Endurance Test Application: Monitoring Failure of Flexible Joint Boots |
Introduction As part of the normal engineering process, it’s often necessary to measure the reliability of mechanical assemblies over long periods of time under various stress conditions. This requires that data on the assembly be recorder and wear out or failure mechanisms be evaluated. Problem In the case of flexible joints on shafts, the parts are rotated at high speeds over an extended period of time to simulate the typical operating life. The failure modes include deformation and cracking of the rubber boots, for which periodic manual observation is the only way of identifying failure. It’s impractical to continuously record video and difficult to capture images of a part spinning at up to 10,000 RPM. Solution A system incorporating an ADwin-light-16 has been designed that allows unattended monitoring of the rubber joint boots over extended periods of time. The ADwin is used to measure the rotational speed of the part via a reflective optical sensor. Next, the ADwin calculates the delay required to achieve an absolute offset (in degrees) that is used to make the part appear to be motionless using a strobe light. The ADwin can also calculate a phase delay that when used in conjunction with the strobe, will make the part appear to rotate at a much slower RPM, typically in the range of 1-10 RPM. Finally, the ADwin is used to trigger a camera which captures a sequence of images that capture a full 360 degree view of the part being tested. A program written in Visual Basic is used to set-up the capture parameters, schedule the periodic collection of the images and store the images in a sequence of files on disk. Benefits By using an automated system, the need to have a person manually inspect the boot for failures has been eliminated. Instead, the history of the complete test is recorded in a sequence of files that can played back later for analysis. By freezing the motion of the part, the joint boot can be inspected without stopping the test and individual sites can be inspected for degradation. Equipment Used
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