ITEC 2014 Paper 20: Practical Insights on State-of-the-Art Hunter & Shoeshine Pre-validation Fatigue Test Methods for Tire Reinforcement Materials
|Date Published||September 9, 2014|
Major improvements on steel or fibre cord & fabrics are required to answer the challenging improvements on tire rolling resistance, performance and manufacturing cost. Because of short time-to-market but also because of the high cost of testing on final tyres, there is a big advantage in being able to test the combination of the rubber and its re-enforcement early in the design process. Instead of validating the improvements in combination with the rubber just on static tension & peel strength, it is today important to test new materials in conditions that are close to real usage at the lower stresses and high cycling of real usage. Otherwise possibly the optimising method followed could exclude the solutions that are really needed, since in many cases materials & adhesion with high static strength are not performing as well on fatigue in the final application. The "bend-over-sheave" or "Shoeshine" test method on single and dual layer reinforced rubber samples is helping the tire designer to validate in an early stage the new materials on dynamic stress-compression under bending in similar conditions as the assumptions of the tire design. Because of the high increase in performance of the reinforcement, the dynamic adhesion of the reinforcement with the rubber is a big issue in this industry. This can also be tested efficiently on dual layer samples, whereby the first degradation generally happens in the lower compression layer. Especially for the quality assurance of steel wire & cord, the additional "bend-rotation" high speed alternate bending method should be seriously considered. By this method typical failures like surface defects, inclusions & metallurgical deviations are detected while they are not affecting the classical static tensile test results. Examples will be shown about these tests and about what results can be expected: validation on single & reverse fatigue bending, dynamic cord tension-compression, dynamic adhesion with the rubber, early warning stop to be able to observe the reason of the start of the degradation, comparison of constructions on sample heat generation. Presented by Philippe van Bogaert, Founder, Bogimac.