AI X-Ray and Shearography in Tire Manufacturing Inspection

This article explores the advanced non-destructive testing methods used by modern tire manufacturers to ensure structural integrity before high-speed highway testing. Specifically, it details how shearography interferometry detects internal belt separations through vacuum-induced surface deformation, and how artificial intelligence analyzes X-ray imaging to identify microscopic cord anomalies and ply-angle deviations. By combining these technologies, manufacturers prevent catastrophic tire failures and optimize quality control.

Shearography Interferometry for Belt Separation Detection

Shearography interferometry is a laser-based optical method used to find air pockets, delamination, and belt separations trapped deep within a tire's rubber layers. Unlike traditional visual inspections, shearography measures microscopic surface deformations caused by subsurface defects.

The process works through the following steps:

  1. Baseline Imaging: The tire is placed inside a sealed chamber. A coherent laser illuminates the tire, and an image-shearing camera captures the baseline reflection, known as a speckle pattern.
  2. Stress Application: The chamber creates a partial vacuum, lowering the ambient pressure around the tire. If there is a trapped air pocket or a separation between the internal belts, the drop in external pressure causes that specific area to expand slightly.
  3. Interferometric Comparison: The camera captures a second speckle pattern while the tire is under vacuum stress. Software subtracts the baseline image from the stressed image to create an interferogram (fringe pattern).
  4. Anomaly Identification: Uniform rubber expansion produces a smooth, predictable pattern. However, an internal belt separation causes an localized bulge on the tire's surface, measured in nanometers. This deformation shows up on the interferogram as a distinct "butterfly" or bullseye fringe pattern, pinpointing the exact location and size of the separation.

X-Ray Ply-Angle Artificial Intelligence for Cord Anomalies

While shearography excels at finding trapped air and layer separation, it cannot evaluate the alignment or integrity of the internal steel and textile cords. To inspect the skeletal structure of the tire, manufacturers use real-time X-ray imaging paired with artificial intelligence.

Inside a tire, steel belts and carcass plies must be laid at precise angles to handle cornering forces and maintain stability at high speeds. Manual inspection of X-ray images is slow and prone to human fatigue, leading manufacturers to deploy computer vision and deep learning algorithms.

The AI-driven X-ray inspection process operates as follows:

  • Radiographic Scanning: A radiation source is positioned inside the tire while an X-ray detector moves along the outside, capturing a continuous, unwrapped 360-degree radiographic image of the internal structure—from bead to bead.
  • Ply-Angle Measurement: Convolutional Neural Networks (CNNs) analyze the X-ray feed in real time. Using edge-detection algorithms, the AI traces the path of the steel cords and calculates the exact angle of the plies relative to the tire's centerline. If the ply angle deviates by even a fraction of a degree from engineering specifications, the tire is flagged.
  • Cord Anomaly Detection: The AI is trained on thousands of defect images to recognize structural flaws instantly. It scans for broken steel cords, overlapping wires, excessive spacing (gapping) between cords, and foreign metallic objects embedded in the rubber.
  • Splice Inspection: The system also evaluates the belt splices—where the ends of the steel belts meet—ensuring they do not overlap too much (causing a heavy spot) or pull apart (creating a weak point).

Pre-Qualifying Tires for High-Speed Highway Testing

High-speed highway testing subjects tires to extreme centrifugal forces, rapid flexing, and intense heat build-up. If a tire enters this testing phase with an undetected belt separation or a misaligned ply angle, the defects will rapidly propagate.

A microscopic air pocket will expand as the tire heats up, tearing the rubber layers apart and leading to a tread separation. Similarly, broken or misaligned cords create uneven tension across the tire footprint, leading to localized overheating and structural blowouts.

By integrating shearography and AI X-ray systems directly into the production line, manufacturers create a two-stage digital filter. Shearography guarantees the chemical and physical bonding of the rubber layers, while AI X-ray verifies the mechanical alignment of the steel skeleton. Only tires that pass both non-destructive evaluations are cleared for the rigors of high-speed highway testing, ensuring both test driver safety and accurate performance data.