Abstract
AbstractThe dynamical properties of tire yarns were investigated, the De Mattia method being used for compression fatigue and the Meskat‐Rosenberg‐Hoffmann instrument for the performance during an alternating tensile strength test. Various influences in the test of compression fatigue after De Mattia were investigated. The intensification of the test by increasing the flex angle leads to a considerable decline in tenacity. With increasing the ply twist, the residual strength shows a maximum which lies at an optimum of cord construction. The maximum of the residual strength follows from the increase of the static twist loss and the decrease of the compression fatigue according to the ply twist. The influence of dipping, temperature, and frequency as well as the properties of different cord types were examined. The correlation between tension and flexibility is shown during the alternating tensile strength test of raw cords assuming that both change sinusoidally. Equations for the calculation of the complex modulus, the Young modulus, and the viscosity modulus as well as of the specific damping and the loss energy are stated. Measurements were carried out with viscose improved and viscose super cords and some of the results compared to those for nylon cords. The damping shows in relation to the twist construction a minimum at a constant ply twist and at a certain cable twist which is represented by the ratio Vz of ply/cable twist. A comparison of the two dynamical test methods, i.e., the compression fatigue and the tensile strength test, shows that a maximum residual strength of a certain twist construction corresponds to a minimum in damping and in twist loss. So far there exists a correlation between the static and the two different dynamic tests. Finally, the results of the two dynamic test methods are compared with the properties of cords in the tire. This comparison shows that not even in one case do the results of the laboratory tests contradict the properties of cords in tires, but in most cases correspond to them. Therefore, it can be assumed that it is possible to investigate the dynamic properties of cord twists in tires by laboratory tests with both test methods, i.e., the compression fatigue after De Mattia and the loss energy with the Meskat‐Rosenberg‐Hoffmann instrument.
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