Some recent innovations for production of high-strength and fatigue-resistant 3-strand and 4-strand wire ropes

Some recent innovations for production of high-strength and fatigue-resistant 3-strand and 4-strand wire ropes

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On this 175th anniversary of Albert’s first 3-strand wire rope, it is fitting to present some recent innovations in the design and manufacture of 3-strand and 4-strand wire ropes. This paper will present the results of a novel method of manufacturing a 3- strand rope from AISI Type 304 stainless-steel wires. This method manipulates the state of residual stresses in the cold-drawn stainless-steel wires to achieve an increased level of fracture toughness and in turn yielding a rope with higher strength and endurance. The actual residual stresses present in the wires at different stages of manufacturing were measured using the X-ray diffraction technique. The measured values of residual stress are reported showing that the state of residual stress present in the cold-drawn wires can be changed from an undesirable tensile state to a very desirable compressive state. The highest tensile residual stress in the mid-section of a 1.1 mm wire was 369 MPa. The tensile residual stress at the midsection was decreased to 77.9 MPa while a compressive residual stress of 209 MPa was imparted on the outer surface of the wires. The 12.7 mm 3×36 WS wire ropes containing the above mentioned thermally and mechanically stress relieved wires were subsequently tensile tested showing that the strength-to-weight ratio for the rope produced with the novel method was 20% higher than that of a rope of the same diameter produced with the standard method. The reverse-bend-fatigue cycles to failure were also increased by 65% for the rope made with the novel method. A comparison of fracture toughness of the wires is made indicating that the novel method increased the fracture toughness of the individual wires. SEM photographs of fractured ends of wires will be presented as well as the results of the X-ray diffraction method of residual stress measurement. Several applications in which the above described novel ropes have been successfully used will be described.

Author(s): Pourladian, B.