Browse Topic: Underride guards
A Rear Underrun Protection Device (RUPD) is a safety feature installed on the rear end of chassis of trailers, designed to prevent smaller vehicles from sliding underneath the rear of the trailer in the event of a collision. Therefore, it plays a critical role in reducing the risk of serious injuries or fatalities. The RUPD standard is updated aiming to improve the strength and resistance of these devices, therefore improving the road safety. This paper shares the author’s experience with the latest standards and regulations for Rear Underrun Protection Devices (RUPD), with a focus on the use of Advanced High Strength Steel (AHSS). It provides a general overview of RUPD standard requirements and suggests several AHSS steel tube sizes suitable for the main longitudinal member, serving as a starting point for design. Key design parameters and potential failure points in RUPD structures are discussed, along with possible solutions. Finite Element Modeling (FEM) is commonly used in the design phase to assess structural performance before physical testing. Given the high costs of prototyping, FEM accuracy is crucial. The paper highlights common sources of inaccuracy—mainly related to modeling techniques—and suggests ways to improve reliability.
Impacts between passenger vehicles and heavy vehicles are uniquely severe due to the aggressivity of the heavy vehicles; this is a function of the difference in their geometry and mass. Side crashes with heavy vehicles are a particularly severe crash type due to the mismatch in bumper/structure height that often results in underride and extensive intrusion of the passenger compartment. Underride occurs when a portion of one vehicle, usually the smaller vehicle, moves under another, rendering many of the passenger vehicle safety systems ineffective. Heavy vehicles in the US, including single-unit trucks, truck tractors, semi-trailers, and full trailers, are currently not required to have side underride protection devices. The NTSB, among other groups, has recommended that side underride performance standards be developed and that heavy vehicles be equipped with side underride protection systems that meet those standards. The work presented used virtual testing to evaluate the relative performance of example side underride devices compared with a baseline. We also evaluate the effects of different test conditions on underride guard performance. Crash test results were utilized for calibration purposes. A tractor-trailer, with and without side impact underride protection, was impacted by a passenger car and SUV under a range of impact conditions. Passenger vehicle intrusion metrics were calculated to provide an indication of relative risk for each impact condition. The results can support the development of side underride protection recommended practices.
Occupant dynamics during passenger vehicle underride has not been extensively evaluated. The present study examined the occupant data from IIHS rear underride crash tests. A total of 35 crash tests were evaluated. The tests were classified as full-width (n = 9), 50% overlap (n = 11), and 30% overlap (n = 15). A 2010 Chevrolet Malibu impacted the rear underride guard of a stationary trailer at 35 mph. Several occupant kinematics and dynamics data including head accelerations, head injury criteria, neck shear and axial forces, neck moments, neck indices, chest acceleration, chest displacement, chest viscous criterion, sternum deflection rate, and left/right femur forces/impulses, knee displacements, tibia axial forces, upper/lower tibia moments, upper/lower tibia indices, and foot accelerations were measured. The vehicle accelerations, delta-Vs, and occupant compartment intrusions were also evaluated. The results indicated that the head and neck injury parameters were positively correlated with driver A-pillar rearward intrusion. The 30% overlap crashes showed significantly higher intrusion and head and neck injury values than the 50% and full-width crashes. No strong relationship between head and neck injury parameters and vehicle delta-V or peak acceleration was observed. None of the chest injury criteria exceeded the chest IARV tolerances in the crash tests examined. No relationship between chest injury parameters and vehicle delta-V, acceleration or driver A-pillar rearward intrusion was observed. No strong relationship was observed between left/right leg injury parameters and vehicle delta-V, acceleration or driver A-pillar intrusion. Only for two crash tests, the “left upper tibia A-P moment”, “left upper tibia resultant moment” and “left upper tibia index” exceeded the IARV tolerances. This study suggested that in underride crashes there is a higher chance of head/neck injuries than other body regions. Also, in addition to delta-V, other parameters such as percent overlap and occupant compartment intrusion should be taken into consideration when analyzing the biomechanics of underride.
Rear underrun protection device is crucial for rear impact and rear under-running of the passenger vehicles to the heavy duty trucks. Rear underrun protection device design should obey the safety regulative rules and successfully pass several test conditions. The objective and scope of this paper is the constrained optimization of the design of a rear underrun protection device (RUPD) beam of heavy duty trucks for impact loading using correlated CAE and test methodologies. In order to minimize the design iteration phase of the heavy duty truck RUPD, an effective, real-life testing correlated, finite element model have been constructed via RADIOSS software. Later on, Pareto Optimization has been applied to the finite element model, by constructing designed experiments. The best solution has been selected in terms of cost, manufacturing and performance. Finally, real-life verification testing has been applied for the correlation of the optimum solution.
This work describes the design and testing of side underride protection devices (SUPD) for tractor-trailers and straight trucks. Its goal is to reduce the incompatibility between small passenger cars and these large vehicles during side collisions. The purpose of these crash attenuating guards is to minimize occupant injury and passenger compartment intrusion. The methods presented utilize a regulation previously created and published for testing the effectiveness of these devices based on the principles of a force application device already implemented in the Canadian rear underride guard regulation. Topology and multi-objective optimization design processes are outlined using a proposed design road map to create the most feasible SUPD. The test vehicle in question is a 2010 Toyota Yaris which represents the 1100C class of vehicle from the Manual for Assessing Safety Hardware (MASH). Since the tractor-trailers and straight trucks utilize different structural components, separate concepts must be generated to accommodate each individual application. The LS-DYNA software package is employed for the creation of the devices, the simulations and the optimization. The guards are tested and their performance is evaluated in order to examine their benefits during collisions.
The heavy commercial vehicles are equipped with under-run protection devices (UPD) to enhance safety of occupants in small vehicles in the event of under-run. These UPD are popularly classified as RUPD (rear under-run protection devices), SUPD (side under-run protection devices), FUPD (front under-run protection devices). These devices primarily work to improve safety of smaller vehicles by changing its interaction with heavy vehicles thereby resulting in change in small vehicle structural engagement for energy absorption. Without UPD, smaller vehicle passenger compartment is likely to interact with stiff commercial vehicle chassis frame structures. However with UPD, the smaller vehicle front-end structure gets involved in the crash which helps in controlled energy absorption and safe-guards the passenger compartment. At present, regulatory criteria have been defined for the minimum static strength, stiffness requirements at component level for these UPD besides dimensional requirements for their installations on the commercial vehicles. However, it was of interest to study the effectiveness of these devices for enhanced occupant safety in real-world accidents and significance of the regulatory structural requirements. The paper describes the assessments of dynamic crash tests of a passenger car and a stationary heavy truck fitted with and without RUPD. The assessment includes structural interactions and interactive forces between them.
This SAE Recommended Practice is intended to provide a uniform basis for evaluating the effectiveness of rear underride devices employed to reduce the likelihood of penetration of the passenger compartment of an impacting vehicle. The procedures described in this report provide means for determining the characteristics of a rear underride guard, taking into consideration the nature and direction of forces involved.
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