Aus der Praxis für die Praxis of 200 h running time passed the test. During the tests the frictional torque and temperature were measured. The conditions for the test are shown in Table 1. Both the rollers and the disk (also called washer) materials are 100Cr6 (German standard corresponding to AISI52100). The washers tested at 80 °C passed the test, the average frictional torque reached a value of 10 Nm. The bearing tested at 100 °C failed the test (test length was 50 h), the average frictional torque was 8.5 Nm. Previous tests proved that bearings tested under this test conditions (100 °C) tend to early failure and WECs (White Etching Cracks) occured. These cracks occur under the surface of the bearing and lead to early failure. Ultrasonic measurements of the surface could prove damages under the surface on the high slip zone on the outer side of this bearing washer. For the bearings tested under a temperature of 120 °C the test length was 200 h (passing the test), the average frictional torque was 6 Nm. By increasing the temperature the frictional torque measured during the FE-8 test decreases. The change of the frictional torque can be referred to the decrease of the oil viscosity with increasing temperature. Figure 1 depicts the boundary layer on the surface of a bearing washer tested at 80 °C. The rolling contact area is clearly visible with a blue to red colour on the surface. The early failure of bearings due to WECs is correlated to the appearance of hydrogen on the steel surface. Due to hydrogen diffusion into the steel the risk of embrittlement increases, the hydrogen is generated by a catalytic reaction of decomposed lubricant and fresh steel surface [3]. Kohara concludes, that a film formed on the sliding surface by additives can reduce both hydrogen generation from lubricant and hydrogen penetration into the steel [3]. Also the additives of the oil and contaminations have an influence on the hydrogen uptake to the bulk steel [4]. Thus, the composition and structure of the formed boundary layers have a high influence on the early bearing failure. The fine structure of the boundary layers surface for a bearing washer tested at 100 °C is shown in Figure 2. According to Smith the structure is based on a ZDDP anti wear film, the roughness can be explained due to failures in the film formation or damages [5]. To investigate the frictional properties of the boundary layers, nanoscratch tests and micro pin-on-disk tests were performed. Before these tests the adhering oil on the axial bearing washers was removed with n-hexane. While the nanoscratch test allows to measure the frictional properties of the boundary layers during ploughing, the frictional sliding properties can be achieved with the micro pin-on-disk tests. To investigate the chemical composition of the layers Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) of the complementary bearing disks (i.e. housing disks; the shaft disks were used in the micro-pin-on-disk tests) was conducted. The ToF-SIMS measurements were conducted at the University of Münster. 40 Tribologie + Schmierungstechnik 64. Jahrgang 5/ 2017 Table 1: Test conditions and results for axial bearing washers Axial bearing Temperature Axial load Test length Average frictional washer [°C] [kN] [h] torque [Nm] TB 60-80 80 60 200 10 TB 60-100 100 60 50 8.5 TB 60-120 120 60 200 6 Rolling contact area High slip zone outside No slip zone High slip zone inside 1 mm Figure 1: Photograph of the surface for a bearing washer with boundary layers on the rolling contact area (tested at 80 °C) Figure 2: Structure of boundary layers on bearing washer tested at 100 °C, scanning probe image at the high slip zone outside T+S_5_17 31.07.17 10: 58 Seite 40 Aus der Praxis für die Praxis Experimental methods Nanoindentational test setup To measure the nanomechanical properties on the axial bearing washer surfaces nanoindentational tests were used. The tests were carried out applying a Hysitron TriboIndenter ® . For measurement of the hardness properties a triangular diamond Berkovich tip was used. As maximum load for the load-indentation curves 1 mN was applied to the tip. The Young’s Modulus and the correlated hardness were calculated with the unloading curve of the indentation tests applying the method of Oliver and Pharr [6]. To investigate the frictional properties during ploughing, single nanoscratch tests were performed. For the scratch tests a cono-spherical diamond tip with an opening angle of 90° and a tip radius of 280 nm was used. For the scratch test the tip is moved along the substrate and scratches into the surface with continuously increasing load over the scratch length, reaching the maximal force at the end of the test. To measure the frictional properties inside the boundary layers the final force was 1 mN. The scratch length was 9 microns. The properties of boundary layers on bearing surfaces were measured previously by nanoscratch tests [7-9]. In contrast to the earlier measurements the applied load was reduced to perform the scratch in the boundary layers. Micro pin-on-disk tester The measurements of the sliding friction were carried out with a micro pin-on-disk tester. This tester is based on a modified Center for Tribology (CETR) Olympus HDI reliability spin-stand (Figure 3). Originally the test stand was developed to investigate the head-to-disk interface of a hard disk drive. On the tester, axial bearing washers can be mounted as disk. A sapphire half ball as test specimen was attached with adhesive to the slider of a HDD recording head. The diameter of the sapphire half ball is 500 microns. After mounting the slider on the testers arm, the desired normal force is applied. As load 30 mN were used. The axial bearing washers serve as counterparts. For the measurements, the bearing washer rotated at 1 rpm. During the test, the coefficient of friction was recorded. Different circumferential positions can be investigated by moving the tip to different radii of the bearing washer. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) The chemical compositions of loaded and unloaded areas on the washer surfaces were determined at the Physikalisches Institut, Westfälische Wilhelms-Universität Münster, using a ToF-SIMS instrument comparable to the ToF-SIMS IV of IONTOF GmbH. It is equipped with a bismuth liquid metal ion gun for high-resolution imaging and a noble-gas electron-impact ion gun for sputter erosion in dual beam depth-profile analysis. Time-of-Flight Secondary Ion Mass Spectrometry (ToF- SIMS) is a surface analytical method for determining the atomic and molecular composition of surfaces of solid state materials. Using this method, the surface of a solid state target is bombarded with energetic primary ions causing the sputtering of the outermost monolayers of the target. Amongst the emitted particles positively or negatively charged atoms or molecules, the so called secondary ions, can directly be analysed according to their mass-to-charge ratio determined via mass spectrometer [10-12]. The special merits of ToF-SIMS are a high detection probability combined with a high surface sensitivity. The main focus of applications are in trace element analysis, the determination of lateral distributions of atoms and molecules on the surface and the analysis of the composition of boundary layers using depth profiling. Due to this, ToF-SIMS is ideally suited for the analysis of tribologically build up boundary layers, including the adsorptive layer formed from oil additive components, and to advance the understanding of the interaction of all materials involved [1, 13-17]. In preparation for ToF-SIMS-analysis, the bearing washers were cut into four pieces. Prior to the analysis, the segments were cleaned in an ultrasonic bath (3 x 5 min) using n-hexane (SupraSolv) to remove the adhering oil film and expose the adsorbate layer. On each washer, the lateral distribution of atoms and molecules on the surface was determined by applying the large area mapping mode of operation on an area of 14.7 mm x 1.8 mm covering the whole rolling contact area, including adjacent areas outside the raceway. In order to avoid exceeding the static limit, two large area maps (positively as well as negatively charged ions) were recorded at different positions. In addition, two sets of eleven depth profiles each analysing positively and negatively charged secondary ions were carried out. In each case, two profiles were recorded outside the Tribologie + Schmierungstechnik 64. Jahrgang 5/ 2017 41 Figure 3: Setup of the micro pin-on-disk tester T+S_5_17 31.07.17 10: 58 Seite 41 Aus der Praxis für die Praxis raceway (one on the outer and one on the inner side of the washer) and nine profiles relatively evenly distributed inside the raceway. Experimental results The hardness on the bearing washers was measured along the surface. For the examination the values on both slip zones and the no slip zone were regarded. The average hardness on the outer high slip zone (measured 4 mm and 5 mm from the outer rim), the inner high slip zone (measured 10 mm and 11 mm from the outer rim), and the no slip zone (measured 8 mm from the outer rim) is shown in Figure 4. The first and third bearing washers (passing the test) feature the lowest hardness values on Pin-on-Disk test results The frictional properties while sliding are measured with the micro pin-on-disk tester. As the pin does not penetrate the boundary layers, the CoFs obtained are much lower compared to the nanoscratch tests. For the bearing washers, the CoF of the outer high slip zone and the no slip zone are shown in Figure 6. The failed bearing washer TB 60-100 shows the highest CoF on the outer high slip zone. In case of the bearing TB 60-80 the difference is much lower. For the bearing TB 60-120 the CoF on the no slip zone is significantly higher. ToF-SIMS large area mapping Figure 7 shows the distribution of selected negative (top) and positive (bottom) secondary ions obtained from large area mapping of the washer surface of test bearing TB 60-80 (left), TB 60-100 (middle) and TB 60-120 (right). The position of the raceway is marked in darkgrey; however the relative position depends on the backlash of the rolling elements in the cage which is about ± 250 µm. The light-grey background marks the whole 42 Tribologie + Schmierungstechnik 64. Jahrgang 5/ 2017 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 TB 60-80 TB 60-100 TB 60-120 Average hardness [GPa] high slip zone outside no slip zone high slip zone inside Figure 5: CoF obtained at the end of scratch test; a) for TB 60 100, CoF (average out of three scratch tests), b) Comparison CoF obtained in nanoscratch test Figure 4: Average hardness on the raceways for the tested bearing washers 0.2 0.22 0.24 0.26 0.28 0.3 0 5,000 10,000 15,000 Coefficient of friction Position on bearing washer [µm] 0.20 0.22 0.24 0.26 0.28 0.30 TB 60-80 TB 60-100 TB 60-120 Coefficient of friction high slip zone outside no slip zone high slip zone inside the no slip zone. The second bearing washer TB 60-100 (failing the test) shows the highest hardness on the no slip zone. On the high slip zone inside this bearing washer feature the lowest hardness. Nanoscratch test results In the nanoscratch tests, the coefficient of friction (CoF) is investigated at the end of the scratch test. At each measurement position three nanoscratch tests were performed. The average values for the bearing washer TB 60-100 are shown in Figure 5a. The CoF on the outer high slip zone features the highest value. The lowest values can be found on the inner high slip zone. The values obtained in the nanoscratch test for the high slip zone outside, the high slip zone inside, as well as the no slip zone are depicted in Figure 5b. The failed bearing washer TB 60-100 features high friction on the outer high slip zone, while relative low friction on the no slip zone. In case of the bearings passing the test the high slip zone outside shows lower frictional values as on the no slip zone. a) b) T+S_5_17 31.07.17 10: 58 Seite 42 Aus der Praxis für die Praxis area of 15.8 mm of the polished washer surface. The outer rim of the washer is indicated by the position 0 mm. Each single image is normalized to itself and bright areas depict high secondary ion intensities. As can be seen for TB 60-80 (left) and TB 60-100 (middle), several secondary ion signals show inhomogeneous distributions with clearly separated areas inside the raceway. With TB 60-120 (right), all negative secondary ions show a much more uniform distribution inside the rolling contact area apart from areas near to both edges of the rolling contact area. Note, that large area maps of negative and positive secondary ions were obtained from different sites separated by a distance of about 2 mm. In the case of TB 60-120 the positive secondary ions were registered at a place where a surface contamination, possibly zinc containing, seems to cover parts of the raceway. The occurrence of PO 2− , Ca 2 PO 3− , Ca 2 PO 3+ and other molecules containing compounds of type P x O y (x ≥ 2, y ≥ 3; not shown) often indicate the formation of a phosphate glass layer [18, 19]. With TB 60-80 and TB 60-100, those signals are mainly located within the raceway. With TB 60-120, those signals also show relatively high intensities outside the raceway, mainly in the inside region of the washer. This might be an indication of a pure thermally caused formation of a phosphate glass layer from ZDDP according to Fujita [20]. He showed that with oil temperatures exceeding 80 °C, layer formation is not negligible and increases with increasing temperature and immersion time. Another peculiarity can be seen comparing the secondary ion signal intensities obtained from different areas of the raceway. With all washers but especially those from TB 60-80 and 60-100 differences in the secondary ion emission between high slip zones outside and inside the raceway are visible. This might indicate different conditions for molecule adsorption and film formation at the outer side of the raceway compared to those on the inner side. A reason might be found in different surface temperatures, probably induced by different kinds of slip, which can lead either to different chemical reactivity or to deterioration of adsorbed molecules. In addition, with TB 60-80 and TB 60-100 some sulphur-containing signals, like CHS + or S − , show opposite behaviour with respect to calcium-containing signals like Ca + or Ca 2 PO 3− . For example, reduced signal inten- Tribologie + Schmierungstechnik 64. Jahrgang 5/ 2017 43 0.080 0.085 0.090 0.095 0.100 0.105 0.110 TB 60-80 TB 60-100 TB 60-120 Coefficient of friction high slip zone outside no slip zone Figure 6: Frictional results obtained in micro pin-on-disk tester Figure 7: Distribution of selected negative (top) and positive (bottom) secondary ions obtained from large area mapping of the washer surface of test bearing TB 60-80 (left), TB 60-100 (middle) and TB 60-120 (right). Each single image is normalized to itself and bright regions depict high secondary ion intensities. T+S_5_17 31.07.17 10: 58 Seite 43 Aus der Praxis für die Praxis sities of Ca + correspond to enhanced signal intensities of S − and increased Ca + -signal intensities correlate with reduced S − -intensities. In contrast, C 9 H 9 SO 3− , a signal often detected in ToF-SIMS analysis of calciumsulphonate-containing oils, shows a distribution similar to calciumand phosphorus-containing secondary ions. Mass spectrometric depth profiling On selected spots on the washer surface, ToF-SIMS depth profile analyses were carried out. In order to reduce matrix induced changes of secondary ion yields and sputtering yields during ion bombardment induced removal of tribological loaded boundary layers and bearing base material, all depth profiles were performed using simultaneous oxygen-flooding applying pure 18 O-gas with a base pressure of 1 x 10 −6 mbar. So, secondary ion signals containing the isotope 16 O can be clearly attributed to oxygen incorporation into the boundary layer during the tribological applied load. Since no reliable information about the actual sputtering yield inside the tribologically formed boundary layer is available, the secondary ion signals are presented as a function of the sputter ion dose densities (SPIDDs) applied for the removal of the boundary layers. The thickness of the depth profiled boundary layers was estimated from the curves of the decaying PO − -signal and the increasing Fe 18 O 2− -signal intersect. Figure 8 shows the intensities of selected negative secondary ions as a function of applied SPIDDs, obtained from depth profiles performed on spots on the outside high slip zone of the raceway in a distance of 5 mm from the outer rim of the washer surface of test bearings TB 60-80 (left), TB 60-100 (middle) and TB 60-120 (right). The Fe 18 O 2− -signal represents steel substrate and indicates the transition from the tribological boundary layer to the base material. Calcium-, sulphur-, boronand phosphorus-containing signals represent remains of additives. Compared to areas outside the raceway (not shown here), where only a SPIDD of 0.06 ∙ 10 17 ions/ cm 2 44 Tribologie + Schmierungstechnik 64. Jahrgang 5/ 2017 0,0 0,2 0,4 0,6 0,8 1,0 0.0 0.5 1.0 1.5 2.0 2.5 3,0 normierte Signalintensität TBB 3814, Low-Ref, Ar + , posi ve Polarität, Stelle 1 S BO PO Fe¹ O Ca PO 0,0 0,2 0,4 0,6 0,8 1,0 0.0 0.5 1.0 1.5 2.0 2.5 3,0 normierte Signalintensität TBB 3814, Low-Ref, Ar + , posi ve Polarität, Stelle 1 S BO PO Fe¹ O Ca PO 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.5 1.0 1.5 2.0 2.5 3,0 normierte Signalintensität TBB 3814, Low-Ref, Ar + , posi ve Polarität, Stelle 1 S BO PO Fe¹ O Ca PO normalized signal intensity SPIDD in 10 17 ions/ cm 2 SPIDD in 10 17 ions/ cm 2 SPIDD in 10 17 ions/ cm 2 Fe¹ O Ca PO PO BO S Fe¹ O Fe¹ O S Ca PO Ca PO PO BO PO BO S TB 60-80 TB 60-100 TB 60-120 Figure 8: Intensities of selected negative secondary ions as a function of applied SPIDDs, obtained from depth profiles performed on areas with a distance of 5 mm from the outer rim of the washer surface of test bearings TB 60-80 (left), TB 60-100 (middle) and TB 60-120 (right) 0.0 0.5 1.0 1.5 TB 60-80 TB 60-100 TB 60-120 SPIDD in 10 17 ions/ cm 2 at PO - -/ Fe 18 O 2- -crossing point bearing high slip zone outside no slip zone high slip zone inside was needed to remove the thin boundary layer, higher SPIDDs were needed to reach the crossing point of the PO − and Fe 18 O 2− -signal curves in areas within the rolling contact area. This indicates the alteration of the washer surface and the formation of a reaction layer. With TB 60-100, showing an early failure during the FE-8 test, some differences can be seen in the signal courses obtained from the outside high slip zone when compared to the other bearings. In these areas, the profiles of S − show the highest intensities directly on the surface and not within the boundary layer. In addition, the profiles of BO 2− and Ca 2 PO 3− show a steeper decrease compared to the other bearings. Comparing SPIDD-values needed to reach the PO − -/ Fe 18 O 2− -crossing point (Figure 9) in the Figure 9: SPIDDs needed to reach the PO − - / Fe 18 O 2− crossing point at the outside high slip zone (blue bar), the no slip zone (green bar) and the inside slip zone (grey bar) of the test bearings TB 60-80, TB 60-100 and TB 60-120 T+S_5_17 31.07.17 10: 58 Seite 44 Aus der Praxis für die Praxis outside high slip zone to the inside high slip zone one can see, that with all bearings lower SPIDD-values were determined at the inside high slip zone. One reason for this could possibly be different amounts of the specific friction energy accumulated at the outer or inner edge of the raceway of this cylindrical roller bearing as proposed in [18]. Conclusion In FE-8 tests was shown, that at a specific temperature bearings tend to failure. By reducing or increasing the temperature of the test the bearings pass. By a change of the temperature the boundary layers feature different chemical and frictional properties. With ToF-SIMS large area mappings, inside the contact area of all bearing washers the formation of phosphate glass stimulated by load and temperature could be detected. Looking at areas outside the raceway of the bearing tested at 120 °C, secondary ion signals suggest that the formation of purely thermally build phosphate glass takes place as well, especially at the inner side of the washer. In addition, some secondary ions, when detected from high slip zones at the outer or inner side of the raceway, show differences in their intensities also indicating different surface temperatures across the washer during layer build-up, probably induced by different kinds of slip. The influence of different temperatures and added type of load on the formation of phosphate glass like boundary layers can be seen as well with ToF-SIMS depth profiles, carried out at selected spots across the raceway of all bearings. Those profiles show that with all bearings in the inside high slip zone lower SPIDD-values are needed to reach the PO − -/ Fe 18 O 2− -crossing point compared to the outside high slip zone. This could possibly be attributed to different amounts of the specific friction energy accumulated at the outer or inner edge of the raceway of this cylindrical roller bearing. In case of the failed bearings in contrast to the other bearings the hardness on the no slip zone is significantly increased. To have a closer look on the nanomechanical properties the frictional properties while ploughing and sliding were analysed. The high slip zone of a failed bearing washer (TB 60-100) shows an increased coefficient of friction on the outer high slip zone in the nanoscratch test and the pin-on-disk test. As in this region higher slip occurs, the increased frictional properties result in increased resistance against slip and can have a negative influence and damage of the boundary layers. A damage of a boundary layer can result in an easier diffusion of hydrogen to the metallic surface and the formation of cracks under the bearings surface. In case of the bearing tested under increased temperature an increased friction on the surface can be detected for the no slip zone. In this case pure rolling dominates, thus the frictional properties of the tribolayers have a lower influence. In this zone the hardness and Young’s Modulus (which is correlated to the hardness) have a higher influence on the surface pressure. Thus, the higher Young’s Modulus in the no slip zone for the failed bearing results in higher stress in the tribological contact and can also influence the failure for the bearings tested under 100 °C. Acknowledgment This work was sponsored in part by the DFG (German Research Foundation) within the research program ”Influence of stress states in rolling bearings on White Etching Cracks”. References 1. D. Lipinsky, C. Brüning, C. Mayer, H. F. Arlinghaus, T. Skubacz, G. Poll: Oberflächenanalyse der aus Additiven gebildeten tribologischen Schichten mit der Flugzeit- Sekundärionenmassenspektrometrie, Tribologie und Schmierungstechnik, 58 (2), pp. 29-35, 2011 2. S. Bec, A. Tonck, J. M. Georges,R. C. Coy, J. C. Bell J, and G. W. Roper: Structure and properties of zinc dithiophosphate anti-wear films, Proc. R. Soc., A 455, 4181- 203, 1999 3. M. Kohara, T. Kawamura, and M. Egami: Study on Mechanism of Hydrogen Generation from Lubricants, Tribology Transactions, 49, 1, pp. 53-60, 2006 4. B. Han, J. Binns, and I. Nedelcu: In Situ Detection of Hydrogen Uptake from Lubricated Rubbing Contacts, Tribology Online, 11, 2, pp. 450-45, 2016 5. G. C. Smith: Surface analytical science and automotive lubrication, J. Phys. D: Appl. Phys., 33, R187-R197, 2000 6. W. C. Oliver, G. M. Pharr: An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments, Journal of Materials Research, Vol. 7, Issue 6, pp. 1564 - 1583, 1992 7. S.B. Wiendl, W.-R. Zabel, H.H. Gatzen, G. Poll: The Influence of Boundary Layer Properties on Grease Lubricated High-Speed Ball Bearing Performance, Transient Processes in Tribology, Tribology Series, 43, Elsevier, Amsterdam, Netherlands, pp. 441-447, 2004 8. M. Gatzen, F. Pape, G. Poll: Physical properties of boundary layers in angular contact ball bearings lubricated with greases containing polymers, Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 22, 3, pp. 581-592, 2009 9. F. Pape.: Mikrotribologische Untersuchungen an Wälzlagern mit polymeradditiver Fettschmierung, Thesis, Leibniz Universität Hannover, 2011 10. A. Benninghoven, FG. Rüdenauer, HW. Werner: Secondary ion mass spectrometry: Basic concepts, Instrumental aspects, Applications and Trends. New York: Wiley, Chemical analysis, Vol. 86, 1987 11. J. C. Vickerman, D. Briggs D (eds): TOF-SIMS: Surface Analysis by Mass Spectrometry, IM Publications, Vol. 2, 2013 12. H. F. Arlinghaus: Static Secondary Ion Mass Spectrometry. In: Bubert H and Jenett H (eds) Surface and Thin Film Analysis, 2 nd ed. Wiley-VCH, 2011 Tribologie + Schmierungstechnik 64. Jahrgang 5/ 2017 45 T+S_5_17 31.07.17 10: 58 Seite 45 Aus der Praxis für die Praxis 13. C. Minfray, J. M. Martin, M. I. De Barros et al.: Chemistry of ZDDP tribofilm by ToF-SIMS, Tribol Lett 2004; 17(3): 351-357 14. T. Kubo, S. Fujiwara, H. Nanao et al.: TOF-SIMS analysis of boundary films derived from calcium sulfonate, Tribol Lett, 23(2), pp. 171-178, 2006 15. A. Murase, H. Mori, T. Ohmori: TOF-SIMS analysis of friction surfaces of hard coatings tested in engine oil, Appl. Surf. Sci., 255(4), pp. 1494-1497, 2008 16. C. Mayer, D. Lipinsky, F. Wohlleber et al.: Coordinated test rig and ToF-SIMS experiments to investigate the influence of phosphate glass layers on the friction behavior of a wet clutch, Surf. Interface Anal., 46 (S1), pp. 401- 404, 2014 17. D. Lipinsky, E. Wittek, C. Muhmann et al.: Oberflächenanalyse der im Betrieb mit Fuel Economy Ölen gebildeten Grenzschichten mit der Flugzeit-Sekundärionenmassenspektrometrie (ToF-SIMS), Proceedings, Tribologie Fachtagung „Reibung, Schmierung und Verschleiß“, Göttingen, Germany, 22 Sept - 24 Sept 2014, paper no. 55 (Vol II), 2014 18. M. Crobu, A. Rossi., F. Mangolini, N. D. Spencer.: Chainlength-identification strategy in zinc poly-phosphate glasses by means of XPS and ToF-SIMS, Analytical and Bioanalytical Chemistry, Volume 403, Issue 5, pp. 1415-1432, 2012 19. M. Crobu, A. Rossi, N. D. Spencer.: ToF-SIMS of polyphosphate glasses, Surface and Interface Analysis, Vol. 45, Issue 1, pp. 579-582, 2013 20. H. Fujita., H. A. Spikes.: The formation of zinc dithiophosphate antiwear films, Proceedings of the Institution of Mechanical Engineers. Part J, Journal of Engineering Tribology, 218, pp. 1-13, 2004 21. J. Loos: Einfluss der Reibbeanspruchung auf die WEC- Bildung in Wälzlagern. Proceedings, Tribologie Fachtagung „Reibung, Schmierung und Verschleiß“, Göttingen, Germany, 22 Sept - 24 Sept 2014, paper no. 23 (Vol I), 2014 46 Tribologie + Schmierungstechnik 64. Jahrgang 5/ 2017 Dipl.-Ing. Alfred P. Thilow und 6 Mitautoren .jpg Entgrattechnik Entwicklungsstand und Problemlösungen 5., neu bearb. u. erw. Aufl. 2017, 243 S., 201 Abb., 11 Tab., 59,00 €, 75,50 CHF (Kontakt & Studium, 392) ISBN 978-3-8169-3352-6 Zum Buch: Die in großen Teilen überarbeitete und aktualisierte 5. Auflage dieses Themenbandes beschreibt die Entgratverfahren, die sich in der Praxis etabliert und bewährt haben und vermittelt Informationen zu ihren Einsatzgebieten und Verfahrensgrenzen. Eine Matrix mit Verfahrensmerkmalen erleichtert dem Planer die Vorentscheidung für das am besten geeignete Verfahren. Erweitert wurden die Grundlagen der Gratentstehung beim Bohren, Drehen und Gleichlauf- Gegenlauffräsen. Ein wichtiges Thema ist die Gratminimierung. Sie beeinflusst und erweitert die Auswahl der anwendbaren Entgratverfahren und damit auch die Fertigungskosten. Mit einem neuen einfachen und damit praktikablen Denk- und Lösungsansatz zur Gratminimierung wird dem Rechnung getragen. Das Kapitel "Entgraten mit Industrierobotern" wurde auf den neuesten Stand gebracht und enthält interessante Problemlösungen. Die Interessenten: Das Buch richtet sich an Fertigungsplaner, Fertigungsmeister, Betriebsleiter und Betriebsingenieure, Planer, Arbeitsvorbereiter, Qualitätskontrolleure und Konstrukteure Blätterbare Leseprobe und einfache Bestellung unter: www.expertverlag.de/ 3352 Bestellhotline: Tel: 07159 / 92 65-0 • Fax: -20 E-Mail: expert@expertverlag.de Anzeige T+S_5_17 31.07.17 10: 58 Seite 46 Aus der Praxis für die Praxis Einleitung Innovative Antriebskonzepte im Bereich des Automobilbaus gewinnen aufgrund politischer Rahmenbedingungen und gesellschaftlicher Entwicklungen zunehmend an Bedeutung. Neben durchaus vielversprechenden Ansätzen aus dem Umfeld der Elektromobilität werden aber auch gerade die klassischen Antriebskonzepte - bestehend aus Verbrennungsmotor, Kupplung und Getriebe, gegebenenfalls in Kombination mit Elektroantrieben (Hybridkonzepte) - in den nächsten Jahrzehnten noch weiterhin eine entscheidende Rolle in sämtlichen Mobilitätskonzepten spielen. Obwohl Verbrennungsmotor und Antriebsstrang schon lange Zeit erforscht und weiterentwickelt worden sind, Tribologie + Schmierungstechnik 64. Jahrgang 5/ 2017 47 * Prof. Dr.-Ing. Sandro Wartzack, Dr.-Ing. Stephan Tremmel Dipl.-Ing. (FH) David Hochrein (SFI): Friedrich-Alexander Universität Erlangen-Nürnberg Lehrstuhl für Konstruktionstechnik, 91058 Erlangen Dipl.-Ing. (FH) Oliver Graf-Goller: Schaeffler Technologies AG & Co.KG, 91074 Herzogenaurach Vorstellung einer neuen Prüfstandsgruppe zur Untersuchung des Fliehkrafteinflusses auf das Reibungsmoment von Wälzlagern D. Hochrein, O. Graf-Goller, S. Tremmel, S. Wartzack* Anwendungen in denen Wälzlager Fliehkraftbelastung erfahren sind beispielsweise Planetenradlagerungen oder Pleuellagerungen im Verbrennungsmotor. Im Bereich der Getriebetechnik sind die Anforderungen an Planetenradlagerungen vor allem in den letzten Jahren aufgrund von Wirkungsgradoptimierungen stark angestiegen und die zu ertragenden Beschleunigungen werden in wenigen Jahren Werte bis zum 8 000-fachen der Erdbeschleunigung erreichen. Dies entspricht in etwa einer Verdoppelung der aktuellen Belastung. Im Gegensatz hierzu sind die Anforderungen für Pleuellagerungen schon seit Beginn der Entwicklung von Verbrennungsmotoren sehr komplex. Im Bereich der Kraftfahrzeugmotoren haben sich daher in den vergangenen Jahrzenten überwiegend Gleitlager etabliert, obwohl zu Beginn der Motorenentwicklung diese Anwendung eine Domäne der Wälzlager war. In beiden Anwendungen sind fliehkraftbelastete Wälzlager ein wesentlicher Beitragsleister für das Gesamtreibungsmoment des Aggregats und weisen somit ein vielversprechendes Energieeinsparpotential auf. Aufgrund der extremen und komplizierten Belastungen sind die Vorgänge in solchen Lagern bisher allerdings nur wenig erforscht. Aus diesem Grund ist eine Prüfstandsgruppe entwickelt und gebaut worden, die eine intensive experimentelle Untersuchung dieser Thematik erlaubt. Schlüsselwörter Wälzlager, Reibung, Fliehkraftfeld Applications for rolling element bearings, which are exposed to centrifugal load, are, for example, planetary wheel supports of planetary gears or connecting rod bearings of internal combustion engines. In the field of planetary wheel supports the requirements especially in recent years have increased sharply due to efficiency improvements in the field of transmission technology. The accelerations, the bearings are exposed to, will reach values of up to 8 000 times gravity in a few years. This represents a doubling of the current load. In contrast the requirements for connecting rod bearings are very complex since the beginning of the development of combustion engines. Thus in the field of automotive engines plain bearings have in recent decades been established, although this application has been the domain of rolling element bearings at the beginning of engines development. In both applications, rolling element bearings exposed to centrifugal load provide a major contribution to the total frictional moment of the assembly unit and show therefore a promising energy saving potential. Due to the extreme and complex loads the procedures in such bearings have so far been little researched. For this reason, a group of test rigs has been designed and installed, which allows a detailed experimental study of this issue. Keywords Rolling element bearings, friction, centrifugal load Kurzfassung Abstract T+S_5_17 31.07.17 10: 58 Seite 47