Strand7: Web notes: Shrink fit

Shrink-fit (or press-fit) problems

An analysis is required to evaluate the deformations, interfacial stresses and hoop stresses of two thick walled cylinders shrink-fitted onto each other using an interference fit of 0.1 mm. The interference fit is the initial differences in diameters between the jacket (outer cylinder) and the tube (inner cylinder) at the interface.

In shrink-fit (or press-fit) applications the inside diameter of the jacket is slightly smaller than the outside diameter of the tube. The plate elements modelling this must therefore overlap each other by an amount equal to the interference. In Strand7, the two surfaces are brought together by using Shrink Links. These links can be created manually or by extruding nodes in any user coordinate system. The next picture shows the relevant dialogue boxes.

Shrink-fit or press-fit problems can be modelled using either the four node or eight node quadrilateral plate element and set to either a 2D plane stress or 2D plane strain analysis. Shrink elements could also be used with full 3-dimensional meshes. To check the integrity of the results (and hence the modelling technique), it is best to view the deformed plots using an absolute displacement scale of 1. At this scale there should be no overlapping of the plates. At a displacement scale of 10 (say) there should be a uniform clearance around the diameter of the interface.

The following pictures show the initial plate mesh as well as the results in terms of stresses (hoop and radial).

Initial Mesh using two different plate properties.

Displacement scale set to 10%. The uniform displacements distribution as well as the shrink links are clearly shown

Hoop stresses contour plot.

Radial Stresses contour plot.