Cracks due to material fatigue are very dangerous for rotating machines. Early detection of any crack is therefore essential before permanent rupture and often fatal consequences can occur. The crack influences the vibration behaviour of the shaft by changing its rigidity. Using suitable analysis software, this change can be registered and inspection of the machine organised in good time. In the experiment, the crack is simulated by an asymmetric flange joint. Variable tightening of the flange bolts produces a temporary gaping of the butt joint, which closely approximates to the behaviour of a crack.
The accessory set-up includes two shafts of different lengths: one short and one long. The short shaft simulates a protruding shaft end, and is loaded with the PT 500.14 belt drive. The long shaft is used in conjunction with a retainer bearing from PT 500.10 and an inertia disk from the base unit to investigate the effects of a crack in a shaft on the elastic rotor.
The accessory set-up is mounted on the base plate of the machinery diagnostic base system PT 500. To measure and evaluate the experiment, the computerised vibration analyser PT 500.04 is required. It includes all the necessary sensors, a measurement amplifier and analysis software to record the vibration phenomena.
Learning Objectives / Experiments
- Change in characteristic vibration behaviour (natural
frequency, resonance speed, amplitude and phase
of vibrations) due to a crack - Crack identification from the change in vibration
spectrum - Detection of cracks in rotating shafts at the
protruding shaft end
- Understanding and interpreting frequency spectra - Use of a computerised vibration analyser
In conjunction with a retainer bearing (e.g. from PT 500.10 - elastic shaft accessory set-up) - Detection of cracks in rotating shafts (the elastic
* Vibration behaviour of shaft with radial crack1 * Identification of damage
 Investigation of the vibration behaviour of a cracked shaft  Crack adapter in flange form  Simulation of the crack by opening bolt joints  4 different sized cracks can be simulated  Short shaft to simulate a protruding shaft end  Long shaft to simulate an elastic rotor  PT 500.14 (belt drive) generates required bending torque  Accessory set-up for PT 500 machinery diagnostic training system  Stackable box for all components
Flange diameter: D=90mm 6 hexagon flange bolts M8x20 Shafts - diameter: D=20mm - short shaft: L=85mm - long shaft: L=200mm - max. permissible bending torques short shaft for belt pulley: 15,9Nm long shaft for mass disk: 3,9Nm
Dimensions and Weight
l x w x h: 600x400x120mm (box) Weight: approx. 3kg
Scope of Delivery
1 pick-up disk 1 long shaft 1 short shaft 1 centering arbor for alignment of shafts in
experimental set-up 6 bolts 1 clamp set 1 storage box with foam inlay 1 manual