Researcher Li Shouxin of the Engineering Materials Fatigue Research Group of the Materials Fatigue and Fracture Research Department of the Institute of Materials Science and Technology, Shenyang National Institute of Materials Science, Chinese Academy of Sciences and others, after 10 years of hard work, has made certain achievements in the study of the impact of inclusions on the ultra-high cycle fatigue behavior of high-strength steel progress. They studied the strength of non-metallic inclusions (mainly hard and brittle oxide inclusions) to fatigue strength under the condition of ultra-high cycle fatigue (spring cycle is generally 107-109 weeks) under high-strength steel such as spring steel and bearing steel. , Fatigue life and the effect of the SN curve (stress-life curve), and the effect of hydrogen content on fatigue behavior. Recently, Researcher Li Shouxin was invited to publish the English review article Effects of inclusions on the very high cycle fatigue properties of high strength steels on International Materials Reviews (57 (2012) 92-114). Researchers first studied the critical inclusion size. Large-size inclusions are very harmful to fatigue, while small-size inclusions are very small to fatigue, and even have a beneficial effect on certain mechanical properties. Understanding and mastering critical dimensions is conducive to quality control of steel. Therefore, for some high-strength steels, in the case of high-cycle fatigue (the number of stress cycles is generally 105-107 weeks), the critical size of inclusions is about 6-10 microns. In the case of ultra-high-cycle fatigue (the number of stress cycles is generally 107-109 weeks), the critical size of inclusions is about 3-5 microns. In addition, the critical inclusion size tends to be smaller with increasing strength. The study found that the ultra-high cycle fatigue strength σw and fatigue life Nf decrease with the increase of the inclusion size D, and their dependencies can be expressed as: In the formula, n1 ～ 0.17-0.19, n2 ～ 4.3-8.4. At present, the size of the inclusions that cause fatigue cracking on fatigue fractures of some commercial high-strength steels averages about 20 microns. If the smelting level is improved, the size of the inclusions on the corresponding fractures will be reduced by half on average to about 10 microns. It can be expected that the fatigue strength will increase by 10 %, The fatigue life is increased by 100 times (in expression (1), it is estimated by n1 = 0.17, n2 = 6.5). This prediction is also consistent with the experimental results, which also shows that the fatigue life is more sensitive to the size of inclusions. Therefore, for high-quality high-strength steels, controlling the size of inclusions is very important to improve the reliability against fatigue damage. Researchers also conducted research on how different hydrogen content in high-strength steel and different inclusion sizes affect ultra-high cycle fatigue performance. Let σw represent the fatigue strength of high-strength steel with very low hydrogen content, σ * w is the fatigue strength of high-strength steel after it has been hydrogen-charged, and λ is the influence factor of hydrogen on fatigue The expression obtained by experiment is: In the formula, CH is the hydrogen content (ppm). Experiments show that the hydrogen content above 1ppm will significantly affect the fatigue strength. When the hydrogen content is 2ppm, the fatigue strength may drop to 70% of the original. In addition, researchers also conducted in-depth research on how the size of inclusions affects the shape of the SN curve of high-strength steel and the mechanism of inclusions in high-strength steel as the origin of fatigue. Since the inclusions at the origin of fatigue on the fatigue fracture are often the largest inclusions in the test volume under the maximum stress, if the size and hydrogen content of the largest inclusions in the steel are known, their fatigue performance can be predicted and evaluated. The statistical extreme value method and the generalized Poreto method can be used to predict the size of the largest inclusions in different volumes of steel based on the size of multiple inclusions observed on metallographic samples. With the support of the 973 project (G19980615 / G2004CB619100), the research team collaborated with the General Research Institute of Iron and Steel Research to obtain a comparatively systematic research result. influences". 2 Person Sound Proof Meeting Pod 2 Person Sound Proof Meeting Pod,soundproof pods office,office phone booth Feat Top International(China) CO.,LTD , https://www.lounge-seating.com
