Emission test transducers are located on each ram

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emission test transducers are located on each ram, each connected into one acoustic emission preamplifier. Only one preamplifier is required because only one ram is active at a time during straightening. The amplified signal is fed into the acoustic emission test system for processing. The system consists of (1) a circuit to filter unwanted high and low 263 Acoustic Emission Testing for Process and Condition Monitoring P ART 6. Crack Detection during Straightening of Axles and Shafts F IGURE 40. Block diagram of an acoustic emission system for shaft straightening. Preamplifier Transducers Acoustic emission in Transducer coupling test Alarm out Straightening process Acoustic emission system Transducer coupling test Alarm light Audible alarm Crack alarm out Crack alarm Straightening Axle position Shaft straightening programmable controller Axle holder Anvil Axle Axle holder
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frequency noises, (2) signal processing circuitry to extract acoustic emission time and hit based features and (3) an onboard computer to process the acoustic emission test signals and to separate noise from crack signals with a pattern matching algorithm for intelligent crack detection. The acoustic emission test system is fully coordinated by the shaft straightening controller through input and output signals between the systems. There are two main acoustic emission test processes being coordinated by the shaft straightening controller: a transducer coupling test and a straightening process. Each process is described below. Transducer Coupling Test The transducer coupling test is carried out just before the shaft is straightened. Once a shaft (or axle) is inserted into the straightening fixture, the machine sets up for the straightening process by rotating the axle into position and advancing the ram into place over the shaft to be straightened. When the ram is touching the axle with a slight force, the controller signals to the acoustic emission test system that a transducer coupling test should be carried out. The acoustic emission test system excites the pulser transducer, sending simulated acoustic emission test signals down the shaft. The signals are detected by the ram transducer in contact with the axle and the system alerts the shaft straightening controller that the simulated crack has been detected. This diagnostic step ensures that the entire acoustic emission system is operating properly before beginning a straightening operation. Straightening Process Once the transducer coupling test is successful, the shaft straightening controller turns off the transducer coupling test signal and starts the straightening process, which indicates to the system that a test has started. At this point, the system is processing all acoustic emission activity to detect a crack. The acoustic emission test system contains a crack detection algorithm to distinguish cracking from noises generated by the machine, environment or process. This algorithm eliminates false alarms that reject good product.
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