Processing and fiber content effects on the machinability of compression moulded random direction short GFRP composites

The random direction short Glass Fiber Reinforced Plastics (GFRP) have been prepared by two compression moulding processes, namely the Preform and Sheet Moulding Compound (SMC) processes. Cutting force analysis and surface characterization are conducted on the random direction short GFRPs with varying fiber contents (25∼40%). Edge trimming experiments are preformed using carbide inserts with varing the depth of cut and cutting speed. Machining characteristics of the Preform and SMC processed random direction short GFRPs are evaluated in terms of cutting forces, surface quality, and tool wear. It is found that composite primary processing and fiber contents are major contributing factors influencing the cutting force magnitudes and surface textures. The SMC composites show better surface finish over the Preform composites due to less delamination and fiber pullouts. Moreover, matrix damage and fiber protrusions at the machined edge are reduced by increasing fiber content in the random direction short GFRP composites.     

Reliability and safety analysis methodology for identification of drivers’ erroneous actions

Owing to significantly individual differences in everyday driving behavior, it is quite difficult to assess the relative importance of driver errors compared with vehicle faults or road environment anomalies. This paper briefly presents several basic concepts for analysis of driving dependability including driving errors, driving reliability, driver recovery from erroneous actions, and key factors that shape driving behavior. This presentation is followed by construction of a shaping architecture for driving behavior that consists of a perception stage, a decision-making stage, an execution stage and correlativity among stages, in addition to internal feedback from complex traffic states. The causation classification of driving errors is then discussed in the context of three elemental types: perception error, decision-making error and execution error. The emphasis of this paper is on how to quantify driving dependability in order to identify various erroneous driver actions during traffic accidents. Specifically, this paper proposes a methodology to measure the probability of driving errors by considering the driver recovery from erroneous actions. The purpose of model-based driving dependability analysis is to quantitatively and qualitatively analyze the relationship between driving errors and traffic accidents causations.     

Low cost design of parallel parking assist system based on an ultrasonic sensor

This paper presents a low cost design and implementation of a parallel parking assist system (PPAS) based on ultrasonic sensors. Generally, a PPAS requires several types of sensors, such as an ultrasonic sensor, camera sensor, radar sensor and laser sensor for parking space detection. However, our proposed PPAS only requires two ultrasonic sensors on the front and lateral sides for parking space detection. Moreover, a steering angle sensor and wheel speed sensor installed in the vehicle are used to obtain vehicle position information for localization in ultrasonic range data. The hardware architecture of the PPAS based on an electronic control unit (ECU) module, sensor modules and a human machine interface (HMI) module was proposed. Moreover, the software architecture of the PPAS is based on system initialization, scheduling, recognition and a control algorithm. In particular, a novel sensor algorithm was proposed to minimize the vehicle corner error of the ultrasonic sensor. A prototype of the PPAS based on the proposed architecture was constructed. The experimental results demonstrate that the implemented prototype is robust and successfully performs parking space detection and automatic steering control. Finally, the low cost design and implementation of the PPAS was possible due to the cheap ultrasonic sensors, simple hardware design and low computational complexity of the proposed algorithm.     

Analysis of an automotive ground system based on its steady-state model

As more electrical equipment is installed and larger currents are required in vehicles, the automotive ground system becomes more important to guarantee the stable operation of the equipment and efficient power consumption. In this paper, an automotive ground system is analyzed in a steady-state condition, and a simulation model for estimating its ground voltage distribution is described. The automotive ground system is divided into an engine compartment ground and a body ground, and it is modeled as an equivalent resistor network, which is suitable for simulation. By using the developed model, ground voltages are simulated and measurements are taken with a real car. A comparison of the simulation and measurement results shows good agreement, and the validity of the model is confirmed. Then, the factors that dominate the ground voltage level are discussed.     

Digital human body model for seat comfort simulation

Using the recent anthropometry of the North American population, human body models were developed for seat comfort simulation. The external geometry of the models was acquired from the three-dimensional whole body laser scan of recruited volunteers in a driving position. The selection criteria for volunteers with standard size and shape were derived from a statistical factor analysis of the Size USA database. As a practical application of the model in a design process, comfortable driving postures were constructed by adopting the cascade prediction model (CPM), which takes into account both interior package layout and the driver’s anthropometry. The detail modeling process of finite element modeling and its validation results against volunteer measurements are introduced.     

桩底土与桩相互作用的模型试验研究

选用黄河砂子、南疆盐渍土作为桩底土进行桩土相互作用的模型试验,应用回传射线矩阵法对不同压实状态下桩底土的刚度系数和阻尼系数进行拟合,建立桩顶反射速度波幅与入射速度波幅比随时间、阻尼系数和刚度系数的变化关系式.试验结果表明:土越密实,桩底刚度系数就越大,实测桩顶速度波时程曲线就越往下倾斜;桩底土层的分层层数和分层厚度对反射波产生很大影响.     

Impacts of built environment and emerging green technologies on daily transportation greenhouse gas emissions in Quebec cities: a disaggregate modeling approach

This paper aims to investigate the impact of the built environment (BE) and emerging transit and car technologies on household transport-related greenhouse gas emissions (GHGs) across three urban regions. Trip-level GHG emissions are first estimated by combining different data sources such as origin–destination (OD) surveys, vehicle fleet fuel consumption rates, and transit ridership data. BE indicators for the different urban regions are generated for each household and the impact of neighborhood typologies is derived based on these indicators. A traditional ordinary least square (OLS) regression approach is then used to investigate the direct association between the BE indicators, socio-demographics, and household GHGs. The effect of neighborhood typologies on GHGs is explored using both OLS and a simultaneous equation modeling approach. Once the best models are determined for each urban region, the potential impact of BE is determined through elasticities and compared with the impact of technological improvements. For this, various fuel efficiency scenarios are formulated and the reductions on household GHGs are determined. Once the potential impact of green transit and car technologies is determined, the results are compared to those related to BE initiatives. Among other results, it is found that BE attributes have a statistically significant effect on GHGs. However, the elasticities are very small, as reported in several previous studies. For instance, a 10 % increase in population density will result in 3.5, 1.5 and 1.4 % reduction in Montreal, Quebec and Sherbrooke, respectively. It is also important to highlight the significant variation of household GHGs among neighborhoods in the same city, variation which is much greater than among cities. In the short term, improvements on the private passenger vehicle fleet are expected to be much more significant than BE and green transit technologies. However, the combined effect of BE strategies and private-motor vehicle technological improvement would result in more significant GHGs reductions in the long term.     

端面转角对板架结构极限强度的影响研究

文章以单层板架、开孔单层板架和双层板架为研究对象,采用非线性有限元法,开展了端面转角对板架结构极限强度的影响研究。首先对单层板架、开孔单层板架和双层板架在不同端面转角下的极限强度进行了系列数值计算,然后对比分析其极限载荷和失效模式,获得了端面转角对板架结构极限强度的影响规律,为开展甲板板架结构极限强度试验提供方法参考。     

机动航态下水中航行器边界层特征参数计算建模研究

文章基于边界层积分求解理论,进行了机动航态下水中航行器厚边界层计算建模,发展了求解动量积分方程组的数值计算方法。编写了相关计算程序。针对SUBOFF潜艇,利用编写的程序,计算得到了边界层特征参数沿艇体分布的曲线,分析研究了机动航态下边界层特征参数变化规律。结果表明,编制的计算程序可用于机动航态下水中航行器边界层特征参数计算分析,为水中航行器水动力性能评估提供技术支持。     

Study of Controlling Measures for Existing Railway Deformation Caused by Metro Shield Tunnel Under-passing Construction北大核心CSCD

Based on the background of the first phase project of the R3 line of Jinan Rail Transit, and in view of the metro shield tunnel passing under the existing railway bridge and subgrade, this paper uses Abaqus to establish a numerical model to simulate the deformation of the existing bridge and subgrade of the Jiaoji railway line under the two conditions of non-active reinforcement and reinforcement. The results show that under the condition of no reinforcement, the maximum settlement of the top bridge on the pier is -5.88 mm, and the maximum settlement difference is 5.16 mm, which exceed the deformation control requirements of the 5 mm regarding the bridge pier of the railway with ballast track. The maximum lateral displacement and longitudinal displacement of the pier are 0.28 mm and -3.01 mm, respectively. After the reinforcement measures of the bored piles are adopted, the maximum settlement of the top bridge on the pier is -1.71 mm, and the maximum settlement difference is 1.16 mm, which fully meet the bridge pier deformation control standard. The maximum lateral displacement and longitudinal maximum displacement are -0.245 mm and -2.83 mm, respectively, which meet the requirements of the control standard. The vertical settlement of the railway subgrade is relatively small. The maximum settlement values under the two working conditions are -12.31 mm and -11.97 mm, respectively, which meet the subgrade settlement control requirement of 20 mm. It is proved that the reinforcement effect of the bored pile is good, and the reinforcement scheme is safe and feasible. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.