Optimizing the shape of a bumper beam section considering pedestrian protection

This paper presents a design technique to optimize the shape of a vehicle bumper beam that satisfies both the safety requirements for a front rigid-wall impact and the regulations protecting pedestrians from lower leg injuries caused by bumper impacts. An intermediate response surface modeling (IRSM) technique was introduced to approximate the non-linear force-displacement curves obtained from the front impact analysis of a vehicle bumper. The accuracy of the IRSM model was tested by comparing its results with those of the non-linear finite element analysis. The maximum displacement error between the two models did not exceed 3%. Using pedestrian impact analyses based on the experimental arrangement of the Plackett-Burman design, the approximate functions describing the response values acting on the lower legs were calculated. The shape of the bumper beam was optimized by integrating the IRSM with the force-displacement model and the approximate functions on lower leg impact. The optimization results satisfied safety regulations on the maximum allowable displacement of the vehicle bumper, and also the regulations protecting pedestrians from lower leg injuries caused by bumper impacts.     

Mitigating the effect of impact loading on a vehicle using an essentially nonlinear absorber

The aim of this study is to investigate the ability of an essentially nonlinear vibration absorber to mitigate the large accelerations transmitted to a passenger compartment of a vehicle which is subjected to shock-type transient loading at the chassis. For such problems, the induced vibration typically attains its maximum value shortly after the application of the loading; thus, it may be impossible to dissipate a major portion of the input energy prior to the occurrence of the peak response. Here, a class of absorbers possessing a form of discontinuous essential stiffness nonlinearity is employed to achieve the desired mitigation. In this paper, we apply a single vibro-impact (VI) absorber to the chassis and examine whether the resulting energy transfer mechanism is an effective way to reduce the peak value of the inertial force measured at the passenger compartment. The influence of the absorber parameters is first studied based on a practical impulsive force, and the optimal design of the absorber is then obtained. Next, an asymmetric clearance arrangement of the absorber is suggested to facilitate the mitigation. Finally, an impulsive acceleration excitation is applied to the system to examine the robustness and efficacy of the optimised absorber. Results of numerical simulations demonstrate that a properly designed VI absorber can significantly decrease the maximum inertial force at the passenger compartment, generated by external impulsive excitations.     

Development of a new sound metric for impact sound in a passenger car using the wavelet transform

Vehicles can experience impacts due to harsh road conditions. Contact with an uneven road surface causes vehicles to vibrate, which generates a loud impact sound. The attenuation of such noise is important because car passengers may complain about the impact noise. However, perfect removal of impact noise is not possible because most of it is caused by external conditions. More research is needed on the objective attributes of impact noise; however, the problem of impact noise is not a simple matter because impact noise is transient in nature and reaches a high level instantaneously. In this paper, a new objective attribute of impact noise is designed using the wavelet transform, which is appropriate for analyzing nonstationary signals, such as an impact signal. The usefulness of the new objective attribute, which is a sound metric, is examined by comparing the mean subjective ratings for real impact noise in passenger cars. The new sound metric has better correlation with the mean subjective rating than currently existing sound metrics.     

Measuring the impact of urban policies on transportation energy saving using a land use-transport model

Various projects all over the world are attempting to build smart cities in hopes of achieving energy-efficient and livable communities, but most of them are aiming to fulfill their goals technologically. However, the energy efficiency and livability of a city are affected by not only these technological factors but also urban structures that encompass residential areas, offices, transportation networks, and other facilities. Urban policies intervene in transportation and land-use conditions and thereby change how citizens consume energy and go about their daily lives as the actors in the urban system alter their behavior. This means that energy efficiency and quality of life share close ties. Assessments of urban policies thus need to consider the reactions of actors to the intervention.     

Model-based analysis of the mechanical subsystem of an air brake system

Most commercial vehicles such as buses and trucks use an air brake system, often equipped with an S-cam drum brake, to reduce their speed and/or to stop. With a drum brake system, the clearance between the brake shoe/pad and the brake drum may increase because of various reasons such as wearing of the brake shoe and/or brake drum and drum expansion caused by high heat generation during the braking process. Hence, to ensure proper functioning of the brake system, it is essential that the clearance between the brake shoe and the brake drum is monitored. In this paper, we present a mathematical model for the mechanical subsystem of the air brake system that can be used to monitor this clearance. This mathematical model correlates the push rod stroke transients and the brake chamber pressure transients. A kinematic analysis and a dynamic analysis of the mechanical subsystem of the air brake system were performed, and the results are corroborated with experimental data.     

Multivariate modeling of pedestrian fatality risk through on the spot accident investigation

Pedestrians are the most vulnerable users of public roads and represent one of the largest groups of road casualties; their death rate around the world due to vehicle-pedestrian collisions is high and tending to rise. In Spain, as in other countries of the European Union, steps have been taken to reduce the number and consequences of such accidents, with encouraging results in recent years. A key to countering this concern is the accident research activity that has obtained remarkable achievements in different fields, especially when multidisciplinary approaches are taken. This paper describes the development of a multivariate model that is able to detect the most influential parameters on the consequences of vehicle-pedestrian collision and to quantify their impact on pedestrian fatality risk. First, an accident database containing detailed information and parameters of vehicle-pedestrian collisions in Madrid has been developed. The accidents were investigated on the spot by INSIA accident investigation teams and analyzed using advanced reconstruction techniques. The model was then developed with two components: (1) a classification tree that characterizes and selects the explanatory variables, identifying their interactions, and (2) a binary logistic regression to quantify the influence of each variable and interaction resulting from the classification tree. The whole model represents an important tool for identifying, quantifying and predicting the potential impact of measures aimed at reducing injuries in vehicle-pedestrian collisions.     

Bumper optimum design using the dynamically equivalent beam under various impact conditions

Nowadays it is required for the bumper system to meet the various impact conditions simultaneously; barrier impact, IIHS (Insurance Institute for Highway Safety) bumper impact and pedestrian impact. Firstly, dynamically equivalent bumper beam models were developed for each impact condition and its accuracy was verified by nonlinear finite element analysis result. Dynamically equivalent pedestrian impact beam model was developed by using the equivalent forces of bumper beam and stiffeners. Pedestrian bending angle was obtained by using this equivalent pedestrian beam model. By combining these equivalent beam models, bumper optimum design program was developed. In this optimum design program, direct search method was used for the optimization algorithm. To verify the accuracy of this optimum design program, a nonlinear finite element result was used. By using this optimum design program, it can be secured the bumper impact performances in an early design stage and it will be also contributed to reduce the design time and test costs.     

Evaluating the effects of external factors on pedestrian violations at signalized intersections (a case study of Mashhad,Iran)

One of the most critical reasons for accidents involving pedestrians in signalized urban intersections is their violations regarding running red lights. Therefore, studying the essential factors in this issue is of interest to researchers. This research aims to evaluate the external factors affecting the pedestrians' violation, specifically, factors regarding the geometrical design and traffic situation. Cameras recorded the behavior of 1590 pedestrians in 10 crosswalks of 6 intersections in Mashhad. Afterward, the effect of 12 distinct variables for each pedestrian was assessed. To analyze the data, SPSS was used in combination with binary logistic regression. Out of the nine variables participated in the model, “traffic volume”, “the number of violators”, “length of the crosswalk”, “red light duration”, and “physical movement problems” affect the pedestrians' decision to comply with or violate a red light. The analysis shows that with an increasing number of vehicles, the probability of violation would reduce by 9.5%. Moreover, if the number of other violating pedestrians grows, the probability of violation would increase significantly. The increase of one unit in “length of the crosswalk”, would result in a violation reduction of 13.9%. Also, if the pedestrian suffers from physical disabilities, the probability of violation decreases by 78.6%. On the other hand, the growth of one unit in “red light duration” would increase the violations by pedestrians 2.2%.     

针对行人保护头部仿真分析中雨刮臂的接触设置研究

利用计算机进行有限元仿真分析,在汽车行人保护性能开发过程中有着广泛的应用。对于行人保护建模来说,风挡玻璃区域应按照实际情况对玻璃进行准确建模,然而对于风挡玻璃与雨刮器采用以往的接触设置,雨刮臂与玻璃产生穿透现象。因此为了解决穿透问题,准确模拟出其实际运动关系,对于雨刮臂与风挡玻璃之间的接触设置研究是非常有必要的。     

Effects of the bumper stiffness characteristics on the pedestrian head injuries and the lower extremities injuries;

The effect of bumper stiffness characteristics on the pedestrian head and lower extremity injuries was investigated by using a vehicle Finite Element (FE) analysis model of the National Highway Traffic Safety Administration (NHTSA) of the USA. Some bumper stiffness curves for 20, 40, and 60 km/h crash speeds were obtained by the FE method. The effects of bumper stiffnesses of 0~1.27 MN /m on pedestrian head and lower extremity injuries were conducted by using a multi-body simulation method. The results show that different bumper stiffnesses have almost no effect on the overall kinematic response of pedestrians, but have an extremity effect on the injuries for pedestrian head and lower limb, especially for lower limb injuries. The pedestrian's head maximum contact force is 4.28 kN and 4.26 kN respectively, and the pedestrian's lower leg maximum contact force is 3.94 kN and 9.36 kN respectively, at the stiffness of the bumper contact force-deformation curve corresponding to 20 km/h and 60 km/h. Therefore, the risk of pedestrian lower limb injury increases with the increase of bumper stiffness. © 2023 Authors. All rights reserved.     

某双曲拱桥承载能力评估方法探讨

我国目前存在着大量的双曲拱桥,由于建造年代久远及原设计荷载等级低等特点,近年来随着交通流量和交通荷载的迅猛发展,桥梁结构不堪重负,造成较严重损伤,结构存在较大的安全隐患。如何合理准确评价既有桥梁的承载能力,是充分发挥这些旧桥的作用,又保证结构安全的关键。基于对结构现有病害调查和成因分析,并结合无损检测和静载试验结果,根据结构实际受力状况和交通量建立计算分析模型,探讨既有桥梁承载能力的评估方法。     

某管道桥的检测与评定分析

某污水处理厂管道桥建于1976年,并于1985年进行了修复,管道桥主桥为150m跨径的悬索桥,跨越黄河河段.为全面了解该桥的工作状态、消除安全隐患、确保企业生产安全,对该桥进行使用状态下的检测鉴定与运营安全性评价,主要内容包括结构外观检查、无损检测、动力特性测试等,同时对结构进行有限元检算.检测和评定结果表明,该桥的技术状况等级为较好状态,但需对已发现病害及时进行维护和处理,防止病害进一步加深或扩大.     

空管运行效率评估指标体系研究

空管运行效率是衡量一个区域空管系统总体运行状态的综合指标,它受到很多与空管系统有关因素的影响。基于人机环系统工程理论,结合空管运行实际情况,充分分析空管运行效率的影响因素,建立空管运行效率评估的原则、标准和指标体系。     

A real-time impact detection and diagnosis system of catenary using measured strains by fibre Bragg grating sensors

This paper describes an impact detection system using strain signals based on fibre optic sensors(FBG) for the real-time monitoring of the catenary system. The proposed detection system consists of three subsystems: a measuring system, a data processing and analysis system, and a status display and data access system. Because the strain signals obey the normal distribution, to monitor the catenary system in real time, a novel method that combines mobile standard deviation with the mobile Pauta criterion is proposed to distinguish real impact from the strain signal background. The use of this adaptive judging method reduces the misjudgment rate of impacts and improves the impact recognition accuracy. These impacts can be identified by the data analysis system, which provides impact location and their causes using the features of the catenary system. This method can simplify the detection system compared with the traditional location method. An application to a commercial metro line system indicated that the impacts on the catenary system were main caused by overlaps, expansion joints or steady arms, and were verified by correspondence with the floor plan of the catenary and manual inspection results. These results verified the reliability and effectiveness of the proposed impact detection system.