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The flexspline features several modal characteristics that are related to its structural parameters, which could impose an impact on the stability and reliability of the system of harmonic gear transmission. In this article, we have integrated the method of orthogonal design with the approach of finite element, so as to study the modal characteristics of flexspline under varying structural parameters. Furthermore, we have analyzed the ways of how varying structural parameters could impose an impact on the first eight-order natural frequencies of flexspline. In addition, by adopting the method of range and variance analysis for the obtained data, we have examined the influence imposed by varying structural parameters on the modal characteristics of flexspline, which could lay a foundation for the optimal design of the structural parameters of flexspline.

The flexible gear is the key parts of harmonic gear reducers,and its performance directly determine the overall condition of harmonic drives. In order to seek the basic law of influence of flexible gears wall thickness on its performance to make use of the law,the influences of flexible gears wall thickness on stress and deformation of the flexible gears are simulated and analyzed by ANSYS Workbench software under no-load and load conditions. The results show that,the maximum stress of the flexible gear increases and the maximum deformation decreases with the increase of the wall thickness under no-load condition. With the increase of the wall thickness,under the load condition,the maximum stress decreases overall and the maximum deformation decreases first and then tends to be gentle. Under the same wall thickness,with the increase of the load,the maximum stress and the maximum deformation both enhance and the load is more sensitive to the deformation in the places whose wall thickness are relatively thinner. Under the same conditions,the stress of flexible gear with bottom modification is smaller. This law can provide some reference for researchers.

The calculation of harmonic gear meshing stiffness is the basis of dynamics analysis. According to the finite element analysis theory of loading contact,and combining with its static and dynamic contact properties,taking each different location during one engaging-in and engaging-out cycle of a tooth as the research object. Then,by extracting the meshing data of discrete point on contact location,the curve of single-tooth stiffness and the synthesizing meshing stiffness in one engaging-in and engaging-out is got. Comparing with the previous researching result,the correctness of the method is verified,which provides the basis for dynamics analysis for harmonic gear.

In view of the stress of flexspline calculated on the basis of the theory of thin-walled cylinder,there are many assumptions of the theory,which will lead to the difference between the calculated value and the actual value. Considering the boundary constraint and force,from theoretical model to actual model,six analysis model are constructed based on the geometric model of flexspline to research the difference between theoretical and actual by finite element method. The result of analysis indicate that the maximum value appears in the gear root which is close to the cup bottom of flexspline,and accompanying the transition from theoretical model to actual model,the stress of all direction is increased gradually,which the circumferential stress has a larger increasing range. The reason of that is the stress concentration caused by the boundary constraint.

The radial deformation is one of the important parameters that affect meshing characteristic and the life of flexspline in harmonic reducer. Based on envelope meshing theory of harmonic drive,the influence of radial deformation on meshing characteristic of harmonic drive is analyzed. The finite element method is used to obtain the stress distribution of the flexspline. The results show that the radial deformation has significant influence on the meshing track,the radial deformation of the flexspline,the tangential deformation,the rotation angle in normal direction,the bending stress and the tangential stress of the flexspline. The result of the flexspline stress distribution from theoretical calculation has good consistent with the result from finite element analysis.This can provide some reference for the choosing of reasonable radial deformation to improve meshing performance and life of flexspline.

The inherent characteristics of the high speed shaft and the unbalance response of the high speed shaft seriously affect the operating condition and service life of the high speed gearbox. For the high speed gear shaft,a multi distribution model of the system is established. The natural frequency and the unbalance response of the shaft are analyzed by using the transfer matrix method. The unbalance response of the shaft at different speeds and different eccentric quality is obtained with the same method. The unbalance response of the gear meshing point is investigated through the analysis of the unbalanced response characteristics in various cases,and the working conditions of the gear meshing point are analyzed,and the basis for the design and manufacture of high speed gear box is provided.

In order to have a better research on the effect factors of the vertical axis wind turbine wind-energy utilization coefficient,based on the multi-blade element momentum theory a Double Disk Multi-tube Model was established,and through mathematical modeling method to focus on the influence of chord length,radius and number of blades. Because of the loading on the wind turbine during rotation was complex,the rotation plane was divided into four quadrants,and put forward the fourquadrant analysis method on the basis of the original theory,then established the simulation model based on the analysis of stress. Finally,in view of the NACA0018 airfoil,study respectively in different chord length,impeller radius and number of blades using the four-quadrant analysis method,the change of vertical axis wind turbine wind-energy utilization coefficient,which provides a reference for the selection of fan impeller parameters.

Ti-Al-based alloys, particularly two-phase TiAl and Ti3Al alloys, have garnered significant attention as potential replacements for various high-temperature structural materials due to their exceptional properties, including low density, oxidation resistance, and high strength at elevated temperatures. Despite these advantages, experimental studies on the microstructure evolution of Ti-Al-based alloys under complex conditions remain challenging to observe and characterize. This review article examines the current research on molecular dynamics (MD) simulations of Ti-Al-based alloys, focusing on two-phase Ti-Al alloys, Ti-Al amorphous alloys, Ti-Al composite materials, and the welding and multi-layer/film applications of Ti-Al alloys. This review highlights the unique capabilities of MD simulations in predicting the behavior of Ti-Al-based alloys and addresses existing scientific challenges. Furthermore, this article discusses future research directions and development prospects in this field. [ABSTRACT FROM AUTHOR]

Pavement condition monitoring is an important task in road asset management and efficient abnormal pavement condition detection is critical for timely conservation management decisions. The present work introduces a mobile pavement condition monitoring approach utilizing low-cost sensor technology and machine-learning-based methodologies. Specifically, an on-board unit (OBU) embedded with an inertial measurement unit (IMU) and global positioning system (GPS) is applied to collect vehicle posture data in real time. Through a comprehensive analysis of both time domain and frequency domain data features for both normal and abnormal pavement conditions, feature engineering is conducted to identify how the most important features affect abnormal pavement condition recognition. Six machine learning models are then developed to identify different types of pavement conditions. The performance of different algorithms and the significance of different features are then analyzed. Moreover, the influence of vehicle speed on pavement condition assessment is further examined and classification models for different speed intervals are developed. The results indicate that the random forest (RF) model that considers vehicle speed achieves the best performance in pavement condition monitoring. The outcomes of the present work would contribute to cost-effective pavement condition monitoring and provide an important reference for pavement maintenance sectors. [ABSTRACT FROM AUTHOR]

Truck's climbing performance is an important consideration in traffic safety, efficiency, and highway geometric design. With the infrastructure development in high-altitude area in China, more attention needs to be paid on truck's climbing performance in such area. In this article, truck's climbing speed in high-altitude area was examined through field tests on different grade sections at different altitudes. Truck's speed-distance curves were built at different altitudes and the impact of altitude on truck's climbing speed was explored based on the test results. It was shown that, within the altitude range of 3000~5000m, altitude had an obvious influence on test truck's decelerating and accelerating performance. Truck's speed decreased faster on steep grades and increased slower on gentle grades with the increase of the altitude. Also, the stable speed that test truck could maintain on a certain grade was lower at a higher altitude. In addition, test truck's theoretical speed-distance curves at the sea level were estimated through truck's dynamic model. Compared with the theoretical crawl speed, a negative effect of altitude change (from 0 to the altitude above 3000 m) was found on truck's climbing performance., 1. Introduction Trucks are an important component of highway traffic. Due to their physical and operational characteristics, they can significantly influence traffic system performance, safety, and the travel experience of [...]

We investigated the effects of four safety facilities in expressway tunnels--information boards, flashing lights, human-voice broadcasts, and siren broadcasts--on driver distance perception by questionnaire surveys and field experiments. Results from a survey questionnaire given to 436 drivers indicated that each of the facilities, except the human-voice broadcast, was perceived to increase the driving safety. Consistently, results from field experiments involving 150 participants in China's Xingshuliang Tunnel indicated that information boards, flashing lights, and siren broadcasts increased the distance perception accuracy of drivers, while human-voice broadcasts decreased this accuracy. The results of human-voice broadcasts may be due to the fact that drivers could not catch and understand the information they heard from human-voice broadcasts while driving in tunnels. This research can assist engineers in identifying the effective safety facilities in tunnels and provide a basis for prioritizing the implementation of these facilities, ultimately increasing driver distance perception accuracy and decreasing rear-end collisions., 1. Introduction Expressway tunnels play an enormous role in transportation systems to make travelling convenient and fast; however, the constantly increasing tunnel accidents become a big problem for the safety [...]