| SU Yan,ZHONG Yong,SU Hong,WANG Cheng-zhang,WU Shuai.Influence of Natural Environment-Fatigue Alternate Action on Accumulated Damage of 2024 Typical Connection Structure[J],49(10):268-275 |
| Influence of Natural Environment-Fatigue Alternate Action on Accumulated Damage of 2024 Typical Connection Structure |
| Received:June 15, 2020 Revised:October 20, 2020 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2020.10.031 |
| KeyWord:connection structure environmental corrosion fatigue alternate action damage rule damage mechanism |
| Author | Institution |
| SU Yan |
Southwest Institute of Technology and Engineering, Chongqing , China |
| ZHONG Yong |
Southwest Institute of Technology and Engineering, Chongqing , China |
| SU Hong |
Southwest Institute of Technology and Engineering, Chongqing , China |
| WANG Cheng-zhang |
Southwest Institute of Technology and Engineering, Chongqing , China |
| WU Shuai |
Southwest Institute of Technology and Engineering, Chongqing , China |
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| Abstract: |
| The work aims to exhibit the environmental damage rule and damage mechanism of 2024 typical connection structure under the alternate action of natural environment and fatigue. Static natural exposure test and static natural environment-fatigue alternate test were used to comparatively study the accumulated damage characteristics and fatigue degradation rule of 2024 typical connection structure. Electro-liquid servo material test machine was applied to test the fatigue life of samples for different cycles. Environmental SEM and optical microscopy were adopted to observe and characterize the morphology and micro corrosion characteristics of sample fatigue fracture. The X-ray stress analyzer was employed to measure the change of residue stress at hole edge by periodical stress. Metallographic results showed that periodical fatigue stress had certain accelerating effects on corrosion damage of 2024 typical connection structure, and the corrosion depth (51.9 μm) under alternate condition for 2 years was larger than that (47.0 μm) in static exposure condition. Median fatigue life curve showed that the samples with the same environmental corrosion conditions in static exposure test had longer fatigue life than that in “fatigue + static exposure” alternate condition. The median fatigue life of samples without coating was about 1.5~2.3 times that in alternate test, and that of coated samples was about 1.1~1.4 times that in alternate test. The test data of residual stress around the fastening hole showed that the residual compressive stress at the edge of the hole gradually decreased due to the superposition of external alternate stress and environmental corrosion, resulting in local plastic deformation, which adversely affected the fatigue life. Under the condition of “fatigue+static exposure” alternate test, the fatigue life degradation of samples is closely related to the competition between low load exercise effect and electrochemical effect, the change of residual compressive stress at the hole edge and fretting wear, thus showing a trend of first increasing and then slightly oscillating and decreasing. |
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