银氧化锡电接触材料直流材料转移和电弧侵蚀形貌研究

运用触点材料测试系统进行了AgSnO2电接触材料在低压直流条件下的电接触实验，研究了材料转移情况，分析了电弧侵蚀形貌和成分变化。结果表明：AgSnO2（12）的转移方向为阴极向阳极转移，阴、阳极材料转移速率均为初期较快后逐渐减缓。阴、阳极表面可按电弧侵蚀形貌分成对应的三个圆环状区域：中心A区—电弧作用域，B区—电弧影响区，最外层区—电弧无明显影响区。阴极电弧作用区微观形貌主要为海绵状基体上分布着大小不一的孔洞，Sn 和 O 元素多偏聚在孔洞区域；阳极侵蚀区主要为熔融流动铺层或喷溅状态。

电弧作用下纤维结构钨铜触头材料的形貌特征

根据触头材料电弧侵蚀后材料表面的微观分析,发现触头表面电弧侵蚀形貌呈现出熔滴、孔洞、蚀坑的特征,并且钨丝丝径越大铜含量越高,材料侵蚀的越严重。

Influence of alloy components on arc erosion morphology of Ag/MeO electrical contact materials

Arc erosion morphologies of Ag/MeO（10） electrical contact materials after 50000 operations under direct current of 19 V and 20 A and resistive load conditions were investigated using scanning electron microscope（SEM） and a 3D optical profiler（3DOP）. The results indicated that 3DOP could supply clearer and more detailed arc erosion morphology information. Arc erosion resistance of Ag/SnO_2（10） electrical contact material was the best and that of Ag/CuO（10） was the worst. Arc erosion morphology of Ag/MeO（10） electrical contact materials mainly included three different types. Arc erosion morphologies of Ag/ZnO（10） and Ag/SnO_2（10） electrical contact materials were mainly liquid splash and evaporation, and those of Ag/CuO（10） and Ag/CdO（10） were mainly material transfer from anode to cathode. Arc erosion morphology of Ag/SnO_2（6）In_2O_3（4） electrical contact materials included both liquid splash, evaporation and material transfer. In addition, the formation process and mechanism on arc erosion morphology of Ag/MeO（10） electrical contact materials were discussed.

细晶W-25Cu-2.0 mass%La2O3合金电接触性能

采用包套热挤压法制备了稀土氧化镧掺杂W-25Cu-2.0 mass%La2O3合金,在JF04C型电接触试验机上测试了稀土掺杂钨铜合金的接触电阻、燃弧时间、燃弧能量等电接触性能,利用钨灯丝扫描电镜对电接触材料阴阳两极电弧侵蚀形貌进行了微观分析。结果表明：稀土钨铜合金触头材料接触电阻较纯钨铜合金明显减小,且接触电阻不随接触电压的增大而增大;燃弧能量和燃弧时间随着接触电压的增大而增大,且波动性变大;闭合过程中的燃弧能量和燃弧时间均大于断开过程。电弧侵蚀后材料转移方向为阳极向阴极转移;电弧侵蚀形貌为阳极表面出现微小凹坑、阴极表面产生微小凸起;阳极触头表面出现富W区,阴极触头表面出现富Cu区,La2O3主要聚集在富W区。

Erosion and erosion-corrosion of Al-brass alloy: Effects of jet velocity, sand concentration and impingement angle on surface roughness

Effects of jet velocity,sand concentration and impingement angle on the surface roughness of Al-brass alloy were investigated after erosion and erosion?corrosion tests.The tests were performed using a jet impingement rig.The eroded surfaces were characterized using2-D and3-D surface profilometery and scanning electron microscopy(SEM).The results showed that there was an increase in the surface roughness of the erosion?corrosion samples as sand concentration was increased to1,5and10g/L at jet velocities of9,6and3m/s,respectively.However,the surface roughness decreased with a further increase in sand concentration.This decrease in the surface roughness was attributed to the higher work hardening of the surface,rebounding or blanketing effect and very high frequency of the impacts at the higher sand concentrations.The surface roughness increased as the jet velocity increased.The results also showed that the change in the surface roughness with impingement angle was not significant at two jet velocities of3and6m/s.However,at a higher jet velocity of9m/s,formation of ripples on the erosion surfaces at oblique angles resulted in a higher surface roughness as compared with the normal impingement angle.

Scorpion back inspiring sand-resistant surfaces

A new approach which adopted the idea of coupling bionics to improve erosion resistance was presented, by taking the desert scorpion as the research object. The anti-erosion characteristic rules and mechanism of desert scorpion＇s surface under the dynamics effect of gas/solid mixed media were researched, especially the comprehensive influence mechanism of surface morphology, microstructure, creature flexibility and many other factors was studied. Simulation by CFD software was applied to predict the relative erosion severity. Samples with the coupled bionic configurations and flexibility were produced. Experiment optimum design theory was employed to design experiment scheme. Silica sand of particle size of 105-830 ~tm was used as the erodent. The erosion tests were carried out to validate the simulation results obtained. It is shown that the predicted results are in agreement with those obtained from the experiment. And contrast tests were carried out at the best and worst test points of erosion resistance for four samples. Contrast tests show that the erosion resistance trend occurs in such order with the best erosion resistance as coupling sample, groove, smooth and flexibility, and smooth, and the increasing rate of erosion resistances in sequence of 12.08%, 8.87%, 6.03% in the best test point. But in the poorest point, the increasing rate of erosion resistance is in sequence of 15.64%, 9.53%, 6.59%. The morphologies of eroded surface were examined by the scanning electron microscope, and the possible wear mechanism was discussed.

Macroscopic and microscopic fracture features of concrete used in coal mine under chlorine salt erosion

The microscopic morphology and pore structure characteristics of concrete with composite admixtures(fly ash and mineral powder) after chlorine salt erosion were analyzed via scanning electron microscopy(SEM) and mercury injection porosimetry(MIP), providing the basis for the design and maintenance of concrete shafts in coal mines. The above-mentioned characteristics were compared with the macroscopic characteristic of concrete fractures under uniaxial compression. The results show that the macroscopic fracture characteristics of concrete under uniaxial compression change from longitudinal split fracture and oblique section shear fracture to conjugate cant fracture, and the degree of breakage increases.Interface cracks, cement paste cracks, spherical surface cracks, and aggregate cracks appear in concrete under uniaxial compression. In the early stages of corrosion, the original cracks which are obvious are repaired. When the corrosion becomes more serious, cement paste cracks appear, and the number of harmful holes increases while the number of harmless holes decreases. This study also reveals the relationship between the macroscopic properties and microscopic structure of concrete under chloride salt erosion. Finally, the paper preliminarily discussed the relationship between the macroscopic properties and mesoscopic characteristics of concrete under chlorine salt erosion.

不同SnO_2含量的Ag-SnO_2触头材料电弧侵蚀行为

采用粉末冶金法制备了不同SnO_2含量的Ag-SnO_2触头材料,研究了SnO_2含量对Ag-SnO_2触头材料电弧侵蚀行为的影响。使用扫描电子显微镜(SEM)表征了Ag-SnO_2触头材料电弧侵蚀形貌,对影响Ag-SnO_2触头材料电弧侵蚀的因素进行了分析。结果表明,在电弧侵蚀过程中侵蚀优先发生在SnO_2区域。随SnO_2含量增多,燃弧时间依次增加,侵蚀面积逐渐减小,侵蚀坑变深,金属喷溅增强。

SnO_(2)含量对AgCuOSnO_(2)电接触性能的影响

采用反应合成法制备了不同SnO_(2)含量的AgCuOSnO_(2)电接触材料。采用FQR-7501型涡流电导率仪测量抛光AgCuOSnO_(2)的电导率。用扫描电镜(SEM)观察和研究了AgCuOSnO_(2)电接触表面的侵蚀形貌。JF04C直流数字电阻测试仪用于进行10000点测试。结果表明,AgCuO(10)SnO_(2)(5)和AgCuO(10)SnO_(2)(8)电触头材料在U=12 V和I=15 A时的接触电阻小于1.3 mΩ,波动最小;当I=10 A时,AgCuO(10)SnO_(2)(x)(x=2,5,8)的熔焊力小于8 cN,AgCuO(10)SnO_(2)(5)电触头的熔焊力较小,当电流增大时熔焊力较为稳定;当AgCuOSnO_(2)电触头材料发生电弧侵蚀时,材料从阳极向阴极转移。随着SnO_(2)含量的增加,材料传输过程中的损耗得到抑制和降低。所转移的电触头表面有少量的气孔和微裂纹,表面形貌较为平坦。

Three-dimensional numerical simulation of glacial trough forming process

The glacial trough is a common glacier erosion landscape, which plays an important role in the study of glacier erosion processes. In a sharp contrast with the developing river, which is generally meandering, the developing glacial trough is usually wide and straight. Is the straightness of the glacial trough just the special phenomenon of some areas or a universal feature? What controls the straightness of the glacial trough? Until now, these issues have not been studied yet. In this paper, we conduct systematic numerical models of the glacier erosion and simulate the erosion evolution process of the glacial trough. Numerical simulations show that:(1) while the meandering glacier is eroding deeper to form the U-shaped cross section, the glacier is eroding laterally. The erosion rate of the ice-facing slope is bigger than that of the back-slope.(2) The smaller(bigger) the slope is, the smaller(bigger) the glacier erosion intensity is.(3) The smaller(bigger) the ice discharge is, the smaller(bigger) the glacier erosion intensity is. In the glacier erosion process, the erosion rate of the ice-facing slope is always greater than that of the back-slope. Therefore, the glacial trough always develops into more straight form. This paper comes to the conclusion that the shape evolution of the glacial trough is controlled mainly by the erosion mechanism of the glacier. Thereby, the glacial trough prefers straight geometry.