Automated U-Bolt Inspection System

Abstract

Consolidated Metal Products has a unique cold-forming process to create U-bolts that makes them
the industry leader in U-bolt production. This process has a tendency to create cracks due to high residual
stresses. The senior design team researched several methods of crack detection including ultrasonic, dye
penetrant, and visual camera inspection. The conventional ultrasonic method was tested by NDT systems in
house and was shown to work with the curvature of the U-bolt. Fluorescent dye penetrant was tested by
applying the dye to the bolts with, and without cracks in them and then observed the difference in light values
in and out of the cracks. Camera inspection was tested statistically by comparing light intensity values inside
and out of crack areas on gathered images without the application of dye. After testing these methods, camera
inspection was chosen through the use of a selection matrix. In The senior design, the team began with
construction of a controlled lighting environment box for taking photographs of U-bolts. A Matlab code was
formed to compare light intensity values of bolt images and to work in unison with an Arduino to output
separate signals for normal and defective U-Bolts. The Matlab code also automatically analyzed images taken
by the camera. The Matlab code was then tested with sample bolts. Threshold light values were obtained to
optimize the system’s ability to detect cracks.