Patent Description:
Due to increasing societal and political demands for decarbonisation, lightweight construction is a constant concern in machinery structures. Although railway vehicles already provide significant environmental benefits compared to other modes of vehicular transport, structural weight reduction remains an important issue. Lightweight aluminium alloy bogie frames have been proposed to reduce the weight of railway vehicles. However, these structures either contain welded joints or consist of a single casting, which both lead to disadvantages in terms of strength and reliability of the bogie frame. The document <CIT> describes alternative lightweight bogie frames comprising a plurality of beams made of a fiber reinforced resin composite material.

The use of bolted joints in a bogie frame provides a number of advantages compared to e.g. welded joints. For example, a bolted joint avoids subjecting the bogie frame to residual stresses that may be caused by a welded joint. Also a bolted joint can be easily repaired or replaced. Therefore, the reliability and repairability of the bogie frame can be improved. Such a bogie frame with bolted joints is described in <CIT>.

Typically, a given bolted joint will include more than one bolt to provide redundancy and spread loads. Therefore, the loosening or failure of a single bolt does not immediately correspond to failure of the whole joint. However, it can be difficult to determine when a bolt has partially or even completely failed if the joint is maintained by the remaining bolt(s), albeit in a weakened arrangement. Essentially, if the loosened or failed bolt is not retightened, repaired or replaced, the load on the remaining bolt(s) is increased and the integrity of the joint as a whole can be compromised.

It would be desirable to provide a way of addressing these issues.

According to a first aspect of the present invention, there is provided a bogie frame for a railway vehicle, the bogie frame comprising structural members defining the frame, and one or more reinforcing components joining the structural members, the or each reinforcing component comprising:.

In normal operation, the/each fastening bolt and the/each reinforcing component forming the joint between the first and second structural members supports a respective load across the structural members. When a bolt fails, its load transfers to any remaining bolts and to the one or more of the reinforcing components. This load transfer can increase the load across a particular reinforcing component to such an extent that the reinforcing component accumulates damage. However, this damage accumulation will tend to be focused in the first and/or second end portions of the first fibre-reinforced plastic layer as they are weaker than the central portion. Moreover, because the end portions are transparent or translucent, this damage, which is typically in the form of cracks, can be visually identified on inspection of the reinforcing component. In this way, the joint between the first and second structural members can be monitored for partial or complete failure of one or more of the fastening bolts, even while the joint as a whole remains intact, i.e. capable of transmitting loads between the first and second structural members. Partial bolt failure may include loosening and/or plastic deformation of a bolt. Complete bolt failure may include rupture of a bolt into separate parts.

Thus signs of damage in the first and/or second end portions can give an early indication of bolt failure, providing an opportunity to tighten, repair or replace the failed bolt before subsequent failure of any remaining bolts or rupture of the reinforcing component occurs. Therefore, the reliability and safety of the joint can be improved.

The first fibre-reinforced plastic layer may be made of a glass-fibre-reinforced plastic (GFRP), for example, a glass-fibre-reinforced epoxy resin.

The second fibre-reinforced plastic layer may be made of a carbon-fibre-reinforced plastic (CFRP), for example, a carbon-fibre-reinforced epoxy resin.

The/each reinforcing component may extend between the first and second end portions in a direction which is parallel to that of the one or more fastening bolts which join the first and second structural members.

The bogie frame may comprise a plurality of reinforcing components joining the first and second structural members. The plurality of reinforcing components may be spaced (e.g. at regular intervals) in a row along a line of the joint between the first and second structural members. In this configuration, the plurality of reinforcing components can provide a visual indication of how bolt failure is causing the joint to open by the relative amounts, along the row, of damage accumulation in the first and/or second end portions.

Additionally, or alternatively, when the structural members of the bogie frame are joined by a plurality of fastening bolts, the plurality of reinforcing components may be positioned to assist with identification of a failed fastening bolt. More particularly, when a fastening bolt fails, a greater load will generally be transferred to the reinforcing component which is nearest to the failed bolt. Therefore, damage accumulation is more likely to occur in that reinforcing component.

The plurality of reinforcing components may have different mechanical properties, e.g. different strengths. For example, a higher strength reinforcing component may be located at a position where the load transmission between the first and second structural members is greater.

The plurality of reinforcing components may be configured such that each reinforcing component is adjacent to and aligned with a different respective fastening bolt. For example, each reinforcing component may be located to minimise a separation between the reinforcing component and its fastening. In this configuration, damage accumulation in the first and/or second end portion of a given reinforcing component may be an indication of failure of its fastening bolt.

Generally, the first and the second end portions are equal in size. However, the/each reinforcing component may be asymmetric, e.g. the first end portion may be smaller than the second end portion.

For example, the first end portion may extend a shorter distance from the central portion than the second end portion. In this configuration, load distribution in the reinforcing component can be such that damage accumulation in the first end portion is more concentrated and therefore easier to visualise than damage accumulation in the second end portion. Conveniently, the first end portion may be located at a more accessible location on the bogie frame, e.g. a location closer to an outer side of the bogie frame, than the second end portion.

The first and second end portions may be adhesively bonded to the first and second structural members, respectively. For example, a structural adhesive such as epoxy, acrylic or urethane may be used to form an adhesive bond. Compared to other fixings, such as mechanical fixings, adhesive bonds are generally lighter and reduce stress concentrations.

The/each reinforcing component is typically formed as a strip, for example in which the first fibre-reinforced plastic layer provides a planar substrate and the second fibre-reinforced plastic layer is bonded to one side of the planar substrate.

The first and/or the second end portion may be divided into a plurality of fingers which attach to the respective structural member. For example, the plurality of fingers may extend in a direction which is parallel to that of the one or more fastening bolts which join the first and second structural members.

The plurality of fingers may be spaced (e.g. at regular intervals) in a row along a line of the joint between the first and second structural members. In this configuration, the plurality of fingers can provide a visual indication of how bolt failure is causing the joint to open by the relative amounts, along the row, of damage accumulation in the fingers.

Additionally, or alternatively, when the structural members of the bogie frame are joined by a plurality of fastening bolts, the plurality of fingers may be positioned to assist with identification of a failed fastening bolt. More particularly, when a fastening bolt fails, a greater load will generally be transferred to the finger nearest to the failed bolt. Therefore, damage is more likely to occur in that finger.

The plurality of fingers of the/each end portion may be separately attached to the respective structural elements. For example, the plurality of fingers may have distinct and separate adhesive bonds with the respective structural member. In this way, interfacial failure of the bond of one of the fingers (e.g. a delamination crack) is less likely to extend into another bond of an adjacent finger leading to similar failure of the other bond.

The/each reinforcing component may further comprise one or more sensors configured to monitor strain in the first and/or second end portions. For example, the one or more sensors can be located at a relatively inaccessible location on the bogie frame, e.g. on one of the first and second end portions which is located further from an outer side of the bogie frame than the other end portion.

When the first and/or the second end portion is divided into a plurality of fingers which attach to the respective structural member, the one or more sensors may be configured to monitor strain in each finger separately. Therefore, the sensors may monitor the type or direction of the load causing the failure of a fastening bolt and/or which fastening bolt has failed.

The/each reinforcing component may further comprise a removable cover configured to protect an exposed surface of one of the first and second end portions. In this way, superficial damage to the exposed surface (e.g. by scratching), or dirt accumulation on the exposed surface, may not hamper the visual identification of damage accumulation in the/each end portion. Conveniently, both end portions may be protected by respective removable covers.

When the first and/or second end portion comprises the plurality of fingers, each of the fingers may further comprise respective removable covers each configured to protect an exposed surface of its finger.

The first structural member may be one of a pair of side members of the bogie frame, e.g. the side members may extend in a longitudinal direction of the railway vehicle. Conveniently, the side members may be extrusions, e.g. made of an aluminium alloy. The extrusion direction may be along the longitudinal direction.

The second structural member may be a centre member which extends between the pair of side members, e.g. the centre member may extend between the side members in a transverse direction of the railway vehicle, perpendicular to its longitudinal direction. The centre member may be a metal casting, e.g. an iron-based casting or an aluminium alloy casting.

According to a second aspect of the present invention, there is provided a method of monitoring the health of the bogie frame according to the first aspect, the method including:.

As mentioned above, joint deterioration can be caused by failure of at least one of the fastening bolts. Thus the method may further include identifying a partially or completely failed fastening bolt as the cause of joint deterioration.

When the reinforcing component comprises the removable cover(s), the inspection step may include removing the/each removable cover from the/each end portion or from one or more of the plurality of fingers.

When the first and/or second end portion comprises the plurality of fingers, the inspection step may include comparing amounts of any damage to respective fingers.

Additionally, or alternatively, when the bogie frame comprises a plurality of reinforcing components, the inspection step may include comparing amounts of any damage to respective end portions of the components.

Further background to the present invention, and aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures.

<FIG> shows a schematic side-view of a railway vehicle <NUM> including a bogie <NUM>. The bogie <NUM> is positioned underneath the railway vehicle <NUM> over the track <NUM>. The bogie <NUM> comprises a bogie frame <NUM>, <NUM>' for supporting the railway vehicle <NUM>. The bogie frame <NUM>, <NUM>' is coupled to a set of wheels <NUM> via respective axles (not shown).

Usually, two bogies (not shown) are fitted to each car body <NUM> of the railway vehicle <NUM>, one near each end of the car body <NUM>. However, the bogie <NUM> may be disposed between adjacent car bodies <NUM>. The bogie <NUM> is important for providing stability to the railway vehicle <NUM> by absorbing strong vibrations and high centrifugal forces, particularly on curved sections of the track <NUM>.

<FIG> shows an example of a bogie frame <NUM>' in a perspective view. The depicted bogie frame <NUM>' comprises two side members <NUM> and a centre member <NUM>. The depicted straight side members <NUM> include extruded profiles 14a made of an aluminium alloy. Preferably, the aluminium alloy may be an aluminium alloy of the 6xxx series. The extrusion direction of the extruded profiles 14a is arranged in a longitudinal direction L of the railway vehicle <NUM> when the bogie frame <NUM>' is mounted thereto.

The depicted centre member <NUM> comprises a cast element <NUM> being a cast multi-chamber element <NUM> which may be made from metal casting. In the depicted examples of the centre member <NUM> shown in <FIG>, the entire centre member <NUM> is a cast element <NUM> being a multi-chamber element <NUM>. However, it may also be possible that only a part of the centre member <NUM> consists of a cast multi-chamber element <NUM> and further parts thereof may have other designs.

For example, the cast material of the multi-chamber element <NUM> may be iron-based or aluminium alloy. Preferably, the cast material may be an aluminium alloy. The depicted centre member <NUM> has an opening 18c in a top view, which is arranged symmetrically to a longitudinal axis of the centre member <NUM>. By arranging the opening 18c as shown in <FIG>, the centre member <NUM> comprises two facing cross beams which are connected to each other at the sides of the centre member <NUM> adjacent to the extruded profiles 14a. This may allow for a uniform distribution of the lateral loads to be absorbed by the bogie frame <NUM>'.

In the upper surface 18a of the cast multi-chamber element <NUM> there are provided two recesses 18d for receiving first strengtheners <NUM>, the bottom 18da of which lies in a plane parallel to the upper surface 18a. The insertion of the first strengtheners <NUM> into the recesses 18d will be described later in connection with <FIG>.

<FIG> shows an enlarged section of the bogie frame <NUM>' depicted in <FIG> illustrating an example of a bolt connection <NUM> between the side members <NUM> and the centre member <NUM>. In particular, <FIG> depicts two contact surfaces <NUM> at which the side member <NUM> is jointed to the centre member <NUM>. The depicted side member <NUM> is connected to the centre member <NUM> at the contact surfaces <NUM> by means of the bolt connection <NUM>.

<FIG> shows the centre member <NUM> of the bogie frame <NUM>' of <FIG> in a front view and the extruded profiles 14a of the side members <NUM> in a section view along the line A-A depicted in <FIG>. In this view, the plurality of chambers included in the multi-chamber element <NUM> is clearly visible. It can be seen that the chambers are formed, e.g., by ribs 18cb, 18cc disposed perpendicularly and parallel to the upper and lower surfaces 18a, 18b of the multi-chamber element <NUM>. In addition, two inclined ribs 18ca are visible, which form a transition to the short side arms 18e of the multi-chamber element <NUM> being U-shaped in longitudinal section. The two inclined ribs 18ca may be arranged at a predetermined angle to the lower surface 18b of the multi-chamber element <NUM>. Moreover, contact surfaces 24a are provided on each of the outward-facing sides of the side arms 18e.

Another contact surface 24a is provided adjacent to the upper surface 18a of the multi-chamber element <NUM> on both sides thereof facing a contact surface 24b of the extruded profile 14a. Further, one can recognize a fastening element <NUM> at a front side of the centre member <NUM>, which is integrated in the cast structure of the multi-chamber element <NUM>. This fastening element <NUM>, may be an element for connecting the bogie frame <NUM>' to a centre pin (not depicted) mounted on the car body <NUM>.

Furthermore, it can be derived from <FIG> that the extruded profile 14a of the side member <NUM> comprises a plurality of hollow profiles 14b which may be obtained from a single extrusion process. In the depicted case, each extruded profile 14a includes five hollow profiles 14b. The extruded profiles 14a may be arranged at the railway vehicle <NUM> such that its extrusion direction is along the longitudinal direction L of the railway vehicle <NUM>. This allows for providing side members <NUM> having a lightweight structure with high bending stiffness.

An advantage of the bogie frame <NUM>' shown in the <FIG> is that its arrangement corresponds to the multidirectional loads it must withstand. Since the side members <NUM> must withstand the bending load applied by the weight of the car body <NUM>, the extruded profile 14a shown in <FIG> is suitable for achieving the lightweight structure with high bending stiffness. On the other hand, the centre member <NUM> must withstand not only the bending load but also lateral and torsion loads. Therefore, a more complex shape such as the U-shaped longitudinal section with multiple chambers shown in <FIG> is desirable, which can be provided by a casting process. In addition to saving weight, the depicted bogie frame <NUM>' reduces the number of the single parts by incorporating fastening elements <NUM> into the cast structure.

<FIG> shows the bogie frame <NUM>' including side members <NUM> with cast curved elements <NUM>. <FIG> shows the bogie frame <NUM>' of <FIG> in an exploded view.

In this example, each side member <NUM> comprises a straight extruded profile 14a and two cast curved elements <NUM> made from metal casting. The depicted straight extruded profiles 14a include a plurality of holes <NUM> for connecting them with the centre member <NUM> by bolt connections (fastening bolts) <NUM> (cf. The depicted cast curved elements <NUM> can be jointed to the straight extruded profiles 14a by a bolt connection <NUM> or the adhesive bond at joining points <NUM>, which will be further described in connection with <FIG> and <FIG>.

For example, the cast curved elements <NUM> may be made of iron or aluminium alloy. Preferably, the cast curved elements <NUM> may be made of an aluminium alloy. Most preferably, the aluminium alloy may be a cast alloy of the 7xxx.

The cast curved elements <NUM> shown in <FIG> include a first section 28a, formed as an open hollow profile 28aa with lateral openings 28ab on both sides, the first section 28a having an arcuate shape in longitudinal section (cf. also <FIG>). Furthermore, the cast curved elements <NUM> comprise a second section 28b adjacent to the first section 28a, which is formed as a closed hollow profile 28bb having a rectangular longitudinal section. The second section 28b includes an integrated receptacle 28ba for receiving at least one wheel <NUM> of the railway vehicle <NUM>.

In other words, the curved element <NUM> comprises an integrated connecting part 28ba that allows the curved element <NUM> to be coupled to at least one wheel <NUM> of the railway vehicle <NUM>. This means that cast curved elements <NUM> allow the bogie frame <NUM>' to be connected to the set of wheels <NUM> via the integrated connecting parts 28ba.

As visible in <FIG>, the cast curved element <NUM> is connected to the extruded profile 14a of the side member <NUM> by joining an outer end of the first section 28a, disposed opposite to an end adjacent to the second section 28b, to an outer end of the extruded profile 14a. Since the cast curved elements <NUM> are jointed to the extruded profile 14a by a bolt connection <NUM> and/or an adhesive bond, stresses due to welded joints can be avoided, allowing an improvement in the mechanical strength and stiffness of the bogie frame <NUM>'.

<FIG> shows the bogie frame <NUM>' of <FIG> in a side view. In this view it becomes apparent that the depicted side member <NUM>, which comprises a straight extruded profile 14a and two cast curved elements <NUM>, allocates a space <NUM> between the bogie <NUM> and the car body <NUM> in which electric sensors and structural components of the railway vehicle <NUM> may be arranged. Additionally, the shape of the cast curved elements <NUM> including a first section 28a and a second section 28b, as described in connection with <FIG>, is clearly visible in the side view of <FIG>. Inside the open profile 28aa of the first section 28a, joining points 38a are disposed for attaching strengtheners <NUM> to the curved element <NUM>.

Furthermore, the position of the joining points 38a, at which the cast curved element <NUM> is connected to the extruded profile 14a, is depicted in <FIG>. It can be seen, that in case of bolt connections <NUM> at these joining points 38a, the position has to be adjusted to avoid interference with the holes <NUM> for bolt connection between the side members <NUM> and the centre member <NUM>.

<FIG> shows an enlarged section of the bogie frame <NUM>' depicted in <FIG> illustrating examples of integrated fastening elements <NUM>, <NUM>. Beside the integrated fastening element <NUM>, which may be used for connecting the bogie frame <NUM>' to the centre pin (not depicted), a further bracket <NUM> is shown in <FIG>, which may be used for attaching the motors (not shown) or the brakes (not shown) of the railway vehicle <NUM> to the bogie frame <NUM>'. The depicted bogie frame <NUM>' enables an improvement in mechanical strength and stiffness at the interface of the bracket <NUM> and the fastening element <NUM> to the centre member <NUM>, as these elements <NUM>, <NUM> can already be formed during casting, so that no subsequent welding is necessary.

Furthermore, the enlarged section of the bogie frame <NUM>' shown in <FIG> illustrates the joining points with the respective bolt connections <NUM> for coupling the curved element <NUM> to the extruded profile 14a. Furthermore, joining points for attaching strengtheners <NUM> to the curved element <NUM> can be seen, which are described in more detail in the following <FIG>.

<FIG> show examples of a first strengthener <NUM>, <NUM> attachable to the bogie frame <NUM>'. In particular, <FIG> shows an exploded view of exemplary strengtheners <NUM> and exemplary first strengtheners <NUM> which can be attached to the cast curved element <NUM> and the cast multi-chamber element <NUM>, respectively. <FIG> shows an example of a first strengthener <NUM> embedded in the upper surface 18a of the multi-chamber element <NUM> of the centre member <NUM>, and <FIG> shows an example of a strengthener <NUM> attached to the cast curved element <NUM> of the side member <NUM>.

The depicted strengthener <NUM> is a flat element which can be inserted into the cast structure of the curved element <NUM> of the side member <NUM> (cf. Since the depicted cast curved element <NUM> is designed as an open profile, the stiffness of the curved element <NUM> can be increased by inserting the flat reinforcing element <NUM> thereto.

Each strengthener <NUM> may be fixed to the respective cast curved element <NUM> by a bolt connection via the joining points 44a. It may be also possible to fix the strengtheners <NUM> to the cast curved elements <NUM> by means of adhesive bonds. The strengthener <NUM> may be made of steel and/or carbon fibre-reinforced plastic (CFRP). The strengtheners <NUM> may be produced using a casting process or any other suitable production process.

The depicted first strengtheners <NUM> are also flat elements having approximately the form of a bird. They are inserted into a recess 18d provided in the upper surface 18a of the multi-chamber element <NUM> such that it forms a flat surface with the latter (cf. To achieve this flat surface, a shape of the recess 18d in a plane parallel to the upper or lower surface 18a, 18b may correspond to a shape of the first strengthener <NUM> in longitudinal and transverse directions thereof, and a depth of the recess 18d may correspond to a thickness of the first strengthener <NUM>.

Having a "bird shape" means for the first strengthener <NUM> to extend longitudinally and transversely of the railway vehicle <NUM> when inserted into the recess 18d in the upper surface 18a of the multi-chamber element 18a. In this case, an extension in the longitudinal direction L of the railway vehicle <NUM> is larger than an extension in the transverse direction thereof. Furthermore, the "bird shape" of the first strengthener <NUM> results in a symmetrical shape of the extension in the longitudinal direction L of the railway vehicle <NUM>, wherein a width of the extension in this longitudinal direction L increases with increasing distance from a transverse axis of the first strengthener <NUM>.

The "bird shape" may, for example, be achieved by forming an outer contour of the first strengthener <NUM> in a top view such that an outer contour of a side thereof facing an outside of the centre member <NUM> in the longitudinal direction L of the railway vehicle <NUM> has a W-shape and an outer contour of an opposite side has a T-shape, wherein the bottom of the W and the top of the T are facing each other (cf. also <FIG>). Opposite ends of the T-shaped and W-shaped outer contour may be connected to each other by a straight line, to complete the entire outer contour of the first strengthener <NUM> (and the corresponding recess 18d).

Inserting the first strengthener <NUM>, having approximately the form of a bird in a top view, in a recess 18d in the upper surface 18a of the multi-chamber element <NUM> further increases the stiffness thereof without limiting the space required for mounting the components of the railway vehicle <NUM>.

The first strengtheners <NUM> may also be made of steel and/or CFRP. They may be fixed to the centre member <NUM> by bold connections and or adhesive bonds. The first strengtheners <NUM> may be produced using a casting process or any other process appropriate to create the specific shape of the first strengthener <NUM>.

<FIG> and <FIG> show examples of a second strengthener <NUM> attachable to the bogie frame <NUM>'.

In particular, <FIG> shows an enlarged section of the centre member <NUM> to which second strengtheners <NUM> are attached. The second strengtheners <NUM> include struts 48a, having a cylindrical cross section, which are mounted with mounting brackets <NUM> on the upper surface 18a of the multi-chamber element <NUM>.

The struts 48a extend in longitudinal direction of the centre element <NUM>, which means they can increase the stiffness in lateral direction of the bogie frame <NUM>'. In the presented case, each second strengthener <NUM> uses three mounting brackets <NUM> to keep the struts 48a in the desired position. The second strengtheners <NUM> may be connected via the mounting brackets to the upper or lower surface 18a, 18b of the cast multi-chamber element <NUM> by a bolt connection and/or an adhesive bond.

Preferably, the second strengtheners <NUM> may be made of CFRP. This allows for increasing the stiffness of the centre member <NUM> without increasing its weight significantly.

<FIG> depicts a further example of the second strengthener <NUM> which uses elastic adhesive bonds <NUM> having high damping properties to mount the second strengthener <NUM> on the upper surface 18a of the multi-chamber element <NUM>. Especially, the struts 48a of the second strengthener <NUM>, having a rectangular cross section, are equipped with the elastic adhesive bonds <NUM> via which the struts 48a are fixed to the mounting brackets <NUM>.

Furthermore, the brackets <NUM> may also be fixed to the upper surface 18a of the multi-chamber element <NUM> via elastic adhesive bonds (not shown). The damping effect of the elastic adhesive material can contribute to absorption of the vibration and noise when transmitting through the bogie frame <NUM>'. In addition, the bonding with the elastic adhesive can contribute to reduction of the thermal stress induced by the mismatch of the thermal properties between the CFRP and the cast material of the multi-chamber element <NUM>. This results in improved mechanical strength and stiffness at the adhesive bond area on the upper surface 18a of the multi-chamber element <NUM>.

<FIG> shows a schematic drawing of a second bogie frame <NUM> which is a development of the first bogie frame <NUM>' described above. Features of the second bogie frame <NUM> corresponding to those of the first bogie frame <NUM>' are referred to herein and in the accompanying Figures by the same reference characters. Compared to the first bogie frame <NUM>', the second bogie frame <NUM> is shown in <FIG> with additional equipment mounted on the centre member <NUM>. Significantly, the second bogie frame <NUM> also includes a plurality of reinforcing components <NUM>. The reinforcing components <NUM> are different from the strengtheners <NUM>, <NUM>, <NUM> in that the reinforcing components <NUM> strengthen the joints between the side members <NUM> and the centre member <NUM>, whereas the strengtheners <NUM>, <NUM>, <NUM> strengthen the respective side members <NUM> and centre member <NUM> individually. The centre member <NUM> is bolted to the pair of side members <NUM> via a plurality of fastening bolts <NUM>. Each of the pair of side members <NUM> may be considered "a first structural member <NUM>" of the bogie frame <NUM>, and the centre member <NUM> may be considered "a second structural member <NUM>" of the bogie frame <NUM>.

Although the fastening bolts <NUM> are configured to receive most of the load between the side members <NUM> and the centre member <NUM>, the side members <NUM> are also joined to the centre member <NUM> by the reinforcing components <NUM>, which extend between the side members <NUM> and the centre member <NUM> in the transverse direction T of the railway vehicle <NUM>, which is substantially parallel to the direction of the fastening bolts <NUM>. Specifically, in <FIG> there are four reinforcing components <NUM>, with one at each corner of the centre member <NUM>, whereby each side member <NUM> is joined to the centre member <NUM> by a pair of the reinforcing components <NUM>.

In normal operation, each fastening bolt <NUM> and each reinforcing component <NUM> forms a joint between the structural members <NUM>, <NUM> and supports a respective load across the structural members <NUM>, <NUM>. If one of the fastening bolts <NUM> partially or completely fails, its load transfers to the remaining bolts <NUM> and to the reinforcing component(s) <NUM> across the same joint. This load transfer can increase the load across a particular reinforcing component <NUM> to such an extent that visible damage accumulates on that reinforcing component <NUM>, as discussed in more detail below. In this way, the joints between the side members <NUM> and the centre member <NUM> can be monitored for failure of the fastening bolts <NUM>, even when most of the fastening bolts <NUM> have not failed and the joint as a whole appears to be fully intact and capable of transmitting the necessary loads between the structural members <NUM>, <NUM>. Therefore, the visible damage gives an early indication that a fastening bolt <NUM> has failed, providing an opportunity to tighten, repair or replace the failed bolt <NUM> before subsequent failure of any of the remaining bolts <NUM> or rupture of either of the reinforcing components <NUM> occurs.

<FIG> is a cross-sectional view of part of the bogie frame <NUM>. The cross-section lies in a plane normal to the longitudinal direction L and bisects one of the fastening bolts <NUM> and one of the reinforcing components <NUM>. The reinforcing component <NUM> can be seen to be attached to an upper surface 18a of the bogie frame <NUM>, where it is adjacent to and aligned with the fastening bolt <NUM> in order to minimise the separation between the reinforcing component <NUM> and the fastening bolt <NUM>.

In this configuration, failure of the particular fastening bolt <NUM> can be identified with more certainty. In particular, if the reinforcing component 60a is visibly more damaged than the other reinforcing component <NUM> on the same side of the centre member <NUM>, it is more likely that the damage was caused by failure of the particular fastening bolt <NUM> rather than other more distant fastening bolts.

Each reinforcing component <NUM> is formed as a strip and comprises a planar, first fibre-reinforced plastic layer <NUM> having a first end portion <NUM> and a second end portion <NUM>, the first <NUM> and second <NUM> end portions being spaced in the direction T. The first end portion <NUM> is attached to a platform formed on an upper surface <NUM> of the side member <NUM> (first structural member <NUM>). The second end portion <NUM> is attached to a platform formed on an upper surface 18a of the centre member <NUM> (second structural member <NUM>).

The first end portion <NUM> and the second end portion <NUM> are adhesively bonded to their platforms on the side member <NUM> and the centre member <NUM>, respectively. A structural adhesive such as epoxy, acrylic or urethane can be used to form the adhesive bond. The adhesive bond is generally lighter than an equivalent mechanical fixing and reduces stress concentrations in the reinforcing component <NUM> and the structural members <NUM>, <NUM>.

The reinforcing component <NUM> further comprises a second fibre-reinforced plastic layer <NUM> disposed on a mid part of the first fibre-reinforced plastic layer <NUM> between its first end portion <NUM> and its second end portion <NUM> such that the first and second end portions <NUM>, <NUM> are left uncovered by the second fibre-reinforced plastic layer <NUM>. The second fibre-reinforced plastic layer <NUM> forms with the mid part of the first fibre-reinforced plastic layer <NUM> a central portion <NUM> of the reinforcing component <NUM> that is stronger than the first and second end portions <NUM>, <NUM>.

Additionally, the first <NUM> and second <NUM> end portions of the first fibre-reinforced plastic layer <NUM> are transparent or translucent. Preferably, the first fibre-reinforced plastic layer <NUM> is made of glass fibre-reinforced plastic (GFRP), e.g. a glass-fibre-reinforced epoxy resin, which is inherently translucent. Preferably, the second fibre-reinforced plastic layer <NUM> is made of a carbon-fibre-reinforced plastic (CFRP), e.g. a carbon-fibre-reinforced epoxy resin.

In <FIG>, the mid part of the first fibre-reinforced plastic layer <NUM> and second fibre-reinforced plastic layer <NUM> narrow to a central waist. In addition, the first <NUM> and second <NUM> end portions are each divided into two fingers (although being bisected on the cross-sectional view of <FIG>, only one finger of each end is actually shown in <FIG>). Such features are discussed below in more detail in respect of <FIG>. However, <FIG> shows a schematic drawing of a simpler version of the reinforcing component <NUM> in which the first fibre-reinforced plastic layer <NUM> is a simple rectangle, and the second fibre-reinforced plastic layer <NUM> is a further simple rectangle, centrally disposed on the mid part of the first fibre-reinforced plastic layer <NUM>.

<FIG> shows a schematic drawing of the reinforcing component <NUM> of <FIG> after it has sustained damage. Visible damage accumulation in the form of cracks <NUM> due to load transfer into the component after failure of a fastening bolt <NUM> is focused in the transparent or translucent first <NUM> and second <NUM> end portions of the first fibre-reinforced plastic layer <NUM> rather than in the central portion <NUM> which is strengthened by the second fibre-reinforced plastic layer <NUM>. In other words, the reinforcing component <NUM> is deliberately configured to have weaker regions at the first <NUM> and second <NUM> end portions, to direct damage to accumulate in regions where it can be made visible upon inspection.

<FIG> shows a schematic drawing of part of the bogie frame <NUM> in which a plurality of reinforcing components 60a, 60b, 60c of the simpler version are spaced at regular intervals in a row along a line of the joint between the structural members <NUM>, <NUM>. Each reinforcing component 60a, 60b, 60c extends parallel to and directly above a respective fastening bolt, the positions of which are indicated by their holes 64a, 64b, 64c.

In this configuration, the reinforcing components 60a, 60b, 60c can provide a visual indication of how the joint may be opening under bolt failure. For example, if the joint is opening more at the end of the row where reinforcing component 60a is located, then the expectation would be that the amount of visible damage accumulation would be greatest in the first and/or second end portions <NUM>, <NUM> of reinforcing component 60a, and least in the first and/or second end portions <NUM>, <NUM> of reinforcing component 60c. Conversely, if the joint is opening more at the other end of the row, then the expectation would be reversed, with greater amounts of visible damage accumulation in the first and/or second end portions <NUM>, <NUM> of reinforcing component 60c. Related to this, the locations of the reinforcing components 60a, 60b, 60c may assist with identification of the fastening bolt which has failed. For example, if the fastening bolt at hole 64a fails, more of its load will tend to transfer to the closest reinforcing component 60a than to the other reinforcing components 60b, 60c. Consequently, the formation of cracks <NUM> in the first <NUM> and/or second <NUM> end portions of the closest reinforcing component 60a may be an indication that the fastening bolt in the first hole 64a has failed.

The reinforcing components <NUM> of the bogie frame <NUM> in <FIG> and the reinforcing components 60a, 60b, 60c of the bogie frame <NUM> in <FIG> are all shown being substantially identical to each other. However, a given bogie frame <NUM> may have reinforcing components <NUM> which exhibit different mechanical properties, e.g. different strengths. This can be useful to manage an uneven load distribution across the joint between the side member <NUM> and the centre member <NUM>. For instance, if one fastening bolt <NUM> transmits a greater load than other fastening bolts, an adjacent reinforcing component may be correspondingly strengthened in order that it can accept a higher load transfer from that bolt in the event of bolt failure.

In <FIG>, the reinforcing components <NUM>, 60a, 60b, 60c have equally sized first end portions <NUM> and second end portions <NUM>. In contrast, <FIG> shows a variant, asymmetric reinforcing component <NUM> in which the first end portion <NUM> is smaller than the second end portion <NUM>. The first fibre reinforcing plastic layer <NUM> has the same configuration as in <FIG>, but in <FIG> the first end portion <NUM> extends from the central portion <NUM> over a shorter distance than the second end portion <NUM>. In other words, the second fibre reinforcing plastic layer <NUM> is bonded to the first fibre reinforcing plastic layer <NUM> closer to the first end portion <NUM>.

By such an adjustment, the load distribution in the reinforcing component <NUM> can be such that damage accumulation in the first end portion <NUM> is more concentrated and therefore easier to view than damage accumulation in the second end portion <NUM>. Conveniently, the first end portion <NUM> can then be located at a more accessible location on the bogie frame <NUM>, e.g. on an outer side of the bogie frame <NUM> attaching to the side member <NUM>, rather than attaching to the less reachable centre member <NUM>.

<FIG> shows a schematic drawing of a further variant reinforcing component <NUM> in which the first end portion <NUM> and the second end portion <NUM> spread out from a central waist and are each divided into a row of fingers <NUM>, <NUM> for attaching to the respective structural member <NUM>, <NUM>. The fingers <NUM>, <NUM> of each row can be spaced at regular intervals along the line of the joint between the first and second structural members <NUM>, <NUM>.

Like the row of reinforcing components 60a, 60b, 60c of <FIG> each row of fingers <NUM>, <NUM> can then provide a visual indication of how the joint may be opening under bolt failure. For example, if the joint is opening more at one end of the row than the other, then there is an expectation that visible damage accumulation will be greater in the fingers closer to that end than in the other fingers. Similarly, if a given finger is closer to a fastening bolt <NUM> than the other fingers, then visible damage accumulation in that finger may be an indication of failure of that bolt.

Typically, the fingers <NUM>, <NUM> of the first end portion <NUM> and the second end portion <NUM> are attached to the respective structural elements <NUM>, <NUM> by distinct and separate adhesive bonds. Accordingly, interfacial failure of the adhesive bond of one of the fingers (e.g. a delamination crack) is then less likely to extend across to an adjacent finger.

<FIG> shows a schematic drawing of the bogie frame <NUM> including the reinforcing component <NUM> of <FIG>. The fingers <NUM> of the first end portion <NUM> of the reinforcing component <NUM> are attached to the centre member <NUM> in a row along the line of the joint, and the fingers <NUM> of the second end portion <NUM> are attached to the side member <NUM> in a row along the line of the joint.

However, the fingers <NUM> of the first end portion <NUM>, which are inward of the side member <NUM>, also carry respective sensors <NUM>, such as strain gauges, configured to monitor strain in the first end portion <NUM>. In this way, the first end portion <NUM> can still be monitored despite being relatively inaccessible to visual inspection. The sensors <NUM> also enable the reinforcing component <NUM> to be monitored continuously, e.g. to obtain data of the load across the joint in real time. This can speed up diagnosis of fastening bolt failure.

<FIG> shows a schematic drawing of the reinforcing component <NUM> of <FIG> but fitted with removable covers <NUM> to protect both the first end portion <NUM> and the second end portion <NUM>. The removable covers <NUM> are configured to cover the otherwise exposed surface of the first fibre-reinforced plastic layer <NUM>. The covers <NUM> prevent surface damage to or dirt accumulation on the end portions <NUM>, <NUM> which could otherwise reduce or obscure the visibility of cracks <NUM> in the first fibre reinforce plastic layer <NUM>. The covers <NUM> are removed for the performance of maintenance inspection of the end portions <NUM>, <NUM>, and are then refitted or replaced.

The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention as defined by the appended claims.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the scope of the invention defined by the appended claims.

Claim 1:
A bogie frame (<NUM>) for a railway vehicle (<NUM>), the bogie frame (<NUM>) comprising structural members (<NUM>, <NUM>) defining the frame (<NUM>), and one or more reinforcing components (<NUM>, 60a, 60b, 60c, <NUM>, <NUM>) joining the structural members (<NUM>, <NUM>), the or each reinforcing component (<NUM>, 60a, 60b, 60c, <NUM>, <NUM>) comprising:
a first fibre-reinforced plastic layer (<NUM>, <NUM>, <NUM>) having spaced first and second end portions (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), the first end portion (<NUM>, <NUM>, <NUM>) attaching to a first structural member (<NUM>) of the bogie frame (<NUM>), and the second end portion (<NUM>, <NUM>, <NUM>) attaching to a second structural member (<NUM>) of the bogie frame (<NUM>), wherein the first and second structural members (<NUM>, <NUM>) are also joined together by one or more fastening bolts (<NUM>); and
a second fibre-reinforced plastic layer (<NUM>, <NUM>, <NUM>) disposed on a mid part of the first fibre-reinforced plastic layer (<NUM>, <NUM>, <NUM>) between its first and second end portions (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) such that the first and second end portions (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) are left uncovered by the second fibre-reinforced plastic layer (<NUM>, <NUM>, <NUM>),
wherein the second fibre-reinforced plastic layer (<NUM>, <NUM>, <NUM>) forms with the mid part of the first fibre-reinforced plastic layer (<NUM>, <NUM>, <NUM>) a central portion (<NUM>, <NUM>, <NUM>) of the reinforcing component (<NUM>, 60a, 60b, 60c, <NUM>, <NUM>) that is stronger than the first and second end portions (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), and wherein at least the first and second end portions (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) of the first fibre-reinforced plastic layer (<NUM>, <NUM>, <NUM>) are transparent or translucent.