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INTRODUCTION
Multi-body dynamics can be understood as the study of systems of many bodies whose interactions are modelled by forces and kinematic constraints. In other words, a multi-body system (MBS) can be defined as a collection of bodies acted upon by forces of different origins and interconnected to each other by different types of joints that constraint their motion. The forces applied to the system components may include those resulting from contact-impact, friction, gravity, joint constraints, external applications, the interaction with other systems such as fluids, tires or wheel/rail contact or due to mechanical elements such as springs, dampers, and actuators. Kinematic constraint types may include revolute joints, translational joints, spherical joints and cylindrical joints, among others. The kinematic constraints may also be in the form of prescribed trajectories for given points of the system components or as a driving constraints for a subsystem. The mechanical systems included under the definition of MBS comprise robots, heavy machinery, automobile suspensions and steering systems, machinery tools, railway vehicles, animal bodies or satellites, among others. However, the range of systems that can be represented by MBS models is expanding and new exciting applications are being proposed every day. Traditionally the kinematic and dynamic analyses of multi-body system was under-taken by assuming that the bodies were treated as rigid.
In recent years greater emphasis has been placed on the design of high-speed, lightweight and precision systems. The design and performance analysis of such systems can be greatly enhanced through transient dynamic simulations, provided that all significant effects must be incorporated into the mathematical model. The need for a better design, in addition to the fact that many mechanical and structural systems operate in adverse environments, demanded the inclusion of many factors that have been ignored in the past. Neglecting deformation effects, for example, when these system are analyzed, can lead to a mathematical model that poorly represents the real system. Neglecting the dynamic loads conditions acting on the structural components of the multi-body system can lead to an improper structural verification.
INTRODUCTION
2 MBS software tools allow engineers to model complex systems with a few number of degrees of freedom. The results obtained from analysis of such systems give the load condition histories, in transient and steady stages, acting on the body (components). Instead, the FE software tools allow detailed stress analyses of the components due to a few number of load conditions with thousands of degrees of freedom.
The interaction of software tools for MBS dynamics, as SIMPACK, and software tools for finite elements analysis, can allow the design and optimization of vehicle structures, components and safety systems by the integration in the multi-body system of bodies flexibility and obtaining from the multi-body analysis (MBA) the main load conditions acting on the flexible body.
