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排序方式: 共有9079条查询结果,搜索用时 31 毫秒
82.
Yong-jin Yang ) Ke-wei Gao ) Chang-feng Chen ) ) School of Materials Science Engineering University of Science Technology Beijing Beijing China ) Department of Materials Science Technology China University of Petroleum Beijing China 《北京科技大学学报(英文版)》2010,17(1):58-62
The effect of hydrogen on the fracture behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing (SSRT).Hydrogen was introduced into the sample by electrochemical charging.The results show that surface microcracks form gradually during aging at room temperature when desorption of hydrogen takes place after hydrogen charging at a current density of 5 mA/cm 2 for 24 h.SSRT shows that the increase of ductility loss is significantly obvious as the hydrogen charging current density inc... 相似文献
83.
The hydrogen-induced cracking (HIC) behavior of X80 pipeline steel was studied by means of electrochemical charging, hydrogen permeation tests, tension test, and scanning electron microscopy (SEM). The experimental results indicate that the increase of charging time and charging current density or the decrease of the solution pH value leads to an increase of the hydrogen content in X80 steel, which plays a key role in the initiation and propagation of HIC. It is found that the majority of macro-inclusions w... 相似文献
84.
通过对25个结构钢缺口板进行的单向拉伸断裂试验,验证了提出的结构钢广义屈服模型和椭球面断裂准则.用ANSYS软件中的参数化设计语言APDL和用户编程功能UPFs,将提出的静水应力型广义屈服模型编制成子程序模块,对结构钢缺口板断裂试验进行了基于广义屈服模型和椭球面断裂准则的数值模拟分析.试验结果表明:裂纹起始于缺口边缘内侧,裂纹在厚度方向贯通后沿宽度发展,试件最终断裂于缺口薄弱断面.缺口板断裂应力场分析表明,提出的椭球面断裂准则对预测结构钢缺口板初始开裂具有广泛适用性和较高精度. 相似文献
85.
The effects of quality and content of fly ash on the early-age cracking behavior of high-flowing concrete (HFC) were investigated.
The early-age cracking behavior of the HFC was analyzed by combining the tests of evaporation capacity and electrical resistivity
of the HFC. In these tests, a modified flat-type specimen was adopted. The results show that the HFC will have a lower evaporation
capacity when it is mixed with fine fly ash, while it will have a higher evaporation capacity when grade III fly ash is used
as mineral admixture. And the electrical resistivity rate of HFC reduces with the increase of the content of fly ash. A nonlinear
relationship exists between the cracking time of HFC and the minimum electrical resistivity. The early-age cracking behavior
of HFC with fly ash can be enhanced by appropriately increasing the fine particle content and MgO, K2O, and SO3 contents of fly ash. The optimal content of fly ash, which makes a satisfied early-age cracking behavior of HFC, is obtained.
And when the content of fly ash exceeds a critical value, the early-age cracking behavior of HFC will rapidly decrease.
Foundation item: Project(50478003) supported by the National Natural Science Foundation of China; Project(2002F007) supported by the Natural
Science Foundation of Fujian Province, China 相似文献
86.
The experimental tests of tensile for lead-free solder Sn-3.5Ag were performed for the general work temperatures range from
11 to 90 °C and strain rate range from 5×10−5 to 2×10−2 s−1, and its stress—strain curves were compared to those of solder Sn-37Pb. The parameters in Anand model for solder Sn-3.5Ag
were fitted based on experimental data and nonlinear fitting method, and its validity was checked by means of experimental
data. Furthermore, the Anand model was used in the FEM analysis to evaluate solder joint thermal cycle reliability. The results
show that solder Sn-3.5Ag has a better creep resistance than solder Sn-37Pb. The maximum stress is located at the upper right
corner of the outmost solder joint from the symmetric center, and thermal fatigue life is predicted to be 3.796×104 cycles under the calculated conditions.
Foundation item: Project(50376076) supported by the National Natural Science Foundation of China 相似文献
87.
周期阵列压痕方法是研究微观摩擦学的工具之一。由于周期阵列刚性压头压在半平面弹性体的表面时,会产生周期的Ⅰ型奇异压应力场,该奇异应力场的应力集中达到一定程度时,即达到临界条件时,该奇异应力场所在的边界将开裂。压痕边界的开裂问题是一个新型的断裂力学问题,通过边界移动的能量释放率的分析给出了压痕边界开裂能量释放率数学表征,并给出边界开裂的临界载荷和临界开裂角。 相似文献
88.
硝铵厂合成氨系统以焦炉煤气为原料生产合成氨,二段转化炉废热锅炉是净化车间转化系统关键设备之一。该设备通过回收利用二段转化炉出口900℃的高温气体的热能产生2.5MPa蒸汽供生产使用,用以调节转化气的温度,满足生产要求。因此,该设备的安全、稳定运行对整个合成氨系统的正常生产具有重要意义。 相似文献
89.
90.
杨房沟水电站地下洞室群规模宏大、地质条件复杂,施工期围岩稳定问题突出。为解决洞室开挖过程中普遍揭露的脆性岩体高应力破坏、缓倾结构面导致的顶拱变形破坏、喷层开裂脱落等岩石力学问题,结合施工地质、监测成果和数值模拟开展动态反馈分析,对洞群围岩稳定性进行了系统地分析和预测。结果表明,在洞室群开挖过程中,上游侧拱肩位置存在应力集中,是导致脆性硬岩发生片帮破坏的主要原因,而及时、有效的系统支护对抑制围岩应力型破坏至关重要;缓倾结构面对顶拱围岩变形与稳定起着控制性作用,主要表现为断层下盘岩体坍塌破坏和深层变形问题;在中高地应力条件下,受不利地质构造和施工质量等因素控制,洞室顶拱混凝土喷层容易发生开裂、脱落问题。通过开展施工期围岩监测反馈分析,不仅能够解释围岩变形破坏机制,而且能够为支护设计优化和信息化施工提供科学依据。 相似文献