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Henan Friend Metal Products Co.,Ltd

Several Factors Affecting Spring Fatigue Strength

1. In order to improve the fatigue strength of the spring, the yield strength of the spring material should be improved, and the yield strength of the material should be improved. Or the use of yield strength and tensile strength ratio of high material. For the same material, the fine grain structure has a higher yield strength than the grain structure.

2. The maximum stress on the surface state occurs in the surface of the spring material, so the surface quality of the spring has a great influence on the fatigue strength. Springs in the rolling, drawing and rolling process caused by cracks, defects and scars and other defects are often caused by spring fatigue fracture reasons.

The smaller the surface roughness of the material, the smaller the stress concentration, the higher the fatigue strength. Effect of Surface Roughness on Fatigue Limit. As the surface roughness increases, the fatigue limit decreases. In the case of the same roughness, the degree of fatigue limit of the different steel grades and the different rolling methods is also different, as the cold spring is less than the hot coil spring. Because the steel hot coil spring and its heat treatment heating, due to oxidation of the spring material surface rough and produce decarburization phenomenon, thus reducing the fatigue strength of the spring.

The surface of the material grinding, pressure, shot blasting and rolling and so on. Can improve the fatigue strength of the spring.

3. The greater the size of the size effect material, the greater the likelihood of defects due to the various cold working and thermal processing processes, and the greater the likelihood of surface defects, which can lead to a decrease in fatigue performance. Therefore, the effect of the size effect is taken into account when calculating the fatigue strength of the spring.

4. Metallurgical defects Metallurgical defects refer to non-metallic inclusions, bubbles, segregation of elements in materials, and so on. The inclusions present on the surface are stress concentration sources that can cause premature fatigue cracks between the inclusions and the matrix interface. Vacuum smelting, vacuum casting and other measures, can greatly improve the quality of steel.

5. Corrosion media spring in the corrosive medium work, due to the surface of the pitting or surface grain boundary corrosion and become a source of fatigue, under the effect of stress will gradually expand and lead to fracture. For example, spring steel working in fresh water, the fatigue limit is only 10% to 25% of the air. The effect of corrosion on the fatigue strength of the spring is related not only to the number of times the spring is subjected to the variable load, but also to the working life. Therefore, when calculating the spring affected by corrosion, the working life should be taken into account.

In the case of corrosion under the conditions of the spring, in order to ensure its fatigue strength, can use high corrosion resistance materials, such as stainless steel, non-ferrous metal, or surface plus protective layer, such as coating, oxidation, spray, paint and so on. Practice shows that cadmium can greatly improve the fatigue limit of the spring.

6. The fatigue strength of the temperature carbon steel decreases from room temperature to 120 ° C, from 120 ° C to 350 ° C, and rises above 350 ° C. There is no fatigue limit at high temperatures. In the high temperature conditions of the work of the spring, to consider the use of heat-resistant steel. At room temperature below room temperature, the fatigue limit of steel has increased.

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