In aerospace and other industrial manufacturing domains, the use of parts with large and difficult-to-machine thin-walled curved surfaces is widespread. Achieving good surface morphology when processing these curved structural parts is a critical research focus due to their insufficient stiffness, variability and susceptibility to noticeable tool marks. This study conducted experimental research based on the principle of electrochemical milling (EC milling) of surfaces, considering different machining sequences. The processing sequence of "first middle and then two sides" obtained a superior surface morphology. Secondly, to address the issue of tool marks, tools with different outlet surface lengths were designed. The results demonstrate that increasing the outlet surface length to 20mm minimized machining depth deviation, roundness error, and tool marks on the machined surface. Ultimately, the experiment confirmed the feasibility of enhancing tool marks by adjusting the length of the outlet surface, thereby achieving excellent surface morphology in the processed workpieces.

Aerospace metal honeycomb seal structures are an essential component of aircraft engines, and their manufacturing has been at the forefront of industrial focus. Due to the low structural stiffness and high-strength materials, it has become one of the complex components that are difficult to machine. To achieve precision manufacturing of honeycomb seal structures, this study proposes the use of electrochemical discharge machining (ECDM) for machining honeycomb seal structures, which has the high efficiency of electric discharge machining (EDM) and superior surface quality of electrochemical machining (ECM). The experiment results explored the influence of different experimental variables on surface quality, energy distribution relation and material removal rate (MRR). Moreover, in order to predict the machined depth, the mathematical relation between different variables and machined depth was established, which can be expressed as h = 1.407 c 0.1135 u 0.3102 v - 0.391 , and a better machining outcome was achieved at 1 wt%, 15 V, and 22 mm/min with an optimal eta 2 of 0.36. Finally, this study elucidates the material removal mechanism of honeycomb seal structures in ECDM, which demonstrates that ECDM has a high application value in the manufacturing of honeycomb seal structures.

With the development of machining technology, the application scenarios of national defense and military equipment, civil aviation vehicles, and reciprocating air and space vehicles are becoming more and more complicated [...]

Electrochemical milling is an ideal technique for machining large-scale 3D structures that consist of aerospace aluminum alloys. The distribution of the electric and flow fields are vital to the quality of the machined surface, and the structures of the inner flow channel and bottom outlet have different effects on the electric and flow fields on the machining surface. In this study, two specialized structures of a tool cathode were optimized by simulating the electric and flow fields, and a reasonable design basis for the tool cathode was obtained. Based on this, an ECM experiment was performed with the same machining parameters using different tools, and a 20 mm × 20 mm plane was machined. The experimental results showed that using an appropriate tool cathode can create ideal flow and electric fields, resulting in better processing. After optimizing, the machining plane arithmetic mean deviation decreased by 43% (from 14.050 μm to 6.045 μm), and the region elevation difference decreased by 52% (from 105.93 μm to 55.17 μm).

Titanium matrix composites (TMCs) are commonly used in aerospace applications and can be effectively processed using electrochemical machining (ECM). This study aims to investigate the impact of reinforced particles on the electrochemical corrosion behavior of these composites. Three alloys with varying particle contents were subjected to electrochemical characterization and dissolution experiments, revealing a mechanism of passive film fragmentation through pore corrosion. The results indicate that while the content of reinforced particles does not affect the rate of passive film formation, it does increase defects in the film, making electrochemical reactions more likely. Additionally, this study introduces a new method for measuring passive film removal time using constant potential discrete time analysis, which highlights limitations in current waveform observation methods. Finally, a model was developed to simulate TMC dissolution in NaCl solution.

Electrochemical machining offers several benefits, making it a valuable technique for producing GH3536 alloys. This study investigated the electrochemical reactions of GH3536 alloy in NaCl and NaNO3 solutions. The open circuit potential, polarization curve, and electrochemical impedance spectroscopy (EIS) results were measured. The results revealed that the rate of electrochemical dissolution was higher in NaCl solution. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) demonstrated that corrosion cracks occurred on the passivation film in NaCl solution, while corrosion pits with less insoluble products were observed in NaNO3 solution. It was found that corrosion pits appeared in both solutions through metallurgical microscope analyses, and the main composition of corrosion products on the surface was the same in different solutions with the use of X-ray photoelectron spectroscopy (XPS). Additionally, models for the electrochemical dissolution reaction were developed.

采用打孔穿丝一体化的方法,对9Cr18Mo不锈钢进行封闭轮廓图形的微细电解线切割加工,研究脉冲电压、脉冲频率、占空比、电解液浓度对加工精度的影响,并探讨影响微缝截面倒圆大小的因素.结果表明:在电解液质量浓度2 g/L、电压17 V、电源频率1000 kHz、占空比30％、进给速度1.2 μm/s的最优条件下,在510 μm厚的9Cr18Mo不锈钢上加工的封闭轮廓图形质量较好,切缝一致性高.

Titanium matrix composite (TiB+TiC)/TC4 has excellent physical properties and is a completely new composite material with great application prospects in the next generation of the aerospace field. However, there are problems, such as tool loss and material overheating, when using conventional processing methods. Electrochemical milling is a low-cost, high-efficiency processing method for difficult-to-machine metal materials with no tool wear. In this research, the feasibility of the electrochemical milling of (TiB+TiC)/TC4 and removal mechanisms during processing was reported for the first time. The feasibility of electrochemical milling is verified by the current efficiency experiment and basic processing experiment. Through the adjustment of the processing parameters, the final material removal rate increased by 52.5% compared to that obtained in the first processing, while the surface roughness decreased by 27.3%. The removal mechanism during processing was further performed based on the current efficiency experiment; three stages were observed and concluded during the electrolytic dissolution. This research proved that electrochemical milling is an excellent low-cost method for roughing and semi-finishing (TiB+TiC)/TC4 composites and provides guidance for better electrochemical milling in the titanium matrix composites.

开放共享平台的建立提高了高校大型仪器设备的使用率,但仍存在一些需要改进的地方.明确设备共享的目标,才能发现现行体制出现的问题.进而从整体上提出仪器开放改革的措施,使设备的利用绿最大化,使设备带来最大的社会效益.

为提高微细工具电极的微细程度,提出一种附加液膜电化学刻蚀法制备微细工具电极的新方法,进行相关工艺试验研究.对比试验结果表明,附加液膜电化学刻蚀法制备的工具电极尖端半径均比传统液膜电化学刻蚀法制备的半径小;附加液膜类型对工具电极尖端半径影响试验结果表明,(胶水)附加液膜制备的工具电极尖端半径尺寸和电极锥度最小,其次为(植物油)附加液膜,最大为(去离子水)附加液膜;而初始半径为250 μm的钨棒在附加液膜(胶水)试验中出现特例,这是由于刻蚀时间过长胶水固化而引起的工具电极尖端过腐蚀所导致.

20Hz以下的低频振动对电子显微镜的检测功能有很大干扰,需要采取各种减震手段降低低频振动的干扰.目前常用的减震方法中,如橡胶减震器、混凝土减震台、空气弹簧等等在20Hz以下的低频段效果很差,而采用主动减震装置可以有效抑制1Hz以上的振动,适合对低频段减震要求较高的场合.此外在某些特定条件下,减震沟对于低频振动的干扰也有较好的抑制效果.

Electrochemical mill-grinding (ECMG) is an ideal technical means to achieve an efficient and precise machining of titanium alloy monolithic structural parts. In the rough ECMG process, the selection of a reasonable cutting depth can improve the machining efficiency of the rough machining. Adopting a reasonable cathode tool structure can achieve a higher precision in the formation of the rough surface, reduce the finishing allowance and tool wear of subsequent finishing. With this aim, the present research proposed a cathode tool with a reasonable structure. Simulation results showed that the designed cathode tool presented a good uniformity of the flow field in the machining gap, which resulted in a higher precision in the formation of the rough surface. For experimental validation, a larger cutting depth and a designed cathode tool was employed to carry out the rough and finish machining experiments on a Ti6Al4V titanium alloy. The experimental results show that a good flatness of the sidewall of the rough-machining groove was obtained by this scheme. Furthermore, the machining surface exhibited no flow marks, and rough machining accounted for 92.37% of total removal. Moreover, measurement of the micro-morphology, roughness and elemental composition of the machined surface, and the effects of different machining parameters on the surface quality of titanium alloys, were studied.

Objectives: The present study aimed to retrospectively compare the clinical and imaging characteristics and laboratory data of patients with malignant tumor concurrent with acute ischemic stroke (IS) and patients with cerebral infarction only, and to analyze the potential related risk factors. Method: A total of 126 patients with acute cerebral infarction concurrent with malignant tumor were collected and assigned to the malignant tumor group. In addition, 120 patients hospitalized for routine acute IS during the same period were randomly selected as the control group. Demographic data and common risk factors of cerebrovascular disease, laboratory data, and imaging characteristics in these two groups were compared. Results: In the malignant tumor group, the age of onset was relatively low, and the National Institutes of Health Stroke Scale score, 90 d recurrence rate, and fatality rate were higher than for those in the control group (p < 0.05). However, most patients had no traditional risk factors of stroke. Biochemical results revealed that the peripheral hemoglobin of patients with malignant tumor and cerebral infarction was lower than for those in the control group (p < 0.05). Furthermore, the levels of D-dimer, fibrinogen, tumor markers CA125, CA199, and carcinoembryonic antigen were significantly elevated, and the difference was statistically significant (p < 0.05). Magnetic resonance imaging results revealed that multiple intracranial infarcts were more common in patients in the malignant tumor group, and the difference was statistically significant compared with patients with cerebral infarction only (p < 0.05). Conclusion: Patients with cancer and IS had fewer traditional stroke risk factors but more anemia as well as higher D-dimer level, tumor marker rate, short-term mortality, and stroke recurrence rate. Furthermore, lower age of onset and other characteristics, including multiple intracranial infarcts, can be regarded as important characteristics of such patients.

PURPOSE To evaluate the clinical efficacy of percutaneous trans-hepatic integrated 125I seed stents implantation for malignant lower biliary tract obstruction. METHODS Thirty-two patients with malignant lower biliary obstruction were randomly divided into two groups. One group underwent the therapy with integrated 125I seed stents (Test group, n = 13), and another group received conventional metal stents implantation for treatment (Control group, n = 19). The pre- and post-operative changes in biochemical indices, white blood cell count, IgG level, stent patency, survival time, tumor size and complications were compared between the two groups. RECIST 1.1 (Response Evaluation Criteria In Solid Tumors) was used to evaluate therapeutic effects. The average follow-up time was 12.3 months. RESULTS The differences between pre- and post-operative (30 days) intragroup biochemical indices had statistically significant difference (P < 0.05), but there were no significant differences (P > 0.05) in leukocyte counts and IgG levels. As to the median time of stent patency and patients' survival, there were significant differences (P < 0.05) between Control and Test groups (3.9 months vs. 8.1 months, 139 days vs. 298 days, respectively). Three months after the operation, the average tumor size was reduced in the Test group, but was increased in the Control group (P < 0.05). There was no significant difference in the incidence of complications between the two groups. The evaluation results using RECIST 1.1 showed that there were statistically significant differences between the two groups in terms of the rates of remission, control, and progression (χ2 = 17.5, P < 0.05). CONCLUSIONS The study indicates that integrated 125I seed stents are effective in reducing jaundice symptoms, inhibiting tumor growth, improving stent patency and prolonging patient survival, which may serve as a safer and more feasible method in treating malignant lower biliary obstruction with minimal invasiveness.

The gold potassium citrate has litter cyanide ,and the solution which uses gold potassium citrate as its main salt has good stability and could be used repeatedly. To solve the problem that the traditional solution for the electrodeposition of gold,contain a lot of cyanide,has high toxicity,huge damage to environment and is hard to deal with ,but the non-cyanide planting baths is unstable and can not be used repeatedly,the gold potassium citrate is used as main salt to electroform gold micro parts. Different parameters are compared to investigate the influence of the current density ,the distance between cathode and anode and flow rate of liquid on the gold micro parts. Using the optimal parameters,the gold micro parts are successfully obtained on Ti substrate.

Crack -free hard chromium electroplating technology with the ceramic particles polishing-assisted was applied in electroplating hard chromium test. The electroplating experiments were carried out on the 300M substrate. Influences of the current density ,rotating speed of cathode , solution temperature,pulse frequency and duty ratio on micro-hardness and corrosion resistance of the coatings have been studied experimentally. With the optimized parameters ,rather higher hard chromium plating with smaller crystalline grain size and better corrosion resistance coatings were obtained. The microstructure of the surface was tested by SEM ,which had bright surfaces ,well-distributed grain structure and with no cracks.

针对现有的有氰镀金体系镀液含有有毒的氰化物,废液污染环境、处理困难等问题,提出低危害电镀金工艺实验研究.为了极大减少溶液在实验过程中电离出游离态氰离子,选择柠檬酸金钾作为电镀金溶液配方主盐.在既定的溶液配方基础上,改变电场、流场、冲液方式、阴阳极间距等参数,优化实验工艺,在紫铜基体上进行基础实验,得到结晶晶粒细致,与基底结合力高,表面光亮度好的电镀层.采用原子力量微镜(Atomic forcemicroscope,AFM)测试了基体和镀层的微观形貌,镀金层有效复制,基体表面的粗糙度降低.应用扫描电子量微镜(Scanning election mircroscope,SEM)分析了镀层的组成成份,并用WS-97涂层附着力划痕试验仪检测了镀层的结合力,其性能满足行业标准的要求.

The prime mixture of Zn-4.5Al-RE-Mg-Ti alloy (ZA) and nano-CeO2 clusters was prepared by mechanical stirring method with high engulfing ability. Then the engulfed nano-CeO2 clusters were dispersed by high-intensity ultrasonic to obtain nano-CeO2/ZA composites (ZACs) with the nominal mass fractions of 1%-6%. The optical microscope observations show that the microstructure of ZACs at room temperature consists of island-like eutectoid structure alpha(A1)+beta(Zn) and lamellar structure alpha+beta. Based on the FE-SEM results, nano-CeO2 particulates could be homogeneously distributed in the ZACs prepared by the combination stirring technology.

Objective: To explore the mismatched manifestation between regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) of astrocytomas. Methods: Both conventional and perfusion CT were performed on 29 patients with pathologically confirmed astrocytomas (15 cases in Grades I-II, 14 cases in Grades III-IV). Time-density curves were plotted, cerebral blood flow and volume maps were generated, and the values between rCBF and rCBV in the same region of interest (ROI) were compared. Results: Twelve low-grade astrocytomas showed low or medium values of both rCBF (46.95 +/- 22.92 ml . 100 g(-1) . mm(-1)) and rCBV (5.74 +/- 3.61 ml . 100 g(-1)); 12 high-grade astrocytomas showed high values of both rCBF (95.44 +/- 42.58 ml . 100 g(-1) . min(-1)) and rCBV (9.24 +/- 5.32 ml . 100g(-1)). These cases exhibited agreement between the values of rCBF and rCBV. However, the remaining five astrocytomas were mismatched, showing reduced rCBF value and increased rCBV value in the same ROI. The discrepancy may mislead to an inaccuracy of perfusion CT in grading gliomas. Conclusions: The mismatched manifestation between rCBF and rCBV occasionally exists in some areas of astrocytomas. Hence, attention should be paid to assessments in preoperative grading of astrocytomas and in monitoring therapeutic effects. (C) 2009 Elsevier Inc. All rights reserved.