Investigation of diesel soot-mediated oils and additive package on wear

In the current study, a statistically designed experiment was developed to study the effects of soot contaminated engine oil on wear. The variables that were considered were the Base stock (Group1, Group2), Dispersant level and ZDP level. The above three variables were formulated at two levels: Low (-1), and High (1), which resulted in 23 matrix (8 oil blends). Soot was also one of the variables and was tested at three levels: Low (-1), Medium (0) and High (1).;A three-body-wear machine was employed to simulate and estimate the extent of wear, as it is very difficult to test each oil sample on an engine. The extent of wear was measured as the actual loss of material, in milligrams. A second set of experiments was performed on a milling machine (Ball-on-flat-disc setup) using a specially designed chuck and aluminum cup. The wear scars formed on the steel ball were measured using a Scanning Electron Microscope (SEM). These wear scars were analyzed qualitatively to determine the effect of soot-contaminated oils on wear.;A third set of experiments involved measuring the viscosity of the various oil formulations at 40°C and 90°C to examine the influence of soot present in the oil. (Abstract shortened by UMI.)

The Effect of Dissolved Water on the Tribological Properties of Polyalkylene Glycol and Polyolester Oils

The effect of water dissolved in polyalkylene glycol and polyolester oils on the tribological behavior of two material contact pairs in three test environments is evaluated. The material contact pairs are M2 tool steel against 390 aluminum and M2 tool steel against gray cast iron. The three oils are a polyalkylene glycol (PAG) and two polyolester (PEl and PE2) oils. The test environments are R134a, air and argon. The tests are conducted in a specially designed high pressure tribometer which provides an accurate control of the test variables. The results indicate that the P AG oil performed better than the esters for both material contact pairs. The wear on the aluminum plates for the tests conducted with the P AG oil in all three environments is greatest at the lowest moisture content levels. From the stand point of friction and wear, it is beneficial to have a water content level of 5000 ppm or greater in the PAG oil when the plate material is 390 aluminum. The wear on the cast iron plates, when using a PAG oil as the lubricant showed a slight increase with water content in a R134a environment. This trend is opposite when air is the test environment. Both ester oils lubricated aluminum much better than the cast iron . The difference in the amount of wear can be as high as two orders of magnitude. This is probably due to the ability of the esters to form bidentate bonds with aluminum. Esters do not form such bonds with iron. The plate wear is greater for the PEl tests than for the PE2 tests for both material contact pairs. This is most likely due to the difference in the viscosity of the oils. In PE2 oil, water does not seem to affect the friction and wear of both aluminum/steel and cast iron/steel contacts when R134a is the test environment. On the contrary, for the aluminum/steel contacts, the water content significantly influences wear when argon or air is the test environment. For the cast iron/steel contacts, the wear is strongly influenced by the water content when the test is conducted in argon, but it is not influenced by the water content when the test is conducted in air.Air Conditioning and Refrigeration Center Project 0

Evaluation of 1,3-diketone as a novel friction modifier for lubricating oils

With the growing demand in both lubrication performance and environmental protection, it is eager to seek novel lubricant additives of good oil miscibility and high tribological efficiency but without harmful elements such as sulfur and phosphorus. As a recently developed material with superlubricity (μ < 0.01), 1,3-diketone EPND (1-(4-ethyl phenyl) nonane-1,3-dione) could modify the contacts of steel surfaces through the tribochemical reaction with iron and also exploit strong intermolecular forces to control the near surface fluid interactions. Owing to its oil-soluble nature, EPND also shows the potential functioning as an additive in lubricating oils. In this study, EPND was introduced into both pure base oils and fully-formulated oils to evaluate its performance as a novel friction modifier. The results suggest that with small influences on the viscosity and oxidation stability in the blended oil, EPND leads to an effective friction reduction in both boundary and mixed lubrication regimes. Moreover, the addition of EPND enhances the oil extreme pressure capacity as well. This work indicates that 1,3-diketone is a promising friction modifier even in the presence of some other commercial additives

Data-based ensemble approach for semi-supervised anomaly detection in machine tool condition monitoring

Data-based methods are capable to monitor machine components. Approaches for semi-supervised anomaly detection are trained using sensor data that describe the normal state of machine components. Thus, such approaches are interesting for industrial practice, since sensor data do not have to be labeled in a time-consuming and costly way. In this work, an ensemble approach for semi-supervised anomaly detection is used to detect anomalies. It is shown that the ensemble approach is suitable for condition monitoring of ball screws. For the evaluation of the approach, a data set of a regular test cycle of a ball screw from automotive industry is used

Friction and wear performance analysis of hydrofluoroether-7000 refrigerant as lubricant

The disquiet about global warming has triggered the formulation and introduction of new generation of refrigerants. Hydrofluoroethers (HFEs) are within the family of newly developed environmentally friendly refrigerants with a wide range of application areas. Hydrofluoroethers reportedly have better heat transfer and thermodynamic properties. In addition to an understanding and knowledge of the thermodynamic properties of refrigerants, it is essential to understand the tribological properties of refrigerants within the context of sustainable development. Tribo-performance of refrigerants applied in refrigeration, air-conditioning and energy systems directly influences the durability, reliability and cost effectiveness of the system. HFE-7000 has considerable potential for engineering applications in green energy and low carbon technologies. In this research, a detailed investigation has been performed to assess friction and wear performance of HFE-7000 (HFE-347mcc3). HFE-7000 has been employed as lubricants. Experimental results indicate the formation of tribo-films on the topmost surfaces. Energy-Dispersive X-ray Spectroscopic (EDS) and X-ray Photoelectron Spectroscopic (XPS) analyses on the tested samples revealed significant presence of oxygenated and fluorinated anti-wear tribo-films. These oxygen and fluorine containing tribo-layers prevent metal to metal contact and contribute to the reduction of friction and wea

High Fidelity Model of Ball Screws to Support Model-based Health Monitoring

L'abstract è presente nell'allegato / the abstract is in the attachmen

Slip in radial cylindrical roller bearings and its influence on the formation of white etching cracks

Ungünstige Betriebsbedingungen und unzureichende Radialkräfte führen zu Schlupf in Radial-Zylinderrollenlagern. Das kann zu verschiedenen Ausfallmechanismen, wie Anschmierung, Fressschäden, Abplatzen und auch sogenannten White Etching Cracks (WEC) führen, die bereits nach einem Bruchteil der berechneten Lagerlebensdauer auftreten können. In dieser Arbeit wird durch systematische Tests der Einfluss der Lagerbetriebsbedingungen (Radialkraft, Drehzahl und Öldurchfluss), sowie der Ausführung des Lagers (Lager- und Käfigtyp, Material, Führung und Toleranzklassen) auf die Entstehung des Wälzkörper- und Satzschlupfs untersucht. Die Wälzkörper vollrolliger Lager in der lastfreien Zone werden verzögert und sind in der Beschleunigungsphase einem vollständigen Rollenschlupf ausgesetzt. Für mit Käfig ausgestattete Zylinderrollenlager übertrifft der einteilige den zweiteiligen Käfig durch eine geringere Schlupfneigung, besonders unter begrenztem Öldurchfluss. Rollengeführte Käfige zwingen die Rollen dazu mit dem rotierenden Innenring zu interagieren, wodurch weniger Schlupf verursacht wird. Polyamid als Käfigwerkstoff bietet Gewichteinsparungen, wird aber bei hohen Lagertoleranzen nicht empfohlen, da es deformiert und somit einen höheren Schlupf bewirkt. Bei moderaten Lagertoleranzen tragen mehr Rollen zur Belastungsübertragung bei. Das kann zu höherem Rollenschlupf als bei hohen Toleranzen führen, da verringerte Traktionskräfte auf die Rollen wirken. Wird ein Lager jedoch durch eine enge Toleranzklasse (TC) vorgespannt, kann der Schlupf unter jeglichen Betriebsbedingungen verhindert werden. Der Einfluss von Schlupf auf die Bildung von WEC am Innen- und Außenring eines Zylinderrollenlagers wurde in insgesamt vier Dauerlaufversuchen mit einem zweiphasigen Belastungsschema untersucht. Während der Niedriglastphase wird das Lager bei erhöhtem Schlupf betrieben und danach einer hohen Lastphase ausgesetzt, während der Ermüdungsrissfortschritt von WEC auftreten kann. Es wurde festgestellt, dass Betriebsbedingungen mit hohem Schlupf weniger kritisch für die WEC-Bildung (an beiden Lagerringen) sind. Die sehr geringe Radialkraft, die in der Niedriglastphase aufgebracht wird, um einen hohen Schlupf zu ermöglichen, führt zu einer geringen Flächenpressung, die nicht WEC-kritisch ist. Ein weiterer Grund ist die längere Regenerationszeit zwischen zwei Überrollungen, die bei einem hohen Sollschlupf auftreten. Kritischer sind die dynamischen Kraftverhältnisse für die stehenden Lagerringe. Sie würden den Rollenschlupf unter der wechselnden Lastzonenbreite akkumulieren, was WEC-kritischer ist. Obwohl die vollrolligen Lager einen hohen Satzschlupf und 100%igen Rollenschlupf in der Lastzone erleiden, zeigten sie auch nach mehr als 3400 Teststunden, unter den für Käfiglager sehr kritischen Prüfbedingungen, keine Anzeichen eines WEC-Ausfalls.Unfavorable operating conditions and inadequate radial force cause slip to occur in radial cylindrical roller bearings. This can also lead to several failure mechanisms such as smearing, scuffing, spalling, and White Etching cracks (WEC) that can occur at a small percentage of the calculated bearing life. In this work, through systematic testing, the influence of the bearing operating conditions (radial force, speed, and lubricant flow rate) as well as the bearing’s design (bearing type, cage type, material, guidance as well as the clearance class) on the development of the roller- and the rolling set slip was studied. The rollers of the full complement bearing stall in the load-free zone, and they suffer from a 100% roller slip at the acceleration zone. For caged bearings, a single-part cage outperforms the two-part cages by having lower slip tendency under restricted oil flow rates. Cages that are roller-guided force the rollers to interact more with the rotating inner ring and thus suffer from an overall lower slip. For the cage material, Polyamide cages offer weight savings. However they are not recommended under elaborated clearance as they would deform and cause high slip. Under moderate clearance, more rollers contribute to the load transfer. This leads to higher roller slip than under higher clearance level due to the decrease in traction forces acting on each roller. However, preloading a bearing by using the TC clearance class while using a tight fitting for both rings my lead to the elimination of the slip under any operating conditions. The influence of slip on the formation of WEC on the inner and outer rings of a cylindrical roller bearing was studied by conducting a total of four endurance tests using a two-phase loading scheme. In the low-load phase, a slip-rich environment is introduced to the bearing during which lubricant smearing can take place. After that, a high load phase is introduced to the bearing during which, fatigue crack propagation of WEC is enabled. It was found that high-slip operating conditions are less critical for the WEC formation on both bearing rings. The very low radial force that must be used in the low load phase to allow such a high slip to occur would result in a low contact pressure that is not WEC-critical. Another reason is the longer regeneration time between two overrollings occurring at a high set slip. Dynamic force conditions are more critical for the stationary bearing rings. They would accumulate the roller slip under the changing load zone width which is more WEC-critical. Although suffering from high set slip and 100% roller slip in the load zone, full complement bearings didn’t show any sign of WEC failure even after testing them for more than 3400 hours under very critical testing conditions for caged bearings

Influence of plasma pre-treatment of polytetrafluoroethylene (PTFE) micropowders on the mechanical and tribological performance of polyethersulfone (PESU)-PTFE and impact modified polyamide (PA66)-PTFE compounds

Polytetrafluoroethylene (PTFE), (CF2-CF2)n exhibits a low coefficient of friction (CoF, 0.07 - 0.15) and is therefore widely used as an additive in polymer compounds to improve their friction and wear properties. However, its applications in polymer compounds are limited due to the PTFE’s inherent poor chemical reactivity, low wettability and poor adhesion with other polymers preventing the establishment of good interfacial bonding. To overcome this, the work introduces plasma treatment of PTFE micropowders in a low-pressure 2.45 GHz microwave plasma reactor, using NH3 and H2 as process gasses to chemically modify their surface by introducing surface nitrogen and oxygen polar groups leading to more hydrophilic surfaces. The presence of these functional groups enhances the surface energy of the plasma treated PTFE and enhances the compatibility with thermoplastic polymers. It must be emphasised that nearly all the literature existing on the surface functionalisation of PTFE focuses on the PTFE films only. The first publication from this research work, in the group of three, reports on the effects of the H2, NH3 plasma processing time (2.5, 10 h), resulting defluorination (1.13 for NH3/10h, 1.30 for H2/10h as compared to 1.86 for pristine PTFE) and measurement of changes in wettability and crystallinity of the PTFE micropowders. The resulting plasma modified PTFE micropowders were further used as dry lubricants to enhance the tribological and mechanical properties of amorphous polyethersulfone (PESU) and semi-crystalline α-olefin-copolymer impact-modified polyamide 66 (PA66i) polymer compounds resulting in the next two publications. At the same loading levels (10wt%) of PTFE, prepared using twin-screw compounding, the pinon- disc tribological measurements of the PESU-PTFE compounds revealed a lowCoF from 0.55 for pristine PESU to 0.20 along with corresponding reduction in the wear rates from 5.75 x 10-06 mm3/Nm (pristine PTFE) to 4.70 x 10-06 mm3/Nm (for H2 treated PTFE) to 3.42 x 10-06 mm3/Nm (for NH3 treated PTFE). In the PA66i matrix, the wear rates of the pristine and plasma treated PTFE were observed to be similar for the sliding speeds up to 2 m/s. However, at the higher sliding speeds, the benefits of plasma treatment became more apparent. At the sliding speed of 3 m/s, the wear rate of pristine PTFE-PA66i compound was 1.1 x 10-06 (± 0.2) mm3/Nm whereas the wear rate of H2 treated PTFE was 0.7 x 10-06 (± 0.1) mm3/Nm and the wear rate of NH3 treated PTFE was 0.6 x 10-06 (± 0.1) mm3/Nm. These improvements in the tribological and mechanical properties have been ascribed to the enhanced dispersion of PTFE in the host matrix with the plasma processing introduced functional polar groups providing enhanced intermolecular bonding (as confirmed using Fourier transform infrared spectroscopy, differential scanning calorimetry and dynamic mechanical-thermal analysis) between the components. Therefore, the incorporation of functional groups into PTFE micro-powders by plasma treatment is an effective and efficient route for enhancing the mechanical and tribological properties of engineering polymer compounds such as PESU-PTFE and PA66i- PTFE offering significant cost and environmental benefits over the existing e- beam and wet chemical technologies

Influence of plasma pre-treatment of polytetrafluoroethylene (PTFE) micropowders on the mechanical and tribological performance of polyethersulfone (PESU)-PTFE and impact modified polyamide (PA66)-PTFE compounds

Polytetrafluoroethylene (PTFE), (CF2-CF2)n exhibits a low coefficient of friction (CoF, 0.07 - 0.15) and is therefore widely used as an additive in polymer compounds to improve their friction and wear properties. However, its applications in polymer compounds are limited due to the PTFE’s inherent poor chemical reactivity, low wettability and poor adhesion with other polymers preventing the establishment of good interfacial bonding. To overcome this, the work introduces plasma treatment of PTFE micropowders in a low-pressure 2.45 GHz microwave plasma reactor, using NH3 and H2 as process gasses to chemically modify their surface by introducing surface nitrogen and oxygen polar groups leading to more hydrophilic surfaces. The presence of these functional groups enhances the surface energy of the plasma treated PTFE and enhances the compatibility with thermoplastic polymers. It must be emphasised that nearly all the literature existing on the surface functionalisation of PTFE focuses on the PTFE films only. The first publication from this research work, in the group of three, reports on the effects of the H2, NH3 plasma processing time (2.5, 10 h), resulting defluorination (1.13 for NH3/10h, 1.30 for H2/10h as compared to 1.86 for pristine PTFE) and measurement of changes in wettability and crystallinity of the PTFE micropowders. The resulting plasma modified PTFE micropowders were further used as dry lubricants to enhance the tribological and mechanical properties of amorphous polyethersulfone (PESU) and semi-crystalline α-olefin-copolymer impact-modified polyamide 66 (PA66i) polymer compounds resulting in the next two publications. At the same loading levels (10wt%) of PTFE, prepared using twin-screw compounding, the pinon- disc tribological measurements of the PESU-PTFE compounds revealed a lowCoF from 0.55 for pristine PESU to 0.20 along with corresponding reduction in the wear rates from 5.75 x 10-06 mm3/Nm (pristine PTFE) to 4.70 x 10-06 mm3/Nm (for H2 treated PTFE) to 3.42 x 10-06 mm3/Nm (for NH3 treated PTFE). In the PA66i matrix, the wear rates of the pristine and plasma treated PTFE were observed to be similar for the sliding speeds up to 2 m/s. However, at the higher sliding speeds, the benefits of plasma treatment became more apparent. At the sliding speed of 3 m/s, the wear rate of pristine PTFE-PA66i compound was 1.1 x 10-06 (± 0.2) mm3/Nm whereas the wear rate of H2 treated PTFE was 0.7 x 10-06 (± 0.1) mm3/Nm and the wear rate of NH3 treated PTFE was 0.6 x 10-06 (± 0.1) mm3/Nm. These improvements in the tribological and mechanical properties have been ascribed to the enhanced dispersion of PTFE in the host matrix with the plasma processing introduced functional polar groups providing enhanced intermolecular bonding (as confirmed using Fourier transform infrared spectroscopy, differential scanning calorimetry and dynamic mechanical-thermal analysis) between the components. Therefore, the incorporation of functional groups into PTFE micro-powders by plasma treatment is an effective and efficient route for enhancing the mechanical and tribological properties of engineering polymer compounds such as PESU-PTFE and PA66i- PTFE offering significant cost and environmental benefits over the existing e- beam and wet chemical technologies

33rd Aerospace Mechanisms Symposium

The proceedings of the 33rd Aerospace Mechanisms Symposium are reported. JPL hosted the conference, which was held at the Pasadena Conference and Exhibition Center, Pasadena, California, on May 19-21, 1999. Lockheed Martin Missiles and Space cosponsored the symposium. Technology areas covered include bearings and tribology; pointing, solar array and deployment mechanisms; orbiter/space station; and other mechanisms for spacecraft