Why bending stiffness and torsional stiffness of the interface rings should be same in a marman clamp band system
There are various ways to formulate stiffness, but we can skip that and go straight to the explanation.
Lets define up to be in an axial direction. We apply a torsional moment to all radial cross sections, for example as an upwards force acting on the outer lower corner, balanced by a pressure on the upper edge. This leads to a small and equal rotation of all these cross sections.
The upmost part of the cross sections move inwards. The lower parts move outwards.
Now lets slice a tangential, curved plane, cut at any radius R you like. All parts are 2piR horizontally. The upper part used to be on a larger radius. The upper part of our ring has just become shorter than it was. The lower part has just become longer than it was. The centre though has stayed on radius R and is just as long as it were. Its a little sheared though.
Sounds familiar? This is the same strain deformation as in bending.
I would not call this torsion, my own mother language has more precise terms. Perhaps someone with better language knowledge could come up with the right term? Wringing?
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