Crack monitoring plays a great role in modern structural health monitoring, however, most of the conventional crack inspections have disadvantages in terms of the accuracy, expense, reliability, durability and level o...Crack monitoring plays a great role in modern structural health monitoring, however, most of the conventional crack inspections have disadvantages in terms of the accuracy, expense, reliability, durability and level of instrumentation required. Thus, development of a simple and reliable crack inspection technique that allows continuous monitoring has been desired. In this paper, electrical potential technique and modern surface technology are employed together to develop a new structural surface crack monitoring method. A special crack monitoring coating sensor based on electrical potential technique was deposited on the hot spot of the structure by modern surface technology. The sensor consists of three layers： the isolated layer, the sensing layer and the protective layer. The isolated layer is prepared by anodic oxidation technology, the sensing layer is made of ion plated copper, and the protective layer is made of silicone. The thickness of each layer is at micrometer magnitude. The electrical conductivity of the sensor is very stable, and the fatigue performance of the specimen with or without coating sensor is nearly unchanged. The crack monitoring experiment result shows that there are two sudden rises of the coating sensor electrical potential values, corresponding to different stages of the crack initiation and propagation. Since the width of the surface coating sensor is only 0.5 mm, this crack monitoring sensor can detect the propagation of cracks less than 0.5 mm long. The method proposed takes the simplicity of electrical potential technique and can monitor surface crack of nearly all kinds of structures precisely. The results of this paper may form the basis of a new crack monitoring system.展开更多
重点研究了薄板材料的非线性L em a iter-Chaboche塑性损伤模型参数的测试与标定方法.首先,利用大圆弧变截面拉伸试样检测不同塑性损伤状态下材料弹性模量的变化,进而换算得到材料单轴塑性损伤演化曲线,即ω(E)-εP曲线;然后,参照L em a...重点研究了薄板材料的非线性L em a iter-Chaboche塑性损伤模型参数的测试与标定方法.首先,利用大圆弧变截面拉伸试样检测不同塑性损伤状态下材料弹性模量的变化,进而换算得到材料单轴塑性损伤演化曲线,即ω(E)-εP曲线;然后,参照L em a iter-Chaboche塑性损伤模型中的非线性塑性损伤演化方程,拟定一个相关三参数幂指数函数作为目标函数,并采用了数值迭代-拟合方法确定拟合参数;最后标定出了材料的非线性塑性损伤模型参数.文中还就LY 12-CZ薄板材料的损伤与破坏行为进行了实验测试与分析.展开更多
The fatigue properties of laser shock processing （LSP） on both side surfaces of fastener hole with diameter of 3 mm in the LY12CZ aluminum alloy specimens were investigated. The superficial residual stress was measu...The fatigue properties of laser shock processing （LSP） on both side surfaces of fastener hole with diameter of 3 mm in the LY12CZ aluminum alloy specimens were investigated. The superficial residual stress was measured by X-ray diffraction method. Fatigue experiments of specimens with and without LSP were performed, and the microstructural features of fracture of specimens were characterized by scanning electron microscopy （SEM）. The results indicate that the compressive residual stress can be induced into the surface of specimen, and the fatigue life of the specimen with LSP is 3.5 times as long as that of specimen without LSP. The location of fatigue crack initiation is transferred from the top surface to the sub-surface after LSP, and the fatigue striation spacing of the treated specimen during the expanding fatigue crack is narrower than that of the untreated specimen. Furthermore, the diameters of the dimples on the fatigue crack rupture zone of the specimen with LSP are relatively bigger, which is related to the serious plastic deformation in the material with LSP.展开更多
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2009AA03Z103)Scientific Research Foundation for the Returned Overseas Chinese Scholars of Ministry of Education of China (Grant No. [2006]331)
文摘Crack monitoring plays a great role in modern structural health monitoring, however, most of the conventional crack inspections have disadvantages in terms of the accuracy, expense, reliability, durability and level of instrumentation required. Thus, development of a simple and reliable crack inspection technique that allows continuous monitoring has been desired. In this paper, electrical potential technique and modern surface technology are employed together to develop a new structural surface crack monitoring method. A special crack monitoring coating sensor based on electrical potential technique was deposited on the hot spot of the structure by modern surface technology. The sensor consists of three layers： the isolated layer, the sensing layer and the protective layer. The isolated layer is prepared by anodic oxidation technology, the sensing layer is made of ion plated copper, and the protective layer is made of silicone. The thickness of each layer is at micrometer magnitude. The electrical conductivity of the sensor is very stable, and the fatigue performance of the specimen with or without coating sensor is nearly unchanged. The crack monitoring experiment result shows that there are two sudden rises of the coating sensor electrical potential values, corresponding to different stages of the crack initiation and propagation. Since the width of the surface coating sensor is only 0.5 mm, this crack monitoring sensor can detect the propagation of cracks less than 0.5 mm long. The method proposed takes the simplicity of electrical potential technique and can monitor surface crack of nearly all kinds of structures precisely. The results of this paper may form the basis of a new crack monitoring system.
文摘重点研究了薄板材料的非线性L em a iter-Chaboche塑性损伤模型参数的测试与标定方法.首先,利用大圆弧变截面拉伸试样检测不同塑性损伤状态下材料弹性模量的变化,进而换算得到材料单轴塑性损伤演化曲线,即ω(E)-εP曲线;然后,参照L em a iter-Chaboche塑性损伤模型中的非线性塑性损伤演化方程,拟定一个相关三参数幂指数函数作为目标函数,并采用了数值迭代-拟合方法确定拟合参数;最后标定出了材料的非线性塑性损伤模型参数.文中还就LY 12-CZ薄板材料的损伤与破坏行为进行了实验测试与分析.
基金Project (51175002) supported by the National Natural Science Foundation of ChinaProject (090414156) supported by the Natural Science Foundation of Anhui Province,China
文摘The fatigue properties of laser shock processing （LSP） on both side surfaces of fastener hole with diameter of 3 mm in the LY12CZ aluminum alloy specimens were investigated. The superficial residual stress was measured by X-ray diffraction method. Fatigue experiments of specimens with and without LSP were performed, and the microstructural features of fracture of specimens were characterized by scanning electron microscopy （SEM）. The results indicate that the compressive residual stress can be induced into the surface of specimen, and the fatigue life of the specimen with LSP is 3.5 times as long as that of specimen without LSP. The location of fatigue crack initiation is transferred from the top surface to the sub-surface after LSP, and the fatigue striation spacing of the treated specimen during the expanding fatigue crack is narrower than that of the untreated specimen. Furthermore, the diameters of the dimples on the fatigue crack rupture zone of the specimen with LSP are relatively bigger, which is related to the serious plastic deformation in the material with LSP.
