MRS Proceedings


Why is the Japanese Sword Curved ?

1990 MRS Spring Meeting.

William N. Weins Ph.D. P.E.a1 and Peter Bleed Ph.D.a2

a1 University of Nebraska, Department of Mechanical Engineering, Lincoln, Nebraska 68588-0656

a2 University of Nebraska, Department of Anthropology, Lincoln, Nebraska 68588-0368


The history and methodology of Japanese swordmaking are reviewed with particular reference to materials and processes. In order to gain a better understanding of the structure/property relationships in Japanese swords, a 16th century katana was analyzed metallographically and by attaching strain gages and cutting to relieve the residual stresses in the blade. The results indicate that the curve in the blade can be attributed to the volumetric expansion of the untempered martensite on the cutting edge, which also causes the edge to be in a state of residual compression. The residual compressive stresses are one of the key elements of the Japanese sword which give it superior toughness and cutting ability.