An increase in the circle was also found on another automobile production assembly line. Since the 1990s, the 704 in one hospital has repeatedly found the phenomenon of rising circles, and it is difficult to apply the specified mounting torque, which has not been well solved. The spring washers used in these examples are spring steel (65Mn or 70 gauge steel). In 1998, the space system changed to stainless steel spring washers according to the requirements of the Aerospace Corporation. At the same time, people may also wish to carry out research work on standardization topics in the following aspects: a1 Benefit evaluation of aerospace standardization work (including social and economic benefits), as currently The evaluation of the benefits of the standards is often focused on economic benefits and operability is poor; at the same time, it is not fair to evaluate aerospace standardization work (or other standardization work) only from economic benefits.
The b1 space system promotes the standardization work of CIMS (Computer Integrated Manufacturing System). For example, establish a CIMS standard system for the aerospace industry, and combine the characteristics of aerospace products to develop corresponding standards or guiding technical documents. C1 other standardization research topics.
In the final assembly, the standard spring stainless steel spring washer (QJ296312) was used to replace the spring steel light spring washer (GB859) used in the past. The intuitive reason is that the assembly precision is too low, the flat washer material is too soft, and the substitution relationship is not accurate. Afterwards, the light stainless steel spring washer (QJ296313) is used, and the problem is temporarily solved (the essence is that the contradiction is covered), and the product is shipped.
In summary of the above-mentioned upswing phenomenon, it is not difficult to see that all the rising circles occur under the condition of applying a large installation torque; both the light spring washer and the standard spring washer may rise; the ring-up phenomenon may occur in the stainless steel spring. On the washer, it is also possible to occur on the spring steel spring washer; the occurrence of the ring is often accompanied by phenomena such as low assembly precision, improper selection of the flat washer or nut, and the problem is difficult to return to zero. These are very instructive for us to analyze the real reason for the spring washer ring.
Mechanism analysis of the rise circle Theoretically, the spring washer should only be subjected to axial pressure during assembly. However, very few spring washers start to rise outward after applying a sufficiently large pre-tightening torque, indicating that the spring washer must be subjected to radial external tension during the tightening of the nut, so where does this external tension come from? To clarify this problem, let us first analyze the assembly process of the spring washer.
The ideal assembly process assumes that the spring washers, flat washers, bolts, etc. are in a centered position relative to the bolt mounting holes. The assembly process is roughly divided into three stages: In the first stage, the spring washer is gradually flattened with the rotation of the nut. During this process, the spring washer is gradually increased in force, and reaches about half of the elastic test load when flattened.
In the second stage, the torque is applied to the nut until the resulting preload force reaches the elastic test load value of the spring washer. In the third stage, a greater torque is applied to the nut until the pre-tightening torque required by the design. In the first two stages, the nut and the washer are very small, and they can be seen as rigid bodies. At this time, in addition to the vertical pressure exerted by the nut and the flat washer, the spring washer is also subjected to the tangential friction force F applied by the bearing facing the spring washer slit rib when the nut is rotated right. Under the action of F, the spring washer is not only impossible to open, but will make the two end faces closer together, even fit (m = 0). The ideal assembly of the spring pad is tightened to the third stage of the initial spring cushion, and the situation changes qualitatively.
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