Key Engineering Materials Vols. 579-580

Abstract: Electrorheological fluid (ERF) is a new kind of smart materials, which has a great deal of market value and broad application prospects. To meet the needs of the ERFs performance testing, design and produce of the ERF's performance test system are based on the relationship of the apparent viscosity, shear stress and electric field strength. Select the NDJ-8S digital viscometer, high voltage DC power supply, liquid container, and other parts to constitute the ERFs performance test system after considering the relationship of the apparent viscosity, shear stress, shear rate and electric field strength. The system has potentials to control voltage, change velocity, change the distance between the parallel panels, and test the yield stress of the ERF, shear stress, viscosity and other parameters. The study introduces the hardware and software device, the related experiments, and obtains the relationship of the viscosity, rotational speed, voltage, and plate gap.

Abstract: The disturbance torque which is caused by the interference of the motor position has observably impact on accuracy of the loading system. According to unstable loading channel and disturbance torque, this paper use a complex control algorithm of differential forward PID control and feed-forward compensation. At the end of this paper, the simulation analysis results show that the feed-forward compensation can observably eliminate the influence of the disturbance torque, and improve the accuracy of the loading system.

Abstract: According to the voltage balance equation, the paper deduces the mathematical model of BLDCM on the basis of analyzing the operation principle. In SIMULINK environment, the BLDCM ontology module is built by adopting the combination of BLDCM state equation with S function method. The built motor ontology module proves to be accurate and reasonable through the analysis of the simulation waveform, which helps to analysis BLDCM electronic commutation, etc. Again taking LM621N as commutation control chip, using PIC microcontroller output variable frequency square wave, and through external input device to adjust the square wave frequency, thus realizes the control of motor speed. A brushless dc motor drive with circuit protection functions is designed by the method of combining hardware and software. Not only the motor work situation of ontology is intuitively reflected, and the development cycle is shorted.

Abstract: To make appropriate rehabilitation decisions, determining subgrade modulus of the existing semi-rigid asphalt pavements is a crucial task for highway engineers. Falling Weight Deflectometer (FWD), as a nondestructive testing technology, is an effective tool to determine subgrade modulus. The objective of this study was to establish a method to predict subgrade modulus of asphalt pavements based on Falling Weight Deflectometer. With the basic theory of structure dynamics, the finite element model of the asphalt pavement was established to generate a synthetic database of surface dynamic deflection basin parameter (DBP) indicators. Then, the relationship between DBP indicators and subgrade modulus was discussed and the prediction function for determining subgrade modulus was established. The analysis results demonstrate that subgrade modulus can be predicted by the direct deflection indicator d₉, shape indicator F₈ and structure layer thickness and the predicted precision is satisfied. The relative error between the theoretical value and the predicted values ranges from-13.2% to +15.56% according to subgrade modulus. The mean value of absolute relative error is 2.36%. The research results provide a technology supports to popularize FWD testing technology applied in performing subgrade structure performance evaluation.

Abstract: The paper has first built the vehicle-borne computer sensing integration testing system experiment platform, through the actual road test experiment, collects the different mobile vehicle the operating condition data and emission data, has constructed the different vehicle instant exhaust emission rate and database of vehicles driving cycle-based data correspondence, Establishes the driving cycle and road grade power density microscopic emission model. Uses the typical path roundabout crossing as an example, the paper carries on the power density computation through microscopic simulation software numerical simulation output roundabout crossing region vehicle bicycle the real-time speed, acceleration and other travel data, combined with the previous microscopic emission model of building, calculates the instantaneous mass emission rate and vehicles total emission of roundabout crossing different vehicles pollutant gas. According to the result of software simulation and numerical computation, the paper effectively appraises the regional road roundabout pollution emitted by vehicles, has verify the validity of the in-vehicle computer sensor integration testing and emission assessment model, provide a reference for seeking to solve regional traffic roundabout environmental pollution testing methods and effective assessment.

Abstract: With the increasingly outstanding of the traffic safety issue, the human factors in People-Vehicle-Road System are being emphasized gradually. Takes Jinhua suburb asphalt mountain road (two-lane, multiple steep slopes) for example, this study focuses on road engineering response analysis on driving reaction, design optimization of road engineering base on driving response. A driver over 3 driving years steered 5-seat car in 4 kilometers long experimental road, kept the vehicle speed (V) under 40km/h. Heartbeat rate of the driver was monitored by dynamic Holter through driving process. The analysis shows that there is a linear positive correlation between Heart beat growth rate (Ni) and V, a nearly positive correlation between lateral force coefficient (μ) and Ni, and nearly inversely proportional between plane curve radius (R) and slope (i). It should decrease R appropriately when road slope (i) much sharply in road alignment design. There is a polynomial relation between Ni, V and R. As R increases, both Ni and V reduce firstly, and then rise. When R ranges from 240 to 500 meter, stress gradually ease; while R exceeds 500 meter, driving reaction tension gradually rise. R<550 m, i <6% and slope length under 300 m in the experimental road. When instructional speed <40km/h, then Ni was 30.2% and μ was 0.25. Its benefit for driving safety to keep drivers in appropriate tension in such situation.

Abstract: According to the numerical simulation of femoral injury, this paper created femoral finite element model from medical image of CT scan, simulated the deformation and stress distribution of femur under complex stress, explored the application of digital bone scientific for femoral injury, analyzed the characteristics of stress distribution on bone under complex loads with the medical image reconstruction technology and the finite element numerical simulation technology, and it can play a guiding role in the research on the injury mechanism of femur under complex loads.

Abstract: With vehicle population increase, urban trunk traffic flows augment significantly. Traffic environmental problems are become progressively severe challenge, such as congestion, emissions, and photoacoustic pollution. In view of exhaust pollution diffusion problems in urban trunk intersection, this article took North Bayi Street - South Bayi Street in Jinhua as case, carried out traffic surveys of trunk along, tested vehicle exhaust pollutants concentration of intersections, analyzed the exhaust diffusion characteristics of trunk along during the early peak, evening peak and working hours on workday, and proposed relevant emission control measures. Traffic flow in this urban trunk was about 860-3060 pcu/h, and CO was the main pollutant in the exhaust emissions. CO and NO₂ diurnal variation ranges were 3.23-14.2ppm and 0.1-0.71ppm. Intersection 4 (South Bayi Street - West Shuangxi Road) with the maximum average concentration of exhaust pollutants along trunk, diurnal variation of peak period were distributed in morning, evening and noon hours, and the evening peak was the maximum. Under the same conditions, exhaust pollutant concentration raised with the traffic increasing in a linear positive correlation. Traffic management measures could control vehicle exhaust diffusion concentration and spread range in the intersection, such as using new clean energy, improving existing fuels, bettering whole road network emissions, and increasing the green rate around intersections.

Abstract: In this paper, the process of laser transmission joining (LTJ) of polycarbonate (PC) and polyformaldehyde (POM) which are thermoplastic plastics is investigated through a finite element (FE) simulation. Firstly, a 3D thermal model is developed with a moving Super-Gaussian heat source based on the ANSYS parametric design language APDL and the distribution of the temperature field is obtained. Then the effect of process parameters namely laser power, scanning speed and spot diameter on the joint width is analyzed. At the same time, the calculated joint width is achieved. Finally, the curves of calculated results are compared with the curves of experimental results. The comparison shows a good agreement between them which shows that the FE model is reliable. This lays the foundation for reducing experimental times, designing of experiments based on FE simulation and optimizing process parameters.

Abstract: In order to calibrate subgrade back calculation modulus, the correction method of subgrade back calculation modulus was put forward based on theoretical analysis and indoor/outdoor experiments, and the detailed implementation process was analyzed combined the latest results of subgrade dynamic modulus and subgrade moisture forecast. The results show that the equivalent resilient modulus of subgrade simultaneously consider subgrade material moisture condition and stress dependency and the forecast equation has higher correlation. The ratio of the loading plate test results to the predicted results ranges from 0.25 to 0.4 and the mean is 0.32, which conforms to the requirements of AASHTO normal value. Utilizing the scale factor 0.65 to calibrate subgrade back calculation modulus is viable and validated. The results provides a new perspective and approach for deformation analysis of subgrade structure. As well, the established method makes up the defect that can't reflect the effect of moisture and stress on equivalent resilient modulus of subgrade.