On the Development of Frame Analysis Program to Simulate Automotive Frame using Direct Dynamic Stiffness Approach

There are many frame analysis programs in the industry, but none of them use the direct dynamic stiffness approach to simulate the frequency response of frames. The Frequency Response Functions (FRF) computation is an important step in determining Noise, Vibration and Harshness (NVH) of any automotive vehicle. Usually, a CAE engineer in the automotive industry will first compute the modal characteristic of the frame component or full body/trim structure, and then compute the frequency response functions to aid in the determination of its ability to withstand the random road load input applied on the structure. There exists an alternate approach to compute the frequency response functions on structures without the need to compute its modal characteristics. This direct method of FRF computation is based on using the direct dynamic stiffness influence computations in conjunction with the classical finite element analysis procedure.

The mathematics of the dynamic stiffness influence coefficients approach is discussed in detail by the author in a previous paper [1]. In this paper, the plane and space frame models are discussed, and associated analysis programs are written and tested based on the dynamic stiffness influence coefficients approach. The matrix equations used in the development of this plane or frame analysis program will be discussed in this paper. The software will be developed in the MATLAB programming language. Three structural examples are used for the program validation. One is a portal frame, second is a continuous beam with a spring in between the ends, and the third is a three dimensional frame.