| Components in the process of use, supported by a complex function of alternating loads, often causing fatigue damage. At present, the design of fatigue life has been in the air, machinery, traffic, and in the field of Ocean Engineering Research, get in-depth study and application. However, there are mang factors affecting the fatigue life, which caused a great deal of the error for the life assessment.The impact of fatigue loading sequence is an important factor in life, therefore, a explicitly effect of loading sequence is of great significance.This paper reviews the history of fatigue, discusses the loading sequence effect on fatigue life of dynamic, while rain flow counting method using random load-time course of processing, the preparation of the three load spectrum, the fatigue testing machine by low-high, high-low load sequence by two different specimen fatigue life, and with the specimen under random load fatigue life compared to study the fatigue life distribution, analysis of different loading sequence on fatigue life of, and the reasons for causing such effects. Test found that under the high load-low load sequence, the fatigue life compared with the random fatigue life significantly decreased, while the low load-the order of fatigue life under high load and random fatigue life is reduced compared to, but with than high-low load, the fatigue life of smaller lesser extent, indicating that the two samples under different loading order of the damage caused is different, high-low load of damage under the larger. Analyze the reasons is because the first thing that caused the high load reduces the fatigue strength of materials, to accelerate the subsequent damage caused by the small load. |
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