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.