This research demonstrates two methodologies for detecting cracks in a metal spindle housed deep within a vehicle wheel end assembly. First, modal impacts are imposed on the hub of the wheel in the longitudinal direction to
produce broadband elastic wave excitation spectra out to 7000 Hz. The response data on the flange is collected using
3000 Hz bandwidth accelerometers. It is shown using frequency response analysis that the crack produces a filter, which
amplifies the elastic response of the surrounding components of the wheel assembly. Experiments on wheel assemblies
mounted on the vehicle with the vehicle lifted off the ground are performed to demonstrate that the modal impact method
can be used to nondestructively evaluate cracks of varying depths despite sources of variability such as the half shaft
angular position relative to the non-rotating spindle.
Second, an automatic piezo-stack actuator is utilized to excite the wheel hub with a swept sine signal extending
from 20 kHz. Accelerometers are then utilized to measure the response on the flange. It is demonstrated using
frequency response analysis that the crack filters waves traveling from the hub to the flange.
A simple finite element model is used to interpret the experimental results. Challenges discussed include
variability from assembly to assembly, the variability in each assembly, and the high amount of damping present in each
assembly due to the transmission gearing, lubricant, and other components in the wheel end. A two-channel
measurement system with a graphical user interface for detecting cracks was also developed and a procedure was created
to ensure that operators properly perform the test.