Effect of Combined Misalignments on Vibrations of a Single-Stage Spur Gear Transmission System: An Experimental Approach

Failures in mechanical power transmission systems can cause serious operating problems in
the systems to which they belong. Misalignments in the shafts of gear transmission systems can produce
transmission errors, increased bending stress at the base of the teeth, and increased normal wear between
the teeth. Because vibration analysis is very useful as a failure detection mechanism in stationary rotating
equipment, the effect of shaft misalignment on vibration measurements was investigated in this study.
Combined misalignments are studied because different types of misalignments occur simultaneously in
real applications. The effect of a combination of axial, radial, and angular misalignments on vibration
measurements in a spur gear transmission system was investigated. This study was developed through the
design and construction of a test bench that allows different types of misalignment in a single-stage spur gear
transmission system and vibration measurement through accelerometers installed in the support bearings.
Indicators, such as kurtosis and skewness, were used to validate the results in the time domain. For the
frequency domain analysis, an indicator was developed that compares the frequency spectra of misaligned
conditions to the base spectrum in the aligned condition. The critical misalignment combinations were also
identified. It was found that for the combined cases, the contact area between the teeth and the contact ratio
were influencing factors. The quantitative effects of combined misalignments on vibration measurements
were determined, which can be used as a preliminary diagnosis of this type of problem and as a basis for
developing more robust prediction models.