The Relationship Between Microstructure and Mechanical Properties of Late 19th/Early 20th Century Wrought Iron Using the Generalized Method of Cells Model

Abstract

ABSTRACTThe discovery of the RMS Titanic has led to a number of scientific studies, one of which addresses the role that the structural materials played in the sinking of the ship. Chemical, microstructural, and mechanical analysis of the hull steel suggests that it was state-of-the-art for 1912 with adequate fracture toughness for the application. However, the quality of the wrought iron rivets may have been an important factor in the opening of the steel plates during flooding. Preliminary studies of Titanic wrought iron rivets revealed an orthotropic, inhomogeneous composite material composed of glassy iron silicate (slag) particles embedded in a ferrite matrix. To date, very little is understood about the properties of wrought iron from that period. Therefore, in order to assess the quality of the Titanic material, contemporary wrought iron was obtained from additional late 19th/early 20th century buildings, bridges, and ships for comparison. Image analysis completed on the Titanic wrought iron microstructure showed a high slag content that is very coarse and unevenly distributed. To investigate how microstructure impacts the mechanical properties, and hence the quality of late 19th/early 20th century wrought iron, a detailed analysis of the relationship between the microstructural features and the mechanical behavior was completed. Here we present the first step in that process: the use of the Generalized Method of Cells (GMC) to predict the mechanical response of composites with variable microstructural properties. The GMC tool is used to generate the effective inelastic behavior of the composite from the individual constituent properties.