The wear of crankshaft journal surface is not uniform, the radial wear of main shaft journal and connecting rod journal is mainly elliptical, and their maximum wear parts correspond to each other, that is, the maximum wear of each main shaft journal is close to one side of the connecting rod journal. The maximum wear of the connecting rod journal is also near the side of the spindle journal. The crankshaft journal also has conical wear along the axis.
The elliptical wear of the journal is caused by the uneven distribution of the forces acting on the journal along the circumference. When the engine is working, the comprehensive force of the connecting rod journal always acts on the inner side of the connecting rod journal, and the direction is outward along the radius of the crankshaft, resulting in the greatest wear on the inner side of the connecting rod journal, forming an oval shape. The reason for conical wear of the connecting rod journal is that the oil passage leading to the connecting rod journal is inclined. When the crankshaft rotates, under the action of centrifugal force, the mechanical impurities in the lubricating oil accumulate on one side of the connecting rod journal, accelerating the wear of the side journal and making the wear of the connecting rod journal conical. In addition, the connecting rod bending, cylinder center line and crankshaft center line is not vertical and other reasons, will make the journal along the axial force is uneven, and the wear is skewed.