Hüllkurvenanalyse

Hüllkurvenanalyse, also known as envelope analysis, is a diagnostic technique used in vibration analysis to detect and diagnose faults in rolling element bearings. It is particularly effective for identifying localized defects such as cracks, spalls, and pits on the bearing races or rolling elements. The principle behind envelope analysis is that impacts generated by a defect in a bearing will excite the natural frequencies of the bearing housing or surrounding structures.

These natural frequencies are often in the ultrasonic range, far above the fundamental frequencies of vibration associated with the bearing's rotation or ball passing frequencies. By filtering the vibration signal to isolate these high-frequency components and then demodulating the signal, the energy associated with these impacts can be amplified. This amplified signal is then analyzed in the time or frequency domain. Peaks in the envelope spectrum at characteristic bearing defect frequencies indicate the presence of a fault.

The process typically involves acquiring high-frequency vibration data using accelerometers. This data is then passed through a band-pass filter set to cover a range of the natural frequencies of interest. The filtered signal is then demodulated, often using a rectifier and a low-pass filter, to extract the amplitude modulation caused by the repetitive impacts. The resulting envelope signal is then analyzed for patterns. The effectiveness of Hüllkurvenanalyse relies on accurately identifying the bearing's natural frequencies and the characteristic defect frequencies. It is a powerful tool for early fault detection, allowing for planned maintenance and preventing catastrophic failures.