On the protective effect of the stress distribution on a lamellar Edo period Samurai helmet: a neutron diffraction study

Abstract

The paper focuses on a seventeenth century Japanese helmet (kabuto) from the Saotome School; previous investigations revealed that its lamellae, made of high-quality low-carbon steel, were assembled following a novel structure that suggested higher resistance to firearms. Neutron diffraction represents the ideal technique for the characterisation of the microstructural properties of metals. In this work, neutron diffraction on a highly collimated instrument, such as ENGIN-X (ISIS, UK), was used to quantify the distribution of residual strains along lamellae arranged in this newly discovered assembly method, and therefore infer on the mechanical properties of the Saotome kabuto. Here, we present novel results investigating residual stresses from diffraction measurements by using the instrument ENGIN-X. This study completes the previous cycle of neutron measurements on this sample and sheds light on the effectiveness of the assembly method of the plates.