Analysis and Improvement of the Fracture of the Anchor Bolt of the Air Compressor of the Technical Reconstruction Liu Wei ffP State Compressor General Plant, the fracture phenomenon of the body anchor bolt of the secondary cylinder of the 54500-force (8) air compressor in Guangxi Liuzhou is analyzed to determine the cause of the failure , improve the structure and solve the problem.
l Bow rumor air compressor has the characteristics of stable and reliable operation. It has been well received by users when it is put on the market. It has won the title of Guangxi Famous Brand and has been widely used in engineering. Insufficient, sometimes there will be breakage of the body anchor bolts in the secondary cylinder, see.
2 Reason analysis 2.1 The schematic diagram of the structural air compressor, the support of the inlet and exhaust bearings is rigid, that is, the four M24 screws are respectively supported on the steel parts, as shown.
When the machine is running, the exhaust support (secondary) is in a hot state, that is, thermal expansion occurs, and due to the rigid support, the expansion is constrained, and thermal stress is generated. As a result, additional loads are added to the anchor bolts.
2.2 Force analysis and calculation 2.2.1 Stress analysis The force of the compressor is very complicated. For the problem of anchor bolt breakage, it is better to analyze it. According to the material mechanics, the compressor can be regarded as the rigid beam of the frame. The anchor bolts at the fuselage and the middle body are simplified into fixed hinge supports. The inlet and exhaust bearings are simplified into movable hinge bearings. See the mechanical model. .
Since the anchor bolts in the body of the secondary cylinder are broken, we analyze the force situation here and regard it as a dangerous section of the rigid beam. When the compressor is running, the anchor bolts in the body of the secondary cylinder are subjected to the preload of the bolts, the working load and the additional load due to thermal expansion.
2.2.2 Calculation of the force of the anchor bolt (3) Pre-tightening force of the bolt The motion mechanism of the compressor is as shown.
The technical transformation of the compressor anchor bolt force reduces the torque received by the anchor bolt at the fuselage and the middle body of the unit, causing the bolt to be sheared. In order to prevent the connected parts from sliding relative to each other, the pre-tightening force of each bolt is the friction coefficient of the f-joining surface, and the working load of the anchor bolts at the center of 0.12 is the effect of comparing the torque and the tilting moment. Value, the pre-tightening force of the bolt required for the anchor bolt at the middle body is the rigid support structure of the exhaust support. As shown, the additional load is due to the temperature rise of the compressor during operation, causing thermal deformation, exhaust branch The rigid support at the seat cannot compensate for the thermal stress generated by the thermal deformation and is transmitted to the anchor bolt. The anchor bolt at the middle body must bear more additional load.
The material of the exhaust support is HT200, the coefficient of linear expansion is a=8.7x106(1/), the ambient temperature is 25 ft, the exhaust temperature is 160U, and the calculated temperature is 70, then the free heat deformation is adjusted at the exhaust support. The bolt is 4xM24, the material is 45, the rigidity is completely constrained according to the thermal deformation, then the additional force is pressed, and the torque is transmitted to the central axis of the compressor group. The moment of inertia is like: =11.9kNm, which is the ground of the compressor unit and the middle body. The tipping moment of the bolt. In order to ensure that the joint fits tightly and seamlessly, the minimum pre-tightening force of the required bolt is transmitted to the middle body of the two-stage cylinder, according to which the additional load on the anchor bolt is considered to be not completely affected by the thermal deformation. Constraint, according to 60% of the technical transformation, the thermal expansion generated during work can not be compensated to generate thermal stress, if the thermal stress can not be eliminated, the tensile stress reaching the simple limit will break the bolt.
3 Improved design From the above analysis, it can be seen that the thermal stress generated during the operation of the secondary cylinder is very harmful. From the calculation point of view, it is inevitable that the bolt is broken, but in reality, not all bolts are used for various reasons. They are all pulled off. But in any case, the thermal stress is very harmful. If you don't want to eliminate it, the consequences are very serious.
In order to compensate for the thermal deformation, it is necessary to improve the structure. As shown, the rigid support is changed to the elastic support, the thermal deformation is compensated, the thermal stress is greatly reduced, and the additional load is eliminated.
After the improvement, the strength check is performed, and the allowable stress is used. 4 After the improved design, the thermal deformation is compensated, and the D-100/7 type air compressor has no such problems, completely eliminating the phenomenon that the anchor bolt is broken.
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