Survey of CAx

Hardware models

- Clay model for styling

- Wood model for first functional tests

- Physical Mock-Ups for functional optimization (seat box, ergonomics, ...)

- Rapid prototyping for evaluation

- Test bench configurations

Virtual models

- Functional structure diagrams

- Geometry models (2D-/ 3D-CAD, DMU)

- Simulation Models (FEM, CFD, MBS, ...)

- Functional simulation models (test of control systems)

- Production simulation (CNC, ...)

- Data structure models (PDM) - Cost calculation models

• A model is a simplified reproduction of an existing or an imaginary system in a different conceptual or representational system (within specified boundaries to enable a specified investigation).

• Models are used to find solutions for problems, which would be not possible or to complex with the original system.

• Models reduce the real conditions to focus the essential aspects of the particular investigation.

• Models simplify and reduce complex systems.

• Models are the basis for the reproduction of product characteristics in virtual development and simulation software tools (CAD, FEM, DMU, PDM, etc.).

Trends:

• Increasing product variety and product complexity

• Integration of different technical disciplines into the development process

• Manifold data formats and structures with interdisciplinary relationships - Disposition of project data on several (global) locations

- Physical models are based on physical laws or axioms, which allow a mathematical description of the considered process(es). The resulting equations usually need to be solved by numerical algorithms.

Advantages: physical meaning of the system parameters, physical insight into the nature of the considered process.

- Phenomenological (or empirical) models are based on mapped approximations of measured or observed phenomena without direct application of mathematical description of physical laws.

Advantage: High computational efficiency.

Simulation (calculation):

• Advanced pre-investigations

• Studies of alternative variants

• Reproducibility of results

• Derivation of difficultly measurable quantities

Measurement (testing)

• Results contain all the influences

• Discovery of remaining weak points

• Subjective fine tuning

• Trouble shooting

• Production release competence

- The material vehicle system (vehicle, -component, media) can be understood as connected group of different continuous bodies („continua“).

- The characteristics of these continua are density, stiffness and viscosity.

- Each of these continua is an infinite-dimensional quantity of material points, which must be discretized into a finite- dimensional structure for computer friendly processing.

- This discretisation process is called modelling or model building.

- The way, how to perform the discretization characterizes the respective CAE method.

MBS: Separation of the locally distributed parameters into discrete parameters: mass, inertia, stiffness, damping etc. „physical discretisation“

FEM: Separation of the continuum into finite, simple areas or volumes: Finite elements, connected at defined nodes „mathematical discretisation “