Morphology of FZG-A Test Gears

Nomenclature FZG-A FZG type A test gears LOM Light Optical Microscopy SEM Scanning Electron Microscopy SAP Start of Active Profile EAP End of Active Profile Introduction This study explores the failure mode morphology of FZG-A test gears. It aims to examine the morphologies of scuffing, scoring, scratches, and polishing using high-magnification light optical microscopy (LOM) and scanning electron microscopy (SEM) images.

Specifications for FZG-A Tests

The FZG-A test rig is described, including specifications for the test procedures according to the industrial standards ISO 14635-1 (Ref. 1), ASTM 5182-19 (Ref. 2), and CEC L-07-95 (Ref. 3). These three standards are considered technically equivalent. Description of Figure 1 Figure 1 illustrates an FZG-A spur pinion with 16 teeth that meshes with a spur gear featuring 24 teeth. Detailed geometric information about both the pinion and the gear can be found in Annex A. For the LOM and SEM investigation, teeth 2 and 3 were removed by cutting along the red radial lines indicated in the figure.Description of Figure 2 Figure 2 illustrates scuffing on teeth 2 and 3. Tooth 2 exhibits scuffing nearly across the entire face width, while tooth 3 shows a narrow band of scuffing. The other teeth, which do not exhibit scuffing, display the unique surface texture produced by the MAAG 15-degree crisscross grinding method.

Description of the FZG-A Test The FZG-A gear test consists of twelve 15-minute stages, each with increasing load, until scuffing occurs or the testing sequence is completed. After load stage 4, and at the end of each subsequent stage, the pinion tooth flanks are visually inspected for signs of scuffing, which are recorded. The visual inspection is done without removing the gears from the test rig, and without the aid of magnification. The test concludes when the summed total width of scuffing on all 16 pinion teeth exceeds 20 mm, and the failure load stage is reported. If load stage 12 is completed without any scuffing, the failure load stage is reported as greater than 12. FZG-A Failure Mode Four failure modes can occur in FZG-A test gears, including scuffing, scoring, scratches and polishing. ASTM 5182-19 defines the failure modes as follows: Scuffing—wear due to localized bonding between contacting solid surfaces leading to material transfer between the two surfaces or loss from either surface. Scoring—a severe form of wear characterized by the formation of extensive grooves and scratches in the direction of sliding. Scratches—the result of mechanical removal or displacement, or both, of material from a surface by the action of abrasive particles or protuberances sliding across the surfaces. Polishing—a mild form of abrasive wear resulting in minor loss of material and typically characterized by a smooth finish and removal of all or part of the initial grinding marks. Description of Figure 3 Figure 3 shows the scuffing observed on tooth 2, which is also illustrated in Figure 2. The scuffing measures 19.5 mm in width, almost covering the total face width of 20 mm. To the unaided eye, or when viewed under LOM, the scuffed area appears as a dull grey surface. An enlarged SEM image of Box 1 is shown in Figure 4, followed by a series of SEM images of Box 2 at progressively higher magnifications.