Investigation of service failures of steel music wire

Abstract

An investigation of a number of service failures of the hard steel strings of plucked musical instruments is reported. All the failed strings were found to contain transverse fatigue cracks, mostly located near the end of the vibrating length (e.g. at the “bridge” of the instrument) and extending to about one third of the section thickness. One wire had corroded severely before failing in fatigue. Final failure occurred by ductile fracture. An analysis of the service stresses showed that the strings are subjected to high mean tensile stresses resulting principally from elastoplastic bending opposite the failure location. It is shown that a small cyclic axial tension arises from repeated plucking during playing and this can lead to fatigue initiation and propagation over a large proportion of the wire cross section. Neither surface nor bulk defects, wear nor contact stresses were found to be factors of importance in the cases examined, contrary to some speculation.