Apparatus, system, method and computer program for tribo-dynamic measurements

Abstract

Apparatus for use with a tribological test rig for performing tribo-dynamic measurements on a test component, which may be a bearing 405, is disclosed. The apparatus comprises load control means (301,

Description

TECHNOLOGICAL FIELD Examples of the present disclosure relate to an apparatus, system, method and computer program fortribo-dynamic measurements. BACKGROUND It is common practice to characterise structures / physical components (e.g. one or more components of rotating machinery, not least such as a shaft-bearing conjunction) using modal testing statically. However, this neglects the influence of tribological phenomenon such as lubrication films which influence rotating machinery / component’s dynamic properties significantly (not least stiffness and damping properties of rotating lubricated-bearing-shaft conjunctions such a roller bearing elements). A rotating component such as a rolling element bearing requires a lubricant film within a contact between an inner / outer race and constituent rolling elements. Such a film supports a radial load, reduces friction, and increases durability of the individual rolling elements and raceways. The lubricant is entrained into the contact at a velocity that is the average of two surface velocities (inner / outer bearing raceway velocity and rolling element tangential velocity). With increasing entrainment speed, the lubricant’s central film thickness increases. The increase in film thickness increases the radial load within the rolling element contact. This increase in radial load causes an increase in localised surface elastic deformation to raceways and rolling elements. Accordingly, a consequence of the increased film thickness in a rolling element bearing (which increases with increase rotational speed) is that it alters the stiffness and damping properties of the rolling element bearing. In other words, a rolling element bearing’s stiffness and damping value changes / increases with increasing rotational speed of the rolling element bearing. Moreover, stiffness and damping values alter dynamic characteristics of the rolling element bearing such as shifting its resonant frequencies - which can effect its durability and efficiency. It is desirable to perform a tribological assessment / test of a physical component (such as a roller element bearing) to determine its tribological properties. Moreover, it is desirable to perform dynamic (i.e. non-static) tribological assessments / tests of a physical component (such as a roller element bearing) to determine its tribological properties in motion / during use - i.e. to perform tribo-dynamic measurements to determine the physical component’s tribo-dynamic properties. Conventional systems and tribological test rigs for performing a tribological assessment of a physical component (such as a roller element bearing) to analyse durability and efficiency of the component are not always optimal. In order to evaluate the performance of bearings, it would be preferable to consider both the tribological as well as the dynamic performance of the bearings relative to the dynamic loads supplied by power transmitting components (e.g. not least gears). In other words, it would be desirable to test the performance of bearings under similar conditions (and via a similar rotational system and drive train) to those that the bearings would be expected to experience in use, e.g. when being driven via power transmitting components, such as gears, that would be used with the bearings in their envisaged real-world application, i.e. so as to seek to replicate the rotational system / drive train (including a particular gear pair of the rotational system / drive train used to transmit power) that the bearing would be a part of when in situ in the rotational system during its real-world use for its intended application. Conventionally, if a particular rotational system / drive train, that included a particular gear pair, were sought to be replicated when performing tribo-dynamic testing / measurements (e.g. on a component of the particular rotational system / drive train, such as a bearing) using a tribological test rig; then the tribological test rig would need to include a test rotational system that includes the particular gear pair (e.g. the drive train for the tribological test rig would need to include the particular gear pair). However, manufacturing gears is not only difficult but costly due to the tooling cost, and time associated with manufacturing an accurate gear pair. Also, when testing / proto-typing a gear design, sometimes a final gear design might not be available since the final gear design depends on a rotational system’s behaviour, which may be governed by bearings of the rotational system. Also, adding gears to a rotational system to be tested adds additional mass and stiffness to the test system which is not desired. In some circumstances it can be desirable to provide an apparatus for improving tribo-dynamic measurements, such as modal testing or force transmissibility testing of rotating structures, components, devices or machinery. In some circumstances it can be desirable to provide an apparatus for simulating / replicating loads that rotating structures, components, devices or machinery may be under during typical real-world / in-situ use. In some circumstances it can be desirable to provide an apparatus for simulating / replicating a gear pair. The listing or discussion of any prior-published document or any background in this specification should not necessarily be taken as an acknowledgement that the document or background is part of the state of the art or is common general knowledge. One or more aspects / examples of the present disclosure may or may not address one or more of the background issues. BRIEF SUMMARY The scope of protection sought for various embodiments of the invention is set out by the claims. According to various, but not necessarily all, examples of the disclosure there are provided examples as claimed in the appended claims. Any examples and features described in this specification that do not fall underthe scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention. According to at least some examples of the disclosure there is provided an apparatus apparatus for use with a tribological test rig for performing tribo-dynamic measurements on a test component, the apparatus comprising: load control means configured to control an application of a radial load and an axial load on the test component, wherein the application of the radial and axial loads is controlled such that a dynamically variable radial load and a dynamically variable axial load are applied to the test component. According to at least some examples of the disclosure there is provided a system comprising: the apparatus as mentioned above; radial loading means configured to directly and / or indirectly apply a radial load to the test component; and axial loading means configured to directly and / or indirectly apply an axial load to the test component. According to various, but not necessarily all, examples of the disclosure there is provided a method for use with a tribological test rig for performing tribo-dynamic measurements on a test component, the method comprising: controlling an application of a radial load and an axial load on the test component, wherein the application of the radial and axial loads is controlled such that a dynamically variable radial load and a dynamically variable axial load are applied to the test component. According to various, but not necessarily all, examples of the disclosure there is provided a computer program comprising instructions, which when executed by at least one processor, cause the above-mentioned apparatus to perform the above-mentioned method. According to various, but not necessarily all, examples of the disclosure the apparatus may be embodied as a chipset, circuitry, or module comprising means / processing circuitry configured to perform the above-mentioned functionality. According to various, but not necessarily all, examples of the disclosure there is provided an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: control an application of a radial load and an axial load on a test component of a tribological test rig for performing tribo-dynamic measurements on the test component, wherein the application of the radial and axial loads is controlled such that a dynamically variable radial load and a dynamically variable axial load are applied to the test component. According to various, but not necessarily all, examples of the disclosure there is provided a non-transitory computer readable medium encoded with instructions that, when executed by at least one processor, causes at least the following to be perform: control an application of a radial load and an axial load on a test component of a tribological test rig for performing tribo-dynamic measurements on the test component, wherein the application of the radial and axial loads is controlled such that a dynamically variable radial load and a dynamically variable axial load are applied to the test component. According to various, but not necessarily all, examples of the disclosure there is provided a method of providing and / or manufacturing an apparatus and / or system as described herein. According to various, but not necessarily all, examples of the disclosure there is provided a method of using an apparatus and / or system as described herein. The following portion of this 'Brief Summary’ section describes various features that can be features of any of the examples described in the foregoing portion of the 'Brief Summary’ section. The description of a function should additionally be considered to also disclose any means suitable for performing that function. In some but not necessarily all examples, the load control means is further configured to control the application of the radial and axial loads so as to apply a predetermined dynamically variable radial load simultaneously with a predetermined dynamically variable axial load. In some but not necessarily all examples, the load control means is further configured to control the application of the dynamically variable radial and axial loads so as to synchronise an application of a time varying radial load with an application of a time varying axial load. In some but not necessarily all examples, the load control means is further configured to control the application of a dynamically variable tangential load to the test component. In some but not necessarily all examples, the load control means is further configured to control the application of the dynamic loads to simulate one or more expected dynamic loads that would be applied to the test component if the test component were rotatably driven via one or more particular power transmission components. In some but not necessarily all examples, the load control means is further configured to control the application of dynamic loads so as to apply a pre-determined load profile to the test component. In some but not necessarily all examples, the pre-determined load profile is based, at least in part, on a pre-determined load profile of one or more of: a power transmission component, a component of a drive train, a gear, a gear pair, and a meshing helical gear pair. In some but not necessarily all examples, the pre-determined load is configured to simulate a load profile of one or more of: a power transmission component, a component of a drive chain, a gear, a gear pair, and a meshing helical gear pair. In some but not necessarily all examples, the control of the application of the loads comprises controlling at least one or more of: means for directly and / or indirectly applying a radial load to the test component; means for directly and / or indirectly applying an axial load to the test component; and means for directly and / or indirectly applying a tangential load to the test component. In some but not necessarily all examples, the control of the application of the loads comprises dynamically controlling an amount of radial, axial and / or tangential load directly and / or indirectly applied to the test component by means for directly and / or indirectly applying radial, axial and / or tangential loads to the rotating structure. In some but not necessarily all examples, the application of the radial and axial loads is controlled such that, in use when the test component is rotating, predetermined dynamically varying radial and axial loads are applied to the rotating structure as it rotates. In some but not necessarily all examples, the test component is one or more of: a bearing coupled to a rotatable shaft; and a rolling element bearing. In some but not necessarily all examples, the apparatus is embodied in a chipset, circuitry, or module. While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all of the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all of the features, in any combination, may be implemented by / comprised in / performable by an apparatus, a method, and / or computer program instructions as desired, and as appropriate. BRIEF DESCRIPTION OF THE DRAWINGS Some examples will now be described with reference to the accompanying drawings in which: FIG. 1 shows an example of a method according to the present disclosure; FIG. 2 shows an example of the subject matter described herein; FIG. 3 shows an example of the subject matter described herein; FIG. 4 schematically shows an example of an apparatus according to the present disclosure; FIG. 5 schematically shows an example of a computer program according to the present disclosure; FIG. 6 shows a further example of the subject matter described herein; FIG. 7 shows a yet further example of the subject matter described herein; and FIG. 8 shows an example of another system according to the present disclosure. The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures. In the drawings (and description) a similar feature may be referenced by the same three-digit number. In the drawings (and description), an optional subscript to the three-digit number can be used to differentiate different instances of similar features. Therefore, a three-digit number without a subscript can be used as a generic reference and the three-digit number with a subscript can be used as a specific reference. A subscript can comprise a single digit that labels different instances. A subscript can comprise two digits including a first digit that labels a group of instances and a second digit that labels different instances in the group. DETAILED DESCRIPTION The figures schematically illustrate, and the following description describes, various examples of the disclosure including an apparatus 10 for use with a tribological test rig 300 for performing tribo-dynamic measurements on a test component 405. The apparatus 10 comprises load control means 201 configured to control an application of a radial load 401 and an axial load 402 to the test component 405, wherein the application of the radial and axial loads is controlled such that a dynamically variable radial load and a dynamically variable axial load are applied to the test component. FIG. 1 schematically illustrates an example of a method 100. It will be understood that the block as illustrated in FIG. 1, as well as the further functions described below, can be implemented by various means, such as hardware, firmware, and / or software including one or more computer program instructions. For example, one or more of the functions described below can be performed by a single physical entity (such as the apparatus 10 described with reference to FIG. 4 which can be embodied in a chipset, circuitry, or module - such an apparatus comprising means for performing the below described functions). One or more of the functions described below can be implemented by a computer program (such as the computer program 14 as described with reference to FIG. 4 which can be stored by a computer readable storage device / memory and performed by a processor). As will be appreciated, any such computer program instructions can be loaded onto a computer or other programmable apparatus (i.e. hardware) to produce a machine, such that the instructions when performed on the programmable apparatus create means for implementing the functions specified. These computer program instructions can also be stored in a computer-readable medium that can direct a programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the blocks. The computer program instructions can also be loaded onto a programmable apparatus to cause a series of operational actions to be performed on the programmable apparatus to produce a computer-implemented process such that the instructions which are performed on the programmable apparatus provide actions for implementing the functions specified in the blocks. One or more of the features discussed in relation to FIG. 1 can be found in one or more of the other FIGs. During the following discussion of FIG. 1, use will be made of reference numerals of features shown in the other FIGs for the purposes of explanation. In block 101, an application of a radial load 401 and an application of an axial load 402 applied to a test component 405 (i.e. a component, not least for example a roller element bearing, under investigation that is the subject of tribo-dynamictesting / measurements via a tribological test rig 300) is controlled so as to apply dynamically variable radial and axial loads to the test component. In some examples, an application of a tangential load 403 applied to the test component 405 is also controlled so as to apply dynamically variable tangential load to the test component. Gears, not least such as a meshed helical gear pairs, exhibit dynamic axial, radial and tangential load. The former two of these are supported by bearings. As will be discussed further below, in certain examples of the disclosure a radial load and an axial load applied (directly to or indirectly) to a test component, i.e. a bearing, is controlled so as to replicate the dynamics and loads of imparted by a meshed helical gear pairs on a shaft-bearing conjunction. FIG. 2 schematically shows an example of a test component 405 that is the subject of tribodynamic testing / measurements (e.g. impact testing or modal testing for characterising tribo-dynamic properties such as stiffness and damping of the test component) via a tribological test rig. In this example, the test component is a roller element bearing that supports a shaft 404 that may be driven (either directly or indirectly vis one or more couplings) by a prime mover (e.g. an electric motor). The shaft defines an axial direction 202 that is parallel to a central longitudinally extending axis 404a of the shaft. FIG. 2 also shows two other directions orthogonal to the axial direction 202, namely a radial direction 201 and a tangential direction 202. It is to be appreciated that other test components could be used, not least other rotation structure whose tribo-dynamic characterisation is to be determined, such as a bearing-shaft-lubricant conjunction or other rational system. FIG. 3 schematically shows an example of a load control means 301 that controls the application of dynamic loads (e.g. radial, axial and tangential) to the test component. In this regard, the load control means controls one or more of: a radial load applying means 302, an axial load applying means 303, and a tangential load applying means 304 to respectively apply, directly or indirectly, one or more dynamically variable radial, axial and / or tangential loads to the test component. As used herein, the load control means 301 can, but need not be used to referto any suitable means or controller for controlling the application of loads to the test component, i.e. controlling the radial, axial and / or tangential load applying means. The axial load applying means may be a controller 11 of an apparatus 10 such as shown in FIG. 4. As used herein, the radial load applying means 302 can, but need not be used to refer to any suitable means or device for applying a radial load, directly and / or indirectly, to the test component. The radial load applying means may be an actuator, not least such as a piezo electric actuator, an electromagnetic shaker or a vibrator. As used herein, the axial load applying means 303 can, but need not be used to refer to any suitable means or device for applying an axial load, directly and / or indirectly, to the test component. The axial load applying means may be an actuator, not least such as a piezo electric actuator, or a dynamic axial loading device such as a piezo-electric stack. As used herein, the tangential load applying means 304 can, but need not be used to refer to any suitable means or device for applying a tangential load, directly and / or indirectly, to the test component. The tangential load applying means may be or comprise a prime mover or other rotation driving device such as an electric motor. One or more of the radial, axial and / or tangential load applying means can be configured to apply respective radial, axial and / or tangential loads directly to the test component. Alternatively, one or more of the radial, axial and / or tangential load applying means can be configured to apply respective radial, axial and / or tangential loads indirectly to the test component (for example, by applying respective radial, axial and / ortangential loads directly to a shaft to which the test component is coupled, or applying respective radial, axial and / or tangential loads directly to a bearing component coupled to the shaft to which the test component is coupled). One or more of the radial, axial and / or tangential load applying means may be parts / modules of a tribological test rig 300. In some examples, the load control means itself may also be a part / module of the tribological test rig 300. In some examples, the application of the radial and axial loads (and, in some examples, also the tangential load) are controlled so as to apply a predetermined dynamically variable radial load simultaneously with a predetermined dynamically variable axial load (and, in some examples, also a predetermined dynamically variable tangential load). In some examples, the dynamically variable radial and axial loads (and, in some examples, a predetermined dynamically variable tangential load) comprise predetermined time varying radial and axial loads (and, in some examples, a predetermined time varying tangential load). In some examples, the application of the radial and axial loads (and, in some examples, the tangential load) are controlled so as to synchronise the application of the dynamically variable radial and axial loads (and tangential load) applied, directly and / or indirectly to the test component. In some examples, the application of the radial and axial loads is controlled so as to apply a predetermined dynamically variable radial load simultaneously with a predetermined dynamically variable axial load. Such loads could be applied whilst tribo-dynamic testing / measurements are being performed on the test component. Examples of the invention may thereby control loading means so as to produce a dynamic force radially and axially, as well as synchronising the applied radially and axially loads applied so as to replicate the dynamics of a helical gear pair on a shaft-bearing conjunction, and thereby avoid the need for the helical gear pair to actually be included in the rotation system / drive train when performing tribo-dynamic testing. In some examples, the application of the dynamic loads is controlled so as to simulate one or more expected dynamic loads that would be expected to be applied to the test component if the rotation system under test were to include one or more particular power transmission components, or if the test component were rotatably driven via one or more particular power transmission components. In this regard, the dynamic loads could be controlled so as to mirror / emulate / replicate one or more of a radial, axial and / or tangential load that would be applied / impartedtothetest component if the rotation system under test were to have included one or more particular transmission components. In such a manner, in effect, the one or more particular transmission components can be simulated as though they were present in the rotation system under test / if the test component were rotatably driven via the one or more particular power transmission components. Advantageously, examples may thereby, in effect, simulate one or more 'virtual power transmission components” in the rotation system under test, or simulate as though the test component were rotatably driven via one or more particular power transmission components. Such power transmission components that may be simulated / ”virtualised” may include, not least: a gear, gear pair or a meshing helical gear pair. In some examples, the application of dynamic loads is controlled so as to apply a predetermined load profile (directly or indirectly) to the test component. Such a predetermined load profile may comprise a predetermined time-varying dynamically variable radial / axial and / or tangential load profile. In some examples, the pre-determined load profile is based, at least in part, on a predetermined (time varying) load profile of one or more of: a power transmission component, a component of a drive train, a gear, a gear pair, and a meshing helical gear pair. In some examples, the pre-determined load is configured to simulate a load profile of one or more of: a power transmission component, a component of a drive chain, a gear, a gear pair, and a meshing helical gear pair. Profiles can be generated from virtual prototypes of the power transmission component(s), e.g. gear pair, and extracted into a time series data format. This can be in turn provided to the axial load applying means (e.g. a dynamic axial loading device such as a piezo-electric stack), and the radial load applying means (e.g. a radial loading device such as an electromagnetic shaker). The tangential and radial loading device could be provided by an auxiliary bearing or directly to the shaft via a point contact. In some examples, the application of the radial and axial loads is controlled such that, in use when the test component is rotating, predetermined dynamically varying radial, axial and / or tangential loads are applied to the rotating structure as it rotates, e.g. when tribodynamic testing is performed on the test component using a tribological testing rig. FIG. 4 schematically illustrates a block diagram of an apparatus 10 for performing the above-described methods and providing the functionality described in the present disclosure. The apparatus comprises a controller 11, which could be provided within a device such as a computer 302. In some, but not necessarily all examples, the apparatus can be embodied as a chip, chip set, circuitry or module. As used here 'module' refers to a unit or apparatus that excludes certain parts / components that would be added by an end manufacturer or a user. Implementation of the controller 11 can be as controller circuitry. The controller 11 can be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware). The controller 11 can be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program 14 in a general-purpose or special-purpose processor 12 that can be stored on a computer readable storage medium 13, for example memory, or disk etc, to be executed by such a processor 12. The processor 12 is configured to read from and write to the memory 13. The processor 12 can also comprise an output interface via which data and / or commands are output by the processor 12 (e.g. to control an impacting means) and an input interface via which data and / or commands are input to the processor 12 (e.g. sensor measurements of positional information such as lateral and vertical displacement and angular orientation / velocity). The apparatus can be coupled to or comprise one or more other components 15 (not least for example: sensors, impacting means, input / output user interface elements, other modules / devices / components for inputting and outputting data / commands, and / or other components and controllers of a tribological test rig 300). The memory 13 stores a computer program 14 comprising instructions (computer program instructions / code) that controls the operation of the apparatus 10 when loaded into the processor 12. The instructions of the computer program 14, provide the logic and routines that enables the apparatus to perform the methods described above and provide the functionality discussed in the present disclosure. The processor 12, by reading the memory 13, is able to load and execute the computer program 14. The computer program instructions may be comprised in a computer program, a non-transitory computer readable medium, a computer program product, a machine-readable medium. The term "non-transitory,” as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. RAM vs. ROM). In some but not necessarily all examples, the computer program instructions may be distributed over more than one computer program. Although the memory 13 is illustrated as a single component / circuitry it can be implemented as one or more separate components / circuitry some or all of which can be integrated / removable and / or can provide permanent / semi-permanent / dynamic / cached storage. Although the processor 12 is illustrated as a single component / circuitry it can be implemented as one or more separate components / circuitry some or all of which can be integrated / removable. The processor 12 can be a single core or multi-core processor. The apparatus can include one or more components (e.g. sensors, impacting means, and / or other modules / devices / components of a tribological test rig) for effecting the methods described above and provide the functionality discussed in the present disclosure. It is contemplated that the functions of these components can be combined in one or more components or performed by other components of equivalent functionality. The description of a function should additionally be considered to also disclose any means suitable for performing that function. Where a structural feature has been described, it can be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described. Although examples of the apparatus have been described above in terms of comprising various components, it should be understood that the components can be embodied as or otherwise controlled by a corresponding controller or circuitry such as one or more processing elements or processors of the apparatus. In this regard, each of the components described above can be one or more of any device, means or circuitry embodied in hardware, software or a combination of hardware and software that is configured to perform the corresponding functions of the respective components as described above. The apparatus can, for example, be a part of a tribological test rig itself. In some examples, the apparatus comprises: at least one processor 12; and at least one memory 13 storing instructions that, when executed by the at least one processor 12, cause the apparatus at least to: control an application of a radial load and an axial load on a test component of a tribological test rig for performing tribo-dynamic measurements on the test component, wherein the application of the radial and axial loads is controlled such that a dynamically variable radial load and a dynamically variable axial load are applied to the test component. The above-described examples find application as enabling components of tribological test rigs / machines for performing tribo-dynamic measurements on test objects, not least for example roller element bearings. FIG. 5, illustrates a computer program 14 which may be conveyed via a delivery mechanism 20. The delivery mechanism 20 can be any suitable delivery mechanism, for example, a machine-readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a solid-state memory, a record medium or an article of manufacture that comprises ortangibly embodies the computer program 14. The delivery mechanism can be a signal configured to reliably transfer the computer program. An apparatus can receive, propagate or transmit the computer program as a computer data signal. In certain examples of the present disclosure, there is provided a computer program comprising instructions, which when executed by an apparatus, cause the apparatus to perform at least the following or for causing performing at least the following: control an application of a radial load and an axial load on a test component of a tribological test rig for performing tribo-dynamic measurements on the test component, wherein the application of the radial and axial loads is controlled such that a dynamically variable radial load and a dynamically variable axial load are applied to the test component. References to 'computer program’, 'computer-readable storage medium’, 'computer program product’, 'tangibly embodied computer program’ etc. or a 'controller’, 'computer’, 'processor’ etc. should be understood to encompass not only computers having different architectures such as single / multi- processor architectures and sequential (Von Neumann) / parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other devices. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc. Various, but not necessarily all, examples of the present disclosure can take the form of a method, an apparatus or a computer program. Accordingly, various, but not necessarily all, examples can be implemented in hardware, software or a combination of hardware and software. Various, but not necessarily all, examples of the present disclosure are described using These program instructions can be provided to one or more processor(s), processing circuitry or controller(s) such that the instructions which execute on the same create means for causing implementing the functions specified in the block or blocks, i.e. such that the method can be computer implemented. The computer program instructions can be executed by the processor(s) to cause a series of operational block / steps / actions to be performed by the processor(s) to produce a computer implemented process such that the instructions which execute on the processor(s) provide block / steps for implementing the functions specified in the block or blocks. Accordingly, the blocks support: combinations of means for performing the specified functions; combinations of actions for performing the specified functions; and computer program instructions / algorithm for performing the specified functions. It will also be understood that each block, and combinations of blocks, can be implemented by special purpose hardware-based systems which perform the specified functions or actions, or combinations of special purpose hardware and computer program instructions. FIG. 6 schematically illustrates an example wherein a radial force / load 401 and a tangential force / load 403 - whose force / load profiles are configured to simulate a gear pair - are directly applied to a shaft 404, supported by bearings 405, which is driven by a prime mover. This example also shows an axial force / load 402 being applied to each of the bearings. The radial, axial and tangential loads may be dynamically applied to a bearing 405i, i.e. so as to apply a loading profile that corresponds to a loading profile of a gear pair, during tribological testing of the bearing (e.g. performing a modal test, such as using a modal hammer, to measure damping and stiffness of the bearing) so as to emulate the dynamics that the shaft, and bearing, would be under where the shaft to be driven via the gear pair. FIG. 7 schematically illustrates an example wherein a radial force / load 401 and a tangential force / load 403 - whose force / load profiles are configured to simulate a gear pair - are indirectly applied to a shaft 404, namely by applying the radial and tangential forces to an auxiliary bearing 406 that is coupled to a shaft 404 which itself is supported by the bearings 405. Similar to that of FIG. 6, whilst tribological testing is being performed on the bearing 405i, the radial, axial and tangential loads may be dynamically applied to the bearing 405i, albeit indirectly via the auxiliary bearing 406, so as to apply a loading profile that corresponds to a loading profile of a gear pair thereby emulating the dynamics that the shaft 404 and bearing 405i conjunction would be under where it to be driven via the gear pair. FIG. 8 shows an example of a tribo-dynamic test rig 300 according to the present disclosure that allows for tribo-dynamic characterisation of high-speed rolling element bearings and their respective lubricating fluids. The test rig comprises a heavy machine bed which is used to mount two bearing blocks, and a loading tower. The bearing blocks support two rolling element bearings, at least one of which corresponds to the test component 405 whose tribo-dynamic properties (e.g. stiffness and damping) are to be characterised. The bearings in turn support a main test shaft 404. One end of the main test shaft is left free with no fixture on the end. The other end of the shaft is connected to a first coupling. The first coupling connects the main test shaft to a torque transducer via another shaft. The torque transducer is then connected to a spindle / rotational prime mover via a second coupling and a yet further shaft. A bearing axial preload device, i.e. axial load applying means 303, applies an axial load to an outer raceway of the bearing(s) under test. The load tower helps to support a modal impact hammer and a shaker device. The load tower directly supports a linear rail guide which allows for a mounting bracket to slide freely in one direction, e.g. a vertical direction towards the main shaft. The modal hammer and a shaker, i.e. radial load applying means 302, are both directly connected to the mounting bracket. The mounting bracket can either be moved via a pneumatic or solenoid impulse or shaker excitation. A sensor bracket is mounted directly to the bearing block housing. The sensor bracket contains two motion (displacement) sensors 304, e.g. capacitive based sensors, that are aligned perpendicularly with respect to on another. The motion sensors measure the motion of the shaft relative to the bearing block housing. One in a direction parallel to the direct excitation of the shaft (e.g. a radial / vertical direction). The other sensor measures the motion perpendicular to the initial excitation (e.g. a horizontal radial direction). The torque transducer measures the torque required of the rotational prime mover / motor to rotate the shaft. The modal hammer and / or a shaker accelerometer acquire voltage signals which are passed through a conditioning amplifier and then to a data acquisition device, DAQ. The DAQ in turn passes the information to a computer which reads in the data. The torque transducer motion sensors are also connected to the same DAQ. The computer (which includes the load control means 201) is used to control the shaker / pneumatics / solenoid (which includes the radial and axial load applying means 202 and 203) as well as the spindle / rotational prime mover (which includes the tangential load applying means 204). The bearings may be lubricated via splash / drip lubrication feed via a heated recirculation sump, which can be controlled via a computer. There now follows a discussion of a methodology of performing tribo-dynamic measurements / characterisations of a test component (i.e. bearing) using apparatuses and systems in accordance with the present disclosure. A test is programmed via a computer. This includes detailing rotor test speeds (i.e. a number of discrete angular velocities of the shaft to test), an amount of axial preload, an impact load required (up to 2.2kN), and a number of repeats required at each test speed / impact load / axial preload required. The computer automatically runs the test without human intervention. In each single test: the computer controls an axial preload and a dynamic axial load applied to the bearings. the computer controls a dynamic radial load applied to the bearings. the shaft’s angular velocity is controlled via the computer. the computer remotely triggers the impacting means / mechanism. the modal hammer tip makes an impact directly to the main test shaft itself to excite the system whilst the main test shaft is rotating. The DAQ continuously captures data from the modal hammer, shaker, motion sensors and torque transducer. The system repeats the following steps until the desired programme is complete. One data post process method consists of: o a low pass filter is used to remove some of the undesirable noise. o the measured signals are further conditioned to remove extra sources of noise such as run out. o the computer uses software to compute a frequency response of the bearing-shaft-lubricant conjunctions relative to the impact / shaking (the bearing-shaft-lubricant conjunctions corresponding to a joint that comprises of a shaft seated within a bearing where lubrication is present) o the real component of a frequency response function, FRF, equates to the test component’s stiffness o the imaginary term of the FRF equates to the test component’s damping Such a methodology and experimental test rig may aid the selection and design of efficient, durable rolling element bearings, such as rolling element bearings that can be found in many industrial applications including but not limited to: automotive, aviation, marine, and power generation applications. Various examples of the disclosure may enable an evaluation of bearing performance (wear, friction, dynamics) whilst taking into account / consideration dynamics of a gear pair. In a real system, certain vibrating forces are transferred from gears to the bearings. Using examples of the present disclosure, forces can be applied to a shaft (and consequently bearings) via synchronized application of pre-determined forces axial and radial directions. This may allow realistic replication of bearing conditions under gear loads. Examples of the disclosure may provide a faster way to evaluate bearing-shaft-gear pairings, by emulating a "virtual” gear, i.e. emulating the dynamics / loading of a gear pair on a shaft-bearing test rig device, thereby avoiding the need, time, resources and cost involved in manufacturing a gear pair to evaluate a bearing-shaft-gear pairing. Examples of the disclosure may enable realistic tribo-dynamic experiments to be performed on, for example, roller element bearings that better reflect real-world usage of roller element bearings, e.g. the dynamics / loading of a gear pair on a shaft-bearing conjunction which may thereby facilitate the evaluation and development of reliable and efficient roller bearing element designs. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Features described in the preceding description can be used in combinations otherthan the combinations explicitly described. Although functions have been described with reference to certain features, those functions can be performable by other features whether described or not. Although features have been described with reference to certain examples, those features can also be present in other examples whether described or not. Accordingly, features described in relation to one example / aspect of the disclosure can include any or all of the features described in relation to another example / aspect of the disclosure, and vice versa, to the extent that they are not mutually inconsistent. Although various examples of the present disclosure have been described in the preceding paragraphs, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as set out in the claims. For example, whilst the present disclosure has described examples of characterising roller bearing stiffness and damping during dynamics conditions, examples of the invention could be applied to other types of bearings and other test components. Examples of the invention could be applied to modal testing of rotating devices or machinery. Examples could also be used in full automotive, aeronautical, marine, power generation powertrains and drivetrains, manufacturing assembly lines. The term 'comprise' is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X can comprise only one Y or can comprise more than one Y. If it is intended to use 'comprise' with an exclusive meaning then it will be made clear in the context by referring to "comprising only one ...” or by using "consisting”. In this description, the wording 'connect’ and 'couple’ and their derivatives mean operationally connected and coupled. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e. so as to provide direct or indirect connection and coupling. Any such intervening components can include hardware and / or software components. In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ’example’ or 'for example’, 'can’ or 'may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some or all other examples. Thus 'example’, 'for example’, 'can’ or 'may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class. In this description, references to "a / an / the” [feature, element, component, means ...] are used with an inclusive not an exclusive meaning and are to be interpreted as "at least one” [feature, element, component, means ...] unless explicitly stated otherwise. That is any reference to X comprising a / the Y indicates that X can comprise only one Y or can comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use 'a’ or 'the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of 'at least one’ or 'one or more’ can be used to emphasise an inclusive meaning but the absence of these terms should not betaken to infer any exclusive meaning. As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements. The presence of a feature (or combination of features) in a claim is a reference to that feature (or combination of features) itself and also to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result. In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described. In the above description, the apparatus described can alternatively or in addition comprise an apparatus which in some other examples comprises a distributed system of apparatus, for example, a client / server apparatus system. In examples where an apparatus provided forms (or a method is implemented as) a distributed system, each apparatus forming a component and / or part of the system provides (or implements) one or more features which collectively implement an example of the present disclosure. In some examples, an apparatus is re-configured by an entity other than its initial manufacturer to implement an example of the present disclosure by being provided with additional software, for example by a user downloading such software, which when executed causes the apparatus to implement an example of the present disclosure (such implementation being either entirely by the apparatus or as part of a system of apparatus as mentioned hereinabove). The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure. Whilst endeavouring in the foregoing specification to draw attention to those features of examples of the present disclosure believed to be of particular importance it should be understood that the applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not particular emphasis has been placed thereon. The examples of the present disclosure and the accompanying claims can be suitably combined in any manner apparent to one of ordinary skill in the art. Separate references to an "example”, "in some examples” and / or the like in the description do not necessarily refer to the same example and are also not mutually exclusive unless so stated and / or except as will be readily apparent to those skilled in the art from the description. For instance, a feature, structure, process, block, step, action, or the like described in one example may also be included in other examples, but is not necessarily included. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present disclosure. Further, while the claims herein are provided as comprising specific dependencies, it is contemplated that any claims can depend from any other claims and that to the extent that any alternative embodiments can result from combining, integrating, and / or omitting features of the various claims and / or changing dependencies of claims, any such alternative embodiments and their equivalents are also within the scope of the disclosure.

Claims

1. An apparatus for use with a tribological test rig for performing tribo-dynamic measurements on a test component, the apparatus comprising:load control means configured to control an application of a radial load and an axial load on the test component, wherein the application of the radial and axial loads is controlled such that a dynamically variable radial load and a dynamically variable axial load are applied to the test component.

2. The apparatus of any previous claim, wherein the load control means is further configured to control the application of the radial and axial loads so as to apply a predetermined dynamically variable radial load simultaneously with a predetermined dynamically variable axial load.

3. The apparatus of any previous claim, wherein the load control means is further configured to control the application of the dynamically variable radial and axial loads so as to synchronise an application of a time varying radial load with an application of a time varying axial load.

4. The apparatus of any previous claim, wherein the load control means is further configured to control the application of a dynamically variable tangential load to the test component.

5. The apparatus of any previous claim, wherein the load control means is further configured to control the application of the dynamic loads to simulate one or more expected dynamic loads that would be applied to the test component if the test component were rotatably driven via one or more particular power transmission components.

6. The apparatus of any previous claim, wherein the load control means is further configured to control the application of dynamic loads so as to apply a pre-determined load profile to the test component.

7. The apparatus of claim 6, wherein the pre-determined load profile is based, at leastin part, on a pre-determined load profile of one or more of:a power transmission component,a component of a drive train,a gear,a gear pair, anda meshing helical gear pair.

8. The apparatus of claim 6 or 7, wherein the pre-determined load is configured to simulate a load profile of one or more of:a power transmission component,a component of a drive chain,a gear,a gear pair, anda meshing helical gear pair.

9. The apparatus of any previous claim, wherein the control of the application of the loads comprises controlling at least one or more of:means for directly and / or indirectly applying a radial load to the test component;means for directly and / or indirectly applying an axial load to the test component; andmeans for directly and / or indirectly applying a tangential load to the test component.

10. The apparatus of any previous claim, wherein the control of the application of the loads comprises dynamically controlling an amount of radial, axial and / or tangential load directly and / or indirectly applied to the test component by means for directly and / or indirectly applying radial, axial and / or tangential loads to the rotating structure.

11. The apparatus of any previous claim, wherein the application of the radial and axial loads is controlled such that, in use when the test component is rotating, predetermined dynamically varying radial and axial loads are applied to the rotating structure as it rotates.

12. The apparatus of any previous claim, wherein the test component is one or more of: a bearing coupled to a rotatable shaft; and a rolling element bearing.

13. The apparatus of any previous claim, wherein the apparatus is embodied in a chipset, circuitry, or module.

14. A system comprising:the apparatus of any previous claim,radial loading means configured to directly and / or indirectly apply a radial load to the test component; andaxial loading means configured to directly and / or indirectly apply an axial load to the test component.

15. The system of claim 14, further comprising tangential means configured to directly and / or indirectly apply a tangential load to the test component.

16. The system of any of claims 14 to 15, wherein the system is a tribological test rig.

17. A method for use with a tribological test rig for performing tribo-dynamic measurements on a test component, the method comprising:controlling an application of a radial load and an axial load on the test component, 5           wherein the application of the radial and axial loads is controlled such that adynamically variable radial load and a dynamically variable axial load are applied to the test component.

18. A method of performing modal testing comprising the method of claim 17.1019. Computer program comprising instructions, which when executed by at least one processor, cause the apparatus of any of previous claims 1 to 13 to perform the method of claim 17 or 18.15

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