Issue 41

F. Chebat et alii, Frattura ed Integrità Strutturale, 41 (2017) 447-455; DOI: 10.3221/IGF-ESIS.41.56 452 of penetration length is indicated as c . The load on top of the roller is modelled typically as a uniformly distributed load on the longitudinal line of the roller. (a) (b) Figure 2: Geometry of the rollers: PSV4 133 315 (a) PSV4 159 530 (b) . Two geometries have been considered here and the details of the geometrical parameters are reported in Fig. 2a and 2b for the two cases, named in the following as PSV4 133 315 and PSV4 159 530. For sake of brevity the modeling will be shortly described only for the first geometry. Further details are reported in [27]. The analysis of the stress fields in these welded details needed 3D models, because of their variability along the circular path described by the weld root. The two considered geometries reported in Fig. 2 have been modelled by means of 20-node 3D finite elements implemented in the FE code ANSYS. Due to the symmetry of geometry and loading only one quarter of the geometry has been considered. The bearing has been considered of infinite stiffness and all the nodes of the bearing housing have been connected by means of rigid elements (links) to a master node. This special node has been placed on the symmetrical longitudinal axis of the roller in correspondence of the instantaneous rotation centre of the bearing. The rotation about the axis Z (ROT Z ) and the longitudinal displacement ( U Y , see Fig. 1) have been left unconstrained, while all other displacements and rotations of the master node have been constrained. The load has been distributed along the longitudinal line. For each geometry two models were created: the first was mainly oriented to the determination of the point where the maximum principal stress and the maximum value of the strain energy density were located. Due to the complex geometry of the bearing housing in fact the point varies as a function of the geometry. In this case a regular fine mesh has been used with the aim also to determine the SIFs at the weld root. The second model was characterized by a coarse mesh but by an accurate definition of the control volume where the strain energy density should be averaged. As just stated the mesh used in that case was coarse with a regular increasing spacing ratio in the direction of the position of the control volume mainly aimed to a correct positioning of the volume itself in the most critical region. All FE analyses have been carried out by means of 20-node finite elements under linear-elastic hypotheses.