超声振动辅助铣磨加工对CFRP切削力和表面质量的影响

为研究超声振动辅助铣磨加工对碳纤维增强树脂基复合材料(CFRP)切削力和表面质量的影响,建立了超声振动辅助铣磨加工的切削力模型,进行了磨粒运动轨迹、刀具锋利化效果及单颗磨粒切厚的理论分析及试验验证。结果表明:超声振动辅助铣磨加工与传统铣磨加工相比切削力更小、加工质量更好。当每齿进给量从4μm/z增加到8μm/z时,超声振动辅助铣磨加工的切削力增加了44.7%,小于传统铣磨加工的84.9%;同样,当切深从200μm增加到400μm时,超声振动辅助铣磨加工的切削力增加了187.8%,小于传统铣磨加工的209%;在相同加工参数下,超声振动辅助铣磨加工的工件表面与传统铣磨加工相比,树脂涂覆、表面凹坑和纤维拔出量明显减少。      

纵-弯复合振动超声挤压加工试验研究

为研究挤压加工时静压力、进给量和挤压速度等工艺参数对试件表面质量的影响,在挤压加工中引入纵-弯复合振动后对Q235钢轴件端面进行处理,并与普通挤压加工进行对比,基于正交试验结果构建了挤压加工后表面粗糙度和表面里氏硬度二次回归预测模型.试验发现:在相同加工工艺参数下,在普通挤压加工中引入纵-弯复合超声振动后获得的表面粗糙度Ra值更小,而表面里氏硬度值显著提高;采用两种挤压加工方法后工件表面粗糙度Ra值均随着静压力和进给量的增加而增大,而挤压速度的影响很小,进给量对表面粗糙度的影响最为显著;工件经超声挤压加工时静压力越大,则获得的表面硬度越大,且表面硬度随进给量的增大先增大后减小,而普通挤压加工后表面硬度随静压力和进给量的增大先增后减,且在两种加工方式下工件表面硬度基本不受挤压速度的影响.纵-弯复合振动超声挤压加工工艺适合Q235钢表面强化处理,构建的表面粗糙度和硬度的预测模型可用于指导Q235钢表面强化处理工艺生产.     

Microstructure and mechanical properties of Cr12MoV by ultrasonic vibration-assisted laser surface melting

The effects of laser surface melting assisted by ultrasonic vibration on the microstructure and mechanical properties of Cr12MoV were investigated. Results indicated that the original coarse columnar dendrite can be converted into a fine dendritic and equiaxed. The average microhardness increase from 389HV_0.2 to 427HV_0.2 resulted from the effect of grain refinement. The friction coefficient was lower than the melted layer without ultrasonic vibration and substrate. Under the same experimental conditions, the width and depth of wear scar were decreased by 19% and 25% than that of without ultrasonic vibration, respectively. The wear mechanism from severe adhesive wear into slight abrasive wear under the action of ultrasonic vibration. Experimental results revealed that melted layer fabricated by ultrasonic vibration exhibit finer and more uniform microstructure as well as superior tribological properties.     

Study of milling force variation in ultrasonic vibration-assisted end milling

Ultrasonic vibration cutting has been proved to be an effective cutting technology for its excellent cutting performance and has been widely applied in turning and drilling process. However, this kind of technology is rarely tried in milling process. In cutting process, cutting force is an important process parameter, which affects surface finish and tool wear. This paper investigates the milling force variation in ultrasonic vibration-assisted end milling process through a series of slot-milling experiments. The main research contents include two parts, one is the effect of the externally excited vibration on milling force in milling process, and the other is the influence of milling and vibrating parameters matching on milling force value. Experimental results show that ultrasonic vibration can change traditional milling conditions, realize separate-type milling, obtain similar pulse-like profiles of cutting forces, reduce average cutting force value; and the peak value of the feed direction cutting force can also be greatly decreased by adopting reasonable vibration amplitude, an optimal combination of machining parameters is of great benefit to achieving small cutting force. According to the experimental findings, ultrasonic vibration-assisted milling is a prospective technology to achieve precision milling of small part.     

功率超声电信号的实时检测

针对功率超声电信号高频高压且带有波形畸变的特点,本文研制了一种超声频电信号检测系统,可以对超声过程中功率,电压电流有效值,相位差及频率信号进行快速准确的实时检测,而且可以对测量结果进行实时记录,分析处理,这为实现功率超声的过程实时监控奠定了基础。     

Experimental investigations into the ultrasonic assisted jet electrochemical micro-drilling process

The present article deals with fabrication of ultrasonic assisted jet electrochemical micro-drilling process setup, a special nozzle assembly to pass the ultrasonic vibrations in the electrolyte jet and a work-piece fixture. A detailed experimental study of the newly developed process has been carried out. Effects of process parameters like voltage, inter-electrode gap, electrolyte concentration, electrolyte pressure and pulse on time of ultrasonic vibrations have been studied on process responses, namely, MRR and hole taper. From the results obtained after experimentation, it was observed that MRR improved with an rise in pulse on time of ultrasonic vibrations whereas the hole taper decreased with the rise in pulse on time. It was concluded that combining ultrasonic vibrations with the Jet-ECMD resulted in an enhancement of the process capabilities in terms of improvement of MRR and reduction in the hole taper.     

Effect of ultrasonic vibration on the single discharge of electrochemical discharge machining

Electrochemical discharge machining (ECDM) is one of the non-traditional processes which employs physical and chemical phenomena to remove the material from the non-conductive workpiece. Moreover, some technical augmentations have been added to the mentioned process to achieve a more efficient machining method. Typically, ECDM includes numerous electric discharges, but study on a single discharge, with/without application of external augmentation, leads to understanding the complicated nature of the ECDM process and the effect of technical augmentation. In this research, the ECDM process is studied in the mode of single discharge. Also, ultrasonic vibration, as a technical augmentation, is added to the process (UAECDM) and related effects are studied. For this purpose, special configuration and equipment are used to apply ultrasonic vibration and generate only single discharge. Material removal and tool wear are two important characteristics of drilling process which can be considered to determine the machining efficiency. The current signal is used to determine the current variation and discharge(s) condition. Results showed that the application of ultrasonic vibration changed the current signal pattern to increase discharge numbers in constant condition. Also, ultrasonic vibration increased the material removal up to 35%, while tool wear reduced between 3% and 14%.     

Experimental research on microscale grinding temperature under different nanoparticle jet minimum quantity cooling

To solve the limited cooling capacity of drip cooling technique in current clinical grinding orthopedic surgery, this paper carried out a nanoparticle jet minimum quantity cooling grinding experiment by using hydroxyapatite, SiO₂, Fe₂O₃, carbon nanotubes nanofluids. The mass fraction of each nanofluids was 2%, 4%, 6%, 8%, 10%, respectively. Grinding temperature during the grinding process was measured, and results show that the temperature peak of bone micro-grinding isn’t always proportional to the mass fraction of nanofluids. The measured temperature peak shows an inversely proportional relationship with the mass fraction of nanofluids within a certain mass fraction range, but a proportional relationship beyond this mass fraction range. Such a critical mass fraction varies when using different types of nanoparticles. Combined with heat transfer enhancement of nanofluids, the influence law of nanofluids type and concentration on grinding temperature was disclosed from the rheological properties of nanofluids and the micromechanisms of nanoparticles in the grinding zone. The bigger the mass fraction, the more easily it displays rheological properties. As for hydroxyapatite, whose length-diameter ratio is high and for SiO₂ and CNTs, whose hardness values are high, they more easily display shear thinning and shear thickening, and the effect of rheological properties on temperature is obvious.     

Experimental investigation of surface topography in photochemical machining of Inconel 718

Surface topography is one of the important aspects of micro-components manufacturing. Photochemical machining (PCM) is the most commonly used method in the low-cost micro-manufacturing process. The present investigation focused on the study of the effect of process parameters on the surface topography in PCM of Inconel 718 of two different grain sizes using ferric chloride (FeCl₃). For this work, the input parameters considered are concentration, time and temperature of the etchant. The temperature of the etchant was found to be the most dominant parameter in the PCM of Inconel 718. Moreover, in this study, the effect of grain size of samples on surface roughness was considered. The average increase in surface roughness is 1.227 times due to variation in grain size from 59?µm to 42?µm.     

旋转超声磨削钛合金有限元仿真与试验研究

为了研究固结磨粒磨具的磨料粒度对旋转超声磨削钛合金磨削力的影响,采用随机空间平面切割正六面体的方法构建了具有实际磨粒几何特征的不规则多面体磨粒,并基于虚拟格子法建立了磨粒在磨具端面随机分布的多颗磨粒磨具模型。使用Deform-3D软件构建了三维旋转超声磨削钛合金有限元模型,采用拉格朗日增量算法获得了多颗磨粒磨具旋转超声磨削钛合金Ti6Al4V的磨削力仿真值,得到了磨料粒度对磨削力的影响规律,并通过试验进行了验证。结果表明,旋转超声磨削钛合金磨削力随着磨料粒度的增大而减小,且试验结果和仿真结果具有一致性,说明了多颗磨粒磨具模型、旋转超声磨削有限元模型具有一定的准确性,为多颗磨粒磨具旋转超声磨削的相关研究提供了新的方法。     

旋转超声内圆磨削砂轮变幅器的设计与试验研究

砂轮变幅器是旋转超声内圆磨削谐振系统的关键部件,其设计质量直接影响超声磨削的工艺效果。但目前内圆磨削砂轮变幅器缺乏较为完善的理论分析模型。为提高砂轮变幅器理论分析模型的通用性,基于非谐振设计理论建立了纵向谐振砂轮变幅器的理论分析模型,并利用砂轮变幅器各振动单元间的力、位移连续条件与边界条件推导了其频率方程。然后,针对频率方程进行编程求解,并通过ANSYS有限元仿真分析进行验证。最后,加工制作了纵向谐振砂轮变幅器,并开展阻抗特性分析试验、超声谐振试验和振动位移测量试验,分析了其谐振特性。试验结果表明,所研制的砂轮变幅器的谐振试验频率与理论设计频率一致,其输出端振动位移的试验值与仿真值的相对误差为7.83%,符合旋转超声内圆磨削的要求,验证了理论分析模型求解的正确性。研究结果为旋转超声内圆磨削砂轮变幅器的设计提供了便捷且有效的方法。     

A comprehensive study on surface integrity of nickel-based superalloy Inconel 718 under robotic belt grinding

Surface integrity of materials should be considered under robotic belt grinding in order to achieve desired finishing quality. In this work, the surface integrity of nickel-based superalloy Inconel 718, involving morphological structure, surface roughness, residual stress and structural domain size, was characterized systematically. A novel predicted model of grinding parameters optimization was proposed based on linear weighting function. The result shows that considerable compressive stress (about?355 MPa) and minimum roughness on material surface are achieved simultaneously at the grinding force of 178 kPa and belt speed of 31 m/s. The morphological structures and microhardness for the specimen under the optimized condition were further analyzed and discussed. Surface hardness is increased by 15%. Grain refinement and a large number of dislocations occur in the subsurface, which are attributed to continuous partial dynamic recrystallization associated with combined effects of plastic deformation and thermal treatment, which results from grinding force and belt speed. The new findings are of significance for ensuring surface integrity with optimal process parameters.     

PBX代用粉体超声加载成型的实验研究

设计了PBX代用粉体超声成型装置。研究了超声波加载对含能有机复合粉末成型效果的作用,对于直径为200mm、高为60~65 mm的压坯,与相同条件下无超声压制相对比,压坯密度提高了1.79%;声速测试表明,压坯强度有一定增强;CT成像表明压坯均匀性有一定提高;压坯表面温度分布均匀,未出现局部过热现象。研究表明超声波加载技术在较大尺寸含能材料成型过程中对提高成品品质具有促进作用。     

先进陶瓷材料超声振动铣磨加工表面粗糙度仿真及实验(英文)

为了对超声振动铣磨加工先进陶瓷的表面粗糙度进行预测,建立了加工表面形貌的仿真模型.通过实验测得砂轮表面形貌和磨粒突出高度信息,并对这些信息进行Kolmogorov-Smirnov正态验证,发现砂轮表面形貌不服从高斯分布.对非高斯分布的数据进行Johnson变换,建立砂轮形貌的数值模型.结合砂轮表面形貌和磨粒与工件的相对运动分析,提出了一种表面轮廓搜索方法,进而生成了加工表面的三维形貌.最后,在DMG ULTRASONIC 70-5 linear机床上进行切削实验,对仿真结果进行了验证,结果表明仿真与实验结果具有较好的一致性,并对仿真误差产生的原因进行了分析.     

Experimental investigations into sintering of magnetic abrasive powder for ultrasonic assisted magnetic abrasive finishing process

The importance of magnetic abrasive powder (MAP) in finishing the surface of work materials as a flexible cutting tool in the presence of a magnetic field during the ultrasonic assisted magnetic abrasive finishing (UAMAF) process is quite evident. A sufficiently intense magnetic field provides the desired magnetic force to the iron particles. This holds nonmagnetic abrasive particles firmly and thus makes flexible chains. However, at higher rotational speeds of the magnet due to the requirement of high centripetal force, the chains start flying away from the finishing zone. In the present work, to overcome this deficiency, bonded MAPs were developed using the sintering technique. The effect of various process parameters on the magnetic property (magnetization) of sintered MAPs was investigated. Design of experiments (DoE) was planned as per the L₈ orthogonal array of the Taguchi method, and magnetizations along with M-H curves for all eight different MAPs were measured. Subsequently, analysis of experimental data was carried out using various techniques to optimize the process parameters. It was observed that sintering temperature affects magnetization the most. Scanned microscopy (SEM) and X-ray diffraction (XRD) analysis were also carried out to investigate bonding strength in sintered MAP.     

旋转超声磨削Si3 N4陶瓷用金刚石磨具磨损行为研究

热压烧结Si₃N₄陶瓷材料常应用于航天飞行器中关键耐高温零部件,但由于高硬度和低断裂韧性,其加工效率和加工表面质量难以满足制造需求。为了提高热压烧结Si₃N₄陶瓷旋转超声磨削加工质量,减小由于金刚石磨具磨损带来的加工误差,开展了磨具磨损行为研究。基于热压烧结Si₃N₄陶瓷旋转超声磨削加工实验,分析了金刚石磨具磨损形式;基于回归分析建立了金刚石磨具磨损量数学模型,揭示了加工参数及磨具参数与金刚石磨具磨损量间映射关系;并研究了磨损形式与磨具磨损量及加工表面粗糙度影响规律。结果表明：磨粒磨耗是旋转超声磨削Si₃N₄陶瓷用金刚石磨具最主要磨损形式,比例超过50%;主轴转速和磨粒粒度对磨具磨损量影响最为显著;且磨损量较小时,加工表面粗糙度值反而增加。以上研究可为提高旋转超声磨削Si₃N₄陶瓷加工精度和加工质量提供指导。     

不同振动方式下的钛合金超声振动铣削表面完整性研究

钛合金在机械工程领域应用广泛,其加工表面完整性对钛合金工件的耐磨性、疲劳强度、使用寿命有着非常重要的影响.通过对工件施加不同振动方向的超声振动,开展了不同振动方向下的TC4钛合金超声振动侧铣平面试验,分析了不同振动方式的运动学轨迹特征,研究了振动方式、切削参数对钛合金加工表面完整性的影响规律.结果表明:法向振动铣削后的...     

钛合金超声椭圆振动辅助车削实验研究

设计钛合金超声椭圆振动辅助车削实验,获得不同超声波电源电压下刀具近似椭圆运动轨迹。分析超声椭圆振动辅助车削切削力变化规律,与普通车削相比超声椭圆振动辅助车削能在较大程度上降低切削力。研究超声椭圆振动辅助车削工件表面粗糙度变化规律,与普通车削相比超声椭圆振动辅助车削工件表面粗度Ra值略增大,Rz值明显降低。分析进给速度对切削力的影响规律,随进给速度增大,普通车削及超声椭圆振动辅助车削切削力均升高。对同一进给速度,与普通车削相比超声椭圆振动辅助车削切削力均降低,且随进给速度增加其降低幅度减小。对比超声椭圆振动辅助车削与普通车削工件表面形貌发现,施加超声椭圆振动后工件表面沿切削速度方向形成有规律振纹。     

Feasibility study of a flexible grinding method for precision machining of the TiAl-based alloy

This study presents detailed experimental investigations on precision machining of the TiAl-based alloy with an abrasive belt flexible grinding method. Subsequently, the feasibility of this precision machining method is evaluated with respect to the material removal rate, abrasive wear, machined surface roughness, and residual stress. The material removal rate and surface roughness were determined as experimental indicators and were measured via a three-coordinate measuring instrument and surface profiler, respectively. Micro-morphologies of the machined surface and worn abrasive belt were investigated via a scanning electron microscope. The residual stress distributions in the machined surface layer were detected by using an X-ray diffractometer. The experimental results revealed that the aforementioned evaluation indicators satisfied the desired requirements, thereby indicating that the abrasive belt flexible grinding technique was suitable for precision machining of the TiAl-based alloy. Additionally, the optimal combinations of grinding parameters were determined to obtain desirable material removal rate and machined surface roughness. The basic wear processes and characteristics of the abrasive belt were thoroughly examined. The formation of desirable residual compressive stresses in the machined surface layer was mainly attributed to low frequency and small amplitude vibration knocking at the grinding interface.