前混合磨料水射流切割HTPB推进剂的可行性研究

针对前混合磨料水射流切割HTPB推进剂的过程安全性和效率，开展了理论分析与试验验证。在理论分析的结果上，分别开展了基于固定和移动两种试验模式下的安全性和效率试验。该切割方式由于有效降低了出口压力，在保证切割能力的前提下其冲击压力远远低于推进剂的冲击感度，导致推进剂内部升温不明显，安全性有足够保证。研究结果表明，在90%的置信水平下，切割的安全可靠度不低于99.52%。而磨料粒子的添加极大地提高了射流的切割效率。试验结果表明，当保持出口压力30 MPa以上、磨料质量分数不低于50%时，磨料水射流约为相同条件下纯水射流切割效率的2倍。由此得出可行性结论:由于前混合磨料水射流具有极强的冷态冲蚀磨削作用，在安全性和效率方面均能够满足对三组元HTPB推进剂的切割作业。     

磨料水射流强化18CrNiMo7-6钢工艺参数的优化设计

为探究磨料水射流技术强化18CrNiMo7-6钢的最优工艺参数,通过设计正交试验,采用X射线残余应力测试仪、粗糙度仪和HV-1000显微硬度计分别测量其残余应力、粗糙度、硬度,然后用直观分析方法对影响因素进行显著性排序。结果表明:多种因素影响磨料水射流的强化效果,其中水压影响最大,速率次之,靶距和进给量影响比较小。通过直观分析得到最优工艺参数组合为水压100 MPa,速率500 mm/min,进给量1.500 mm,靶距5mm。经优化的工艺参数组合,可以使试样表层具有较高的残余压应力值,同时具有比较理想的硬度和粗糙度,研究结果可为其他金属材料的磨料水射流强化方法提供参考。     

45钢表面喷丸强化工艺的模拟分析

为了研究高压水射流喷丸的工艺效果,选择合适的水射流喷丸工艺参数,利用ANSYS有限元仿真软件进行模拟分析,以玻璃为喷丸材料,45钢为靶体材料,采用LS-DYNA软件,建立喷丸与靶体的有限元模型,通过模拟喷丸冲击靶体的动态过程,得到弹坑的深度及最大残余压应力的分布情况,绘制工艺参数对弹坑深度以及最大残余压应力的关系曲线。结果表明:弹坑深度及最大残余压应力随着弹丸速度的增加而明显增加,而弹丸入射角度对于弹坑深度及最大残余压应力的影响则比较平缓;该仿真结果与试验结果相近。     

磨料水射流对脆性材料的冲蚀研究

磨料水射流技术作为一种特种加工技术，具有无刀具接触、无热影响区和加工范围广等优势，在众多领域得到应用。为了探究磨料水射流对脆性材料的冲蚀效果，构建和设计了磨料水射流外流场冲蚀仿真模型与磨料水射流冲蚀实验。以30 mm×50 mm的喷嘴外流场域为计算域，建立磨料水射流冲蚀仿真模型，并分析射流冲蚀过程中压力分布、水与磨料的速度分布及它们在射流中心线上的衰减规律。通过对氧化铝陶瓷材料的冲蚀实验，分析工艺参数对冲蚀孔径的影响，并结合仿真结果对比分析了射流束宽度与冲蚀孔径的关系。结果表明：水的速度随着喷嘴距离的增大而减小且分布范围变宽，射流宽度呈线性增大，磨料速度随喷嘴距离的增大而减小且分布范围基本不变；射流中心线上水的速度与磨料速度呈三段式衰减，水的第1段速度衰减段长度比磨料的长，但水的第2段速度衰减段长度比磨料的短；射流束能量的有效利用部分逐渐减小，但在15~25 mm的靶距范围内其有效利用部分较稳定，为40%；冲蚀孔径随喷嘴距离增大呈线性增大。研究结果为磨料水射流切割、铣削及抛光加工的参数选择提供实验依据，同时为磨料水射流加工过程仿真提供参考。     

基于大型钢铁工件磨料水射流除锈及工艺研究

设计了湿式送料后混合磨料水射流除锈装置,并对装置的主要除锈参数进行了研究。结果表明,喷射压力为40 MPa、磨料量为600 g/min、工件进给速度为2 000 mm/min、靶距为60 mm时,粗糙度R_a为4.51μm,工件表面光滑,满足加工要求。     

基于SPH-FEM耦合算法的后混合磨料水射流冲击破岩数值模拟研究

采用SPH-FEM(smoothed particle hydrodynamics with finite element method)模拟了后混合磨料水射流在喷嘴中的混合过程,并研究了射流速度、磨料浓度以及岩石围压等因素对后混合磨料水射流破岩效果的影响规律。研究结果表明:在柱塞推动下,水与磨料在喷嘴的混合段、收敛段与直线段分别获得加速,最终磨料的速度可增加至纯水速度的80%;岩石破碎深度随射流速度呈近似线性增加,而破碎宽度随射流速度变化不大;磨料射流较纯水射流的破岩损伤更加明显,岩石的损伤随磨料浓度呈先增大后减小的趋势;岩石的破碎深度随着围压的增加呈近似线性减小的趋势。数值模拟结果与破岩实验现象基本吻合,该研究结果可为磨料水射流破岩的应用提供一定的理论支撑。     

磨料水射流切割防暴弹的试验研究

针对前混合式磨料水射流切割防暴弹的过程,分析磨料水射流对装药的切割安全性,探讨射流参数的选取及工程化处废的可行性。根据弹性力学的固体接触理论,建立磨料水射流冲击弹体时的数学模型,从而选取射流出口压力等工艺参数。依据射流的冲击理论和装药的热感度及撞击感度,结合射流作用时的升温试验,分析证实在该射流参数下的冲击安全性。结果表明,以手投催泪(或发烟)弹、枪射催泪(或发烟)弹为代表的4种防暴弹,其试验结果与实例计算相吻合,切割安全可靠度不低于98.57%。该研究可为防暴弹的工程化处废提供理论依据和技术支持。     

高压磨料水射流切割破碎岩石的单轴力学特征研究EI北大核心CSCD

高压磨料水射流切割破碎后岩石的力学参数变化对于岩石的进一步破碎具有重要的影响。选取了砂岩、灰岩与花岗岩在水射流切割平台上开展了磨料射流冲击切割试验,对切割后的岩石进行CT扫描并重构岩石在不同冲击切割条件下的三维破碎形态,最后通过单轴压缩试验对比分析了岩石试件在磨料射流冲击切割前后的力学响应特征。研究结果表明:①在相同的射流参数条件下,岩石在磨料射流的移动切割下大多出现较为规整的缝槽形态,而定点冲击则出现孔洞破碎形态,前者比后者在岩石内部造成的损伤破碎程度更大;②磨料射流的冲击切割作用导致岩石试件在单轴压缩过程中出现折断型破碎形态的概率增加,且这种增加趋势随着切割长度的增加而愈加显著,但切割作用几乎不改变岩石试件的应力应变趋势;③岩石试件的单轴抗压强度与泊松比随切割长度与射流压力的增加呈现近似线性降低的趋势。该研究结果可为高压磨料水射流煤层割缝卸压的工程应用提供一定的理论指导。     

增压式脉冲水射流破碎硬岩性能研究

为进一步提高脉冲水射流破岩能力,提出了一种增压式脉冲水射流发生方法,以低输入压力获取高脉动压力。为检验增压式脉冲水射流的破碎硬岩性能,搭建了增压式脉冲水射流破碎硬岩试验系统,开展破岩试验,并结合数值模拟获取的流场细节信息,分析了不同喷嘴直径、射流压力、靶距对增压式脉冲水射流破碎硬岩性能的影响规律。结果表明：增压式脉冲水射流的破碎硬岩性能随喷嘴直径增加先增大后减弱;随射流压力升高,射流轴心速度增大,但因气、液能量交换加剧导致的能量损耗增加,当前试验条件下射流压力为60 MPa时破岩效果最好;破碎体积在100 mm靶距达到峰值,而最大破碎深度对应的最优靶距为25 mm和75 mm,逐渐向喷嘴回移。研究结果对推动增压式脉冲水射流工程应用具有重要指导意义。     

多线切割工艺对单晶锗损伤层及几何参数的影响

本工作集中研究磨料粒径、进给速度及切割线径对单晶锗片损伤层及几何参数的影响。结果表明:在切割过程中,磨料粒径与锗片损伤层深度及表面粗糙度呈正比关系,采用3 000#磨料切割时,损伤层深度为6μm,表面粗糙度为0.285μm;进给速度的降低会降低锗棒在切割过程中的温度变化,从而降低锗片的几何参数;采用3 000#碳化硅微粉,100μm/min进给速度,0.09 mm切割线的切割工艺,能够获得表面质量优异、几何参数小、切割损耗小的锗片。     

Multiresponse Optimization of Abrasive Water Jet Cutting Process Parameters Using TOPSIS Approach

This paper describes how optimization studies were carried out on an abrasive water jet (AWJ) cutting process with multiresponse characteristics based on Multi Criteria Decision Making Methodology (MCDM) using the Technique for Order Preference by Similarity Ideal Solution (TOPSIS) approach. The process parameters water jet pressure, traverse rate, abrasive flow rate, and standoff distance are optimized with multiresponse characteristics, including the depth of penetration (DOP), cutting rate (CR), surface roughness (R_a), taper cut ratio (TCR), and top kerf width (TKW). The optimized results obtained from this approach indicate that higher DOP and CR and lower R_a, TCR, and TKW were achieved with combinations of the AWJ cutting process parameters, such as water jet pressure of 300 MPa, traverse rate of 120 mm/min, abrasive flow rate of 360 g/min, and standoff distance of 1 mm. The experimental results indicate that the multiresponse characteristics of the AA5083-H32 unit used during the AWJ cutting process can be enhanced through the TOPSIS method. Analysis of variance was carried out to determine the significant factors for the AWJ cutting process.     

带隔板线型聚能装药侵彻能力的正交优化

为了获得带隔板线型聚能装药最佳的结构参数,采用正交优化设计的方法,研究了药型罩楔形角2α、壁厚δ、装药高度H、隔板宽度a、隔板楔形角2β5个因素对线型聚能射流的影响,选取L25(55)正交优化表,利用LS-DYNA软件进行仿真计算,得到了5个因素对射流最大速度和射流长度影响的主次顺序,描述了各因素对射流两个指标的影响规律,获得了最佳的结构组合a3-2β2-H5-2α4-δ4。实验证明,该装药结构对钢靶的侵彻深度大于1倍药型罩口宽,提高了线型聚能装药的切割能力。     

A New Approach for Selection of Optimal Process Parameters in Abrasive Water Jet Cutting

This paper presents a new approach, based on the principles of fuzzy logic and Genetic Algorithm (GA) for selection of optimal process parameters in Abrasive Water Jet (AWJ) cutting of granite to any predetermined depth, using multi-criteria optimization technique. The proposed approach suggests the best combination of process parameters such as water jet pressure, jet traverse rate and abrasive flow rate for cutting granite material to any predetermined depth. GA, in combination with the model built based on fuzzy approach, generates several sets of process parameters satisfying the objective of achieving the desired depth of cut. These sets of parameters are subjected to multi-criteria optimization procedure which suggests a set of process parameters that can minimize the cost of production by increasing the rate of production and reducing the consumption of abrasives, maintaining the desired depth of cut within the specified limits. The proposed approach is validated with suitable experiments conducted on Paradiso granite.     

Research on the Mechanism of Abrasive Particles Accelerated and a Cutting System of a Premixed Abrasive Jet

Forces acting on abrasive in the process of speeding up have been analyzed. Motion differential equation of abrasive in a pipeline and nozzle has been given,respectively. Mechanisms of abrasive particles accelerated in a premixed abrasive jet has been analyzed. The study shows that driven by high-pressure water,velocity of an abrasive is near to velocity of water in pipeline through the acceleration distance. In the taper section of a nozzle,water and abrasive particles are greatly accelerated at the same time. But velocity of an abrasive always lags behind velocity of water. A premixed abrasive jet cutting system has been introduced. The structure and working principles of the system have been given. The system is an assembly of abrasive screening and filling. By use of the premixed abrasive jet cutting system established,cutting experiments have been made to test the main parameters which influence the cutting performances such as working pressure,standoff and traverse velocity,and the nozzle diameter affecting cutting chink width.     

Investigation of process parameters influence in abrasive water jet cutting of D2 steel

In the present experimental study, abrasive water jet (AWJ) cutting tests were conducted on D2 steel by different jet impingement angles and abrasive mesh sizes. The experimental data was statistically analyzed using the simos–grey relational method and ANOVA test. In addition, the outcome of influencing cutting parameters, namely jet pressure, jet impingement angle, and abrasive mesh size on the different response parameters, namely, the jet penetration, material removal rate, taper ratio, roughness, and topography, were studied. Micro-hardness test and surface morphology analysis were employed to examine the D2 cut surfaces at different AWJ cutting conditions. The chemical element study was performed to determine the abrasive particle contamination in the AWJ kerf wall cut surfaces. The ANOVA test result indicated the jet pressure and jet impingement angle as the influencing process parameters affecting the various performance characteristics of AWJ cutting. The overall AWJ cutting performance of the D2 steel has been improved through proper identification of the optimal process parameter settings, namely jet pressure 225?MPa, abrasive mesh size #100, and jet impingement angle 70° by the simos–grey relational analysis.     

Numerical optimization of hole making in GFRP composite using abrasive water jet machining process

Machining of composite materials for the production of bolt holes is essential in the assembly of the structural frames in many industrial applications of glass fiber-reinforced plastic (GFRP). Abrasive water jet cutting technology has been used in industry for such purposes. This technology has procured many overlapping applications and as the life of the joint in the assembled structure can be critically affected by the quality of the holes, so it is important for the industry to understand the application of the abrasive water jet cutting process on GFRP composite materials. The aim of the present work is to assess the influence of abrasive water jet machining parameters on the hole making process of woven-laminated GFRP material and to find the optimum values of the process parameters. Statistical approach was used to understand the effects of the predicted variables on the response variables. Analysis of variance was performed to isolate the effects of the parameters affecting the hole making in abrasive water jet cutting. The results show that the optimum values of cutting feed, fiber density, water jet pressure, standoff distance, and abrasive flow rate upon the response variables are 0.3 m/min, 0.82 g/cm³, 150 MPa, 2 mm, and 100 g/min, respectively.