Annika Stensson

Nonlinear dynamics of parts in engineering systems

By definition, chaotic vibrations arise from nonlinear deterministic physical systems or non-random differential or difference equations. In numerous engineering systems there exist nonlinearities ...

THE NONLINEAR BEHAVIOUR OF A MACPHERSON STRUT WHEEL SUSPENSION.

SUMMARY Three nonlinear models of a MacPherson strut wheel suspension have been studied. The nonlinearities considered are due to the nonlinear geometrical effects in the mechanism, the amplitude limitation due to the bumpstop, the progressive stiffness of the bumpstop and the different damping coefficients for the shock absorber in bump and rebound. The models have been derived according to physical parameter values of. the MacPherson strut wheel suspension of the car SAAB 9.000. The most suitable model was further studied with special attention to nonlinear phenomena. For harmonic forcing the system had phenomena such as multiple solutions and subharmonics. For some parameter values the solution was very sensitive to changes in the integration tolerances in the numerical integration routine. No chaotic steady state solutions were found for the parameter values studied.

Simulation and Visualisation of the Dynamic Behaviour of an Overhead Power System with Contact Breaking

SUMMARY For high speed rail traffic it is necessary to design overhead power systems which minimize the contact loss between pantograph head and contact wire. To predict how different design solutions will behave it is favourable to model and simulate the dynamic behaviour. In this paper a model of an overhead power system is specified and used in simulation. The model is suitable for simulation with contact loss since it includes specifications of impact conditions between pantograph head and contact wire. Two sets of equations of motion are specified, one for the contact case and one for the non-contact case. The model also includes lateral movement of the wire due to the zigzag span and friction between the pantograph head and the contact wire. It is shown how to make animations of the system behaviour using a MCAE-system. The animations are made using a geometrical model of the system together with results from numerical simulations. Through the examples provided, use of the mathematical model and the...

Consequences of Nonlinear Characteristics of a Secondary Suspension in a Three-Piece Freight Car Bogie

Mechanical systems with nonlinear characteristics can show a complex dynamic behavior that should be taken into account when analysing dynamic performance and reliability. The dynamic behavior of the main suspension in a three-piece freight car bogie with constant friction damping is considered in this work. The aim is to investigate the vertical behavior of a specific suspension design due to different driving conditions, weather and wear of the friction wedges. A variation in weather and wear is represented by different friction configurations in the model of the suspension. Models of different levels of detail that are based on experimental data on existing designs are developed. It is found that the suspension performance is very sensitive to variations of the friction configuration and this indicates a possible presence of nonlinear dynamic phenomena at in service like conditions.

Nonlinear dynamic behaviour of coupled suspension systems

A two degrees of freedom model of two coupled suspension systems characterised by piecewise linear stiffness has been studied. The system, representing a pantograph current collector head, is shown to be sensitive to changes in excitation and system parameters, possessing chaotic, periodic and quasiperiodic behaviour. The coupled system has a more irregular behaviour with larger motions than the uncoupled suspension system, indicating that the response from the uncoupled suspension system cannot be used as a worst case measure. Since small changes in system parameters and excitation affect the results drastically then wear and mounting as well as actual operating conditions are crucial factors for the system behaviour.

Dynamic Behaviour of Ore Wagons in Curves at Malmbanan

SUMMARY The transportation of ore can be made more cost efficient by use of bigger and heavier trains. An increase in axle load is thereby wanted. The fleet of ore wagons of today at Malmbanan/Ofotbanan in northern Sweden and Norway has to be updated. It is of interest to find out if it is possible to allow a higher axle load on the track with new wagons To be able to understand and predict the effects on track wear depending on what type of vehicle that is in use, the contact forces between wheels and rails have to be determined. A computer aided analysis has been made of the dynamic behaviour of three test vehicles equipped with different types of three-piece bogies running at Malmbanan. The vehicles are modelled and their interaction with the track is analysed using the multibody simulation package GENSYS The simulations show that, even if the axle load is increased from 25 tons to 30 tons and the velocity is increased from 50 km/h to 60 km/h, it is possible to reduce lateral track forces and wear in c...

A Relational Database for General Mechanical Systems

This paper provides a specification of a relational database structure for mechanical systems. Through the example provided, a robot gripping device, it is demonstrated how the initial development of the database structure has successfully led to an implementation in a practical software environment. The database is accessible to multiple engineering application programs and supports a flexible environment for the continuing development of new applications.

State-of-the-Art of CAE for Mechatronic Systems and Industry Requirements

Computer aided engineering support is important in order to increase the efficiency in the product development process without sacrificing product quality. For mechatronic systems, different aspects such as system dynamics, actuators, sensors, control algorithms and interacting systems must be considered and this makes the computer environment complex. The aim of this work is to present the state-of-the-art of computer aided engineering support for development of mechatronic products together with industry demands on future capabilities.