Abstract: In an assembly including components clamped together and in which one or both of the components is subject to a relatively high and variable tensile stress, fretting due to vibration at abutting surfaces of the components can start cracks in the surfaces which is then accentuated in the stressed surface.FIG. 1 of the specification shows a fan turbine rotor disc 4 clamped on a shaft 2 by nut 12 and interposed between confronting surfaces 14 and 16 on the disc and an adjacent bearing is a stress-reducing collar 6 which is slotted at 18 to define struts 20 extending between the surfaces. The struts 20 transmit the clamping load while allowing torsional flexibility to reduce the shear stress and hence fretting between contacting surfaces.In an alternative embodiment the surfaces themselves may be slotted which gives the added advantage that the tensile stress in the surfaces can be reduced or eliminated.