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Technical Paper

Accelerated Degradation of Li-Ion Batteries for High Rate Discharge Applications

The U.S. Army has been pursuing vehicle electrification to achieve enhanced combat effectiveness. The benefits include new capabilities that require high power pulse duty cycles. However as the vehicle platform size decreases, the Energy Storage System (ESS) pulse power discharge rates (> 40 C rate) to support system requirements can be significantly greater than commercial ESS. Results are reported of high power pulse duty cycles on lithium iron phosphate cells that show a dramatic loss in lifetime performance. For a 2 s and 3 s pulse duration tests, the observed degradation is 22 % and 32 % respectively. Although these cells were thermally managed in a convective chamber at 10°C, the 2 s pulse showed a 31°C temperature rise and the 3 s pulse, a 48°C temperature rise. The decreased lifetime is attributed to increased lithium loss due to the increased temperature during pulse discharging.
Journal Article

Research on Intelligent Layout of Door Hinge Based on CATIA CAA

As one of the most important auto-body moving parts, door hinge is the key point of door design and its accessories arrangement, also the premise of the door kinematic analysis. We proposed an effective layout procedure for door hinge and developed an intelligent system on CATIA CAA platform to execute it. One toolbar and five function modules are constructed - Axis Arrangement, Section, Parting Line, Kinematic, Hinge Database. This system integrated geometrical algorithms, automatically calculate the minimum clearances between doors, fender and hinges on sections to judge if the layout is feasible. As the sizes of the clearances are set to 0s, the feasible layout regions and extreme start/end points are shown in parts window, which help the engineer to check the parting line and design a new one. Our system successfully implemented the functions of five modules for the layout of door hinge axis and parting line based on a door hinge database.
Journal Article

Front Rail Crashworthiness Design for Front Oblique Impact Using a Magic Cube Approach

The front rail, as one main energy absorption component of vehicle front structures, should present steady progressive collapse along its axis and avoid bending collapse during the front oblique impact, but when the angle of loading direction is larger than some critical angle, it will appear bending collapse causing reduced capability of crash energy absorption. This paper is concerned with crashworthiness design of the front rail on a vehicle chassis frame structure considering uncertain crash directions. The objective is to improve the crash direction adaptability of the front rail, without deteriorating the vehicle's crashworthiness performance. Magic Cube (MQ) approach, a systematic design approach, is conducted to analyze the design problem. By applying Space Decomposition of MQ, an equivalent model of the vehicle chassis frame is generated, which simplifies the design problem.
Technical Paper

Technical Challenges for Vehicle 14V/28V Lithium Ion Battery Replacement

Modern commercial and military vehicles are equipped with more electrical accessories and demand more power than ever before. This causes an increase in the weight of the battery as well as drives the battery to end of life when the vehicle is stationary with the engine off. Lithium ion batteries, which are known for their high power and energy to weight density, long cycle life, and low self-discharge rate, are considered to be an alternative for the replacement of existing Starting, Lighting, and Ignition (SLI) lead acid batteries. Lithium ion battery chemistry offers double the reserve time of the stock battery and a significantly greater number of charging and discharging cycles while providing weight savings. There is no acid inside a lithium ion battery to cause corrosion, which eliminates potential damage to a vehicle from chemical spills and poisonous gases.
Technical Paper

Hydrogen Consumption Measurement for Fuel Cell Vehicles

Fuel cell vehicle fuel consumption measurement is considerably different from internal combustion engine vehicle fuel consumption measurement. Conventional Carbon Balance Method and Flow Measurement methods for gas consumption within combustion engines are not suitable for fuel cell vehicles. The small quantities of fuel consumed and the characteristics of hydrogen itself impose a challenge for the hydrogen measurement. This paper addresses fuel consumption measurement for fuel cell vehicles using various methods such as mass flow measurement, pressure/temperature/volume method, weigh method as well as other methods. The advantages and disadvantages of these methods are discussed.
Technical Paper

Hydrogen Fuel Cell Vehicle Fuel Economy Measurements and Calculation

Hydrogen Fuel cell vehicles, and techniques for fuel economy measurement and fuel economy calculations are considerably different from those traditionally used fro combustion engine vehicles.. Like gasoline or diesel hybrid vehicles, fuel cell vehicles typically use batteries or other power systems such as super-capacitors for load leveling. Thus, the energy transfer or consumption from these supplemental power sources to the drive train should be compensated for when determining fuel consumption or fuel economy. This paper addresses fuel economy calculations and testing for hybrid hydrogen fuel cell vehicles. The impact of supplemental power systems to a fuel cell vehicle's fuel economy and the various methods to derive actual vehicle fuel economy with supplemental power system usage are discussed.