Deceleration Process Research Articles

Vibration characteristics of rolling bearing cage under speed variation conditions

Speed variation conditions will deteriorate the stress state of the rolling bearing internal components and aggravate the vibration of the cage, thereby affecting the service life and reliability of rolling bearings. In this paper, a nonlinear dynamic analysis model of the cylindrical roller bearing is established considering the rubbing effect and hydrodynamic contact between the cage and the guiding ring, as well as the sliding between the cage and other rolling elements. The vibration characteristics of the cage is discussed under the start-stop conditions and different fluctuations of rotation rate. The results show that the vibration of the cage mainly occurs at the middle and late stages of the acceleration process, and the impact mainly occurs at the middle stage of the deceleration process under the start-stop conditions. Moreover, the fluctuation of inner ring speed will enhance the unstable motion of the cage, among which the vibration and impact of the cage are most severe under the rectangular fluctuation of speed, followed by simple harmonic and triangular fluctuations. The findings can provide a theoretical guidance for improving the performance of rolling bearings and ensuring their safe and reliable operation.

Investigations on the near-wall bubble dynamic behaviors in a diverging channel

This study investigates the movement characteristics and causes of the dramatic deceleration of individual bubbles as they enter a diverging channel near the wall, an important phenomenon for understanding fluid dynamics in the Venturi-type bubble generator. The use of a modified volume of fluid model with a user defined source method based on van der Geld’s drag theory improves the accuracy of bubble velocity predictions. Visualization experiments were conducted to observe air bubble motion in water, focusing on deceleration near the wall, while numerical simulations were employed to complement these observations. The results reveal the identification of forces governing bubble deceleration, such as pressure gradient, drag, added mass, and lateral force (lift and wall lubrication). Pressure gradient and added mass forces of magnitudes of 106 N/m3 were found to dominate the deceleration process, with drag and lift forces contributing to bubble acceleration and lateral motion in low-speed liquid flow, respectively. In addition, simulations revealed the formation of a faster-moving liquid region downstream of the bubble during rapid deceleration, highlighting the critical role of added mass on the bubble dramatic deceleration process.

Analysis of the Nonlinear Complex Response of Cracked Blades at Variable Rotational Speeds

The operation of an aero-engine involves various non-stationary processes of acceleration and deceleration, with rotational speed varying in response to changing working conditions to meet different power requirements. To investigate the nonlinear dynamic behaviour of cracked blades under variable rotational speed conditions, this study constructed a rotating blade model with edge-penetrating cracks and proposes a component modal synthesis method that accounts for time-varying rotational speed. The nonlinear response behaviours of cracked blades were examined under three distinct operating conditions: spinless, steady speed, and non-constant speed. The findings indicated a competitive relationship between the effects of rotational speed fluctuations and unbalanced excitation on crack nonlinearity. Variations in rotational speed dominated when rotational speed perturbation was minimal; conversely, aerodynamic forces dominated when the effects of rotational speed were pronounced. An increase in rotational speed perturbation enhanced the super-harmonic nonlinearity induced by cracks, elevated the nonlinear damage index (NDI), and accentuated the crack breathing effect. As the perturbation coefficient increased, the super-harmonic nonlinearity of the crack intensified, resulting in a more complex vibration form and phase diagram.

Improving Pedestrian Safety with Head-Up Display Warning in a Connected Environment

In this paper, the potential of using a head-up display (HUD) in the connected environment to improve a vehicle’s running comfort and pedestrian safety is tested, by providing warning information to drivers in advance. To achieve this objective, driving simulation technology is used to construct the connected environment and develop the HUD, and the effectiveness of the system is then tested. Specifically, thirty-four participants were recruited to conduct driving simulation experiments in six scenarios: three warning display types (Baseline/Head-down display/Head-up display) combined with two weather conditions (clear weather/foggy weather). The effects of the three different warning display types on braking risk-avoidance strategy were studied by comparing the drivers’ performance during the perception and decision stage (position of accelerator-pedal release, position of first braking), the risk-avoidance manipulation stage (maximum deceleration, braking distance) and the risk-avoidance result stage (minimum collision distance, position of minimum speed). The influences of weather conditions and driver attributes were also considered. When the HUD warnings were activated, drivers started to decelerate further away from pedestrians, with a more stable and moderate deceleration process and a greater safety margin between the vehicle and the pedestrians. Using HUD warnings in foggy conditions improved drivers’ perception and decision abilities, this study confirmed the great benefits that HUD warnings in the connected environment can bring to traffic safety, especially under risky situations and inclement weathers. The research results provide a reference for the more humanized and rationalized optimization design of these warning systems.

Simulation on the Effect of Braking Force and Brake Shoe Material Type on The Wear Rate of Railway Bogie Brake Block

The brake block in the railway bogie system is an important component in supporting the operational safety of trains, so it needs to be inspected to determine its performance and service life. A simulation-based study was conducted to predict the wear rate of railway brake block with oriented braking force (F = 25.66 kN - 29.54 kN) and different material types, namely grey cast iron with hardness 170 HBN and metallic composite with hardness 90 HRR. The method of the study was carried out by Finite Element Analysis (FEA) simulation and calculating the wear rate with the Archard wear equation to measure the comparison of the amount of wear volume that occurs on the two materials. The results of the braking ability calculation can be concluded that the different types of brake block materials can affect the ability to decelerate during the deceleration process, causing differences in stopping mileage according to the type of material, such as gray cast iron (μ = 0.30) which has an average mileage of 15 metres and metallic composite (μ = 0.21) has an average mileage of 66 metres. The wear simulation results obtained are that the grey cast iron brake block has an average wear rate of 2,8285e-08 /s which is greater than the metallic composite which is only 1,5391e-08 /s. With this data, it can be concluded that oriented to the braking force load, the metallic composite brake block material has the advantage of a longer service life than grey cast iron.

Investigation on the Influence of Thermal Inertia on the Dynamic Characteristics of a Gas Turbine

In mini-grids and marine-isolated grids, power generation gas turbines are subjected to rapid start-up, shutdown, and acceleration/deceleration. This sudden load change can pose a significant impact on the power grid, severely affecting the operational characteristics of gas turbines. To understand the dynamic characteristics of the gas turbine in the transitional processes, this testing takes twin-shaft medium-sized power generation gas turbines as the test object, and goes through the process of startup, acceleration, deceleration, acceleration, shutdown in one hour, and repeats this process 40 times continuously. With fuel flow as the control parameter and power turbine outlet temperature and high-pressure turbine speed as the controlled parameters, the parameter response rate of the gas turbine under various transition processes is analyzed and the effect of thermal inertia on the gas turbine mass temperature as well as speed is studied. Research findings: During the transition processes, the gas temperature exhibited an axial gradient distribution in the channel. In both the acceleration and deceleration processes, the working fluid temperature gradually decreased along the flow direction. And thermal inertia posed different extents of impact on the dynamic characteristics of the gas turbine under different transitional processes. In the same transition process, the impacts of thermal inertia on the response speeds of temperature and rotational speed varied. The results of this study help to more accurately predict the operating state of the gas turbine during the transition process and lay the foundation for the dynamic simulation model of the non-adiabatic gas turbine.

Fatigue fracture of 316L steel manufactured by selective laser melting method

The kinetics of short cracks in 316L steel samples made by selective laser melting was studied. The structural sensitivity of such cracks, which form on technological defects at the early stage of fatigue is noted. The cracks develop predominantly along the fusion boundaries and slow down their growth at the boundaries of the melt pools. An increase in the crack opening of arrested cracks lead to the formation of a plastic zone at their tips, localization of deformation, a decrease in opening and continued growth with an increase in the number of cycles. The alternation of the processes of propagation and deceleration of short cracks during loading is reflected in the kinetic diagram of fatigue failure which has rate growth thresholds with spacing between them being close to the scanning step during steel manufacturing. The diagram is described by the Paris equation with the same exponent at the growth stage of both short and long cracks. The plotted fatigue curve was compared with fatigue curves for the same material produced by traditional and additive methods. It was shown that the plotted fatigue curve, as well as the fatigue curves for similar materials taken from literary sources, lie much lower than the fatigue curve for the same steel obtained by the traditional method. However, the use of optimal manufacturing modes, as well as subsequent heat treatment, leads to the fatigue characteristics of «additive» steel being similar to those of steels produced by the traditional method. The macro- and microrelief of the fracture surfaces of the samples was studied, the stages of stable and accelerated crack growth were identified, the crack lengths at fracture surfaces corresponding to these stages were evaluated and the predominate fracture mechanisms at each stage were described. It is shown that the observed knee point in the fatigue curve is accompanied by an increase in the damage of the lateral surface of the samples with an increase in the stress amplitude and transition to a more ductile fracture relief, which is explained by the switch from the plane-strain state to a plane-stressed state of the sample material realizing at the tip of the macrocrack.

Simulation calculation and optimization of hydraulic buffer device based on Simulink

Abstract When the hydraulic cylinder moves at high speed to the end of the stroke, it usually produces severe pressure, shock, and vibration, and makes the system very unstable, so the buffer device is often used to buffer the deceleration process of the hydraulic cylinder. In this paper, the cushioning process of a high-pressure hydraulic cylinder buffer device is modeled mathematically, the motion parameters in the cushioning process are calculated based on Simulink, and different structural parameters of the cylinder block are optimized and compared, to study the influence of structural parameters of the cushioning device on the cushioning process.

Modulation of Lipid Dynamics in the β-Amyloid Aggregates Induced Membrane Fragmentation.

Nonspecific membrane disruption is considered a plausible mechanism for the cytotoxicity induced by β-amyloid (Aβ) aggregates. In scenarios of high local Aβ concentrations, a two-step membrane fragmentation model has been proposed. Initially, membrane-embedded Aβ oligomeric aggregates form, followed by membrane fragmentation. However, the key molecular-level interactions between Aβ oligomeric aggregates and lipids that drive the second-stage membrane fragmentation remain unclear. This study monitors the time-dependent changes in lipid dynamics and water accessibility of model liposomes during Aβ-induced membrane fragmentation. Our results indicate that lipid dynamics on the nanosecond to microsecond time scale undergo rapid acceleration upon initial incubation with membrane-incorporated Aβ oligomeric aggregates, followed by a slow deceleration process. Concurrently, lipid headgroups become less accessible to water. Both observations suggest a carpet-like mechanism of membrane disruption for the Aβ-induced membrane fragmentation process.

Topography and accumulation rate as controls of asynchronous surging behaviour in the eastern and western branches of the Western Kunlun Glacier, Northwestern Tibetan Plateau

ABSTRACT The western Kunlun main peak region is among the areas in High Mountain Asia where surge-type glaciers are highly concentrated. Here, we analyse the surging characteristics of the eastern and western branches of the Western Kunlun Glacier and the factors controlling the asynchronous behaviour of their surges. The eastern branch entered an unstable state in 1999 and remained so until the culmination of its surge in the summer of 2019, spanning 21 years. Conversely, the surge of the western branch commenced in the summer of 2020. The surge duration for this glacier was four years, characterized by a rapid acceleration and deceleration process. Based on the glacier surge characteristics, we posit that western branch of Western Kunlun Glacier was influenced by hydrological mechanisms, while eastern branch was affected by subglacial thermal processes. These process intensifies crevasse formation on the glacial surface, providing conduits for surface meltwater to reach the glacier bed, thus elevating subglacial water pressure. The difference of subglacial hydrology and thermal processes caused by different subglacial topography and mass accumulation rates was the main factor of the asynchronous behaviour of the west and east branches of the West Kunlun glacier.

Dynamic analysis of composite flywheel energy storage rotor

Dynamic analysis is a key problem of flywheel energy storage system (FESS). In this paper, a one-dimensional finite element model of anisotropic composite flywheel energy storage rotor is established for the composite FESS, and the dynamic characteristics such as natural frequency and critical speed are calculated. Through the analysis of acceleration transient response, it is found that the flywheel rotor have two critical speeds during acceleration or deceleration process, which are prone to resonance and damage the bearing. Therefore, in order to avoid resonance or reduce resonance peak, the influence of bearing support stiffness, damping and speed-up rate on the critical speed and resonance peak is studied. The calculation results show that the first two order critical speed are affected by the support stiffness. When the stiffness increases, the critical speed of the flywheel rotor increases, but the growth rate decreases. When the damping increases, the critical speed is basically not affected, and the vibration amplitude decreases rapidly. In addition, the resonance peak value of transient response can be effectively reduced by increasing the speed-up rate.

Modular approximate discrete modeling for blisk system with triple closed-loop equivalence method

At present, the lumped-parametric model is often used in the preliminary design of bladed disks. However, the lack of systematic modeling methods leads to high errors. In order to develop the systematic modeling method and improve the equivalence accuracy, this paper considers the comprehensive equivalence from the aspects of natural characteristics, transient forced responses, and steady-state forced responses under aerodynamic excitations. This paper includes two novelties. First, based on the modular equation of blisk system, an approximate discrete model is derived for computational efficiency. Second, a triple closed-loop equivalence method with modal weight optimization is developed innovatively for optimal equivalence parameters. The method can significantly improve the accuracy of element parameters in the lumped-parametric model and achieve the comprehensive equivalence to actual blisk. Compared with the existing equivalence method, the average errors of natural frequencies in the whole mode interval and in the high-density mode interval are reduced by 41.75 % and 36.76 %, respectively. The maximum and average displacement errors of the transient response are reduced by 51.76 % and 58.98 %, respectively. Furthermore, vibration characteristics of the mass and stiffness mistuned blisks are analyzed under traveling wake excitation during acceleration and deceleration processes by approximate discrete model and determined parameters.

Experimental investigation of time-dependent electrical load effects through multipoints in-situ measurement of temperature and relative humidity of PEMFC bipolar plate under transient operation

In this study, multiple micro-relative humidity and temperature (RH/T) sensors were installed in the anode and cathode channels of a proton exchange membrane fuel cell (PEMFC) bipolar plate to simultaneously observe and analyze the variation in RH/T behaviors during transient operation. In order to simulate the acceleration and deceleration process, the electrical load was ramped from 10 to 40 A and then back to 10 A, with time intervals of 0, 2, and 5 s. The data corresponding to different acceleration/deceleration time intervals were compared and analyzed to assess the time-dependent effects of load changes. The analyzed data provide visual information, including the transient voltage response, transient behavior of temperature and water distribution, and evolution of RH/T within PEMFC. The results indicate that the acceleration and deceleration interval times significantly influence the temperature and water distribution within PEMFC during transient operation. Shorter acceleration times lead to more rapid changes in temperature and humidity within the PEMFC active area, resulting in higher transient temperature and water concentration. This finding explains why the output voltage decreases more when the load changes with a short time interval. This research enhances our understanding of transient temperature and water behavior, providing a foundation for further research and development of effective operational strategies and vehicle PEMFC designs.

High flux strontium atom source

We present a novel cold strontium atom source designed for quantum sensors. We optimized the deceleration process to capture a large velocity class of atoms emitted from an oven and achieved a compact and low-power setup capable of generating a high atomic flux. Our approach involves velocity-dependent transverse capture of atoms using a two-dimensional magneto-optical trap. To enhance the atomic flux, we employ tailored magnetic fields that minimize radial beam expansion and incorporate a cascaded Zeeman-slowing configuration utilizing two optical frequencies. The performance is comparable to that of conventional Zeeman slower sources, and the scheme is applicable to other atomic species. Our results represent a significant advancement towards the deployment of portable and, possibly, space-based cold atom sensors.

A28: Biomechanical Analysis and Research in Rugby Speed Training

Purpose: Speed training is an essential and important part of rugby. Usually in confrontational events, strength will have a powerful effect, but good speed will be more than that plus works. Rugby speed drills can be complex or simple things that coaches choose. To the best of the speed required depends on the position, but every player on the field can be trained to get faster. Methods: Through the literature method, logic analysis and other related analysis of sports biomechanics of speed training in football, in order to provide some theoretical basis and reasonable suggestions for speed training, to improve the efficiency of speed training in football to make a contribution. Result: One of the most common scenes in football is when players speed up and slow down over and over again. Acceleration on the field can take many forms. Acceleration relies more on the quads and running at top speed relies more on the hamstrings and hip flexors. Acceleration depends on the strength of the buttocks, quadriceps, calves, and upper body (especially the anterior deltoid tract). Absolute strength, relative strength and running technique are also important. The process of deceleration is accomplished through centrifugal contraction of the legs, which creates the muscle elasticity to counter and mitigate impact and is a key element in the ability of athletes to perform rapid deceleration. To cushion such an impact, explosive force is absolutely essential, and the knee and hip joints also require a certain amount of flexion to effectively cushion the impact, a movement similar to the landing technique. But in actual speed training situations, a different scenario can occur, and many coaches directly relate disadvantage factors. Conclusion: First, speed training programs must be designed to meet the bioenergetic and biomechanical requirements encountered by athletes during competition and practice. Each position on the field needs to differentiate the composition of the training load to meet the different requirements that these players must meet during the game. Secondly, we should closely monitor the amount and time of speed training according to the actual situation and focus on the recovery of the body. Coaches should avoid the urge to rush, as athletes may practice incorrect sports biomechanics when they are tired. Finally, the coach should analyze the limiting factors of the disadvantageous elements, train the limiting factors of plasticity, and finally achieve the goal of improving the disadvantageous elements.

Approximate calculation of static mass analyzers based on two-dimensional fields

The concurrent utilization of electric and magnetic fields in static mass analyzers proves highly effective in sparticle separation solely based on their masses, thereby ensuring remarkable analytical capabilities. High-resolution mass analyzers employ an achromatizing electrostatic system to precisely focus ion radiation by energy. Devices featuring zero energy dispersion are created through the collaborative action of electric achromatizing systems and the magnetic field within the analyzer, resulting in ion separation based solely on mass. Expanding the ion beam prior to its magnetic field exposure enhances the overall quality of static mass analyzers. This article delves into a static mass analyzer with dual ion beam focusing, elucidating the ion acceleration and deceleration processes at electrode boundaries, their focalization via a transaxial lens, and the impact of the electrostatic prism's refractive surface on the mass analyzer's "quality" parameter. Additionally, the transition from a sector homogeneous magnetic field to the fields generated by a two-dimensional magnetic prism and a three-electrode transaxial focusing lens is explored to augment the mass analyzer's linear dispersion. To refine ion beam focus pre-magnetic field entry, the proposed adoption of a two-dimensional electrostatic prism promises heightened linear dispersion in the mass analyzer while expanding the beam pre-magnetic field entry. This study also examines the impact of a two-dimensional electric prism on the charged particle beam, presenting an approximate expression for its angular energy dispersion. It is demonstrated that a prism-based mass analyzer integrating two-dimensional electric and magnetic prisms enables energy-focused operations alongside enhanced linear dispersion and reduced linear dimensions.

SUBSTANTIATION OF THE ANOMALIES OF THE MEASUREMENT RESULTS FOR TRAJECTORIES OF GRAVITATIONAL MANEUVER OF SPACE VEHICLES

In astronomical research, the problem of measuring the trajectories of the gravitational maneuver of space vehi- cles in the gravitational field of large celestial bodies arises. The known measurement results differ from those predicted by classi- cal celestial mechanics. A practical solution to this anomaly is possible only based on an adequate mathematical model. For this purpose, we have adapted Newton’s law of universal gravitation to the case of moving masses in a possible range of speeds in flat space and physical time. At the same time, the finite speed of propagation of the gravitational field is taken into account. The dif- ferential equations of motion of cosmic bodies have been obtained. In the heliocentric and planetocentric coordinate systems, tran- sient processes in the cosmic three-mass system are simulated – star, planet, and man-made spacecraft (Sun-Mercury-space probe). To more deeply identify the essence of gravitational interaction, transient processes of both acceleration and deceleration of the space vehicle were simulated depending on the specified space-velocity initial conditions for the differential equations of motion. The results of the simulation of transient processes are attached.

Experimental research of novel true triaxial hydrothermal phase change impact fracturing

When extracting coal-bed methane (CBM) from deep ground, conventional hydraulic fracturing struggled to expand fractures due to both inadequate pressure and the water-lock phenomenon, while burgeoning fracturing techniques were unable to provide both high pressure and impact stress. The hydrothermal phase change impact fracturing technology can instantaneously discharge high-pressure thermal fluid and generate impact stress to volumetric fracturing. In order to research the fracturing mechanism of the new fracturing strategy, a separately designed experimental system was utilised for high-pressure thermohydraulic fracturing at different release pressures and different peripheral pressures. The experimental findings: (1) The pressurisation profile in the reactor was divided into five stages: accelerated reaction process, reaction homogeneity process, deceleration process, pressure relief shock stage and residual pressure seam formation process; (2) High-pressure hydrothermal fracture produces both radial and tearing cracks, with radial cracks being the main cracks; (3) The dimension of the fractal can be used as a damage variable to describe both the fracture morphology and the degree of damage.

What ADS-B Data Can Tell Us About HL7525(KAL631) Accident at the CEBU Airport

This research aims to extract useful information from the HL7525 accident ADS-B data archive. The approach used is Exploratory Data Analysis (EDA), which ensures that the ADS-B data quality standards must be met and visualizes the landing position or touchdown, altitude, and speed data, which is then compared with the flight rules for the landing phase. These criteria are based on three important characteristics that ensure the aircraft does not overrun: touchdown point, touchdown speed, and deceleration after touchdown. Data analysis revealed that the stored ADS-B HL7525 data had good data quality, falling within the ICAO standard (tier-1) for 82% of the total data, meaning that this data was 82% representative of the actual environment. In addition, it was found that the aircraft attempted three landings, with the first and second attempts showing the go-around procedure, and the third attempt (the final attempt) landing successfully but ending in an accident. Based on the analysis results, two of the landing criteria were met even though the slope angle exceeded 30, and the third criterion was not met because the deceleration process after touchdown was not in accordance with the procedure.

Hybrid electric vehicles and regenerative braking

With the rapid development of the automotive industry, the fossil fuel crisis and environmental pollution issues have become increasingly severe. The demand for low energy consumption and low emissions has become an inevitable trend in automotive development. Hybrid electric vehicles effectively address the issues of driving range and emissions reduction, making them an important branch of new energy vehicle technology. Electric vehicles have long faced the challenge of limited driving range, particularly in urban driving conditions with frequent start-stop processes. This study focuses on new-energy electric vehicles and proposes an energy recovery control strategy for regenerative braking. Considering various related influencing factors, the strategy accurately allocates the regenerative braking force of the drive motor during vehicle coasting, deceleration, and braking processes. This improves the energy recovery efficiency of the vehicle while ensuring driving safety. This article introduces the operating principles and classification of hybrid electric vehicles and provides an overview of the regenerative braking technology in current hybrid electric vehicles.