Supakit Rooppakhun
Introduction to Automotive Structure The main purpose is to: Support all the major components and sub assemblies making up the complete vehicle Carry the passengers and/or payload in a safe and comfortable manner
The structural requirements of any vehicle structure can be summarized as follows: The structure must be sufficiently stiff to react the static loads and dynamic loads without excessive deformation. The structure must be sufficiently strong to withstand many cycles of the applied loading without suffering from fatigue or other forms of material failure. The structure should deform in such a manner under impact load conditions so as the minimize the risk of injury to the occupants and other road users
A simplified approach to conceptual design The foundations of the simplified approach are the principles of statics and strength-of-materials (the core of basic engineering fundamentals) The Simple Structure Surface (SSS) method is offered as a mean of organizing the process for rationalizing the basic vehicle body structure load paths. (Dr. Janusz Pawlowski, 1969)
The initial design begins with sketches, moving then to full-size tape drawings and then to threedimensional clay model. Packaging mean the determination of the space require for the major components. (such as the engine, transmission, suspension, steering system, radiator, fuel tank, and not least the space for passenger, luggage or payload)
The Simple Structure Surface (SSS) method A methods that is used at the concept stage or when there are fundamental changes to the structure. To model or represent the structure as a number of plane surfaces. Structural surfaces are rigid in their plane but flexible with respect to forces normal to it
The Simple Structure Surface (SSS) method Each plane surface SSS must be held in equilibrium by a series of forces. (forces which created by the weight of components attached to them) Is useful for determining that there is continuity for load paths and subsequently determining the integrity of the structure.
A tool to help: i) qualitatively filter design alternatives during the conceptual stage ii) guide the course of FEA iterations. Combination of these forms a foundation for the later design phase.
Expectation and limitation of SSS method Enables the engineer to know the type of loading condition applies to each of the main structural. (bending, shear, tension or compression loads) Enables nominal magnitudes of the loads to be determined based static conditions and amplified by dynamic factors if these are known.
Expectation and limitation of SSS method To ensure continuity for the load path through the structure is achieved. Theoretically/ideally size of the components can be determined.
Limitations of the SSS method Cannot be used to solve redundant structures Does not enable stiffness values to be determined
The Concept design stage of vehicle body It is critical that functional requirements precede the development of detailed design and packaging. It is possible to generate design data faster than before. The concept design state with the integration of computer aided engineering (CAE) processes has the capability in effect to lay the track
The Concept design stage of vehicle body The SSS method can provide a tool for rationalizing structural concepts prior to and during the application of CAE tools for load conditions. Begin with a qualitative free body diagram (FBD) of the fundamental loads acting on the structure. (SFD, BMD for beam members and shear flow for panels)
The example of an innovation (courtesy of Automotive Design Engineering)