F2010C221
Fatigue Life Prediction of a Bus Body Structure using CAE Tools
The new vehicle development process requires an appropriate durability based design with actual service loads. In the early design phase of vehicle development computer aided durability analysis will be helpful to predict life cycle design issues before high cost prototype vehicle production and physical tests. Over the last few decades, FE methods have been widely utilized for structural analysis but CAE tools have limited usage for fatigue life estimation due to difficulties in determination of the major inputs of fatigue analysis such as loading data and the cyclic properties of the material.
In this paper, an integrated computer aided durability analysis method is proposed for durability estimation of a city bus with actual test rig data.
The load history derived by running accelerated actual test rig data on multi-body dynamics model. For multi-body dynamic analysis to obtain time dependent load data acting on structure, a general purpose multi-body dynamic analysis code ADAMS/Car is used. The multi-body dynamic model of the prototype bus is composed of suspension, power train, steering, brake systems and a flexible body structure. The body structure is modeled as a flexible body to consider flexibility affect. Also realistic behavior of suspension established with modeling air suspension in EASY5 and co-simulating with ADAMS/Car. In order to obtain time independent part of the fatigue analysis such as stress coefficients, a general purpose finite element analysis code MSC/NASTRAN is used. MSC Fatigue database is used for material properties.
Finding the loading information is not the only problem to overcome for fatigue analysis of the body structure. Fatigue analysis of large structures like bus frame often requires detailed modeling of critical regions such as welded areas since the stiffness of this small portions reflects the stiffness of the global structure, some sub-modeling techniques were used isolating welded regions from the entire body.
The durability of prototype vehicle has been estimated in accelerated test rig and fatigue analysis results compared for developing comprehensive simulation methodology. With the proposed computational methodology, an efficient and reliable structural development capability gained in finding design issues in the early design phases.
This abstract is supplemented by a PDF, which can be viewed here.
Session: Buses