1990-02-01

Improving Vehicle Response to Engine and Road Excitation Using Interactive Graphics and Modal Reanalysis Methods 900817

In the initial design stages of a vehicle, one desires to analyze and improve the response of the vehicle when sitting at idle or when travelling down various roads. One can perform such analyses and improvements to an FEM model using NASTRAN. However, a faster and easier method has been developed into a postprocessor to NASTRAN called FASTAR.Initially FASTAR was created to supplement NASTRAN by providing interactive graphics modal animation, structural modifications, and sinusoidal frequency response using a reduced modal space. With greater emphasis on vehicle analysis, FASTAR has been modified to process much more complicated loads generated by engines and road profiles. To simplify user input, engine data and road data have been integrated into two comprehensive data bases.As a result, one can now very easily choose in FASTAR specific engines and quickly compute the engine induced vehicle response. As in the lab, one can get either primary, peak, sum or average response values by selecting the appropriate filter option when plotting the response.Similarly, road profile data has been gathered into another data base for the various road surfaces. For vehicle ride, one can step through several different road profiles and calculate the PSD acceleration in dB units once the transfer functions have been calculated.The theory to generate such complex loads will be discussed along with selected applications. Our examples will show that using a program such as FASTAR can increase substantially the productivity of an analyst.

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