Influence of materials and machining parameters on WEDM of Al/AlCoCrFeNiMo0.5 MMC

The current study intends to optimize the wire electric discharge machining (WEDM) parameters while machining the newer AlCoCrFeNiMo_0.5 high entropy alloy (HEA) particles-reinforced aluminum composites. AlCoCrFeNiMo_0.5 HEA particles produced through arc melting technique are reinforced here for different weight % (0%, 3%, 6%, 9%, 12%, and 15%) along with pure aluminum by the way of powder metallurgy. WEDM studies were conducted by varying the appropriate parameters, namely, pulse ON time, pulse OFF time, and wire feed. Based on the selected parameters, through Taguchi method L18 orthogonal array is designed; the optimal parameter combination for better surface finish, material removal rate (MRR), and reduced kerf width (KW) is identified. For better understanding, through ANOVA, also the effect of each input variables over these adopted response variables was analyzed. The yielded results reveal that addition of AlCoCrFeNiMo_0.5 HEA as reinforcement has considerable effect over the response variablessuch that MRR and KW reduces; surface roughness increases with increase in HEA %. ANOVA results confirm that pulse ON time has higher effect over the response variables than any other parameters involved for the study. Multi-objective optimization done through Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) methodology answers that MRR and surface finish have improved, whereas KW gets reduced noticeably.     

WEDM of Mg/CRT/BN composites: Effect of materials and machining parameters

The current work presents a detailed exploration on real-time wire electric discharge machining (WEDM) experiments and grey relational analysis (GRA)–based multi-criteria optimization of material and machining characteristics for lowered surface roughness (R_a) and improvised material removal rate (MRR) of the newly developed magnesium/boron nitride/cathode ray tube (Mg/BN/CRT) hybrid metal matrix composites (MMCs). The composites were fabricated through powder metallurgy (PM) route by reinforcing silica-rich E-waste CRT panel glass powder crushed for different particle sizes (10, 30, and 50?µm) at various weight percentages (5%, 10%, and 15%) and with 2% boron nitride (BN). Taguchi-based orthogonal array procedure was utilized to formulate the experimental plan for WEDM considering reinforcement level and size, pulse on time (P_on), pulse off time (P_off), and wire feed (W_f) as the input process parameters. ANOVA results reveal that P_on and wt% of reinforcement has more effect on R_a and MRR than any other considered parameters. The developed mathematical model for R_a and MRR predicted values similar to that of experimental results. Multi-criteria optimization was done through GRA technique and the so recommended optimum parameter set furnishes higher MRR (22.34?mm³/min) and reduced R_a (2.87?µm).     

Modeling and Optimization of Machining Nimonic C-263 Superalloy using Multicut Strategy in WEDM

In recent years, wire-electrical discharge machining (WEDM) has gained popularity in the industry due to its capability to generate complicated shapes in exotic materials, irrespective of their hardness. Conventional machining of Nimonic C-263 superalloy is an extremely difficult and costly process due to its high hardness and tool wear rate. The present research work investigates the influence of the WEDM process parameters on different performance measures during machining of Nimonic C-263 superalloy. A mathematical model for all four important performance measures, namely, cutting rate, surface roughness, spark gap, and wire wear ratio, was developed and the responses were used for studying the interrelationship between performance measures and process parameters. The optimal settings of operating conditions were predicted using desirability function. The effectiveness of multicut strategy was also investigated in the article.     

Surface modification of WC-Co alloy using Al and Si powder through WEDM: A thermal erosion process

This paper presents the surface modification of WC-Co alloy with the use of aluminum and silicon powder in wire electric discharge machining (WEDM) process. A separate attachment with the stirrer is used to mix the metal powder in the dielectric, which is further supplied by a pump at the workplace continuously. The effects of different process parameters like peak current, pulse on-time, pulse off-time and servo-voltage are investigated on the material transfer, crack formation and white-layer formation with the help of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis. It was observed that silicon powder enhances the surface quality (4?µm white layer) compared with aluminum (6?µm white layer) powder. The white-layer thickness without the use of metal powder was around 14?µm. The cracks density after the addition powders reduces significantly.     

Abrasive waterjet cutting of cladded material: kerf taper and MRR analysis

Gas/plasma cutting of cladded materials provides inferior cut quality that demands subsequent finishing processes. Abrasive waterjet cutting could be a proficient alternate in terms of cut quality. However, the inherent problem of kerf taper and low material removal rate in comparison to the said thermal cutting processes limit its application. Therefore, potential of aforesaid machining process for cutting of stainless-clad steel is investigated with a prior focus on maximizing the material removal rate with minimum kerf taper. Abrasive mass flow, traverse speed, water pressure, and stand-off distance have been selected as input parameters. ANOVA analysis revealed that traverse rate as well as abrasive mass flow are the major contributing factors for both the responses. Optimal settings of parameters developed by S/N ratio analysis results in an improvement of 18.6% in material removal rate and 39% in the kerf taper. Moreover, regression models are developed and validated through various statistical tests.     

Modeling and Analysis of Machinability Evaluation in the Wire Electrical Discharge Machining (WEDM) Process of Aluminum Oxide-Based Ceramic

The wire electrical discharge machining (WEDM) allowed success in the manufacture of the hard, fragile, and materials difficult to cut, especially for electroconductive ceramic materials. In this study, the mathematical models of material removal rate (MRR) and surface roughness (SR) used for the machinability evaluation in the WEDM process of aluminum oxide-based ceramic material (Al₂O₃ + TiC) have been carried out. The experimental plan adopts the face centered central composite design (CCD). The mathematical models using the response surface methodology (RSM) are developed so as to investigate the influences of four machining parameters, including the peak current, pulse on time, duty factor, and wire speed, on the performance characteristics of MRR and SR. It has been proved that the proposed mathematical models in this study would fit and predict values of the performance characteristics, which would be close to the readings recorded in experiment with a 95% confidence level. The significant parameters that critically affect the performance characteristics are examined.     

4045/3004/4045层状铝合金复合材料连铸制备方法

本文旨在开发出制备复合锭坯的新技术,在新型热顶石墨环结晶器中安装冷却板,采用直接水冷半连续铸造法实现了4045/3004/4045铝合金三层复合锭的实验室制备,研究了复合锭坯的宏观形貌、微观组织,并考察了界面两侧元素分布以及铸造过程中界面附近3004合金熔体的温度分布.结果表明:在冷却板的作用下界面附近形成了一层温度分布较为均匀的固态支撑层,从而保证复合铸造过程的顺利实现,复合界面结合较好,且为一种冶金结合;由界面抗拉强度测试结果可知界面的结合强度均高于96 MPa,进一步证明了两种合金的结合是一种冶金结合.     

基于宏观各向异性碳纤维增强树脂基复合材料的切削仿真

为了对碳纤维增强树脂基复合材料切削加工过程中的基体破坏及亚表层损伤机制进行研究,借助数值仿真方法建立了基于宏观各向异性的复合材料正交切削有限元模型。采用Hashin-Damage失效准则,通过定义纤维拉伸断裂、压缩屈曲极限应力及基体横向拉伸断裂、剪切断裂极限应力等数值,建立了复合材料切削加工动态物理仿真模型。通过切削力仿真值与实验值的比较,验证了仿真模型的有效性。通过对0°和90°纤维方向复合材料基体开裂和压溃的分析发现,当进入稳定切削后,基体开裂方向与纤维方向平行,而基体的压溃主要发生在刀尖周围。分析了纤维方向对复合材料亚表面损伤深度的影响,随着纤维方向角度的增加,工件亚表面裂纹损伤深度呈增长趋势。     

复合半导体纳米材料的研究与制备

综述了纳米半导体的特性及应用,以及复合半导体纳米微粒的类型及其制备等方面的进展。     

陶瓷-金属双连续相复合材料的发展现状与未来

陶瓷-金属双连续相复合材料作为一种采用空间连续网络构型设计的复合材料,具有耐摩擦磨损、抗热震性高、热膨胀系数低等特点,具有广阔的应用前景.其中,多孔陶瓷预制体作为双连续相复合材料中的结构增强相,其本征特性对复合材料的整体性能有重要影响.本文系统分析了现阶段在多孔陶瓷的制备方法与表面改性两个领域内的主要进展,并对陶瓷-金...     

纳米镍/炭复合材料的制备与磁性表征

以废弱酸型聚丙烯酸系阳离子交换树脂为炭前驱体,经过与镍离子交换后,再经热解制备纳米镍粒子均匀分散于炭基体的纳米镍/炭(Ni/C)复合材料.以XRD、TEM为主要分析手段研究了热解条件对纳米镍粒子在Ni/C复合材料中的形貌、大小的影响.结果表明:通过热解条件可以控制Ni/C复合材料中纳米镍粒子的平均粒径;热解温度的升高和热解保温时间的增加都可使Ni/C中纳米镍粒径增大.磁性能测试结果表明: Ni/C-500表现为超顺磁特性,而Ni/C-600、Ni/C-700为铁磁性;Ni/C-600、Ni/C-700的比剩磁化强度、矫顽力都要大于微米镍粉与块体镍,但其比饱和磁化强度要小于微米镍粉和块体镍.     

Non-linear stress analysis of composite layered plates and shells using a mesh reduction method

This paper represents an attempt for reducing the dimensionality of the finite element method, based on applying a new concept to the finite strip method. Mindlin's plate-bending theory has been employed for the derivation of an efficient element for buckling and stress analysis of folded and stiffened plates made of composite layered materials. The plate midplane is to be discretized in one direction in terms of this new element, leading to a simple mesh reduced by one dimension as compared with standard finite element meshes. The interpolation in the other direction is achieved by employing independently a smooth polynomial over the plate width. An efficient modular programming package based on the new element has been designed, and a number of case studies have been employed for its validation. The package has proved to be an efficient tool for numerical modelling of trapezoidal and stiffened plates, and cylindrical shells, made of isotropic or composite layered materials.     

Experimental and numerical analysis of a bus component in composite material

The aim of this work is the fatigue design of a structural component manufactured in composite materials. The use of composite materials in structural applications implies that the reliability and safety requirements are met, in particular from a point of view of the fatigue life. A bus component is considered: the composite material is obtained by means of the pultrusion technique: the longitudinal reinforcement is glass fibre, while the matrix is polyester resin. At first, a static and fatigue characterization of the pultruded composite is performed to identify the mechanical behaviour along the fibres and in the normal direction, following an extensive testing programme on specimens. During the fatigue tests, the variation of the elastic modulus and the residual strength are monitored to characterize the damage; further experimental tests are performed to fit parameters required for models of fatigue life prevision. Fatigue bending tests are performed on the component, showing crack propagation through the section: a check at the SEM is performed to identify the main internal type of damage. A final comparison with a numerical simulation is proposed: this numerical model will be useful for the optimal fatigue design of the section.     

Synthesis and application of Poly(acrylamide-itaconic Acid)/Zirconium tungstate composite material for cesium removal from different solutions

This study is conducted to find the conditions required to synthesize composite material for cesium (¹³⁴Cs⁺) removal from the generated liquid waste associated with nuclear, medical, industrial, and/or research activities. The study shows that the optimum conditions required for synthesizing “Poly [acrylamide (AM)-itaconic acid (IA)]/N,N′-methylenediacrylamide (DAM)/Zirconium tungstate (ZrW)” or “Poly(AM-IA)/DAM/ZrW” are 0.01 g DAM dose as a cross-linker, a co-monomer concentration of 20%, a co-monomer composition (AM-IA) (12:88), and 0.03 g (melted at 450 °C–500 °C) ZrW with gamma irradiation dose of 30 kGy. The composite material was characterized by Fourier infrared (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscope (SEM), and Brunauer-Emmett-Teller (BET) surface area measurements. The adsorption performance of the composite was investigated. The maximum removal efficiency of ¹³⁴Cs⁺ ions was found to be 93% in moderate alkaline solutions at pH 8 ± 0.2 after 90 min. Kinetic studies indicated that the adsorption process is controlled by the pseudo-second-order kinetic model as a chemisorption process. Fitting of the adsorption data has pointed out that the adsorption process follows the Freundlich isotherm model as heterogeneous process. The maximum adsorption capacity (q_max) is 5.298 mmol Cs⁺ g^?1 adsorbent. Applicability of the synthesized composite material was also examined to remove ¹³⁴Cs⁺ ions in different aqueous solutions.     

银掺杂三氧化钨复合上转换材料的制备与表征

WO₃本身在紫外光下具有很强的光催化性能,在可见光下能力较弱。为了改善其光催化性能,通过热解法和水热法分别制备出WO₃颗粒和WO₃纳米管基体,采用水热还原法制备出不同质量比的WO₃与Ag复合的光催化剂。以罗丹明B为目标降解物,对其光催化性能进行了测试。结果表明:热解法制备的WO₃与Ag的复合并未改善其光催化性能,水热法制备的WO₃纳米管在与银复合后一定程度上提高了WO₃的光催化效果。为了进一步提高其催化效率,把Ag/WO₃与上转换材料NaYF₄∶Yb,Er进行了复合,并对其进行了光催化实验。实验证明Ag/WO₃与上转换材料NaYF₄∶Yb,Er质量比为0.25时,在暗反应过程中罗丹明B浓度有明显的下降。通过实验表明与上转换材料NaYF₄∶Yb,Er的复合使其具有了良好的吸附性能,在对处理环境污染起到了一定作用。     

Catalytic activity of a soft composite material: Nanoparticle location–activity relationship

A nanostructure, fiber-shaped morphology of a conjugated polymer (poly-5 amono-ortho-cresol, PAOC) has been synthesized using palladium acetate as the oxidizing agent. A one pot, in situ chemical synthesis approach has been utilized in which palladium acetate was reduced during the polymerization process of 5-amono-o-cresol (AOC) and formed well dispersed palladium nanoparticles in the polymer fibers. The resultant composite material was characterized by means of optical, thermo and micro-analytical techniques. The elemental identity of the nanoparticles was determined by means of electron energy loss spectroscopy (EELS) mapping using analytical transmission electron microscopy (TEM). Subsequently, the sample was used as a catalyst for a model gas-phase hydrogenation reaction. The activation and deactivation behaviour of the catalyst as a function of temperature is discussed in the light of different phase transition points of the polymer as well as the orientation of the palladium nanoparticles. The fact that palladium nanoparticles (2 nm) were uniformly distributed throughout the polymer matrix makes the composite material an excellent hybrid structure.     

Effects of material properties and crush conditions on the crush energy absorption of fiber composite rods

Crushing along the fiber axis of undirectional E-glass fiber composites rods was examined to determine the effects of fiber volume fraction, fiber diameter, matrix compressive yield strength, crush rate, fiber surface treatment, and crush plate geometry. The volume specific energy absorption was found to increase with fiber content, fiber diameter, matrix yield strength, and crush rate. The crush load stability was found to be independent of fiber content and fiber diameter but not of matrix yield strengt. The crush load became less stable as the yield strength increased. The crush behavior of specimens containing clean fibers was about the same as with sized fibers, but specimens with a release agent on the fiber surface crushed with less energy absorption that decreased even as the fiber content increased, but the crush load was more stable than with sized or clean fibers. The volume specific energy absorption was greater when the rod specimens were crushed against concave surfaces than against a flat plate. A relatively simple model was able to account for the dependence of the energy absorption on fiber volume fraction and matrix yield strength.     

壳聚糖/磷灰石-硅灰石复合多孔支架材料的制备与性能

以磷灰石-硅灰石(AW)生物活性多孔玻璃陶瓷支架材料为基体,采用物理包被法制备了壳聚糖(CS)/AW复合多孔支架材料,通过红外图谱分析、扫描电镜、光学显微镜、强度检测等分析测试方法,研究了复合材料的组成、微观结构、力学和矿化性能。结果发现：复合材料与AW多孔支架材料基体相比,仍具有三维贯通且分布均匀的孔隙结构,孔径尺寸约 100～500μm,孔隙率为80%左右,且力学性能明显增强,平均抗压强度可达3.11 MPa,比多孔AW支架材料基体的平均抗压强度提高了8.3倍。体外模拟体液浸泡实验表明,复合材料具有较高的矿化功能,预示材料具有较好的生物活性。这种复合材料可望作为人体非承重部位的植入骨修复体和组织工程支架使用。     

湿法纺丝Amid-CNT/PAN复合纤维的结构与性能

通过溶液聚合得到胺化碳纳米管（Ami-CNT）/聚丙烯腈（PAN）复合溶液, 采用湿法纺丝技术制备了Amid-CNT/PAN复合纤维。利用红外光谱、 拉曼光谱、 差示扫描量热仪、 热失重仪和扫描电镜等方法分析Amid-CNT对PAN纤维结构的影响。结果表明: Amid-CNT与PAN大分子之间有很强的化学作用力; Amid-CNT在复合纤维中具有很高程度的取向, 使PAN纤维中氰基的取向从1.61提高到了2.30; 复合纤维在空气中的起始放热温度相对PAN纤维从212.30℃提前到206.01℃, 反应放热量从3054J/g降低到2346J/g; 复合纤维比PAN纤维的起始失重温度提前了3.7℃, 在700℃时的剩余质量提高了13.5%; 复合纤维的断面比PAN纤维具有更多的絮状结构。      

Preparation and thermal properties of layered porous carbon nanotube/epoxy resin composite films

A floating-catalyst spray pyrolysis method was used to synthesize carbon nanotube (CNT) thin films. With the use of ammonium chloride as a pore-former and epoxy resin (EP) as an adhesive, CNT/EP composite films with a porous structure were prepared through the post-heat treatment. These films have excellent thermal insulation (0.029--0.048 W·m⁻¹·K⁻¹) at the thickness direction as well as a good thermal conductivity (40--60 W·m⁻¹·K⁻¹) in the film plane. This study provides a new film material for thermal control systems that demand a good thermal conductivity in the plane but outstanding thermal insulation at the thickness direction.