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Advanced Non-Destructive Evaluations Laboratory

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Impact-Acoustic Technique for Sorting Truck Tire Casings


Project funded by Michelin North America, Inc.


Purpose

      Recycling and retreading is the key for reducing costs and energy used for manufacturing of tire casings, thus the cost per mile of operations. This is an environmentally friendly technology since it conserves approximately 15 gallons of crude oil for each retread of a truck tire. However, effective retreads require tire casings with good structural integrity, i.e. without internal cracks and delaminations. The main objectives of this project were:

  • explore a nondestructive method of detection of internal cracks and separations in used tire casings
  • design and build an automated prototype to test and sort 10 - 20 tires per hour without human intervention

Synopsis

    Explore the potential of using an inexpensive nondestructive technique such as impact-acoustic to assess the presence and size of internal voids and separations in used tire casings before their retreading operation.

    Tested tires are tapped on each side by a small impactor containing a load cell that measures the impact force. A miniature microphone senses the acoustic waves generated under impact. A computer controls the impactor and the motor rotating the tire while in the same time records the signals from the load cell and the microphone.


Impact-acoustic prototype designed to test truck tire casings after the worn out tread was removed. Compared with shearography testing where a technician has to assess each image, the impact-acoustic technique could be used as part of an automated line so that a computer will sort casings based on their acoustic energy level.

    The experimental measurements showed that both the peak amplitude and the decay rate of the impact-emitted acoustic waves have a strong correlation with the size of internal delaminations estimated from shearography diagrams. The decay rate seems to be a robust indicator of defects across multiple tire structures exhibiting various levels of damage.


The decay rate of the acoustic signal emitted by the impact proved to be the most significant indicator of the internal defects in tire casings. While a brand new tire had a small attenuation of the sound (lower plot), the tires with medium and large defects exhibited a high attenuation.

B-scan image based on impact-acoustic method for a XZA2 tire as compared to a shearography image. This tire had localized small defect sizes along shoulder one - the side with the DOT mark. The acoustic energy level is relatively small. The second shoulder was relatively clean.

B-scan of another XZA2 tire having medium defect sizes at the second shoulder.

B-scan of a XZA3 tire large defect along shoulder one. The acoustic energy level is large. Our impact-acoustic technique found a defect on the outside of the steel belt that was not detected by the shearography technique. The second shoulder was relatively clean indicating a low acoustic energy.

Selected Publications

Bunget, G., Shen, Q., Gramling, F., Judd, D., and Kurfess, T. - "Impact-Acoustic Evaluation Method for Rubber-Steel Composites: Part I. Relevant Diagnostic Concepts", Applied Acoustics Journal, Vol. 90, p74 - 80, 2015

Bunget, G., Kurfess, T., Shen, Q., Gramling, F., Judd, D. - "Method and Apparatus for Nondestructive Detection of Tire Anomalies" Patent No. WO20150 69218 A1, 2015

High temperatures cause stress on 18 wheeler tires leaving the highways peppered with shredded debris caled "gators" in the trucking industry.

Before their retread all tire casings have to be inspected for internal cracks and delaminations.