Fem-studie av rörelser i planet mellan bakaxelbrygga ADA1100 och centralväxelhuslock R780

Sammanfattning: This thesis has been performed at Scania CV AB Technical Centre in Södertälje and its aim has been to study the causes and effects of deformations in the interface between the rear axle housing ADA1100 and the central gear house R780 during operation. Design changes that would increase the sealing capability of the studied interface are also suggested. Finite element (FE) and CAD software have been the primary tools in this study. Finite element (FE) simulations are used in the industry to predict and develop engineering designs. The main motive for FE simulations has traditionally been to identify weak spots in the design, regarding high tensions and large deformations. The FE model is an aggregation of submodels and interface models that represents the rear axle housing, suspension, central gear, central gear housing, wheels, bolts and weldings, and their interactions. The submodels have different material properties and they are connected with contact interface models. Boundary conditions are defined on the bushings in front of the rear axle and on the air bellows behind the rear axle. The different load scenarios are represented by forces either on the wheels, the central gear or on the rear axle housing. The finite element model has been quantitatively verified with rig tests where displacements at points on a rear axle housing have been measured. The model has also been qualitatively verified by observing the interface behaviour of Scania field trucks. The central gear housing, with reinforcing springs on the sides, shows some weaknesses. When the rear axle housing is loaded with both interior and exterior forces it tends to locally open the interface between the rear axle housing and the central gear housing. Conical shaped openings are judged to destroy the interface gasket by extensive micro sliding. By removing the two lower reinforcing springs on the central gear housing and strengthening the central gear housings flange a 50 to 70 percents reduction of the conical openings can be achieved. This design change will most likely minimize the leakage problem observed on the field trucks.