INDUSTRY NEWS
Simulating the Friction of Lubricants and Materials with a High-Frequency Reciprocating Rig Source: Coherent Scientific
Performing Reciprocating Tribotests Scanning Testing of surfaces and lubricants on reciprocating systems, such as engines and linear To simulate the behaviour of a reciprocating system, one must compressors, requires the use of laboratory-scale select the elements that play important roles on the tribological tribometers prior to final component testing. This system. Such elements include: application note discusses a tribometry setup that • Material and geometry of the tested samples enables time-effective screening of lubricants and • Contact pressure between surfaces that is controlled by the materials at the benchtop scale using a UMT TriboLab™ load, geometry, and material of the contact surfaces Reciprocating Tests (Bruker, San Jose, CA). With this setup, the samples • Reciprocating frequency and stroke length that will direct the can be tested under simulated conditions to rank the motion and velocity profiles, and performance of lubricants and surfaces, while monitoring UMT TriboLab HFRR • Controlled temperature that will activate tribo-chemical events small changes in friction with a piezoelectric-based force on the tested surfaces sensor. The article covers the technique and analyses its effectiveness in simulating standard protocols, such Key resulting parameters that could be measured during the tests as the ASTM D6245-17, and shows how. Also, of great Engine include: Tribosystem importance, the system offers unprecedented flexibility • Friction changes along the stroke, since the friction is not for a wide range of conditions and parameters, such steady in reciprocating systems as speed, stroke length, and temperature variation. • Temperature changes, and Finally, also presented, is the critical importance of • Wear measured after the test the calculation method employed to analyse the data obtained by high-frequency reciprocating tests.
Application Note #1016 Simulating the Friction of Lubricants and Materials with a For the purposes of this study, a TriboLab system, equipped with High-Frequency Reciprocating Rig the new High Frequency Reciprocating Rig (HFRR). One main
Evaluating the Behaviour of Lubricants and Materials on Reciprocating Systems
advantage of the use of a small-scale tribometer is that the lubricant and surfaces can be easily characterized after the test with other metrology tools, such as profilometers and chemical Continuous development of lubricants and surfaces for analysers/spectrometers. Figure 1 shows the TriboLab setup reciprocating engines and compressors is needed to meet The precise understanding of component wear and friction Testing of surfaces and lubricants on reciprocating systems, for high-frequency reciprocating tests. The setup is equipped changing environmental regulations, improve automobile fuel in mechanical systems is vital to quantify energy losses such as engines and linear compressors, requires the use with a fast reciprocating stage, a piezo-based sensor, a normaleconomy, and extend component durability. and to predict the durability of such surfaces. Thus, the of laboratory-scale tribometers prior to final component force sensor, and a 400°C heater. The sensor assembly has been measurement of lubricant performance continues to be a testing. This application discusses setup The precise understanding of component wear note and friction in a tribometry designed with the capability of pivoting to allow the user to factor in accurate fuel economy estimation. To do mechanical systems is vital to quantify energy losses and to that enables time-effective screening of lubricants and replacecritical quickly lower samples and apply lubricant. this successfully, one must account for various challenges predict the durability ofmaterials such surfaces. the measurement at the Thus, benchtop scale using a UMT TriboLab™ in Figure precisely mimicking the specific and factors As an example, 2 shows a typical result ofconditions 5W-30 engine of lubricant performance continues be aCA). critical in (Bruker, San to Jose, Withfactor this setup, the samples that might play a major role on the tribological performance oil tested using a reciprocating ball-on-flat (steel-on-steel) accurate fuel economy estimation. Tounder do this successfully, one to rank the can be tested simulated conditions of those systems. Fortunately, these measurements are configuration and the ASTM D6425-17 conditions with the HFRR must account for various challenges in precisely mimicking the performance of lubricants and surfaces, while monitoring possible with laboratory-scale tribometers. specific conditions and factors that might play a major role on small changes in friction with a piezoelectric-based force the tribological performance ofThe those systems. Fortunately, theseand analyzes sensor. material covers the technique Tribological evaluation of reciprocating systems can be measurements are possible with laboratory-scale tribometers. its effectiveness in simulating standard protocols, such as reciprocating the ASTM D6245-17, how. Also, of great Tribological evaluation of systemsand canshows be effectively importance the system offersimplementing unprecedented flexibility for performed at the laboratory scale only by correctly a widethat range of conditions and parameters, such as speed, a motion and velocity profile exactly simulates the actual stroke length, and variation. Finally, we also motion of the real-world tribosystems. Totemperature properly simulate present thethat critical importance the calculation method materials or lubricants in systems reciprocate, it isofcritical to to analyze the databy obtained replicate the sinusoidal employed motion, typically produced a slider-by high-frequency reciprocating tests. crank mechanism in which the lubrication regime could be varying along the stroke, and to monitor the small changes in Evaluatingprecise the Behavior of Lubricants friction. This requires high-speed, force transducers and and Materials displacement sensors. on Reciprocating Systems
effectively performed at the laboratory scale only by correctly implementing a motion and velocity profile that exactly simulates the actual motion of the real-world tribosystems. To properly simulate materials or lubricants in systems that reciprocate, it is critical to replicate the sinusoidal motion, typically produced by a slider-crank mechanism in which the lubrication regime could be varying along the stroke, and to monitor the small changes in friction. This requires high-speed, precise force transducers and displacement sensors. A variety of standards are in use by the automotive and
Continuous of lubricants and surfaces A variety of standards are in use bydevelopment the automotive and lubricants industry. Of particular interest here is the for reciprocating is needed lubricants industry. Of particular interestengine here isand thecompressors ASTM ASTM D6425-17 (Standard Test Method for Measuring meet changing environmental D6425-17 (Standard TesttoMethod for Measuring Friction regulations, and Wear improve Friction and Wear Properties of Extreme Pressure (EP) automobile economy,Oils andUsing extend durability. Lubricating Oils Using SRV Test Machine)1. This specific Properties of Extreme Pressure (EP)fuel Lubricating SRVcomponent Test Figure 1. UMT TriboLab with HFRR setup. Left: Setup includes the reciprocating Machine)1. This specific protocol ranks lubricants using severe drive, HFRR sensor, 400°C heater, and load sensor. Right: Pivoting allows easy setup of the samples. conditions of temperature, speed, and contact pressure.
36 | JUNE 2021
BACK TO CONTENTS
WWW.MATERIALSAUSTRALIA.COM.AU
