Material Properties of Wire for the Fabrication of Knotted Fences

This paper describes the materials properties of galvanised fencing wire, as used in the fabrication of knotted wire fences. A range of physical properties are investigated: tensile strength, ductility in tension, Young’s modulus, three-point bending, and bending span. A range of commercially available wire products were tested. The results show that most, but not all, high tensile wire samples met the minimum tensile and ductility requirements. Young’s modulus results failed to provide any meaningful insights into wire quality. Flexural modulus results also failed to provide any insight into wire quality issues, with no statistically significant differences existing between acceptable and problematic wire batches. The implications are that premature fence failures are unlikely to be caused solely by reduced tensile properties. Existing test methods, including tensile strength and ductility, are somewhat incomplete, perhaps even unreliable, as measures of wire quality. 1. Introduction Knotted wire fencing, despite being agriculturally ubiquitous, has a limited research literature. There are several aspects to the problem, including the manufacturing of the fencing, its erection, and its in-field use. The focus of the present paper is on the manufacturing, and the particular area under examination is the physical properties of wire. 2. Background Knotted wire fencing, which is differentiated from single strands, diamond (chain link), welded mesh, and hexagonal mesh (chicken mesh), is a rectangular knotted mesh that is used for livestock retention, for example, sheep and deer. The fencing is an integral feature of the stock farming landscape worldwide and serves its purpose for years and even decades totally exposed to the environment. It is such a common product as to be overlooked. Yet the fabrication of this product is a sophisticated task that requires specialist machines [1–4]. Modern machines are numerically controlled to permit different configurations, for example, sizes of the rectangular openings. There are other challenges too: the steel wire used for fences tends to have high tensile strength, and this makes it particularly difficult to form the knotted features, since plastic deformation is required. Consequently high localized forces are required to bend the wire, and the wire needs to have the necessary material properties to accommodate this without fracture. Breakages of wire inside the fence knotting machine is highly problematic from a production perspective, since the high speed of operation causes wire to be jammed and tangled in the