The lifetime of electrical contacts is influenced by various factors. Micromotions due to fluctuations in temperature and vibration in the field lead to fretting wear and fretting corrosion of electrical contacts. In case of the contacts with noble coatings, the fretting wear results in the wear through of the coating causing the exposure of the underlying non-noble metal to the surrounding atmosphere which in turn leads to fretting corrosion. These degradation mechanisms lead to an increase in electrical contact resistance and eventual failure of the system. In this study, the extent of contact degradation due to fretting war of galvanically silver-plated electrical contacts is investigated. To compare the extent of war occurring at different stages of the contacts’ lifetime, the fretting tests are conducted up to predefined fretting cycles. XRF measurements of the coating thickness before after the tests are performed and the wear depth after the given fretting cycles is determined via confocal microscopy. The results of two different types of silver plating are compared. Based on this, a prognosis regarding the wear behavior and expected lifetime of different coating systems can be made possible.
{"title":"Einfluss der Mikrohärte der Ober- flächenschutzschicht auf den Verschleiß und die Lebensdauer von elektrischen Kontakten bei Reibverschleißbelastung","authors":"Roman Probst, J. Song","doi":"10.24053/tus-2023-0005","DOIUrl":"https://doi.org/10.24053/tus-2023-0005","url":null,"abstract":"The lifetime of electrical contacts is influenced by various factors. Micromotions due to fluctuations in temperature and vibration in the field lead to fretting wear and fretting corrosion of electrical contacts. In case of the contacts with noble coatings, the fretting wear results in the wear through of the coating causing the exposure of the underlying non-noble metal to the surrounding atmosphere which in turn leads to fretting corrosion. These degradation mechanisms lead to an increase in electrical contact resistance and eventual failure of the system. In this study, the extent of contact degradation due to fretting war of galvanically silver-plated electrical contacts is investigated. To compare the extent of war occurring at different stages of the contacts’ lifetime, the fretting tests are conducted up to predefined fretting cycles. XRF measurements of the coating thickness before after the tests are performed and the wear depth after the given fretting cycles is determined via confocal microscopy. The results of two different types of silver plating are compared. Based on this, a prognosis regarding the wear behavior and expected lifetime of different coating systems can be made possible.","PeriodicalId":53690,"journal":{"name":"Tribologie und Schmierungstechnik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47719225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As copper is a rather difficult material to machine due to its ductility compared to aluminium, this study presents the approach of oxidizing the surface to improve the results of the grinding process. Therefore, batch manufactured flexible micro-grinding tools are used for grinding of copper and oxidized copper surfaces to machine microstructure or local areas of functional surfaces. Besides, we show a comparison of the performance of an abrasive layer made of silicon carbide (SiC) and cubic boron nitride (cBN). The tools are made of a polyimide-based abrasive layer and silicon as substrate and are fabricated by photolithography and deep reactive ion etching. The oxidation of copper surfaces is done by electrochemical processes and are directly machined with grinding tools. The surface quality is evaluated concerning the surface roughness by optical measurements with confocal microscopy. Lower roughness values are achieved on both, the pure copper and the oxidized copper by using SiC grinding tools. On pure copper this is reflected in a reduction of the arithmetical mean roughness value Ra to 0.04 µm. The unprocessed reference surface shows an Ra of 0.24 µm. In addition, the machined oxidized surfaces show a reduction of the mean roughness depth Rz from 7,60 µm to 1.10 µm, which is an optimization of factor 2 compared to the machined non-oxidized copper surfaces (2.32 µm). The machining of copper with cBN micro-grinding tools also shows improved roughness values, but in comparison to the SiC tools these are 50 % higher for machined copper surfaces and similar for machined oxidized copper surfaces. While the oxidation of the copper surface has a positive effect on the surface quality, no effect on tool wear can be observed.
{"title":"Application of batch manufactured flexible micro-grinding tools on copper and oxidized copper surfaces","authors":"Lukas Steinhoff, F. Dencker, M. Wurz","doi":"10.24053/tus-2023-0002","DOIUrl":"https://doi.org/10.24053/tus-2023-0002","url":null,"abstract":"As copper is a rather difficult material to machine due to its ductility compared to aluminium, this study presents the approach of oxidizing the surface to improve the results of the grinding process. Therefore, batch manufactured flexible micro-grinding tools are used for grinding of copper and oxidized copper surfaces to machine microstructure or local areas of functional surfaces. Besides, we show a comparison of the performance of an abrasive layer made of silicon carbide (SiC) and cubic boron nitride (cBN). The tools are made of a polyimide-based abrasive layer and silicon as substrate and are fabricated by photolithography and deep reactive ion etching. The oxidation of copper surfaces is done by electrochemical processes and are directly machined with grinding tools. The surface quality is evaluated concerning the surface roughness by optical measurements with confocal microscopy. Lower roughness values are achieved on both, the pure copper and the oxidized copper by using SiC grinding tools. On pure copper this is reflected in a reduction of the arithmetical mean roughness value Ra to 0.04 µm. The unprocessed reference surface shows an Ra of 0.24 µm. In addition, the machined oxidized surfaces show a reduction of the mean roughness depth Rz from 7,60 µm to 1.10 µm, which is an optimization of factor 2 compared to the machined non-oxidized copper surfaces (2.32 µm). The machining of copper with cBN micro-grinding tools also shows improved roughness values, but in comparison to the SiC tools these are 50 % higher for machined copper surfaces and similar for machined oxidized copper surfaces. While the oxidation of the copper surface has a positive effect on the surface quality, no effect on tool wear can be observed.","PeriodicalId":53690,"journal":{"name":"Tribologie und Schmierungstechnik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42265145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Numerische Modellierung von Elektro vibration in der Oberflächenhaptik","authors":"Fabian Forsbach, Philip Köch, M. Hess","doi":"10.24053/tus-2023-0003","DOIUrl":"https://doi.org/10.24053/tus-2023-0003","url":null,"abstract":"","PeriodicalId":53690,"journal":{"name":"Tribologie und Schmierungstechnik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48998866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Benjamin Bergmann, B. Denkena, G. Poll, F. Pape, Haichao Liu, L. Ellersiek
The friction at the cutting wedge has a significant influence on tool wear. Due to the strong local variance of temperatures and stresses at the cutting wedge, the friction conditions differ significantly locally. In this work, a method is presented with which normal stress es, tangential stresses and local friction coefficients at the cutting wedge can be determined based on experimental investigations. For this purpose, high-speed recordings and force measurements are conducted on a planing test rig. In addition to dry cutting processes, investigations are carried out on the test rig using emulsion and oil as metal working fluid. The results show a reduction of the coefficients of friction when oil is used as metal working fluid. However, when emulsion is used as metal working fluid, the coefficient of friction changes only slightly compared to dry machining. This can be attributed to low film-forming ability of the emulsion.
{"title":"Reibkoeffizientenermittlung in der Zerspanung auf Basis von Hochgeschwindigkeitsaufnahmen","authors":"Benjamin Bergmann, B. Denkena, G. Poll, F. Pape, Haichao Liu, L. Ellersiek","doi":"10.24053/tus-2022-0041","DOIUrl":"https://doi.org/10.24053/tus-2022-0041","url":null,"abstract":"The friction at the cutting wedge has a significant influence on tool wear. Due to the strong local variance of temperatures and stresses at the cutting wedge, the friction conditions differ significantly locally. In this work, a method is presented with which normal stress es, tangential stresses and local friction coefficients at the cutting wedge can be determined based on experimental investigations. For this purpose, high-speed recordings and force measurements are conducted on a planing test rig. In addition to dry cutting processes, investigations are carried out on the test rig using emulsion and oil as metal working fluid. The results show a reduction of the coefficients of friction when oil is used as metal working fluid. However, when emulsion is used as metal working fluid, the coefficient of friction changes only slightly compared to dry machining. This can be attributed to low film-forming ability of the emulsion.","PeriodicalId":53690,"journal":{"name":"Tribologie und Schmierungstechnik","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41913540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this work, the friction behavior of chain joints with triboactively coated pins was analyzed. For this purpose, the nitride hard coating (Cr,Al)N+Mo, produced by means of a PVD process, was investigated. A sulfur-added model grease was used for lubrication. This is to produce tribochemical transfer coatings that are transferred from the chain pin to the sleeve under tribological loading. As a reference, measurements were also carried out on a (Cr,Al)N coating system and on uncoated samples. Various normal forces, sliding speeds and temperatures were also considered as further influencing variables. The frictional torques were determined using the chain joint tribometer deve loped at the Chair of Machine Elements, Gears and Tribology (MEGT).
{"title":"Einfluss von Beschichtungen zur triboaktiven Transferschichtbildung auf die Reibung in Kettengelenken","authors":"M. Rank, D. Meffert, M. Oehler, Oliver Koch","doi":"10.24053/tus-2022-0039","DOIUrl":"https://doi.org/10.24053/tus-2022-0039","url":null,"abstract":"In this work, the friction behavior of chain joints with triboactively coated pins was analyzed. For this purpose, the nitride hard coating (Cr,Al)N+Mo, produced by means of a PVD process, was investigated. A sulfur-added model grease was used for lubrication. This is to produce tribochemical transfer coatings that are transferred from the chain pin to the sleeve under tribological loading. As a reference, measurements were also carried out on a (Cr,Al)N coating system and on uncoated samples. Various normal forces, sliding speeds and temperatures were also considered as further influencing variables. The frictional torques were determined using the chain joint tribometer deve loped at the Chair of Machine Elements, Gears and Tribology (MEGT).","PeriodicalId":53690,"journal":{"name":"Tribologie und Schmierungstechnik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49214296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Christian Orgeldinger, Armin Seynstahl, Tobias Rosnitschek, S. Tremmel
Additive manufacturing processes have become increasingly important in recent years. However, the use of additive manufactured components in tribological applications – especially for metallic components – has still been little investigated. This work analyzes the extent to which components printed with the Atomic Diffusion Additive Manufacturing (ADAM) process are suitable for use in tribomechanical systems. The focus is on the tribological behavior of the tool steel D2 against 100Cr6 counterparts under lubrication with deep drawing oil, taking direction-dependent manufacturing effects into account. The first tribological investigations with the ADAM process show great optimization potential for possible applications in the field of forming technology. The surface treatment of the samples has proven to be mandatory in the investigations.
{"title":"Einfluss fertigungsbedingter Effekte auf das tribologische Verhalten im ADAM-Verfahren gedruckter Bauteile","authors":"Christian Orgeldinger, Armin Seynstahl, Tobias Rosnitschek, S. Tremmel","doi":"10.24053/tus-2022-0042","DOIUrl":"https://doi.org/10.24053/tus-2022-0042","url":null,"abstract":"Additive manufacturing processes have become increasingly important in recent years. However, the use of additive manufactured components in tribological applications – especially for metallic components – has still been little investigated. This work analyzes the extent to which components printed with the Atomic Diffusion Additive Manufacturing (ADAM) process are suitable for use in tribomechanical systems. The focus is on the tribological behavior of the tool steel D2 against 100Cr6 counterparts under lubrication with deep drawing oil, taking direction-dependent manufacturing effects into account. The first tribological investigations with the ADAM process show great optimization potential for possible applications in the field of forming technology. The surface treatment of the samples has proven to be mandatory in the investigations.","PeriodicalId":53690,"journal":{"name":"Tribologie und Schmierungstechnik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48826832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Patrick Strobl, Marianne Trapp, K. Völkel, H. Pflaum, K. Stahl
Detailed knowledge of the influences on the frictional behavior is crucial for reliable operation of safety-relevant, wet-running multi-plate clutches. The breakaway torque is of particular interest for safety-critical applications such as safety brakes and clutches. While influences of the tribological system by variation of friction partners, lubricant and operating conditions are usually the focus of current investigations, the influence of the time of standstill between a preceding tribological load and a subsequent breakaway of the wet disk clutch is not considered. To determine this influence, experimental investigations are carried out on a component test rig. For this purpose, the time of standstill of the clutch is systematically varied after preceding load shifts and the clutch is then broken away. During these investigations, it is shown that the downtime of multi-plate clutches with sinter friction lining has considerable influence on the frictional behavior in the first switching operations after actuation. An influence can already be clearly seen at a standstill time of approximately 15 minutes. An increase in the maximum friction coefficient occurring at the start of the slip switching operation compared with subsequent slip switching operations was observed, which can be attributed to the downtime after a defined preload. Influences of the disk temperature are considered by measuring the outer disk temperature. The influence is attributed to the change of the boundary layer during the standstill. The results provide a contribution to the transferability of investigations of the friction behavior of component test rigs to real applications in which the friction system is exposed to relevant times of standstill and expand the existing knowledge base on test methods.
{"title":"Einfluss der Stillstandszeit auf das Losreißmoment nasslaufender Lamellenkupplungen","authors":"Patrick Strobl, Marianne Trapp, K. Völkel, H. Pflaum, K. Stahl","doi":"10.24053/tus-2022-0044","DOIUrl":"https://doi.org/10.24053/tus-2022-0044","url":null,"abstract":"Detailed knowledge of the influences on the frictional behavior is crucial for reliable operation of safety-relevant, wet-running multi-plate clutches. The breakaway torque is of particular interest for safety-critical applications such as safety brakes and clutches. While influences of the tribological system by variation of friction partners, lubricant and operating conditions are usually the focus of current investigations, the influence of the time of standstill between a preceding tribological load and a subsequent breakaway of the wet disk clutch is not considered. To determine this influence, experimental investigations are carried out on a component test rig. For this purpose, the time of standstill of the clutch is systematically varied after preceding load shifts and the clutch is then broken away. During these investigations, it is shown that the downtime of multi-plate clutches with sinter friction lining has considerable influence on the frictional behavior in the first switching operations after actuation. An influence can already be clearly seen at a standstill time of approximately 15 minutes. An increase in the maximum friction coefficient occurring at the start of the slip switching operation compared with subsequent slip switching operations was observed, which can be attributed to the downtime after a defined preload. Influences of the disk temperature are considered by measuring the outer disk temperature. The influence is attributed to the change of the boundary layer during the standstill. The results provide a contribution to the transferability of investigations of the friction behavior of component test rigs to real applications in which the friction system is exposed to relevant times of standstill and expand the existing knowledge base on test methods.","PeriodicalId":53690,"journal":{"name":"Tribologie und Schmierungstechnik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44056895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In rib-guided roller bearings, there are a large number of different tribological contact forms. These include not only line contacts on the raceways, the cage and the rolling elements, but also point and elliptical contacts between the rolling element end face and the ring rib. Load is transmitted via these lubricated, concentrated rolling and rolling-sliding contacts. Depending on the load situation, these contacts contribute differently to the operating behavior of the roller bearing. Axial loads on rib-guided roller bearings are mainly transmitted via the point and elliptical contacts between the roller end and the ring rib. These oil-lubricated point and elliptical contacts can be calculated and designed using thermos-elastohydrodynamic (TEHD) simulations. In existing methods for the TEHD calculation of point and elliptical contacts, the macroscopic geometries of the contact partners are described in a simplified manner, similar to the theory according to HERTZ, using ellipsoids. However, contacts of real, complex geometry pairings of rolling elements and ribs, as used to optimize the axial load capacity or the frictional torque of roller bearings, can only be determined inaccurately with this method. Compared to the exact consideration of the macroscopic geometry, larger discrepancies in the lubricant film height, contact pressure and friction can be observed. For this reason, this paper presents a TEHD simulation that considers the exact macroscopic geometry of point or elliptical contacts. The macroscopic geometry is generated using mathematical functions and a ray-tracing method is used to generate the equivalent body for the TEHD simulation. Different geometry pairings of sphere, plane, cone and torus are investigated. The results for lubricant film height, contact pressure and friction are compared with the results from conventional TEHD simulations, which use a geometry description via ellipsoids. By comparing the calculated geometry pairings, the possibilities and limitations of the modified geometry description are assessed.
{"title":"Using exact macroscopic geometry in elastohydrodynamic simulations of point and elliptical contacts","authors":"Sven Wirsching, M. Bartz","doi":"10.24053/tus-2022-0045","DOIUrl":"https://doi.org/10.24053/tus-2022-0045","url":null,"abstract":"In rib-guided roller bearings, there are a large number of different tribological contact forms. These include not only line contacts on the raceways, the cage and the rolling elements, but also point and elliptical contacts between the rolling element end face and the ring rib. Load is transmitted via these lubricated, concentrated rolling and rolling-sliding contacts. Depending on the load situation, these contacts contribute differently to the operating behavior of the roller bearing. Axial loads on rib-guided roller bearings are mainly transmitted via the point and elliptical contacts between the roller end and the ring rib. These oil-lubricated point and elliptical contacts can be calculated and designed using thermos-elastohydrodynamic (TEHD) simulations. In existing methods for the TEHD calculation of point and elliptical contacts, the macroscopic geometries of the contact partners are described in a simplified manner, similar to the theory according to HERTZ, using ellipsoids. However, contacts of real, complex geometry pairings of rolling elements and ribs, as used to optimize the axial load capacity or the frictional torque of roller bearings, can only be determined inaccurately with this method. Compared to the exact consideration of the macroscopic geometry, larger discrepancies in the lubricant film height, contact pressure and friction can be observed. For this reason, this paper presents a TEHD simulation that considers the exact macroscopic geometry of point or elliptical contacts. The macroscopic geometry is generated using mathematical functions and a ray-tracing method is used to generate the equivalent body for the TEHD simulation. Different geometry pairings of sphere, plane, cone and torus are investigated. The results for lubricant film height, contact pressure and friction are compared with the results from conventional TEHD simulations, which use a geometry description via ellipsoids. By comparing the calculated geometry pairings, the possibilities and limitations of the modified geometry description are assessed.","PeriodicalId":53690,"journal":{"name":"Tribologie und Schmierungstechnik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48578679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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