Abstract
In order to elucidate the characteristics of residual stress and plastic strain produced by the dissimilar friction welding operation, detailed FEM modelling was carried out. The obtained main results are as follows :
(1) During numerical modelling of residual stress and plastic strain formation in dissimilar joints, the distribution of δz (axial component) in the radial direction produced by uniform cooling from 800°C, in material adjacent to the bondline in both substrates, provides an effective means for evaluating the accuracy of the computational procedure in dissimilar materials welds.
(2) Heat transfer into a narrow zone, z=±20 mm on either side of the bondline promotes residual stress formation. The peak temperature occurs in the AISI304L substrate.
(3) Adjacent to the bondline, σr (radial component) is tensile in the higher thermal expansion substrate (AISI304L), and is compressive in the substrate (titanium) with the lowest thermal expansion value. σz is tensile in the central region of the component (where the stiffness is large) and is compressive at the periphery of the component.
(4) The σz distribution in the axial direction, in material far from the bondline, indicates that σz is compressive in the central region of the component and is tensile at the component periphery. Specially, σz is tensile in titanium substrate, except in regions extremely close to the bondline at the periphery of the component.
(5) Considerable plastic strain is produced perpendicular to the bondline and in the radial direction. Limited plastic strain occurs in the circumferential direction.
(6) Severe plastic strain is produced in titanium substrate close to the bondline. This region in titanium close to the bondline has a hardness 1.5 times higher than in the base metal.
