基于GA-GRNN的AWJ强化3D打印AlSi10Mg表面性能实验研究

为提高磨料水射流(Abrasive Water Jet,AWJ)强化工艺对3D打印AlSi10Mg表面性能的强化效果预测的准确性及高效性,首先开展磨料水射流强化AlSi10Mg表面强化实验;然后分别以表面硬度和表面残余应力作为目标,基于遗传算法-广义回归神经网络(Genetic Algorithm-Generalized Ragression Neural Network,GA-GRNN)对实验数据样本进行训练,建立3D打印AlSi10Mg表面性能预测模型;最后,利用遗传算法对建立的神经网络预测模型中的AWJ强化主要参数进行优化。研究结果表明,经过磨料水射流强化后的AlSi10Mg表面硬度与表面残余应力均得到有效提高;建立的GA-GRNN预测模型与校验值误差在2.3%以内,具有较高的准确性;经遗传算法优化后,得到表面硬度最佳参数组合:射流压力为33 MPa,磨料粒径为0.15 mm,靶距为12.4 mm,此时表面硬度为159.25HV;表面残余应力最佳参数组合:射流压力为40 MPa,磨料粒径为0.13 mm,靶距为15 mm,此时表面残余应力为-137.4 MPa。为后续磨料水射流强化零件表面的参数选择提供数据支撑。

陶瓷等脆硬板材的磨粒水射流(AWJ)切割技术

陶瓷等脆硬材料板材在普通方法切割加工时容易破碎,也不能切割加工出特别复杂的形状和图案。分析磨料水射流技术原理和材料去除机理,重点介绍几种脆硬材料的水磨料射流切割应用示例,并总结其技术优势和推广意义。

Endoscopic transluminal pancreatic necrosectomy using a self-expanding metal stent and high-flow water-jet system

Walled-off pancreatic necrosis and a pancreatic abscess are the most severe complications of acute pancreatitis. Surgery in such critically ill patients is often associated with significant morbidity and mortality within the first few weeks after the onset of symptoms. Minimal invasive approaches with high success and low mortality rates are therefore of considerable interest. Endoscopic therapy has the potential to offer safe and effective alternative treatment. We report here on 3 consecutive patients with infected walled-off pancreatic necrosis and 1 patient with a pancreatic abscess who underwent direct endoscopic necrosectomy 19-21 d after the onset of acute pancreatitis. The infected pancreatic necrosis or abscess was punctured transluminally with a cystostome and, after balloon dilatation, a non-covered self-expanding biliary metal stent was placed into the necrotic cavity. Following stent deployment, a nasobiliary pigtail catheter was placed into the cavity to ensure continuous irrigation. After 5-7 d, the metal stent was removed endoscopically and the necrotic cavity was entered with a therapeutic gastroscope. Endoscopic debridement was performed via the simultaneous application of a high-flow water-jet system; using a flush knife, a Dormia basket, and hot biopsy forceps. The transluminal endotherapy was repeated 2-5 times daily during the next 10 d. Supportive care included parenteral antibiotics and jejunal feeding. All patients improved dramatically and with resolution of their septic conditions; 3 patients were completely cured without any further complications or the need for surgery. One patient died from a complication of prolonged ventilation severe bilateral pneumonia, not related to the endoscopic procedure. No procedure related complications were observed. Transluminal endoscopic necrosectomy with temporary application of a self-expanding metal stent and a high-flow water-jet system shows promise for enhancing the potential of this endoscopic approach in patients with walled-off pancreatic necrosis and/or a pancreatic abscess.

Formation Control for Water-Jet USV Based on Bio-Inspired Method

The formation control problem for underactuated unmanned surface vehicles(USVs) is addressed by a distributed strategy based on virtual leader strategy. The control system takes account of disturbance induced by external environment. With the coordinate transformation, the advantage of the proposed scheme is that the control point can be any point of the ship instead of the center of gravity. By introducing bio-inspired model, the formation control problem is addressed with backstepping method. This avoids complicated computation, simplifies the control law,and smoothes the input signals. The system uniform ultimate boundness is proven by Lyapunov stability theory with Young inequality. Simulation results are presented to verify the effectiveness and robust of the proposed controller.

Natural orifice transluminal endoscopic wedge hepatic resection with a water-jet hybrid knife in a non-survival porcine model

AIM: To explore the feasibility of a water-jet hybrid knife to facilitate wedge hepatic resection using a natural orifice transluminal endoscopic surgery (NOTES) approach in a non-survival porcine model. METHODS: The Erbe Jet2 water-jet system allows a needleless, tissue-selective hydro-dissection with a pre-selected pressure. Using this system, wedge hepatic resection was performed through three natural routes (trans-anal, trans-vaginal and trans-umbilical) in three female pigs weighing 35 kg under general anesthesia. Entry into the peritoneal cavity was via a 15-mm incision using a hook knife. The targeted liver segment was marked by an APC probe, followed by wedge hepatic resection performed using a water-jet hybrid knife with the aid of a 4-mm transparent distance soft cap mounted onto the tip of the endoscope for holding up the desired plane. The exposed vascular and ductal structures were clipped with Endoclips. Hemostasis was applied to the bleeding cut edges of the liver parenchyma by electrocautery. After the procedure, the incision site was left open, and the animal was euthanized followed by necropsy. RESULTS: Using the Erbe Jet2 water-jet system, trans-anal and trans-vaginal wedge hepatic resection was successfully performed in two pigs without laparoscopic assistance. Trans-umbilical attempt failed due to an unstable operating platform. The incision for peritoneal entry took 1 min, and about 2 h was spent on excision of the liver tissue. The intra-operative blood loss ranged from 100 to 250 mL. Microscopically, the hydro-dissections were relatively precise and gentle, preserving most vessels. CONCLUSION: The Erbe Jet2 water-jet system can safely accomplish non-anatomic wedge hepatic resection in NOTES, which deserves further studies to shorten the dissection time.

Trans-umbilical endoscopic cholecystectomy with a water-jet hybrid-knife:A pilot animal study

AIM:To investigate the feasibility and safety of Natural orifice trans-umbilical endoscopic cholecystectomy with a water-jet hybrid-knife in a non-survival porcine model.METHODS:Pure natural orifice transluminal endoscopic surgery(NOTES) cholecystectomy was performed on three non-survival pigs,by transumbilical approach,using a water-jet hybrid-knife. Under general anesthesia,the following steps detailed the procedure:(1) incision of the umbilicus followed by the passage of a double-channel flexible endsocope through an overtube into the peritoneal cavity;(2) establishment of pneumoperitoneum;(3) abdominal exploration;(4)endoscopic cholecystectomy:dissection of the gallbladder performed using water jet equipment,ligation of the cystic artery and duct conducted using nylon loops;and(5) necropsy with macroscopic evaluation.RESULTS:Transumbilical endoscopic cholecystectomy was successfully completed in the first and third pig,with minor bleedings. The dissection times were 137and 42 min,respectively. The total operation times were 167 and 69 min,respectively. And the lengths of resected specimen were 6.5 and 6.1 cm,respectively.Instillation of the fluid into the gallbladder bed produced edematous,distended tissue making separation safe and easy. Reliable ligation using double nylon loops insured the safety of cutting between the loops.There were no intraoperative complications or hemodynamic instability. Uncontrolled introperative bleeding occurred in the second case,leading to the operation failure.CONCLUSION:Pure NOTES trans-umbilical cholecystectomy with a water-jet hybrid-knife appears to be feasible and safe. Further investigation of this technique with long-term follow-up in animals is needed to confirm the preliminary observation.

Water-Jet Cavitation Shock Bulging as Novel Microforming Technique

With the continuous expansion of the application range of microelectromechanical systems,microdevice forming technology has achieved remarkable results.However,it is challenging to develop new microforming processes that are low cost,environmentally friendly,and highly flexible;the high-energy shock wave in a cavitation bubble's collapse process is used as the loading force.Herein,a new process for the microbulging of the water-jet cavitation is proposed.A series of experiments involving the water-jet cavitation shock microbulging process for TA2 titanium foil is performed on an experimental system.The microforming feasibility of the water-jet cavitation is investigated by characterizing the shape of the formed part.Subsequently,the effects of the main parameters of the water-jet cavitation on the bulging profile,forming depth,surface roughness,and bulging thickness distribution of TA2 titanium foil are revealed.The results show that the plastic deformation increases nonlinearly with the incident pressure.When the incident pressure is 20 MPa,the maximum deformation exceeds 240 pm,and the thickness thinning ratio changes within 10%.The microbulging feasibility of water-jet cavitation is verified by this phenomenon.

The Propulsive Force of the Water-jet to the Flying Weft in Water-jet Looms

In order to study the propulsive force on the water-jet to the flying weft in water-jet looms, a dynamic model has been established. Based on the analysis and example testing, an experiential formula of the propulsive force of the water-jet to the flying weft is obtained for the first time. The formula will profit the further research of the water-jet weft insertion and the production of textile.

Influence of long and short guide vanes on hydraulic performance of water-jet pump

Different guide vane structures will affect the flow inside the pump,and then affect the transformation of the pressure energy and kinetic energy,and change the velocity distribution of the pump outlet.In order to study the influence of long and short guide vanes on the water-jet pump,on the basis of conventional design,eight schemes of guide vane with different vertical heights were designed in the method of computational fluid dynamics for numerical calculation,the performance curve of water-jet pumps with different long and short guide vanes was obtained,and finally the influence of different guide vanes on hydraulic performance and internal flow was analyzed.The results show that all of schemes reducing the height of blade can improve the head and efficiency.In the schemes reducing the height on the shroud,the guide vanes that the height of the blade is equal to the height difference between hub and shroud in impeller have the highest head and efficiency.In all schemes decreasing the blade height,with the increase of the height difference,the velocity increases gradually and the distribution of turbulence kinetic energy becomes more reasonable in the guide vane outlet.The schemes reducing the height on the hub have more reasonable distribution of velocity and turbulence kinetic energy according to schemes reducing the height on the shroud.The guide vanes of long and short blades can be used to stagger the position of the diffusion flow generated by adjacent blades,which can reduce the effect of the velocity circulation and make the flow of the outlet position more stable.

Study of Water Jet Impulse in Water-Jet Looms

The watar jet impulse is brought forward to study the traction force of the water jet to the flying weft in water-jet looms. The distribution of the water jet impulse in the shed is tested by a sensor, and the influence of water jet parameters on the water jet impulse is analyzed.

Prediction and Analysis of Surface Quality of Northeast China Ash Wood during Water-Jet Assisted CO_(2) Laser Cutting

As a natural and environmentally friendly renewable material,Northeast China ash wood(NCAW)(Fraxinus mandshurica Rupr.)was cut by water-jet assisted CO_(2) laser(WACL),the surface quality was evaluated by surface roughness of cut section.The surface roughness was measured by three-dimensional(3D)profilometry.Furthermore,the micromorphology of machined surface was observed by scanning electronic microscopy(SEM).Carbon content changes of machined surface were measured by energy dispersive spectrometer(EDS).A relationship between surface roughness and cutting parameters was established using response surface methodology(RSM).It is concluded that the cutting speed,laser power and water pressure played an important role in surface roughness of cut section.The surface roughness increased as an increase in laser power.It decreased caused by increasing of cutting speed and water pressure.Measurements revealed that the surface quality of NCAW part was improved using the optimized combination of cutting parameters.The established quadratic mathematical model of a good prediction is helpful for matching suitable cutting parameters to obtain expected surface quality.

AWJ射流对加工质量的影响

AWJ(磨料水射流)加工的主要先进性,是对某些工件的加工可以满足一般的工艺要求,省却二次加工.因此,切割后的切口质量一直是研究的重点.

英国AWJ发布中国尼龙市场报告

英国AWJ咨询公司发布的一项新的研究显示，中国市场对尼龙聚合物和复合改性材料的需求和供给持续上升。该报告主要侧重于尼龙6、尼龙6／6和高温尼龙。中国市场对尼龙改性材料的需求在2012年达到894，500吨，预计在未来五年内平均每年增长7．5％，2017年将达到近130万吨的市场需求。在过去三年中，中国的尼龙市场的年平均增长率为11．2％。

The kinematic Design of Beating-up Mechanism for Water-jet Loom Series Modified from Air-jet Loom

For Toyoda looms with air-jet weft insertion,the beat-ing-up mechanisms together with those of Tsudakomawater-jet looms are analyzed.Then by changing thecrank length of the four-bar-linkage for the air-jetlooms to get four specifications of reed travel correspond-ing to the series of Tsudakoma water-jet looms,it canbe proved by comparisons of displacements,velocities,accelerations and transmission pressure angles that thosetwo series of mechanisms have very similar kinematicproperties.So the possibility of developing a series of wa-ter-jet looms modified from Toyoda air-jet looms isproved.It is beneficial to save the machine cost andbroaden the machine types.

前混合式磨料水射流喷嘴外流场仿真与实验

通过建立磨料水射流喷嘴有限元模型，对2种不同直径的前混合式磨料水射流的喷嘴外流场进行仿真分析．结果表明，在喷嘴其它几何条件相同的情况下，出口直径对喷嘴的出口速度影响比较大，出口直径越大，出口速度越小；在一定程度上将混合管适当地加长，可以提高磨料射流在喷嘴出口处的速度；磨料水射流最佳的切割距离为喷嘴出1：7直径的2．0—5．0倍．磨料水射流切割靶体实验结果与靶体冲击仿真结果基本吻合．

磨料水射流切割碳纤维复合材料的表面粗糙度试验

采用超高压磨料水射流技术对碳纤维复合材料进行切割试验,借助μscan激光共聚焦显微镜重构样品切口的三维表面,测得样品切口表面粗糙度;研究了扫描分辨率对表面粗糙度测量的影响,以及切割速度、样品厚度对样品切口表面粗糙度的影响规律。试验结果表明:扫描分辨率对表面粗糙度的测量无明显的影响;当切割深度较小(0～0.6 mm)时,即在切口入口处,表面粗糙度随切割深度的增大而减小,当切割深度较大(大于0.6 mm)时,表面粗糙度随切割深度的增大而增大;当样品厚度一定时,随着切割速度的增大,切口最大表面粗糙度在整体趋势上是增大的,而样品厚度的大小对表面粗糙度的影响并无明显的规律。

前混合磨料水射流切割技术在诱导顶板垮落中的应用

对前混合磨料水射流切割技术在诱导顶板垮落中的应用进行了研究,分析了该技术在井下应用的可行性和安全性。研制了用于井下诱导顶板垮落的磨料水射流切割设备并进行了现场应用试验。该设备可以顺利切割井下锚索锁具,从而诱导上隅角位置坚硬顶板实现自然垮落,防止上隅角位置顶板大面积悬空引起瓦斯积聚造成的安全隐患。前混合磨料水射流切割技术使用方便,安全高效,在井下安全生产中具有广阔的应用前景。

磨料水射流钻削深小盲孔的试验研究

论述用连续磨料水射流钻削深小孔的试验研究。磨料水射流的加工领域非常广泛,它可以在许多材料上进行加工,加工的主要优点是加工时不产生切削热,加工过程非常灵活。所采用的钻削加工是在不同材料上进行的,随着钻削时间的不同,可观察到钻孔的深度和直径都不同。孔的深度和直径与钻削时间呈幂函数关系增大。根据试验结果可以创建一个经验模型,预测在不同钻削时间,钻孔的深度和直径的大小。

基于CFD的磨料水射流水下切割研究

从工程实际应用的角度出发,运用理论研究、试验验证、软件仿真等手段,对前混合磨料高压水射流系统的水下切割技术进行机理分析及实验研究。

基于人工神经网络的磨料水射流切割加工模型

作为一种冷态加工新工艺 ,磨料水射流 (AWJ)以其独特的优点得到广泛应用 ,但由于高速液固两相流本身的特性 ,AWJ切割加工是一个受多参数影响的复杂随机过程 ,很难建立一个适当的机理模型。基于人工神经网络理论 ,本文建立了切割厚度与主要工艺参数间的AWJ切割加工预测模型 ,模型预测结果与实验值及Zeng的经验模型进行了比较 ,该网络模型能可靠、准确地映射出AWJ的加工规律 ,可应用于AWJ切割加工过程的参数优化选择、加工规律计算机仿真及智能化控制中。