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In this study, journal bearings were manufactured from composite structures by casting method reinforcing 3% (Al2O3 and SiC) and (3% Al2O3 + 3% SiC) into pure Al. Tribological properties of these bearings were investigated by wear experiments at lubricated conditions under 20 N load and 1500 rpm on the radial journal bearing wear test rig. Effects of these composites on wear properties were investigated. Consequently, tribological properties of these particle reinforced composite bearings have significantly improved. In addition, particle reinforced Al composites were used to produce journal bearing.

Wear condition of journal bearing was experimentally monitored with an On-Line Visual Ferrograph (OLVF) system. The round bearing was made of 45# steel with babbitt alloy bushing and the bearing journal was made of 45# steel. High stress of the water content of 0%,1%,3% in lubricant, 10 times of a normal load of 2200 N, and the rotating speeds at 500, 1000, 2000 rpm were adopted in accelerated experiment. A quantitative index of particle coverage area (IPCA) together with wear debris ferro-image was used to characterize wear degree and wear mechanisms. Three wear stages with corresponding wear debris ferro-images were identified from IPCA variations characterized by bathtub curve trend. The first one was running-in stage characterized by the highest wear debris producing rate and higher large debris content. The second one was normal wear stage characterized by the lowest wear debris producing rate and small normal debris. The final one was failure initiation stage characterized by higher wear debris producing rate and higher large debris content. The corresponding dominant wear mechanisms were micro-ploughing and micro–cutting induced by rough initial surfaces in the running-in stage, local rub due to vibration in the normal stage, and fatigue and abrasive wear in the failure initiation stage.

This article presents an approach based on wavelet correlation modelling for health state monitoring of fluid dynamic bearings in brushless DC motors. This approach involves two stages: (1) extracting of features from the motor-stator current signatures by analysing discrete wavelet transform coefficients; and (2) building of the simplest correlation model between the extracted features and the bearing wear using a multivariable regression technique. The correlation model can be used to detect and predict the bearing wear of brushless DC motors. Experiments were carried out using brushless DC motors with fluid dynamic bearings to verify the proficiency of this approach. Good agreement between the prediction result and the real motor health condition demonstrated the viability of the approach for bearing prognostic applications. The correlation equations obtained have acceptable detectability and accuracy based on a desired 95% level of confidence.

Production process of the rotor causes a primary unbalance where the mass center of the rotor does not locate in its rotation axis. Excessively large unbalance force and moment induce large amplitudes of the rotor response that leads to the bearing wear, bearing failure, and rub contact between the rotor and stator of electric machines. Additionally, the rotor unbalance generates unbalance whistle that is synchronous with the rotor frequency (frequency order 1×). The unbalance whistle is one of the undesirable airborne noises in electric vehicles.

The main bearing and sub bearing which support the crankshaft rotation often have wear in the rotary compressor, and the exceptional wear will cause a series of problems which contain the vibration, noises, frictional power rising and reliability reduced. The process of improving the actual exceptional wear problems of bearings is analyzed. And based on the finite element method (FEM), the results of the original and improved bearings are compared with each other; contact stress is chosen to be used to evaluate the wear condition of bearings. Then the influence of height, diameter and clearance of main bearing on the wear of the bearing is analyzed by the accelerated life test and the FEM simulation, and the feasibility of the bearing contact stress to evaluate the wear condition of bearings is further verified, at the same time it provides a theoretical basis for the design of compressor bearing.

It has been recognized for about 50 years that the addition of polymer to motor oil will result in shear-dependent viscosity at relatively low shear stress. This shear-thinning can be shown to reduce the elastohydrodynamic film thickness and there has been an expectation of a reduced film in hydrodynamic lubrication as well. The expected associated increase in the journal bearing wear, however, has not been observed. The load-supporting benefit of the elastic properties contributed by the polymer has been used as an explanation for the success of the polymer blended oils in this application. The available measurements of elasticity in the form of normal stress differences have been inconclusive regarding their contribution to load support. These measurements have all been at atmospheric pressure, however, and at a very high shear rate. The oil in the load-carrying region of a bearing is at elevated pressure and the elevated pressure may enhance the elasticity. A new experimental technique for the measurem...

Background As outcomes for destination therapy continue to improve, many patients are requiring left ventricular assist device (LVAD) exchange due to end-of-life of their LVAD. Current techniques to identify and diagnose device end-of-life issues usually require invasive testing or off-site filter dust analysis. In this study we assess a non-invasive technique using acoustic signals generated from the HeartMate XVE LVAD to potentially identify impending device end-of-life issues. Methods Nine patients were prospectively followed after implantation of the HeartMate XVE LVAD as destination therapy between May 2004 and July 2006. Acoustic signals were collected using an aquatic hydrophone system interfaced with a data acquisition system and a standard laptop computer. Data were collected at pre-set intervals. All data/acoustic signals were prospectively interpreted by a blinded independent reviewer skilled at interpreting acoustic signals. Acoustic data suggesting possible device failure were then correlated with clinical findings and LVAD examination at the time of device removal. Results All patients survived long enough to develop signs of impending device end-of-life. Four of 9 (44%) patients developed inflow valve incompetence, 4 (44%) were identified as having significant bearing wear, and 1 (12%) had both. All acoustically identified device issues were confirmed by standard clinical examinations and testing (echocardiography, angiography, laboratory tests and filter dust analysis). The acoustic findings were subsequently confirmed at time of device exchange. All patients ultimately had their device successfully exchanged and have continued to live with their new apparatus. Conclusions Acoustic signal monitoring can successfully identify HeartMate XVE device end-of-life. This new method provides a low-cost, reproducible, non-invasive technique that may be used to identify possible impending device failure.

This paper presents the method of assessing rope wheel bearing wear, developed for the special case of a shaft hoist in the Bogdanka coal mine. The diagnosis method presented here may also be used for inspecting the bearings of direction rope wheels with movable axles and bearings placed outside the axle in bodies, of the type that prevail in Polish coal mining. The superiority of this method in comparison to those used so far consists in limiting the testing time, as well as in the fact that no extra workers are needed. Nor does it require special availability of the shaft equipment for performing the test.

Bronze is widely used as a journal bearing material for copper-based alloys. These alloys ensure that journal bearings possess the expected properties. These materials that possess tribological properties give good results at journal bearings. In this study, friction and wear properties of journal bearings manufactured by CuSn10 bronze and the effect of p.v. (pressure–velocity) parameter have been examined and compared. SAE 1050 steel shaft has been used as counter abrader. Experiments have been carried out for p.v. values of 0.0125, 0.025 and 0.05 (N/mm s) and for every half an hour totalling to 2.5 h by using radial journal bearing wear test rig. As a result, depending on p.v. values, high friction coefficient and weight loss have been obtained under dry condition more than those obtained under lubricated condition.

Firstly, the concepts and classification about visualized data mining technology have been elaborated in this paper, then the technology of data mining, data visualization and regression analysis are discussed, Finally, combined with the example of sliding bearing wear coefficient test, using data mining, data visualization and regression analysis technology, this paper design a system to implement visualized data mining technology under the web environment.

The HeartMate XVE left ventricular assist device is a valuable treatment option for patients with end-stage heart failure. During the past several years, the XVE has undergone a series of design enhancements to improve reliability. We compared the reliability of the two most recent design iterations of the XVE pump (stitch modification to the inflow valve assembly and new inflow valve housing redesign) to the earlier VE version.A retrospective evaluation of device reliability was performed for 268 devices implanted in 245 patients (VE: n = 167 devices, 147 patients, implant dates October 16, 1998, to December 19, 2003; XVE: n = 101 devices, 98 patients, implant dates August 1, 2002, to April 14, 2004).Median duration of device support for the VE and XVE was 159 days (range, 0 to 1,206 days) and 229 days (range, 0 to 693 days), respectively (p = 0.495). Significantly fewer major device malfunctions occurred within the XVE group as compared with the VE group (6 versus 36, respectively; p = 0.0003). The number of major device malfunctions per patient-year of support for inflow valve dysfunction, bearing wear, and other failures for the VE and XVE were 0.2 versus 0.04 (p = 0.006), 0.16 versus 0.01 (p = 0.005), and 0.06 versus 0.04 (p = 1.000), respectively. The freedom from major device malfunction at 1 year was 76% +/- 6% for the VE and 97% +/- 2% for the XVE device (p0.001). The freedom from death as a result of major device malfunction at 1 year was 97% +/- 2% for the VE and 98% +/- 2% for the XVE (p = 0.698).Design enhancements to the HeartMate XVE have significantly reduced the incidence of major device malfunctions compared with the earlier VE model because of a reduction in failure modes from bearing wear and inlet valve dysfunction. Further follow-up is necessary to establish the long-term durability of the most recent XVE pump version.

Bearing wear and associated osteolysis are the most common problems affecting the long-term results of total hip arthroplasty. Alumina ceramic–ceramic bearings have been introduced as one method of addressing these problems. The current study reviews the clinical outcome of the use of alumina ceramic–ceramic bearings in the United States and specifically reports on the 2- to 8-year results of a prospective FDA–ID. Results demonstrate that the alumina ceramic–ceramic bearings are reliable and show very few early problems. Ceramic fractures do occur rarely and may be similar in incidence to reports of fractures or disassociations of polyethylene components. The incidence of instability is extremely low despite the absence of lipped liners and fewer head-length options.

In this article, fuzzy logic method is used to detect two types of incipient faults viz., interturn insulation failure and bearing wear in single-phase induction motor. The fuzzy rules are framed depending upon the experimental data for five input parameters viz., motor intake current, rotor speed, winding temperature, bearing temperature, and noise. The simulation and experimental results are given to verify the proposed method. Initially the performance is tested with two inputs, motor intake current and rotor speed; later the remaining three input parameters were added and the performance is tested with five inputs. It is found that the performance with five inputs gives better results.

The original Oxford and Low Contact Stress mobile-bearing unicompartmental knee designs have been used successfully since the mid-1970s, but have had limited exposure. Our study reviews 177 LCS unicompartment replacements (156 medial) with 5–19 years follow-up. Mean age was 68 years, 70% were female, with osteoarthritis (OA) diagnosis in 96%. Fixation was cementless in 72% and cemented in 28%. Results were good/excellent [modified Hospital for Special Surgery (HSS)] in 82%. Scores improved from 60 to 86, mean range of motion 123°. Complications requiring reoperation were 32 of 177 knees (18%). Early failures were technique-related and late failures (3+ years) related to bearing wear/fracture; 15 cases required bearing exchange alone. Low contact stress mobile-bearing unicompartmental knee arthroplasties with 82% prosthetic survivorship at 11 years is encouraging, especially in a more active population and with the success of bearing exchange.

The combined wear of water-lubricated bearings supporting a flexible shaft has a modal characteristic, that is, the cumulative wear can be represented by distinct patterns (modes) that increase geometrically at unique rates. The instantaneous wear rates decrease exponentially with time and approach zero asymptotically. The total load on the outboard bearings decreases and the total load on the inboard bearings increases: the redistribution of outboard and inboard loads is controlled by the shaft stiffness matrix (the reaction influence numbers). The characteristics of modal wear are examined and the changes in alignment loads are calculated, particular attention being paid to reduction-gear loads. Numerical results are displayed.

Rotating-platform knee arthroplasties have enjoyed an outstanding clinical history since their introduction in 1978. Mechanical complications requiring further surgery have been identified and include loosening, bearing dislocation, bearing wear, and osteolysis. No structural, metallic failures were reported, although extreme bearing wear was noted to cause metal surface damage sufficient to require revision in isolated cases. Survivorship of primary LCS cemented rotating-platform knee arthroplasties using an endpoint of revision of any component for any reason was 97.7% at the 20-year interval. Survivorship of primary LCS cementless rotating-platform knee arthroplasties using the same endpoint was 98.3% at the 18-year interval.

There is currently much discussion about the most clinically relevant testing methods for evaluating total hip replacements. This study examined the effect of different swing phase loads, including microseparation, on the wear, friction, and wear particles of metal-on-metal (MOM) hip replacements. MOM hip replacements were tested for 5 million cycles with the use of a hip simulator; prostheses were tested with a low (100-N) and ISO (280-N) swing phase load, and under microseparation conditions. Increasing the swing phase load from 100 to 280 N in the same hip simulator increased the wear of the MOM hip replacements by over tenfold. Introducing microseparation into the gait cycle increased wear further, and stripe wear was observed on the femoral heads, accompanied by corresponding rim damage on the acetabular cups. No significant difference in wear particle size was observed between wear particles produced by low load and microseparation hip simulator conditions. Introducing microseparation into the hip simulator gait cycle increased the wear of MOM prostheses. Joint laxity and separation may lead to increased wear rates of MOM prostheses in vivo. Additionally elevated positive swing phase loads may also increase wear. Variable swing phase load conditions in vivo may contribute to variations in clinical wear rates. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 70B: 233–239, 2004

Theoretical analysis of the geometry of flowmeters with a mechanical oscillator in the form of a prism, which appeared on the market in the 1970s, has shown that its properties can be significantly improved. A simplified theory of the flowmeter has been presented. Based on this theory an attempt to determine the optimal geometry of the flowmeter oscillator has been made. The achievement of maximum active forces acting on the oscillator as the effect of the fluid flow has been accepted as the criterion of optimisation. Then the oscillation energy of the optimised oscillator is greater. It means that the optimised flowmeter has a greater range and resistance to dirt and is more resistant to oscillator bearing wear. The analysis shows that the improvement of oscillator geometry is possible. Experimental verification of theoretical analysis (using an 8 inch model and visualisation) has confirmed its results. The optimisation has also made it possible to change the form of flowmeter body section—from rectangular to circular. It significantly decreased the pressure drop. The properties of the flowmeter also depend on fluid density, viscosity and compressibility. The final part of the paper deals with the minimisation of the viscosity influence on characteristics of the flowmeter. Some operational properties of flowmeter have been discussed.

Introduction Abnormal metal ion release from wear of metal-on-metal (MoM) bearing in total hip arthroplasty (THA) is associated with adverse local reactions to metal debris (ARMD). Metal particles may also arise from wear and corrosion of the implant's modular junction. The aim of this study was to compare ion levels and rate of ARMD between patients with THA sharing the same MoM bearing but one group having monoblock stems versus another group having modular stems. Materiel et methodes This study included 45 patients who underwent primary MoM THA using the same acetabular component and large diameter metallic modular femoral head. 32 hips received a modular stem and 13 hips received a monoblock stem. Cobalt (Co) and chromium (Cr) ion concentrations, ARMD rate and function measured by UCLA and WOMAC scores were compared between groups. Resultats ARMD rate was significantly lower in the monoblock group (16%) compared to the modular group (46%, P = 0.031). Revision for ARMD was performed at 115 ± 5.9 months after primary THA in the monoblock group versus 63 ± 2.3 months in the modular group. ARMD cases had severe wear and corrosion of the junction between stem and femoral head trunnion in all monoblock cases and the junction between stem and modular neck in all the modular ones. Cr and Co ions levels were significantly lower in the monoblock stem group: 2.0 ± 1.0 μg/L vs. 7.2 ± 11.4 μg/L (P Discussion The rate of ARMD was significantly higher in the modular stem group and this group required revision earlier. Although both groups had MoM bearings, corrosion at stem/neck or neck/head junctions were seen as the source of excessive metal ions release lea. Conclusion In the presence of ARMD, MoM bearing wear may not be the main source of failure. Modular junction's poor performances may be more deleterious than the bearing. To avoid such complication, THA femoral stem modular junctions should be eliminated (return to a full monoblock implant) or have improved junction design.

Wear and corrosion occurring in patients with hip and knee arthroplasty are common causes of failure leading to revision surgery. A variety of surgical approaches to these problems have been described, with varying efficacy. Polyethylene wear, metal-on-metal (MoM) hip bearing wear, and problems associated with modular taper corrosion are the areas of greatest clinical impact; results of revisions for these problems are likely to dictate a large portion of revision resources for the foreseeable future, and so they call for specific study.We identified the most frequently reported procedures to treat hip polyethylene wear, knee polyethylene wear, MoM wear after THA, and modular taper corrosion and determined the timing and reasons these failed.We performed systematic reviews of the published literature on the four topics using MEDLINE(®) and Embase in October 2013; searches were supplemented by hand searches of bibliographies. Prespecified criteria resulted in the identification of 38 relevant articles, of which 33 were either case reports or Level IV evidence. Followup was generally at short term and ranged from 0.2 to 8 years.The most frequently reported procedures for treating clinically important wear were a partial or complete revision. When treating polyethylene wear, the more frequently reported reasons for hip and knee rerevisions were loosening, continued wear, and instability. Soft tissue reactions were more common and occasionally extensive in patients with MoM or modular taper corrosion. Patients with soft tissue reactions had more complications and higher rerevision rates.Studies with longer followup and higher levels of evidence are needed to direct the treatment of wear and corrosion. When soft tissue damage secondary to MoM wear or taper corrosion is present, the results of treatment can be poor. There is an urgent need to better understand these two mechanisms of failure.

Wear and corrosion in joint arthroplasty are important causes of failure. From the standpoint of current clinical importance, there are four main categories of wear and tribocorrosion: polyethylene wear, ceramic-on-ceramic (CoC) bearing wear, metal-on-metal (MoM) bearing wear, and taper tribocorrosion. Recently, problems with wear in the knee have become less prominent as have many issues with hip polyethylene (PE) bearings resulting from the success of crosslinked PE. However, MoM articulations and taper tribocorrosion have been associated with soft tissue inflammatory responses, and as a result, they have become prominent clinical concerns. WHERE ARE WE NOW?: For PE wear in the hip, several advances include improved locking mechanisms and data supporting highly crosslinked polyethylenes (HXLPE). Edge-loading in CoC articulations can contribute to stripe wear and subsequent squeaking. For MoM articulations, the relationship of wear-to-edge loading, sensitivity to component positioning, typical soft tissue response, and use of imaging is increasingly understood. Taper tribocorrosion (from femoral head-neck junctions and other modular elements) and associated soft tissue inflammatory responses appear to be serious clinical issues that are not fully understood. WHERE DO WE NEED TO GO?: In the knee, clinical concerns remain with the efficacy of HXLPE, modular connections, and metal allergies. For PE wear in the hip, concerns remain regarding how to increase crosslinking of PE while minimizing PE fractures. With CoC articulations, questions remain on how to prevent noises, chipping, and impingement and if enhanced designs can contribute to improved results. For MoM articulations, we need to improve imaging tests for soft tissue reactions, determine best practices in terms of monitoring protocols, and better define if, how, and when to act on serum metal levels. For taper tribocorrosion, we need to use modularity wisely and also understand how to improve tapers and materials in the future. For patients at risk for tribocorrosion, we need to define realistic diagnostic and monitoring protocols. We also need to enhance revision methods, and the threshold of acceptable soft tissue damage, to minimize complications associated with soft tissue damage such as hip instability. HOW DO WE GET THERE?: HXLPE and other bearing surfaces will likely continue to be refined. We need to develop tapers with more resistance to tribocorrosion through improved understanding of the manufacturing process and ongoing engineering improvements. Revision procedures for wear and tribocorrosion can be enhanced by determining when partial component retention is appropriate and how best to manage soft tissue damage. For CoC articulations, enhanced designs are required to minimize noises, chipping, and impingement. Importantly, we must continue to promote and analyze joint replacement registries to identify early failures and analyze long-term successes.

Recent engine bearings have been operating under harsh conditions. Consequently, wear propagates for a short time and fatigue sometimes occurs on the bearings. On the rig test machine, the operating conditions of engine bearing were simulated to reproduce the bearing damage. The bearing wear was measured until a fatigue crack occurred. The bearing wear increased at the edges of the bearing length and the crack was also observed near the edges. The experimental results were compared to the calculated results based on the elastohydrodynamic lubrication (EHL) theory. The correlations between the bearing damage and bearing performance by theoretical analysis were investigated.

Solid debris particles in a lubricant can become entrained into the contacts of ball bearings. The particles damage the bearing surfaces. This can lead to rolling contact fatigue failure or material loss by three body abrasion. This work concentrates on modelling the later process for brittle debris materials. A brittle particle is crushed in the inlet region and the fragments are entrained into the contact. Rolling bearing contacts (because of the high degree of conformity) are subject to contact microslip. When this slip takes place, the trapped particle scratches the bearing surfaces. Repeated scratching by many particles results in substantial material removal. Although this failure mechanism is usually not as rapid as debris initiated fatigue, it is frequently important in mineral handling or desert environment rolling bearing applications. A simple model has been developed which considers the wear as the sum of the individual actions of each particle. The number of debris particles is determined by considering the volume of oil entrained into the bearing contacts and an empirically derived `particle entry ratio'. The abrasive action of each particle is determined by the volume of material displaced during sliding and another empirical factor for the proportion of this removed as a wear particle. The predictions are compared with some experimental results. The correlation between bearing wear and the debris particle size is encouraging.

Electrical generators and other drive-train components experience significant varying loads in wind turbines. This can lead to bearing failure due to unbalanced forces caused by misalignment and rotor eccentricity. This paper presents an analytical model to determine the radial force induced in 50KW air-gap winding permanent magnet generators in wind turbines due to static rotor eccentricity. The model has been verified with 2D electromagnetic finite element analysis software. Depending on fault frequency, Stator currents have been analysed in order to detect bearing wear type (inner race defect, outer race defect or bearing defect).

An impeller pump has been evaluated chronically in calves as a left ventricular assist device. In a group of 18 calves, three survived approx. 2 months (62, 54 and 46 days, respectively) while earlier calves survived less than 14 days. The termination of the experiments was due to bearing wear, which resulted in pump failure. The pump delivered nonpulsatile or pulsatile blood flow, according to the heart function. All the haemochemical data remained within normal or acceptable ranges during the experiments. Further improvement is now concentrated on developing a magnetic bearing to solve the problem of bearing wear.

The foaming and aeration properties of crankcase oils were investigated through the observation of foam behavior in the crankcase. Entrained air bubbles in the crankcase oil, that is oil aeration, increased as engine speed and oil temperature increased. This also depended on oil formulation. However, surface foam disappeared in high-speed conditions. It was found that the aeration performance of oils had an effect mainly on the connecting-rod bearing wear under high speed-high temperature engine operating conditions.

In order to efficiently improve engine bearing durability, we investigated the feasibility of predicting the durability of actual engine bearings by means of hydrodynamic lubrication computations. This paper describes a method of predicting the amount of actual engine bearing wear based on the results of a numerical analysis (EHL analysis) which takes into account the pressure dependence of lubricant viscosity and the elastic deformation of the bearing housing. The wear shape predicted by this method serves as input data for the EHL analysis calculations. The results show that variations in bearing performance caused by wear are substantial. Analyses that incorporate wear shape data make it possible to examine durability under conditions that more closely approximate actual conditions.

A rotor-bearing system is simulated in this study to investigate the effect of worn journal bearings on the system response and to specify the eventual development of additional frequency components. The well-known symmetric Dufrane bearing wear model is used here. The main target here is the investigation of the wear influence on the system response. An experimental layout was constructed for the needs of the current research, including an artificially worn bearing. It was observed that sub- and superharmonics are revealed in the continuous wavelet transform (CWT) of the rotor-bearing system response for worn bearings.

To estimate the lifetime of the pivot bearing system of the sealless centrifugal Gyro C1E3 pump, pivot bearing wear phenomena of the C1E3 were studied. The pivot bearing system consisted of a male and female pivot made of ceramics and ultrahigh molecular weight polyethylene (UHMWPE), respectively. First, many pumping tests were performed with the C1E3 under various pumping conditions, and the effects of impeller position and fluid on wear were analyzed. Through these preliminary tests, it was found that the wear progress of the pivot bearing consisted of initial wear and stationary wear. Most of this initial wear is caused by the plastic deformation of the polyethylene female pivot. It also was observed that bovine blood was almost comparable to water in its effect on the stationary wear rate at the same rotational speed. Based on these results, a long-term pumping test was performed with the C1E3, and initial and stationary wear rates were determined. At the same time, the maximal loosening distance (LDmax) (permissible total wear) of the C1E3 was determined experimentally from hemolytic and hydraulic performance perspectives. By using experimentally determined parameters the lifetime of the pivot bearing system of the C1E3 pump was estimated for various pumping conditions. The lifetime of the pivot bearing system of the C1E3 was typically 10 years for right ventricular assist, 8 years for left ventricular assist, and 5 years for cardiopulmonary bypass.

Hip resurfacing is now becoming an established alternative to total hip replacement in the young, high-demand patient with end-stage hip arthritis. Many of the complications and early failures of the previous generations of hip resurfacing appear to have been eliminated with the most recent hip resurfacing systems. The literature now contains excellent short- and medium-term results of the new generation of hip resurfacing (Amstutz et al. 2004a, b; Amstutz and Le Duff 2008; Daniel et al. 2004; McMinn and Daniel 2006; Treacy 2006). The advantages of preservation of proximal bone stock, low dislocation risk and excellent bearing wear characteristics make hip resurfacing an attractive alternative to total hip replacement. However, concerns over the risk of implant failure persist.

Preclinical testing is a critical part of the orthopaedic device design process and is required to demonstrate efficacy, safety and adherence to the requirements of essential regulations. The following chapter provides an overview of the key regulatory and technical requirements associated with mechanical and tribological testing of orthopaedic devices and the characterization of metallic coatings applied to such devices for improved biological fixation. Mechanical testing is typically carried out according to regional or international standards that define the type of device to be tested, its laboratory-based performance requirements and reference criteria that a product must meet. The most widely used tests for orthopaedic devices are static or fatigue tests. These may be conducted under compression, bending, shear or torsion, depending on the in vivo loading conditions that they are trying to replicate. Bearing wear simulator test methods have evolved over several decades from simpler tests such as pin-on-plate to more realistic tests that replicate the forces and motions experienced during walking or other gait cycles and, importantly, allow the testing of actual components. Current wear simulator test standards for hip and knee joints are reviewed and methods of characterizing wear debris and measuring friction are discussed. Metallic coatings on orthopaedic devices can be employed to improve the fixation of the implant to the host bone. This chapter discusses methods to characterize critical properties of metallic coatings for orthopaedic devices and also identifies the acceptance standards set by regulatory bodies for these kinds of coatings.

The primary objective of this study was to evaluate bearing wear during clinical use of the HeartMate II (HMII) left ventricular assist device. Bearings obtained from HMII pumps explanted after clinical use in the Destination Therapy and Bridge to Transplantation clinical trials were analyzed for wear using surface profilometry. Geometric profile variations measured on the inlet bearing ball were used to calculate the wear. Bearing wear was normalized to the total pump support duration to obtain an annualized bearing wear rate. Bearing life was estimated assuming a linear wear rate, as the time to reach a wear limit of 25 µm, which includes a 3× safety factor, to ensure that there is no contact between the rotor blades and the blood bore housing. One hundred and eighty-three bearings from left ventricular assist devices implanted in 181 patients were analyzed. Average age of the patients was 56.3 ± 14.6 years, 76% were male, 46% had an ischemic etiology of heart failure. Mean support duration for the pumps was 363 ± 349 days (median: 238, range: 1-1,621 days). Sixty pumps (33%) were explanted at heart transplantation, 20 (11%) after device replacement, 6 (3%) for ventricular recovery, 94 (51%) after patient death, and 3 (2%) were explanted for other reasons. Mean bearing wear was 0.59 ± 0.37 µm (median: 0.46 µm [5-95% interval: 0.25-1.48]). The median bearing wear rate for patients supported for at least 1 year was 0.30 [5-95% interval: 0.09-0.94] µm/yr. The 5-95% limits of the bearing wear rate corresponded to an estimated bearing life between 27 and 269 years. The pump having the highest bearing wear rate (1.46 µm/yr) had an estimated bearing life of at least 17 years. HMII bearing wear is extremely small, with an estimated bearing life well in excess of 17 years; it is not a limiting factor for long-term support with the HMII left ventricular assistive system.

Rotating-platform TKA, although purported to have superior kinematics, has shown no clinical advantages over those of fixed-bearing TKA. Our design-matched retrieval study aimed to investigate if differences in bearing wear damage exist between fixed- and mobile-bearing TKAs with similar condylar geometry.We asked whether (1) the rotating platform's more conforming tibiofemoral articulation would be associated with less severe damage; (2) the location of damage and wear would be similar on the tibiofemoral or backside surfaces of two contemporary designs with similar condylar geometry; and (3) the combined damage and deformation measured as thickness would differ between the two designs.We performed damage grading and damage mapping on 25 rotating-platform and 17 fixed-bearing inserts. The patient demographic data from each of these cohorts were comparable. Inserts were also laser-scanned from which we obtained thicknesses, and inferior surface three-dimensional scans, from which we determined dimensional changes.Rotating-platform and fixed-bearing inserts had similar tibiofemoral damage scores. However, the scores on the inferior surface of rotating platforms were greater, often as a result of third-body debris scratching observed on both damage mapping and three-dimensional scans. The extent of damage as a function of surface area was greater for rotating platforms, consistent with the greater tibiofemoral conformity. Dimensional changes on the inferior surfaces of the fixed bearing followed loading areas of the knee. However, no differences were seen in the thicknesses between fixed- and rotating-platform bearings.The increased total damage score on the rotating platform, coupled with increased surface area damaged and the propensity for third-body debris, indicates no damage advantage to this mobile-bearing design.

This paper deals with the early detection and monitoring of possible bearing damage of variable-speed, converter-fed electric motors. After a brief description about the issue of bearing currents in converter-fed drives, the main subject will be outlined with the focus on practical experience. A measurement systemology is used for this purpose, where the electrical measurement of bearing current events as well as the mechanical measurement of the vibration status of the bearing is taken into account. A comparison between different vibration measurement methods leads to a systemology, which allows to detect possible changes in the motor bearing in a very early state of operation.

Publisher Summary This chapter discusses lubricants for drilling applications. One of the greatest challenges in the formulation of specialty lubricants for drilling applications is the prevention of drill bit bearing wear in subterranean formations. In such applications, lubrication takes place in an abrasive environment of mud and rock particles deep below the earth's surface. Extensive laboratory work has been carried out to determine the performance of a number of lubricants including tests to determine the potential for formation damage of several types of drilling fluids, as well as the reduction in the friction coefficient. There are monographs on the issues of synthetic greases, including their application in petroleum industries. Synthetic greases have considerable advantages over conventional hydrocarbon-based greases including: high viscosity with good pumpability, lower torque, ability to function at lower operating temperatures, and excellent thermal and oxidative stability. Many of these advantages arise from the use of controlled synthesis, which yields products with exact properties. These benefits have led to the development of many commercial synthetic types of grease for a variety of uses.

The competition and high precision requirements in manufacturing processes have forced companies to develop and implement automated manufacturing cells on the factory floor. However, due to the high precision requirements of these cells, small changes in the cell components, such as bearing wear, clamp wear, and sensor loss of sensitivity, can degrade their performance such that they fail to function properly. Furthermore, on-line direct measurement of the condition of cell components is very difficult. This paper presents on-line and off-line algorithms that use redundant sensory information to determine the condition of these cell components without directly measuring them. The effectiveness of these algorithms has also been tested and confirmed on the factory floor. This work suggests that for higher productivity, high precision manufacturing cells should have self-diagnosis capability to predict which parts need repair or maintenance. >

The real-time prediction of bearing wear for roller cone bits using the Intelligent Drilling Advisory system (IDAs) may result in better performance in oil and gas drilling operations and reduce total drilling cost. IDAs is a real time engineering software and being developed for the oil and gas industry to enhance the performance of complex drilling processes providing meaningful analysis of drilling operational data. The prediction of bearing wear for roller cone bits is one of the most important engineering modules included into IDAs to analyze the drilling data in real time environment. The ‘Bearing Wear Prediction’ module in IDAs uses a newly developed wear model considering drilling parameters such as, weight on bit (WOB), revolution per minute (RPM), diameter of bit and hours drilled as a function of IADC (International Association of Drilling Contractors) bit bearing wear. The drilling engineers can evaluate bearing wear status including cumulative wear of roller cone bit in real time while drilling, using this intelligent system and make a decision on when to pull out the bit in time to avoid bearing failure. The wear prediction module, as well as the intelligent system has been successfully tested and verified with field data from different wells drilled in Western Canada. The estimated cumulative wears from the analysis match close with the corresponding field values.Copyright © 2011 by ASME

Although the origin of the development of alumina as a biomaterial can be traced back to 1930, its successful use as a biomaterial is based on the studies carried out in the early 1970s in France, Germany, and Japan. Alumina has 40 years of clinical record in the field of orthopedics, where it is used in the manufacture of balls and cups for hip replacements and has proven its effectiveness in limiting the bearing wear. The arthroplasty of the hip is one of the most successful surgeries, with very positive outcomes but its success is hampered in a number of cases by the insurgence of osteolysis, a device-induced pathology, which also arises out of the reactions induced by the wear debris. This explains the interest shown in minimizing the wear of bearings in arthroplasty and the continuous efforts taken to improve the materials selected for this task. This chapter outlines, from an historical perspective, the development of alumina as a biomaterial, reviews the properties of this ceramic that are relevant for its clinical use, with emphasis on the studies performed on the biological safety of alumina and of its wear debris. Special attention is devoted to the use of alumina in total hip replacement (THR) bearings, which is the main application of alumina as a biomaterial today, while a section is devoted to the use of this ceramic biomaterial in the knee and to the ongoing development of alumina matrix composites.

The basic interrelationships that are required to investigate the cross-system subject of “bearing currents in converter operation”, are discussed in this paper. In order to obtain an integrated overview of the situation, it is decisive that the main points of the investigation are not discussed individually, but must be considered from an overall point of view. Results from the parameter test area and their link to the overall situation are shown. Higher-level systemology to simulate electric currents flowing through a bearing is outlined, taking into account the various processes that take place in the bearing. The paper is completed by presenting a new type of bearing current sensor system. A review of the steps still required is provided in the conclusion.

This paper deals with the diagnosis of faults in roller-element bearings as the core of a dedicated Condition based Maintenance (CBM) system. Vibration signals recorded by accelerometers feed into a classification model in charge of monitoring and evaluating bearing wear. The chosen feature extraction technique is based on the computation of the Discrete Fourier Transform (DFT) and on the estimation of the normalized frequency content in each of the considered spectrum sub-bands as an indicative measure of the state of health of the roller-element bearing. Three different damage attributes have been investigated. For each attribute, both Support Vector Machines (SVM) and neurofuzzy Min-Max classifiers have been employed as the core of the diagnostic system. Test results show that it is possible to achieve high accuracy in all diagnostic problems considered. The pre-processing procedure and the classification stage, especially in the case of Min-Max fuzzy networks, do not require demanding computational hardware resources, and as a result, a simple and effective diagnostic system can be designed by feeding the synthesized Min-Max classifiers with the spectral features computed from vibration sensor outputs.

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During running-in conditions, contact occurs between surface asperities, which induce wear and bearing shell profile adaptation. Firstly, the bearing wear evolution is investigated for different but constant engine rotational speeds. Secondly, the wear is investigated for transient speed conditions. By comparison with a realistic wear coefficient, the real engine time required to reach a steady-state wear condition is predicted.Copyright © 2010 by ASME

Bearing failure of roller cone bits may result in a time-consuming fishing job, and lead to significant increase in drilling costs. The bearing failure generally comes from over wear of frictional pairs (surfaces between the journal and bearing of the cone). A bearing wear model has been developed to predict the wear status through multi-variable nonlinear regression analysis based on field data. The wear model considers four variables including weight on bit (WOB), revolution per minute (RPM), diameter of bit and hours drilled as a function of IADC bit bearing wear. Some abnormal bit run field reported bearing failures were removed in order to acquire the best regression of the field data. A bearing failure probability model is then introduced to predict the survival probability of the bit, the parameter of which is obtained through statistics of more than 500 bit runs. The wear status, including instantaneous and cumulative wear, for different roller cone bits and different wells drilled in Western Canada is simulated respectively with the wear model. A good correlation coefficient was obtained for different IADC bit types including both milled tooth and insert roller cone bits. The cumulative wear values from the model match close those from the field. The wear model and the failure probability model can help drilling engineers evaluate bearing wear status during real time drilling operations through simulation, and make a decision on when to pull out the bit in time to avoid bearing failures and the possibly lost cones. Better bearing wear predictability will result in better drilling results and effect the total drilling cost.

The main research of the thesis was based on the analysis to the wearing and plugging in the pneumatic conveying pipeline and the elaboration on the mechanism of the accident. Several methods of dealing with ash blocking and several kinds of pipelines which fit for decreasing wear and bearing wear in the pneumatic conveying system were introduced.

This paper deals with the detection of worn rolling bearings in asynchronous machines using electrical measurements and estimated mechanical variables. These two approaches are based on the use of the available electrical quantities, e.g., the machine stator currents, which are often already measured for control and protection purposes. Considering that bearing faults induce load-torque oscillations, a theoretical stator-current model, in case of load-torque oscillations, is recalled. Then, a theoretical estimated rotor flux and estimated speed model demonstrates the presence of harmonics related to load-torque oscillations. Phase-modulation components on stator current and harmonics on estimated speed can be used for detection purposes. The frequency behavior of monitored quantities with regard to the load-torque oscillation frequency is particularly investigated. Fault detectors are then proposed on monitored variables. The efficiency of the indicators is studied for different operating points considering the frequency behavior of the system. Finally, the use of detectors is discussed regarding the supply-frequency range usable for the detection.