## Electronic Theses and Dissertations

8-2005

#### Document Type

Doctoral Dissertation

Ph. D.

#### Department

Mechanical Engineering

Day, Michael L.

#### Author's Keywords

Crashworthiness; Channel section beams; Thin-walled beams; Vehicle chassis

#### Subject

Automobiles--Crashworthiness

#### Abstract

Simplified modeling generates a great deal of interest in the area of crashworthiness analysis. Modeling methods used to create simplified computer models for crashworthiness have been well developed. In advanced simplified models, researchers develop simplified elements that can correctly predict structure's crash behavior based on the existing collapse theories. These developed simplified elements then are applied to develop the simplified models. Nevertheless, most of the exiting collapse theories are regarding the thin-walled box section beams. However, in addition to the box section member, the channel section member is another popular member and is widely used in engineering for architectural structures, vehicles, and etc. Therefore, to simplify the thin-walled channel section beams, new collapse theory is required to predict the crash behavior for such beams. This topic is the focus of this dissertation. This dissertation develops a mathematical model to predict the crash behavior of the thin-walled channel section beams based on their real collapse mechanisms. The derived math formulae are verified through several basic applications. After that, both the existing collapse theories and the developed collapse theory regarding the thin-walled channel section beams are applied to simplify the detailed truck chassis model. The developed simplified model is used for crashworthiness analysis and the results are compared to those from the detailed model. The developed theory and the modeling method are then validated through the comparison. Additionally, in developing the simplified truck chassis model, the cross members that were modeled using coarse shell elements in previous simplified models are remodeled using simple elements. Two of the simplified modeling methods, the superelement method and the equivalent beam method, are utilized to generate the simplified models for the cross members of the truck chassis model. The principle of both methods is to use simple elements to transfer the original members' mass and stiffness matrices. The equivalent beam method is recommended after comparison of the results of the crashworthiness analyses of each method. The primary contributions of this work are first, the derivation of crash theory that can predict the crash behavior of thin-walled channel section beams. The second is the use of equivalent beams to simplify the cross members within truck chassis models. Finally, a simplified modeling methodology is presented and evaluated. All the theory and modeling method developed in this work are applied for creating simplified models. Both the simplified and detailed models are used for crashworthiness analyses, results show that the errors caused by the simplified models are fewer than 10% and the simplified models only take less than 10% of the computer time of the corresponding detailed models.

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