Precision finishing of the inner surface of SUS 304 pipes is of great practical value in aerospace and other high-end manufacturing fields. Accurate analysis and prediction of material removal depth (MRD) form the core technical support for optimizing process parameters and ensuring machining precision. In this study, a predictive model for MRD during magnetic abrasive finishing (MAF) of the inner surface of SUS 304 pipes is developed. First, the cross-sectional profile data of the material removal area are obtained through magnetic abrasive finishing experiments on SUS304 planar workpieces, and the material removal volume is further calculated accordingly. According to the Preston equation, the material removal coefficient is finally determined. Through coupled simulations of the Maxwell finite element method (FEM) and EDEM discrete element method (DEM), the energy accumulation and distribution characteristics on the inner surface of SUS 304 pipes were obtained, and the finishing pressure was further derived. By integrating the material removal coefficient, finishing pressure and motion velocity of magnetic abrasive particles, the material removal depth within a given machining time was ultimately calculated. A series of experiments were conducted, and the results indicate that under different experimental conditions, the minimum relative error of the model predictions is 8.14%, the maximum is 18.83%. This study provides a reliable theoretical basis for the engineering application of MAF precision finishing for the inner surfaces of SUS 304 pipes.

ObjectivesPrecision micro through-hole parts are widely used. However, due to the limitations of manufacturing technology, precision parts with complex shapes, such as cross micro-holes, may have defects such as burrs, scratches, and nodules during the manufacturing process. In view of the problems of conventional finishing processing of cross deep micro-holes being limited by size, uneven processing, and poor quality, and combined with the characteristics of a stable removal function and strong adaptability of the abrasive jet, the magnetic micro-abrasive jet technology finishing processing method is proposed to improve the quality of the inner wall of cross deep micro-holes.MethodsAn independent magnetic abrasive jet device was used to carry out finishing tests on the cross deep micro-holes, and an electromagnetic device was used to generate a focusing magnetic force near the nozzle outlet. The magnetic abrasive was concentrated towards the center during the internal movement of the nozzle, alleviating the problem of rapid divergence of the magnetic abrasives with the jet after spraying and further improving the efficiency of finishing processing. A simulation mathematical model was established to explore the influence of different process parameters on the finishing effect. The finite element method and the discrete element method were coupled to simulate the polishing process of the inner wall of deep micro-holes by the magnetic micro-abrasive jet under different process parameters. The flow field distribution, the erosion rate, and the action law of wall shear force under different parameters were analyzed, and the key factors were identified. Finally, the response surface method was used to optimize the three factors of jet target distance, jet pressure, and nozzle diameter. The response surface equation was established and solved by taking the comprehensive influences of wall shear force and erosion rate on the orifice, the inner wall of the hole, and the cross part of the hole as the response value, and the optimal combination of process parameters was obtained and verified by the test.ResultsAdding a focusing magnetic field near the nozzle can effectively reduce the divergence of the abrasive after jet ejection, and further improve the efficiency and quality of magnetic abrasive ejection polishing of cross deep micro-holes. The simulation results show that the main parameters affecting micro-hole finishing are jet target distance, jet pressure, and nozzle diameter. By using the response surface method combined with experiments for parameter optimization, the optimal process parameter combination for magnetic micro-abrasive jet finishing of cross deep micro-hole inner walls is obtained, which includes a jet target distance of 7 mm, a jet pressure of 1.0 MPa, and a nozzle diameter of 1.4 mm. Under the optimal combination of process parameters, the inner wall quality of the cross deep micro-holes is significantly improved, the burrs at the cross-holes are completely removed, the wall roughness Ra is reduced from 0.49 μm to 0.13 μm, and the orifice has a good rounding effect.ConclusionsBy combining magnetic fields and abrasive jets, the magnetic micro-abrasive jet technology provides a new method for the finishing of cross deep micro-holes. Due to the ability of the magnetic abrasive micro-jet to achieve focused fixed-point machining, it has significant processing advantages in cross deep micro-hole finishing and deburring. By constructing a physical model of the machining process and using the simulation form of coupling the finite element method and the discrete element method, it is possible to more clearly simulate the motion of the abrasive and flow field in the abrasive water jet during the machining process, as well as the force situation of the workpiece being machined. In the finishing process of cross-hole parts, the nozzle diameter, pressure, and target distance have a direct impact on the finishing effect. However, parameter adjustment is required for finishing workpieces of different sizes and shapes. Finding suitable processing parameters will further improve the quality and efficiency of workpiece processing.

ObjectivesMagnetic particle grinding finishing technology as an advanced processing technology can achieve high precision surface treatment. In order to simplify the test device, reduce the test cost and improve the processing effect, the single particle size abrasive is changed to mixed particle size abrasive without changing the test device, so as to improve the grinding effect of magnetic particles.MethodsFinite element analysis software is used to simulate the magnetic field in the machining area, and the magnetic field data is imported into the discrete element simulation software through an API interface to obtain the magnetic field during the simulation process, in order to simulate the force situation of mixed particle size abrasive and single particle size abrasive during machining. Taking the spindle speed of the machine tool (A), the abrasive mass ratio (B) and the abrasive particle size ratio (C) as the research objects, the experimental parameters are analyzed and optimized using response surface methodology. To prevent abrasive splashing and reduce the grinding effect, the selected experimental parameters ranges are 400 to 600 r/min for A, 0.50 to 2.00 for B, and 1.5 to 2.5 for C. Using the surface roughness Ra of the workpiece as the response value, the Box Behnken method is used for response surface test design.ResultsThe P-value of the variance analysis of the model experiment results is less than 0.000 1, indicating that the experimental model is highly significant. The mismatch term refers to the unexplained error in the model, with a P-value of 0.458 1, much greater than 0.050 0, indicating that the mismatch term is not significant and the regression equation fitted by the software is valid. At the same time, the multiple correlation coefficient R2 is 0.996 2, and R2Adj is 0.989 4 after verification, which is very close to 1.000 0, indicating a good fit of the model. Moreover, the surface roughness is affected by the spindle speed, abrasive mass ratio and abrasive particle size ratio to 98.94%. The results of the single factor experiment indicate that the order of influence on surface roughness Ra is the spindle speed, followed by the abrasive mass ratio and the abrasive particle size ratio. When the spindle speed is 500 r/min and the abrasive mass ratio is 1.25, the workpiece surface roughness Ra reaches the minimum value. In the case of a certain abrasive mass ratio, when the abrasive particle size ratio is 2.0 and the spindle speed is 500 r/min, the workpiece surface roughness Ra reaches its minimum value. Under the condition of constant spindle speed, when the abrasive mass ratio is 0.50 and the abrasive particle size ratio is 2.5, the workpiece surface roughness Ra reaches the maximum. However, when the abrasive particle size ratio is 2.0 and the appropriate mass ratio is 1.25, the surface roughness Ra of the workpiece can reach the minimum value. Aiming at the minimum surface roughness Ra of the workpiece, the response surface software is used to optimize the data, and the optimal process parameter combination for workpiece processing is obtained, that is, the spindle speed is 511 r/min, the abrasive mass ratio is 1.67, the abrasive particle size ratio is 1.9, and the predicted surface roughness Ra value after processing is 0.038 µm. When the workpiece is machined under the optimal process parameters, the surface roughness Ra of the workpiece decreases from the original value of 0.244 μm to the test value of 0.036 μm, and the absolute value of relative error between the two is 5.26%.ConclusionsThe experimental results show that the established model is effective, and the process parameters that affect the surface roughness Ra of the workpiece are in the order of spindle speed, followed by abrasive mass ratio and abrasive particle size ratio. Compared to single-abrasive magnetic particle grinding, the use of mixed abrasives can further reduce the surface roughness of the workpiece and improve its machining effect.

As an advanced precision machining process, magnetic abrasive finishing (MAF) technology can be applied to grind complex workpieces. However, it is not conducive to formulate an appropriate processing that MAF processing on tubular workpiece has a severe lack of a well-defined material removal rate model. In order to solve this problem, the contact form between the magnetic abrasive and the workpiece surface was simplified, and the force analysis of the magnetic abrasive in the magnetic field was performed. Furthermore, an ideal predictive model on material removal rate was proposed, which was based on both the quantity of active abrasives in the processing area and the depth at which magnetic abrasive was pressed into the workpiece. The correction factor 'k' was determined based on the comparison and analysis of experimental results and theoretical predictions. What is more, the accuracy of the revised model on material removal rate was confirmed. The surface roughness of the workpiece was reduced from 0.213 to 0.058 μm after undergoing 19 cycles of processing under the conditions of spindle speed of 104.7 rad/s, abrasive mass of 3.5 g, processing distance of 2 mm, and a feed rate of 3 mm/s. The material removal rate was 0.140 μm/min, which exhibits an absolute error of 7.675

In order to explore the influence of various process parameters in the pressing stage of magnetic abrasive grain bodies on their forming quality, optimize the sintering preparation parameters of magnetic abrasive grains, and prepare high-quality magnetic abrasive grains, the dispersion element model of dry pressing forming of magnetic abrasive grains was established with iron-based alumina magnetic abrasive grains as the research object. By changing the pressing force, pressing mode, friction coefficient, die height-diameter ratio and other process parameters, the influence of each process parameter on the forming quality of the magnetic abrasive grain bodies was explored, and the optimization of process parameters in the pressing process was realized. The results show that the larger the pressing force, the smaller the porosity of the green body. However, if the pressing force is too large, cracks will appear on the outer surface of the green body, affecting the integrity of the surface morphology of the green body. Therefore, a pressing force of 75 to 125 MPa should be selected. The density of the green body obtained by two-way pressing is more uniform, and the mechanical properties are better. The higher the height-diameter ratio of the mold, the higher the porosity of the green body, and the smaller the axial stress of the green body. The smaller the friction coefficient between particles and between the side wall and particles, the smaller the porosity, the better the density and the better the homogeneity of the green body. When adding an appropriate amount of lubricant in the mixing stage of the magnetic abrasive particles, the friction coefficient between the magnetic abrasive particles and between the particles and the side wall of the mold can be appropriately reduced, thereby improving the quality of the abrasive body.

Magnetic needle grinding processing technology is one of the magnetic grinding processing techniques. It possesses the characteristics of micro-cutting removal, small increase in processing temperature, flexible processing, high-quality, and high-precision processing. It is mainly utilized to remove burrs at the edge of the workpiece and the edge of the hole, as well as to finish the surface of the workpiece. It is frequently employed in civil, aerospace, navigation, and other fields. Due to the randomness and complexity of magnetic needle movement in magnetic abrasive finishing, it is difficult to quantify the processing parameters and predict processing effects. Therefore, this paper establishes a simulation model of magnetic needle in magnetic abrasive finishing by the coupling numerical simulation method of fluid dynamics discrete element method (CFD-DEM) to analyze the working state parameters of the magnetic needle. Through the simulation of actual working conditions, the machining process and parameters of magnetic abrasive finishing are quantified and analyzed, and the motion trend of magnetic needles during the machining process is studied. Then, the residual stress of single magnetic needle impact is analyzed with ABAQUS, and the performance enhancement of the workpiece is predicted. Finally, observations of surface morphology and validation of residual stress prediction were conducted through experiments on an aluminum plate. The results show that the residual stress of the aluminum plate is positively correlated with the number of strikes of the magnetic needle. The residual stress changes from tensile stress (+0.1 MPa) to compressive stress (-16.5 MPa). The comparison between simulation results and experimental results is good, indicating that the simulation model can comprehensively consider multiple factors such as magnetic field, particle motion, and fluid flow, and establish a magnetic needle magnetic grinding process model that is suitable for actual working conditions.

Partial discharge detection is an effective method for evaluating the insulation condition of cable accessories. Ultra-high-frequency method for detecting partial discharge has strong anti-interference ability. Therefore, a broadband, circularly polarized Archimedean planar spiral antenna is used as the partial discharge detection sensor. After determining the antenna parameters through theoretical calculations, simulate and design the antenna. Analyze the influence of different inner diameter values on antenna performance. Exponential gradient microstrip balun is added to achieve impedance matching between the antenna and the coaxial line, and a reflection cavity is added to achieve unidirectional radiation and gain improvement of the antenna. Based on parameter analysis, optimize the design of Archimedean planar spiral antenna and complete the physical production. The test results indicate that the designed Archimedean planar spiral antenna has a gain greater than 6dB and a VSWR less than 2. The performance of the antenna meets the requirements.

超声振动辅助磁粒研磨技术是在磁粒研磨的基础上增加了超声波振动功能,可以在短时间内将表面抛光至纳米级别,因其具有辅助研磨效果佳、可控性和适用性好等优点,在越来越多的领域得到了应用.首先对超声辅助磁粒研磨加工技术的发展概况进行了简要介绍,分别从表面粗糙度、材料去除率、显微组织和残余应力等方面进行了重点分析和总结.其次,超声振动工艺参数是影响研磨效果的重要因素,优化选取振幅、振动频率、主轴转速以及磨料粒径等工艺参数可以明显提高研磨效果.此外还要考虑合适的加工时间和加工间隙,从而对复杂曲面进行精密研磨.最后,提出了超声振动辅助磁粒研磨加工技术研究中存在的一些缺陷,并对其未来的发展趋势进行了展望.

传统喷砂在实践中多以经验为主,缺乏理论支撑.研究喷砂工艺的冲蚀磨损规律及其影响因素.在CFD-DEM耦合的基础上,引入Archardwear模型求解喷砂气固两相流对平板的冲蚀过程,预测颗粒冲击状态和冲蚀区域效果,研究不同的喷射角度、砂粒粒径及供砂速率对平板冲蚀深度总量的影响规律及其变化原因.结果表明:喷砂作用于平板形成的冲蚀区域形貌大致为盆地状,但又因喷射角度的不同会造成类椭圆形或类圆形区域.在控制单因素变量条件下,冲蚀深度总量随着喷射角度增大先缓慢增大至峰值,随后基本上呈线性减小,因此喷砂作业时应尽量保持倾斜,以喷射角度50°为宜,另外,从能量出发,喷射角度50°时法向-切向累积接触能量都相对较大;同时砂粒粒径在0.25 mm＜d＜0.55 mm范围内,冲蚀深度总量下降最快;冲蚀深度总量随供砂速率增大呈线性梯度增大.以数值模拟和试验验证相结合的形式给喷砂工艺提供了一种较为可行的研究方法.

目的 设计一种低频交变磁场发生装置,高效率地去除H62黄铜管内的表面缺陷,提高其表面质量,延长其使用寿命.方法 采用闭合铁芯的方式设计一种低频磁场发生装置,利用EDEM软件对磁场中的磁性磨粒进行运动仿真分析;对电磁线圈的缠绕方式、通电方式进行设计,并利用Ansys软件对不同的线圈缠绕方式和通电方式所产生的磁场进行模拟分析.数控车床夹持管件旋转,并与磁场发生装置相配合,使管件中的磁性磨粒在磁场中磁化,并紧贴管件内表面进行研磨抛光.使用触针式表面粗糙度测量仪和超景深3D电子显微镜,对研磨前后的样品进行检测分析.结果 基于三端缠绕方式,采用2种不同的通电方式对管件进行研磨加工,采用相对型通电方式研磨6 min后,H62黄铜管内的表面粗糙度由原始的0.618μm降至0.373μm.采用相邻型通电方式研磨6 min后,H62黄铜管内的表面粗糙度由原始的0.667μm降至0.081μm.结论 利用低频交变磁场能够实现研磨工具(磁性磨粒)的循环更新,提高磁性磨粒的利用率.在采用三端缠绕方式通电时所产生的磁场强度更大,更适合于磁粒研磨加工.采用相邻型通电方式(N?N?S?S磁极排布)加工时,研磨压力更大,大幅缩短了加工时间,去除了管件内壁的原始缺陷.

In order to discuss the influence of sand particles carried in the transportation of natural gas pipeline on the erosion wear of Ω-shaped pipes, the erosion process of gas-solid two-phase flow in Ω-shaped pipes was numerically simulated by using CFD-DEM coupling and Archard wear model. The movement state of particles and the area where erosion wear is most likely to occur were predicted, and the influences of particle shape, particle size and inlet velocity on the erosion wear of pipe inner wall were studied. The results show that the erosion-prone area of Ω-shaped pipes is the outer ring side walls of four elbows; under the condition of controlled variables, for non-spherical particles, the maximum erosion depth of four elbows increases by 32.1% on average compared with spherical particles. The maximum erosion depth of each elbow decreases with the increase of particle size. When the particle size is small, elbow Ⅳ wears out most seriously; when the particle size is large, the elbow Ⅰ will be damaged and leaked earlier due to the cumulative effect of wear. With the increase of inlet velocity, the maximum erosion depth increases almost linearly from elbow I to elbow Ⅲ; while for elbow Ⅳ, the maximum erosion depth shows a trend of increasing first and then decreasing, reaching the peak when the inlet velocity is 8 m/s. The research results provide reference for the protection and safe operation of Ω-shaped pipes in transportation pipeline systems.

目的 为解决现有铁磁性磨粒中研磨相材料价格昂贵、硬度不够和性价比低等问题,采用碳化硼粉末制备出一种具有成本低和性价比高的新型磁性磨粒.方法 采用黏结法制备铁基碳化硼磁性磨粒,探究制备工艺中不同成分配比对其研磨性能的影响.通过扫描电子显微镜观察磁性磨粒表面形貌,并进行面扫能谱分析观察磨粒中研磨相分布情况;采用表面粗糙度测量仪与3D超景深显微镜对研磨前后的工件表面质量进行对比分析;结合钛合金平板试件的研磨试验结果评价磁性磨粒的研磨性能,最终确定黏结法制备铁基碳化硼磁性磨粒的最佳方案.结果 压制力为100 kN,物料与黏结剂量比为10︰1,粒径比为4︰1时,磁性磨粒的切削刃较为明显,研磨效果达到最佳.使用此磁性磨粒研磨30 min后,钛合金平板试件的表面粗糙度由原始的Ra 0.88μm降至Ra 0.07μm,有效去除了工件原始表面的缺陷和加工纹理,改善了工件的表面质量.结论 在黏结剂中加入无水乙醇可解决黏结剂过于黏稠、不利于与物料混合的问题.采用此黏结法所制备的铁基碳化硼磁性磨粒能够有效地完成对钛合金材料的加工,铁基碳化硼磁性磨粒可以作为性能优良的磨削介质参与研磨,并能够满足磁粒研磨光整加工的要求.

目的 改善传统平面磁粒研磨中轨迹均匀性较差、材料去除不均匀等问题.方法 首先,基于Hilbert分形曲线加工平面,对Hilbert分形曲线进行几何特征的修改,进一步改善研磨轨迹的均匀分布;其次,传统磁粒研磨平面时采用圆柱磁极,其半径方向线速度的差异会导致材料出现去除量不一致等问题,使用环形磁极进行研磨,对不同长径比环形磁极进行三维静磁场模拟仿真,对比不同长径比的磁感应强度和1 mm处的磁场强度曲线,选取最佳的长径比进行研磨,在一定程度上保证材料的均匀去除;最后,利用ADAMS软件进行单个磨粒运动轨迹的仿真,建立笛卡尔坐标网格划分,利用离散系数vC进行轨迹密度的数值分析,对研磨轨迹均匀性进行评价.结果 长径比为3:4的环形磁极的磁感应强度最大,可达300 mT左右.在相同条件下,分别沿传统直线往复式路径、Hilbert曲线和改进的Hilbert曲线进行仿真,经离散系数vC的评定,沿改进Hilbert曲线的研磨轨迹均匀性显著提高,离散系数vC为0.407,较传统往复式的离散系数提高了约43.2％,较Hilbert曲线路径的离散系数提高了约10.7％.沿改进的Hilbert曲线的9个检测点的表面粗糙度降幅基本一致,降幅曲线平缓.原始表面的加工纹理、缺陷被完全去除,研磨后表面形貌均匀平坦.结论 沿改进的Hilbert加工路径进行研磨,研磨轨迹复杂多样,且分布相对均匀,确保了表面材料去除量的均一性,表面质量较好.

目的 解决现有烧结法制备磁性磨粒工艺中存在的研磨相单一、研磨相材料硬度相对较低,以及对于高硬度难加工材质的研磨效率低、质量差等问题,采用立方氮化硼粉末作为研磨相烧结制备一种新型磁性磨粒.方法 采用烧结法制备铁基立方氮化硼磁性磨粒,探究原料的粒径比、烧结温度对磁性磨粒磨削性能的影响,以TC4钛合金板和Si3N4陶瓷板为试验对象,通过表面粗糙度测量仪和3D超景深显微镜对比加工前后工件的表面质量,采用扫描电镜观察加工后磁性磨粒的表面形貌,以此作为磁性磨粒的研磨性能和使用寿命的评价指标,并采用面扫描能谱分析仪观察磁性磨粒中研磨相的分布情况.结果 采用烧结法,以铁粉为基体,以立方氮化硼粉末为研磨相材料,制备磁性磨粒.最终确定压制力为90 kN,基体与研磨相的粒径比为3:1,烧结温度为1180℃,在此条件下制备的磁性磨粒具有良好的磨削性能,相较于烧结法制备的Al2O3/Fe、SiC/Fe磁性磨粒具有更强的磨削性能,可实现Si3N4陶瓷板表面的光整加工,在研磨39 min后可将其表面粗糙度由1.382μm降至0.117μm.结论 采用烧结法制备的铁基立方氮化硼磁性磨粒能够解决硬脆材料的表面质量问题,可以作为性能优异的磨削介质参与研磨,满足磁粒研磨光整加工技术的需求.

目的 提高磁粒研磨加工厚壁管内表面的表面质量与表面粗糙度改善率.方法 采用聚磁盘与瓦形磁极相配合的方式,通过仿真软件对不同数量的瓦形磁极与聚磁盘的多种组合进行模拟仿真,并分析其磁感应强度变化与磁力线分布.利用磁粒研磨法对管件内表面进行研磨试验验证,研磨后对工件表面粗糙度进行测量,并观察工件表面微观形貌.分析瓦型磁极数量、主轴转速以及磁性磨粒粒径对管件内壁表面质量的影响.结果 不设置瓦形磁极时,在主轴转速为600 r/min、磨粒粒径为185μm、研磨时间为15 min的条件下,管件内表面粗糙度由原始的0.42μm左右降低至0.14μm左右,表面粗糙度改善率为67.05％,表面质量有所改善.设置2个瓦形磁极时,在主轴转速、磨粒粒径、研磨时间与不设置瓦形磁极相同的条件下,管件内表面粗糙度从原始的0.42μm左右降低至0.09μm,表面粗糙度改善率为78.57％,表面缺陷被完全去除.结论 聚磁盘与瓦形磁极相配合的磁极排布方式,使得管件内外形成封闭磁回路,增大了加工区域的磁感应强度并改善了磁场分布,工件内表面的微裂纹、凹坑等表面缺陷基本被去除,获得良好的表面加工质量和较高的表面粗糙度改善率.

目的 在传统的平面磁粒研磨加工中添加脉冲辅助磁场,增大加工区域中磁感应强度和加工时磁感应强度动态变化,丰富磨料粒子在加工时的运动形式,使研磨轨迹复杂化,降低工件表面粗糙度,获得更好的工件表面形貌.方法 通过分析磨料粒子在有无辅助磁场时各自的受力情况,探究辅助磁场对磨料在加工时运动状态的影响,研究脉冲辅助磁场下磨料的运动行为机理.利用Ansoft Maxwell软件对电磁铁不同形状的磁极头产生的磁场进行模拟对比,确定理论上最优的磁极头形状.同时模拟对比脉冲电流在不同时刻加工区域内磁感线的分布情况,以及恒定磁场和脉冲磁场下磨料的运动轨迹.通过试验对比无辅助磁场、恒定辅助磁场和脉冲辅助磁场下磁粒研磨加工SUS304不锈钢的表面形貌和表面粗糙度.结果 在磁粒研磨加工中,磁性磨料分布受磁感线的影响,在脉冲辅助磁场的作用下加工区域内的磁性磨料会随磁感线的变化而做周期性的往复运动,加工时会有更为复杂的研磨轨迹.模拟3种不同形状的磁极头在加工区域产生的磁感应强度曲线,平面、圆锥面和半球面在中点处的磁感应强度峰值分别为655、636、702 mT.以SUS304不锈钢板作为试验对象,原始表面粗糙度为0.46μm,采用半球形的电磁铁磁极头,在研磨间隙为2 mm、永磁极转速为800 r/min、进给速度为5 mm/s的试验条件下,对比电磁铁不通电、通入0.8 A直流电流、通入1 Hz,占空比50％,峰值电流0.8 A的单向脉冲电流3种辅助磁场分别对工件研磨30 min后的工件表面形貌,无辅助磁场时工件表面仍残留一些原始纹理;恒定辅助磁场下工件表面原始纹理被去除,但表面存在明显圆弧形研磨痕迹;脉冲辅助磁场下工件表面形貌更为光整、平滑.研磨后工件表面粗糙度分别降至0.28、0.13、0.06μm.结论 脉冲磁场辅助磁粒研磨在提高加工区域磁感应强度的同时,可使磁性磨料在加工时做周期性运动,研磨轨迹复杂化,促进了磨料的更新,相比传统磁粒研磨和恒定辅助磁场磁粒研磨工艺,脉冲磁场辅助磁粒研磨加工后的工件表面形貌更加平滑,表面粗糙度更低.

According to the characteristics of elbow erosion damage position, a new differential processing technology was proposed. Using the flexibility of the manipulator, the machining gap between the inner and the outer side of the elbow was changed in the process of elbow machining, so as to realize the differential grinding of the inner wall of the elbow and improve its surface quality. The results show that when the machining time is 75 min and the machining gap between the inner and the outer side of the elbow is 2.0 mm, the inner surface roughness of the outer arc of the elbow is reduced from 0.70 μm to 0.34 μm, and the inner surface roughness of the inner arc of the elbow is reduced from 0.82 μm to 0.32 μm. During differential grinding, the outer machining gap of the elbow is 1.5 mm, the inner machining gap remains unchanged at 2.0 mm, the inner surface roughness of the outer arc of the elbow is reduced from 0.70 μm to 0.26 μm, and the inner surface roughness of the inner arc of the elbow is reduced from 0.82 μm to 0.29 μm. Differential grinding can effectively improve the inner surface quality of the elbow.

目的 研究在喷砂工艺过程中,喷嘴的收缩角、喉部半径及扩散角3种结构对出砂平均速度和出砂总量的影响规律及原因.方法 利用EDEM-Fluent耦合模型,对喷砂喷嘴内气固两相的运动状态进行模拟,并通过实验验证其正确性.以喷嘴的不同结构大小设置正交表进行仿真实验,运用方差分析法(F检验),分析各因素水平出砂平均速度和出砂总量的变化规律,并利用控制变量法,进一步探究喉部半径对出砂平均速度和出砂总量的影响原因.结果 由出砂平均速度方差分析可得,喉部半径的F值为3716.044,收缩角的F值为380.102,出砂平均速度随着喉部半径的增大而快速增大,随着收缩角的增大而减小.由出砂总量方差分析可得,喉部半径的F值为103.695,收缩角的F值为13.101,出砂总量随喉部半径的增大而快速减小,随着收缩角的增大而缓慢增大.当收缩角和扩散角不变的情况下,随着喉部半径增大,喷嘴内负压增大,导致气相流速增大,进而使出砂平均速度增大.随着喉部半径增大到8 mm时,出砂平均速度不再增大,且有略微下降,其峰值为184.65 m/s.在砂粒生成速率相同的情况下,得出喉部半径越大,砂粒速度越大,砂粒在喷嘴内的停留时间越短,收缩段待喷出的砂粒质量越少,且分布状态越稀疏.结论 验证了EDEM-Fluent耦合模拟喷嘴内气固两相流场是合理可行的.基于这一仿真模型,得出了出砂平均速度及出砂总量分别与喷嘴不同结构参数之间的关系规律,其中喉部半径对两者的影响最为显著.随着喉部半径越大,出砂平均速度越大,单位时间内在喷嘴出口处统计到的砂粒总量越少.

目的 去除焊接管件焊缝处的氧化皮,改善焊缝处的应力状态.方法 采用振动辅助磁针磁力研磨法去除导磁材质管件经焊接处理后焊缝表面的氧化皮,利用超景深电子显微镜观察氧化皮的去除情况;利用X射线能谱分析仪对焊缝表面氧化皮的成分进行分析,根据氧化皮及管件材料主要元素的占比情况,分析检测焊缝表面氧化皮是否被完全去除.结果 焊缝表面氧化皮经振动辅助磁针磁力研磨后被完全去除.通过对比振动辅助磁针磁力研磨前后的表面形貌发现,表面颜色由黑变光亮,氧化皮得到有效去除.通过EDS成分分析可知,氧化皮的主要成分为C元素,质量分数为88.62％;管切面显示基体的主要成分为Fe元素,质量分数为67.09％.通过振动辅助磁力研磨法去除氧化皮后,管表面的元素组成与研磨前相比C元素降低了85.52％,Fe元素增加了63.06％.表面残余应力由原始的+17.5 MPa变为?186.0 MPa.经研磨后,氧化皮基本被完全去除.结论 焊缝表面成分的检测结果证实,从表面形貌分析中得到氧化皮被完全去除的结论是正确的,同时也表明振动辅助磁针磁力研磨对完全去除焊缝表面的氧化皮具有可行性.