MUSCATINE, Iowa-Preventing a catastrophic ``zipper'' failure in a truck tire may become easier with the application of some new technology currently used in the aerospace industry. A three-year joint research and development venture between Laser Technology Inc. (LTI) of Norristown, Pa., and Muscatine-based Bandag Inc. has resulted in development of a new capability in sidewall tire inspection.
The procedure, Bandag said, is based on a specific type of laser technology that combines solid state lasers, image shearing technology, electronics and proprietary software to examine casings for possible structural weaknesses in a tire's sidewall areas. Those can cause what is commonly known in the industry as ``zipper'' ruptures that result in a tire failure.
Bandag claims ``no other commercially available technology gives the operator such easy-to-use information about the tire's condition.''
John Newman, LTI's president, told TIRE BUSINESS that with his company's system-which he believes is the first of its kind on the market-an operator can push a button and test both sidewalls of a tire in less than two minutes. The equipment takes a photo that will indicate whether the sidewalls aregood or bad.
``It's much easier to interpret and a lot less tiring on the operator, who can run another machine at the same time,'' he said.
X-ray equipment-in use in some retread shops to detect degradation of a tire's radial cables-is limited, Mr. Newman explained, because an operator ``must stay glued to the screen,'' constantly watching every cable as it is scanned by X-ray at 10 wires per inch. ``If he blinks, he can miss one.
``Our unit looks for stress concentrations when there's degradation to the wire, and we get (a photo) and a video picture that shows where the flaws are located.''
Although Bandag acknowledged such a ``breakthrough in inspection technology could easily provide a significant technology advantage'' for the company, it said the importance of sidewall inspection to the retreading industry caused it to reconsider putting any restrictions on the product's availability.
``For years there has been talk in the tire industry of developing a safe, reliable method for positively identifying sidewall defects,'' Bandag stated in an Oct. 2 press release, ``but nothing practical ever materialized. This technology provides the capability of doing so with a non-destructive method.''
Because of its significance to the tire and trucking industries, both LTI and Bandag decided to market the LTI Sidewall Inspection System to anyone through LTI.
Expected to be available around mid-November, the system will initially be marketed for $69,950, Mr. Newman said. It will be manufactured in LTI's plant in Norristown, where the company incorporates the same technology in units it builds to test tires for belt-edge separations, bead blisters and other defects.
The company will install and set up the new system for customers, Mr. Newman said, as well as provide training and a warranty.
Nate Derby, LTI's vice president, engineering, said there was ``tremendous pressure on us'' to develop a way to identify possible zipper defects. ``When we finally saw what this sidewall inspection technology was capable of doing, we knew we had to share this with the industry.''
To prove the effectiveness of the new system, Mr. Newman said LTI conducted tests in Bandag retread shops, X-raying and bursting thousands of tires.
The technology originated in the aerospace industry, where LTI does most of its business, he said. ``We invented it to do non-destructive testing of composite materials on the B-2 Stealth bomber and the space shuttle.''
Since the International Tire and Rubber Association (ITRA) in Louisville, Ky., has not yet tested the capabilities or accuracy of the LTI system, Bill Gragg, ITRA's technical director, said he couldn't comment on the equipment.
However, he did offer somewhat of a layman's explanation of image shearing (shearography). It is, according to Mr. Gragg, a method in which a ``sheared image'' is obtained by photographing, with a lens that has a prism over half of it, a subject that is illuminated by a laser.
``That will take a photograph of the object's displacement gradient,'' he said. ``For example, if you see a separation in a tire, it will curve upward away from its base and form a little hill.
``If you look at that as a sort of topographic map of the area, it makes a topographic or `shearographic' image of that separation.''
On the other hand, inspection via holography does not ``shear'' the image, he said, but just measures the displacement of the rubber.
LTI has about 250 similar systems in use worldwide for military aerospace applications, and also is becoming active in the commercial aircraft sector.
LTI Sidewall Inspection System
Laser Technology Inc. photo