Restoration of deformed ship crankshafts by straightening

The article focuses on studying the crankshaft as an essential part of the marine internal combustion engine. Typical defects of crankshafts of marine diesel engines are considered. The loads causing the curvature of a crankshaft axis under operating conditions are indicated. The causes and nature of violation of the shaft axis geometry are determined. The statistical assessment in the cases of axle warping during diesel operation is found necessary. The recommendations of the Russian Maritime Register of Shipping on eliminating the curvature of the shaft axis are considered. A long-term practical experience of straightening crankshafts at the ship repair plants is taken into account. Methods for eliminating shaft deflections under repair conditions are described. Methods of mechanical straightening without heating are considered. The advantages and disadvantages of mechanical methods of shaft straightening are clarified. The conditions and necessary requirements for thermomechanical shafts straightening are described. The conditions for applying the thermal method of straightening ship shafts are substantiated. High labor intensity and instability of a shaft shape after straightening are pointed out. There has been proposed method of straightening crankshafts of marine internal combustion engines by stress relaxation based on the creep of the shaft material. Theoretical foundations of the processes of creep and stress relaxation in the shaft material are considered. There has been inferred a necessity of further research of operational reliability of crankshafts of marine internal combustion engines after their restoration by the stress relaxation method.