Analysis, Modeling and CAE Validation of Vehicle Crashes using Advanced Signal Processing Tools

Doktorgradsavhandling ved Fakultet for teknologi og realfag, Universitetet i Agder, 2017Road safety is one of the hot-spot issues in modern society and covers many aspects of traffic system. Vehicle safety plays an important role in reducing the casualties and saving the accident cost. Up to now, a lot of efforts have been made to improve vehicle safety on both passive and active aspects, such as optimizing the vehicle structure, updating the vehicle dynamic control algorithm and developing driving assistant system. Considering the fact that traffic accidents cannot be completely avoided, passive safety of vehicle are seriously concerned by researchers, manufactures and consumers. Modeling of vehicle crash process is a challenging problem, which has been widely studied and will remain a topic of interest in the future. With the developing of Computer Aided Engineering (CAE) technology (e.g. multi-body theory, nonlinear finite element method), detailed numerical models are used in various areas of vehicle safety. However, the development and utilization of numerical models are generally time consuming and costly. At the same time, mathematical models are usually built without clear physical interpretation, although they have advantages in some applications. The existing mathematical models have limitations in adaptation to different crash conditions. This thesis is mainly about the investigation of vehicle crash process based on the time-frequency analysis of the crash responses (i.e. the accelerations of vehicle structure). The essential idea of this work is to building the mathematical relationship between vehicle structures and crash responses. The data used in this work come from the NCAP crash tests and finite element crash simulations of Toyota Yaris. Paper A illustrates the typical load paths of vehicle frontal structure firstly. According to the energy absorbing features of crashworthiness components, a piecewise model is proposed to represent frontal crashes. The proposed model is built by analyzing the crash response, engine accelerations and external barrier force. Moreover, the model variance in different cases, including crashes with different impact velocities and oblique crashes, are also discussed. Papers B and C introduce Ensemble Empirical Mode Decomposition (EEMD) method into crash response analyzing. EEMD is a time-frequency analysis technology, which is suitable for nonlinear and non-stationary signals. Paper B studies the signal transmission in vehicle components and illustrates how the deformations of components influence the crash responses. Paper C proposes an integrated algorithm to identify the performance of energy absorbing components during crashes by both low frequency trend and high frequency oscillations of the response signal. Two cases, low speed crash and oblique crash, are also studied in this work. Paper D presents a modeling scheme of vehicle crash, as well as an estimation method of crashes with different velocities. Specifically, the parameters of proposed model are identified from the data of corresponding NCAP 56km/h frontal crash test, which is available for most vehicles. For the crash process estimation, the crashes are catalogued into light, moderate and sever types, according to the deformed components. For the crashes in different catalogues, the structures and parameters of piecewise models may vary consequently. For this reason, the estimation algorithms of three types of car crashes are developed separately. Examples are also given for these three cases. Finally, Paper E discusses the application of EEMD in the validation of CAE simulations. The proposed scheme compares the trend and oscillations of original signal separately and involves more features to achieve better validation performance. In conclusion, this thesis involves the signal processing technologies into the analysis, modeling and CAE model validation of vehicle frontal crashes. It benefits the understanding of vehicle crash processes and helps to achieve better safety design of vehicle. Some future work should be continued for car crashes in more complex conditions

A Data-Based Approach for Modeling and Analysis of Vehicle Collision by LPV-ARMAX Models

Vehicle crash test is considered to be the most direct and common approach to assess the vehicle crashworthiness. However, it suffers from the drawbacks of high experiment cost and huge time consumption. Therefore, the establishment of a mathematical model of vehicle crash which can simplify the analysis process is significantly attractive. In this paper, we present the application of LPV-ARMAX model to simulate the car-to-pole collision with different initial impact velocities. The parameters of the LPV-ARMAX are assumed to have dependence on the initial impact velocities. Instead of establishing a set of LTI models for vehicle crashes with various impact velocities, the LPV-ARMAX model is comparatively simple and applicable to predict the responses of new collision situations different from the ones used for identification. Finally, the comparison between the predicted response and the real test data is conducted, which shows the high fidelity of the LPV-ARMAX model

2005 Engineering Annual Report

Selected research and technology activities at Dryden Flight Research Center are summarized. These activities exemplify the Center's varied and productive research efforts

Mathematical Modelling and Analysis of Vehicle Frontal Crash using Lumped Parameters Models

A full-scale crash test is conventionally used for vehicle crashworthiness analysis. However, this approach is expensive and time-consuming. Vehicle crash reconstructions using different numerical modelling approaches can predict vehicle behavior and reduce the need for multiple full-scale crash tests, thus research on the crash reconstruction has received a great attention in the last few decades. Among modelling approaches, lumped parameters models (LPM) and finite element models (FEM) are commonly used in the vehicle crash reconstruction. This thesis focuses on developing and improving the LPM for vehicle frontal crash analysis. The study aims at reconstructing crash scenarios for vehicle-to-barrier (VTB), vehicleoccupant (V-Occ), and vehicle-to-vehicle (VTV), respectively. In this study, a single mass-spring-damper (MSD) is used to simulate a vehicle to-barrier or a wall. A double MSD is used to model the response of the chassis and passenger compartment in a frontal crash, a vehicle-occupant, and a vehicle-tovehicle, respectively. A curve fitting, state-space, and genetic algorithm are used to estimate parameters of the model for reconstructing the vehicle crash kinematics. Further, the piecewise LPM is developed to mimic the crash characteristics for VTB, VO, and VTV crash scenarios, and its predictive capability is compared with the explicit FEM. Within the framework, the advantages of the proposed methods are explained in detail, and suggested solutions are presented to address the limitations in the study.publishedVersio

Railway Research

This book focuses on selected research problems of contemporary railways. The first chapter is devoted to the prediction of railways development in the nearest future. The second chapter discusses safety and security problems in general, precisely from the system point of view. In the third chapter, both the general approach and a particular case study of a critical incident with regard to railway safety are presented. In the fourth chapter, the question of railway infrastructure studies is presented, which is devoted to track superstructure. In the fifth chapter, the modern system for the technical condition monitoring of railway tracks is discussed. The compact on-board sensing device is presented. The last chapter focuses on modeling railway vehicle dynamics using numerical simulation, where the dynamical models are exploited

SOLID-SHELL FINITE ELEMENT MODELS FOR EXPLICIT SIMULATIONS OF CRACK PROPAGATION IN THIN STRUCTURES

Crack propagation in thin shell structures due to cutting is conveniently simulated using explicit finite element approaches, in view of the high nonlinearity of the problem. Solidshell elements are usually preferred for the discretization in the presence of complex material behavior and degradation phenomena such as delamination, since they allow for a correct representation of the thickness geometry. However, in solid-shell elements the small thickness leads to a very high maximum eigenfrequency, which imply very small stable time-steps. A new selective mass scaling technique is proposed to increase the time-step size without affecting accuracy. New ”directional” cohesive interface elements are used in conjunction with selective mass scaling to account for the interaction with a sharp blade in cutting processes of thin ductile shells

Piezoelectric-based in-situ damage detection of composite materials for structural health monitoring systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002.Includes bibliographical references (p. 151-160).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cost-effective and reliable damage detection is critical for the utilization of composite materials. This thesis presents the conclusions of an analytical and experimental survey of candidate methods for in-situ damage detection in composite materials. Finite element results are presented for the application of modal analysis and Lamb wave techniques to quasi-isotropic graphite/epoxy test specimens containing representative damage. These results were then verified experimentally by using piezoelectric patches as actuators and sensors for both sets of experiments. The passive modal analysis method was reliable for detecting small amounts of global damage in a simple composite structures. By comparison, the active Lamb wave method was sensitive to all types of local damage present between the sensor and actuator, provided useful information about damage presence and severity, and presents the possibility of estimating damage type and location. Analogous experiments were also performed for more complex built-up structures such as sandwich beams, stiffened plates and composite cylinders.(cont.) These techniques have proven suitable for structural health monitoring applications since they can be applied with low power conformable sensors and can provide useful information about the state of a structure during operation. Piezoelectric patches could also be used as multipurpose sensors to test using a variety of methods such as modal analysis, Lamb wave, acoustic emission and strain based methods simultaneously by altering driving frequencies and sampling rates. Guidelines and recommendations drawn from this research are presented to assist in the design of a structural health monitoring system for a vehicle, and provides a detailed example of a SHM system architecture. These systems will be an important component in future designs of air and spacecraft to increase the feasibility of their missions.by Seth Stovack Kessler.Ph.D

Fuzzy Logic

The capability of Fuzzy Logic in the development of emerging technologies is introduced in this book. The book consists of sixteen chapters showing various applications in the field of Bioinformatics, Health, Security, Communications, Transportations, Financial Management, Energy and Environment Systems. This book is a major reference source for all those concerned with applied intelligent systems. The intended readers are researchers, engineers, medical practitioners, and graduate students interested in fuzzy logic systems

Proceedings of the 2018 Joint Workshop of Fraunhofer IOSB and Institute for Anthropomatics, Vision and Fusion Laboratory

The Proceeding of the annual joint workshop of the Fraunhofer IOSB and the Vision and Fusion Laboratory (IES) 2018 of the KIT contain technical reports of the PhD-stundents on the status of their research. The discussed topics ranging from computer vision and optical metrology to network security and machine learning. This volume provides a comprehensive and up-to-date overview of the research program of the IES Laboratory and the Fraunhofer IOSB

Reduced-Order Modeling of Unsteady Aerodynamics Across Multiple Mach Regimes.

The accurate prediction of unsteady aerodynamic loads is of utmost importance in an aeroelastic simulation framework. Inaccurate prediction of these loads may result in inaccurate control design and evaluation, which, in a worst-case scenario, could cause loss of control of the vehicle. In addition to accuracy, these simulations require that the aerodynamic calculations be computationally efficient, so this often eliminates the use of full-order computational fluid dynamics (CFD) simulations, which can be quite computationally-intensive. Reduced-order models (ROMs) offer a solution to these competing demands of accuracy and efficiency by extracting pertinent data from a limited number of full-order CFD simulations and using that data to construct computationally-efficient models that retain a high amount of the accuracy of the full order solution while running orders of magnitude faster computationally. This dissertation focuses on the development of a reduced-order modeling methodology for unsteady aerodynamics based on linear convolution combined with a nonlinear correction factor. Rather than being limited to a specific Mach regime, the ROM formulation is general enough such that it can be applied over a wide range of Mach regimes, from subsonic to hypersonic flight. The correction factor term allows the ROM to be accurate over a range of vehicle elastic modal deformation amplitudes as well as flight conditions representing off-design conditions. This generality is important because it permits a single form of the equations for aerodynamic loads to be used throughout all simulations in a controls framework, further increasing the efficiency. The evaluation of the ROM is accomplished through the comparison of ROM results with full-order CFD simulations for test-case geometries in the subsonic, transonic, and super/hypersonic regimes. Additionally, methods for ROM construction are explored, including the development of a simplified aerodynamic model in the transonic regime for use in aiding ROM construction. Overall, good agreement is obtained between the ROM and CFD results, generally improving as Mach number increases. The potential of the ROM is illustrated by following a single example case from low subsonic up through supersonic flight, thus demonstrating the usefulness of the approach over a wide range of conditions.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/97977/1/tskujins_1.pd