【正文】 r friction estimation in reciprocating wear testsH. Fama,b, M. Kontopouloua,b, . Bryanta,c,?a Human Mobility Research Centre, Queen’s University, Kingston General Hospital, Kingston, ON, , Canadab Department of Chemical Engineering, Queen’s University, Kingston, ON, , Canadac Department of Mechanical and Materials Engineering, Queen’s University, Kingston, ON, , Canadaa b s t r a c tA method is described by which the coefficient of friction was determined using a linear reciprocating wear testing machine with spherical metal indenters articulating on flat UHMWPE samples and deionized and distilled water lubrication. A characteristic periodic pattern in the friction behaviour was observed. The coefficient of friction was puted by calculating the average of 30 points about the midpoint between reversals and using the average of three cycles. Variability between tests was equivalent to that obtained between stations but was considerably higher than that obtained between cycles. The coefficient of friction could reliably be estimated using this method with a standard deviation of .. 2022 Elsevier . All rights reserved241. IntroductionTotal knee replacement is an orthopaedic surgical procedure used to replace knee joints with osteoarthritis, rheumatoid arthritis and severe trauma [1]. The femoral ponent is typically made of a metal alloy such as cobalt chrome (CoCr) and the tibial ponent includes an insert typically made of UHMWPE on a metal backing made of an alloy such as CoCr or titanium. Wear of the polymeric ponent has been a focus of studies directed toward optimizing the performance of these bearings [2–18]. Recently, studies have been undertaken to evaluate friction in these systems in an attempt to understand the mechanisms of wear [19–22]. It is recognized that friction measurements may reveal the mode of lubrication occurring within joint prostheses. Boundary and hydrodynamic fluid film lubrication are the mechanisms known to take place in joint replacements [23]. Hydrodynamic fluid film lubrication of bearing surfaces occurs when a viscous film is generated separating the two surfaces [24]. The two surfaces must move relative to each other with sufficient velocity for the hydrodynamic film to be generated [24]. If the hydrodynamic pressure is insufficient to separate the surfaces, then lubrication would primarily depend on the ponents of the fluid that could form boundary films [25]. In boundary lubrication, these ponents adsorb on the bearing surfaces and aid in minimizing friction upon contact. In mixed lubrication, the surfaces are partially separated by a fluid film, and partially in contact at the asperities [24]. Lubricant viscosity is a critical determinant in hydrodynamic fluid film lubrication, and hence it is important to consider its effect on the friction behaviour of joint prosthesis bearing surfaces [26]. This is particularly important since periprosthetic fluid, the fluid that bathes joint replacements in vivo, contains HA (hyaluronic acid) a high molecular weight ponent that imparts it with viscous characteristics. Friction studies have been conducted to determine the lubrication mechanism in which different bearing materials of joint replacements operate [27–29]. This is typically performed 25by using the Stribeck analysis where the friction factor is plotted against the Sommerfeld number [27,28]. A decrease in the friction factor with increase in Sommerfeld number is indicative of mixed lubrication while an increase in the friction factor with Sommerfeld number is indicative of fluid film lubrication [19,28,29]. Based on this analysis Flannery et al. [19] suggested that in total knee replacement a mixed lubrication regime dominates. While simulator testing has focused on recreating the conditions of loading and motion of joints in service [7,9], friction measurements tend to use simpler test conditions at constant speeds [21]. This strategy makes it possible to delineate the factors influencing the lubrication mechanisms associated with theStribeck curve. However, wear studies have shown a relationship between the nature of surface motion (rolling, sliding, crossshear, etc.) and wear patterns [30]. Therefore, in order to study therole of lubrication in this phenomenon, it is necessary to measure friction under the dynamic conditions associated with joint replacements. The purpose of this study was to determine a method for estimating the friction coefficient in a linear reciprocating machineunder kinematic and loading conditions representative of those encountered in total knee replacement. A reciprocating pin on disc friction and wear testing machine (AMTI OrthoPodTM, AMTITM, Watertown, MA) was used with deionized and distilled water lubrication. A protocol for data acquisition and analysis was designed, followed by statistical analysis that quantified the variability of the friction coefficient among different stations and tests. This study was designed to be used as basis for future work involving different lubricants, test geometries, and surface kinematics.2. Materials and methods. InstrumentationAn AMTI OrthoPodTM six station pin on di。 [8]桂長林，沈健 .摩擦磨損試驗機設(shè)計的基礎(chǔ)Ⅲ.固體潤滑，2022,1。每次遇到難題，我最先做的就是向老師尋求幫助，而老師每次不管忙或閑，總會抽空來找我面談，然后一起商量解決的辦法。該設(shè)計在滿足設(shè)計要求的前提下，力求結(jié)構(gòu)簡單，制造成本低廉，沒有一味的追求高精度，適合進行實際的生產(chǎn)。對所用天平的精密度要求取決于磨損量的數(shù)量級。 傳動功率為 p=24kw 查《機械設(shè)計》圖 得接觸疲勞極限 =710MPa， =580MPa1limH?2limH?10初步計算的許用接觸應(yīng)力 ????= 710=639MPa，? = 580=522MPa2li2 齒輪 1 轉(zhuǎn)速為 =13（r/min)1n 齒輪 2 轉(zhuǎn)速為 =4(r/min)2 齒輪 1 齒數(shù) =19，齒寬 =145z1B 齒輪 2 齒數(shù) =62，齒輪 =130mm2 使用系數(shù) 查《機械設(shè)計 》表 得 = 動載系數(shù) 查,《機械設(shè)計》圖 得 = V a?= =?????????????? = =? 齒向載荷分布系數(shù)由《機械設(shè)計》表 得 =A+B 2+c =?HK??????1db14503???C 載荷系數(shù) K= = =??接觸壽命系數(shù) 由《機械設(shè)計》圖 得NZ 1=， = 許用接觸應(yīng)力 = = =7