The authors would like to acknowledge Tim Krantz from NASA Glenn and Duane Detwiler from Honda R&#38;D for their technical support and in-kind contributions. Financial support for this research was provided by the member organizations of the Smart Vehicle Concepts Center (www.SmartVehicleCenter.org), a National Science Foundation Industry/University Cooperative Research Center (I/UCRC). S.D. is supported by a Smart Vehicle Concepts Graduate Fellowship and a University Fellowship from The Ohio State University Graduate School.

1. Development of the Modified Tribometer
<ol>
	<li>Install chuck-motor subsystem.
	<ol>
		<li>Level vibration isolation table. Place DC motor on the table; level the motor with shims and fix it with struts and bolts. Place support frame around the motor.</li>
		<li>Connect splined shaft to the motor shaft using a key. Put support plate on the frame with the splined shaft going through the hole in the plate. Set thrust needle-roller bearing on the support plate and around the splined shaft. Lubricate the bearing with c...

<ol>
	<li>Bhushan, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Introduction to tribology. , (2002).</li><li>Severdenko, V., Klubovich, V., Stepanenko, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Ultrasonic rolling and drawing of metals. , (1972).</li><li>Taylor, R., Coy, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+fuel+efficiency+by+lubricant+design:+a+review.">Improved fuel efficiency by lubricant design: a review.</a> Proc. Instit. Mech. Eng., Part J: J Eng. Tribol. 214 (1), 1-15 (2000).</li><li>Littmann, W., Storck, H., Wallaschek, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sliding+friction+in+the+presence+of+ultrasonic+oscillations:+superposition+of+longitudinal+oscillations.">Sliding friction in the presence of ultrasonic oscillations: superposition of longitudinal oscillations.</a> Arch. Appl. Mech. 71 (8), 549-554 (2001).</li><li>Littmann, W., Storck, H., Wallaschek, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduction+in+friction+using+piezoelectrically+excited+ultrasonic+vibrations.">Reduction in friction using piezoelectrically excited ultrasonic vibrations.</a> Proc. SPIE. 4331, (2001).</li><li>Bharadwaj, S., Dapino, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+control+in+automotive+seat+belt+systems+by+piezoelectrically+generated+ultrasonic+vibrations.">Friction control in automotive seat belt systems by piezoelectrically generated ultrasonic vibrations.</a> Proc. SPIE. 7645, 7645E (2010).</li><li>Bharadwaj, S., Dapino, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+load+on+active+friction+control+using+ultrasonic+vibrations.">Effect of load on active friction control using ultrasonic vibrations.</a> Proc. SPIE. 7290, 7290G (2010).</li><li>Kumar, V., Hutchings, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduction+of+the+sliding+friction+of+metals+by+the+application+of+longitudinal+or+transverse+ultrasonic+vibration.">Reduction of the sliding friction of metals by the application of longitudinal or transverse ultrasonic vibration.</a> Tribol. Int. 37 (10), 833-840 (2004).</li><li>Pohlman, R., Lehfeldt, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+ultrasonic+vibration+on+metallic+friction.">Influence of ultrasonic vibration on metallic friction.</a> Ultrasonics. 4 (4), 178-185 (1966).</li><li>Popov, V., Starcevic, J., Filippov, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+Ultrasonic+In-Plane+Oscillations+on+Static+and+Sliding+Friction+and+Intrinsic+Length+Scale+of+Dry+Friction+Processes.">Influence of Ultrasonic In-Plane Oscillations on Static and Sliding Friction and Intrinsic Length Scale of Dry Friction Processes.</a> Tribol. Lett. 39 (1), 25-30 (2010).</li><li>Dong, S., Dapino, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Piezoelectrically-induced+ultrasonic+lubrication+by+way+of+Poisson+effect.">Piezoelectrically-induced ultrasonic lubrication by way of Poisson effect.</a> Proc. SPIE. 8343, 83430L (2012).</li><li>Dong, S., Dapino, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elastic-plastic+cube+model+for+ultrasonic+friction+reduction+via+Poisson+effect.">Elastic-plastic cube model for ultrasonic friction reduction via Poisson effect.</a> Ultrasonics. 54 (1), 343-350 (2014).</li><li>Dong, S., Dapino, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wear+Reduction+Through+Piezoelectrically-Assisted+Ultrasonic+Lubrication.">Wear Reduction Through Piezoelectrically-Assisted Ultrasonic Lubrication.</a> Smart. Mater. Struct. 23 (10), 104005 (2014).</li><li>Chowdhury, M., Helali, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+frequency+of+vibration+and+humidity+on+the+wear+rate.">The effect of frequency of vibration and humidity on the wear rate.</a> Wear. 262 (1-2), 198-203 (2014).</li><li>Bryant, M., Tewari, A., York, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Micro+(rocking)+vibrations+and+surface+waviness+on+wear+and+wear+debris.">Effect of Micro (rocking) vibrations and surface waviness on wear and wear debris.</a> Wear. 216 (1), 60-69 (1998).</li><li>Bryant, M., York, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurements+and+correlations+of+slider+vibrations+and+wear.">Measurements and correlations of slider vibrations and wear.</a> J. Tribol. 122 (1), 374-380 (2000).</li><li>Goto, H., Ashida, M., Terauchi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+ultrasonic+vibration+on+the+wear+characteristics+of+a+carbon+steel:+analysis+of+the+wear+mechanism.">Effect of ultrasonic vibration on the wear characteristics of a carbon steel: analysis of the wear mechanism.</a> Wear. 94, 13-27 (1984).</li><li>Goto, H., Ashida, M., Terauchi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wear+behaviour+of+a+carbon+steel+subjected+to+an+ultrasonic+vibration+effect+superimposed+on+a+static+contact+load.">Wear behaviour of a carbon steel subjected to an ultrasonic vibration effect superimposed on a static contact load.</a> Wear. 110 (2), 169-181 (1986).</li><li>Robinowicz, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The friction and wear of materials. , (1965).</li><li>Bowden, F., Freitag, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+friction+of+solids+at+very+high+speeds.">The friction of solids at very high speeds.</a> Proc. R. Soc. A. 248 (1254), 350-367 (1985).</li><li>Burwell, J., Rabinowicz, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+nature+of+the+coefficient+of+friction.">The nature of the coefficient of friction.</a> J. Appl. Phys. 24 (2), 136-139 (1953).</li><li>Cocks, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interaction+of+sliding+metal+surfaces.">Interaction of sliding metal surfaces.</a> J. Appl. Phys. 33 (7), 2152-2161 (1962).</li><li>Rusinko, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Ultrasound and Irrecoverable Deformation in Metals. , (2012).</li></ol>

The authors have nothing to disclose.

Experiments were conducted using this protocol to study the effect of linear speed on ultrasonic friction and wear reduction. The measurements show that ultrasonic vibrations effectively reduce friction and wear at three linear speeds.&#160;Consistent with prior observations, the amount of friction reduction decreases from 62.2% at 20.3 mm/sec to 29.3% at 87 mm/sec. Wear reduction is negligible with changing linear speed (45.8% to 48.6%).
Material properties such as Young&#8217;s modulus and y...

Friction exists at the interface of two contacting surfaces when they slide or roll relative to each other. Friction usually occurs along with abrasive or adhesive wear.1 Ultrasonics is the science behind high frequency phenomena, that is, waves traveling at frequencies above the acoustic range (20 kHz). The field of ultrasonics encompasses two fundamentally different regimes. One regime involves low intensity waves like those utilized in imaging processes such as medical ultrasound or non-destructive inspection of structures. The other is a high power regime in which high-energy waves are utilized to execute or assist engineering processes such as welding of plastics and metals. It has been shown that application of the latter kind of ultrasonic vibrations at the interface of two surfaces in sliding contact reduces the effective friction force at the interface. This phenomenon is known as ultrasonic lubrication.
To achieve ultrasonic lubrication between two sliding objects, relative vibration at ultrasonic frequencies must be established between them. Vibrations are typically applied to one of the two objects, either in the longitudinal, transverse, or perpendicular direction relative to the sliding velocity. In this study, a tribometer&#8217;s pin is fitted with a piezoelectric actuator so that its tip vibrates in the direction perpendicular to the tribometer&#8217;s rotating disc. Piezoelectric materials are a class of &#8220;smart&#8221; materials that deform when exposed to electric fields, vibrating at the same frequency as the excitation field. Piezoelectric materials can vibrate at frequencies well into the MHz range. Being superimposed to the macroscopic velocity, ultrasonic vibrations have the effect of alternating the direction of the instantaneous friction force and the contact between the surfaces, which in combination leads to a reduction of the effective friction force and surface wear.
Ultrasonic friction reduction has been demonstrated in practical manufacturing systems. For example, this technology has been utilized to reduce the force between tool and work piece in metal machining and forming processes such as drilling, pressing, sheet rolling, and wire drawing. Benefits include improved surface finish2 and a reduced need for expensive and environmentally harmful detergents to remove lubricants from the final product. There are potential applications of ultrasonic lubrication in other areas as well. For example, ultrasonic lubrication can substantially enhance the user experience in personal health care products by eliminating the need for lubricants or coatings. In automobile applications, friction modulation can improve the performance of ball joints whereas friction reduction between vehicle seats and rails facilitates seat movement, saving space and mass that would otherwise be occupied by traditional components and mechanisms. Ultrasonic lubrication can also help to improve fuel efficiency by reducing friction in powertrain and suspension systems.3 In space applications, where traditional lubricants cannot be used, ultrasonic lubrication can be employed to reduce wear and dramatically extend the life of critical components.
Laboratory demonstrations of friction reduction through ultrasonic lubrication are numerous. Friction reduction is quantified as the difference between the friction force measured without ultrasonic lubrication and the friction force with ultrasonic vibrations applied. In either case, the friction force is directly measured with force sensors. Littmann et al. 4-5 connected a piezoelectrically-driven actuator to a slider, on which a force sensor and a frame were installed for measuring friction forces and applying normal loads. A pneumatic actuator was employed to push the slider together with the actuator along a guide rail. Ultrasonic vibrations were applied in the direction longitudinal to the sliding velocity. Bharadwaj and Dapino6-7 conducted similar experiments using a piezoelectric stack actuator connected to a conical waveguide at either end of the stack. Contacts took place between the spherical edges of the cones and the surface of the guide rail. The effects of system parameters such as contact stiffness, normal load, and global stiffness were studied. Kumar and Hutchings8 installed a pin on a sonotrode which was energized by an ultrasonic transducer. Ultrasonic vibrations were generated and transmitted to the pin, which was placed in contact with a tool steel surface. Normal force was applied by a pneumatic cylinder and measured by a load cell. The relative motion between the pin and the disc was created by a reciprocating table.
Pohlman and Lehfeldt9 also implemented a pin-on-disc experiment. Unlike other studies, they employed a magnetostrictive transducer to generate ultrasonic vibrations. To study the optimum direction for ultrasonic friction reduction, the transducer was carefully aligned so that the vibrational direction was longitudinal, transverse, and vertical to the macroscopic velocity. They studied ultrasonic friction reduction on both dry and lubricated surfaces. Popov et al.10 utilized an actuator with conical waveguides. The actuator was placed in contact with a rotating base plate. Cones made of nine materials with various hardnesses were adopted to study the influence of material hardness on ultrasonic friction reduction. Dong and Dapino11-13 used a piezoelectric transducer to generate and transmit ultrasonic vibrations to a prismatic waveguide with rounded edges. The longitudinal vibration causes vertical vibration due to Poisson&#8217;s effect. A slider with a curved top was placed under and in contact the waveguide. A frame was built to apply normal forces at the contact interface. The slider was pulled manually around the center area of the waveguide; the friction force was measured by a load cell that was connected to the slider.
Ultrasonically-induced wear reduction was also investigated and demonstrated. Volume loss, weight loss, and surface roughness changes are employed to quantify the severity of wear.Chowdhury and Helali14 vibrated a rotating disc in a pin-on-disc setup. The vibrations were generated by a support structure of two parallel plates located under the rotating disc. The top plate has a spherical ball installed off-center on the bottom surface, which slides in a slot that was engraved at the top surface of the bottom plate. The slot was machined with a periodically variable depth so that the top plate moves vertically during rotation. The frequencies ranged around 100 Hz according to the rotational speed.
Bryant and York15-16 studied the effect of micro-vibrations on wear reduction. They inserted a carbon cylinder through a holder with one end rested on a spinning steel disc and the other end connected to a coil spring. In one case, the cylinder was snug fitted in the holder so that there was no space for vibration. In other cases, clearances were left to allow micro-vibrations of the cylinder while the cylinder was in contact with the spinning disc. The weight loss of the cylinder was measured to calculate the wear rate. It was shown that the self-generated micro-vibrations helped reduce wear by up to 50%.
Goto and Ashida17-18 also adopted a pin-on-disc experiment. They connected pin samples with a transducer via a tapered cone and a horn. The pin vibrated in the direction perpendicular to the disc surface. A mass was connected to the transducer on its top for applying normal loads. Friction forces were translated from the torque that was applied to rotate the disc. Wear was identified as adhesive because both pin and disc were made of carbon steel. Wear rates were calculated from volume loss measurements.
It has been shown that linear speed plays an important role in ultrasonic lubrication. The experimental component of this research focuses on the dependence of friction and wear reduction on linear speed.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>DC Motor&#160;</td>
			<td>Minarik&#160;</td>
			<td>SL14</td>
		</tr>
		<tr>
			<td>Electrical amplifier</td>
			<td>AE Techron</td>
			<td>LVC5050</td>
		</tr>
		<tr>
			<td>Signal conditioner&#160;</td>
			<td>Vishay Measurements Group</td>
			<td>2310</td>
		</tr>
		<tr>
			<td>Signal generator</td>
			<td>Agilent&#160;</td>
			<td>33120A</td>
		</tr>
		<tr>
			<td>Piezoelectric stack</td>
			<td>EDO corporation</td>
			<td>EP200-62</td>
		</tr>
		<tr>
			<td>Load cell</td>
			<td>Transducer Techniques</td>
			<td>MLP-50</td>
		</tr>
		<tr>
			<td>Load sensor pad</td>
			<td>FlexiForce</td>
			<td>A201</td>
		</tr>
		<tr>
			<td>Laser meter</td>
			<td>Keyence corporation&#160;</td>
			<td>LK-G32</td>
		</tr>
		<tr>
			<td>Hall-effect probe and gaussmeter</td>
			<td>Walker Scientific, Inc.</td>
			<td>MG-4D</td>
		</tr>
		<tr>
			<td>Data acquisition module</td>
			<td>Data Physics</td>
			<td>Quattro</td>
		</tr>
		<tr>
			<td>Data acquisition software</td>
			<td>Data Physics</td>
			<td>SignalCalc Ace</td>
		</tr>
		<tr>
			<td>Thermocouple reader</td>
			<td>Omega</td>
			<td>HH22</td>
		</tr>
		<tr>
			<td>Optical profilometer</td>
			<td>Bruker</td>
			<td>Contour GT</td>
		</tr>
		<tr>
			<td>Profilometer operation software</td>
			<td>Bruker&#160;</td>
			<td>Vision 64</td>
		</tr>
	</tbody>
</table>

experiments on ultrasonic lubrication using a piezoelectrically-assisted tribometer and optical profilometer

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at a frequency above the acoustic range (20 kHz). As a solid-state technology, ultrasonic lubrication can be used where conventional lubricants are unfeasible or undesirable. Further, ultrasonic lubrication allows for electrical modulation of the effective friction coefficient between two sliding surfaces. This property enables adaptive systems that modify their frictional state and associated dynamic response as the operating conditions change. Surface wear can also be reduced through ultrasonic lubrication. We developed a protocol to investigate the dependence of friction force reduction and wear reduction on the linear sliding velocity between ultrasonically lubricated surfaces. A pin-on-disc tribometer was built which differs from commercial units in that a piezoelectric stack is used to vibrate the pin at 22 kHz normal to the rotating disc surface. Friction and wear metrics including effective friction force, volume loss, and surface roughness are measured without and with ultrasonic vibrations at a constant pressure of 1 to 4 MPa and three different sliding velocities: 20.3, 40.6, and 87 mm/sec. An optical profilometer is utilized to characterize the wear surfaces. The effective friction force is reduced by 62% at 20.3 mm/sec. Consistently with existing theories for ultrasonic lubrication, the percent reduction in friction force diminishes with increasing speed, down to 29% friction force reduction at 87 mm/sec. Wear reduction remains essentially constant (49%) at the three speeds considered.

The representative measurements presented here were obtained from the modified tribometer shown in Figure 1. The piezoelectric actuator generates vibrations with amplitude of 2.5 &#956;m at a frequency of 22 kHz. To study the dependence of friction and wear reduction on linear velocity, three different speeds (20.3, 40.6, and 87 mm/sec) were applied to the disc by changing the rotational speed of the motor. For all three groups, the number of disc revolutions and the travel distance of the pin were chose...

Watch this Scientific Journal Video about Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer at JoVE.com

Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer

We present a protocol for using a piezoelectrically-assisted tribometer and optical profilometer to investigate the dependence of ultrasonic wear and friction reduction on linear velocity, contact pressure, and surface properties.

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at ...

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12.5K Views.  The Ohio State University. We present a protocol for using a piezoelectrically-assisted tribometer and optical profilometer to investigate the dependence of ultrasonic wear and friction reduction on linear velocity, contact pressure, and surface properties. 