contact pressures and sliding speeds under friction, lead to the collapse of the lubricating film. Without lubrication, the contacting surfaces become bonded, effectively welding together. Due to the rolling motion, these weldings are immediately torn apart, resulting in a roughened surface. The failure mode is characterized by scuffing marks that align with the rolling direction. Adhesive effects cause material to be removed from the surface and transferred to the counter body. Over time, roughened areas and transferred material become partially run in after a certain number of load cycles. [CZI20; LIN22; NIE03; SOM18; VOR23] Lubricants are evaluated for their scuffing load-carrying capacity using an FZG gear test machine, following the test procedures specified in DIN ISO 14635-1 [DIN06]. These test methods provide the basis for determining characteristic values of lubricants which are essential for calculating the scuffing load-carrying capacity for gears. The tests employ the standardized FZG test gears type A Science and Research 14 Tribologie + Schmierungstechnik · volume 72 · issue 3-4/ 2025 DOI 10.24053/ TuS-2025-0014 1 Introduction A variety of standardized test procedures exists for investigating lubricants. In addition to gears, analogy tests are conducted using test specimens with a simpler geometry, such as the tribological subsystems ball-on-ball [DIN15], ball-on-disc [PCS24] or disc-on-disc [OPT24]. On a tribological view, gear meshing is characterized by varying slide-to-roll ratios. In contrast, most of these subsystems only accommodate constant slide-to-roll ratios. The closest approximation to gear meshing is achieved by using discs as specimens but limitations arise due to the stationary contact conditions. This article introduces new test specimens featuring a variable disc radius. These non-circular discs enable the implementation of locally varying slide-to-roll ratios, offering a higher degree of similarity to gear meshing compared to conventional disc contacts. The research includes tests with non-circular discs on a two-disc tribometer and reference tests with gears on an FZG gear test machine, both evaluating the scuffing load-carrying capacity of various test oils. The results of these tests are discussed in this article. 2 State of research and technology Scuffing is a type of failure that occurs spontaneously due to the loss of lubrication from temporary overloading. The wear mechanism responsible for scuffing is adhesion. Excessive contact temperatures, caused by high Test method using non-circular discs with a locally varying slide-to-roll ratio to investigate scuffing Nadja Aufderstroth, Lennart Schierholz, Jaacob Vorgerd, Manuel Oehler* submitted: 20.09.2024 accepted: 11.08.2025 (peer review) Presented at GfT Conference 2024 Lubricant and wear tests are conducted using both test-specific gears and specimens such as balls or discs. To enhance the disc-disc subsystem, a test specimen was developed whose geometry allows for locally varying slide-to-roll ratios similar to those in gear meshing while maintaining a constant shaft speed. Scuffing load-carrying capacity tests were performed with non-circular discs on a two-disc tribometer and with gears on an FZG gear test machine, following the FZG test procedures. The results demonstrated a strong correlation between the disc and gear tests. In the process, the scuffing load-carrying capacity classes for various lubricants were determined. Additionally, the pv values at the damage points were equivalent for both setups. Keywords discs, analogy tests, two-disc tribometer, slide-to-roll ratio, scuffing load-carrying capacity, adhesion Abstract * Nadja Aufderstroth, M.Sc. (corresponding author) ORCID-ID: https: / / orcid.org/ 0009-0001-9160-3442 Lennart Schierholz, M.Sc. ORCID-ID: https: / / orcid.org/ 0009-0003-5581-233X Dr.-Ing. Jaacob Vorgerd ORCID-ID: https: / / orcid.org/ 0000-0003-0232-2479 Prof. Dr.-Ing. Manuel Oehler ORCID-ID: https: / / orcid.org/ 0000-0001-8251-0896 Lehrstuhl für Antriebstechnik (ante) Fakultät für Maschinenbau, Ruhr-Universität Bochum Universitätsstr. 150, 44801 Bochum which are noted for their uneven slide-to-roll ratio. At the contact point D, the maximum contact pressure and a slide-to-roll ratio of 106 % are observed (Eq. 1). (1) In the development of lubricants, numerous tests are conducted using analog test specimens which enable a cost-efficient and flexible testing. Established tribometers primarily employ the disc-on-disc [OPT24] or ballon-disc [ING15; LI13; PCS24] sub-systems to simulate the tribological conditions. Analogy tests have proven valuable for determining the scuffing load-carrying capacity of lubricants [CON23], the influence of surface treatments [ALN04; PAT95], and the frictional properties [CIH23; GRE22]. However, their transferability is limited due to the stationary contact conditions. During these tests, moderate slide-to-roll ratios (SRR < 50 %) are typically used under constant load conditions. Particularly at high slide-to-roll ratios, substantial cooling is necessary to stabilize the thermal conditions due to heat emission [SAV17]. Analogy tests using the disc-on-disc subsystem typically operate with stationary slide-to-roll ratios. To better replicate gear meshing, it is desirable to achieve locally varying slide-to-roll ratios. One approach involves using a tribometer with elliptic gears to create variable slide-toroll ratios in the contact between two discs with constant radii, which has been used to investigate the scuffing load-carrying capacity [BRE17]. Another approach is to adapt the disc geometry to achieve variable slide-to-roll ratios, for which a corresponding model test rig has been developed [TEN16]. Micro pitting tests were successfully carried out on this test rig [SCH24; TEN22]. 3 Modelling of non-circular discs In gear meshing, locally varying speeds influence the tribological stress and can lead to gear damage such as = 2 ∙ s Σ = 2 ∙ ( t1 − t2 ) t1 + t2 scuffing [CZI20; LIN22]. The disc geometry is designed based on the law of gearing, allowing for the modelling of specimens to generate locally varying slide-toroll ratios during one full rotation. Figure 1 illustrates the model of the non-circular discs. The distance between the centers of rotation O 1 and O 2 corresponds to the center distance a. The pressure angle α defines the angle between the center distance and the contact normal. The pitch point C is located in the center between O 1 and O 2 . The base circle radii r b1 and r b2 are perpendicular to the contact normal. The contact point K, whose contact plane is orthogonal to the contact normal, moves along this line. The minimal radii r min1 and r min2 serve as the starting values for the disc contour generation and are located at the disc angle φ = 180°. The disc contour is symmetric about the x-axis and extends from φ = 0° to φ = 180° for each side. In this article, the basic concept is presented, while the derivation of the disc geometry and its modelling are described in detail in [AUF25]. To ensure a continuous and smooth meshing, the principles of cam design are applied in contour calculations (Figure 1). The infinitesimal change of the contact point must occur within the contact plane (Eq. 2). [ANG91; ROT04]. (2) The contact radius r 1 is calculated using the base circle radius r b1 and the angles α and δ 1 (Eq. 3). The base circle radius r b1 is determined based on the center distance a and the pressure angle α (Eq. 4). (3) (4) The angle δ 1 represents the relative angle from the contact normal to the contact radius r 1 (Eq. 5). The contact 1 1 = 1 ∙ tan ( + 1 ) 1 = b1 sin ( + 1 ) b1 = 0,5 ∙ ∙ sin ( ) Science and Research 15 Tribologie + Schmierungstechnik · volume 72 · issue 3-4/ 2025 DOI 10.24053/ TuS-2025-0014 Figure 1: Geometric model of the non-circular discs with a constant contact normal and depiction of the contact point motion within the contact plane (6) (7) To adjust the relative speed ratios, the non-circular discs are scaled according to the size ratio u (Eq. 8). (8) The pressure angle over a full disc rotation is shown in Figure 2. Between φ A and φ E , the pressure angle remains constant with a value of 22.5°, and is equal to the normal pressure angle α n . In this region, the contact point moves along the contact normal, and the disc contour follows an involute shape. To ensure a continuous rotary motion of the disc, the disc contour from 0° to 180° is mirrored. In order to connect these regions, a transition function is required that fades smoothly. For this purpose, a continuously differentiable Bézier function is generated based on interpolation points, where the final interpolation point determines the target pressure angle which corresponds with α n . For the scuffing tests, the disc variant S70-A is used, for which the specifications are shown in Table 1. In this 1 , 2 = + 1 , 2 2 = � ( − 1 ∙ cos ( 1 )) 2 + ( 1 ∙ sin ( 1 )) 2 = min1 min2 Science and Research 16 Tribologie + Schmierungstechnik · volume 72 · issue 3-4/ 2025 DOI 10.24053/ TuS-2025-0014 radius r 2 is then determined using δ 1 (Eq. 6). The angle ξ represents the deviation from the x-axis to the contact radii and is derived from the sum of the angles φ and δ (Eq. 7). (5) 1 = arcsin � 0,5 ∙ ∙ sin ( ) 1 � − Figure 2: Pressure angle over a full disc rotation Description Symbol Value Unit Center distance a 70.0 mm Normal pressure angle α n 22.5 ° Disc width b 10.0 mm Size ratio u 1.4 - Crowning c b 15.0 μm Arithmetic mean roughness Ra 0.1 μm Table 1: Specifications for the disc variant S70-A 0 30 60 90 120 150 180 0 500 1,000 1,500 contact pressure [MPa] 0 2 4 6 force [kN] contact pressure p H normal force F n φ A φ E φ C 2,000 8 F = 3 kN disc -10 -5 0 5 10 speed [m/ s] sum speed v Σ sliding speed v s φ A φ E φ C rotation angle [°] φ n = 1,000 rpm disc 0 1 2 3 4 disc width [mm] 0 1 2 3 4 rolling direction [mm] -4 -2 0 2 4 profile height [µm] φ A φ C φ E 0° 180° 0 30 60 90 120 150 180 + - Figure 3: Disc variant S70-A: Contact pressure and normal force (upper left) and sum speed and sliding speed (lower left) over half a disc rotation, disc sample (upper right) and representative section of an optical measurement of the disc surface at new condition (lower right) disc notation, S refers to the specimen, 70 represents the center distance, and A denotes the FZG test gears type A used in scuffing tests (hereafter referred to as type A gears). Because of the size ratio, the discs are of different sizes, with specimens categorized as S1 for the large disc and S2 for the small disc. For comparison, the parameters contact pressure, force, sum speed, and sliding speed are shown for both the S70-A discs and type A gears in Figure 3 and Figure 4. The size ratio of the discs enables the implementation of an uneven slide-to-roll ratio, with higher values in the area of positive sliding than negative sliding, based on the type A gear design. The contact pressure is likewise unevenly distributed. The disc surface features a 15 µm crowned finish and has been treated with tangential grinding, resulting in grinding grooves in the rolling direction, creating a uniform texture (Figure 3). The tooth flank surface of the type A gears exhibits the typical Maag 15 cross-hatch pattern (Figure 4). With an arithmetic mean roughness Ra of 0.1 µm measured in axial direction, the disc surface is smoother than the tooth flanks of the type A gears, which have an arithmetic mean roughness of 0.35 µm [DIN06]. 4 Experiments The scuffing load-carrying capacity tests are performed according to the FZG test procedures A/ 8.3/ 90 and A/ 16.6/ 90 on an FZG gear test machine, as specified in DIN ISO 14635-1 [DIN06]. Dip-lubrication is used, and the initial oil temperature of 90 °C is uncontrolled during the tests. Each test consists of twelve load stages including contact pressures from 146 to 1,841 MPa, with each stage lasting for 15 minutes (Table 2). The load increases after each completed load stage. The load stage at which scuffing damage occurs is referred to as the failure load stage. The disc tests were carried out on a two-disc tribometer. The testing procedure for the discs is in line with the FZG test procedures and includes the load stages four through twelve (Table 2). For each load stage, the test load on the two-disc tribometer was adjusted to ensure that the contact pressure at the pitch point of the discs matched that of the type A gears. The discs tests were conducted with injection lubrication and a controlled oil Science and Research 17 Tribologie + Schmierungstechnik · volume 72 · issue 3-4/ 2025 DOI 10.24053/ TuS-2025-0014 -0.5 0 0.5 1.0 1.5 0 500 1,000 1,500 contact pressure [MPa] 0 2 4 6 force [kN] 2,000 8 -10 -5 0 5 10 meshing coordinate [-] A C B D E -0.5 0 0.5 1.0 1.5 sum speed v Σ sliding speed v s speed [m/ s] T = 94 Nm pinion n = 1,450 rpm pinion normal force F n contact pressure p H - + 0 1 2 3 4 disc width [mm] 0 1 2 3 4 rolling direction [mm] -4 -2 0 2 4 profile height [µm] A B E Figure 4: Type A gears: Contact pressure and normal force (upper left) and sum speed and sliding speed (lower left) during meshing, gear sample (upper right) and representative section of an optical measurement of the tooth flank surface at new condition (lower right) Description Type A gears Discs S70-A Unit Test duration per load stage 15 15 min Load stages 1 - 12 4 - 12 - Contact pressure at pitch point 146 - 1,841 621 - 1,841 MPa Sum speed at pitch point 6.6 | 13.2 6.6 | 13.2 m/ s Rotational speed 1,500 | 3,000 1,000 | 2,000 rpm Oil temperature 90 (test start) 60 °C Lubrication Dip-lubrication Injection lubr. - *Gear test with SLC-1 : injection lubrication with a controlled oil temperature of 60 °C Table 2: Test parameters for gear and disc tests torque in the shafts. Lubricant is injected into each disc pair through a nozzle positioned at the midpoint of the center distance 5. The oil injection temperature and flow rate are monitored. 5 Experimental results on scuffing load-carrying capacity The tests revealed that the employed procedures cause scuffing damage to the discs. The analogy between the disc tests and gear tests is illustrated by the failure load stages (Figure 6). Tests conducted at higher speeds resulted in a lower failure load stage for both disc and gear tests. Using test oil SLC-H, both setups exhibited no scuffing with a failure load stage exceeding twelve. The disc tests show a consistent deviation of approximately two failure load stages, corresponding to around 300 MPa, compared to the gear tests. For this test plan, the gear test with SLC-L1 does not show a significant influence of the oil temperature and lubrication on the scuffing load-carrying capacity as demonstrated by the failure load stages. Science and Research 18 Tribologie + Schmierungstechnik · volume 72 · issue 3-4/ 2025 DOI 10.24053/ TuS-2025-0014 temperature of 60 °C, due to the system’s configuration. The test oils are categorized based on their scuffing loadcarrying capacity (SLC): two oils with low (L1 and L2), one oil with medium (M), and one oil with high (H) scuffing load-carrying capacity. The gear test with test oil SLC-L1 was carried out with a controlled oil temperature of 60 °C and injection lubrication, in order to determine the influence of these conditions on the scuffing load-carrying capacity during the tests. On the two-disc tribometer, the discs are mounted at the ends of the shafts, with each disc pair rotated 180° relative to the other 1 (Figure 5). The discs are driven by a synchronization gearbox with a gear ratio of -1 2. The required test force, measured by a load cell, is applied through a hydraulic cylinder and transmitted to the discs via a yoke and bearings 3. Acceleration sensors are attached to the yoke’s rocker arms. The disc force acts toward the centers of rotation and is supported at the contact point by the normal force, which bypasses the rotational axis, thereby generating torque 4. The double-disc arrangement compensates for the alternating Figure 6: Overview of the failure load stages from the gear and disc tests for all test oils Figure 5: Two-disc tribometer and depiction of a mounted disc pair The absolute sliding speeds of the discs are slightly lower than these of the type A gears due to the design and show a slide-to-roll ratio of 80 % at the damage point. Since the current setup of the two-disc tribometer does not yet allow for friction measurements, the friction-independent pv value is used to evaluate the scuffing load-carrying capacity on a tribological level [DYS75]. The pv value describes the contact-specific power and is determined by the product of the highest contact pressure and corresponding sliding speed at the point of scuffing. For both disc and gear tests, the pv values remain consistent across different test oils, irrespective of the test setup (Figure 7). 5.1 Damage analysis The scuffing damage on the disc exhibits a damage pattern similar to that observed on gears, with scuffing marks aligned with the rolling direction and resulting in material removal (Figure 8). The damage is evenly distributed across the disc surface but does not cover the entire width of the surface because of the crowning. Regarding the shape, the damage starts narrowly, widens to its maximum point, and then tapers slightly. Due to the test procedure, the damaged area on the disc appears more roughened since tests on the two-disc tribometer are terminated immediately after scuffing occurs, which is clearly indicated by an increase in vibration speed. As a result, the disc surface remains more worn compared to the gear surface. The damaged surface on the gear extends over two-thirds of the tooth flank in the rolling direction and across the full width of the active tooth flank (Figure 9). In both setups, the scuffing damage occurred in areas with the highest contact pressures and high positive sliding speeds. Science and Research 19 Tribologie + Schmierungstechnik · volume 72 · issue 3-4/ 2025 DOI 10.24053/ TuS-2025-0014 Figure 7: pv diagram of the damage points from the gear and disc tests for all test oils 3 disc width [mm] -20 -10 0 10 20 profile height [µm] 0 0 3 rolling direction [mm] 1 2 1 2  = 13.2 m/ s v Σ,C  failure load stage 8  p = 1,285 MPa H,max  test oil SLC-L1 Test parameters 0 500 1,000 1,500 contact pressure [MPa] 0 2 4 6 force [kN] φ A φ E φ C 2,000 8 -20 -10 0 10 20 speed [m/ s] rotation angle [°] φ φ A φ C φ E ω 2 v t 0 30 60 90 120 150 180 0 30 60 90 120 150 180 contact pressure p H normal force F n sum speed v Σ sliding speed v s Figure 8: Scuffing damage on a disc and a representative section of an optical measurement of the disc surface after testing (left), contact pressure and normal force (upper right) and sum speed and sliding speed (lower right) over half a disc rotation analogy to gear meshing in tests, as the tribological contact conditions of gears can be more accurately replicated. The two-disc tribometer, combined with the use of non-circular discs, provides an effective test method for determining the scuffing load-carrying capacity based on FZG test procedures. The disc tests produced comparable scuffing damage and demonstrated a strong correlation with the gear tests. The higher failure load stages Science and Research 20 Tribologie + Schmierungstechnik · volume 72 · issue 3-4/ 2025 DOI 10.24053/ TuS-2025-0014 6 Conclusion The non-circular discs enable the implementation of locally varying slide-to-roll ratios. The geometric design provides continuous and smooth meshing while forming a contour with a variable disc radius. Besides, the disc contour partially consists of curvature radii ratios that correspond to those of involute gears. This improves the -0.5 0 0.5 1.0 1.5 0 500 1,000 1,500 contact pressure [MPa] 0 2 4 6 force [kN] 2,000 8 -20 -10 0 10 20 speed [m/ s] meshing coordinate [-] A C B D E -0.5 0 0.5 1.0 1.5 v t 3 tooth width [mm] -10 -5 0 5 10 profile height [µm] 0 0 3 rolling direction [mm] 1 2 1 2  = 13.2 m/ s v Σ,C  p = 823 MPa H,max  test oil SLC-L1  failure load stage 5 Test parameters E B A normal force F n contact pressure p H sum speed v Σ sliding speed v s Figure 9: Scuffing damage on a type A gear and a representative section of an optical measurement of the gear surface after testing (left), contact pressure and normal force (upper right) and sum speed and sliding speed (lower right) during meshing Nomenclature A, B, D, E - Meshing points C - Pitch point F disc N Disc force F n N Normal force F test N Test force K - Contact point O - Center of rotation Ra µm Arithmetic mean roughness SRR - Slide-to-roll ratio T pinion Nm Torque pinion V oil l/ min Oil volume flow a mm Center distance b mm Disc width c b µm Crowning n disc rpm Rotational speed disc n pinion rpm Rotational speed pinion p H MPa Contact pressure p H,max MPa Maximal contact pressure pv kW/ mm 2 Contact-specific power r mm Contact radius r b mm Base circle radius r min mm Minimal disc radius u - Size ratio v s m/ s Sliding speed v t m/ s Tangential speed v Σ m/ s Sum speed v Σ,C m/ s Sum speed at pitch point α ° Pressure angle α n ° Normal pressure angle δ ° Auxiliary angle ξ ° Disc angle φ ° Rotation angle ω °/ s Angular speed 1, 2 Indices for large, small disc DIN German Institute for Standardization ISO International Organization for Standardization SLC Scuffing load-carrying capacity observed in the disc tests can be attributed to the lower sliding speeds compared to the type A gears. Therefore, a higher contact pressure is required to cause scuffing on the discs. Another aspect are the larger curvature radii of the discs which leads to a lower contact temperature at the same friction power due to the larger contact area. Moreover, the disc surface is smoother due to the grinding process which influences the friction and lubrication behavior. On a tribological level, the friction-independent pv value shows a strong correlation between the disc and gear tests. For further investigations, the setup of the two-disc tribometer should be upgraded to include friction and temperature measurement capabilities in order to determine friction-dependent parameters such as flash temperature. Furthermore, this would facilitate a more precise thermal analysis of the disc contact, as both the bulk temperature and the coefficient of friction can be used to determine the contact temperature. Literature [ALN04] Alanou, M. P.; Evans, H. P.; Snidle, R. W.: “Effect of different surface treatments and coatings on the scuffing performance of hardened steel discs at very high sliding speeds”. In: Tribology International 37 (2004). [ANG91] Angeles, J.; López-Cajún, C. S.: “Optimization of Cam Mechanics”. 1. Auflage. Springer Dordrecht, 1991. [AUF25] Aufderstroth, N, Schierholz, L., Vorgerd, J., Oehler, M.: “Modelling of non-circular discs as test specimens for gear analogy tests”. In: Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology (2025) [BRE17] Brecher, C.; Löpenhaus, C.; Mevissen, D.: „Zwei- Scheiben-Tribometer mit variablem Schlupfverlauf“. In: Antriebstechnik 12/ 2016 (2016). [CIH23] Cihak-Bayr, U.; Wopelka, T.; Wintersteiger, C.: “Investigation of friction and scuffing during loss of lubrication on a high velocity twin-disc test rig”. In: Forschung im Ingenieurwesen 87 (2023). [CON23] Contreras Urgiles, R. W.; Echávarri Otero, J.; Chacón Tanarro, E.; Franco Martínez, F.; Cortada-García, M.: “A test for evaluating the scuffing performance of fully-formulated lubricants”. In: Tribology International 187 (2023). [CZI20] Czichos, H.; Habig, K.-H.: “Tribologie-Handbuch: Tribometrie, Tribomaterialien, Tribotechnik”. 5., überarbeitete und erweiterte Auflage. Springer Vieweg, 2020. [DIN06] DIN ISO 14635-1: „Zahnräder - FZG-Prüfverfahren - Teil 1: FZG-Prüfverfahren A/ 8,3/ 90 zur Bestimmung der relativen Fresstragfähigkeit von Schmierölen (ISO 14635-1: 2000)“. 2006. [DIN15] DIN 51350-1: „Prüfung von Schmierstoffen - Prüfung im Vierkugel-Apparat - Teil 1: Allgemeine Arbeitsgrundlagen“. 2015. [DYS75] Dyson, A.: “Scuffing - a review: Part 2: The mechanism of scuffing”. In: Tribology International 3 (1975). [GRE22] Grenet de Bechillon, N.; Touret, T.; Cavoret, J.; Changenet, C.; Ville, F.: “A new experimental methodology to asses gear scuffing initiation”. In: Tribology - Materials, Surfaces & Interfaces 16 (2022). [ING15] Ingram, M.; Hamer, C.; Spikes, H.: “A new scuffing test using contra-rotation”. In: Wear 328 - 329 (2015). [LI13] Li, S.; Kahraman, A.; Anderson, N.; Wedeven, L. D.: “A model to predict scuffing failures of a ballon-disc contact”. In: Tribology International 60 (2013). [LIN22] Linke, H.; Börner, J.: „Stirnradverzahnungen: Berechnung - Werkstoffe - Fertigung“. 3., aktualisierte Auflage. Hanser Verlag, 2022. [NIE03] Niemann, G.; Winter, H.: „Maschinenelemente 2: Getriebe allgemein, Zahnradgetriebe - Grundlagen, Stirnradgetriebe“. 2. Auflage. Springer, 2003. [OPT24] Optimol Instruments: 2disk - Zwei-Scheiben-Prüfstand. [online] URL: https: / / optimol-instruments.de/ de/ produkte/ 2disk/ (Stand: 19.08.2024). [PAT95] Patching, M. J.; Kweh, C. C.; Evans, H. P.; Snidle, R. W.: “Conditions for Scuffing Failure of Ground and Superfinished Steel Disks at High Sliding Speeds Using a Gas Turbine Engine Oil”. In: Journal of Tribology 117 (1995). [PCS24] PCS Instruments: MTM [online] URL: https: / / pcs-instruments.com/ product/ mtm/ (Stand: 19.08.2023). [ROT04] Rothbart, H. A., Hrsg.: “Cam Design Handbook”. McGraw-Hill, 2004. [SAV17] Savolainen, M.; Lehtovaara, A.: “An experimental approach for investigating scuffing initiation due to overload cycles with a twin-disc test device”. In: Tribology International 109 (2017). [SCH24] Schierholz, L.; Aufderstroth, N.; Vorgerd, J.: „Analogieuntersuchungen an unrunden Zahnscheiben mit tribologisch äquivalenten Lastbedingungen wie im Zahneingriff“. In: Dresdner Maschinenelemente Kolloquium (2024). [SOM18] Sommer, K.; Heinz, R.; Schöfer, J.: „Verschleiß metallischer Werkstoffe: Erscheinungsformen sicher beurteilen“. 3. Auflage. Springer Vieweg, 2018. [TEN16] Tenberge, P.; Weibring, M.; Gondecki, L. (2016) Modellprüfstand (DE 10 2016 015 529.9). Deutsches Patent- und Markenamt. URL: https: / / register.dpma.de/ DPMAregister/ pat/ register? AKZ=1020160155299&CURSOR=0. [TEN22] Tenberge, P.; Vorgerd, J.; Gondecki, L.: “2-disc tribometer for various tests on sliding/ rolling contacts with tribological loads such as in tooth flank contacts”. In: VDI-Berichte Nr. 2389 (2022). [VOR23] Vorgerd, J.: “Wirkungsgrad und Fresstragfähigkeit schnelllaufender Stirnradverzahnungen mit chemisch glattgeschliffenen Oberflächen”. Dissertation Ruhr-Universität Bochum, 2023. Science and Research 21 Tribologie + Schmierungstechnik · volume 72 · issue 3-4/ 2025 DOI 10.24053/ TuS-2025-0014