displacement and stress curves of the subgrade surface; with the increased polygon order and wave depth, the wheel-rail vertical forces, wheel unloading rates, fastener forces and rail accelerations are significantly exacerbated; the vertical displacement and stress of the subgrade system are mainly affected by the lower orders of wheel polygon.

High efficient dynamic analysis of vehicle–track–subgrade vertical interaction based on Green function method

ABSTRACTA new method is proposed to efficiently simulate vehicle-track-subgrade vertical dynamic interactions based on the Green function method. In this simulation, the vehicle-track-subgrade system is divided into two subsystems, the vehicle-rail subsystem and the slab-subgrade subsystem, which are coupled through fastener connections. In the vehicle-rail subsystem, the vehicle is modelled as a multi-rigid-body system with 10 degrees of freedom, and the rail is simplified as a Bernoulli-Euler beam supported by rail pads. Dynamic equations of the vehicle-rail subsystem are described by differential equations. In the slab-subgrade subsystem, a three-dimensional finite element model is established to obtain the Green functions of the system induced by a unit impulse excitation. Based on the derived Green functions, dynamic equations of the slab-subgrade subsystem are formulated by the Duhamel integral. The interaction between the two subsystems is transferred by the fastener forces, and the dynamic responses of the whole system are solved through explicit numerical methods. The proposed method is subsequently validated through a detailed numerical comparison with the result obtained by the finite element method. Finally, the method is applied to investigate the dynamic property of the subgrade system under high-speed train operation.

Prediction and mitigation of train-induced vibrations of large-scale building constructed on subway tunnel

Among all the recent improvements in the railway industry, ground vibration remains an important showstopper in metropolitan cities. In some particular cases, significant levels of vibration are felt by residents. The role of engineers is to propose mitigation solutions and to ensure that they are efficient in the long-term. This paper presents a numerical study of a large-scale building close to underground networks. A two-step time-frequency prediction method for train-induced vibrations of a superstructure is proposed in this work. In the first step, the spatial train-track coupled dynamic model in time domain is established and then simulated to obtain the vertical and lateral rail supporting forces (fastener forces). In the second step, the discrete Fourier Transform (DFT) of fastener forces are taken as the external loads of a finite element (FE) model of the track-tunnel-soil-building system to solve the building vibrations. On this basis, train-induced vibrations of the large-scale building are predicted under different train operation conditions, and two relevant standards are adopted to evaluate the building vibrations. Further, a base isolation measure, that consists in installing steel springs between the superstructure and the base, is employed to mitigate excessive building vibration. Results show that the underground train and track interaction could result in over-limit building vibrations. The train moving with a higher speed will deteriorate track vibration level and leads to more serious extent of over-limit vibrations of the larger-scale building. The base isolation measure can effectively reduce the excessive building vibrations, and also ensures the train-induced vibrations of the building to satisfy the relevant standard requirements under the worst train operation conditions.