Two common causes of needle roller bearing damage

  1. Contact fatigue failure. Under the action of high contact stress, after many stress cycles, pits will be generated in the local area of the working surface, which will increase the noise, vibration, temperature and wear of the bearing during operation. The bearing cannot operate normally;

      2. Wear caused by relative activity. The normal form of failure of rolling bearings is usually fatigue spalling.

       The fatigue failure of bearing steel includes two processes: the generation and development of fatigue cracks.

       The initial fatigue crack occurs at a certain depth from the surface, which is exactly the same as the maximum shear stress. For ordinary size needle roller bearings with different loads, the maximum shear stress should appear at a depth between 0.35 and 0.55 mm below the contact surface.

       The metal in the needle bearing area first undergoes plastic deformation under the action of the maximum shear stress. If the contact stress is greater than the contact fatigue limit of the material, as the number of stress cycles increases, plastic deformation will continue to undergo plastic deformation, and due to plastic deformation, fatigue cracks will not appear here.

      Under normal conditions, micro-cracks form an angle of approximately 45° on the surface. The fatigue spalling crack on the contact track of needle roller bearing gradually expands under the action of repeated stress, and usually develops along the internal structure and composition of the material and the area where the stress distribution is uneven, until it extends to the surface and fractures from the root of the crack to form fatigue Flaking.