Study of steering effects. Virtual testing of front suspension of heavy trucks.

The truck suspension works today in many different environments. Demands on good handling are high and need to be fulfilled in all possible situations. Good handling needs good control on steering effects. These effects can both be unwanted like brake and bump steering or wanted like understeering. Methods used at Volvo have changed by time from simple geometry sketches and knowledge from test-driving studies to analysis on non-linear FE-models. The department for front suspension and steering at Volvo 3P has developed a non-linear FE model for virtual testing of the front suspension and steering. Steering effects considered in this report are bump, brake and roll steering, with the main emphasis on the last mentioned that has not been previously modeled. The aim of this thesis is to enhance knowledge of steering effects phenomena at Volvo 3P through in-dept studies of output from a complemented and improved modeling of the front suspension steering effects, and to map parameters influence on induced steer angle due to bump, brake and roll load cases. Our approach has been to develop and enhance the load cases of the considered steering effects. The load case representing roll has been broken down into separate parts in order to make the analysis easier. The in-dept analysis of the load cases then gave us a foundation to choose the parameters of the front suspension to be included in the parameter study. The parameter study was then executed with the help of several UNIX, Python and Matlab scripts. The outcome of the steering effects study showed some not well known phenomena, such as twist of the axle beam. The result from the parameter study confirmed the result from the study of steering effects and gave a good picture of the influence of parameter changes. Our conclusion is that modeling of load cases is crucial to get a trustworthy output and that an advanced FE model such as the present is necessary.