FORM -2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE
Specification
(See Section 10; rule 13)
VARIABLE LOADING WEAR AND FRICTION MONITOR (VLWAFM) PIN-ON-DISK SLIDING TRIBOMETER
COLLEGE OF ENGINEERING, PUNE
An Autonomous Institute of Government of Maharashtra of Wellesley Road, Shivaji Nagar, Pune- 411 005, Maharashtra, India.
Inventors
1. AHUJA BHARATKUMAR BHAGATRAJ
2. PAUL SUDHIR MADHAV
3. PATIL ANANDKUMAR PANDURANG
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE DISCLOSURE
The present disclosure generally relates to tribometers.
Particularly, the present disclosure relates to variable loading wear and friction monitor (VLWAFM) pin-on-disk sliding tribometer.
BACKGROUND
Tribology is the science and engineering of interacting surfaces in relative motion. Tribology includes study and application of the principles of friction, wear and lubrication. A tribometer is an instrument/machine that measures tribological quantities, such as coefficient of friction, friction force, and wear volume, between two surfaces in contact.
Some prior art tribometers are as follows:
Stephen L. Rice [Stephen L. Rice "Reciprocating Impact Wear Testing Apparatus" (6 Dec 1976) Wear, 45 (1977) 85 - 95] discloses a reciprocating impact wear testing apparatus for study of wear occurring between solid materials undergoing repetitive impulsive loading. Such loading may be purely normal or may include simultaneous transverse sliding. The apparatus is stated to allow measurement of an impact load pulse and to provide for maintenance of repeatable force pulses for the duration of a prolonged series of impacts (millions of cycles). When utilized with a flat-nosed impacting specimen, the time invariant impulse waveform results in repeatable surface and subsurface stress cycling of materials undergoing wear. This paper stated to describe a testing apparatus and procedures and includes results from a preliminary series of tests on two polymeric materials. However, the

"Reciprocating Impact Wear Testing Apparatus" disclosed by Stephen L. Rice is not effective in measuring tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load.
F. Charles White, Sherif T. Noah, C. Fred Kettleborough and Richard B. Grifexn [F. Charles White, Sherif T. Noah, C. Fred Kettleborough and Richard B. Grifexn "An Apparatus for the study of wear under dynamic loading condition" (19 Mar 1984) Wear, 97 (1984) 179 - 197] disclose a multipurpose wear testing apparatus. The apparatus is primarily an impact wear testing device, but it may also be used for vibratory and oscillatory wear experimentation. The apparatus utilizes a versatile displacement and force controlled device that stated to allow accurate control and measurement of load cycles and their frequencies and relative normal and transverse velocities between the wear surfaces as well as their time of contact. According to work carried out by F. Charles White, Sherif T. Noah, C. Fred Kettleborough and Richard B. Grifexn, the apparatus is stated to be capable of generating, maintaining and monitoring the various significant parameters for conducting wear studies under various loading conditions, in particular those arising during impact. The apparatus can maintain particular parameters constant while others are varied. Initial testing has stated to be shown that the apparatus may allow the effects of impact velocity and internal material and system damping on wear to be investigated. The apparatus also stated to enable the system stiffness to be varied. This is particularly relevant in the presence of transverse relative sliding motion between pairs of wear specimens. However, "An Apparatus for the study of wear under dynamic loading condition" disclosed by F. Charles White et al. is not effective in measuring tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load.

Mohammad Asaduzzaman Chowdhury and Md. Maksud Helali [Mohammad Asaduzzaman Chowdhury, Md. Maksud Helali "The effect of frequency of vibration and humidity on the wear rate" (11 Nov 2005) Tribology International 39 (2006) 958-962] disclose how wear rates are affected by frequency of vibration in conjunction with relative humidity. Variation of wear rate with variation of frequency of vibration and relative humidity is investigated experimentally on a mild steel disc using pin-on-disc apparatus having facility of vibrating the disc at different frequency of vibration and amplitude. During the experiment, the effect of normal load, speed and relative humidity on wear rate were also stated to be investigated. According to work carried out by Mohammad Asaduzzaman Chowdhury, Md. Maksud Helali, the presence of vibration affects the wear considerably. Wear rate is significantly higher at no vibration (0 Hz) condition than that at vibration condition. The value of wear rate decreases with the increase of frequency of vibration. The percentage reduction of wear rate under vibrating and non-vibrating conditions increases almost linearly with increase of frequency of vibration at a particular relative humidity level. As the wear rate decreases with increasing relative humidity, therefore maintaining appropriate level of humidity and vibration wear may be kept to some lower value. However, the "pin-on-disc apparatus" disclosed by Mohammad Asaduzzaman Chowdhury and Md. Maksud Helali is not effective in measuring tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load.
Michael V. Swain and others [Naoki Fujisawa, Natalie L. James, Richard N. Tarrant, David R. McKenzie, John C. Woodard, Michael V. Swain "A Novel Pin-on Apparatus" Wear 254 (2003) 111-119] have developed a pin-on-disk apparatus that provides repetitive impact loading between periods of sliding through alternate lifting and dropping of a spring-suspended spinning disk, away from, and

onto, a spring-supported pin, respectively. The combination of the repetitive impact loading and sliding achieved in the apparatus was able to induce film adhesion failure of a thin film coated disk within 20 min, which, in the absence of the impact loading, would have survived the test due to the adequate sliding wear resistance. The impact/sliding pin-on-disk apparatus is stated to be a useful means of predicting the sliding wear resistance and film adhesion of a coated system simultaneously. A repetitive impact loading between periods of continuous sliding was stated to be effective in a pin-on-disk apparatus for testing simultaneously both the sliding wear resistance, and film adhesion of a coated system. The repetitive impact loading generated by the apparatus was able to promote adhesion failure of a thin film coating applied on a titanium alloy disk. This coating would have survived the test within the 20 min test period in the absence of repetitive impact loading due to its low friction coefficient and adequate sliding wear resistance. The mechanism of film adhesion failure involved initial local de-bonding of the film at discrete regions along the sliding path, where repetitive pin/disk contact occurred, and subsequent removal of the bulged coating by the frictional force exerted by the sliding pin. However, "A Novel Pin-on Apparatus" disclosed by Michael V. Swain and others is not effective in measuring tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load.
Some prior art patent documents are as follows:
For example, US Patent Number US7045489 discloses an Amsler machine consisting of two parallel discs being run by each other with variable loads being applied against the two discs. This apparatus is designed to stimulate two steel surfaces in sliding-rolling contact. The discs are geared so that the axle of one disc runs about 10% faster than the other. By varying the diameter of the discs,

different creep levels can be obtained. The torque caused by friction between the discs is measured and the coefficient of friction is calculated from the torque measurements. Sliding friction characteristics of a composition in the field, may be determined using for example but not limited to, a push tribometer or TriboRailer (H. Harrison, T. McCanney and J. Cotter (2000), Recent Developments in COF Measurements at the Rail/Wheel Interface, Proceedings The 5th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems CM 2000 (SEIKEN Symposium No. 27), pp. 30-34,). However, the push tribometer or TriboRailer .or the Amsler machine disclosed by the US Patent Number US7045489 is not effective in measuring tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load.
Further, US publication number US20040092407 discloses a liquid friction control composition for use in low temperature conditions, which comprises a rheological control agent, a consistency modifier and a freezing point depressant. The liquid friction control composition may also comprise other components such as a retentivity agent, an antioxidant, a friction modifier, a lubricant, a wetting agent, and a preservative. Also, US publication number US20040092407 discloses a push tribometer. However, the push tribometer disclosed by the US publication number US20040092407 is not effective in measuring tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load .
Furthermore, US Patent Number US7244695 discloses a method of reducing wear of one or both of two steel elements having surfaces in sliding or sliding-rolling contact. The method involves applying an HPF friction control composition to one, or more than one contacting surface of one or both of the two steel elements.

In a particular example, the HPF friction control composition comprises a rheological control agent, a lubricant, a friction modifier, and one, or more than one of a retentivity agent, an antioxidant, a consistency modifier, and a freezing point depressant. However, the US Patent Number US7244695 discloses only method of reducing wear of one or both of two steel elements having surfaces in sliding or sliding-rolling contact and not a tribometer.
Also, US publication number US20050287187 discloses hydrogel devices for surgical implantation to replace damaged cartilage in a mammalian joint (such as a knee, hip, shoulder, etc.) are disclosed, with one or more of the following enhancements: (1) articulating surfaces that have been given negative surface charge densities that emulate natural cartilage and that interact with positively charged components of synovial fluid; (2) anchoring systems with affixed pegs that will lock into accommodating receptacles, which will be anchored into hard bone before the implant is inserted into a joint; (3) a three-dimensional reinforcing mesh made of strong but flexible fibers, embedded within at least a portion of the hydrogel. However, the US publication number US20050287187 discloses hydrogel devices and not a tribometer.
Moreover, WIPO publication number WO 1998041576 discloses conducting of Friction, wear and PV-limit tests with a Pin-on-disk tribometer having a horizontal rotating disc. The rotation diameter of the test pin against the disc was 58 + 1 mm. The plastic pin to be tested was loaded with weights at the end of a lever arm. Before the test, the test pins and the steel disc were cleaned carefully with alcohol. All of the tests were conducted in a conditioned room having a temperature of 20 °C and a relative humidity of 50%, without using an external lubricant. The specimens were kept in the same room during the testing. However, the "Pin-on-disk tribometer" disclosed by the WIPO publication number WO 1998041576 is

not effective in measuring tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load.
Accordingly, as illustrated above various experimental setups are available to study tribological behavior of materials under different types of loading such as a constant load, an impact load and vibrations. However, none of the prior art apparatus/ experimental setups facilitate study of tribological behavior of material under variable loading such as a repeated load, a fluctuating load and a superimposed load.
Further, -now-a-days most of the tests are carried out with constant loading situation, however the loading condition in practice is never constant and some variation of load is always there. Further, in all sliding applications even though it is considered that the load acting is constant, there is actually some variation in load during operation and hence it is necessary to consider the effect of variable loading conditions while studying the friction and wear behavior of materials.
Accordingly, there is need of a tribometer that measures tribological quantities between two surfaces in sliding contact under variable loading. Also, there is need of a tribometer that facilitates study of wear and friction characteristics of materials in sliding contacts both in dry and lubricated test conditions under variable loading.
OBJECTS
Some of the objects of the system of the present disclosure which at least one embodiment herein satisfies are as follows:

It is an object of the system of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the system of the present disclosure is to provide an experimental or test set-up to facilitate study of friction and wear behavior of different industrial materials operating in a sliding mode (i.e. rubbing between two surfaces).
Another object of the system of the present disclosure is to provide a tribometer that measures tribological quantities between two surfaces in sliding contact under variable loading conditions.
Further, an object of the system of the present disclosure is to provide a tribometer that facilitates study of wear and friction characteristics of materials in sliding contacts both in dry and lubricated test conditions under variable loading.
Also, an object of the system of the present disclosure is to provide an experimental or test set-up to facilitate study of friction and wear behavior of different industrial materials operating under sliding mode (i.e. rubbing between two surfaces) subjected to variable loading conditions with different frequencies (constant and variable).
Other objects and advantages of the system of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.

SUMMARY
In accordance with one. aspect of the present disclosure, a variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer is disclosed. The VLWAFM pin-on-disk tribometer includes a spindle assembly, a loading lever assembly and a variable loading assembly. The spindle assembly is adapted to hold and rotate a wear disc. The loading lever assembly includes a loading lever and a specimen holder. The specimen holder is connected to a first end of the loading lever. The specimen holder is disposed over the wear disc. The specimen holder is adapted to hold a specimen stationary therein. The specimen is in contact with the rotating wear disc and configures sliding motion there between. The variable loading assembly includes a transmission mechanism, at least one radial disc cam and a follower assembly. The at least one radial disc cam is disposed on a splined shaft. The splined shaft is rotated by the transmission mechanism, wherein splines on the splined shaft facilitate movement of the at least one radial disc cam along a shaft axis of the splined shaft. The follower assembly includes a flat faced follower, an adjustable lock nut, a helical compression spring and a spring housing. The flat faced follower is adapted to be in contact with the at least one radial disc cam and configures motion based on profile of the at least one radial disc cam. The flat faced follower has a threaded arm. The adjustable lock nut is disposed on an operative lower portion of the threaded arm. The helical compression spring is functionally connected to the flat faced follower and the adjustable lock nut and adapted to get compressed and de-compressed by movement of the flat faced follower. The spring housing accommodates the helical compression spring therein. The housing is disposed over the loading lever for transmitting variable load from the variable loading assembly to the specimen. The specimen exerts variable load on the rotating wear disc for facilitating measurement of tribological parameters between the specimen and the rotating wear disc under variable loading condition.

Typically, the transmission mechanism includes an AC motor and a variable frequency drive (VFD).
Typically, a proximity sensor is disposed on the splined shaft to measure the rotational speed of the at least one radial disc cam/ the splined shaft.
In one embodiment, a plurality of spring housing locators is adapted to adjust position of the housing in a way such that the threaded arm is inline with the axis of the helical compression spring.
In one embodiment, a plurality of spring housing holders is adapted to hold the housing firmly to avoid its movement due to tangential force exerted by the at least one radial disc cam on the flat faced follower.
A thrust reducing mechanism may be disposed between the operative lower portion of the housing and the loading arm for reducing effect of tangential load on the loading arm.
Typically, the variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer includes a controller with a data acquisition system.
Typically, a frame structure facilitates mounting of various components of the variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer thereon.
In one embodiment, the spindle assembly includes a spindle, a taper roller bearing, a wear disc holder, a proximity sensor disc and a proximity sensor. The taper roller bearing is adapted to house the spindle. The wear disc holder is connected to an

operative top portion of the spindle, wherein the wear disc holder is adapted to hold the wear disc thereon. The proximity sensor disc is connected to an operative bottom portion of the spindle. The proximity sensor is disposed on the proximity sensor disc and adapted to measure speed of the spindle.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The variable loading wear and friction monitor (VLWAFM), pin-on-disk sliding tribometer of the present disclosure will now be explained in relation to the non-limiting accompanying drawings, in which:
Figure 1 illustrates a schematic representation of a prior art "Reciprocating Impact Wear Testing Apparatus" disclosed by Stephen L. Rice;
Figure 2 illustrates a schematic representation of a prior art "An Apparatus for the study of wear under dynamic loading condition" disclosed by F. Charles White et al.;
Figure 3 illustrates a schematic representation of a prior art experimental set up of an apparatus having facility of vibrating the disc at different amplitude and frequency disclosed by Mohammad Asaduzzaman Chowdhury and Md. Maksud Helali;
Figure 4 illustrates a schematic representation of a prior art experimental set up of "A Novel Pin-on Apparatus" disclosed by Michael V. Swain and others;

Figure 5a illustrates a front view of Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer, in accordance with one embodiment of the present disclosure;
Figure 5b illustrates a side view of the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of Figure 5a;
Figure 6 illustrates a machine layout of the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of Figure 5 a;
Figure 7 illustrates a perspective view of the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of Figure 5a;
Figure 8 illustrates another perspective view of the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of Figure 5a;
Figures 9a and 9b illustrate perspective views of a follower mechanism of the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of Figure 5 a;
Figure 10 illustrate a perspective view of a frame structure of the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of Figure 5a;
Figure 11 illustrates yet another perspective view of the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of Figure 5 a;

Figure 12 illustrates a perspective view 0f a pin-on-disk tribometer for constant loading;
Figure 13 illustrates a schematic representation of a spindle assembly of the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of Figure 5 a;
Figure 14 illustrates a perspective view of a loading lever assembly of the Variable Loading Wear and Friction Monitor (VL WAFM) pin-on-disk tribometer of Figure 5a;
Figure 15 illustrates a perspective view 0f a disc assembly and a loading lever assembly of the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of Figure 5a;
Figure 16 illustrates a perspective view 0f a thrust reducing mechanism of the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of Figure 5 a;
Figure 17 illustrates a schematic representation of a wear track adjusting sliding plate assembly of the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of Figure 5a;
Figure 18 illustrates a perspective vievv of a lubrication -unit of the Variable Loading Wear and Friction Monitor (VL WAFM) pin-on-disk tribometer of Figure 5a;
Figure 19 illustrates a schematic representation of a loading lever;

Figure 20 illustrates a graph depicting comparison of coefficient of friction under constant and variable loading;
Figure 21 illustrates a graph depicting comparison of PTFE wear under constant and variable loading; and
Figure 22 illustrates a graph depicting wear behavior of PTFE under different dynamic loading frequencies compared with corresponding maximum and minimum limit of constant load conditions.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The variable loading wear and friction monitor (VLWAFM), pin-on-disk sliding tribometer of the present disclosure will now be described with reference to the accompanying drawings which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The description hereinafter, of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current

knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Referring to Figure 1, a schematic representation of a prior art "Reciprocating Impact Wear Testing Apparatus" disclosed by Stephen L. Rice is illustrated. The "Reciprocating Impact Wear Testing Apparatus" illustrates apart from other components a motor 20, a power unit 30, an oscilloscope 40 and a control circuit 50. However, the "Reciprocating Impact Wear Testing Apparatus" disclosed by Stephen L. Rice is not effective in measuring tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load.
Referring to Figure 2, a schematic representation of a prior art "An Apparatus for the study of wear under dynamic loading condition" disclosed by F. Charles White et al is illustrated. However, "An Apparatus for the study of wear under dynamic loading condition" disclosed by F. Charles White et al. is not effective in measuring tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load.

Referring to Figure 3, a schematic representation of a prior art experimental set up of an apparatus having facility of vibrating the disc at different amplitude and frequency disclosed by Mohammad Asaduzzaman Chowdhury and Md. Maksud Helali is illustrated. The experimental set up includes a load arm holder 1, a load arm 2, a normal load 3, a horizontal load 4, a pin sample 5, a test disc with rotating table 6, a computer 7, a belt and pulley assembly 8, a main shaft 9, a motor 10, a compressing spring 11, a mechanism for generating vertical vibration 12, a height adjustable screw 13 and a base plate with foundation 14. However, the "pin-on-disc apparatus" disclosed by Mohammad Asaduzzaman Chowdhury and Md. Maksud Helali is not effective in measuring tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load.
Referring to Figure 4, a schematic representation of a prior art experimental set up of "A Novel Pin-on Apparatus" disclosed by Michael V. Swain and others is illustrated. "A Novel Pin-on Apparatus" includes a micrometer drive 62, a single-axis translation stage 64, a solenoid 66, a solenoid pin 68, a guide-rail 70 of the bearing behind the motor, an extension spring 72, a DC servo motor 74, an extension shaft 76, second accelerometer position 78, a compression spring 80, a load cell 82, first accelerometer position 84, a pin 86, a disk 88, a disk holder 90 and a bearing and bearing shaft assembly 92. However, "A Novel Pin-on Apparatus" disclosed by Michael V. Swain and others is not effective in measuring tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load.
Accordingly, to alleviate the limitations of the prior arts, the present disclosure provides a Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk

tribometer. A Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer of the present disclosure facilitates measurement of tribological quantities between two surfaces in sliding contact under variable loading such as a repeated load, a fluctuating load and a superimposed load at different frequencies (constant and variable). Also, a VLWAFM pin-on-disk tribometer of the present disclosure facilitates measurement of tribological quantities between two surfaces in sliding contact under application of constant load. Further, a VLWAFM pin-on-disk tribometer of the present disclosure facilitates study of wear and friction characteristics of materials in sliding contacts both in dry and lubricated test conditions under variable loading. Accordingly, a VLWAFM pin-on-disk tribometer of the present disclosure facilitates study/ analysis of the actual load variation and provides an opportunity to test materials under realistic variable loading condition such as a repeated load, a fluctuating load and a superimposed load.
Referring to Figures 5a to 22, a VLWAFM pin-on-disk tribometer 100 for sliding wear of the present disclosure includes a frame structure 200, a spindle assembly 300, a loading lever assembly 400 and a variable loading assembly 500.
Referring to Figures 5 a, 5b, 6 , 7, 8 10 and 11, the frame structure 200 is adapted to facilitate mounting of various components of the variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer 100 thereon. In one embodiment, the frame structure 200 includes MS tubes and hollow rectangular bars welded to form homogeneous structure which form a base of the tribometer 100 and also provides support for mounting a transmission system consisting of an AC motor with Variable Frequency Drive (VFD) which facilitates variation in rotation speed of a wear disc through the spindle assembly 300. In one embodiment, the frame structure 200 can be made of two parts which can be

assembled depending on the test conditions. One part is related to testing under constant loading and second part along with first part is related to testing under variable loading conditions. The frame structure 200 also includes a motor and a VFD stand 208 (illustrated in Figures 5a, 7 and 10) and a side support 210 (illustrated in Figures 5a and 10).
Referring to Figure 13, the spindle assembly 300 is driven by an AC motor 302. The power from the AC motor 302 is transferred to the spindle assembly 300 by means of a pulley 304 and a teethed belt 306 arrangement. In one embodiment, the spindle assembly 300 includes a spindle (not shown), a taper roller bearing (not shown), a wear disc holder (not shown), a proximity sensor disc (not shown) and a proximity sensor (not shown). The taper roller bearing is adapted to house the spindle. The spindle is mounted firmly on bottom of a base plate 208 (illustrated in Figure 17) of the frame structure 200 through housing. The wear disc holder is connected to an operative top portion of the spindle. The wear disc holder is adapted to hold a wear disc 308 (illustrated in Figures 7 and 15) thereon. In one embodiment, the wear disc holder is adapted to hold the wear disc thereon by screws. The proximity sensor disc is connected to an operative bottom portion of the spindle. Also, at bottom of the spindle a driven pulley is fitted. The proximity sensor is disposed on the proximity sensor disc and adapted to measure speed of the spindle. In one embodiment of the present disclosure, the proximity sensor is fixed perpendicular to the proximity sensor disc.
Referring to Figure 14, the loading lever assembly 400 includes a loading lever 402 and a specimen holder 404. The loading lever is made of a single bar with the specimen holder 404 fixed at a first end and at other end a wire rope and pulley assembly 406 is attached. In one embodiment, the pivot point of lever is fixed at the middle to get 1: 1 loading lever ratio. A specimen 408 to be tested is fitted to

the specimen holder 404 by clamping on hardened jaws 410, separate jaws are provided for pin. The specimen holder 404 is disposed over the wear disc 308. The specimen holder 404 is adapted to hold the specimen 408 stationary therein. The specimen 408 being in contact with the rotating wear disc 308 and configures sliding motion there between.
Referring to Figures 5a to 11 and Figure 16, the variable loading assembly 500 includes a transmission mechanism 502 (illustrated in Figure 6), radial disc cams 504 and a follower assembly 506. The transmission mechanism 502 includes an AC motor 522 (illustrated in Figure 5b) controlled by a Variable Frequency Drive (VFD) 526 (illustrated in Figure 6). The radial disc cam 504 is disposed on a splined shaft 508. The splined shaft 508 is rotated by the transmission mechanism 502. The splined shaft 508 is rotated by the transmission mechanism 502 by means of teethed pulley and belt arrangement 524. Splines on the splined shaft 508 facilitate movement of the radial disc cams 504 along a shaft axis of the splined shaft 508 so that the plane of rotation of the cams 504 and direction of reciprocation of the follower assembly 506 should be inline. In one embodiment, a proximity sensor 536 (illustrated in Figure 6) is disposed on the splined shaft 508 to measure the rotational speed of the radial disc cam 504/ the splined shaft 508. The rotational speed of the radial disc cam 504/ the splined shaft 508 is related with frequency of variable loading. .
Referring to Figures 9a and 9b, the follower assembly 506 includes a flat faced follower 510, an adjustable lock nut 512, a helical compression spring 514 and a spring housing 516. The flat faced follower 510 is adapted to be in contact with the radial disc cam 504 and configures motion based on profile of the radial disc cam 504. More specifically, the radial disc cam 504 operates the flat faced follower 510. The flat faced follower 510 has a threaded arm 518. The adjustable

lock nut 512 is disposed on an operative lower portion of the threaded arm 518. The adjustable lock nut 512 is in contact with the top portion of the helical compression spring 514. The adjustable lock nut 512 facilitates adjustment of height of the follower assembly 506 to maintain contact between the radial disc cam 504 and the flat faced follower 510. Also, the adjustable lock nut 512 is adapted to facilitate initial compression in the helical compression spring 514 to facilitate initial non-zero loading on the wear disc 308.
The helical compression spring 514 is functionally connected to the flat faced follower 510 and the adjustable lock nut 512 and adapted to get compressed and de-compressed by movement of the flat faced follower 510. The spring housing 516 is adapted to accommodate the helical compression spring 514 therein. The housing 516 is disposed over the loading lever 402 for transmitting variable load from the variable loading assembly 500 to the specimen 408 (illustrated in Figures 11,15 and 16). The specimen 408 is adapted to exert variable load on the rotating wear disc 308 for facilitating measurement of tribological parameters between the specimen 408 and the rotating wear disc 308 under variable loading condition.
In one embodiment, the variable loading assembly 500 includes a plurality of spring housing locators/ C-clamps 534 (illustrated in Figures 5a and 6) adapted to adjust position of the housing 516 in a way such that the threaded arm 518 be inline with the axis of the helical compression spring 514. Also, the plurality of spring housing locators/ C-clamps 534 facilitates support to the spring housing 516. All adjustments are provided to the cam 504 through splines, the spring 514 through locators 534 are required whenever wear track diameter is changed.
In one embodiment, the variable loading assembly 500 includes a plurality of spring housing holders (not shown) adapted to hold the housing 516 firmly to

avoid its movement due to tangential force exerted by the radial disc cam 504 on the flat faced follower 510. The movement of the housing 516 due to tangential force exerted by the radial disc cam 504 on the flat faced follower 510 ultimately acts on the specimen holding arm 404 and hence to eliminate its effect a thrust reducing mechanism 600 (illustrated in Figure 16) is provided between the operative lower portion of the housing 516 and the loading arm 404 for reducing effect of tangential load on the loading arm 404. In one embodiment, the thrust reducing mechanism 600 includes balls sandwiched between the spring housing 516 and the loading arm 404. Further, in one embodiment the thrust reducing mechanism 600 includes a U-clamp 530 (illustrated in Figure 5b).
Further, the variable loading assembly 500 includes a plummer block 528 (illustrated in Figure 5b) for facilitating support to the splined shaft 508.
Referring to Figure 17, in one embodiment, the VLWAFM pin-on-disk tribometer 100 includes a wear track diameter adjusting sliding plate assembly 700. The loading lever assembly 400, a pulley for loading pan, sensors for wear and frictional force, such as a linear variable differential transformer (LVDT) 704 and a frictional force load cell 706, are mounted on the sliding plate assembly 700. The sliding plate assembly 700 moves over a base plate 208 to set wear track diameter using a graduated scale 702 (illustrated in Figure 15). The assembly 700 movement is guided by two guiding rails fixed on the base plate 208. An adjusting block fixed on the sliding plate facilitates to set specimen height properly. A wire rope from the loading lever passes over the pulley and at the end a loading pan is hung. Normal constant load is applied by placing dead weights on loading pan.
Referring to Figure 18, a lubricating unit 800 is disclosed. The lubricating unit 800 facilitates study of wear and friction characteristics of materials in sliding contacts

in lubricated test conditions. The lubricating unit 800 includes a lubricating tank 802, an outlet pipe 804, a motor 806, a pump and an inlet pipe. The inlet pipe supplies oil near to the specimen 408 through polyurethane tube and the outlet pipe 804 carries used oil to tank for recirculation.
Further, in one embodiment, the VLWAFM pin-on-disk tribometer 100 includes a plurality of sensors, such as sensors 902 (illustrated in Figure 12). Figure 12 illustrates a pin-on-disk tribometer for constant loading. When the variable loading assembly 500 is removed from the Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer 100, the pin-on-disk tribometer for constant loading is formed. The pin-on-disk tribometer for constant loading also discloses an on-off switch 904 and an environmental chamber 906. The plurality of sensors monitors wear and the tangential force of friction as a function of normal load. Also, the VLWAFM pin-on-disk tribometer 100 includes sensors for sensing various operating parameters such as speed, temperature, pressure, load and the like.
Sliding occurs between stationary pin (specimen) and a rotating disc (counter face). Depending on the test requirement different specimen material and counter face material combinations can be tested by manufacturing the specimen and rotating counter face disc of required material.
Normal load (constant as well as variable), rotational speed of the disc, wear track diameter, and frequency of variable loading can be varied as required for the test condition. The variable loading range corresponding to different variable loading factor or dynamic loading coefficient can be obtained as per the required test condition.

The instantaneous Normal Load, Tangential frictional force and wear are monitored and recorded with electronic sensors. The coefficient of friction is obtained by dividing the frictional force with instantaneous normal load. The wear is monitored based on height loss principal by measuring the wear height of the specimen by means of an electronic sensor.
Furthermore, in one embodiment, the VLWAFM pin-on-disk tribometer 100 includes a controller with a data acquisition system. The data acquisition system facilitates measurement and record of input parameters and their responses.
The VLWAFM pin-on-disk tribometer 100 of the present disclosure facilitates tests under:
(i) constant loading condition (ii) repeated loading condition (iii) fluctuating loading condition (iv) superimposed loading condition
The above loading situations can be tested by using the cams of different lift or stroke. Same cam and spring can be used for obtaining different dynamic coefficient.
Tests can be carried out for wide range of variation in loading (by considering a factor as 'variable loading factor') by changing the spring and cam combination (i.e. by changing the spring stiffness and cam lift).
Further, tests can be carried out for wide range of frequencies of variable loading by changing the input speed of variable loading assembly.

Some of the industrial applications of the VLWAFM pin-on-disk tribometer 100 of the present disclosure include in the study, analysis and construction of the sliding contact bearings, guide ways used in machine tools/supporting secondary equipments operating over long distance.
Test Analysis
Introduction:
The Variable Loading Friction And Wear Monitor (VLWAFM) Pin-on-Disk Sliding Tribometer 100 of the present disclosure is a versatile unit constructed to evaluate the Wear and Friction characteristics of variety of materials exposed to sliding contacts in dry or lubricated environments under variable loading. The sliding friction test occurs between a stationary pin and a rotating disc. Electronic sensors monitor wear and the tangential force of friction as a function of normal load. Input parameters and .responses are measured and recorded using the data acquisition system which can be used to plot graphs as required to study the interrelationship between variables.
Parameters: Normal load (constant or variable), contact pressure, rotational speed, sliding speed, wear track diameter, sliding time, dynamic load coefficient (ratio of maximum load to minimum load), dynamic loading frequency.
Response: Frictional force, coefficient of friction, wear height and specific wear rate.

Experimental set up:
The apparatus consists of a rotating disc made of Steel (EN 31) of diameter 165 mm which forms the counter face on which the test specimens slide over. Cylindrical test specimens of diameter 10 mm and length 31 mm of Poly Tetra Fluoro Ethylene (PTFE) material were used. The specimens were clamped tightly in the specimen holder and held against the rotating steel disc.
The operation of pin-on-disk is made user friendly by arranging controls on the controller.
The controls for operation are
Wear - To be set to zero before start of
operation
Frictional Force - To be set to zero before start of
operation
Speed - To select speed of the disc
Timer - To control test duration
Start-Stop - To start or stop the disc rotation
VFD Start-Stop - To Start Stop input to the Dynamic
Loading Mechanism
VFD Speed controller - To Set the Frequency of Dynamic
loading through RPM of the Cam.

Steps for Test:
• Place the specimen in the specimen holder (collate) and adjust the height of the pin by using adjustment block
• Tight the clamping screws
• Swivel the adjustment block away from loading arm
• Set required track radius
• Place test weight in the loading pan
• Set the required cam by sliding on the splined shaft
• Set the required Frequency of the dynamic loading by setting the rpm on VFD
• Start the DAQ system
• In the cell for sample ID ,enter the material of the specimen
• In the cell for speed ,enter speed and test duration
• In the remarks cell enter load applied track radius duration of test etc.
• Click ACQUIRE button
• To start the test
o Click start button on Controller o Click start button on VFD
• To stop the test
o Click stop button on controller o Click stop button on VFD
Table 1: Key Specifications for VLWAFM Pin-on-Disk Sliding Tribometer

Sr.No Parameter Units and Remarks
1 Sliding speed range 0.5 to lOm/sec
2 Wear Track Diameter 165 mm max.
3 Disc rotation speed 200 to 2000 rpm
4 Normal Constant Load 0.5 kg to 20 kg Range, in steps of 100 gm
5 Dynamic loading coefficient* or Range of variable load Can be varied by using different combinations of cam lift and stiffness of spring.

6 Dynamic loading frequency 0.5Hz to 20Hz
7 Frictional force Least count 0.1 N. Accuracy O.lto 0.2 %
8 Wear Range +2mm, Least count lmicron, Accuracy 1%
9 Lubrication system Discharge 0.5 Lit/min, oil capacity 3 Liter
10 Test duration 0to99hrs,59min,59sec 0 to 999999 rev.
Dynamic Loading Coefficient = Maximum Load Applied/Minimum Load Applied
Calculation of Dynamic loading coefficient:
Referring to Figure 19, point A indicates location of pin, point B indicates the location of spring where the variable load is acting, point C is the fulcrum point and at point D one end of the rope of loading pan (used to apply constant load only) is connected which then passes over the pulley and holds loading pan.
For 5mm cam lift:
Initial compression in the spring during the dwell period of the cam is zero.
The maximum compression in the spring is 5mm per cam revolution due to cam lift of 5 mm. Spring stiffness = 4.15 N/mm Load acting on arm, F = Kx Where, F = Force K = Spring stiffness x = Spring deflection
F = 4.15X5 = 20.75 N = 2.11 Kg. (Force acting on point 'B' in Figure 19)


Therefore, force acting on specimen at point 'A' through spring and cam is
In experiment the static load 0.8 Kg is kept constant and is placed in the loading pan.
Therefore total maximum load acting on specimen i.e. at point 'A' = 1.44 + 0.8 = 2.24 Kg

= 2.8 Similarly,
For cam lift 10mm, Dynamic loading coefficient = 4.62 For cam lift 15mm, Dynamic loading coefficient = 6.42

where, D = Dia. of track (mm). N = Rotational speed of disc (rpm). V = Sliding Velocity (m/s)

Table 2: Calculation of RPM

Sr. No Sliding Velocity (m/s) Track Diameter
(mm) (N) (rpm)
1 0.5 110 87
2 1.0 110 174
3 1.5 110 261
Objective of the Test:
To compare the wear and friction behavior of the material under variable loading (fluctuating loading) at different frequencies to that with corresponding minimum and maximum constant loads.
Minimum constant load is 0.8 Kg whereas maximum constant load is 3.7Kg correspond to this the dynamic loading coefficient is 4.62.
Different experiments are carried out for different frequencies of variable loading with following test parameters being constant:
Table 3: Details of parameters which are kept constant during variable loading
experiment

Sr. No. Parameter Value
1 Dynamic coefficient 4.62
2 Time (min.) 45
3 Velocity (m/s) 1

Table 4: Observational data of PTFE on VLWFM Pin -On-Disk setup with different
dynamic loading frequency condition

Sr. No. Dynamic loading Frequency(Hz) Cam rotation speed (rµm) Wear (µm) Coefficient of friction (µ)
1 0.5 30 438 0.935/4.62 = 0.202
2 1 60 403 1.040/4.62 = 0.225
3 2 120 479 0.966/4.62 = 0.209
4 3 180 352 0.993/4.62 = 0.215
5 4 240 360 0.996/4.62 = 0.215
6 5 300 376 0.837/4.62 = 0.181
7 6 360 410 0.940/4.62 = 0.203
8 7 420 457 0.987/4.62 = 0.213
The data acquisition system has recorded the coefficient of friction by dividing the actual frictional force with minimum load and it is suggested that dividing this value by dynamic coefficient to get the average coefficient of friction during the operation.
Table 5: Observational data of PTFE on VLWFM Pin -On-Disk setup with constant
loading

Sr.
No. Static load (Kg) Wear
(µm) Coefficient of Friction (µ)
1 0.8 140 0.270
2 3.7 550 0.228
From the results of coefficient of friction obtained in Table 4 and Table 5 it is observed that the value of coefficient of friction under variable loading is less or equal to that of corresponding maximum limit of constant load condition.
Figure 20 illustrates a graph depicting comparison of coefficient of friction under constant and variable loading. The graph depicts variation of Coefficient of Friction (Y axis) with respect to Time in seconds (X axis). The line "A" represents variation at 1 Hz frequency, the line "B" represent variation at 0.3 Hz

frequency, the line "C" represents variation at Minimum static frequency and the line "D" represents variation at Maximum static frequency.
Figure 21 illustrates a graph depicting comparison of wear under constant and variable loading. The graph depicts variation of Wear in micrometers (Y axis) with respect to Time in seconds (X axis). The line "E" represents variation at Minimum static frequency, the line "F" represent variation at 0.3 Hz frequency, the line "G" represent variation at 1 Hz frequency and the line "H" represents variation at Maximum static frequency.
Figure 22 illustrates a graph depicting wear behavior of PTFE under different dynamic loading frequencies compared with corresponding maximum and minimum limit of constant load conditions. The graph depicts variation of Wear in micron (Y axis) with respect to Frequency in Hz (X axis). The line "I" represents variation at Minimum static frequency, the line "J" represent center line, the line "K" represent wear at different frequency and the line "L" represents variation at Maximum static frequency.
Referring to Table 4, Table 5 and Figure 22 it is clear that wear at different dynamic loading frequencies lies between the wear observed under minimum and maximum static loading condition but it is above mean line of the static conditions.
Conclusions:
The VLWAFM pin-on-disk sliding tribometer can be used to
S Compare coefficient of friction and wear of the material under variable
>
loading with that of corresponding maximum and minimum limit of constant load conditions or mean constant loading condition.

Study the effect of frequency (constant and variable) of variable loading on wear and friction behavior of the materials
TECHNICAL ADVANCEMENTS AND ECONOMICAL SIGNIFICANCE
The technical advancements offered by the system of the present disclosure which add to the economic significance of the disclosure include the realization of:
• a Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer that facilitates study of friction and wear behavior of different industrial materials operating under sliding mode (i.e. rubbing between two surfaces);
• a Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer that measures tribological quantities between two surfaces in sliding contact under variable loading conditions;
• a Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer that facilitates study of wear and friction characteristics of materials in sliding contacts both in dry and lubricated test conditions under variable loading conditions; and
• a Variable Loading Wear and Friction Monitor (VLWAFM) pin-on-disk tribometer that facilitates study of friction and wear behavior of different industrial materials operating under sliding mode (i.e. rubbing between two surfaces) subjected to variable loading conditions with different frequencies.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

We claim:
1. A variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer comprising:
• a spindle assembly adapted to hold and rotate a wear disc,
• a loading lever assembly comprising,
o a loading lever,
o a specimen holder connected to a first end of said loading lever, said specimen holder disposed over said wear disc, said specimen holder adapted to hold a specimen stationary therein, wherein said specimen being in contact with said rotating wear disc and configures sliding motion there between; and
• a variable loading assembly comprising,
o a transmission mechanism;
o at least one radial disc cam disposed on a splined shaft, said splined shaft being rotated by said transmission mechanism, wherein splines on said splined shaft facilitates movement of said at least one radial disc cam along a shaft axis of said splined shaft; and
o a follower assembly comprising,
■ a flat faced follower adapted to be in contact with said at least one radial disc cam and configures motion based on profile of said at least one radial disc cam, said flat faced follower having a threaded arm;
■ an adjustable lock nut disposed on an operative lower portion of said threaded arm;
■ a helical compression spring functionally connected to said flat faced follower and said adjustable lock nut and adapted to get compressed and de-compressed by movement of said flat faced follower; and
■ a spring housing for accommodating said helical compression spring therein, wherein said housing being

[
disposed over said loading lever for transmitting variable load from said variable loading assembly to said specimen, wherein said specimen exerts variable load on said rotating wear disc for facilitating measurement of tribological parameters between said specimen and said rotating wear disc under variable loading condition.
2. The variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer as claimed in claim 1, wherein said transmission mechanism comprises an AC motor and a variable frequency drive (VFD).
3. The variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer as claimed in claim 1, further comprising a proximity sensor disposed on said splined shaft to measure the rotational speed of said at least one radial disc cam/ said splined shaft.
4. The variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer as claimed in claim 1, further comprising a plurality of spring housing locators adapted to adjust position of said housing in a way such that said threaded arm be inline with the axis of said helical compression spring.
5. The variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer as claimed in claim 1, further comprising a plurality of spring housing holders adapted to hold said housing firmly to avoid its movement due to tangential force exerted by said at least one radial disc cam on said flat faced follower.
6. The variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer as claimed in claim 1, further comprising a thrust reducing mechanism disposed between said operative lower portion of said housing and said loading arm for reducing effect of tangential load on said loading arm.

7. The variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer as claimed in claim 1, further comprising a controller with a data acquisition system.
8. The variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer as claimed in claim 1, further comprising a frame structure for facilitating mounting of various components of said variable loading wear and friction monitor (VLWAFM) pin-on-disk tribometer thereon.
9. The variable loading wear and friction monitor (VLWAFM) pin-on-disk
tribometer as claimed in claim 1, wherein said spindle assembly comprises,
• a spindle;
• a taper roller bearing adapted to house said spindle;
• a wear disc holder connected to an operative top portion of said spindle, wherein said wear disc holder being adapted to hold said wear disc thereon;
• a proximity sensor disc connected to an operative bottom portion of said spindle; and
• a proximity sensor disposed on said proximity sensor disc and adapted to measure speed of said spindle.