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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 setup 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 setup 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 measuring 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 setup)
- detection of cracks in rotating shafts (the elastic rotor)
 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 setup for PT 500 machinery diagnostic training system
 stackable storage system to house the components
Flange diameter: D=90mm
6 hexagon flange bolts M8x20
- 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
LxWxH: 600x400x120mm (storage system)
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 setup
1 clamp set
1 storage system with foam inlay