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Dragging the Bolt Pretension object under Static Structural to Solution and evaluating results gives the amount by which the bolt has to be shrunk in order to generate the specified preload. See below. The value reported by ANSYS (3.093e-3 in) can be checked using 1D elasticity approximation: dL = (F L)/(E A)
Hex Mesh
The disadvantage of the Hex Dominant meshing technique is that it generates poor elements in transition regions between hex and tet elements. A pure hex mesh can be generated by splitting up the model and using the Multizone meshing technique as per below.