Reasons for Failure of Machine Parts and Repair Methods
Mechanical failures and machine parts failures are inseparable. The failure of key components will cause equipment accidents. Therefore, we must pay enough attention to the failures of mechanical machine parts. The following are the reasons for the failure of machine parts and the repair methods to deal with them.
Failure of machine parts
1. Part wear and tear is the most important and common form of part failure.
2. Deformation of machine parts During the working process of the machine, the phenomenon that the size and shape of the machine parts change due to the action of the force is called deformation. Metal deformation includes elastic deformation and plastic deformation.
3. Fracture of machine basic parts Under the action of external force, the machine parts first undergo elastic deformation. When the stress caused by the load exceeds the elastic limit and continues to increase, the material may undergo plastic deformation, and finally, fracture occurs when the stress exceeds the strength limit.
4. The punctate peeling on the surface of the corroded part under the action of cyclic contact stress is called fatigue pitting; the damage to the surface metal of the part by the chemical and electrochemical action of the surrounding medium is called corrosion; needle-shaped holes are formed on the lower surface, and they are constantly expanding called cavitation. Fatigue pitting, corrosion, and cavitation are collectively referred to as corrosion.
Repair method
1. Repair methods that mainly restore the nature of cooperation
(1) The adjustment method generally uses adjusting the bolt tightness or adjusting the thickness of the gasket to restore the original matching relationship of the mating parts of the machine. When repairing, there is no need to process the mating machine parts (or only scrape), but only add gaskets or adjustments. The thickness of the gasket is used to restore the original mating clearance.
(2) Repair size method. When repairing, the more expensive machine parts in the mating machine parts are processed to restore their geometric shapes, and the new size is obtained at the same time, and then another worn part in the mating machine parts is discarded and replaced with a new one. The machine replacement machine parts that are matched with the processed machine parts can restore the matching clearance of the matching machine parts to the initial clearance, such as repairing the shaft and replacing the bearing bush, repairing the cylinder liner, and replacing the piston, etc. This repair method should consider the possibility of machining machine parts and the allowable mechanical strength after machine parts repair. Under this premise, the number of repairs should be increased as much as possible; on the other hand, in order to facilitate the supply of spare machine parts, the repair size should be standardized.
(3) Supplementary machine basic parts method (additional machine parts method) This method is to process and shape each part of the mating part, and give a reasonable diameter reduction or expansion to one of the machine parts, and then add a similar material or quality The high bushing is press-fitted or screwed or welded to the original part by interference, and then processed to the matching size, so that the matching properties can meet the requirements.
2. Repair method that restores not only the nature of fit but also the shape and size of machine parts
Welding repair method Metal welding is to uses the diffusion and connection between atoms to firmly combine the separated metal weldments into a whole. Depending on the welding equipment, welding includes gas welding and electric welding, and most of the broken and worn machine parts are repaired and repaired. For the repaired by surfacing method, some machine parts are processed by turning and grinding after welding to restore the original geometric shape and size.
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