Southwest Research Institute® (SwRI®) News
CIBLE Automatic Bearing Inspection System
San Antonio, Texas -- Sept. 15, 1977 -- A computer-assisted, automatic bearing inspection system developed by Southwest Research Institute® (SwRI®) has been honored as one of the 100 most significant new technical products of the year.
The system was chosen as a winner in the 1977 I-R 100 Competition sponsored by Industrial Research magazine, officials of the publication announced in Chicago.
Known as the Mark I CIBLE (Critical Inspection of Bearings for Life Extension), this system provides a significantly improved means of inspecting rolling element bearings used in gas turbine engines, said John R. Barton, leader of the CIBLE development group. He is vice president in charge of the SwRI Instrumentation Research Division.
The job of inspecting critical jet engine bearings for potentially dangerous flaws is comparable to looking for a pea which may be hidden in one of many football fields, he said. CIBLE is capable of detecting such tiny, hidden defects.
The bearings under study assemblies of balls or rollers held between inner and outer raceways measuring from about 3 to 15 inches in diameter are precision components costing generally between $500 and $5,000 each. Noting this cost, Barton pointed out that extension of a bearing's lifetime through reliable prediction of a safe operating period could result in significant savings.
Instead of the current visual and manual inspection procedures, the SwRI automatic system examines bearings through use of three sensitive techniques of nondestructive evaluation (NDE):
Magnetic perturbation, which detects flaws by their characteristic disturbances of a magnetic flux, is used to find subsurface and surface inclusions and other defects.
Laser scattered light provides a sensitive evaluation of surface finish.
The Barkhausen noise technique, which makes use of signals produced by minute movements of small magnetized areas under the influence of a changing magnetic field and stress, is used to evaluate surface and near surface conditions of residual stress, either in compression (beneficial) or tension (undesirable).
The inspection system is designed for rapid change of fixtures required for different bearings. During an examination, a printout of signal locations is provided, and a permanent magnetic tape record is made of individual bearing NDE profiles.
The research unit in use at the Institute is one of three inspection systems, Barton said. A second unit, which like the SwRI system is designed for use with inner and outer bearing races, is now in service at the Corpus Christi (Texas) Army Depot. Another prototype, equipped to inspect balls and rollers as well as raceways, has been delivered to the Air Force Logistics Command at Tinker Air Force Base, Oklahoma City.
These inspection systems will be used to evaluate large numbers of bearings, Barton said, in studies aimed ultimately at the development of serviceability criteria based on actual service experience.
Laboratory investigations have verified both the effectiveness of the NDE methods in flaw detection and their capability of predicting bearing life, he explained. But field studies are needed because it is not now possible to determine the extent to which laboratory experience, in terms of the dominance of sources of failure, is representative of actual service experience.
In these long term studies, Barton said, new and used bearings will be inspected, and the same bearings will be re-inspected during periodic engine overhauls. Any indications of defects will be compared with stored NDE profiles, and common features will be sought. Gradually, in this way, relationships will be developed between NDE signature characteristics and bearing service experience.
A 5-year investigation of this kind is being conducted for the Air Force, he said. The Army is considering a similar program involving bearings of special interest to its requirements.
For more information about the CIBLE Automatic Bearing Inspection System, contact Joe Fohn, Communications Department, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas, 78228-0510, Phone (210) 522-4630, Fax (210) 522-3547.