【作者】 司俊德；

【导师】 王国强；

【作者基本信息】 吉林大学 ， 机械设计及理论， 2011， 博士

【摘要】 工程车辆指应用于矿山、建筑、水利和筑路等领域的非公路行走机械,包括工业拖拉机、装载机、挖掘机、压路机、推土机、平地机、挖掘装载机和自卸汽车等。工程车辆由于行驶地面复杂、工作环境恶劣,翻车事故难以避免。工程车辆的翻车事故一旦发生,将会对司机造成致命伤害。为了保障司机的生命安全,目前国际通用的方法是在工程车辆上安装翻车保护结构。国际标准对翻车保护结构的性能提出了静态实验室试验要求。然而实践证明,满足国际标准要求的翻车保护结构并不能保证翻车时司机的生命安全。工程车辆翻车是一个动态冲击过程,在这个过程中,造成司机伤亡的原因主要有以下几点：1)保护结构和地面撞击太大,导致加速度过大,人体伤害指数超过人体耐冲击域值；2)碰撞中回弹剧烈,导致人与车内物体反复碰撞,恶化司机伤害程度；3)司机室变形太大,司机被挤压,难以施救,使司机重伤死亡。司机的损伤程度取决于和地面接触碰撞系统的柔度、司机和车体间的约束以及保护结构的强度和刚度。符合国际标准要求的翻车保护结构仅能够避免第3种情况。此外,满足标准要求的翻车保护结构不能给司机提供足够的缓冲。本文结合国家自然科学基金项目：“非公路车辆翻车安全技术研究”(No.50775095)和国家"863"项目：“工程车辆安全性数字化试验平台”(No.2007AA04Z126),采用可视化计算机模拟和物理样机试验方法,对翻车后人体的损伤程度进行预测和评估,对新型缓冲吸能翻车保护结构进行了数值模拟和试验研究。在国内外工程车辆翻车保护结构设计、汽车碰撞安全、机车碰撞安全研究成果基础上,综合运用多体系统动力学、大变形非线性有限单元法、碰撞生物力学、测试及传感技术及材料学等多学科知识,以司机—车辆—地面环境构成的系统为研究对象,以人体损伤程度为评价指标,建立了工程车辆翻车事故模拟的虚拟样机。进行了典型工程车辆在规定坡道和地面条件下倾翻过程的数值模拟,对人体响应、结构吸能、结构强度刚度以及缓冲时间等进行全面仿真,提取人体响应及车体各部分受力和动态响应,得到车体参数、座椅参数、安全带约束形式、地面参数以及翻车保护装置吸能和支撑方式对人体损伤的影响,对人体损伤情况进行评价。在工程车辆翻车过程动态仿真和试验的基础上,结合翻车保护结构国际标准规定的实验室试验性能要求,提出一种基于人体损伤的翻车保护结构设计方法。该设计方法从司机保护的角度出发,以事故再现的方式来分析车辆翻车事故中,司机与车辆的运动状态和损伤状况,并以此为依据进行翻车保护系统安全性设计。提出了由缓冲吸能元件和金属框架结构组成的新型保护结构概念。在传统框架式翻车保护结构上安装缓冲吸能元件既能够吸收大量滚翻产生的动能,又能够减少翻车保护结构自身的变形量,从而解决了刚度要求和吸能要求的矛盾,并且缓冲吸能元件可以大幅削弱保护结构与地面第一次碰撞造成加速度峰值。从能量吸收、最大碰撞载荷和结构轻量设计的角度出发,将孔缺陷引导变形的薄壁直方管引入翻车保护结构设计。依据优化理论和代理模型,将有限元分析,试验设计、响应面法以及遗传算法多种手段相结合,对孔缺陷引导变形的薄壁直方管进行多目标抗撞性优化分析,得到翻车保护结构的最优的设计参数。本文研究成果将目前国际标准对翻车保护结构的性能要求由静态实验室试验提高到动态翻车人体损伤要求,将目前国际标准对保护结构、安全带等单独考核试验提高到将人-机-环境一体化试验,发展了工程车辆安全设计方法,对于保障工程车辆司机生命安全、提高我国在工程车辆市场竞争能力均有重要意义。更多还原

【Abstract】 Engineering vehicles refer to off-highway mobile machinery applied in mines, architecture, water conservancy, road construction and other fields, including industrial tractors, loaders, excavators, rollers, bulldozers and dump trucks, etc.. Since the road surfaces are complex and the working environment is harsh, engineering vehicles are susceptible to rollover accidents, and once rollover happens, the engineering vehicle will inflict fatal damage to the operator.To protect the life safety of the operator, the current international method is to install a rollover protection structure (ROPS) on engineering vehicles, and the international standards have stipulated static lab test requirements in view of ROPS performance. However, facts have shown that the ROPS that meet the requirements of international standards cannot protect the operator’s life safety upon rollover. The rollover of engineering vehicles is a dynamic impact process, during which the operator gets hurt due to the following reasons:1) Severe collision between the ROPS and the ground leads to high acceleration and a human body injury index beyond the threshold value of human body impact resistance; 2) Violent rebound in the collision results in repeated clashes between the operator and objects inside the vehicle, and aggravates the operator’s injury; 3) Dramatic deformation of the operator’s cab squeezes the operator and makes it hard for rescue, and thus causes severe injury or even death. The severity of the operator’s injury depends on the flexibility of the system contacting and colliding the ground, the restraint between the operator and the vehicle body as well as the strength and stiffness of ROPS. The ROPS satisfying the requirements of international standards can only avoid the third case and are unable to provide sufficient buffering for the operator.In this paper, visual computer simulation and physical prototype test method have been adopted in combination with the project of National Natural Science Foundation program "Roll-over safety technology for off-road vehicle" (No.50775095) and the national "863" program "Digital design platform of safety for Roll-over and Falling-object of off-road vehicles (No.2007AA04Z126) to predict and evaluate the operator’s injury after rollover, and to carry out numerical simulation and experimental study on a new type of buffer energy-absorption ROPS. Based on the findings of domestic and foreign researches on ROPS designs for engineering vehicles, car crash safety, motorcycle crash safety, a virtual prototype with the system of operator-vehicle-ground environment as the research object, body injure degree as evaluation index has been established to simulate rollover accidents of engineering vehicles by using multi-disciplinary knowledge including multi-body system dynamics, large deformation nonlinear finite element method, impact injury biomechanics, testing and sensor echnology and material science.Numerical simulation of the rollover process in the given (?)amps and ground conditions for typical engineering vehicle has been conducted; comprehensive simulation has been performed on human body response, energy absorption of the structure, strength and stiffness of the structure, buffer time and so on. Thus human body response, force exerted on various parts of the vehicle body and dynamic response have been extracted, and such parameters as parameters of vehicle body and seat, restraint form of seat belt, ground parameters, the influence of energy absorption and support mode ROPS on human body injury to evaluate human body injury have also been obtained.Based on the dynamic simulations and experiments of the rollover process of engineering vehicles and in combination with the lab test performance requirements in international standards for ROPS, the author has put forward a ROPS design method with the focus on human body injury. This design method starts from the perspective of protecting the operator and analyzes the movement of the operator and vehicle and their injury and damage in the way of accident reconstruction, on the basis of which safety design of rollover protection system has been conducted.In this paper, a new concept of protection structure has been proposed, which consists of buffer energy-absorption device and metal frame structure. The installation of buffer energy-absorption device on the traditional frame-type ROPS can not only absorb the kinetic energy generated by many rollovers, but also reduce deformation of ROPS itself, and thus solves the contradiction between the stiffness requirement and energy absorption requirement; besides, the buffer energy-absorption device can significantly weaken the peak value of acceleration due to the first collision between the protection structure and the ground. From the perspective of energy absorption, maximum collision load and structure light-weight design, thin-wall straight square pipes with hole-defect induced deformation are introduced into the ROPS design. According to the optimization theory and surrogate model, multi-objective anti-collision optimization analysis has been carried out on the thin-wall straight square pipe with hole-defect induced deformation by combining several means, namely, finite element analysis, experiment design, response surface method, genetic algorithm, and the optimal design parameters of ROPS have been obtained.The research findings of this dissertation improve the performance requirements for ROPS in current international standards from static lab tests to human body injury in dynamic rollover, and improve the individual assessment test on protection structures and seat belts, etc. stipulated by current international standards to the integrated test of human-vehicle-environment, which develops the safety design method for engineering vehicles and is of great importance to guaranteeing the operators’ life safety of engineering vehicles and improving the competitiveness of China in engineering vehicle market.更多还原