TABLE OF CONTENTS The function of the tie wire is to transmit vibratory loads induced in the blades by various stimuli, from one blade to all others that are tied together into a common batch. This tie therefore assists in dissipating the motion and bending stress throughout all those blades that are tied together. The tie wire location is selected to be at the point on the vane where the amplitude of vibratory deflection is a maximum if the blade were free standing. The tie wire dampens the vibration of the individual blades, but does not dampen the batch vibration.
Vibratory forces are present substantially in the wire axial direction, and induce alternating tensile and compressive stresses along the wire. However, because of the torsional vibration modes, there is also developed in the wire a bending component to these stresses. These loads are normally of low magnitude, but possibly of very high and complex frequencies. The tie wire is then subject to various types of stress or loading:
The centrifugal stresses induced in the wire during operation due to its own weight. These forces produce a bending stress in the wire between adjacent blades. Because the wire has centrifugal weight on both sides of the blade vane, the bending stresses induced in the wire can be estimated using the encastre beam theory. Usually, and under normal operation, the magnitude of such stresses is not high, and at normal speed...
