Fatigue crack propagation is one of the common problems in the long time use of ship port machinery forgings. Because there may be various defects in the manufacturing, assembly and use of mechanical forgings, such as uneven materials, improper heat treatment, stress concentration, etc., these defects will become the source of the germination and expansion of fatigue cracks. When the fatigue crack extends to a certain extent, it will have a serious impact on the performance and safety of the forging, and may even lead to major accidents.
The basic principle of fatigue crack propagation is that under the action of cyclic load, the local defects or stress concentration areas in the forging will produce small cracks. With the continuous action of cyclic load, the micro crack will gradually expand and eventually form a macro crack. When the macroscopic crack reaches a certain length, it will affect the structural stability and integrity of the forging, and then lead to the failure or destruction of the forging.
Ship port mechanical forgings have the following characteristics in terms of fatigue crack propagation:
Withstand alternating loads: The ship will be subjected to various alternating loads during navigation, such as wind waves, currents, earthquakes, etc. These alternating loads can easily lead to fatigue cracks in forgings.
Corrosive environment: Port mechanical forgings are usually in a high humidity, salty environment, these environmental factors will accelerate the corrosion of forgings and fatigue crack growth.
High temperature and high pressure: ships will encounter high temperature and high pressure environment during navigation, these factors will affect the mechanical properties of forgings and fatigue crack growth.
In order to solve the problem of fatigue crack propagation of ship port mechanical forgings, the following prevention measures can be taken:
Optimization design: Optimize the structural design of forgings to avoid stress concentration and local overload. At the same time, the mechanical properties and environmental adaptability of the material should be considered to reduce the risk of fatigue crack propagation.
Strict control of the manufacturing process: in the forging and heat treatment process, it is necessary to strictly control the process parameters and material quality to avoid problems such as uneven materials and improper heat treatment. At the same time, non-destructive testing should be carried out to ensure the quality and integrity of the forging.
Strengthening protective measures: In view of corrosion environment and high temperature and high pressure and other factors, protective measures such as coating and shot peening can be applied to the surface of the forging to improve the corrosion resistance and fatigue resistance of the forging.
Regular inspection and maintenance: Regular inspection and maintenance of ship port machinery forgings, timely discovery and treatment of existing defects such as fatigue cracks, in order to avoid serious consequences caused by crack expansion.
Fatigue crack propagation of mechanical forgings in ship harbors is one of the important problems affecting its service life and safety performance. In order to prevent fatigue crack propagation, it is necessary to improve the quality and reliability of forgings from the aspects of structural design, manufacturing process, protective measures and regular inspection. In the actual use process, the monitoring and maintenance of forgings should be strengthened, and the existing defects such as fatigue cracks should be found and dealt with in time to ensure the safe and stable operation of the ship.
