基于VERICUT二次开发的粗加工数控代码优化

针对航空钛合金结构件数控粗加工效率低、刀具磨损快、加工过程中切削功率变化较大的问题,基于VERICUT软件二次开发技术进行了粗加工数控代码优化的研究,阐明了常规数控代码编制方法存在问题的原因,给出了识别优化位置的算法和不同情况下数控代码优化的计算方法。测试结果表明：优化后的数控代码加工效率明显提高,刀具磨损程度减小,切削功率变化平稳。提出的优化方法为实现大型航空钛合金结构件安全、高效的数控粗加工技术提供了一种新思路。     

面向高速切削加工的数控编程技术研究

高速加工数控编程技术是高速加工研究的关键内容之一,它极为重要也非常复杂。针对高速切削加工的特点,提出了新的数控加工编程策略,深入分析了高速粗加工和精加工过程中走刀路径的优化。通过这样的优化科学地编出最优、最实际的高速铣削数控加工程序,充分发挥高速铣削加工的特长。从而缩短零件的生产工艺过程,增加切削余量的去除率,提高表面的加工精度。     

钛合金铣削参数多目标优化及神经网络预测模型建立

为有效降低钛合金TC4铣削过程中的刀具磨损及能耗的同时提升效率,以合力弯矩、加工能耗、加工效率为优化目标开展多目标优化研究。通过单因素试验分析切削参数影响规律,通过响应曲面试验建立径向基神经网络预测模型。最后将预测模型整体引入粒子群算法中进行帕累托前沿求解得到若干组合理的切削参数组合。试验结果表明：神经网络预测模型的预测精度达95%以上;多目标优化模型的优化结果可使钛合金铣削加工过程中的合力弯矩减小28.98%、加工效率提高25.93%、加工能耗减少13.08%,可为钛合金铣削加工切削参数的选择及多个生产目标之间的协调提供有力支持。     

钛合金材料的数控加工方法

文章对钛合金的物理性能、化学性能以及切削性能进行了详细地分析.根据产品技术要求,文中介绍了一种新的钛合金电缆端子数控加工工艺方法,其中包括利用加工中心的可编程性合理编制数控加工程序,利用加工中心的操作人性化之特点优化切削参数.文章运用了对比的方法介绍了合理选择刀具几何形状以及采用普通高速钢钻头和立铣刀加工高精度大孔径比钛合金孔的加工工艺路线和措施.并通过实际样件的加工验证了改进刀具、优化切削参数及加工工艺方法的实用性.     

基于航空铸造钛合金Ti-6Al-4V高速铣削参数的表面质量及切削效率优化

目的研究高速铣削参数对航空铸造钛合金Ti-6Al-4V表面质量的影响规律及交互作用,并基于高速铣削参数对表面质量和材料去除率进行优化。方法采用Box-Behnken设计和二次回归正交实验法,建立高速铣削参数与表面粗糙度的显著不失拟回归模型,获得铣削参数影响表面粗糙度的显著性差异,挖掘高速铣削参数交互作用与表面粗糙度的关系;基于表面粗糙度回归模型及材料去除率,采用遗传算法(GA),对高速铣削参数进行多目标优化。结果铣削参数影响航空铸造钛合金Ti-6Al-4V试件表面粗糙度的显著性顺序为:切削深度>每齿进给量>切削宽度>主轴转速,其中切削宽度和主轴转速、每齿进给量和主轴转速的交互作用较为明显。利用遗传算法对铣削参数优化后,Ti-6Al-4V表面粗糙度较优化前提高44%,材料去除率提高70%,遗传算法优化后的试件表面粗糙度显著降低,表面刀路行距减小,纹理平均高度降低。结论由实验验证可知,通过响应曲面建立表面粗糙度显著不失拟回归模型具有较高的预测精度,基于遗传算法优化获得的铣削参数可有效提高表面质量和切削效率,对保证航空铸造钛合金Ti-6Al-4V表面质量具有较好的指导意义。     

基于支持向量机的钛合金铣削加工参数优化

针对钛合金材料在加工过程中受铣削力影响易于产生变形而影响加工效果,属难加工材料,为了保证加工质量,提高生产效率及降低加工成本,其切削加工参数的合理选择非常关键;对钛合金铣削加工进行有限元数值计算,结合试验设计方法构建了基于支持向量机的切削力预测模型,提出了一种基于支持向量机和遗传算法的优化方法,对钛合金铣削工艺参数进行了优化;结果表明,该方法准确、高效、可行,为钛合金加工工艺参数优化提供一种新的思路,具有良好的推广价值。     

数控铣床逻辑进给振动铣削的试验研究

研究利用数控铣床的逻辑控制系统进行工作台的脉冲式的进给,实现脉冲切削力作用的分离型的数控振动铣削。研究了脉冲振动方向沿进给方向的振动铣削和脉冲振动方向与进给方向成一定角度的振动铣削过程,并对铣削过程进行了切削力对比试验。试验结果表明：脉冲振动方向与进给方向成一定角度的振动铣削可以降低铣削力,强化铣削过程,降低切削温度,对表面粗糙度影响不大;随进给路线、逻辑关系的不同,切削效果差别很大。     

高速铣削钛合金TC4切削力试验研究及切削参数优化

采用正交试验研究了高速铣削钛合金TC4粗加工阶段时切削参数对切削力的影响规律，并以Y向切削力最小和材料去除率最大为优化目标，利用MATLAB基于Pareto遗传算法优化高速铣削TC4的切削参数，结合Pareto最前沿给出了优化后的切削参数最优解集。     

数控铣床切削数据库的建立及应用

数控铣床已广泛应用于我国模具加工中，但其切削参数往往由操作者任经验给出，带有一定的盲目性，为解决这些问题，我们对切削参数数据库的技术进行一般性研究，建立了一个铣削参数数据库，可根据加工条件选择铣削参数，同时把这些参数转化为CAM软件的切削参数文件，供加工中方便使用。     

提高数控铣床加工效率的有效途径

从刀具管理、工件装夹定位、编程和切削方式等多方面着手，采取相应的办法，减少装夹、定位、重复换刀等辅助时间，缩短编程时间，提高机床利用率。用干式切削方式，避免数控铣床没有封闭防护罩不能进行大喷流冷却切削的缺陷，改善加工条件，提高切削效率，从而达到提高数控铣床加工效率的目的。     

Machinability of hypereutectic silicon-aluminum alloys

The machinability of high-silicon aluminum alloys made by a P/M process and by casting was compared. The cutting test was conducted by turning on lathes with the use of cemented carbide tools. The tool wear by machining the P/M alloy was far smaller than the tool wear by machining the cast alloy. The roughness of the machined surface of the P/M alloy is far better than that of the cast alloy, and the turning speed did not affect it greatly at higher speeds. The P/M alloy produced long chips, so the disposal can cause trouble. The size effect of silicon grains on the machinability is discussed.     

高硬度航空合金铣削颤振研究进展

高硬度、高强度合金在航天航空领域的应用越来越广泛,但这类合金在铣削过程中存在铣削力过大而容易引起刀具颤振的问题,而刀具颤振会降低工件的最终表面质量和生产效率。为了减少刀具颤振对加工质量的影响,铣削颤振稳定性预测被广泛应用于高硬度合金铣削的研究中。综述了高硬度航空合金铣削过程颤振稳定性分析的研究现状,重点阐述再生型颤振的动力学建模,分析刀具颤振与磨损的相互关系,介绍了近年来铣削颤振稳定性研究中抑制颤振的研究成果。     

Machinability aspects of new Al–Cu alloys intended for automotive castings

This study was undertaken to investigate the machinability aspects of four new Al–Cu casting alloys with regard to the drilling and tapping processes; the base alloy is the 220 Al–2%Cu–1.3%Si–0.4%Mg alloy from which the other three alloys were prepared through the addition of TiB₂ and Zr, Sn, and Bi. The machining performance was evaluated based on the calculation of the total cutting force and moment together with that of the tool life expressed as the number of holes drilled/tapped up to the point of tool breakage. The evaluation range was limited by a predefined targeted tool life of 2520 holes corresponding to 14 machinability test blocks. The results show that more than 2520 holes can be drilled for all the alloys studied without drill breakage. The addition of Sn and Bi decreases the total drilling force over the evaluation range by 14% and 25%, respectively, compared to the base alloy. The total drilling moment was reduced by almost the same ratios. All the alloys studied produce a fan-shaped chip which is considered to be the ideal chip for most drilling applications. The addition of Bi increases chip fragility considerably whereas no distinct change in chip characteristics was caused by the addition of Sn. No significant drill wear or any outstanding change in the built-up edge (BUE) to be observed with the progress of the drilling process. A comparative study was also carried out on the machining behavior of these new alloys, represented by their base 220 alloy, with that of the A206, 356, B319, and A319 alloys. Results revealed that the 220 alloy may be proposed as a promising cheaper and lighter alternative for the machining application of the A206 alloy. Furthermore, the machinability of the 220 alloy may be deemed an acceptable compromise between that of the 356 and B319 alloys, on the one hand, and that of the A319 alloy on the other.     

Effects of Fe intermetallics on the machinability of heat-treated Al–(7–11)% Si alloys

The need for bridging the divide between the casting process and the machining process provides a strong motivation for examining the various aspects affecting the machinability of Al–Si casting alloys, given that these alloys constitute about 85% of all aluminum castings produced. Strontium-modified, grain-refined, T6 heat-treated 396 alloys (containing ～11% Si), and B319.2 and A356.2 alloys (containing ～7% Si) were selected, with a view to studying their machinability characteristics. Three 396 alloy compositions were selected (M1, M3, M4) such that different iron intermetallic phases were obtained in each case. Drilling and tapping operations were both carried out using a Makino A88E machine under fixed machining conditions. The machinability criteria relates to forces and moment analysis as well as to tool life, chip configuration, and built-up edge (BUE) evolution. The effects of Fe-intermetallics (α-Fe, β-Fe, and sludge) on the machining characteristics of these alloys were investigated and a comparison was made between the three 396 alloys in terms of mean total drilling forces, mean total tapping forces, tool life, and chip configuration. The results demonstrate that the presence of sludge has a significant effect on cutting forces and tool life. The tool life of the 396-M3 alloy (containing sludge) decreased by 50% compared to the base alloy 396-M1 (containing α-Fe intermetallics). Increasing the Fe-content from 0.5% to 1% in the M1 alloy (i.e., M4 alloy) produces a distinct improvement in the alloy machinability in terms of cutting forces and tool life. The addition of Fe and Mn appears to have no discernible effect on the built-up-edge (BUE) width and chip configuration as compared to the base alloy. The dominant type of wear which leads to drill failure and breakage is outer corner wear; there is, however, no evidence of crater-wear. Fan-shaped chips were obtained during machining of the 396, B319.2 and A356.2 alloys, where the latter alloy yielded the largest chips. As far as the alloy Si content was concerned, it was found that the 396 alloys produce drilling results similar to those of the B319.2 and A356.2 alloys, in terms of the number of holes drilled (cf. 2160 with 2100 and 2285 holes drilled in the B319.2, and A356.2 alloys, respectively). During tapping tests, however, the B319.2 alloy yielded the longest tool life, i.e., more than twice that of 396 alloy and four-and-half-times that of the A356.2 alloy.     

生物医用植入钛及钛合金的力学性能研究及进展

生物医用植入纯钛具有低密度、优越的耐蚀性、无致敏性和良好的生物相容性，而医用植入钛合金还具有高比强度、较低的弹性模量及易加工等优良特点。所以生物医用植入钛及钛合金已成为外科植入件优选的替代材料。本文重点介绍了人体硬组织修复与替换材料新型钛合金的生物相容性、力学性能、合金添加元素对力学性能的影响和最新研究进展，并指出了未来研究的发展方向。     

The Correlation of Machinability and Microstrutural Characteristics of Different Extruded Aluminum Alloys

This work correlates metallurgical characteristics (chemical composition, microstructure and morphology of second phase particles) of different extruded aluminum alloys with their machinability as determined by the measurement of axial forces and shear momentum involved in drilling operations. Three different aluminum alloys were evaluated. The alloy AA6061 with low and high P content was tested in the recrystallized condition while alloys AA6351 and AA2117 were tested in the cold-worked condition. Specimen characterization also included tensile and hardness tests, chemical and microstructural evaluation. The results have shown that Pb and Cu have a positive effect on the machinability of these alloys and that the microstructure control may decrease forces in machining, resulting in great improvement of production in cutting procedures.     

Analysis of a free machining α+β titanium alloy using conventional and ultrasonically assisted turning

Rapid advancements in power generation and aviation industries have witnessed a widespread use of titanium and its alloys in many applications. This is primarily due to their excellent mechanical properties including, amongst other, high strength-to-density ratio, outstanding fatigue properties and corrosion resistance with the ability to withstand moderately high temperatures. However, this combination of properties results in poor machinability of the material, increasing the cost of components machined with conventional cutting techniques. Recently, Ti 6Al 2Sn 4Zr 6Mo, a modern titanium alloy with improved mechanical properties, has been introduced as a possible replacement of Ti 6Al 4V in aerospace industry. However, its poor machinability and formation of long chips in conventional turning are main limitations for its wide-spread application. Therefore, a new alloy based on Ti 6Al 2Sn 4Zr 6Mo, namely Ti 6Al 7Zr 6Mo 0.9La, was developed; it shows enhanced machinability generating short chips during metal cutting, which prevents entanglement with cutting tools improving productivity. To further enhance the machinability of this material, a novel hybrid machining technique called ultrasonically assisted turning (UAT) was used. Experimental investigations were carried out to study the machinability, chip shapes, cutting forces, temperature in the process zone and surface roughness for conventional and ultrasonically assisted turning of both alloys. UAT shows improved machinability with reduced nominal cutting forces, improved surface roughness of the machined workpiece and generation of shorter chips when compared to conventional machining conditions.     

Modified material constitutive models for serrated chip formation simulations and experimental validation in machining of titanium alloy Ti–6Al–4V

Titanium alloys present superior properties such as high strength-to-weight ratio and resistance to corrosion but, possess poor machinability. In this study, influence of material constitutive models and elastic–viscoplastic finite element formulation on serrated chip formation for modeling of machining Ti–6Al–4V titanium alloy is investigated. Temperature-dependent flow softening based modified material models are proposed where flow softening phenomenon, strain hardening and thermal softening effects and their interactions are coupled. Orthogonal cutting experiments have been conducted with uncoated carbide (WC/Co) and TiAlN coated carbide cutting tools. Temperature-dependent flow softening parameters are validated on a set of experimental data by using measured cutting forces and chip morphology. Finite Element simulations are validated with experimental results at two different rake angles, three different undeformed chip thickness values and two different cutting speeds. The results reveal that material flow stress and finite element formulation greatly affects not only chip formation mechanism but also forces and temperatures predicted. Chip formation process for adiabatic shearing in machining Ti–6Al–4V alloy is successfully simulated using finite element models without implementing damage models.     

Comparison of the machinabilities of Ti6Al4V and TIMETAL® 54M using uncoated WC–Co tools

Single-point turning tests of cylindrical bars were undertaken to analyse and compare the machinability of Ti6Al4V, the most common titanium alloy, and TIMETAL^® 54M, a newly developed alloy with similar mechanical properties as Ti6Al4V but with better machinability. Conventional cooling and uncoated WC–Co tool inserts were used in the study, because they are the most recommended for machining these materials. The feed and the depth of cut were maintained constant, and only the cutting speed was varied because it is the most affecting parameter. Adhesion of workpiece material in the form of a built-up edge appeared in all the cutting inserts after machining both alloys, which was removed for flank- and crater-wear measurements. Lower wear rates were observed for the Ti54M alloy, especially at high cutting speeds. In the same manner, cutting-force measurements showed lower specific cutting- and feed-force values for the Ti54M alloy. Adiabatic shear bands, a typical feature in the machining of titanium alloys, were observed in chips from both alloys under all cutting conditions. Finally, scanning electron microscopy observations were carried out to analyse the adhered material on the cutting edges of the worn tools where signs of diffusion and attrition were detected.     

BT20钛合金筒形件真空热胀形过程热力耦合有限元分析

建立了BT20钛合金筒形件真空热胀形的二维非线性准静态热弹塑性有限元模型。该模型考虑了辐射传热和材料热物性非线性等因素的影响。使用有限元软件MSC．Marc对BT20钛合金筒形件真空热胀形过程进行数值模拟,计算了BT20钛合金筒形件真空热胀形过程的温度场、变形场和应力场,并进行了相应的实验验证。数值模拟结果与实验结果吻合较好,说明了所建立的热力耦合模型的有效性。