Effect of transversal loading on the fatigue life of cold-drawn duplex stainless steel

Abstract

The paper gives new insights on failure behavior of high-strength, heavily cold-drawn duplex stainless steel wires when simultaneously subjected to static transverse and longitudinal loadings, with the latter ones being of a fully tensile or cyclic nature. The wires might experience such combined actions when incorporated into strands of pre or post-tensioned cable systems, today used in a wide spectrum of construction applications. The transversal loads are due to the contact forces between the wires, and mainly occur by longitudinal tensioning of strands. In order to reproduce them, the experiments were made with a specially designed device assuring the control of the locally applied transversal compression during the wire loading in simple or cyclic tension. The results concerning the static bi-axial loading did not show significant differences concerning the failure load of duplex stainless steel wires when compared with that of currently used prestressing eutectoid wires: on this basis, an empirical fracture criterion predicting the critical load combinations was formulated. The simultaneous action of transverse compressive loading and fatigue tensile loading of 200 MPa stress range produces a nominally infinite lifetime of lean duplex wires for combinations of the compressive and maximum tensile loads experimentally determined. These combinations could be roughly described as those given by compressive loads or maximum tensile fatigue loads higher than 50% of the tensile bearing capacity of lean duplex wire.