Subject: CHASSIS AND BODY DESIGN AND MANUFACTURING (A.A. 2021/2022)
Unit chassis and body design and manufacturing
To be chosen by the student (lesson)
in attesa di attivazione da parte del docente
The outcomes of the course are to provide the advanced knowledge, the methods and the tools useful for the correct design and verification of the chassis components. The students will learn how to tackle the design of a motorbike frame by means of both analytical and numerical FEA tools. A special focus will be put on joining methods suitable for lightweight structures (adhesives, bolts, welds). The design of some key components, such as suspension elements, will be examined in depth. At the end of the course, the students will be able to select the most appropriate structural solutions based on the product mission, taking into account both the performance targets (e.g. stiffness, weight) and the expected failure modes the product must be designed against (e.g. fatigue, wear), in the framework of the requirements set by the relevant International Standards.
Basic skills acquired through the following teachings may be regarded as prerequisites for a correct fruition of the present course: Mechanics of Solids, Machine Mechanics, Machine Design.
Statically indeterminate structures: force method and displacement method. Strain energy methods. Rotating-node and translating-node frames.
Screws: static and fatigue dimensioning and assessment. Calculation methods according to Eurocode 3 and VDI 2230. Axial preload and tightening torque. Determination of the coefficients of friction according to ISO 16047. Friction coefficients requirements according to the automotive field normative. How to account for data scatter in dimensioning threaded joints. Load introduction factor. Prying load. Residual shank torsion. Self loosening and self-relaxation issues.
Static and fatigue dimensioning and assessment.Failure criteria. Calculation method according to Eurocode 3 (steel) and Eurocode 9 (aluminium).
ADHESIVELY BONDED JOINTS
Static and fatigue dimensioning and assessment. Single-lap joints: Volkersen and Goland&Reissner theories. Cylindrical joints: dimensioning according to the Loctite method. Hybrid joints: interference fit plus adhesive.
FEA laboratory with commercial softwares
Introduction and solution of linear static problems
Numerical modeling of threaded joints, 1d and 3d approaches.
Numerical modeling of welding joints.
Numerical modeling of adhesively bonded joints.
Solution of nonlinear problems (large displacements, nonlinear materials, contact).
EXPERIMENTAL STRESS ANALYSIS
Strain gauges: materials, measuring circuits, data acquisition. The gage factor. Single grid strain gauges and rosettes. Determining residual stresses by the hole-drilling strain gauge method.
TUTORIALS AND CASE STUDIES
The course content will be entirely covered by the lectures. Lectures are supported by many practical exercises, aimed at guiding the students towards the solution of practical problems, based on the tools acquired during the theoretical lectures.
The examination consists of a written test, made up of two exercises dealing with the topics of the course. The test lasts three hours, every kind of printed support is allowed.
Students shall acquire the ability to identify the key elements of the chassis which affect the fulfillment of the required structural performance.
They shall be able to properly model the problem and to validate the results of calculations.
A. M. Wahl, Mechanical Springs, 2nd Ed. Mc Graw Hill Book Company.
A. Freddi, G. Olmi, L. Cristofolini, Experimental Stress Analysis for Materials and Structures: Stress Analysis Models for Developing Design Methodologies, Springer.
B. J. Mac Donald, Practical Stress Analysis with Finite Elements (2nd Edition), Ed. Glasnevin.
D. G. Pavlou, Essentials of the Finite Element Method: For Mechanical and Structural Engineers, 2015 Ed. Elsevier Academic Press.
S. Timoshenko, J. N. Goodier, Theory of Elasticity, 1951 Ed. McGraw-Hill.