Tyre / soil interaction modelling within a virtual proving ground environment

摘要

Off-road mobility defines the ability of land-based vehicles to accelerate, pullloads and climb gradients. Historically, much of the work completed to relatemobility to vehicle and terrain characteristics has been empirical in nature, andhas therefore been susceptible to errors caused by the inherent variability ofnaturally occurring soils. This thesis addresses the off-road mobility of wheeledvehicles, and in particular the use of a finite element (FE) based approach topredict performance metrics such as rolling resistance, drawbar pull and tractiveefficiency. Tools to predict these measures of performance have a wide rangeof applications, including military, agricultural and leisure vehicles, aircraftoperating from temporary airfields and planetary landing craft.The current study extends the virtual proving ground (VPG) concept, where asingle vehicle model can be subjected to a series of virtual test conditions, toinclude the assessment of off-road mobility. Throughout, modelling has beencarried out using LS-DYNA, a commercially available non-linear dynamicanalysis code. Unlike previous studies using FE techniques to investigatewheel / soil interaction, an Eulerian representation of the soil has beenemployed, which permits a consistent approach to be applied to both purelycohesive and purely frictional soils, as well as those displaying a combination ofcohesive and frictional behaviour. At each stage of the research, the validity ofthe FE-based modelling approach has been assessed using data fromcontrolled experimental testing at Cranfield University’s off-road dynamicsfacility.A key finding of the work completed is that rate sensitivity in moisture containingsoils can significantly affect the accuracy of (empirical, analytical and numerical)model predictions, even at low translational speeds (less than 0.1m/s). Thisfinding highights the adverse impact of simplifications in many previousexperimental and modelling studies, which have assumed that rate effects maybe ignored providing the translational speed of the vehicle is low.