Domenico Mundo

Concept Modelling of Vehicle Joints and Beam-Like Structures through Dynamic FE-Based Methods

This paper presents dynamic methodologies able to obtain concept models of automotive beams and joints, which compare favourably with the existing literature methods, in terms of accuracy, easiness of implementation, and computational loads. For the concept beams, the proposed method is based on a dynamic finite element (FE) approach, which estimates the stiffness characteristics of equivalent 1D beam elements using the natural frequencies, computed by a modal analysis of the detailed 3D FE model of the structure. Concept beams are then connected to each other by a concept joint, which is obtained through a dynamic reduction technique that makes use of its vibration normal modes. The joint reduction is improved through the application of a new interface beam-to-joint element, able to interpolate accurately the nodal displacements of the outer contour of the section, to obtain displacements and rotations of the central connection node. The proposed approach is validated through an application case that is typical in vehicle body engineering: the analysis of a structure formed by three spot-welded thin-walled beams, connected by a joint.

Performance Comparison of Real-Time and General-Purpose Operating Systems in Parallel Physical Simulation with High Computational Cost

Real-time simulation is a valuable tool in the design and test of vehicles and vehicle parts, mainly when interfacing with hardware modules working at a given rate, as in hardware-inthe-loop testing. Real-time operating-systems (RTOS) are designed for minimizing the latency of critical operations such as interrupt dispatch, task switch or inter-process communication (IPC). General-purpose operating-systems (GPOS), instead, are designed for maximizing throughput in heavy-load systems. In complex simulations where the amount of work to do in one step is high, achieving real-time depends not only in the latency of the event starting the step, but also on the capacity of the system for computing one step in the available time. While it is demonstrated that RTOS present lower latencies than GPOS, the choice is not clear when maximizing throughput is also critical.

COMBINING FINITE ELEMENT ANALYSIS AND ANALYTICAL MODELLING FOR EFFICIENT SIMULATIONS OF NON-LINEAR GEAR DYNAMICS

Although gears have been used in mechanical industry for a long time and first systematic research activities, aimed at understanding gear meshing, started in the ‘50s, still nowadays a lack of accurate description for several physical phenomena represents a limitation for transmission design. One of the main causes of such limitations is the threedimensional (3D), local and non-linear nature of contact problems. Given the complexity of these problems, a variety of modelling techniques with different levels of fidelity and required computational effort have been set up. Among the available methodologies, analytical modelling, which has been developed for a vast variety of applications from the early days of gear dynamics research, still attracts the interest of researchers thanks to the low computational requirements and to the capability to efficiently describe specific phenomena. Among analytical models, one-dimensional (1D) description aims at studying the torsional gear vibrations around the rotational axes and can be used to simulate either gear whine or gear rattle phenomena. The aim of this paper is to illustrate a numerical approach, based on 3D (Finite Element) FE simulations, to estimate the mass and inertia properties of a 1D gear pair model. The proposed approach is based on pre-strained modal analyses, carried out on the 3D FE model of a pair of meshing gears, from which the variable meshing stiffness and modal mass values in a given system configuration are derived and used to calibrate the equivalent 1D model. An application example of the proposed method is provided by analyzing a pair of identical spur gears, for which the 1D model is created and used to estimate the dynamic TE at different rotation speeds and under constant external load in steady-state conditions.