A novel forging process of 6082 aluminum alloy is proposed, which can save time and reduce energy consumption while ensuring mechanical properties. In this process, the billet was preforged at solid solution temperatu...A novel forging process of 6082 aluminum alloy is proposed, which can save time and reduce energy consumption while ensuring mechanical properties. In this process, the billet was preforged at solid solution temperature and then preaged, followed by warm forging at 200 ℃. The flow behavior of the preaged samples during compression and the mechanical properties of the formed samples were investigated by hot compression tests. The differences in the precipitated phases of the samples with different processing parameters were analyzed by scanning electron microscopy(SEM), transmission electron microscopy(TEM), and differential scanning calorimetry(DSC). The best comprehensive performance was obtained after preaging at 120 ℃ for 4 h and holding at 200 ℃ for 10 min, and the Vickers hardness was HV 128, which was higher than that of the traditional process. Precipitation strengthening and dislocation strengthening were improved when the samples were formed at 200 ℃. This forging process shows the advantages of short time consumption and low energy consumption, which can effectively improve the production efficiency while ensuring the strength after forming.展开更多
In order to eliminate the settlement underestimation in surcharge preload engineering, a study based on Bjerrum's creep diagram and the tangent slope definition of secondary consolidation coefficient was carried o...In order to eliminate the settlement underestimation in surcharge preload engineering, a study based on Bjerrum's creep diagram and the tangent slope definition of secondary consolidation coefficient was carried out to analyze the time effect of secondary consolidation coefficient of over consolidated soil, and a time–growth model for it was formulated. As Bjerrum's creep diagram is an idealized model, oedometer tests were performed to improve the above time–growth model of secondary consolidation coefficient for the purpose of achieving a better agreement with the actual ground situations. It is found that secondary consolidation coefficient of over consolidated soil not only decreases with the ratio of historical maximum to current effective stress of soil(OCR), but also increases with the development time of secondary consolidation. No matter how large OCR is, the long-term time effect of secondary consolidation coefficient of over consolidated soil is all significant. Based on the above results, a model for settlement estimation was formulated and a case study to estimate it indicates that the settlement estimated by our method is 2–5 times larger than that estimated by the previous method. Moreover, the larger the OCR is as well as the longer the service life is, the larger the difference between our method and the previous method is. Thus, the post-construction secondary settlement in surcharge preload engineering will be underestimated when neglecting the time effect of secondary consolidation coefficient in over consolidated state.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 51775397, 52075400)“111” Project of China (No. B17034)+1 种基金the Major Program of Science and Technology Program of Hubei Province, China (Nos. 2019AAA007, 2020BAB140)the Innovative Research Team Development Program of Ministry of Education of China (No. IRT17R83)。
文摘A novel forging process of 6082 aluminum alloy is proposed, which can save time and reduce energy consumption while ensuring mechanical properties. In this process, the billet was preforged at solid solution temperature and then preaged, followed by warm forging at 200 ℃. The flow behavior of the preaged samples during compression and the mechanical properties of the formed samples were investigated by hot compression tests. The differences in the precipitated phases of the samples with different processing parameters were analyzed by scanning electron microscopy(SEM), transmission electron microscopy(TEM), and differential scanning calorimetry(DSC). The best comprehensive performance was obtained after preaging at 120 ℃ for 4 h and holding at 200 ℃ for 10 min, and the Vickers hardness was HV 128, which was higher than that of the traditional process. Precipitation strengthening and dislocation strengthening were improved when the samples were formed at 200 ℃. This forging process shows the advantages of short time consumption and low energy consumption, which can effectively improve the production efficiency while ensuring the strength after forming.
基金Project(51178419)supported by the National Natural Science Foundation of China
文摘In order to eliminate the settlement underestimation in surcharge preload engineering, a study based on Bjerrum's creep diagram and the tangent slope definition of secondary consolidation coefficient was carried out to analyze the time effect of secondary consolidation coefficient of over consolidated soil, and a time–growth model for it was formulated. As Bjerrum's creep diagram is an idealized model, oedometer tests were performed to improve the above time–growth model of secondary consolidation coefficient for the purpose of achieving a better agreement with the actual ground situations. It is found that secondary consolidation coefficient of over consolidated soil not only decreases with the ratio of historical maximum to current effective stress of soil(OCR), but also increases with the development time of secondary consolidation. No matter how large OCR is, the long-term time effect of secondary consolidation coefficient of over consolidated soil is all significant. Based on the above results, a model for settlement estimation was formulated and a case study to estimate it indicates that the settlement estimated by our method is 2–5 times larger than that estimated by the previous method. Moreover, the larger the OCR is as well as the longer the service life is, the larger the difference between our method and the previous method is. Thus, the post-construction secondary settlement in surcharge preload engineering will be underestimated when neglecting the time effect of secondary consolidation coefficient in over consolidated state.
