Simulation Analysis On The Rollover Risk State Of Hazmat-transport Tractor-semitrailer

In recent years, with sustained and rapid development of the national economy, the community's demand for various categories of hazmat(hazardous material) has expanded each year. Meanwhile, the number of hazmat traffic accidents, including rollover, collision, leakage and explosion, are also clearly show an upward trend. Taking 2006 for example, allover the country, there are totally 533 road accidents involved in hazmat, resulting in 264 deaths, 627 people injured and directly property loss of more than 1627 yuan. The average annual growth rate of hazmat transportation accidents is more than 30%, which is the fastest growing rate among the traffic accidents. The large and extra large accidents are shocking.Hazmat transportation safety has become a road safety problem in urgent need of solution. Confronting the increasingly serious security situation in road transport, at home and abroad, the government unveils a number of laws and regulations to make hazmat transport included in the rule of law and establishes a long-term management mechanism. In the vehicle supervision and early warning technology field, western developed countries have a large number of studies, which mainly focuses on developing on-vehicle safety devices, and establishing emergency rescue system and information collection and distribution systems based on ITS, and has entered a practical stage of research after years of hard work. Domestic research in this area started late, until the 90's, with the rapid development of the technology of GPS positioning and GIS, the domestic research has began in the micro-technology side.Researching on identifying risk state of the vehicle and on- vehicle early warning technology is the research focus at present abroad, but also is an essential requirement for upgrading the vehicles of transporting hazmat. This paper combined the need of the research on vehicles in-transit risk status identification and supported by The Jilin Province Science and Technology Developing Project of《Research on The Comprehensive Supervision & Early Warn Technology for Road Transporting Hazmat》(Contract Number: 20065007), mainly research the rollover risk state threshold of a transporting hazmat tank tractor-semitrailer.When a tank tractor-semitrailer is in the non-loaded state, moving into the turn or high-speed changing lane, the liquid cargo in the role of gravity and centrifugal force will tend to one side. Due to the location of the liquid center of mass changes, vehicle center of mass transfers, which affects the rollover characteristics of vehicle, reduces the rollover threshold and the roll stability in driving process. In addition, tractor-semitrailer has special natures such as big quality, big size, high center of gravity position, narrow wheelbase and so on. So all above mentioned makes rollover accidents easily happen. According to the data from the Highway Traffic Safety Administration in the U.S.A,during the course of transporting liquid hazmat, the 95% of the tank tractor-semitrailer accident is due to the rollover and the rollover accident accounts for 40% of tank tractor-semitrailer accidents. The crew mortality rate in rollover accidents take up 33 % of traffic accidents.This paper introduced the research status about the tractor-semitrailer dynamics modeling and roll theory at home and abroad; basing on a lot of reading on the roll stability of the tractor-semitrailer research, outlined an overview on the basic concept of tractor-semitrailer roll, rollover; analyzed the factors impacting the roll stability of a tractor-semitrailer and the affection that maneuverability of a tractor-semitrailer operated on the roll stability; through the mathematical derivation, established a dynamical equation for the ADAMS dynamics simulation to simulate the affection operated on the performance of the running vehicle by sloshing of liquid cargo in the tank, which joined the moving characteristics of liquid cargo in tank to the research on the roll stability of tractor-semitrailers.According to the real parameters of the hazmat-transport tractor-semitrailer, applicated ADAMS, basing on some assumptions, this paper established a liquid tank hazmat-transport tractor-semitrailer multi-body dynamics simulation model with 351 degrees of freedom including front suspension model, steering system model, rear suspension model, vehicle body frame model and tire-road model; illustrated methods and processes of modeling in details; did a steering characteristic test, and the test result showed that the the model had characteristic of lack steering; made a useful exploration on building the dynamics model of the tractor-semitrailerUsing the vehicle model, basing on considering the sloshing impact in tank, did a large number of open-loop simulation tests under steering and high-speed changing lane conditions to research the rollover risk state of tractor-semitrailer; outputed the roll response curve of each parameters, and made a deep study on internal relations among the speed, load and steering wheel angle, when the rollover risk state occurred, made sure the risk state threshold of the tank tractor-semitrailer rollover under steering and high-speed changing lane conditions. Comparing the different performance of tractor-semitrailer between carring the solid cargo and liquid cargo, which showed the sloshing of the liquid cargo in the tank reduced rollover stability of vehicle in the driving process, and made rollover accidents easier to happen.The multi-body dynamic model of the tank tractor-semitrailer, experimental research methods, ideas and conclusions laid the foundation for follow-up research work, and provided a reference for identifying the risk state of the running hazmat-transport tank tractor-semitrailer.