Access Type

Open Access Dissertation

Date of Award

January 2016

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Mechanical Engineering

First Advisor

Chin-An Tan

Abstract

The Arbitrary Lagrangian-Eulerian (ALE) is a hybrid finite element formulation that can alleviate many of the drawbacks from the traditional Lagrangian-based and Eulerian-based finite element simulations, which is developed through combining modern algorithms for Lagrangian hydrodynamics, meshing technology and remap methods developed for high-resolution Eulerian methods. Lagrangian-based finite element formulations is that the computational system moves with the material and main drawback is that it will face severe problems to deal with strong distortions in the computational domain. Eulerian-based finite element formulations is that the computational system is a prior fixed in space and unable to deal easily with fluids undergo large distortions at the interface. The use of Arbitrary Lagrangian-Eulerian (ALE) computer codes has been an enabling technology for many important applications. When using the ALE technique in engineering simulations, the computational mesh inside the domains can move arbitrarily to optimize the shapes of elements, while the mesh on the boundaries and interfaces of the domains can move along with materials to precisely track the boundaries and interfaces of a multi-material system.

In automotive CAE durability analysis, simulation of dynamic stress and fatigue life of fuel tank straps is a complex problem. Typically a fuel tank is held with fuel tank straps. Its movement lies in the domain of nonlinear large rotation dynamics. Moreover, the sloshing behavior in the fuel tank makes the problem even more intricate.

The objective of this study is to investigate the advantage of ALE method in simulating fuel sloshing through fuel tank and fuel tank strap movement under proving ground conditions using the nonlinear large rotation dynamic method with RADIOSS, a commercial code. After the stress distribution of the fuel tank strap is achieved, a commercial fatigue code, nCode DesignLife, is used to predict the fatigue life of the fuel tank straps.

In this research, the stress distribution of the fuel tank strap can be predicted with Arbitrary Lagrangian-Eulerian Method (ALE) to simulate fuel sloshing which plays critical role in fuel mass redistribution and the stress variation with time. A commercial fatigue code, nCode DesignLife, is used to predict the fatigue life of the fuel tank straps. The analyses have accurately predicted the crack initiation location and sequence in the fuel tank straps, and show good correlation with test. The utilization of this method can give design direction to minimize the iteration of lab testing and expedite the design period.

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