US20150233141A1

US20150233141A1 - Post

Info

Publication number: US20150233141A1
Application number: US14/415,663
Authority: US
Inventors: Brad Taylor; Mark White
Original assignee: OneSteel Wire Pty Ltd
Current assignee: OneSteel Wire Pty Ltd
Priority date: 2012-07-19
Filing date: 2013-07-19
Publication date: 2015-08-20
Also published as: NZ703257A; AU2013205197A1; WO2014012143A1; AU2013205197B2; CA2877887A1; CA2877887C

Abstract

A post that comprises at least one elongate flange with one or more spaced apertures therethrough is disclosed. A given one of the apertures is located and configured to be elongate, whereby a longitudinal axis of the given aperture is generally parallel to or aligned with an elongate axis of the flange. Configuration of the aperture, as presently disclosed, has surprisingly been shown to assist with the prevention of failure of the post at the aperture when a bending moment is applied to the post in a first instance. The post may be employed in applications such as fencing, demarcation, signage, retention, barricades etc.

Description

TECHNICAL FIELD

Disclosed herein is a post that comprises at least one elongate flange with one or more spaced apertures therethrough. A given one of the apertures is located and configured to be elongate, whereby a longitudinal axis of the given aperture is generally parallel to, or aligned with, an elongate axis of the flange. The post may be employed in applications such as fencing, demarcation, signage, retention, barricades etc.

BACKGROUND ART

Posts for use in applications such as fencing, demarcation, signage etc are known. Such posts are usually formed from steel, though in some applications it is known to mould posts from a plastic material (e.g. for use in electric fencing).
Steel fence posts have been known for many years that are roll-formed to have a Y-shaped or T-shaped profile (i.e. in end view). The post may take the form of a picket and, in this case, may be provided (e.g. cut) with a pointed end to facilitate post driving into the earth. Fence posts, especially those for use in e.g. rural applications, require a combination of strength (to enable the post to be driven into the earth) and ductility (so the post can deform without breaking when pressure is applied to it by e.g. livestock).
Such steel fence posts are usually provided with a series of spaced holes in a flange thereof (i.e. in the so-called “stalk” or “stem” of the post) to enable strands of fencing wire to be secured to the post, usually by tying each wire strand to the post with a separate short length of wire tie threaded through an individual hole, or by employing a wire “clip”. However, the wire can also be directly threaded through such holes. These holes are typically punched, cut, machined or drilled into an already roll-formed post in a separate step.
In addition (or as an alternative) to the series of holes, the posts can be provided with a series of spaced passages or notches that are usually cut or machined to project right into the stalk from a distal edge thereof. These passages enable a strand of fencing wire to be moved into and retained in the passage, thereby securing the wire directly to the post. An additional latch can be mounted to the post in the vicinity of the passage that allows the fencing wire strand to be moved therepast, and that retains the wire once located in the passage. Usually this latch is factory-fitted to the post in a separate stage.
Again, it has been observed that these passages are typically cut, punched, drilled or machined into an already roll-formed post in a separate step, adding additional manufacturing complexity and cost. In addition, the passages and the attachment of the latches can compromise the strength, integrity, corrosion resistance, etc of the stalk and thus of the entire post in use.
The holes and/or passages formed in the posts have typically been a weak point of the post, in-use. In this regard, when excessive pressure is applied to the post (e.g. by livestock) that results in a bending moment in the post, the post has been known to fracture at the holes and passages. When the post fractures, usually at the hole or passage closest to the ground, the post can no longer be used and must be replaced.
A number of techniques have been proposed to minimise the likelihood of fracture through the holes or passages. For example, moving the holes closer to a centreline of the post (i.e. further from a distal edge of the post flange in which the holes are formed) can assist with preventing fracture at the hole. However, having holes located further away from the flange distal edge results in manufacturing difficulties (i.e. the cutting, drilling or machining of the holes). In another example, the diameter of the holes may be reduced. However, this causes great difficulty in the threading of the wire or a clip through the hole. In another example, a post manufactured of a soft steel grade can be used. However, this compromises the initial bending strength of the post, which may result in the post bending as it is being driven into the ground.
Posts are known in the art with different types of apertures therethrough. For example, WO 2006/085182 discloses a clip for use with a trellis C-post. The clip is designed so that part of the clip can extend through an elongate aperture of the trellis C-post and be twisted (so that part of the clip is no longer aligned with the aperture), to secure the clip to the post. The aperture in this case is designed and provided for the clip.
Similarly, U.S. Pat. No. 1,214,749 discloses a clip for use with an L-post. The clip is designed so that part of the clip can extend through a slot of the L-post, and the entire clip is twisted so that the clip part that was previously aligned with the slot to allow its extension therethrough is no longer aligned with the slot, thus securing the clip and an associated wire to the L-post.
In another example, U.S. Pat. No. 1,826,182 discloses a wire clip for use with a T-post. The clip is designed so that the two ends of the elongate clip co-operate with two spaced and offset openings in the head of the ‘T’, with the wire placed intermediate the two openings and secured by the wire clip.
In yet a further example, GB 599,042 discloses a U-shaped clip for use with a T-post. The T-post has pairs of slots in the head of the ‘T’, whereby each slot, in each slot pair, receives a respective arm of the U-shaped clip to secure items thereto.
In each of these examples, the post apertures have solely been provided and adapted to allow a specific clip to be attached to the post, and not vice versa.
U.S. Pat. No. 6,488,268 discloses a breakaway support post for highway guardrail end treatments. The support post is in the form of an I-beam having two flanges separated by a web. The I-beam is designed so that when it is impacted by a vehicle at the guardrail (i.e. when the vehicle hits a single flange of the I-beam head-on), the I-beam will remain intact and redirect the vehicle back on to the road. The I-beam is also designed so that when it is impacted by a vehicle at the end of the guardrail (i.e. when the vehicle hits the I-beam side on and perpendicular to the web) the I-beam will buckle or yield. In this regard, the I-beam is considered to have a “strong” direction (i.e. perpendicular to the flange) which resists deformation, and a “weak” direction (i.e. perpendicular to the web) that buckles or yields. In U.S. Pat. No. 6,488,268, this weakening is achieved by removal of metal in the form of slots from the flanges of the I-beam.
The above references to the background art do not constitute an admission that the art forms a part of the common general knowledge of a person of ordinary skill in the art. The above references are also not intended to limit the application of the post disclosed herein.

SUMMARY OF THE DISCLOSURE

In a first aspect there is disclosed a post of a type that comprises at least one elongate flange with one or more spaced apertures therethrough. The flange may project out from, for example, a central longitudinal axis of the post. The post may have up to three (or more) elongate flanges that each project from the central longitudinal axis of the post, and may take the form of a Y- or T-post. The flange with the one or more spaced apertures therethrough may comprise a stalk or stem of the Y- or T-post (although other flanges of the post may instead be employed). The stalk is generally the major (or larger) of the flanges in a Y- or T-post, with the remaining (minor) flanges generally the so-called “wings”. Further, the post may take the form of a picket.
In accordance with the first aspect, a given aperture can be located and configured to be elongate. A longitudinal axis of the given aperture can be generally parallel to, or aligned with, the stalk elongate axis.
The given aperture is located in the stalk of the Y- or T-post. The stalk is generally the strongest member of the Y-post or T-post. This increased strength, with respect to the wings, is generally achieved by increasing the width (span) of the stalk relative to the remaining elongate flanges. The stalk is also generally orientated to be perpendicular to the fence plane. The apertures may preferably be placed in the stalk to enable threading of the fence wires unimpeded through the fence post, or for securing a wire or other attachment method, for example a tie or clip, via the same aperture. As the apertures of known posts are often the point of failure in the post (i.e. when a bending moment is applied thereto), locating the given aperture in the stalk also assists in strengthening the bending moment because, in use of the post, the bending moment often occurs in a direction that is planar to the flange having the apertures therein, and the stalk is generally thicker than the remaining flanges.
Reconfiguration of the aperture, as presently disclosed, has surprisingly been shown to assist with the prevention of failure of the post at the aperture when a bending moment is applied to the post in a first instance. It is understood that reconfiguration of the aperture (i.e. re-configuring away from a conventional circular hole to an elongate aperture) better allows the post to bend and deform, and prevents fracture of the post at the aperture in the first instance for a given deflection. It is also understood that the reconfigured elongate aperture is, in use, better able to resist propagation of micro-cracks at forward and trailing edges of the elongated aperture, when compared to a circular hole. This results in increased resistance to fracture of the post.
Furthermore, contrary to what might be expected with an elongating of the aperture, yield strength of the post is preserved, whilst ductility is increased. Again, this is understood to be a result of the better accommodation of stresses at the forward and trailing edges of the elongated aperture.
This can allow a post that has been deformed, which would otherwise have failed and needed to be replaced, to be re-bent (i.e. straightened) and thus re-used, thereby providing either a semi-permanent or temporary fix. The deformed post can be restraightened using known methods, and can provide for a significant saving of costs associated with otherwise having to replace fractured posts.
In contradistinction to the apertures disclosed in each of WO 2006/085182, U.S. Pat. No. 1,214,749 and U.S. Pat. No. 1,826,182, the re-configuring of the given aperture is particular and deliberate so as to be in a principal bending plane of the post elongate flange. In such a flange, a bending moment arises in a completely different manner to the moments that may arise in trellis posts, L-posts, the top flange of a T-post and circular posts. There is no teaching or recognition of bending moments or principal bending planes in any of WO 2006/085182, U.S. Pat. No. 1,214,749 or U.S. Pat. No. 1,826,182.
In addition, the removal of metal in the form of slots from the flanges of an I-beam, as taught in U.S. Pat. No. 6,488,268, is only to provide “strong” and “weak” directions of impact to the beam, and not to improve yield strength or increase ductility in comparison to pre-existing posts having apertures in a major flange thereof. U.S. Pat. No. 6,488,268 is silent on the resistance to fracture of the post. Further, the elongate apertures are not located in the major flange (i.e. the web) of the I-beam.
For example, the reconfiguring of the given aperture in the present disclosure can be designed in consideration of the principal bending plane of the flanges, and especially the stalk, of Y- and T-posts.
The reconfiguration of the aperture can also allow various steel grades to be utilised in the production of posts, which were previously not suitable. Fence posts require a combination of strength and ductility, which usually results in the sacrificing of one of these properties in preference for the other. With the reconfiguration of the aperture, it is now possible to use a higher grade steel (i.e. a steel grade having a higher carbon content, and is thus a less ductile steel that has a higher tensile strength) in the production of the post. Such higher grade steel can have greater resistance to bending and, even when bent, the post still does not tend to fail at the given aperture in the first instance for a given deflection. This allows the post to be re-bent and re-used.
In one embodiment, configuring of the given aperture to be elongate may enable one or more of the spaced apertures to be moved closer (e.g. from a centreline extending longitudinally through the stalk) to a distal edge of the stalk (i.e. closer to the stalk distal edge than the circular holes of a conventional post), without compromising the integrity of the post. This closer proximity to the distal edge can assist with simplifying securement of an elongate strand to the post. A conventional post having circular apertures located close to the stalk distal edge will generally fail more quickly than when the post has circular apertures that are located close to the post centreline (i.e. closer to the central axis from which the stalk and wings extend). However, configuring of the given aperture to be elongate can enable the given aperture to be located (shifted) closer to the stalk distal edge, and without prematurely causing post failure, than is achievable using known circular holes.
Similarly, and yet conversely to the embodiment described above, configuring of the given aperture to be elongate can enable the given aperture to be located closer to the central post axis (i.e. from which the wings and stalk extend), as the elongate aperture may be narrower than a conventional hole (i.e. the elongate aperture can be provided with or assume an effective transverse diameter that is less than that of a conventional circular hole). This may be useful to further improve the relative strength of the post.
When the stalk comprises a plurality of spaced apertures, reconfiguration of the given aperture can also enable the spaced apertures to be moved closer together than, for example, the holes in a conventional post (e.g. closer together along a longitudinal axis of the stalk). The inclusion of additional apertures, compared with a conventional post, may also be useful for fencing applications. It may provide a user with a variety of spacing options between wire strands, or enable additional wire strands to be incorporated into the fence. The closer spacing can also allow wire mesh/grid to be secured at multiple locations along the post.
In one embodiment, the given aperture may be located where the greatest bending moment occurs in the post in use. For circular holes of known conventional posts, the greatest bending moment tends to occur at one of a group of lowermost circular holes when the post is in use. When a bending moment is applied, the post will tend to fracture through one of these circular holes. By locating and configuring an elongate aperture at such a location, the stress through the given aperture can be reduced when compared to a conventional post. In one embodiment, the given aperture may therefore be one (or more) of a group of lowermost apertures in the stalk.
In one form, the group of lowermost apertures may be more closely spaced along the stalk longitudinal axis than a remainder of the apertures. This spacing can be used to assist with containing or excluding animals (e.g. rabbits and foxes) by enabling closely spaced wire strands closer to ground level, thereby helping to prevent the animal from being able to squeeze through otherwise wider gaps between strands.
When the stalk of the Y- or T-post comprises a plurality of apertures, the given aperture may be defined by one or more of the spaced apertures. In this regard, the given aperture may be considered to be a given “configured” aperture, while the spaced apertures that are not “given apertures” may each be considered to be a “non-configured” aperture. In the context of this disclosure, a “configured” aperture refers to an aperture that has been reconfigured in accordance with the teaching herein (i.e. to be elongate). A “non-configured” aperture may refer to an aperture that remains configured in a known manner such as, for example, a generally circular hole, or a notch in a distal edge of the stalk, of a conventional post. Further, the given apertures may be configured in the same or a different manner to each other.
In this regard, a post in accordance with the present disclosure may comprise only one configured/given aperture, with the remaining apertures being non-configured. Alternatively, a post in accordance with the present disclosure may comprise a number of apertures, for example ten apertures, two or three apertures of which may be configured/given, with the remaining apertures being non-configured. In a further alternative, a post in accordance with the present disclosure may comprise a number of apertures, for example ten apertures, that have each been configured in accordance with the teaching herein. Each of the ten apertures may have the same configuration, or they may have various different configurations. For example, some of the apertures may have the same configuration, for example five of the apertures may have the same configuration, and the remaining, for example five, apertures may each have a different configuration, but each of the ten apertures may be reconfigured in accordance with the teaching herein. It should also be appreciated that when the post comprises more than one configured/given aperture, the configured/given apertures need not be positioned adjacent to each other.
The apertures in the post, including any configured and/or non-configured apertures, may be spaced to correspond to the spacing of horizontal strands in a grid or mesh of the strands. Respective strands can be secured to respective apertures via, for example, a wire clip, thereby securing the grid to the post. The term “grid” is intended to include a wire mesh. Such a post allows a wire grid or mesh, having known or pre-existing spacings, to be quickly and easily secured to the post. In other words, the post may be preconfigured or pre-adapted to the wire grid or mesh. A single post may have a number of apertures along its length so that it can have a number of differently spaced wire grids or meshes secured thereto.
In a usual mode, the post is formed from a relatively non-deformable metal such as steel. The steel may optionally be galvanised or coated. Such coatings may be air dried, force cured or comprise thermal diffusion coatings.
In one embodiment, the given aperture may comprise a substantially straight leading edge, with reference to the distal edge of the stalk. The given aperture may further comprise top and bottom edges extending, from the leading edge, away from the stalk. At least one of the top and bottom edges may extend arcuately, for at least a portion thereof, from the leading edge. In this regard, a portion of the top or bottom edge may be straight and a portion of the top or bottom edge, connecting to the leading edge, may be curved. Alternatively, the top and/or bottom edges may each form a semi-circle. The top and bottom edges may extend to a substantially straight trailing edge. The elongate aperture may therefore be in the form of a rounded rectangle (i.e. a rectangle having rounded corners) or an obround (i.e. semi-circular top and bottom edges, with substantially parallel leading and trailing edges).
According to a second aspect, a method of improving or increasing the ductility of a Y- or T-post is disclosed. The Y- or T-post may be of the type that comprises at least one elongate stalk having an elongate axis. The stalk may comprise one or more spaced apertures therethrough. The apertures may be arranged along the stalk with respect to the elongate axis thereof. The method may comprise locating and configuring a given aperture in the stalk to be elongate, whereby a longitudinal axis of the given aperture is generally parallel or aligned with the stalk elongate axis.
Such location and elongate configuring of the given aperture has been observed to improve or increase the ductility of a Y- or T-post in comparison to a conventional Y- or T-post having circular holes therethrough.
The Y- or T-post may otherwise be as disclosed in the first aspect.
The posts as disclosed herein may be used in applications such as fencing, demarcation, signage, etc. The apertures may enable elongate strands (e.g. wire strands) to be secured to the post by either directly threading a strand through a given aperture, or by tying each strand to the post with a separate short length of wire tie threaded through an individual aperture, or by employing a wire “clip”. Reconfiguration of the, or each, aperture can also allow known clips or other methods for securing an elongate strand to a post to be employed. The term “strand” as used herein is to be broadly interpreted to include various elongate components that can be secured to a post, including fence post wire, grid and mesh.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the post as set forth in the Summary, specific post embodiments, conventional post examples and FEA post models will now be described, by way of example only, and with reference to the accompanying drawings in which:

FIG. 1 shows a representative top view of the various posts described herein;

FIG. 2 shows a side view of a first post embodiment having a series of vertically aligned and spaced slots having a maximum dimension of 5.5 mm×12 mm in a stalk (major flange) thereof, each slot having semi-circular top and bottom edges;

FIG. 3 shows a side view of a second post embodiment having a series of vertically aligned and spaced slots having a maximum dimension of 5.5 mm×9.5 mm in a stalk thereof, each slot having semi-circular top and bottom edges;

FIG. 4 shows a side view of a conventional post example having a series of vertically aligned and spaced 8 mm diameter circular holes in a stalk thereof;

FIG. 5 shows a graph of the fail angle of the first and second post embodiments and the conventional post example, as a function of the distance of the aperture from the stalk distal edge, for EY60 grade posts;

FIG. 6 shows a graph of the fail angle of the first and second post embodiments and the conventional post example, as a function of the distance of the aperture from the stalk distal edge, for ER41 grade posts;

FIG. 7 shows a graph of the number of re-bends before failure of the first and second post embodiments and the conventional post example, as a function of the distance of the aperture from the stalk distal edge, for EY60 grade posts;

FIG. 8 shows a graph of the number of re-bends before failure of the first and second post embodiments and the conventional post example, as a function of the distance of the aperture from the stalk distal edge, for ER41 grade posts;

FIG. 9 shows a graph of the yield strength of the first and second post embodiments and the conventional post example, as a function of the distance of the aperture from the stalk distal edge, for EY60 grade posts;

FIG. 10 shows a graph of the yield strength of the first and second post embodiments and the conventional post example, as a function of the distance of the aperture from the stalk distal edge, for ER41 grade posts;

FIG. 11 shows a finite element analysis (FEA) model of the resultant stress in the a conventional post with a 5.5 mm diameter round hole when a 100N load is applied at the top of the post in the direction shown;

FIG. 12 shows an FEA model of the resultant stress in the first post embodiment of FIG. 2 when a 100N load is applied at the top of the post in the direction shown; and

FIG. 13 shows an FEA model of the resultant stress in the second post embodiment of FIG. 3 when a 100N load is applied at the top of the post in the direction shown.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Various embodiments of a post that enables securement of at least one strand thereto will now be described with reference to FIGS. 1 to 3. Comparative post examples for a conventional post, as shown and described in FIG. 4, are also provided. Finite element analysis (FEA) post models are shown and described in each of FIGS. 11 to 13. These models illustrate similar aperture and hole configurations to those posts shown in FIGS. 2 to 4.
Whilst the post will generally be described in relation to the securing of wire strands (e.g. of fence wire) to a fence post, it should be understood that the post is not limited to fencing-related applications. Further, whilst each of the post embodiments and conventional post examples described is of a type that comprises three elongate flanges that each project out from a longitudinal central axis of the post to generally take the form of a Y-post, it should be understood that the post embodiments may have more or less flanges, and may also take the form of a T-post. Further, the flange in which the apertures are typically formed comprises a stalk (i.e. stem or major flange) of the post, however, other flanges of the post may employ one or more reconfigured apertures in the bending plane thereof. Finally, it should be understood that each of the post embodiments may take the form of a picket (i.e. with a pointed lower end) for ease of post driving into the ground in fencing and related applications, but is not so limited.
Referring firstly to FIG. 1, a top view of a Y-post, generally designated 10, is shown. Such a Y-post 10 comprises a major flange in the form of a stalk 12. Stalk 12 extends from a longitudinal central axis 13 of the post 10 and has an elongate distal edge 14. Minor flanges in the form of wings 15 also extend from the longitudinal central axis 13 of the post to form a Y-shape in profile, as shown in FIG. 1, hence the name “Y-post”. The Y-post 10 may, for example, be used as a fence post and, in this regard, may have the form of a picket wherein the lower end, or base, is cut or machined to be pointed.
Referring now to FIGS. 2 and 3, side schematic views of first and second post embodiments are shown in the form of elongate Y- posts 20 and 30, respectively. The Y- posts 20, 30 are generally as has been described in relation to FIG. 1.
In the first post embodiment, FIG. 2, the Y-post 20 is shown having apertures, in the form of slots 25. Slots 25 have a maximum dimension of 5.5 mm wide and 12 mm long. Slots 25 have straight leading edges 27 and straight trailing edges 28, with semi-circular top and bottom edges 29, thus forming an obround. The leading and trailing edges 27, 28 are substantially parallel to the stalk distal edge 14. The leading and trailing edges 27, 28, and also a central elongate axis of each slot 25, are either parallel to a central elongate axis of the stalk 12, or may align with that stalk axis, depending on where each slot is chosen to be located. Whilst the leading edges 27 are shown as being spaced 12 mm from the stalk distal edge 14, they may be spaced closer to, or further from, the stalk distal edge 14 (as will be described in the experimental results, below).
In the second post embodiment, FIG. 3, the Y-post 30 is shown having apertures, in the form of slots 35. Slots 35 have a maximum dimension of 5.5 mm wide and 9.5 mm long, and are thus more squat than the apertures 25 shown in the first post embodiment. Slots 35 have straight leading edges 37 and straight trailing edges 38, with semi-circular top and bottom edges 39, thus again forming an obround. The leading and trailing edges 37, 38 are substantially parallel to the stalk distal edge 14. Again, the leading and trailing edges 37, 38, and also a central elongate axis of each slot 35, are either parallel to a central elongate axis of the stalk 12, or may align with that stalk axis, again depending on where each slot is chosen to be located. Leading edges 37 are again shown as being spaced 12 mm from the stalk distal edge 14, although they can be positioned closer to, or further from, the distal edge.
Referring now to FIG. 4, a conventional elongate Y-post example 40 is shown. The Y-post 40 is generally as described in relation to FIG. 1. The Y-post 40 shown in FIG. 4 is considered ‘conventional’ in that it comprises generally circular holes 47 spaced out along the stalk 12. Each hole 47 has a diameter of 8 mm, which can be considered to be a “conventional hole shape”, and which is spaced 12 mm from the stalk distal edge 14.

Experimental & Comparative Results

Bending and ductility tests were performed on the first and second fence post embodiments 20, 30, with each post embodiment formed from two different steel grades, EY60 (a high-carbon steel having a nominal carbon equivalence (CE) of 0.55%) and ER41 (a medium-carbon steel having a nominal carbon equivalence (CE) of 0.48%). The EY60 grade post, due to the higher carbon content, was noted to generally be a stronger but less ductile post, whilst the ER41 grade post, due to the lower carbon content, was noted to balance the strength and ductility properties of the post. Each fence post 20, 30 was 180 cm long and had three of the respective apertures (slots) 25, 35 formed into the stalk of each respective post. The apertures 25, 35 were formed such that the centre points of adjacent apertures were approximately 2 inches apart.
Testing of the fence post was performed to represent the fence post in-use. In this regard, a lower part of the fence post (i.e. that part of the fence post that would be located in the ground in-use) was anchored in a fixed position in the test apparatus.
The location of the apertures 25, 35, with reference to the stalk distal edge 14, was varied, to observe its effect on the bending and ductility properties of the post. Apertures 25 were formed as obrounds having a maximum dimension of 5.5 mm wide and 12 mm long. Apertures 35 were formed as more squat obrounds, having a maximum dimension of 5.5 mm wide and 9.5 mm long.
In order to compare the results of the post embodiments, bending and ductility tests were also performed on the conventional fence post example 40 having generally circular 8 mm diameter holes 47. The conventional fence post example was also tested using the same steel grades as the post embodiments, with the aperture shape being the primary point of distinction therebetween. The area (i.e. amount) of steel removed for 8 mm round holes 47 was intermediate the area of steel removed for slots 25 and 35 (i.e. slot 25 had the most amount of steel removed during forming, followed by hole 47 and slot 35). The location of the holes 47, with reference to the stalk distal edge 14, was varied to again observe the effect on the bending and ductility properties of the conventional post example.
Ductility tests were performed by placing a post 20, 30, 40, of each steel grade into a bending rig, with the lowermost hole 25′, 35′, 47′, spaced a pre-determined distance (e.g. 50 mm) above a fixed position (i.e. where the post was anchored in the test apparatus). The post 20, 30, 40, was then bent parallel to the stalk 12 until crack propagation occurred. The failure angle was taken to be the deviation from the vertical, to the start of the curvature of the bending, when the crack propagation occurred. This was performed on both steel grades, with the location of the apertures 25, 35, 47, with respect to the stalk distal edge 14, being varied. Specifically, the apertures 25 and 35 of posts 20 and 30, respectively, were positioned 8 mm, 13 mm, 16 mm and 19 mm from the stalk distal edge in different experimental posts.
The results of the average of ten posts for each type (i.e. ten samples of EY60 grade post 20 with aperture 25 distanced 8 mm from the stalk distal edge 14, ten samples of EY60 grade post 20 with aperture 25 distanced 13 mm from the stalk distal edge 14, ten samples of EY60 grade post 20 with aperture 25 distanced 16 mm from the stalk distal edge 14, ten samples of EY60 grade post 20 with aperture 25 distanced 19 mm from the stalk distal edge 14, ten samples of ER41 grade post 20 with aperture 25 distanced 8 mm from the stalk distal edge 14, etc) are shown graphically in FIGS. 5 and 6.
As each post was being bent, the yield stress was also measured. The results of the average of ten posts for each type are shown graphically in FIGS. 7 and 8.
Bending tests were also performed by placing a post 20, 30, 40, of each steel grade, with the various spacings of the apertures and holes from the stalk distal edge, into a bending rig, with the lowermost aperture 25′, 35′ and hole 47′ being spaced a pre-determined distance (e.g. 50 mm) above a fixed position. The post 20, 30, 40 was then bent to a 30° angle, from the vertical, and the number of re-bends was assessed as the number of times the post could be re-straightened, re-bent, re-straightened, etc.
For both the EY60 and ER41 grade post embodiments and for the conventional post example, as can be seen in FIGS. 5 and 6, moving the slot and hole further away from the stalk distal edge resulted in a higher average angle of failure (i.e. the angle to which the post can be bent before it fails). However, the average angle of failure of the conventional post example was notably lower than both of the post embodiments 20 and 30 (i.e. the more elongate and more squat obrounds, 25, 35, respectively).
It was also noted that the EY60 grade post embodiments had a lower average angle of failure than the ER41 grade post embodiments, for apertures located closer to the distal edge. This was expected, given that the ER41 grade steel is more ductile (e.g. softer) than the EY60 grade steel. Again, it was noted that as the aperture was moved further away from the stalk distal edge, there was more material to deform, thus the average angle of failure resulting from aperture reconfiguration was more reliably able to be compared.
In addition to the failure angle, reference is now made to FIGS. 7 and 8, which show the number of re-bends for the various shaped apertures and conventional hole for EY60 and ER41 grade posts, as a function of the distance of the aperture or hole from the stalk distal edge. It can be clearly seen that, for both steel grades, the elongate apertures allow for the post to be re-bent at least once, whereas the posts with conventional circular holes do not. This surprising result therefore allows a user (e.g. a farmer) to provide a fix, or at least a temporary fix, to a fence. For example, if a conventional post example were used in a fence, the post would more likely need to be replaced, due to the likely failure of the post (and thus its inability to be re-bent). However, use of the reconfigured post embodiments, as disclosed herein, was noted to allow the post to be restraightened and used temporarily until the post was replaced at a later time, convenient to the user (e.g. farmer). As expected, the ER41 grade posts were able to be re-bent more times than the corresponding EY60 grade posts, due to the more ductile nature of the steel grade.
The distance of the aperture from the stalk distal edge also proved to be more significant in the EY60 steel grade posts, which was again expected due to the additional amount of stronger material between the stalk distal edge and the aperture, allowing more deformation of the post and for the post to be re-bent.
As seen in FIGS. 9 and 10 the EY60 grade post embodiments provided a more significant increase in yield strength over the EY60 grade conventional post example, and greater than the ER41 grade post embodiments and conventional post example. This improvement became less pronounced when the apertures and holes were moved further from the stalk distal edge. Here, the greater bulk of flange material came into play influencing yield strength.
The EY60 grade post embodiments 20, 30 (i.e. those having elongate apertures), as described above, were able to act in a more ductile manner than an EY60 grade conventional post example 40 (i.e. one having circular holes). This increased/improved ductility allowed the posts to be re-used or re-bent to form a temporary fix. Not having to immediately replace bent posts was observed to provide a significant advantage for post users, such as farmers.

FEA Analysis

Finite element analysis models, see FIGS. 11 to 13, were created to illustrate similar aperture and hole configurations to those shown in FIGS. 2 to 4. The FEA modelling data was noted to be limited, in that there were a number of factors which were not able to be accounted for. For example, the FEA models did not account for cold-working in the material which would occur during the forming of each elongate aperture or circular hole. Further, the FEA models did not account for inconsistencies in the composition of the post. As such, the FEA modelling isolated the shape and/or location of the aperture or hole to provide an indication as to stress concentrations occurring at the apertures or holes.
Whilst the FEA post models are generally described in relation to the securing of wire strands to a fence post, it should be understood that such posts are not limited to fencing-related applications. Further, whilst each of the FEA post models described is of a type that comprises three elongate flanges that each project out from a longitudinal central axis of the post to generally take the form of a Y-post (such as Y-Post 10 shown in FIG. 1), it should be understood that the FEA post models may be modified to enable analysis of posts with more or less flanges, and for posts that take the form of a T-post. Further, the models assume the flange in which the apertures are typically formed comprises a stalk (i.e. stem or major flange) of the post, however, it was noted that other flanges of the post can be modelled. Finally, it should be understood that each of the FEA post models assume that the post will take the form of a picket (i.e. with a pointed lower end) for ease of post driving into the ground in fencing and related applications, but the models are not so limited.
The finite element analysis modelling, for each of the post models, was performed on a 1.1 m long post section. The base of the post was fully restrained (i.e. 0 degrees of freedom) and a load of 100N was applied at the top of the post section in a lateral direction, such that the stalk distal edge was placed into tension. While each of the following FEA post models were modelled on the basis of the stalk distal edge being in tension, due to the application of the load, it should be appreciated that the bending moment may be applied from another direction (i.e. the bending moment may be applied from the other side of the post), which can result in the stalk distal edge being in compression.
Each post was modelled on plain carbon steel (i.e. mild steel having 0.16-0.29% carbon). Additionally, the lowermost aperture on each post was located 50 mm from the base of the post. This was to separate the first aperture from anomaly stresses occurring due to constraining of the post base. In the model, subsequent apertures (i.e. vertically above) were separated by a spacing of 37.5 mm. While the spacing between apertures remained consistent for the purposes of the FEA modelling, it was noted that the spacings could be modified to correspond to known or pre-existing spacings employed for wires or wire mesh/grid in the fencing industry (e.g. in agricultural applications). Further, the spacing between apertures did not need to be consistent for the length of the post. For example, the model could be run with the lower apertures being more closely spaced than the upper apertures. Such closer spacing was noted to be suitable when arranging more densely spaced wire (e.g. for more densely spaced wire or mesh, such as to fence-off for small creatures such as vermin and pests; rabbits, foxes, etc). While the configuration of each aperture for a given post embodiment was the same, for the purposes of the FEA modelling, it was noted that each aperture could be configured in a different manner (i.e. each aperture having a different shape), or a number of apertures could be configured in one manner and the remaining apertures could be configured in a different manner.

FEA Post Models

An FEA model is shown in FIG. 11, based on a conventional elongate Y-post, such as the one shown in FIG. 4. The Y-post 60 is considered ‘conventional’ in that it comprises a generally circular hole 68. The hole 68, at its closest point to the stalk distal edge, is a distance of 12 mm from the stalk distal edge 14. In the FEA model shown in FIG. 11, each hole 68 has a diameter of 5.5 mm, which may be considered as an “optimal standard hole shape”. In this regard, the “optimal standard hole shape” is optimised to provide a best case scenario for conventional posts. Specifically, the hole 68 has been reduced in size as compared to currently available commercial Y-posts (typically having a hole diameter of 8 mm and spaced approximately 8-14 mm from the stalk distal edge). Reducing the size of the hole 68 can reduce the effects that the hole 68 will have on the failure mechanisms of the Y-post 60.
In FIG. 11, the stresses resulting from a 100N load being applied in a lateral direction are shown in an FEA model. Regions of high stress are depicted as vertical hatchings, while heavy horizontal hatchings indicate a relatively low stress.
Referring now to FIGS. 12 and 13, side views of second and third FEA models are shown generally in the form of elongate Y- posts 20 and 30, as shown in FIGS. 2 and 3. Again, the Y- posts 20, 30 are as described in relation to FIG. 1.
In FIG. 12, apertures are shown in the form of obrounds 25. The obrounds 25 have a maximum dimension of 5.5 mm wide and 12 mm long, with semi-circular top and bottom edges 29. The leading edges 27 are spaced 12 mm from the stalk distal edge 14.
In FIG. 13, apertures are shown in the form of obrounds 35. The obrounds 35 have a maximum dimension of 5.5 mm wide and 9.5 mm long, with semi-circular top and bottom edges 39. The leading edges 37 are spaced 12 mm from the stalk distal edge 14.

Analysis of the FEA Post Models

The FEA modelling was performed to provide comparative and supporting data to that of the experimental results. Given that a number of influential material parameters were not accounted for in the FEA modelling, the above results were used merely to assist with a review of stress concentrations occurring at the aperture edge closest to the stalk distal edge.
The FEA models showed the effect of changing (reconfiguring) the aperture shape on the maximum resultant stress at the aperture. The FEA models also showed the effect of changing the width to length ratio of the aperture on the maximum resultant stress at the aperture. Specifically, the FEA models show a reduction of stress at the lowermost elongate aperture 25′, 35′, when compared to the lowermost circular hole 68′ of the conventional post 60. The FEA models also show that the more squat aperture 35′ has a higher stress concentration than aperture 25′. The second lowermost aperture 25″, 35″ is also shown to have a reduced stress, when compared to the second lowermost hole 68″ of the conventional post 60. The more squat aperture 35″ again has a higher stress concentration than aperture 25″.
From the FEA modelling it was understood that the reconfigured apertures were better able to resist the propagation of micro-cracks at the lateral (side) edges of the elongated aperture in comparison to a circular hole, where the stress is concentrated at an “equatorial” point at opposing sides of the hole. The redistribution of stresses along the side edges of the elongated aperture resulted in increased resistance to fracture of the major flange (stalk) and thus the post as a whole.
It was noted that this outcome was contrary to what might be expected when a circular hole is replaced with an elongated aperture such as a slot. Not only was yield strength of the post discovered to have been preserved, but post ductility was also increased. Again, it was understood that the mechanism for this arose from the better accommodation of stresses at the side edges of the elongated aperture (slot).
Whilst a number of specific post embodiments have been described, it should be appreciated that the post may be embodied in many other forms. For example, the aperture elongation may be more pronounced, or the aperture widened or narrowed, or the radius to top and bottom edge curvatures changed.
The strand to be attached to the post may include various elongate components such as rod, bar, etc. Whilst a usual application of the post is in fencing, to secure wire strands or mesh/grid to a post, the post can be employed in other applications such as demarcation, signage, retention, barricades etc. In this regard, a device may be used that enables barriers, signage (e.g. of a core-flute design), etc to be secured to the post.
In the claims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” and variations such as “comprises” or “comprising” are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the post and method as disclosed herein.

Claims

1-15. (canceled)

16. A Y- or T-post, being of a type that comprises a major flange that defines a stalk in the Y- or T-post, and remaining flanges that define wings in the Y- or T-post, the stalk having an elongate axis, the stalk comprising one or more spaced apertures therethrough that are arranged along the stalk with respect to the elongate axis, with a given aperture being located and configured to be elongate, whereby a longitudinal axis of the given aperture is generally parallel to or aligned with the stalk elongate axis.

17. A post as claimed in claim 16 wherein the given aperture is located where the greatest bending moment occurs in the post in use.

18. A post as claimed in claim 16 wherein, in use, the given aperture is at least one of a group of lowermost apertures in the stalk.

19. A post as claimed in claim 18 wherein, in use, the group of lowermost apertures, comprising at least one given aperture, are more closely spaced along the longitudinal axis than a remainder of the apertures.

20. A post as claimed in claim 16 wherein, when the post is inserted into ground, in-use, the given aperture is the lowermost aperture at or above the ground.

21. A post as claimed in claim 16 wherein, when the post comprises a plurality of spaced apertures, the given aperture comprises one or more of the spaced apertures.

22. A post as claimed in claim 21 wherein each given aperture may be configured in the same, or a different, manner.

23. A post as claimed in claim 16 wherein the given aperture comprises a substantially straight leading edge, with reference to a distal edge of the stalk.

24. A post as claimed in claim 24 wherein the given aperture comprises top and bottom edges extending, from the leading edge, away from the stalk distal edge.

25. A post as claimed in claim 24 wherein at least one of the top and bottom edges extends arcuately, for at least a portion thereof, from the leading edge.

26. A post as claimed in claim 25 wherein the top and bottom edges extend to a substantially straight trailing edge.

27. A post as claimed in claim 26 wherein at least one of the top and bottom edges forms a semi-circle between the leading and trailing edges.

28. A post as claimed in claim 16 wherein the post is formed from steel.

29. A method of improving the ductility of a Y- or T-post being of a type that comprises a major flange that defines a stalk in the Y- or T-post, and remaining flanges that define wings in the Y- or T-post, the stalk having an elongate axis, the stalk comprising one or more spaced apertures therethrough that are arranged along the stalk with respect to the elongate axis, the method comprising locating and configuring a given aperture in the stalk to be elongate, whereby a longitudinal axis of the given aperture is generally parallel to or aligned with the stalk elongate axis.

30. A method as claimed in claim 29 wherein the given aperture is located where the greatest bending moment occurs in the post in use.