外文文献翻译--脉冲电解液流动钛合金深小孔的电化学钻削【中文4040字】【中英文WORD】
外文文献翻译--脉冲电解液流动钛合金深小孔的电化学钻削【中文4040字】【中英文WORD】,中文4040字,中英文WORD,外文,文献,翻译,脉冲,电解液,流动,钛合金,小孔,电化学,中文,4040,中英文,WORD
脉冲电解液流动钛合金深小孔的电化学钻削
1.简介
具有相当高宽比的深孔，如涡轮叶片和叶片上的冷却孔已广泛应用于航空航天领域[1,2]。这些孔通常由镍基超合金，钛合金和金属间化合物制成，这些材料难以用机械加工技术加工。不管材料的机械性能如何，大多数都使用非传统加工技术。激光钻孔和放电加工（EDM）在表面上产生重铸层，必须随后在需要特定表面抛光的应用中去除重铸层。此外，随着加工深度的增加，电火花加工中的刀具磨损恶化，加工效率降低。电化学钻孔（ECD）可以达到较高的表面质量，不会出现刀具磨损和冶金缺陷。 ECD的固有特性意味着它可以成为在难切削材料中加工深孔的主要解决方案[3,4]。
在工业应用中，开发酸溶液以避免溶解的金属离子形成不溶性氢氧化物。 但是，酸性废水的环境处理非常昂贵。 因此，已经做出许多努力用中性盐溶液代替酸溶液[5-7]。 在中性水溶液中，电解产物通常在深孔钻井中凝聚成絮状结构。 延迟的污泥去除可能阻塞电解液通道，桥接电极之间的连接并引起短路。 用中性盐溶液去除ECD中的副产物因此决定了控制的准确性并限制了处理能力。 也已经提出了各种方法来加速电解更新。
Skoczypiec [8]发现电极超声振动改变了电化学溶解的条件。 电解液流动以及电极极化由于湍流空化而增强。 Rajurkar和Zhu [9]对工具阴极施加轨道运动，这会周期性地扩大侧面加工间隙并使副产物的去除更容易。 Hewidy [10]发现工具阴极的低频振动改变了正面加工间隙的物理条件并挤出了电解质。 Guo [11]发明了一种同轴方法，通过在新鲜电解液中泵送并在孔入口处提取副产物来限制浸没区域并减少废物的去除。
图1：具有脉动流动的ECD示意图
Li等人 [12]逐步增加深孔钻井中的电解液压力，以保持必要的电解液速度，以除去副产物。 但是，这个问题没有得到圆满解决。
已经证实脉动流动造成流体流动的周期性波动并改变边界层的厚度，这在多相流动中已被证实是有效的[13,14]。 然而，对于电化学钻井中的脉动流动的研究还很有限。这项工作主要集中在改善伴随脉动电解液流动的深孔钻削中副产物的去除。 还进行了实验以研究脉动参数对钛合金钻削中副产物去除率，孔性能和最大加工深度的影响。
2.脉冲电解质流的ECD原理
图1显示了具有脉动电解液流的ECD的示意图。与恒定流量的典型ECD过程不同，脉动流量是一种非定常流量，其特征在于质量流量和压力的周期性波动。压力脉动的典型刺激信号如图2所示。𝑇和respectively分别表示脉动周期和振幅，𝑝av表示脉动周期内的平均电解质压力。在脉动电解液流动的ECD中，工件电连接到脉冲电源的正极，管工具连接到负极。速度为10-30m / s的脉动电解液被泵入电极内与管工具中空部分的间隙。当工具电极以恒定速率进入工件时，材料被溶解，形成所需的孔。脉动流的扰动和湍流剧烈搅动混有不溶性污泥和气泡的电解质。搅拌使产品分散得更快，分布更均匀。当施加脉动流时，在加工间隙中产生周期性的低压区域，这降低了由电解质对副产物引起的压紧压力并且增强了电解液的更新。因此，可以提高深孔钻孔和钻孔质量的加工稳定性。
图2：压力脉动的典型刺激信号。
3.用脉冲电解液流动的ECD系统
图3中示出了用于钻深孔的特定系统，其配备有脉动电解液流。该加工系统由电化学钻孔机，脉动压力发生器，电解液循环系统，工具阴极导向装置和电源。自主研发的钻孔机可实现𝑋-𝑌-𝑍轴的精确进给。在这个系统的试验测试中，发现管电极被迫与脉动流一起振动。在这种情况下，管电极像悬臂梁一样起作用，并且电极尖端的振动幅度随着脉动频率的增加而放大。脉动流动产生的机械工程振动进展会对加工造成危害。因此，设计了一种导向装置，以限制工具的振动并提高进给方向上的孔轮廓圆柱度。
脉动流由伺服控制模块产生，该模块在电解液循环系统中串联连接。如图4所示，该伺服系统由一个蓄能器，一个伺服阀，一个控制器芯片，一个滤波器和一个动力单元组成。该模块的核心部件是Get型电动液压伺服阀（RT6615E，Radk中国），它可以快速响应从0到100 Hz范围内的宽带激励信号。该阀的流出量随着阀芯的位置而变化，阀芯的位置由刺激信号控制。建立实时全反馈控制系统来设置激励信号并获取电解质压力。
4.实验结果和讨论
4.1 刺激信号的选择
进行实验以检查脉动压力伺服系统对典型刺激信号的动态响应，如图2所示。伺服系统出口处的实时电解质压力记录在图5中。当刺激信号频率为40Hz，电解质压力随信号波动而一致地变化。当鼓励正弦和三角波时，保持原始信号的细节。然而，当锯齿波和矩形波被驱动时观察到失真。该伺服系统通过伺服阀芯的机械动作进行操作。机械系统具有耦合延迟和高频谐波滤波的固有特性，这些高频谐波会导致信号损失或跳跃信号，例如锯齿波和矩形波。因此，选择近似于基波的正弦波以在下面的实验中驱动脉动电解液流动。
4.2。 脉动流对产品去除的影响
用不同的电解液流动条件电化学钻出厚度为20mm的Ti6Al4V样品以研究脉动流动对副产物去除的影响。 在这个实验装置中，我们施加了26V的电压和0.6mm / min的电极馈送速率。 其他加工参数列于表1中。实验结束后和清洁前，立即使用3D视频显微镜（DVM5000，Leica，德国）观察样品。 深钻孔的入口特征如图6所示。图6（b）所示的孔是用0.4MPa的恒定电解质压力加工的。 在孔的内表面上观察到大量的白色电解质产物。图6（c）至6（f）中的孔用脉冲电解质以0.2MPa的幅度钻孔。 脉动频率分别为2,5,8和10Hz。 很明显，当施加脉动流时，残留产物大部分减少。
图4：脉动压力的伺服系统
当钛及其合金溶解时，离子扩散到电解质中并形成不溶且容易凝聚成絮状结构的TiO 2。 此外，TiO2是亲水性和粘合性的，并且可能粘附到孔内表面并堵塞电解液通道。 这些特性对进一步的材料溶解和加工稳定性有害。 从图6所示的结果可以得出结论，脉动电解液流动对于减少加工表面上的残留副产物并加速它们的去除是有效的。
4.3 脉动流对孔性能的参数影响
在本节中，进行参数实验来研究脉动频率和振幅对深孔钻削的影响。 图7显示了具有脉动参数的加工间隙的变化。 结果表明，当脉动频率和振幅增大时，加工间隙先增大后减小，而加工间隙范围先减小后增大。
（a）加工间隙随着𝑓，𝐴= 0.2 MPa而变化 （b）加工间隙随着𝐴，𝑓= 5 Hz而变化
图7：脉动参数对深孔钻探的影响。
在ECD中，正面加工间隙处的电解液对粘附的絮状副产物产生压制压力。这种效果使得副产品的去除变得困难，并且它们中的一些粘附到墙内的孔。当施加脉动流时，在加工间隙中产生周期性的低压区域，这降低了由于电解质造成的压紧压力。随着脉动频率和振幅的增加，副产物去除率增加。加工间隙中的电解质电导率接近于入口处新鲜电解质的电导率，并且电导率分布也是均匀的[15]。因此，加工间隙增加，间隙范围减小。然而，当频率大于5Hz时，该加工系统的响应时间被细长管电极和电解质液体的惯性延迟。此外，实验结果还表明，当脉动频率增加时，电极头会振动，加工过程不稳定，频繁发生短路。这是由于这样的事实，即特定的引导装置被限制为当脉动频率增加时限制工具的振动，特别是当电极长时间超出引导装置时。所有这些都会对加工间隙偏差产生不利影响。
当脉动幅度大于0.3MPa且时间在3/4时，入口处的电解液压力几乎为零。 电解液入口和出口之间存在零压差，并且由电解液流动驱动的副产物去除停止。 随着工具进入孔中，这种现象变得更糟，这会对孔特性产生不利影响。
从结果中选择一组最佳的脉动流量参数。 当频率为5Hz，振幅为0.2MPa，平均压力为0.5MPa时，得到25μm的最小加工间隙偏差。
4.4 施加电压对深孔钻削的影响
图8显示了施加电压分别对恒定流量和脉动流量的深孔钻削的影响。 恒定压力为0.5MPa，脉动流频率为5Hz，振幅为0.2MPa，平均压力为0.5MPa。 电压在22和25V之间变化。电极馈送速率为0.6mm / min。
图8（a）显示了施加电压对加工间隙和最大加工深度的影响。 图8（b）显示了对加工间隙范围的影响。 在这两种流动条件下，随着施加电压的增加，平均的加工间隙，加工间隙范围和最大加工深度都增加。 当电压升高时，电流密度增加，单位时间的材料去除量增加，这意味着更大的加工间隙。
通过比较相同电压下的结果，可以得出脉动流动加工间隙与恒定流动加工间隙几乎相同，而加工间隙范围减小的结论。 即加工精度提高。 此外，脉动流的最大加工深度明显优于恒定流的加工深度。 当电压为22 V时，以恒定流量钻出的孔具有0.159 mm的间隙和0.016 mm的间隙范围，而钻有脉动流的孔具有0.161 mm的间隙和0.013 mm的间隙范围。 带有脉动流的加工深度为12.5毫米，比恒定流量（10.4毫米）深约20％。 当电压为24 V时，脉动流的最大加工深度为20 mm，比恒流（15.3 mm）深30％。
4.5 电极进给速度对深孔钻削的影响
图9分别显示了电极进给速率对恒定流量和脉动流量深孔钻削的影响。 恒定压力是0.5MPa。 脉动流频率为5Hz，振幅为0.2MPa，平均压力为0.5MPa。 电极进给速率在0.6,0.8和1.0毫米/分钟之间变化。 施加的电压是24 V.
图9（a）显示了电极进给速度对加工间隙和最大加工深度的影响。 图9（b）显示了对加工间隙范围的影响。 在这两种流动条件下，随着电极进给速率的增加，平均加工间隙，加工间隙范围和最大加工深度都减小。 当电极进给速率增加时，每单位长度电流攻击工件的时间减少，材料去除量减小，这意味着较小的加工间隙。
比较相同电极进给速度下的结果，脉动流的最大加工深度明显优于恒定流的加工深度。 当进给速率为0.6毫米/分钟时，带脉动流的加工深度为20毫米，比恒流（15.5毫米）深30％。
4.6 钛合金深孔钻削
从第4节中的结果可以得出结论，使用高电压和低电极进给速率的参数组有助于提高最大加工深度。 另外，脉动流动对于提高最大加工深度和深孔直径的均匀性是有效的。 利用5Hz频率，0.2MPa振幅，0.5MPa平均压力，25V施加电压和0.6mm / min电极进给速率的优化参数，在钛中机加工了深20mm深和平均直径1.97mm的深孔 合金，如图10所示。
5结论
本文提出了一种脉动电解液流动的电化学钻井方法，并对脉动流动对深孔钻削的影响进行了实验研究。 结论可概括如下。
（1）随着正弦规则变化的脉动流动对于加速副产物去除和减少絮凝产物与孔内壁的粘附是有效的。
（2）脉动频率和振幅的正确增加可以提高副产物的去除率和加工间隙的均匀性，但过高的增加对工艺稳定性有害。
（3）在提高最大加工深度和加工精度方面，脉动流量优于恒定流量。
致谢
作者感谢国家自然科学基金和江苏省自然科学基金提供的财政支持。
9
Electrochemical Drilling of Deep Small Holes in Titanium Alloys with Pulsating Electrolyte Flow
1. Introduction
Deep small holes with considerable aspect ratios, such as cooling holes in turbine blades and vanes, have been widely applied in the aerospace field [1, 2]. These holes are typically made of nickel-based super alloys, titanium alloys, and intermetallic compounds, which are difficult-to-work-with mechanical machining technologies. Nontraditional machining technologies are mostly used, regardless of the mechanical properties of the materials. Laser drilling and electric discharge machining (EDM) produce recast layers on the surface, which must be subsequently removed in applications demanding a specific surface finish. Additionally, with the increase of machining depth, tool wear in EDM worsens and the machining efficiency reduces. Electrochemical drilling (ECD) can achieve high surface quality with an absence of tool wear and metallurgical defects. The inherent characteristics of ECD mean that it can be a major solution for machining deep small holes in difficult-to-cut materials [3, 4].
In industrial applications, acid solutions are developed to avoid the formation of insoluble hydroxides from dissolved metal ions. However, the environmental treatment of acid effluent is expensive. Therefore, many efforts have been made to replace acid solutions with neutral salt solutions [5–7]. In neutral aqueous solutions, the electrolytic products typically cohere into a flocculent structure in deep hole drilling. Delayed sludge removal may block the electrolyte passage, bridge the connection between the electrodes, and induce short circuits. By-product removal in ECD with neutral salt solutions therefore determines the accuracy of control and limits the process capacity. Various approaches have also been proposed to accelerate the electrolytic refreshment.
Skoczypiec [8] found that electrode ultrasonic vibrations change the conditions of electrochemical dissolution. The electrolyte flow, as well as electrode polarization, was enhanced by turbulent cavitations. Rajurkar and Zhu [9] applied an orbital motion to the tool cathode, which periodically expanded the side machining gap and made by-product removal easier. Hewidy [10] found that low-frequency vibrations of the tool cathode changed the physical condition in the frontal machining gap and extruded the electrolyte. Guo [11] invented a coaxial method by pumping in fresh electrolyte and extracting by-products at the hole entrance to restrict the submerged region and reduce the waste removal.
Figure 1: Schematic diagram of ECD with pulsating flow
Li et al. [12] progressively increased the electrolyte pressure in deep hole drilling to maintain a necessary electrolyte velocity for by-product removal. However, this issue has not been satisfactorily solved.
Pulsating flow, which creates periodic fluctuations of fluid flow and alters the thickness of the boundary layer, has been verified as effective in multiphase flow [13, 14]. However, there are limited studies on pulsating flow in electrochemical drilling.This work focuses on the improvement of by-product removal in deep hole drilling with pulsating electrolyte flow. Experiments are also carried out to study the effects of pulsation parameters on by-product removal rate, hole performance, and maximum machining depth in drilling of titanium alloys.
2. Principles of ECD with Pulsating Electrolyte Flow
Figure 1 shows a schematic diagram of ECD with pulsating electrolyte flow. Different from the typical ECD process with a constant flow, pulsating flow is an unsteady flow characterized by periodic fluctuation of the mass flow rate and pressure. Typical stimulus signals for pressure pulsation are presented in Figure 2. 𝑇 and 𝐴 denote the pulsation period and amplitude, respectively, and 𝑝av is the averaged electrolyte pressure over the pulsation period. In ECD with pulsating electrolyte flow, the workpiece is electrically connected to the positive pole of a pulse power supply and the tube tool is connected to the negative pole.The pulsating electrolyte with a velocity of 10–30 m/s is pumped into the interelectrode gap from the hollow center of the tube tool. When the tool electrode is fed at a constant rate into the workpiece, the material is dissolved, forming the desired hole. The perturbation and turbulence of pulsating flow intensely agitate the electrolyte mixed with insoluble sludge and bubbles. Agitation makes the products disperse more quickly and the distribution more uniform. When the pulsating flow is applied, a periodical low-pressure area is created in the machining gap, which reduces the hold-down pressure caused by the electrolyte on the by-products and enhances the refreshment of the electrolyte. As a result, process stability for deep hole drilling and hole quality can be enhanced.
3. System for ECD with Pulsating Electrolyte Flow
A specific system for drilling deep holes, equipped with pulsating electrolyte flow, is shown in Figure 3. This machining system consists of an electrochemical drilling machine, a pulsating pressure generator, an electrolyte circulatory system, a tool cathode guiding apparatus, and a power supply. The self-developed drilling machine can achieve precise feed in the 𝑋-𝑌-𝑍-axis. In trial tests of this system, it is found that the tube electrode was forced to vibrate with the pulsating flow. In this case, the tube electrode acts like a cantilever beam and the vibration amplitude of the electrode tip was amplified with the increase of the pulsating frequency. The vibration Advances in Mechanical Engineering generated by pulsating flow would be harmful to the machining. So, a guiding apparatus is designed to restrict the tool’s vibration and enhance the hole profile cylindricity in the feeding direction.
The pulsating flow is generated by a servo-controlled module, which is connected in series in the electrolyte circulatory system. This servo system is composed of an energy accumulator, a servo valve, a controller chip, a filter, and a power unit, as shown in Figure 4. The core component of this module is a Get-type electrohydraulic servo valve (RT6615E, Radk-Tech, China), which can quickly respond to a broadband stimulus signal ranging from 0 to 100 Hz. The outflow of this valve varies with the position of the valve core, which is controlled by the stimulus signals. A real-time full feedback control system was established to set the stimulus signals and acquire the electrolyte pressure.
4. Experimental Results and Discussions
4.1. Selection of Stimulus Signals.
Experiments were conducted to check the dynamic responses of the pulsating pressure servo system to typical stimulus signals, which are shown in Figure 2. Real-time electrolyte pressure at the outlet of the servo system was recorded and is presented in Figure 5. When the stimulus signals were at a frequency of 40 Hz, the electrolyte pressure consistently varied with the fluctuation of the signals. When sinusoidal and triangular waves were encouraged, the details of the original signals were maintained. However, distortions were observed when sawtooth waves and rectangular waves were driven. This servo system operates through mechanical actions of the servo valve core. Mechanical systems have inherent characteristics of coupling delay and filtering of high-frequency harmonics, which cause signal losses or jumping signals, such as sawtooth and rectangular waves. Hence, sinusoidal waves, which approximate to the fundamental wave, were selected to drive the pulsating electrolyte flow in the following experiments.
4.2. Effects of Pulsating Flow on Product Removal.
Samples of Ti6Al4V with a thickness of 20 mm were electrochemically drilled with different electrolyte flow conditions to study the effects of pulsating flow on by-product removal. In this experimental set, we applied a voltage of 26 V and an electrode feed rate of 0.6 mm/min. The other machining parameters are listed in Table 1. Immediately after the experiments and before cleaning, the samples were observed using a 3D video microscope (DVM5000, Leica, Germany). The entrance characteristics of the deep drilled holes are presented in Figure 6. The hole shown in Figure 6(b) was machined with a constant electrolyte pressure of 0.4 MPa. Massive white electrolytic products were observed on the hole’s inside surface.The holes in Figures 6(c) to 6(f) were drilled with a pulsating electrolyte at amplitude of 0.2 MPa. The pulsating frequencies were 2, 5, 8, and 10 Hz, respectively. It is obvious that when pulsating flow is applied, the residual products are mostly decreased.
Figure 4: Servo system for pulsating pressure.
When titanium and its alloys are dissolved, ions are diffused into the electrolyte and form TiO2, which is insoluble and easily coheres into a flocculent structure. Furthermore, TiO2 is hydrophilic and adhesive and may adhere to the hole inside surface and block the electrolyte passage. These characteristics are harmful to further material dissolution and to process stability. From the results presented in Figure 6, it can be concluded that pulsating electrolyte flow is effective in reducing residual by-products on the machined surface and accelerating their removal.
4.3. Parametric Effects of Pulsating Flow on Hole Performance.
In this section, parametric experiments were carried out to study the effects of pulsation frequency and amplitude on deep hole drilling. Figure 7 shows the variations of the machining gap with pulsation parameters. It shows that when the pulsation frequency and amplitude increase, the machining gap firstly increases and then decreases, while the range of the machining gap firstly decreases and then increases.
(a) Machining gap varied with 𝑓, 𝐴 = 0.2 MPa (b) Machining gap varied with 𝐴, 𝑓=5 Hz
Figure 7: Effects of pulsation parameters on deep hole drilling.
In ECD, the electrolyte at the front machining gap creates a hold-down pressure on the cohered flocculent by-products. This effect makes the removal of the by-products difficult, and some of them adhere to the hole inside wall. When pulsating flow is applied, a periodical low-pressure area is created in the machining gap, which reduces the hold-down pressure due to the electrolyte. With increasing pulsation frequency and amplitude, the by-product removal rate increases. The electrolyte conductivity in the machining gap is then much closer to the conductivity of fresh electrolyte at the inlet, and the conductivity distribution is also uniform [15]. Therefore, the machining gap increases and the gap range decreases. However, when the frequency is greater than 5 Hz, the response time of this machining system is delayed by the slender tube electrode and the inertia of the electrolyte liquid. Moreover, the experimental results also indicated that when the pulsating frequency increases, the electrode tip will vibrate and the machining process is unstable and short circuits took place frequently. It is due to the fact that the specified guiding apparatus is limited to restrict the tool’s vibration as the pulsating frequency increases, especially when the electrode is fed long beyond the guiding apparatus. All these adversely affect the machining gap deviation.
When the pulsation amplitude is larger than 0.3 MPa and the time is at 3/4 period, the electrolyte pressure at the inlet is nearly zero. Zero pressure difference exists between the electrolyte inlet and outlet and by-product removal driven by the electrolyte flow stops. As the tool feeds into the hole, this phenomenon becomes worse, which adversely affects the hole characteristics.
From the results, an optimal group of pulsating flow parameters is selected. When the pulsating flow is 5 Hz in frequency, 0.2 MPa in amplitude, and 0.5 MPa in average pressure, a minimum machining gap deviation of 25 𝜇m is obtained.
4.4. Effects of Applied Voltage on Deep Hole Drilling.
Figure 8 shows the effects of applied voltage on deep hole drilling with constant flow and with pulsating flow, respectively. The constant pressure is 0.5 MPa, while the pulsating flow is 5 Hz in frequency, 0.2 MPa in amplitude, and 0.5 MPa in average pressure. The voltage varies between 22 and 25 V. The electrode feed rate is 0.6 mm/min.
Figure 8(a) shows the effects of applied voltage on the machining gap and the maximum machining depth. Figure 8(b) shows the effects on the machining gap range. In both of these two flow conditions, with increasing applied voltage, the averaged machining gap, the machining gap range, and the maximum machining depth all increase. When the voltage is increased, the current density increases and the material removal volume per unit time increases, which means a larger machining gap.
Comparing the results obtained with the same voltage, it can be concluded that the machining gap drilled with pulsating flow is nearly the same as that with constant flow, while the machining gap range decreases; that is, the machining accuracy is improved. Furthermore, the maximum machining depth with pulsating flow is obviously superior to that with constant flow. When the voltage is 22 V, the hole drilled with the constant flow has a 0.159 mm gap and a 0.016 mm gap range, while the hole drilled with the pulsating flow has a 0.161 mm gap and a 0.013 mm gap range. The machined depth with pulsating flow is 12.5 mm, which is about 20% deeper than that with constant flow (10.4 mm). When the voltage is 24 V, the maximum machined depth with pulsating flow is 20 mm, which is 30% deeper than that with constant flow (15.3 mm).
4.5. Effects of Electrode Feed Rate on Deep Hole Drilling.
Figure 9 shows the effects of electrode feed rate on deep hole drilling with constant flow and with pulsating flow, respectively. The constant pressure is 0.5 MPa. The pulsating flow is 5 Hz in frequency, 0.2 MPa in amplitude, and 0.5 MPa in averaged pressure. The electrode feed rate varies between 0.6, 0.8, and 1.0 mm/min. The applied voltage is 24 V.
Figure 9(a) shows the effects of electrode feed rate on the machining gap and the maximum machining depth. Figure 9(b) shows the effects on the machining gap range. In both of these two flow conditions, with increasing electrode feed rate, the averaged machining gap, the machining gap range, and the maximum machining depth all decrease. When the electrode feed rate is increased, the time in which the current attacks the workpiece per unit length decreases and the material removal volume decreases, which means a smaller machining gap.
Comparing results for the same electrode feed rate, the maximum machining depth with pulsating flow is obviously superior to that with constant flow. When the feed rate is 0.6 mm/min, the machined depth with pulsating flow is 20 mm, which is about 30% deeper than that with constant flow (15.5 mm).
4.6. Drilling of Deep Hole in Titanium Alloy.
From the results presented in Section 4, it can be concluded that using a parameter group with a high voltage and a low electrode feed rate contributes to enhancing the maximum machining depth. In addition, pulsating flow is effective in enhancing the maximum machining depth and the homogeneity of the deep hole diameter. With the optimized parameters of 5 Hz frequency, 0.2 MPa amplitude, 0.5 MPa average pressure, 25 V applied voltage, and 0.6 mm/min electrode feed rate, a deep hole of 20 mm in depth and 1.97 mm in average diameter was machined in titanium alloys, as shown in Figure 10.
5. Conclusions
This paper proposed a method of electrochemical drilling with pulsating electrolyte flow, and the effects of pulsating flow on deep hole drilling were experimentally investigated. The conclusions can be summarized as follows.
(1) Pulsating flow varying with the sinusoidal rule is effective in accelerating by-product removal and in reducing the adhesion of flocculent products to the hole inside wall.
(2) The correct increase of pulsation frequency and amplitude could enhance by-product removal and the homogeneity of the machining gap, but an excessive increase is harmful to the process stability.
(3) Pulsating flow is superior to constant flow in enhancing both maximum machining depth and machining accuracy
Conflict of Interests
The authors declare that there is no conflict of interests regarding the publication of this paper.
Acknowledgments
The authors acknowledge the financial support provided by the National Natural Science Foundation of China (51175258) and the Jiang Su Natural Science Foundation (BK20131361).
References
[1] R. S. Bunker, “A review of shaped hole turbine film-cooling technology,” Journal of Heat Transfer, vol. 127, no. 4, pp. 441–453, 2005.
[2] M. Sen and H. S. Shan, “A review of electrochemical macro- to micro-hole drilling processes,” International Journal of Machine Tools and Manufacture, vol. 45, no. 2, pp. 137–152, 2005.
[3] K. P. Rajurkar, D. Zhu, J. A. McGeough, J. Kozak, and A. de Silva, “New developments in electro-chemical machining,” CIRP Annals: Manufacturing Technology, vol. 48, no. 2, pp. 567– 579, 1999.
[4] X. Fang, N. Qu, H. Li, and D. Zhu, “Enhancement of insulation coating durability in electrochemical drilling,” International Journal of Advanced Manufacturing Technology, vol. 68, no. 9– 12, pp. 2005–2013, 2013.
[5] W.Wang, D. Zhu, N. S. Qu, S. F. Huang, and X. L. Fang, “Electrochemical drilling with vacuum extraction of electrolyte,” Journal of Materials Processing Technology, vol. 210, no. 2, pp. 238–244, 2010.
[6] M. S. Hewidy, S. J. Ebeid, K. P. Rajurkar, and M. F. El-Safti, “Electrochemical machining under orbital motion conditions,” Journal of Materials Processing Technology, vol. 109, no. 3, pp. 339–346, 2001.
[7] W. Wang, D. Zhu, N. Qu, S. Huang, and X. Fang, “Electrochemical drilling inclined holes using wedged electrodes,” International Journal of Advanced Manufacturing Technology, vol. 47, no. 9–12, pp. 1129–1136, 2010.
[8] S. Skoczypiec, “Research on ultrasonically assisted electrochemical machining process,” International Journal of Advanced Manufacturing Technology, vol. 52, no. 5–8, pp. 565–574, 2011.
[9] K. P. Rajurkar and D. Zhu, “Improvement of electrochemical machining accuracy by using orbital electrode movement,” CIRP Annals: Manufacturing Technology, vol. 48, no. 1, pp. 139– 142, 1999.
[10] M. S. Hewidy, S. J. Ebeid, T. A. El-Taweel, and A. H. Youssef, “Modelling the performance of ECM assisted by low frequency vibrations,” Journal of Materials Processing Technology, vol. 189, no. 1–3, pp. 466–472, 2007.
[11] J. C. Guo, Study on Micro electrochemical machining using coaxial for gushing and sucking method [M.S. thesis], National Yunlin University of Science & Technology, 2007, (Chinese).
[12] Z. Li, D. Wei, and S. C. Di, “Research on electrochemical machining small hole in variable pressure field using tubular electrode,” Electromachining & Mould, no. 5, pp. 30–32, 2011 (Chinese).
[13] X. Fang, N. Qu, Y. Zhang, Z. Xu, and D. Zhu, “Effects of pulsating electrolyte flow in electrochemical machining,” Journal of Materials Processing Technology, vol. 214, no. 1, pp. 36–43, 2014.
[14] E. M. Benavides, “Heat transfer enhancement by using pulsating flows,” Journal of Applied Physics, vol. 105, no. 9, Article ID 094907, 2009.
[15] N. S. Qu, X. L. Fang, Y. D. Zhang, and D. Zhu, “Enhancement of surface roughness in electrochemical machining of Ti6Al4V by pulsating electrolyte,” International Journal of Advanced Manufacturing Technology, vol. 69, no. 9–12, pp. 2703–2709, 2013
脉冲电解液流动钛合金深小孔的电化学钻削
1.简介
具有相当高宽比的深孔，如涡轮叶片和叶片上的冷却孔已广泛应用于航空航天领域[1,2]。这些孔通常由镍基超合金，钛合金和金属间化合物制成，这些材料难以用机械加工技术加工。不管材料的机械性能如何，大多数都使用非传统加工技术。激光钻孔和放电加工（EDM）在表面上产生重铸层，必须随后在需要特定表面抛光的应用中去除重铸层。此外，随着加工深度的增加，电火花加工中的刀具磨损恶化，加工效率降低。电化学钻孔（ECD）可以达到较高的表面质量，不会出现刀具磨损和冶金缺陷。 ECD的固有特性意味着它可以成为在难切削材料中加工深孔的主要解决方案[3,4]。
在工业应用中，开发酸
收藏