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

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.