Yokohama Rubber Co., Ltd., in partnership with a professor at Kanazawa University has developed a evaluation technology that can improve the performance of tires on ice. The technology was developed at the Tribology Laboratory which is headed by Associate Professor Iwai of the College of Science and Engineering at Kanazawa University and helps visualize rubber’s frictional state of contact on an icy surface. This new technology is expected to facilitate the discovery of new compounding agents having excellent water absorbency so that tire companies can develop tread patterns that can deliver higher drainage performance in a more precise manner. The technology is expected to lead to the development of winter tires having significantly better performance on ice.
When tires are used on icy surfaces, if they do not make firm contact with the road surface due to the watery film that the icy surface generates, it can significantly reduce the tire’s grip. In order to counter the effects of the watery film, studless snow tires use water absorbing agents and tread patterns with high drainage performance. One difficulty in developing such tires is that when experts need to observe the tires’ contact with the road, it has been difficult to distinguish the area where water is between the road surface and the rubber from the area where the tire is in direct contact with the road surface. Thus, it is difficult to measure the area of real contact.
The joint research project between Yokohama Rubber and Kanazawa University came up with a specialized testing machine having a high-speed camera. This camera facilitates visualization of the tires’ contact with the ground and can help assess the extent of the real contact area. Furthermore, by establishing an analytical technique for digitizing contact images, Yokohama Rubber succeeded in numerically evaluating the water absorbency and drainage of tire rubber.
The specialized testing machine can directly observe frictional behavior between a sample of rubber and ice or a smooth transparent disk which is used to replicate ice at speeds of up to 50km/hr. The high-speed camera can take as many as one million micro-level images per second of the tire rubber’s contact area with the road surface. At the same time, it is capable of measuring the frictional force during the test.
The images taken with this testing machine are dark only in the areas where there is real contact. Rubber having a water-absorbing agent shows darkness over a wider area than rubber that does not include the water-absorbing agent. Moreover, as a result of digitizing the image with the newly developed analytical technique to associate the contact area with the frictional force, it was revealed that the calculated numerical value has a high correlation with the frictional force of the rubber.
Yokohama is aiming for leadership in winter tires that are supplied to the European, Russian and Japanese markets as part of its consumer tire strategy in its three-year medium-term management plan, the Grand Design 2020 (GD2020), which was launched in 2018.
Yokohama Rubber is using the new technology widely in its development of a broad range of winter tires, from studless snow tires for Japan to winter tires for the European market and all-season tires. Using this technology, Yokohama Rubber will accelerate product development as it aims to build leadership in the performance of winter tires.
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