Abstract
Research and/or Engineering Questions/Objective
Nowadays, in automotive industry, the integration of Computer Aided Engineering (CAE) tools into System Engineering Approach according to the V-Cycle is becoming more and more relevant. Numerical tools allow to verify properties on virtual prototypes although, the end validation of a new truck design still requires physical tests. The physical validation can be enhanced when proper boundary conditions are found, such that full-vehicle-equivalent loading mechanisms are applied to the systems. Typically, the process of isolating and applying equivalent boundary conditions to systems is not trivial, especially with flexible bodies like truck chassis. In this paper, an innovative CAE approach for determining the first-time-right setup and boundary conditions for durability test rigs is presented and applied to an industry-relevant case.
Methodology
Among CAE tools, the Finite Element Method (FEM) has high relevance in structural analysis. Due to its formulation, FEM requires detailed information, which is initially not available. The approach presented here defines a reduced FEM formulation, describing the analytical relationship between loads and targets (i.e. stress, displacement). The optimal rig´s constraint is iteratively searched within a design space, which represents all the possible engineering solutions (i.e. fixation points,…). Due to the high efficiency of the presented formulation, a fast exploration of the design space is performed, yielding a series of test rig configurations and loads: the accuracy of the obtained virtual test rigs can be enhanced (i.e. increasing number of actuators) in order to reach the required level of quality. The efficient and extensive exploration of the design space guarantees the existence of solutions, whereas the bottom-up approach ensures that simpler and cheaper configurations are analyzed first.
Results
The main outcome of the method is the virtual model (CAE) of test rig, consisting of the specimen/system to be tested, the (minimally needed) surrounding components and the boundary conditions, in terms of constraints and actuator forces. The method is applied to and validated on the design of a test rig for experimental fatigue analysis of a chassis cross member, which is highly relevant for and influenced by the full vehicle behavior. Key Performance Indicators (KPIs) of the virtual rig such as local stresses, relative displacements and cross-section forces are compared with the ones calculated in the full vehicle analysis, used as reference.
Limitations of this study
The core of the method is based on mathematically exact but linear relationships and linear FE analysis: this partially limits the applicability to linear optimization targets, such as stress components, displacements and forces.
What does the paper offer that is new in the field including in comparison to other work by the authors?
The presented study illustrates an innovative approach for CAE-based design of test rigs, with respect to accuracy and robustness. Given by its formulation, the proposed CAE approach supports the test rig design from its early stages up to the physical calibration phase. Conclusions- The new method for CAE-driven design of test rigs is developed and successfully applied on a truck with an air sprung front axle design. The method proved to give very accurate and robust results.
KEYWORDS: Truck design, Durability, Test Rig, Inverse Problem, Optimization, CAE