Beloit Technologies, Inc.

Beloit Technoloiges, Inc.

Dennis A White

Richard L Fearnside

Gordon R Voll

The bonding of an elastomeric cover to a metal roll is tested by transmitting audible frequency waves through the compliant roll cover and receiving the waves at a transducer mounted to the underlying steel roll. The resulting signal may be analyzed by a technician listing to the audio frequencies transmitted. The audio range of frequencies employed may be about 5000 Hz. The elastomeric material such as rubber does not transmit sound without considerable loss of amplitude, whereas sound travels at high speed through steel with little attenuation. A sound transmitter is spirally scanned along the rubber-covered surface of the roll, transmitting into the steel roll directly beneath the sound transmitter and throughout the roll. Sound is detected at a transducer mounted at the roll ends. Any failure or significant variation in the roll/cover bond is detected by the effect on the quality of sound transmitted through the rubber steel interface.

Detection of delamination of rubber covers from metal substrates

Radially spaced calibration holes are drilled parallel to the exterior surface of a cylindrical shell for a dryer roll. An ultrasonic transducer is mounted in a fixture filled with a coupling medium which allows for adjustment of the spacing and angle of the transducer which traverses the shell as it is rotated. The transducer produces a signal directed to the shell. A computer calculates the time the signal takes to travel from and return to the transducer and the depth of the shell from which the signal returns. A clear signal corresponding to holes up to one inch from the surface are found by adjusting the ultrasonic transmission angle. This angle is approximately 23 degrees from a normal to the casting surface. The calibrated transducer traverses the surface of the shell. The signals are gathered and stored to create data which may be used in maintaining the shell for the dryer roll.

Ultrasonic inspection method

When an ultrasonic transducer for detecting discontinuities and/or delaminations in a thin layer of coated material applied to a metal plate or the outside wall or surface of a cast iron dryer cylinder is directed at the coated surface to be inspected at a particular angle, about 10 percent of the single will appear as Harris waves which propagate into the coated test plate at 90 degrees to the surface. This signal which propagates vertically is polarized, with the result that the signal has a greatly improved signal-to-noise ratio. For incident medium of Lucite and employing shear wave refracting in the medium of Lucite, the specific angle is approximately 66 degrees from the vertical for best signal-to-noise ratio. Shear or longitudinal waves can be employed to affect the detection of subsurface defects with the particular angle changing depending on the relation of the velocity of the sound waves in the refracting medium to the velocity of sound waves in the incident medium.

Ultrasonic examination of coated parts

When an ultrasonic transducer for detecting flaws in metal plates or the wall of a metal cylinder is directed at a surface to be inspected at a particular angle, about ten percent of the signal will appear as Harris waves which propagate into the test plate at ninety degrees to the surface. This signal which propagates vertically is polarized, with the result that the signal has a greatly improved signal to noise ratio. For an incident medium of water and employing shear wave refracting in the medium of cast iron the specific angle is approximately 33 degrees from the vertical for best signal to noise ratio. For steel the specific angle is approximately 31 degrees and is about 50 degrees for brass. Shear or longitudinal waves can be employed to affect the detection of subsurface defects with the particular angle changing depending on the relation of the velocity of the sound waves in the refracting medium to the velocity of sound waves in the incident medium.

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St. George Island, FL, United States of America

Dennis A White