Since the traditional Miner rule ignores the influence of the load sequence on the fatigue life, the fuzzy rules are used to analyze the fuzziness of the fatigue damage caused by the stress nearby the fatigue limit un...Since the traditional Miner rule ignores the influence of the load sequence on the fatigue life, the fuzzy rules are used to analyze the fuzziness of the fatigue damage caused by the stress nearby the fatigue limit under different load sequences. The improved fuzzy Miner rule can reflect the influence of the load sequence on the fatigue life. Results of the example show that the prediction error can be reduced from 61.6% to 21.7%.展开更多
The riverbank soil is a natural purifying agent for the polluted river water(Riverbank filtration, RBF). This is of great importance to groundwater safety along the riverbank. This paper examines the migration and tra...The riverbank soil is a natural purifying agent for the polluted river water(Riverbank filtration, RBF). This is of great importance to groundwater safety along the riverbank. This paper examines the migration and transformation rules of ammonia-nitrogen in three typical types of sand soil using the indoor leaching experiment of soil column, and then makes comparison with the indoor experiment results in combination with the numerical simulation method. The experiment process shows that the change in ammonia-nitrogen concentration goes through three stages including "removal-water saturation-saturation". As the contents of clay particles in soil sample increase, the removal of ammonia-nitrogen from soil sample will take more time and gain higher ratio. During the removal period, the removal ratio of Column 1, Column 2 and Column 3 averages 68.8%(1-12 d), 74.6%(1-22 d) and 91.1%(1-26 d). The ammonia-nitrogen removal ratio shows no noticeable change as the depth of soil columns varies. But it is found that the ammonia-nitrogen removal ratio is the least of the whole experiment when the soil columns are at the depth of 15 cm. It can be preliminary inferred that the natural purifying performance of soil along the river for ammonia-nitrogen in river water mainly depends on the proportion of fine particles in soil. HYDRUS-1D model is used to simulate this experiment process, analyze the change of the bottom observation holes by time and depth in three columns(the tenth day), and make comparison with the experiment result. The coefficients of determination for fitting curves of Column 1, Column 2 and Column 3 are 0.953, 0.909, 0.882 and 0.955, 0.740, 0.980 separately. Besides, this paper examines the contribution of absorption, mineralization and nitrification in the simulation process. In the early removal stage, mineralization plays a dominant role and the maximum contribution rate of mineralization is 99%. As time goes by, absorption starts to function and gradually assumes a dominant position. In the middle and late removal stage, nitrification in Column 1 and Column 2 makes more contribution than mineralization. So the experiment result of the ammonia-nitrogen concentration is 0.6% and 2.4% lower than that in effluent and the maximum contribution ratio of nitrification is -4.53% and -5.10% respectively when only the function of absorption is considered. The mineralization in Column 1 and Column 2 in the middle and late removal stage still plays a more important role than nitrification. So the experiment result is 1.4% higher than that in effluent and the maximum contribution ratio of nitrification is -2.51% when only the function of absorption is considered. Therefore, absorption, mineralization and nitrification make different contributions during different part of the stage. This means that the natural purifying performance of soil along the river for ammonia-nitrogen in river water not only depends on the proportion of fine particles in soil, but depends on the mineralization and nitrification environment. This can offer some insights into the protection and recovery of groundwater along the riverbank.展开更多
First of all, the concept of γ_p_S a_S m_N (confidence level_reliability_stress amplitude_stress mean_fatigue life) surface is presented. Then the formulas of p_S a_S m_N surface and γ_p_S a_S m_N ...First of all, the concept of γ_p_S a_S m_N (confidence level_reliability_stress amplitude_stress mean_fatigue life) surface is presented. Then the formulas of p_S a_S m_N surface and γ_p_S a_S m_N surface are derived. In addition, fatigue strength distribution function and two_dimensional reliability Miner rule are obtained. At last, an example is given.展开更多
Firstly, constant amplitude P-S_a-S_m-N_c surface family is established.Secondly, four basic assumptions, i.e., monotonically increasing, non-coupling, separability andnonintersecting of fatigue damage accumulation ar...Firstly, constant amplitude P-S_a-S_m-N_c surface family is established.Secondly, four basic assumptions, i.e., monotonically increasing, non-coupling, separability andnonintersecting of fatigue damage accumulation are proposed from the viewpoint of both damagemechanics and fracture mechanics. Then the individual isodamage D-S_a-S_m-N surface under constantamplitude loading is constructed and the two-dimensional individual Miner's rule is derived.Consequently, the two-dimensional probabilistic Miner's rule (TPMiner) is established and proved fora population subjected to variable amplitude loading. Finally, with successfully experimentverification, TPMiner proves be to very useful and feasible in fatigue reliability theory.展开更多
Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic load...Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.展开更多
基金the National Natural Science Foundation of China(60472118)~~
文摘Since the traditional Miner rule ignores the influence of the load sequence on the fatigue life, the fuzzy rules are used to analyze the fuzziness of the fatigue damage caused by the stress nearby the fatigue limit under different load sequences. The improved fuzzy Miner rule can reflect the influence of the load sequence on the fatigue life. Results of the example show that the prediction error can be reduced from 61.6% to 21.7%.
基金supported by Special Scientific Research Expenditure for Public Charity Industry of Ministry of Water Resources(No.201501008)Institute of Resources and Environment of North China University of Water Resources and Electric Power
文摘The riverbank soil is a natural purifying agent for the polluted river water(Riverbank filtration, RBF). This is of great importance to groundwater safety along the riverbank. This paper examines the migration and transformation rules of ammonia-nitrogen in three typical types of sand soil using the indoor leaching experiment of soil column, and then makes comparison with the indoor experiment results in combination with the numerical simulation method. The experiment process shows that the change in ammonia-nitrogen concentration goes through three stages including "removal-water saturation-saturation". As the contents of clay particles in soil sample increase, the removal of ammonia-nitrogen from soil sample will take more time and gain higher ratio. During the removal period, the removal ratio of Column 1, Column 2 and Column 3 averages 68.8%(1-12 d), 74.6%(1-22 d) and 91.1%(1-26 d). The ammonia-nitrogen removal ratio shows no noticeable change as the depth of soil columns varies. But it is found that the ammonia-nitrogen removal ratio is the least of the whole experiment when the soil columns are at the depth of 15 cm. It can be preliminary inferred that the natural purifying performance of soil along the river for ammonia-nitrogen in river water mainly depends on the proportion of fine particles in soil. HYDRUS-1D model is used to simulate this experiment process, analyze the change of the bottom observation holes by time and depth in three columns(the tenth day), and make comparison with the experiment result. The coefficients of determination for fitting curves of Column 1, Column 2 and Column 3 are 0.953, 0.909, 0.882 and 0.955, 0.740, 0.980 separately. Besides, this paper examines the contribution of absorption, mineralization and nitrification in the simulation process. In the early removal stage, mineralization plays a dominant role and the maximum contribution rate of mineralization is 99%. As time goes by, absorption starts to function and gradually assumes a dominant position. In the middle and late removal stage, nitrification in Column 1 and Column 2 makes more contribution than mineralization. So the experiment result of the ammonia-nitrogen concentration is 0.6% and 2.4% lower than that in effluent and the maximum contribution ratio of nitrification is -4.53% and -5.10% respectively when only the function of absorption is considered. The mineralization in Column 1 and Column 2 in the middle and late removal stage still plays a more important role than nitrification. So the experiment result is 1.4% higher than that in effluent and the maximum contribution ratio of nitrification is -2.51% when only the function of absorption is considered. Therefore, absorption, mineralization and nitrification make different contributions during different part of the stage. This means that the natural purifying performance of soil along the river for ammonia-nitrogen in river water not only depends on the proportion of fine particles in soil, but depends on the mineralization and nitrification environment. This can offer some insights into the protection and recovery of groundwater along the riverbank.
文摘First of all, the concept of γ_p_S a_S m_N (confidence level_reliability_stress amplitude_stress mean_fatigue life) surface is presented. Then the formulas of p_S a_S m_N surface and γ_p_S a_S m_N surface are derived. In addition, fatigue strength distribution function and two_dimensional reliability Miner rule are obtained. At last, an example is given.
基金This project is supported by National Natural Science Foundation of China(No.59605010,No.59979015)Selected from Proceedings of 2000 the First International Conference on Mechanical Engineering
文摘Firstly, constant amplitude P-S_a-S_m-N_c surface family is established.Secondly, four basic assumptions, i.e., monotonically increasing, non-coupling, separability andnonintersecting of fatigue damage accumulation are proposed from the viewpoint of both damagemechanics and fracture mechanics. Then the individual isodamage D-S_a-S_m-N surface under constantamplitude loading is constructed and the two-dimensional individual Miner's rule is derived.Consequently, the two-dimensional probabilistic Miner's rule (TPMiner) is established and proved fora population subjected to variable amplitude loading. Finally, with successfully experimentverification, TPMiner proves be to very useful and feasible in fatigue reliability theory.
基金supported by the National Natural Science Foundation of China(No.10377007)
文摘Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.
