Prestressing steel wires usually undergo cyclic loading in service. Therefore, it is of interest to analyse certain features of their mechanical behaviour under this type of loading, such as the Bauschinger effect (BE) or the hardening rule, that fit the real mechanical behaviour appropriately. In this study, different samples of high strength pearlitic steel wires were subjected to cyclic tension-compression load exceeding the material yield strength, thus generating plastic strains. From the experimental results, various parameters were obtained revealing that analysed steels exhibited the so-called Masing type BE. In addition, the variation of the BE characteristics (of the effective and internal stresses) with the applied plastic pre-strain indicated that the studied materials followed a mixed strain hardening rule with the domination of the kinematic component.

Prestressing steel wires are commonly used as reinforcement elements in structures bearing fatigue loads. These wires are obtained by a conforming process called cold drawing, where a progressive reduction of the wire diameter is produced, causing residual stress in the commercial wire. The aim of this paper is to analyze the effect of diverse in-service cyclic loading conditions (cyclic loading and cyclic loading with overload) on such a residual stress field. To achieve this goal, firstly, a numerical simulation of the wire drawing process of a commercial prestressing steel wire was carried out to reveal the residual stress state induced by the manufacture technique. Afterwards, a numerical simulation was performed of the in-service loading conditions of a prestressing steel wire in which the previously calculated residual stress state is included. The analysis of the obtained results shows a significant reduction of the residual stress state of about 50% for common in-service loadings and as high as 90% for certain cases undergoing overloads during cyclic loading. Therefore, an improvement of the mechanical performance of these structural components during their life in-service can be achieved.

Round-notched samples are commonly used for testing the susceptibility to hydrogen embrittlement (HE) of metallic materials. Hydrogen diffusion is influenced by the stress and strain states generated during testing. This state causes hydrogen-assisted micro-damage leading to failure that is due to HE. In this study, it is assumed that hydrogen diffusion can be controlled by modifying such residual stress and strain fields. Thus, the selection of the notch geometry to be used in the experiments becomes a key task. In this paper, different HE behaviors are analyzed in terms of the stress and strain fields obtained under diverse loading conditions (un-preloaded and preloaded causing residual stress and strains) in different notch geometries (shallow notches and deep notches). To achieve this goal, two uncoupled finite element (FE) simulations were carried out: (i) a simulation by FE of the loading sequences applied in the notched geometries for revealing the stress and strain states and (ii) a simulation of hydrogen diffusion assisted by stress and strain, for estimating the hydrogen distributions. According to results, hydrogen accumulation in shallow notches is heavily localized close to the wire surface, whereas for deep notches, hydrogen is more uniformly distributed. The residual stress and plastic strains generated by the applied preload localize maximum hydrogen concentration at deeper points than un-preloaded cases. As results, four different scenarios are established for estimating “a la carte” the HE susceptibility of pearlitic steels just combining two notch depths and the residual stress and strain caused by a preload.

Stress corrosion cracking (SCC) of metals is an issue of major concern in engineering since this phenomenon causes many catastrophic failures of structural components in aggressive environments. SCC is even more harmful under cathodic conditions promoting the phenomenon known as hydrogen assisted cracking (HAC), hydrogen assisted fracture (HAF) or hydrogen embrittlement (HE). A common way to assess the susceptibility of a given material to HAC, HAF or HE is to subject a cracked rod to a constant extension rate tension (CERT) test until it fractures in this harsh environment. This paper analyzes the influence of a residual stress field generated by fatigue precracking on the sample’s posterior susceptibility to HAC. To achieve this goal, numerical simulations were carried out of hydrogen diffusion assisted by the stress field. Firstly, a mechanical simulation of the fatigue precracking was developed for revealing the residual stress field after diverse cyclic loading scenarios and posterior stress field evolution during CERT loading. Afterwards, a simulation of hydrogen diffusion assisted by stress was carried out considering the residual stresses after fatigue and the superposed rising stresses caused by CERT loading. Results reveal the key role of the residual stress field after fatigue precracking in the HAC phenomena in cracked steel rods as well as the beneficial effect of compressive residual stress.

Prestressing steels, obtained by cold drawing, are highly susceptible to hydrogen embrittlement (HE) phenomena. Stress and strain fields produced by cold drawing play an essential role in this process since they affect hydrogen diffusion. Therefore, variations of such fields due to changes in drawing conditions could modify life in-service of these structural components. In this work the effect on HE of a parameter of the wire drawing process, the bearing length, is analyzed by means of diverse numerical simulations by the finite element method (FEM). The results of this work allow the definition of a characteristic value of the die bearing length equal to the wire radius, and demonstrate that the effects of stress-strain fields produced by wire drawing on HE are reduced when the bearing length exceeds such a characteristic value, so that the optimum cold drawing process is that with a bearing length higher than the wire radius.