In eddy current testing, the law of attenuation of eddy current(EC) is of great concern. In conductive half space under the excitation of uniform magnetic field, the EC density decreases exponentially in the depth dir...In eddy current testing, the law of attenuation of eddy current(EC) is of great concern. In conductive half space under the excitation of uniform magnetic field, the EC density decreases exponentially in the depth direction. However, in conductor with finite thickness tested by coil, the distribution of EC in the depth direction is more complicated. This paper studies the characteristics of EC attenuation in metallic plate of finite thickness. Simulation results show that there is an EC reflection at the bottom of plate, which changes the law of EC attenuation. A new concept, namely the equivalent attenuation coefficient, is proposed to quantify the speed of EC attenuation. The characteristics of EC attenuation are utilized to explain the nonmonotonic relation between coil voltage and plate thickness. Procedure of selecting frequency is discussed. Thereafter, measurement of plate thickness is carried out and accurate result is obtained.展开更多
Bending fatigue tests were carried out on cruciform welded joints of China-made platform steel E36-Z35 with plate thickness of 16mm, 32mm and 40mm. The tests consisted of testing in air and in sea water with and witho...Bending fatigue tests were carried out on cruciform welded joints of China-made platform steel E36-Z35 with plate thickness of 16mm, 32mm and 40mm. The tests consisted of testing in air and in sea water with and without cathodic protection (-850mV. SCE). The sea water corrosion fatigue tests were conducted at loading frequency of 0.2 Hz and sea water temperature of 20°C. The test results show an obvious reduction in fatigue strength of welded joints with increasing plate thickness in all the three test conditions. The present paper proposes different thickness corrections for fatigue strength and fatigue life of welded joints in air and in sea water with and without cathodic protection respectively. In addition, an explanation for thickness effect on fatigue life of welded joints is given by using the theory of fracture mechanics.展开更多
滤膜堵塞型传感器可以半定量地评价油液的固体颗粒污染度,其关键元件为金属微孔滤膜.为了获得性价比较高的金属微孔滤膜,选择600目斜纹不锈钢丝网为镀覆基材,研究所选不锈钢丝网表面化学镀镍的工艺流程,通过扫描电镜（LEO1450VP）和能...滤膜堵塞型传感器可以半定量地评价油液的固体颗粒污染度,其关键元件为金属微孔滤膜.为了获得性价比较高的金属微孔滤膜,选择600目斜纹不锈钢丝网为镀覆基材,研究所选不锈钢丝网表面化学镀镍的工艺流程,通过扫描电镜（LEO1450VP）和能谱分析仪（INCA ENERGY 300）分析镀层成分、镀层与基材的结合情况以及微孔滤膜的微孔及丝径尺寸.结果表明,本研究工艺下制备的微孔滤膜镀层为低磷镀层,抗拉强度为400～700MPa,硬度为580HV,镀层与基体材料结合牢固.镀覆20min和30min后可获得微孔尺寸分别为14μm和10μm的微孔滤膜,且丝径镀覆厚度均匀一致,微孔大小也均匀一致.利用所研制的金属微孔滤膜制成滤膜堵塞型传感器,配制样液分别对该传感器的重复性精度和污染度检测精度进行检验,结果表明,微孔滤膜传感器具有较好的重复性精度,对油液中固体颗粒污染度等级的测定结果与实际值完全一致,因此所研制的金属微孔滤膜可以满足滤膜堵塞型传感器的使用要求.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51277154)Xiamen Key Laboratory of Optoelectronic Transducer Technology+1 种基金Fujian Key Laboratory of Universities and Colleges for Transducer TechnologyInnovative Talents Program of Far East NDT New Technology&Application Forum
文摘In eddy current testing, the law of attenuation of eddy current(EC) is of great concern. In conductive half space under the excitation of uniform magnetic field, the EC density decreases exponentially in the depth direction. However, in conductor with finite thickness tested by coil, the distribution of EC in the depth direction is more complicated. This paper studies the characteristics of EC attenuation in metallic plate of finite thickness. Simulation results show that there is an EC reflection at the bottom of plate, which changes the law of EC attenuation. A new concept, namely the equivalent attenuation coefficient, is proposed to quantify the speed of EC attenuation. The characteristics of EC attenuation are utilized to explain the nonmonotonic relation between coil voltage and plate thickness. Procedure of selecting frequency is discussed. Thereafter, measurement of plate thickness is carried out and accurate result is obtained.
文摘Bending fatigue tests were carried out on cruciform welded joints of China-made platform steel E36-Z35 with plate thickness of 16mm, 32mm and 40mm. The tests consisted of testing in air and in sea water with and without cathodic protection (-850mV. SCE). The sea water corrosion fatigue tests were conducted at loading frequency of 0.2 Hz and sea water temperature of 20°C. The test results show an obvious reduction in fatigue strength of welded joints with increasing plate thickness in all the three test conditions. The present paper proposes different thickness corrections for fatigue strength and fatigue life of welded joints in air and in sea water with and without cathodic protection respectively. In addition, an explanation for thickness effect on fatigue life of welded joints is given by using the theory of fracture mechanics.
文摘滤膜堵塞型传感器可以半定量地评价油液的固体颗粒污染度,其关键元件为金属微孔滤膜.为了获得性价比较高的金属微孔滤膜,选择600目斜纹不锈钢丝网为镀覆基材,研究所选不锈钢丝网表面化学镀镍的工艺流程,通过扫描电镜（LEO1450VP）和能谱分析仪（INCA ENERGY 300）分析镀层成分、镀层与基材的结合情况以及微孔滤膜的微孔及丝径尺寸.结果表明,本研究工艺下制备的微孔滤膜镀层为低磷镀层,抗拉强度为400～700MPa,硬度为580HV,镀层与基体材料结合牢固.镀覆20min和30min后可获得微孔尺寸分别为14μm和10μm的微孔滤膜,且丝径镀覆厚度均匀一致,微孔大小也均匀一致.利用所研制的金属微孔滤膜制成滤膜堵塞型传感器,配制样液分别对该传感器的重复性精度和污染度检测精度进行检验,结果表明,微孔滤膜传感器具有较好的重复性精度,对油液中固体颗粒污染度等级的测定结果与实际值完全一致,因此所研制的金属微孔滤膜可以满足滤膜堵塞型传感器的使用要求.
