Electromagnetic superposed forming of large-scale one-dimensional curved AA2524-T3 sheet specimen

This study proposes a methodology for helical mill-grinding of tiny internal threads made of hard brittle materials such as SiCp/Al composites. The methodology uses the helical mill-grinding method incorporating with a diamond form-grinding wheel. A mathematical model is established to predict thread form errors and provide a rational range of wheel parameters, such as variation of tool profile angle Δα and ratio of the wheel diameter to the thread major diameter η. Based on the methodology, a grinding wheel is developed for processing the M2 internal threads in a validation experiment. The study demonstrates that an M2 internal thread made of the SiCp/Al composite of 45% SiC volume fraction is successfully machined in 5 min with pitch error <0.08% and angle error <0.3%. The thread profile on the pitch diameter is within the axial equivalent tolerance zone (0–0.016 mm), which indicates that the thread precision reaches the H4 level.     

Face Grinding Surface Quality of High Volume Fraction SiCp/Al Composite Materials

The existing research on SiCp/Al composite machining mainly focuses on the machining parameters or surface morphology.However,the surface quality of SiCp/Al composites with a high volume fraction has not been extensively studied.In this study,32 SiCp/Al specimens with a high volume fraction were prepared and their machining parame-ters measured.The surface quality of the specimens was then tested and the effect of the grinding parameters on the surface quality was analyzed.The grinding quality of the composite specimens was comprehensively analyzed taking the grinding force,friction coefficient,and roughness parameters as the evaluation standards.The best grinding parameters were obtained by analyzing the surface morphology.The results show that,a higher spindle speed should be chosen to obtain a better surface quality.The final surface quality is related to the friction coefficient,surface roughness,and fragmentation degree as well as the quantity and distribution of the defects.Lower feeding amount,lower grinding depth and appropriately higher spindle speed should be chosen to obtain better surface quality.Lower feeding amount,higher grinding depth and spindle speed should be chosen to balance grind efficiently and surface quality.This study proposes a systematic evaluation method,which can be used to guide the machining of SiCp/Al composites with a high volume fraction.     

An experimental study on formation mechanisms of edge defects in orthogonal cutting of SiCp/Al composites

In this study, orthogonal cutting of SiCp/Al composites with a polycrystal diamond tool has been carried out. The influences of cutting velocity, cutting depth, and tool rake angle on the cutting force and edge defects near the exit of orthogonal cutting were analyzed in detail. The research results show that the influence of the cutting depth on cutting force is most obvious, and there is a close relationship between the cutting force and the size of edge defects. At the same time, the fractographs indicated that the brittle fracture mode corresponds to the dominant failure mode during machining of SiCp/Al composites with higher volume fraction and larger SiC particle. Therefore, in the precision and super-precision manufacturing of SiCp/Al composites, with a proper tool rake angle, adopting higher cutting velocity and lower cutting depth not only can reduce the cutting force effectively but also can ensure cutting edge quality.     

高体积分数SiCp/Al复合材料旋转超声铣磨加工的试验研究

由于大量高硬度增强相SiC颗粒的存在,高体积分数铝基碳化硅（SiCp/Al）复合材料的机械加工十分困难。旋转超声加工被认为是加工这种材料的有效方法。通过超声辅助划痕试验,分析高体积分数SiCp/Al复合材料旋转超声铣磨加工的材料去除机理。在超声振动的作用下,材料中铝基体发生塑性变形,其表面得到夯实;SiC增强相被锤击成细小的颗粒而发生脱落,形成较大的空洞。由于材料加工的缺陷大多产生于SiC颗粒的去除过程中,SiC颗粒的去除方式对加工表面的质量起着决定性的作用,选择合适的工艺参数可以有效提高加工表面质量。旋转超声加工工艺特征试验表明,超声振动可有效降低切削力;主轴转速对轴向切削力的影响最大,其次是进给速度,切削深度对轴向切削力的影响较小;另外主轴转速对表面质量的影响效果也最大,并随主轴转速的增大表面粗糙度增大。因此在加工过程中,可以适当加大切削深度,在保证加工质量的基础上,选择较大的进给速度,在保证刀具寿命的前提下,选择合适的主轴转速,以获得较优的加工表面质量和加工效率。     

Selection of optimal process parameters in WEDM while machining Al7075/SiCp metal matrix composites

Aluminium metal matrix composites (MMCs) reinforced with silicon carbide particulate (SiCp) find several applications due to their improved mechanical properties over the conventional metals for a wide variety of aerospace and automotive applications. However, the presence of discontinuously distributed hard ceramic in the MMCs made them as difficult-to-cut materials for conventional machining methods. The wire electrical discharge machining (WEDM), as a widely adopted non-traditional machining method for difficult-to-cut precision components, found an appropriate metal removal process for MMCs to enhance quality of cut within the stipulated cost. While machining the advanced materials like MMCs, a clear understanding into the machining performance of the process for its control variables could make the process uncomplicated and economical. In light of the growing industrial need of making high performance-low cost components, the investigation aimed to explore the machining performance characteristics of SiCp reinforced Al7075 matrix composites (Al7075/SiCp) during WEDM. While conducting the machining experiments, surface roughness, metal removal rate, and wire wear ratio are considered the responses to evaluate the WEDM performance. Response surface methodology is used to develop the empirical models for these WEDM responses. SiC particulate size and volume percentages are considered the process variables along with pulse-on time, pulse-off time, and wire tension. Analysis of variance (ANOVA) is used to check the adequacy of the developed models. Since the machining responses are conflicting in nature, the problem is formulated as a multi-objective optimization problem and is solved using the Non-dominated Sorting Genetic Algorithm-II to obtain the set of Pareto-optimal solutions. The derived optimal process responses are confirmed by the experimental validation tests, and the results are analyzed by SEM.     

Slotted-electrical discharge diamond cut-off grinding of Al/SiC/B4C hybrid metal matrix composite

Advanced manufacturing industries need materials with high strength and low weight in the fields of advanced engineering, such as automobiles and aeronautics. Metal matrix composites (MMCs) are one of the advanced engineering materials that meet the above requirements. To enhance the properties of MMCs, researchers added an additional phase of reinforcements into single reinforced MMCs; such developed MMCs are known as hybrid MMCs. The additional phase of reinforcements enhances the properties of MMCs, but simultaneously leads to rapid tool wear and poor machinability. This study developed an innovative hybrid machining process (HMP) consisting of electrical discharge grinding and diamond grinding in such a way that both the processes occur alternately with equal intervals due to the rotation of a slotted abrasive grinding wheel. The performance of the hybrid process was tested on an Al/SiC_p/B₄C_p work-piece in cut-off grinding mode. The experiments were conducted on an electrical discharge machining machine, which consists of a separate attachment on a vertical column to rotate the wheel. Pulse current, pulse on-time, pulse off-time, wheel RPM, and abrasive grit number were taken as input parameters while material removal rate (MRR) and average surface roughness were taken as output parameters. Result were shown that the HMP gives higher MRR with better surface finish as compared to the constituent processes. Pulse current ranging from 3 A to 21 A, pulse on-time ranging from 30 μs to 200 μs, and pulse off-time ranging from 15 μs to 90 μs were also found to be more suitable for higher MRR, and a wheel RPM at 1300 RPM was more suitable for higher MRR with better surface finish.     

颗粒增强铝基复合材料小直径孔磨削加工实验研究

文中使用电镀金刚石砂轮进行A12024／SiCp复合材料小直径孔的磨削加工实验。实验结果表明，利用磨削方法对孔进行加工可以避免出现崩边和崩角缺陷，保证孔的完整；孔的入口和出口尺寸基本一致，孔直径略大于砂轮直径。孔壁的表面粗糙度较低，在实验所采用的加工参数条件下粗糙度在RaO．347-0．578之间。     

Experimental study of high-speed milling of SiCp/Al composites with PCD tools

In this paper, high-speed milling experiments on silicon carbide particle reinforced aluminum matrix (SiCp/Al) composites with higher volume fraction and larger particles were carried out using polycrystalline diamond (PCD) tools at dry and wet machining conditions. For comparison, a TiC-based cermet tool was also used in milling the same workpiece material at very low speed. Worn PCD and cermet tools were measured and extensively characterized by scanning electron microscopy at different machining conditions. Furthermore, the effect of cutting distance on milling force and surface roughness were also investigated. The results showed that the main tool wear mechanism in machining of this type of material was abrasion on the flank face, and it was verified that the TiC-based cermet tool was not suitable for machining SiCp/Al composites with higher volume fraction and larger particles due to the heavy abrasive nature of reinforcement.     

冲刺2018 山高刀具实力全面提升 山高刀具大中华区总经理Bo Udsen先生媒体见面会在北京举行

<正>10月16日,山高刀具大中华区总经理Bo Udsen先生媒体见面会在北京举行,来自全国各地的媒体记者近30人出席。Bo Udsen为山高刀具丹麦前董事总经理,于8月1日起,Bo Udsen被正式任命为山高大中华区董事总经理,他将在上海任职并向负责亚太地区的山高刀具副总裁汇报。     

Fabrication and characterization of 7075 Al alloy reinforced with SiC particulates

7075 aluminum (Al) alloy as matrix and silicon carbide (SiC) as reinforcement has been identified since it has potential applications in aircraft and space industries because of lower weight to strength ratio, high wear resistance and creep resistance. Thorough investigations about the microstructure and characterization of Al alloy/SiC composite are needed so that metal matrix composites (MMCs) fabricated for aircraft and space industries are defect free and have sound microstructure. Objective of this research work are the fabrication and microstructural investigations of AA7075–SiCp MMCs. 7075 Al alloy is reinforced with 10 and 15 wt.% SiCp of size 20–40 μm by stir casting process. The resulting as-cast composite structures are analyzed using scanning electron microscopy, X-ray diffraction (XRD), differential thermal analysis, and electron probe microscopic analysis (EPMA). SiCp distribution and interaction with 7075 Al alloy matrix is studied. The 7075 Al alloy–SiCp composite microstructure showed excellent SiCp distribution into 7075 Al alloy matrix. In addition to this, no evidence of secondary chemical reactions is observed in XRD and EPMA analysis. Decomposition step in derivative thermogravimetric curve is seen at temperature of 1,257, 1,210, and 1,256 °C for 7075 Al alloy, AA7075/10 wt.%/SiCp (20–40 μm) and AA7075/15 wt.%/SiCp (20–40 μm) composites, respectively. So, these composites can be successfully used for applications where temperature does not exceed beyond 1,250 °C.     

电镀金刚石砂轮端面磨削2024Al／SiCp的实验研究

用电镀金刚石砂轮对SiC颗粒增强铝基复合材料2024Al／SiCp进行了端面磨削实验研究。结果表明,端面磨削能获得高质量加工表面;已加工表面残余应力为压应力;磨削参数对切向和法向磨削力影响较小,但对轴向磨削力影响较大,且轴向磨削力随着磨削深度的增加而明显增大。     

Drilling characteristics of SiCp/Al composites with electroplated diamond drills

SiCp/Al composites are extensively used in aerospace, automotive, and civil applications, and the machining characteristic of SiCp/Al composites is an issue of great economic impact. This paper presents an experimental investigation of the drilling characteristics during machining of SiCp/Al composites with electroplated diamond drills; the drilling characteristics were evaluated in terms of drilling forces, tool wear, surface roughness, and entrance edge quality. Due to the very different machining properties between the SiC particles and Al alloy matrix, in a broader sense, the edge defect is defined as an undesirable effect generated at the edge of a workpiece after the machining process. The results demonstrate that with the increase of the drilling speed, both the thrust force and torques have no significant increase, while the surface roughness increased quickly. In addition, it is found that the formation of the entrance edge defects was associated with the varying of the drilling force and the electroplated diamond drills were subjected to an extremely rapid flank wear. The primary wear mechanism includes abrasive and adhesive wear of the flank face.     

高速铣削高体积分数SiCp/Al复合材料表面形貌及切屑机制的研究

为了研究高体积分数SiCp/Al复合材料的切削机理及工件表面形貌,采用PCD刀具对干式切削和水溶性冷却液浇注冷却的湿式切削两种切削条件下的高速铣削进行了研究。结果表明,在对颗粒尺寸大、体积分数高的SiCp/Al复合材料进行高速铣削时,干式切削无论是在工件已加工表面形貌和微观结构,还是在切屑形成及形貌上,都好于湿式切削。两种切削条件下均可获得较理想的表面粗糙度。     

SiCp/Al复合材料钻削加工的有限元和试验研究

为了研究碳化硅颗粒增强铝基(SiCp/Al)复合材料钻削加工的棱边缺陷,通过对工件和钻头进行二维简化建模以及对工件的网格划分,利用ABAQUS/Explicit中的动力显示模块进行钻削模拟。通过改变每齿进给量fy观察复合材料的棱边缺陷,并对仿真结果进行分析,同时和试验结果进行对比。结果表明:工件的棱边缺陷的大小随着进给量的大小而呈线性变化,此结果与试验结果大体一致。该研究可为进一步研究碳化硅铝基(SiCp/Al)复合材料的棱边缺陷提供理论依据。     

SiC_p/Al复合材料铣削残余应力的有限元分析

SiC_p/Al复合材料属于典型难加工材料,大量Si C颗粒离散分布其中,导致在铣削加工高体积分数SiC_p/Al复合材料时,加工表面容易出现应力分布不均现象,严重影响材料的稳定性。为了研究SiC_p/Al复合材料加工表面残余应力,通过ABAQUS有限元分析软件建立了SiC_p/Al复合材料三维铣削有限元模型,并分析了切削工艺参数对残余应力的影响。结果表明:切削速度对残余应力变化影响较小,每齿进给量对残余应力变化影响较大,所得结果与经验计算值吻合较好。     

SiCp/Al复合材料高速切削的研究现状

介绍了SiCp/Al复合材料的特点、应用现状和加工难度,综合评述了SiCp/Al复合材料高速切削的国内外研究现状,分析了目前存在的主要问题及今后的研究方向。     

Drilling of hybrid aluminium matrix composites

This paper presents the influence of cutting parameters on thrust force, surface finish, and burr formation in drilling Al2219/15SiCp and Al2219/15SiCp-3Gr composites. The composites were fabricated using the liquid metallurgy method. The tools used were commercially available carbide and coated carbide drills. The results revealed that feed rate had a major influence on thrust force, surface roughness, and exit burr formation. Graphitic composites exhibit lesser thrust force, burr height, and higher surface roughness when compared to the other material. The reduced thrust force and burr height is attributed to the solid lubricating property of the graphite particles. The higher surface roughness value for Al2219/15SiCp-3Gr composite is due to the pullout of graphite from the surface. The chips formed when machining graphitic composites are more discontinuous when compared to SiCp reinforced composites and hence advantageous.     

SiC_p/Al复合材料的超精密车削试验

试验研究了碳化硅颗粒增强铝基复合材料(SiCp/Al)的超精密车削加工性能.使用扫描电镜(SEM)对已加工表面、切屑及其根部、刀具前/后刀面磨损带进行观察,使用表面粗糙度轮廓仪对各种切削条件下的加工表面粗糙度轮廓进行测试分析.结果表明,该材料的加工表面常残留微孔洞、微裂纹、坑洞、划痕、残留物突起及基体材料撕裂等微观缺陷,刀具几何参数、切削速度、进给量、增强颗粒尺寸和材料体积分数是影响表面粗糙度的主要因素.由于切削变形区微裂纹动态形成的作用,超精密切削该材料时一般形成锯齿型切屑.刀具-工件的相对振动、基体撕裂增强颗粒拔出、破碎、压入等是该材料超精密车削表面形成的主要机制.单晶金刚石(SCD)刀具主要发生微磨损、崩刃、剥落和磨粒磨损,聚晶金刚石(PCD)刀具主要发生磨粒磨损和粘结磨损.结论表明SiCp/Al的超精密切削加工性较差,但通过选择合适的工艺参数,体积分数为15%的SiCp/2024Al加工表面粗糙度Ra可达24.7 nm.     

SiCp/Al复合材料加工边缘断裂特性分析

应用线弹性断裂力学有限元法计算了SiCp/Al复合材料加工边缘的应力强度因子,定量地表征了工件边缘材料的断裂特性。建立了棱边缺陷形成的力学模型和数学模型。根据断口微观结构特征得出:裂纹的萌生扩展是棱边缺陷形成的主要原因。统计分析了棱边缺陷体积与切削力的二次回归数学模型,获得了棱边缺陷体积随切削力的增加呈非线性单调递增的特性。     

钛合金大直径孔螺旋铣削工艺优化研究

本文基于螺旋铣孔技术,采用正交试验和极差值分析方法,在钛合金上进行了19.05mm直径孔的螺旋铣削试验。分析了不同切削参数对轴向切削力、钛合金孔径、粗糙度等的影响,以此为指标优化出最佳工艺参数。在此基础上研究了最佳参数下切削力、加工质量和刀具磨损随加工孔数的变化,发现在大直径孔加工中,螺旋铣孔技术可有效改善加工质量、提高加工效率。