农林车辆安全驾驶室碰撞的数值模拟

农林用车辆安全驾驶室碰撞系统具有几何非线性和材料非线性等多重非线性特点,应用大变形弹塑性理论,建立驾驶安全系统数学模型,对安全驾驶室强度特性进行分析,预估车辆翻车时驾驶室结构件的力—变形,预测变形侵入驾驶员容身空间的安全性,并进行变形的屈服评判,实现车辆安全驾驶室结构碰撞的数值模拟。文中以某农林车辆安全驾驶室碰撞的数值模拟为例,理论计算和试验结果吻合,方法切实可行,为车辆驾驶室安全设计提供依据。     

大功率带式运输机软起动装置试验台的研究

研究了液压恒压网络二次调节系统在大功率软起动装置试验台中的应用,建立了控制规律的数学模型,按照控制规律,调节二次元件的排量,实现驱动单元扭矩及转速的调节;加载单元,不仅能实现功率回收,还可通过预建压的方法,实现理想的恒扭矩加载。试验台可完全模拟真实的工况试验     

大功率带式运输机软超支装置试验台的研究

研究了液压恒压网络二次调节系统在大功率软起动装置试验台中的应用,建立了控制规律的数学模型,按照控制规律,调节二次元件的排量,实现驱动单元扭矩及转速的调节;加载单元,不仅能实现功率回收,还可通过预建压的方法,实现理想的恒扭矩加载。试验台可完全模拟真实的工况试验。     

装配式地下粮仓钢板-混凝土组合仓壁轴压受力性能分析

为了研究装配式地下粮仓钢板-混凝土组合仓壁的轴压力学性能,该研究在仓壁试件轴压试验的基础上,对仓壁试件进行非线性有限元分析,模拟试件加载的全过程,进一步分析试件及其组件在加载过程中的受力性能及工作机理,并对钢板强度、混凝土强度、距厚比等不同的参数影响规律进行了分析。结果表明:有限元模拟结果与试验结果吻合较好,在最大试验载荷5 000 kN时模拟轴向压缩总变形与试验平均轴向压缩总变形相对差值为4.2%,建立的有限元模型适用;在弹性阶段仓壁预制块部位混凝土和接头部位止水钢板分别承担了79.7%和50.9%的荷载,峰值荷载主要由混凝土和传力钢板决定,达到峰值荷载后接头部位止水钢板承担更大的荷载,增强止水钢板可以改善试件的延性;相较钢板强度、距厚比和止水钢板厚度,混凝土强度对仓壁试件的初始刚度和峰值荷载影响最大,混凝土强度、钢板强度、距厚比和止水钢板厚度对峰值荷载回归得到的回归系数值分别为0.910、0.154、-0.005和0.301;止水钢板的强度和厚度较小时,试件易发生脆性破坏;结合设计参数分析中得到的荷载-变形曲线,提出2种荷载-变形模型曲线,进一步提出装配式钢板-混凝土组合仓壁轴压峰值荷载简化计算式,得到的计算峰值荷载与有限元峰值荷载相对差值均不超过9%,计算结果具有较高的精度。研究结果可为装配式地下粮仓仓壁的工程设计提供指导和参考。     

驾驶室结构安全强度分析

根据GB7121—86的驾驶室安全强度验收标准,用弹塑性理论和非线性有限元方法,建立了驾驶室的数学力学模型,并进行了模拟计算,据此,可以实现对轮式拖拉机驾驶室的安全强度预估。     

基于Pro/E Manikin的拖拉机驾驶室人机工程评价方法

人机工程学设计是拖拉机驾驶室设计中非常重要的部分.该文以确定的H点为参考,运用人机工程学设计原则,对拖拉机驾驶室的驾驶员座椅和各操纵装置进行了布局和设计,并建立了驾驶室的 Pro/E 三维模型,运用Pro/E Manikin模块对驾驶员的坐姿舒适性、驾驶员视野性能、驾驶员的操作空间3个方面进行仿真和评价.结果表明,原设计方案中无法同时满足对各操纵装置的舒适性.对驾驶室优化布局和设计,首先,H点位置在X方向的坐标位置为550和581 mm时,分别调用第5百分位和第95百分位的中国男性人体模型进行分析,各操纵装置在操纵舒适性的RULA分析分数为1时,方向盘、变速杆、侧控台和前控台距踵点水平距离范围分别为290~352、366~437、375~420和128~213 mm.其次,通过Pro/E Manikin中到达包络的阴影区域检查操作空间是否符合要求.最后,在进行驾驶室设计过程中,将消音器和空气滤清器的位置设计在前立柱对驾驶员形成的盲区范围内,将水平面前方2个不可避免的盲区(12.81°和14.36°)叠加,最大程度的减小了驾驶员的盲区.优化设计后的驾驶舒适性、视野性能及易操作性在一定程度上都得到了改善.该方法为拖拉机驾驶室人机工程学设计提供了一定的参考.     

隔振器在拖拉机驾驶室降噪中的应用

在对拖拉机驾驶室振动、噪声及对穿联结式隔振装置的性能进行试验分析的基础上,对原拖拉机驾驶室隔振装置进行了改进设计,取得驾驶室内耳旁噪声下降12dB(L)和3.3dB(A)的良好效果。     

农业装备驾驶室虚拟人机工程学设计与评价

以拖拉机和联合收割机等典型农业装备驾驶室为研究对象,建立了基于元件类型、元件、元件特征参数的“顶层、中间层、底层”三层驾驶室人机界面评价指标体系;利用OpenGL参数化模型设计方法和虚拟现实交互技术,研究了驾驶室分层次模糊综合评判的客观评价方法与基于虚拟漫游交互的主观评价方法;基于VS.NET 开发系统和Multigen Vega Prime仿真平台,开发了农业装备驾驶室虚拟人机工程学设计与评价系统。对某国产拖拉机的应用结果表明,基于所开发系统的客观评价和虚拟试验评价结果基本一致,可作为一种设计和评价农业装备驾驶室的重要手段。     

2F-6-BP1型变量配肥施肥机的研制与试验

针对国内与大马力拖拉机配套应用施肥机型缺乏的问题,该文应用变量配肥施肥技术,设计了2F-6-BP1型变量配肥施肥机。施肥机通过GPS系统获取车辆在田间的位置信息,通过预先加载的施肥处方图,获取当前位置的目标施肥量,采用称重法反馈肥料流量信息,并按照当前车辆行进速度,实时调整施肥量,进行变量配肥施肥作业,达到精准施肥目的。对2F-6-BP1型变量施肥机系统设计、工作原理及试验情况进行了介绍。室内外试验结果表明,该变量配肥施肥机称重系统的最大称量误差为0.65%,施肥精度可达到95%以上,可实现精准施肥作业,具有良好的经济性和实用性。     

沿前刺孔行驶的水田叶轮动力学的试验研究

四轮驱动拖拉机的驱动轮沿前轮辙行驶,在旱地、水田获得良好的牵引性能,因而得列广泛应用,有取代履带拖拉机的趋势。在水田,四轮驱动船式拖拉帆具有优良的越野、牵引性能,其后驱动叶轮除滑前驱动轮轮辙行驶外,还要求后驱动轮轮时沿前驱动轮刺孔行驶,这是更进一步的要求。该文是对沿前刺孔行驶的四轮驱动船式拖拉机动力学的专项试验研究,设计了三轮叶模拟试验装置,对前后轮叶刺孔的最佳偏移距或偏移率、前岳驱动叶轮轮叶的推力、承力和效率,以及影响效率的因素如滑转率、倾角、陷深、轮叶数等进行了深入的试验和探讨。     

Finite element modeling of ROPS in static testing and rear overturns

Even with the technological advances of the last several decades, agricultural production remains one of the most hazardous occupations in the United States. Death due to tractor rollover is a prime contributor to this hazard. Standards for rollover protective structures (ROPS) performance and certification have been developed by groups such as the Society of Automotive Engineers (SAE) and the American Society of Agricultural Engineers (ASAE) to combat these problems. The current ROPS certification standard, SAE J2194, requires either a dynamic or static testing sequence or both. Although some ROPS manufacturers perform both the dynamic and static phases of SAE J2194 testing, it is possible for a ROPS to be certified for field operation using static testing alone. This research compared ROPS deformation response from a simulated SAE J2194 static loading sequence to ROPS deformation response as a result of a simulated rearward tractor rollover. Finite element analysis techniques for plastic deformation were used to simulate both the static and dynamic rear rollover scenarios. Stress results from the rear rollover model were compared to results from simulated static testing per SAE J2194. Maximum stress values from simulated rear rollovers exceeded maximum stress values recorded during simulated static testing for half of the elements comprising the uprights. In the worst case, the static model underpredicts dynamic model results by approximately 7%. In the best case, the static model overpredicts dynamic model results by approximately 32%. These results suggest the need for additional experimental work to characterize ROPS stress levels during staged overturns and during testing according to the SAE standard.     

Development and validation of a computer program to design and calculate ROPS

In Spain, there are more than 250,000 tractors built before 1980, when it became mandatory for all new tractors to be equipped with a rollover protective structure (ROPS). A similar situation is found in the European Union, but the situation is worse in the U.S. and in developing countries. Directive 2003/37/EEC establishes that tractors over 800 kg weight can be homologated by using the OECD standard code for the official testing of protective structures on agricultural and forestry tractors (static test), called Code 4. A ROPS attachable to the rear axle of different tractor models has been designed, and a computer program for the calculation of the ROPS design has been developed. The program, named ESTREMA, is available at: www.cfnavarra.es/insl. Using this program, it has been possible to design a ROPS for the Massey Ferguson model 178 tractor, one of the most common tractor models without a ROPS in Spain. After the tractor was equipped with the designed ROPS, it was tested at the Spanish Authorized Station for testing ROPS and passed the homologation test (OECD Code 4), the main results being a maximum distortion of 21.3 cm when the absorbed energy was 5437 N and the maximum force applied was 34 kN during loading from the side. The ROPS was improved, redesigned, and remounted on the tractor, the tractor was tested in a real overturn, and no part of the structure intruded on the driver's clearance zone during the test. In conclusion, the ESTREMA program worked correctly, and the designed ROPS was able to pass the authorized test and provide adequate protection to the operator during a real overturn.     

Initial rollover effectiveness evaluation of an alternative seat belt design for agricultural tractors

A test program was conducted to determine the effectiveness of a seat belt restraint in preventing occupant movement in a rollover accident. A baseline type-2 seat belt (pelvic and torso restraint), and an improved type-2 seat belt restraint, both designed to restrict occupant motion in a rollover accident, were tested in a rollover restraints tester (RRT). Each seat belt was placed on a H-III 50th percentile male dummy and testing conducted at a single roll rate and two D-ring adjustment positions. Each test simulated what was approximately a 260 degrees per second rollover parallel to the longitudinal axis of the tractor with the top of the ROPS impacting the ground after 180 degrees of roll. Forces on the dummy's head and neck were measured, and video was taken to measure the head motion in the x-, y-, and z-axis of the dummy. The average vertical, forward, and lateral head movement in the baseline seat belt was 144, 222, and 184 mm, respectively, when the adjustable D-ring anchorage supporting the shoulder belt was in its lowest position. At the lowest D-ring height, the shoulder belt became ineffective and the seat belt performance became similar to a type-1 restraint (required for tractors with ROPS) resulting in increased vertical, forward, and lateral movement. The improved restraint reduced vertical head movement by as much as 75% without increasing head and neck loads above established injury criteria. Testing seat belts for rollover effectiveness will become increasingly important as seat belt usage on tractors with ROPS increases.     

割草机连续翻滚中翻滚保护装置的有限元分析

针对割草机在斜坡上工作时引起的连续翻滚工况,利用有限元非线性分析法建立了ROPS 有限元模型, 对ROPS进行强度分析,预测了车辆连续翻滚时ROPS构件的应力、变形及吸能,并预测了变形后的ROPS是否侵入驾驶员容身空间（Clearance Zone）。最后进行了翻滚试验验证有限元模型的准确性,结果表明：ROPS的有限元分析与试验结果吻合,翻滚过程中,ROPS 未进入驾驶员容身空间,有限元分析为车辆ROPS安全设计提供了可靠依据。     

Operator assessment of tractor roll angle with and without a tractor stability visual feedback device

According to a 2004 National Institute for Occupational Safety and Health (NIOSH) report, approximately 250 to 350 fatalities occur each year due to incidents involving production agriculture workers and tractors. Tractor overturns account for about 150 to 200 of these deaths. The goals of this project were to study operators' understanding of tractor roll angles and test a device to effectively deliver stability information to the tractor operator. This project required the design and construction of a full-scale tractor cab roll simulator that was used to identify lateral roll angles at which volunteer participants felt uncomfortable, as well as lateral roll angles at which they would no longer operate a tractor. In addition, the participants performed a series of tasks to test the functionality of a visual slope indicator that was designed to help them estimate slope angles. The project tested 231 tractor operators' perceptions of safe operation on side slopes and 128 participants' interactions with the visual slope indicator. Testing showed that the visual slope indicator was able to influence the angle estimations of the novice tractor operator population and helped the entire population of participants more accurately rank the simulator scenarios.     

Performance of an automatically deployable ROPS on ASAE tests

In the U.S., approximately 132 agricultural tractor overturn fatalities occur per year. The use of rollover protective structures (ROPS), along with seat belts, is the best-known method for preventing these fatalities. However, one impediment to ROPS use is low-clearance situations, such as orchards and animal confinement buildings. To address the need for ROPS that are easily adapted to low-clearance situations, the Division of Safety Research, National Institute for Occupational Safety and Health, developed a prototype automatically deploying, telescoping ROPS (AutoROPS). The NIOSH AutoROPS consists of two subsystems. The first is a retractable ROPS that is normally latched in its lowered position for day-to-day use. The second subsystem is a sensor that monitors the operating angle of the tractor. If an overturn condition is detected by the sensor, the retracted ROPS will deploy and lock in the full upright position before ground contact. Static load testing and field upset tests of the NIOSH AutoROPS have been conducted in accordance with SAE standard J2194. Additionally, timed trials of the AutoROPS deployment mechanism were completed. The results of these tests show that the NIOSH AutoROPS has significant potential to overcome the limitations of current ROPS designs for use in low clearance as well as unrestricted clearance operations.     

Stories or statistics? Farmers' attitudes toward messages in an agricultural safety campaign

Farming is the second most hazardous occupation in the U.S. The high mortality rate is due in large part to farm equipment hazards, particularly tractor overturns. Injuries and deaths associated with tractor overturns could be prevented with the use of a rollover protective structure (ROPS). In spite of the known dangers associated with overturn incidents, farmers are reluctant to retrofit ROPS on older tractors. Few agricultural safety campaigns target the issue of ROPS retrofits, and none have been evaluated systematically. This article reports a study that examines a set of messages that were central to the Community Partners for Healthy Farming project. This study indicates that narrative-based messages and messages incorporating fear appeals are more favorably evaluated by farmers than messages that simply inform farmers or messages that rely on statistics.     

Evaluating the protective capacity of two-post ROPS for a seat-belted occupant during a farm tractor overturn

This study evaluated the effectiveness of a commercial rollover protective structure (ROPS) and size-extended ROPS in protecting a 95th percentile male operator during tractor overturns. Six rear upset tests (commercial ROPS) and ten side upset tests (commercial and size-extended ROPS) were conducted. A 95th percentile instrumented male manikin was used in all tests. Head injury criterion (HIC15), 80 g limit on resultant head acceleration, neck injury criterion (Nij), and peak axial force (extension-compression) were employed to evaluate injury potential. In all rear tests, the manikin's head impact with the ground was within the tolerance limits for head/neck injuries. Based on limited trials in the side tests, the study observed a small to moderate chance of neck injuries under the commercial and size-extended ROPS conditions; the injury risk was not statistically significant between these two test conditions. This study identified a risk of non-fatal injuries for large-size operators in side overturns, although the prevention effectiveness of commercial versus size-extended ROPS cannot be determined without further testing. These findings may have implications for future ROPS designs.