Scratch phenomenon on the outer diameter of the rolling element of the failed bearing: the circumferential dent in the contact area of u200bu200bthe rolling element. There are parallel circumferential traces on the rollers, see Figures 70 and 71. For balls, yarn balls are often seen, see Figure 72. Not to be confused with edge marks (see section 3.3.2.6). The edge of the trajectory formed by the edge movement is smooth due to plastic deformation, and the abrasion has a sharp edge. Hard particles are often embedded in the cage pockets, causing scratches, see Figure 73. Reason: contaminated lubricant; hard particles embedded in the cage pockets, which act like abrasive particles on the grinding wheel. Remedial measures: to ensure clean installation conditions, improve sealing, and filter lubricant. Slip marks of failed bearings: rolling elements slip, especially large and heavy roller bearing models, such as full complement bearings. Slip causes the raceway or rolling elements to become rough. The material is often piled up and accompanied by drag marks. It is usually not evenly distributed on the surface but in dots, see Figures 74 and 75. Small pitting corrosion is often found, please refer to section 3.3.2.1 of fatigue caused by poor lubrication. Reason: When the load is too low and the lubrication is poor, the rolling elements slip on the raceway. Sometimes because the load-bearing area is too small, the roller decelerates rapidly in the cage pockets of the non-load-bearing area, and then accelerates sharply when entering the load-bearing area. The speed changes rapidly. Remedial measures: Use bearings with low load carrying capacity. Bearing preload, such as springs. Reduce bearing clearances. Ensure sufficient load when there is no load. Improve lubrication.