Maintenance and Failure Analysis
Routine Inspection
Warpage Measurement: Use a dial indicator to detect the circular runout of the outer edge end face of the steel sheet on a lathe. The allowable value is ≤ 0.15mm. If it exceeds 0.2mm, thermal compression correction or replacement is required.
Hardness Testing: A portable Leeb hardness tester is used, with focus on testing the friction surfaces and gear hub parts. If the hardness fluctuation exceeds HRC 3, re-heat treatment is necessary.
Crack Detection: Fluorescent penetrant is used to inspect the edges of the steel sheet and the area around the weight-reduction holes. If a crack with a length > 1mm is found, the steel sheet must be scrapped.
Failure Modes and Countermeasures
Thermal Deformation: When the surface temperature of the steel sheet exceeds 600°C, wavy collapse will occur. Solutions include adding heat dissipation grooves (width: 2-3mm, depth: 1-1.5mm) and using hollow rivets (diameter: 4mm, wall thickness: 0.5mm) to enhance convection.
Fatigue Fracture: Under alternating stress, fatigue cracks are prone to occur at the root of the steel sheet's gear hub. Through shot peening strengthening (Almen intensity: 0.3-0.4A), a compressive stress layer of 0.2-0.3mm can be formed on the surface, increasing the fatigue life by more than 50%.
Key Terminology Notes
dial indicator: A precision measuring instrument used to detect small linear displacements or runout.
Leeb hardness tester: A portable device for measuring material hardness based on the Leeb hardness test principle, suitable for on-site testing of large workpieces.
fluorescent penetrant: A non-destructive testing material that penetrates surface cracks and emits fluorescence under ultraviolet light to reveal defects.
shot peening strengthening: A surface treatment process that bombards the material surface with high-velocity spherical media to induce compressive residual stress and improve fatigue resistance.
Almen intensity: A parameter used to quantify the intensity of shot peening, with "A" representing the standard Almen strip type.
