Fast Characterization of Fatigue Properties of an Anisotropic Metallic Material: Application to a Puddled Iron from a Nineteenth Century French Railway Bridge

Abstract

Largely used as main material in railway riveted bridges during the second half of the nineteenth century, the puddled iron characterizes for having an anisotropic behaviour due to the large amount of non metallic inclusions that it posses. Its mechanical characterization is thus difficult. Since these ancient structures have supported variable cyclic loadings at least for a century, the determination of the puddled iron's fatigue properties becomes crucial to their maintenance. The self-heating method is proposed in this paper to accomplish this task. The obtained experimental self-heating curves show dispersion non observed in homogeneous materials, this phenomenon is explained by the lack of determination of the representative elementary volume of the puddled iron. However, this data gives us important information such as the minimum and maximum boundaries of the mean fatigue limit for several orientations. A two-scale probabilistic model for high cycle fatigue is also used to represent the dispersion on the experimental data by using Weibull's distribution law to describe several characteristics of each site where the microplasticity occurs. The influence of such parameters and the limitations of the model are also studied.