386 S. Richardson et al. FaCTs can also be used as a pass/fail indicator as part of a qualification testing system where vibration data, or any other type of engineering data, is acquired from the machine or test article. Any type of engineering data can be added as components to a shape vector, and consequently can be used in an SDI calculation as part of FaCTs. 35.9 Conclusion The purpose of this paper was to show that ODS data taken from the bearing blocks on a rotating machine can be postprocessed to detect and identify various unbalance conditions of the machine. The idea behind this approach is to correlate currently acquired data with data that has been previously archived in a data base, and which has been associated with particular unbalance conditions. We applied two different measures of shape correlation to the ODS data, MAC and SDI. Both measures indicate the likeness of a pair of shapes by giving values between 0 and 1. A value of 1 means that the shapes are the same, and a value less than 1 means that they are different. Both measures could be referred to as correlation coefficients. MAC indicates whether or not two shapes are co-linear, lying together on the same straight line. SDI measures the true differencebetween two shapes. When both measures were applied to the bearing block ODS data, the SDI bar charts showed that the shape difference was stronger than shape co-linearity for discriminating between the unbalance cases. However, even SDI didn’t provide a clear distinction between all cases. Therefore, it was also shown that the sensitivity of SDI can be increased by inputting two modified shapes to the SDI algorithm which are derived from the original shapes. By increasing its sensitivity, SDI was able to clearly discriminate between all of the unbalance conditions and the balanced condition of the rotating machine. References 1. Ganeriwala, S.N., Schwarz, B., Richardson, M.: Using operating deflection shapes to detect unbalance in rotating equipment. In: IMAC XXVII, Orlando, February 2009 2. Richardson, S., Tyler, J., McHargue, P., Richardson, M.: A new measure of shape difference. In: IMAC XXXII, 3–6 February 2014 3. Allemang, R.J., Brown, D.L.: A correlation coefficient for modal vector analysis. In: Proceedings of the International Modal Analysis Conference, 1982 4. Allemang, R.J.: The modal assurance criterion (MAC): twenty years of use and abuse. In: Proceedings of the International Modal Analysis Conference, 2002 5. Richardson, M.: Is it a mode shape or an operating deflection shape? Sound Vibration magazine, March 1997
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