Evaluating Designed Gap Closure Effect on Joint Preload

The method presented utilizes the analytical design model and matrix algebra to determine the load required to close a design gap. By performing a linear analysis in MSC® Nastran, relative displacements at fastener contact points due to unit loading are collected. The stiffness equation, F = K x is used in matrix form to determine gap closure force. The effect of this force on preload should be considered in torque specifications.

The method prevents overestimation of preload if closure force is not considered and underestimation if only the stiffness equation is used independently.