Formula SAE Monocoque Chassis Development

Formula SAE is a collegiate competition hosted by SAE International with the primary goal being to design, manufacture, and race an open wheel race car. The Cal Poly Racing Formula SAE team strives for improvement every race season and has remained competitive as a result. The 2019-2020 management team determined that further research and development towards the chassis would yield the greatest performance benefit for future seasons, as the previous chassis platform limited packaging and mounting options for vehicle subsystems which interfaced with the chassis. A redesign of the Cal Poly Racing Formula SAE team’s carbon fiber reinforced polymer monocoque chassis was requested to improve subsystem integration, increase torsional stiffness, and reduce weight compared to the previous platform. Specifically, this senior project team focused on manufacturing process improvement and laminate design to meet these goals for the 2020 Formula SAE competition. This report details the design and manufacturing of such a chassis. Specific emphasis was placed on the geometry, laminate, and manufacturing process design. The geometry was designed using subsystem input for satisfactory integration of all subsystem components while maintaining a high specific torsional stiffness. The team also developed numerous analysis tools including spreadsheets and finite element models to design the asymmetric laminate of the chassis. Modular, multi-piece tooling was designed to produce a single-piece chassis and to allow for easy geometric changes in the future. Though two complete chassis were delivered to the Formula SAE team, the outbreak of COVID-19 prevented the collection of data that would have been used to validate the design. However, the Formula SAE team was made aware of the validation plan proposed in this report

AN INTEGRATED SYSTEMS ENGINEERING METHODOLOGY FOR DESIGN OF VEHICLE HANDLING DYNAMICS

The primary objective of this research is to develop an integrated system engineering methodology for the conceptual design of vehicle handling dynamics early on in the product development process. A systems engineering-based simulation framework is developed that connects subjective, customer-relevant handling expectations and manufacturers\u27 brand attributes to higher-level objective vehicle engineering targets and consequently breaks these targets down into subsystem-level requirements and component-level design specifications. Such an integrated systems engineering approach will guide the engineering development process and provide insight into the compromises involved in the vehicle-handling layout, ultimately saving product development time and costs and helping to achieve a higher level of product maturity early on in the design phase. The proposed simulation-based design methodology for the conceptual design of vehicle handling characteristics is implemented using decomposition-based Analytical Target Cascading (ATC) techniques and evolutionary, multi-objective optimization algorithms coupled within the systems engineering framework. The framework is utilized in a two-layer optimization schedule. The first layer is used to derive subsystem-level requirements from overall vehicle-level targets. These subsystem-level requirements are passed on as targets to the second layer of optimization, and the second layer derives component-level specifications from the subsystem-level requirements obtained from the first step. The second layer optimization utilizes component-level design variables and analysis models to minimize the difference between the targets transferred from the vehicle level and responses generated from the component-level analysis. An iterative loop is set up with an objective to minimize the target/response consistency constraints (i.e., the targets at the vehicle level are constantly rebalanced to achieve a consistent and feasible solution). Genetic Algorithms (GAs) are used at each layer of the framework. This work has contributed towards development of a unique approach to integrate market research into the vehicle handling design process. The framework developed for this dissertation uses Original Equipment Manufacturer\u27s (OEM\u27s) brand essence information derived from market research for the derivation and balancing of vehicle-level targets, and guides the chassis design direction using relative brand attribute weights. Other contributions from this research include development of empirical relationships between key customer-relevant vehicle handling attributes selected from market survey and the various scenarios and objective metrics of vehicle handling, development of a goal programming based approach for the selection of the best solution from a set of Pareto-optimal solutions obtained from genetic algorithms and development of Vehicle Handling Bandwidth Diagrams

An improved powertrain attributes development process with the use of design structure matrix

Thesis (S.M.)--Massachusetts Institute of Technology, System Design & Management Program, 2004.Includes bibliographical references (p. 131).Automobiles are becoming increasingly complicated and are creating more of a challenge for the engineering teams working on them. This thesis focuses on improving the methods of managing powertrain attributes and the interactions between them. We are concentrating on the particular attributes of Shift Quality, Performance Feel, Driveability, and Trailer Towing. Engineering work to achieve specific attributes is currently handled attribute by attribute and the system is brought together later. This lack of a more holistic view results in a large amount of engineering rework as attributes are balanced. Reducing or eliminating this rework is the goal. A Design Structure Matrix (DSM) was used to document interactions between the powertrain attributes, sub-attributes and design parameters. Research on various reporting formats was done to determine the best method to communicate the interactions. DSM experts were interviewed about the benefits and pitfalls of using a DSM for reference. Several surveys were done to determine engineering's familiarity with various methods of displaying system interactions and their preferences for reporting the interactions. We also compared the interactions to existing CAE capability to determine the current state of attributes management. The DSM showed numerous interactions between powertrain attributes, other vehicle attributes and design parameters. The analysis of existing CAE tools showed a significant percentage of interactions are not currently being modeled. The responses to survey questions on output methods indicated that a DSM, while being an excellent tool for capturing the interactions, might not be the best tool for displaying the interactions to engineers. The surveys revealed that(cont.) engineers are looking for more information than a DSM or any systems interactions model contain, such as probability that an interaction exists, expected direction and levels of the interaction, and quick and simple methods for better understanding of these potential interactions. This desired level of detail highlights the need to share Lessons Learned, develop a corporate knowledge base and develop best practices. A review of the organizational structure and engineering focus indicated that increased focus is needed on powertrain attributes to better match customer expectations. Additionally, organizational structure changes are recommended to increase visibility of powertrain attributes.by Daniel J. Rinkevich [and] Frederick P. Samson.S.M

Integrated durability analysis of a vehicle through virtual simulation.

The intent of this research is to create a high fidelity multibody dynamics model of a compact Sport Utility Vehicle (SUV) using CATIA, ADAMS and NASTRAN software suites. These software packages together are used to conduct virtual proving ground simulations. An MTS 329 series Road Test Simulator (RTS), which uses servo-hydraulic actuators to replicate vehicle proving ground is used to correlate results. The overall objective is to be able to predict component failure earlier in the design process, and to reduce the amount of time spent conducting physical durability tests. This thesis builds on research currently being conducted by many auto manufacturers in the area of virtual road test simulation. The development of a complete durability model is very complex, and involves many steps in simulating physical phenomena. This research focuses primarily on model creation techniques that are used to build a virtual multibody dynamics model, with an emphasis being placed on the construction, implementation and background theory of flexible bodies. (Abstract shortened by UMI.)Dept. of Mechanical, Automotive, and Materials Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2003 .W66. Source: Masters Abstracts International, Volume: 44-01, page: 0428. Thesis (M.A.Sc.)--University of Windsor (Canada), 2003

Analysis of the roll properties of a tubular-type torsion beam suspension

Abstract: Tubular-type torsion beam rear-suspension systems are widely used in small passenger cars owing to their compactness, light weight, and cost efficiency. It is already known that the roll behaviour of a torsion beam suspension system can be approximated to that of a semitrailing arm suspension system. By this kinematic assumption, analytical equations to obtain the roll centre height, roll steer, and roll camber have already been developed in terms of geometry points. Therefore, this paper proposes an analytical method to calculate the torsional stiffness of a tubular beam from its cross-section area based on the assumption that a tubular beam is a series connection of finite lengths with a constant cross-section. In addition, a potential energy method is proposed to calculate the roll stiffness of a tubular torsion beam suspension system based on considering the bushing stiffness and torsional stiffness of the tubular beam without the use of any commercial computer-aided engineering (CAE) software. The torsional stiffness and roll stiffness predicted using the proposed method showed errors of about 4 per cent and 3.3 per cent respectively, when compared with results from commercial CAE software

A Virtual Shaker Table for Predicting Loads in Automotive Powertrain Mounts

In the automotive industry, multi-axis shaker tables are often used to study the damage caused by motion-induced inertia loads to components such as engine mounts or fuel tank strips. To assess the component durability characteristics using this approach, prototype parts must be built and a test rig must be installed. This process is both time and budget consuming, so there is an incentive to reduce the number of physical shaking tests. To that end, this thesis introduces a set of software tools that are capable of conducting virtual shaking simulations with quality output results, i.e., a virtual multi-axial shaker table (VMAST). By refining and reproducing vehicle body acceleration signals collected from the proving grounds, the VMAST is able to replay the body motion of a vehicle. The reproduced motion (drive file) can then be used to drive the virtual dynamic shaking. With the additional consideration of vehicle body local flexibility, the flexible motion can be added to the rigid body motion to improve the simulation accuracy. The dynamic shaking simulation can be done natively in MATLAB, or the drive files derived from MATLAB can be used by other commercial software, such as Altair MotionView. The virtual load data acquisition of the engine bushing mount is implemented during the simulation to predict the fatigue index, which can be referenced in the design procedure. This VMAST provides the automotive engineer with a cost effective tool for analysis, and optimizes the testing process, allowing rapid design iteration

Dynamic Substructuring for Evaluating Vibro-acoustic Performance

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 기계항공공학부, 2020. 8. 강연준.Generally, a mechanical system consists of various substructures that cause noise and vibration problems. This thesis proposes a dynamic substructuring method for the estimation of the dynamic characteristics of a coupled mechanical system based on substructure characteristics. The first phase of this thesis presents a method for the estimation of rotational stiffness at the coupled points of an assembled system based on a dynamic substructuring method. Conventional test-based rotational stiffness evaluation methods are sensitive to measurement errors and require a specialized jig for testing. In contrast, given that the proposed method uses the natural frequency shift phenomenon that results from the addition of mass, the measurement error is relatively small, and the accuracy is improved by excluding the interference of other modes. In addition, the proposed method solves the problem due to the complexity of the conventional method by changing the fixed condition of the system using frequency response function (FRF)-based substructuring (FBS) modeling; thus, it does not require a specialized jig for fixing parts. In this manuscript, the concepts of trial mass, virtual mass, and virtual spring are introduced to systematically explain the proposed method and its application based on frequency shifts. The results of the experiments conducted on a vehicle shock absorber verify the utility of the proposed method. In the second phase, a novel transfer path analysis (TPA) method based on a dynamic substructuring model is proposed. With the dynamic substructuring model, the FRF information of a base system can be used to evaluate the stiffness addition effect at the measurement points instead of adding the actual stiffness. In the proposed method, a spring with an infinite stiffness is virtually added to a specific transfer path among various possible paths, such that the specific path is removed. Hence, the virtual spring significantly reduces the contribution of the specific path. This method is more implementable and applicable than existing TPA methods (i.e., conventional TPA and operational TPA), as it does require part removal or the correlation information between the signals. To verify the feasibility of the FBS-based TPA method, it was applied to a significant road noise phenomenon. The test results confirm that the proposed method can be applied to the TPA of suspension linkages and vehicle bodies. In the final phase of this thesis, an improved dynamic substructuring model is presented based on the estimated FRF information at a coupling point between substructures. An assembled system generally consists of two or more such substructures, which are typically connected by a bolt. To ensure an accurate estimation of the dynamic characteristics of the assembled system, an accurate measurement of the joint properties is required. However, in most practical cases, physical constraints prevent such measurements at actual coupling points. Accordingly, this study proposes a method that uses generalized coupling properties to estimate the dynamic characteristics of a new coupling system based on the characteristics of the original substructure. In this process, the concept of virtual point transformation was used to estimate accurate FRFs at the coupling points of the assembled system based on convenient measurements. Thereafter, the proposed method was validated using a hard-mount vehicle suspension in a test jig and on an actual vehicle body for estimating the vibration characteristics of the assembled system. This research contributes towards the accurate estimation of the dynamic properties of bolt-assembled systems in several practical applications.일반적으로 기계시스템은 다양한 하위 부분구조물로 구성되며, 이들은 많은 소음 및 진동 문제를 야기한다. 본 논문은 이러한 하위 부분구조물의 동특성 정보만을 사용하여 전체 대상 시스템의 동적 특성을 추정하기 위한 동특성 합성기법을 다루고 있다. 먼저, 본 논문의 첫 장에서는, 동특성 합성기법을 활용한 결합 시스템의 회전 강성 추정 기법을 제시하였다. 기존 시험기반의 회전 강성 평가법들은 측정 오류에 민감 할 뿐 아니라, 측정을 위한 별도의 고정용 지그가 필요하다. 그러나, 본 연구에서 제시된 방법은 시스템에 부가되는 질량에 의한 고유 주파수 편이 현상을 사용하기 때문에 기존 방법에 비해 측정오차가 상대적으로 작고, 다른 모드의 간섭을 배제함으로써 추정 정확도의 향상을 기대할 수 있다. 또한, 본 기법은 주파수 응답함수 기반 합성 모델을 사용하여 실제 고정 지그를 사용하는 대신, 고정 경계조건을 수식적으로 대체함으로써 기존 방법의 복잡성을 해결하였다. 이 과정에서 시험 질량, 가상 질량 및 가상 스프링의 개념이 도입되었으며, 실제 차량의 충격 흡수장치를 이용하여 모델의 검증을 수행하였다. 다음으로, 본 논문의 두 번째 장에서는, 동특성 합성 모델을 이용한 새로운 전달 경로 분석 기법을 제시하였다. 본 연구에서는 대상 시스템의 실제 전달경로를 제거하는 대신, 무한대의 강성을 갖는 가상의 스프링을 주파수 응답 함수의 형태로 반영함으로써, 특정 전달경로의 제거 효과를 구현하였다. 본 기법은 기존의 전달경로 분석법에 비하여 실험적으로 구현이 쉬우며, 측정에 소요되는 작업량과 계산량 또한 획기적으로 줄일 수 있다. 해당 기법은 차량 현가계의 특정 진동 전달 현상을 이용하여 실험적으로 유효성이 검증되었다. 본 논문의 마지막 장에서는, 동특성 합성 모델의 정확도 개선을 위한 연구가 수행되었다. 일반적으로 결합시스템은 두 개 이상의 결합물이 볼트를 이용하여 결합되며, 결합 시스템의 동특성 예측을 위해서는 결합부의 정확한 동특성이 요구된다. 하지만 대부분의 경우, 물리적 공간의 제약으로 인하여 실제 결합 지점에서의 측정이 불가능하기 때문에, 가상 지점의 개념을 도입하여 결합지점에서의 주파수 응답함수를 추정하였다. 해당 방법 역시, 실제 차량과 서스펜션 시험 지그를 이용하여 검증되었다. 본 연구는 많은 실제 응용 분야에서 정확한 시스템의 동특성 추정에 기여하고 있다.CHAPTER 1. GENERAL INTRODUCTION 1 1.1 Research background and motivation of the work 1 1.2 Literature reviews 8 1.3 Overview of the present work 15 1.4 Contributions 17 CHAPTER 2. INTRODUCTION TO DYNAMIC SUBSTRUCTURING 21 2.1 Introduction 21 2.2 Summary 25 CHAPTER 3. VIRTUAL PARAMETERS FOR ESTIMATING ROTATIONAL STIFFNESS 27 3.1 Introduction 27 3.2 Theoretical concepts 34 3.2.1 Concept of trial masses 34 3.2.2 Concept of virtual masses 40 3.2.3 Concept of virtual springs 44 3.3 Experimental validation 47 3.3.1 Validation of trial masses 47 3.3.2 Validation of virtual masses 55 3.3.3 Validation of virtual springs 59 3.4 Summary 64 CHAPTER 4. TRANSFER PATH ANALYSIS USING A VIRTUAL SPRING 69 4.1 Introduction 69 4.2 Conventional TPA 76 4.3 FBS-based TPA 79 4.4 Experimental validation 83 4.4.1 Specific road noise phenomenon 83 4.4.2 Suspension link TPA 89 4.4.3 Body TPA 99 4.5 Summary 104 CHAPTER 5. EXPERIMENTAL METHOD FOR IMPROVED ACCURACY OF DYNAMIC SUBSTRUCTURING MODEL 109 5.1 Introduction 109 5.2 Theoretical concepts 111 5.2.1 Dynamic substructuring model considering generalized coupling properties 111 5.2.2 Virtual point transformation method to improve experimental data 117 5.2.2.1 Virtual point displacement 117 5.2.2.2 Virtual point FRF 125 5.3 Validation of virtual point transformation 128 5.3.1 Target system and system description 128 5.3.2 Validation of virtual point transformation 133 5.3.2.1 Validation of virtual point displacement 133 5.3.2.2 Validation of virtual point FRF 139 5.3.3 Dynamic substructuring with virtual point transformation 143 5.4 Summary 152 CHAPTER 6. CONCLUSIONS AND RECOMMENDATIONS 155 6.1 Conclusions 155 6.2 Recommendations 159 APPENDIX 163 REFERENCES 167 국 문 초 록 177Docto

Health Monitoring of LAV Planet Gear Bushings using Signature Analysis Techniques

The Center for Integrated Manufacturing Studies (CIMS) is studying the improvement of military Light Armored Vehicles (LAVs) for the United States Department of Defense. A focus of this study is the Marine Corps LAVs that are experiencing failures in the planetary assembly which serves as the vehicle\u27s final drive system. The primary failure source is the bushings that provide the interface between the planet gears and their respective pins. Currently, to detect a bushing failure, vehicle occupants must exit the LAV and place their hand on the wheel hub cover to check for excessive heat. If the hub feels too hot, travel must stop so the planetary assembly can cool down. These overheating wheel hubs can lead to catastrophic failure of the planetary assembly. Therefore, CIMS is working to analyze these bushing failures and develop a method that will allow occupants to detect potential bushing failures from inside the moving vehicle. In the past, the relationship of pin-bushing interface temperature and wear showed that temperature does not indicate bushing failure soon enough for practical implementation. It was the intention of this current wear study to evaluate bushing failures using vibration signatures as part of an effort to develop failure prognostic tools for (future) in-service use. This thesis was conducted as a feasibility assessment study to evaluate bushing failure from a vibration and signal processing standpoint. Accelero meters were used to collect vibration data from the bushings. Collected vibration signatures were analyzed and examined as bushing wear progressed to determine whether or not remaining bushing life could be predicted using vibration signatures. Vibration data was analyzed from an energy standpoint; that is, the band power was calculated for several frequency bands of interest. Band power was plotted versus bushing wear to reveal any potential relationship between the two. Test results showed that a direct, linear relationship exists between bushing wear and band power in the 2000 to 2100 Hz frequency range. The results of this thesis suggest that vibration data can be used to identify the severity bushing wear. Since this investigation was conducted as a feasibility assessment, additional work is required before this wear detection method can be implemented on an actual LAV. It is recommended that similar bushing wear-vibration studies be conducted where bushings are tested on the Mustang dynamometer (at CIMS) and then on an actual LAV

Structure-thermal coupling in viscoelastic material in rubber bushing of vehicle system

The objective of this research is to utilize the frequency-dependent viscoelastic material model and characterize the dynamic response of rubber bushing under external excitation. Furthermore, with appropriate modeling, two heat generation mechanisms of rubber bushing are explored and their thermal fields are investigated. Due to the nonlinear force-deflection relationship of the viscoelastic material, finding satisfactory mechanical properties of rubber components still poses a great challenge. However, industry nowadays is in urgent demand for precise finite element analysis (FEA) modeling of rubber components. For example, a proper constitutive relationship of rubber components is critical to providing a reliable and trustable simulation of vehicle suspension systems. As for current FEA commercial software, the frequency-dependent modulus of viscoelastic material hasn\u27t been presented well and they have failed to provide satisfactory results. Therefore, two approaches, FEA and the multi-body dynamic analysis have been selected together to give a more comprehensive and credible prediction of suspension system\u27s performance in different working conditions. The FEA approach evaluated the stability of rubber bushing in view of the dynamic response and temperature distribution under high frequency excitation. With these results, the life prediction of rubber bushing becomes more feasible. The multi-body dynamic analysis explores the structure instability of rubber bushing when exposed to extremely high frequency and estimates the energy dissipation in the rubber core.^ The key innovations of this paper can be classified into four aspects. The first one is the application of multi-body dynamics in the dynamic analysis of rubber bushing. Based on experimental modal analysis, the sandwich cylindrical rubber bushing is treated as multi-body. With the multi-body model, the transfer function of the rubber bushing is calculated in order to estimate the dynamic response. The second innovation comes from the development of the FORTRAN program to solve the system transfer function of the structure made of viscoelastic material. Since the geometry and boundary conditions are amenable in FEA compared with the experimental modal testing, this approach is not just applicable in rubber bushing dynamic analysis, but also useful in dynamic analysis of different rubber components. The third innovative contribution of this research is connecting the multi-body analysis with continuum mechanics to evaluate the mechanical properties of rubber bushing. The last innovation is the structure-thermal coupling of rubber bushing to predict its temperature distribution based on the heat source calculated from the FEA simulation. The finite volume method (FVM) is applied using MATLAB in the simulation of temperature distribution. In this research, the classical standard linear model is applied in the FEA program to characterize the variation of viscoelastic material in the frequency domain. The three parameters of this model have been identified with the batch data measurement using dynamic mechanical analysis equipment (DMA). Specially, two heat generation mechanisms are explored to emphasize the friction-induced hysteresis damping except for the commonly discussed viscous damping. As complementation of FORTRAN program simulation in the frequency domain, the multi-physics commercial software COMSOL is employed to estimate the dynamic response of rubber bushing and temperature distribution in the time domain. To verify the results of FEA and multi-body dynamic approach in the dynamic and thermal analysis of rubber bushing, dynamic tests have been carried out using torsion and tensile testing machines. The experimental temperature distribution is in good agreement with the simulation results, which indicated the feasibility of the FEA method.^ However, due to the limited experience and complicated constitutive relationship of the viscoelastic material, the standard linear viscoelastic model is chosen to simulate the heat dissipation mechanism of rubber core. The high-frequency or high-temperature dynamic testing are almost impossible because of the experiment equipments\u27 range of service. As the first step of predicting the dissipation energy density and temperature distribution of rubber components, the initial explorations are significant and provide a proper guidance for further predictions about life expectation