Compatibility of Passenger Vehicles and Cable Median Barrier Systems

Cross-median crashes are one of the most severe type of highway crashes. Many state Departments of Transportation (DOTs) install median barriers, such as cable median barriers (CMBs), to reduce the rate of cross-median crashes. Nonetheless, these barriers are not always successful. Approximately 20,000 cable barrier crashes throughout the United States spanning between 1999 and 2010 were examined, and detailed data was sufficient to determine the prevailing causes of 182 penetration crashes (i.e., barrier was breached). Penetration crashes involving CMBs were affected by: (1) impact conditions; (2) barrier placement and design; and (3) vehicle factors, including geometry and inertial properties. In general, CMB crashes occur at higher CG trajectory angles than with other roadside features. The 85th percentile CG trajectory angle for cable barriers was 39 degrees, compared to 25 degrees when all roadside features are considered. Approximately 2.2% of all CMB crashes were severe, although penetrations were between two and thirteen times more likely to be severe than non-penetration crashes. Vehicle factors such as weight and geometrical profile affected the likelihood of CMB penetrations. Headlights or taillights fractured or were damaged in approximately 80% of non-penetration crashes, but were damaged or fractured in less than 60% of penetration crashes, often by additional unrelated impacts. Lastly, heavier vehicles with more kinetic energy were more likely than similar, lighter vehicles to penetrate CMBs. Through better understanding of all of the complicating factors affecting CMB performance, better designs and guidelines can be prepared to maximize CMB effectiveness.

ADI-CRSTS: A New Method for the Moving Heat Sources — Application to a Train Pantograph Strip

The pantograph strip interface involves many physical phenomena. Temperature evolution is one of them. This problem includes various thermal flux and sources. More specifically, due to the train motion, a moving zigzag heat source occurs. This paper deals with a thermal 2D Alternating Direction Implicit (ADI) numerical method for temperature estimations in the train pantograph carbon strip, the aims being a better wear problems anticipation and the creation of a preventive maintenance. For that, an electrical model is coupled to the thermal one to take into account all Joule effects. The ADI strategy enables a significant computation time reduction against most classical resolution methods. Besides, the model involves two mathematical processes: the first one is an appropriate variable transform which induces a fixed surface heat production, while the second is based on locally refined meshes. Various numerical tests are presented and discussed in order to show the accuracy of the scheme. From a physical point of view, the results are much interesting. Further investigations, depending on the different parameters, should lead us to predict the strip critical thermal phases.

Rocket-Augmented Two Stage Runway Based Space Access Architecture

A runway-based space access system concept based on two stages to orbit is further refined. Routine access to Space with large payloads is essential for Space infrastructure projects such as solar power stations. The aim is to develop a reference architecture to enable cost estimation for a large reusable fleet. Prior work established that a 25000 kg payload could be delivered to low earth orbit starting with takeoff from a runway using a vehicle with the parameters of today’s large airliners. Hydrogen-fueled high-bypass turbofans provide efficient subsonic climb while oxygen is liquefied and stored. The second stage is launched at transonic speed at 18 kilometers altitude, followed by aerodynamic flight with ramjet, SCRAMjet and then rocket propulsion to orbit. A new feature is a brief rocket burn to fill the transonic ramjet performance gap, followed by ramjet-powered supersonic acceleration and climb. Beyond 60 km, SCRAMJET acceleration reaches the von Karman limit of 100km at Mach 8, beyond which rocket propulsion takes the craft to orbit. A refined initial mass estimation process allows the design to close swiftly, showing that payload capacity can be increased in future iterations with the same carrier aircraft parameters.

Robust Controller Design for Active Suspension Systems of Road Vehicles

The Linear Quadratic Gaussian (LQG) technique has been applied to the design of active vehicle suspensions (AVSs) for improving ride quality and handling performance. LQG-based AVSs have achieved good performance if an accurate vehicle model is available. However, these AVSs exhibit poor robustness when the vehicle model is not accurate and vehicle operating conditions vary. The H∞ control theory, rooted in the LQG technique, specifically targets on robustness issues on models with parametric uncertainties and un-modelled dynamics. In this research, an AVS is designed using the H∞ loop-shaping control, design optimization, and parallel computing techniques. The resulting AVS is compared against the baseline design through numerical simulations.

Development of Upper Extremity Finite Element Model for Elderly Female: Validated Against Dynamic Loading Conditions

Injuries to the upper extremities that are caused by dynamic impacts in crashes, including contact with internal instrument panels, has been a major concern, especially for smaller female occupants, and the problem worsens with increasing age due to reduced strength of the bones. From the analysis of 1988–2010 CDS unweighted data, it was found that risk of AIS ≥ 2 level for the arm was 58.2±20.6 percent higher in females than males, and the injury risk for a 75-year-old female occupant relative to a 21-year-old subjected to a similar physical insult was 4.2 times higher. Although injuries to upper extremities are typically not fatal, they can have long-term effects on overall quality of life. Therefore, it is important to minimize risks of injuries related to upper extremities, especially for elderly females, who are most at risk. Current anthropomorphic surrogates, like crash-test dummies, cannot be directly used to study injury limits, as these dummies were developed mainly to represent the younger population. The current study is focused on the development of a finite element (FE) model representing the upper extremity of an elderly female. This can be further used to analyze the injury mechanisms and tolerance limits for this vulnerable population. The FE mesh was developed through Computer Tomography (CT) scanned images of an elderly female cadaver, and the data included for validation of the developed model were taken from the experimental studies published in scientific literature, but only the data directly representing elderly females were used. It was found that the developed model could predict fractures in the long bones of elderly female specimens and could be further used for analyzing injury tolerances for this population. Further, it was determined that the developed segmental model could be integrated with the whole body FE model of the elderly female.

Slung Load Amplification Detector

Externally slung loads and their mission applications are becoming more common on human and autonomously piloted air vehicles. Flight speed is often limited not by the performance envelope but by the danger of divergent load oscillations. Certifying this limiting speed for every load-vehicle combination, is a huge barrier to operations. The conservatism dictated by this uncertainty may itself be life-threatening in critical applications. Computing the dynamics of slung loads for a specific load/vehicle combination has been hindered by lack of knowledge on bluffbody aeromechanics. The prevailing top-down approach is to incorporate slung load aeromechanics calculations into large comprehensive aeromechanics codes for rotorcraft. We argue for a bottom-up approach. This allows on-the-fly system identification and dynamics simulation. The Slung Load Amplification Detector (SLAD) concept provides an on-board safety system to predict, detect, avoid and alleviate divergent oscillations. SLAD is based on a knowledge base derived from wind tunnel data and simulation results including canonical geometries, as well as practical shapes. Validation of simulation results against two practical test cases lends confidence. SLAD allows reliable distinction between pseudo and absolute divergence, permitting an increase of as much as 50% speed in safe flight speed, and guidance on active alleviation of oscillations.

Pole Placement Near the Midwest Guardrail System

Poles are regularly placed along highways and are used to support signs, lights and electrical lines. The Midwest Guardrail System (MGS) is a standard W-beam guardrail system used throughout the United States to redirect vehicles that leave the roadway away from dangerous roadside obstacles, like ravines, water hazards, and bridge piers. Placing poles near a guardrail may affect its ability to safely contain and redirect vehicles. The compatibility of poles placed in the proximity of the MGS is studied using nonlinear finite element analysis. Computer simulations were conducted with vehicles impacting the MGS with varying lateral pole offsets between the back of the system and the front face of the pole, and varying longitudinal pole location from being placed directly behind a post to directly behind the unsupported rail half-way between posts. Results show that poles placed within 16 inches behind the MGS may cause concern in regard to acceptable crash test performance for guardrail systems. Additional simulations and full-scale crash testing is required before guidelines can be recommended.

Experimental Determination of the Efficiency of a Multi-Speed Bicycle Transmission

The efficiencies of gears in a multi-speed bicycle gearbox transmission were measured and efforts were taken to establish measurement repeatability. Data collected from this apparatus challenges manufacturers to improve their product lines. Given that cyclists are limited in their ability to sustain power supplied through pedaling, minimizing drivetrain losses is very important. Previous researchers have measured various bicycle drives, including chains and belts, multi-speed derailleur sets and multi-speed hub gear transmissions. This study continued to measure the efficiency of a Pinion P1.12 multi-speed crank transmission. Repeatability studies were performed using a custom apparatus, capable of providing a wide range of input speed, output power and configuration adjustments and the experiment procedure was adjusted accordingly. Efficiency was evaluated as the ratio of flywheel power to motor power over fourteen combinations of crank speed and output power for each gear. The means and 95% confidence intervals for these efficiencies were calculated, and a nonlinear regression was used to model the data as an exponential function of output torque. The mean of the means was calculated and fit with an exponential curve. Gear efficiency was determined to be the efficiency at infinite output torque, although this theoretical value is only approached at moderate cycling torques. Results indicate these transmissions are comparable to many modern multispeed geared bicycle hubs, ranging from 91.6–94.95%. Single-speed and derailleur systems can obtain higher efficiencies. However, the Pinion transmission provides enhanced reliability, reduced maintenance and relocates the majority of the drive weight to the middle of the bicycle. A repeatability study was conducted on the P1.12 transmission.

Evaluation of Ride Comfort in a Railway Passenger Vehicle With Integrated Vehicle and Human Body Bond Graph Model

Ride comfort is the level of comfort sensed by the passengers when they are continuously exposed to the vibration and noise. To diminish the vibration level, air springs are used in the secondary suspension system instead of coil springs, especially in the modern railway vehicles. This article focuses on the modeling of Nishimura air spring with non-linear damper and human biodynamic (bio-mechanical) model by using multi-energy domain modeling approach, bond graph. The car body of the railway vehicle is treated as a beam and the first five modes including three flexible modes are considered in the model. We use International Organization for Standardization 2631 for evaluating ride comfort for different durations of the travel time (1 h, 2.5 h, 4 h and 8 h) on flexible and irregular tracks.