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In the early history of engineering, the engineer was an integrator of many technologies. With the advent of the digital computer in the mid 1950's this began to subtly change as the demands of implementing various analytical methods on digital computers tended to focus engineers on the analysis of a single discipline such as structural mechanics. This revolution in engineering practice is reaching maturity after almost 40 years of intensive research. For such fields as rigid body mechanics, structures, and fluid mechanics, computational methods exist which span a range from simple techniques to full implementations of the underlying field equations. This paper will argue that the remaining part of the revolution in engineering should refocus on the engineer as a generalist by using the computational techniques in a more integrated fashion. To accomplish this, work that needs to be carried out in several areas will be discussed.

Since the introduction of structural optimization as a tool in the automotive structural design process, a considerable body of experience has been obtained in its practical application to automotive design. It is the purpose of this paper to illustrate this experience by means of several structural optimization examples of the basic load-carrying skeleton and a more detailed model of a panel structure. A complex comparative configuration study will be presented which considers several alternative configurations for front structures. The results of this study indicate that the redundancy of load paths in the automotive structure will allow reduced load capacity in one part of the structure to be compensated for in some other load path. In many cases, alternative configurations may produce approximately equal optimum mass structures. It is concluded that structural optimization offers a unique ability to give high-quality design direction in the early phases of the structural design.

Previous work in structural optimization for the automotive structure has been limited to beam models of the major load-carrying structure. This was primarily done to reduce the amount of computer resources required to minimize the mass. In this study, techniques necessary to include a moderately complex representation of the panels are developed in which some compromises between model fidelity and solution time must be accepted. As an example, plate elements have been included in a vehicle structural optimization model to represent the roof, floor, dash, motor compartment, and rear quarter. Minimum mass designs subjected to stress, displacement, and frequency constraints are obtained by structural optimization. It was found that most panels were at minimum gage in the optimum design. This suggests that these panels are designed by local criteria as opposed to being controlled by global load and stiffness criteria.

A two-tier approach is applied to the analysis of a cab-over-engine tractor. A detailed three-dimensional finite element model was developed and verified with data acquired from road input. In addition, a simpler two-dimensional model was developed and used with an optimization technique to develop alternative designs. The root-mean-square accelerations of the driver in the vertical and fore-aft directions were used as performance measures. The proposed designs were then evaluated using the detailed finite element model, and additional improvements were suggested. This approach led to a modification of the cab mounting system which resulted in a predicted 44 percent reduction in the fore-aft rms acceleration from an initial design.

It is hypothesized that the potential value of powered lift may be greater for transport applications requiring RTOL and CTOL field lengths than for those requiring STOL performance. Thus, it is implied that powered lift can be applied effectively to aircraft designed for medium and long haul, as well as short haul. This premise has been reached on the basis of observed trends in direct operating cost, mission fuel consumption, and, most significantly, community noise footprint areas for both powered lift and conventional mechanical flap configurations. Some pertinent results from recent NASA-sponsored configuration design and system studies for quiet short haul and fuel-conservative aircraft are discussed, and further data are developed to explore the potential value of incorporating powered lift concepts in advanced aircraft designs for medium and long haul applications.

A review is presented of low-noise airplanes designed for operation in the 1980 time period. Aircraft with parametric engines covering a range of fan pressure ratios and noise levels were developed conceptually under contract with NASA Advanced Concepts and Missions Division, supported by the NASA Lewis Research Center contracts for the Quiet Clean STOL Experimental Engine (QCSEE) Study Program. Powered-lift concepts included externally blown flap, augmentor wing, internally blown flap, and over-the-wing upper surface blowing. Performance, sizing, and costs are described for 148 passenger airplanes with design field length varying from 2000-4000 ft. Techniques for reducing noise are evaluated in terms of aircraft performance, weight, and cost; experimental data on decayer nozzles are presented and assessed with respect to effectiveness in exhaust noise reduction and aircraft performance penalties.