Torsional Vibration Measurement and Analysis: A New Technique

Torsional vibration measurements, while varying in complexity, are probably the least familiar type of vibration measurement. The high output demands imposed on today's engines require a complete understanding of torsional vibration. This understanding is necessary to insure proper function and durability of these engines and their components. The need for an accurate, reliable and durable measurement system that could be used for the evaluation of any engine application is essential. The measurement system has two basic components, an engine mounted transducer and signal conditioning/data reduction equipment. The transducer must be selected before other system components can be identified or developed. A prototype transducer has been evaluated and proven to meet the above criteria. Its performance has been verified with the use of redundant test methods. This instrumentation included proximity probes, linear accelerometers, an angular velocity transducer and optical methods. The linearity response of the transducer was excellent on all the subjected test set-ups. The device responded equally well to either rotating or non-rotating inputs. Eccentric locations of the transducer were shown to have minimal effects on the output response. Temperature compensation must be built into the production transducer and accurate readings can be expected from 25°F (−3.8°C) to 250°F (121°C). The future of this device looks very promising and the range of applications extend from torsional testing and machinery diagnosis to continuous systems monitoring.