Influence of Fatigue Loading on the Residual Stress Distribution in Prestressing Steel Wires

Abstract

Abstract: This paper analyzes the influence of fatigue loading on the residual stress profile in high strength steel wires. To this end, different sinusoidal loads with diverse values of maximum loading level and number of cycles were simulated on wires in which s everal residual stress profiles had been previously introduced, some of them with a tensile state and others with a compressive state. An analysis was made of the evolution with time of such residual stress laws by comparing them at key instants of loading, that is , at initial instant, at maximum load, at minimum load and at final instant. Numerical results show only a minor influence of fatigue loadin g on the residual stress profile. Key words: Prestressing steel wires, cold drawing, fatigue, residual stress redistribution. 1. Introduction  The drawing process applied in the manufacture of prestressing steel wire (widely used in structural elements) usually produces residual stresses in the material [1, 2], even without any external loading or thermal gradients applied on the wire. The profile of these stress states can present different configurations [3], but in all of them the maximum value of stress is placed at the external surface of the wire. The evolution of the residual stress is decreasing with depth until reaching a value after which it may be assumed as constant throughout the internal section of the wire. Common values at which residual stresses become zero are usually about a tenth of millimetre [3]. Residual stresses play an important role in the process of initiation of surface cracks. It is well known that the industrial use of different surface treatments, e.g., shot peening, provides compressive residual stress at the material surface, thus delaying the initiation and propagation of cracks [4]. For these reasons it is essential to know the evolution of the residual stress