If the joint experinces a compressive external force this has the effect of increasing the
clamp force acting on the joint and decreasing the tension in the bolt. This is illustrated
with the joint diagram shown below. If the compressive external force is great enough then either:
1. The tension in the bolt can be reduced to a low value - if the external load is cyclic then the
bolt could fail due to fatgue (since it is experiencing tension variations under a compressive external force).
Also the bolt is more susceptable to vibrational loosening.
2. The yield limitations of the clamped material may be exceeded since the joint is sustaining a
compressive force in addition to that provided by the bolt's preload. This will result in some permanent
deformation that upon the release of the external force a loss of bolt preload would result.
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