Uniaxial Tension Fatigue Test of Asphalt Concrete—An Improved Framework

Abstract

Abstract The stress and strain distributions in the uniaxial tension fatigue test are homogeneous and are better estimated than in the beam fatigue test. This condition is of utmost importance when analyzing the test using viscoelastic continuum damage (VECD). The uniaxial tension is nowadays conducted using crosshead displacement control. The strain control condition is difficult to realize with crosshead control. The paper proposes to use two extensometers with an averaging cable to control the strain in the central part of the specimen in the same manner as the load cell is used to control the stress and avoid the problems caused by the crosshead displacement control. The fatigue test history contains millions of data points and poses some difficulties in using the full-time history in the analysis of the test. It is proposed to conduct dynamic modulus and uniaxial tension fatigue tests on the same specimen and to implement numerical integration that reduces the computation effort. The analysis of two fatigue tests suggests that, with the full-time history, it is possible to: (1) Obtain an additional damage parameter, in addition to the maximum pseudo stiffness (PS). The maximum PS is calculated from the peaks of the stress and pseudo strain and represents the material state at the peak loading condition and at failure. The slope PS is calculated at beginning of the loading as the ratio of the damaged and undamaged moduli. It represents the material state at the end of the loading cycle; and (2) To make a more accurate estimation of the internal variable S which may be used as a material performance parameter.