1. Common damage to crankshafts Common forms of damage to crankshafts are: journal wear, bending deformation and cracks. (1) Wear of the journal. The wear of the crankshaft main journal and connecting rod journal is uneven, and the wear part has a certain regularity. (2) The bending and twisting deformation of the crankshaft. The so-called crankshaft bending refers to the coaxiality error of the spindle journal that is greater than 0.05mm. If the connecting rod journal partition angle error is greater than 0 degrees 30 minutes, it is called crankshaft distortion. (3) Break of the crankshaft. Cracks in crankshafts occur at the transition rounds between the crank and the journal and at the oil holes. 2. Crankshaft overhaul The inspection of the crankshaft mainly includes the inspection of cracks, the inspection of deformation and the inspection of wear. (1) Crack maintenance. After the crankshaft is cleaned, it should first be checked for cracks. Crack testing can be performed with a magnetic flaw detector or a stained permeate agent. If the crankshaft is tested for cracks, it should generally be scrapped and replaced. (2) Maintenance of crankshaft bending. The test bending deformation should be based on the common axis of the spindle journal at both ends, and the radial circular runout error of the middle spindle journal should be checked. During the inspection, the spindle journals at both ends of the crankshaft are placed on the V-shaped block of the test plate, the dial gauge contacts are placed vertically against the intermediate spindle journals, and the crankshaft is slowly rotated, and the maximum pendulum difference shown by the dial gauge pointer, that is, the radial circle runout error value of the intermediate spindle journal, if it is greater than 0.15mm, the pressure correction should be carried out. Below this limit, it can be corrected in conjunction with the grinding spindle journal. The correction of the bending deformation of the crankshaft can generally be adjusted by cold pressing or percussion correction. Cold pressing calibration is to frame the crankshaft with V-shaped iron on both ends of the main shaft journal, and use the hydraulic press to press along the crankshaft bending in the opposite direction. Due to the elastic effect of the steel crankshaft, the amount of bending should be 10 to 15 times the amount of curvature of the crankshaft, and maintained for 2min to 4min, in order to reduce the elastic after-effect effect, it is best to use artificial aging method to eliminate. Artificial aging treatment, that is, after cold pressing, the crankshaft is heated to 573K ~ 773K, and the heat preservation is O.5h ~ 1h, which can eliminate the internal stress generated by cold pressing. (3) Maintenance of crankshaft distortion and deformation. The test of crankshaft distortion is to turn the connecting rod journal to the horizontal position, and use a percentile to determine the height difference between the two journals in the same direction. This height difference is the amount of distortion. Slight twisting deformation of the crankshaft can be corrected directly on the crankshaft grinding machine when grinding the connecting rod journal. The correction of the distortion of the crankshaft can be adjusted using the hydraulic wrench twist correction method. (4) Crankshaft journal wear maintenance. For crankshafts that are allowed to be repaired by flaw detection, the amount of wear on the shaft journal must be checked: the journal is first checked for wear marks and damage, and then the roundness error and cylindrical error of the main journal and connecting rod journal are measured. The wear of the crankshaft short journal is mainly to check the roundness error, and the long journal must check the roundness and cylindrical degree error.