STP694

    Laboratory Machine to Evaluate the Resistance of Tire Cords (Textile or Steel) to Tensile Fatigue or Compressive Fatigue or Both

    Published: Jan 1979


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    Abstract

    A device for measuring the fatigue resistance of tire reinforcing materials at pure tensile or compressive strain is described.

    If a pure bending moment is applied to a specimen like the complex beam used in the Simoni-Canevari “bending dynamometer” the specimen deforms like an arc of a circle and will be subjected to pure tensile or compressive stresses according to the direction of the bending. After a mathematical study had shown the possibility of the construction, we thought of building a machine capable of bending this kind of specimen cyclically as an arc of a circle. With this machine we achieved compression or tension or both in cycles at different stress levels (both as regards the average value and range) by changing the length of the connecting rod and the crank.

    The first results of the study of steel cord fatigue made on this device were related to belt fatigue performance of car tires. We have found: (a) on the tire, the indoor fatigue life measured at different lateral forces followed a trend that can be described by the curve in Fig. 1; (b) on the specimen, by increasing the strain on the cord, its life decreased with a similar law; (c) on the specimen, by appling dissymmetrical strains at equal total strain we obtained longer lives, with different behaviors if the mean strain were on the tensile side or on the compressive side; and (d) the visual aspects of the failures obtained with the machine were the same as those obtained in the tires tested on the road.

    Keywords:

    bending dynamometer, cord, fatigue (materials), indoor test, reinforcing material, rubber, specimens, test, tires


    Author Information:

    Canevari, C
    Tire reinforcing materials director and senior researcher, Industrie Pirelli S.p.A., Milano,

    Lala, AG
    Tire reinforcing materials director and senior researcher, Industrie Pirelli S.p.A., Milano,


    Paper ID: STP36947S

    Committee/Subcommittee: D13.19

    DOI: 10.1520/STP36947S


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