Utpal Dutta

True Walking Distance to Transit

Abstract People riding transit in the city of Detroit walk on average 0.8 miles (1.3 km) per round trip. The straight-line walking distance was found by buffering the bus stop locations and comparing them to the weighted US Census blocks. However, the true walking path follows the street pattern. Rather than undertaking network analysis, which would require connecting all addresses in the city with all bus stops, a Monte Carlo simulation was performed in geographic information system with random addresses. The simulation was performed over several addresses until convergence was achieved. The distances were converted to walking times and compared to the US National Household Transportation Survey.

Laboratory performance of ASR modified asphalt binders

Automobiles, when they are no longer useful, are flattened and shipped to an automotive shredder facility. At the shredder facility, while they are shredded to recover the ferrous and non-ferrous metals for recycling, a huge quantity of non-metallic residue commonly called Automotive Shredder Residue (ASR) is generated. Since ASR mostly contains plastic and rubber related materials, and addition of plastic and scrap rubber from waste tires as a road material has been proven to be effective in solving existing pavement related problems, attempts were made to examine the feasibility of ASR as a road material additive. As a part of this effort, compatibility and mechanical properties of ASR modified asphalt were studied. The asphalt was mixed with a requisite amount of ASR for one hour at 375°F. Glass transition temperature (Tg) and microstructure of ASR, asphalt and ASR modified as-phalt were examined to determine compatibility. Mechanical properties of ASR modified asphalt were studied by performing dynamic mechanical analysis. The photomicrographs and Tg of ASR modified asphalt demonstrated some compatibility between ASR and asphalt. Dynamic mechanical analysis indicated that rutting and aging properties of asphalt should improve with the addition of ASR.

A practical approach for cross-functional vehicle body weight optimization

The goal of optimization in vehicle design is often blurred by the myriads of requirements belonging to attributes that may not be quite related. If solutions are sought by optimizing attribute performance-related objectives separately starting with a common baseline design configuration as in a traditional design environment, it becomes an arduous task to integrate the potentially conflicting solutions into one satisfactory design. It may be thus more desirable to carry out a combined multi-disciplinary design optimization (MDO) with vehicle weight as an objective function and cross-functional attribute performance targets as constraints. For the particular case of vehicle body structure design, the initial design is likely to be arrived at taking into account styling, packaging and market-driven requirements. The problem with performing a combined cross-functional optimization is the time associated with running such CAE algorithms that can provide a single optimal solution for heterogeneous areas such as NVH and crash safety. In the present paper, a practical MDO methodology is suggested that can be applied to weight optimization of automotive body structures by specifying constraints on frequency and crash performance. Because of the reduced number of cases to be analyzed for crash safety in comparison with other MDO approaches, the present methodology can generate a single size-optimized solution without having to take recourse to empirical techniques such as response surface-based prediction of crash performance and associated successive response surface updating for convergence. An example of weight optimization of spaceframe-based BIW of an aluminum-intensive vehicle is given to illustrate the steps involved in the current optimization process.