面向绿色制造的工艺种类选择及参数优化

绿色工艺规划是实施绿色制造的重要环节,而工艺种类选择是绿色制造工艺规划的首要内容,在对TQCRE(time、quality、cost、resources、enviroment effect)分析的基础上提出了面向绿色制造工艺种类选择的总体要求和五项基本原则,以及种类选择的模糊评判方法,建立了评价指标体系和评价矩阵,并提出了工艺参数优化的数学模型及研究方法,通过数据库设计、软件开发对模糊评判方法和工艺参数优化开发了友好软件操作界面,最终实现了工艺参数优化的最优方案选择。     

Concurrent design process analysis and optimization for aluminum profile extrusion product development

Owing to intricate interdependency and information feedback among tasks, the concurrent design process probably cannot converge to the correct solution when there are wrong integration and improper interaction between activities. Therefore research on concurrent design process optimization is necessary. In the paper, a novel methodology is proposed to analyze and optimize the concurrent engineering process scientifically. Based on design structure matrix and graph theory, coupled task recognition and design task level plotting are performed for the concurrent design process of aluminum profile extrusion product development. Three factors are used to describe the coupling property of activity, namely sensitivity, complexity and affection factors, which provide the basis to analyze development process quantitatively. And an optimism algorithm is presented to define the initial iteration order of coupled task set. Finally a rational and efficient concurrent design process model is constructed, which can make aluminum profile product development faster, with lower costs and higher quality. The methodology proposed is also applicable to other concurrent engineering fields.     

A study of three-body particle generation and subsequent pole tip recession in linear tape recording heads

The Pole Tip Recession (PTR) and transferred material (stain) are major causes of magnetic spacing losses in magnetic recording system. The recorded signal amplitude is only independent of the data being read if the spacing is zero. Thus, the level and more specifically the variation in head media spacing with device life must be a minimum to maximise signal output and minimised errors. It was the purpose of this research to isolate and identify the mechanisms responsible for pole tip recession using the Linear Tape Open format as an experimental platform, but the results have implications for any head where the tape-bearing surface is Al₂O₃/TiC (AlTiC).All experiments were conducted within a matrix of pressure and humidity, which encompassed the system operating extremes. Atomic force microscopy (AFM) was used to analyse the surface topography of the heads and monitor the development of PTR after 100, 1000 and 5000 passes of tape. Auger electron spectroscopy (AES) was employed to analyse the chemical changes on the surface of the heads after 5000 passes of tape and X-ray Photoelectron Spectroscopy (XPS) was used to identify the chemical changes that occurred at the head surfaces. Optical Microscopy was employed to identify the head surface changes before and after wear. Environment was found to have a significant influence on the head/tape interface. Head wear and PTR were highest at high temperature and humidity.Wear between the head and tape was found to transform the surface layers on the TiC grains in the tape-bearing surface to TiO₂. This process results in the production of TiO₂ fragments that become trapped in the recessed pole tip region, acting as three-body abrasive particles. The presence of Ti on the surface of head thin film region confirmed that the three-body particles originated from the head AlTiC ceramic. The TiO₂ (thickness and possible areal coverage) increased with the water content increase, wear of head increased in the high water content condition.     

Tribological properties of ZrO2 (Y2O3)-Mo-BaF2/CaF2 composites at high temperatures

ZrO₂ (Y₂O₃) with different contents of BaF₂/CaF₂ and Mo were fabricated by hot pressed sintering, and the tribological behavior of the composites against SiC ceramic was investigated from room temperature to 1000 °C. It was found that the ZrO₂ (Y₂O₃)-5BaF₂/CaF₂-10Mo composite possessed excellent self-lubricating and anti-wear properties. The low friction and wear were attributed to enhanced matrix and BaMoO₄ formed on the worn surfaces.     

基于三维加工特征的工艺优化设计系统

三维CAD/CAPP的应用要求表明,三维工艺设计不仅要解决不同设计与工艺模型之间的数据获取与传输,而且还要考虑工艺优化的环境与全局性.利用基本几何面单元来表达三维加工特征并结合特征的制造信息和资源约束,建立了基于设计模型与工艺模型的统一数据模型;然后在工艺准则、资源加工能力和用户自定义的约束条件下进行工艺优化;最后根据生产环境进行综合评价并选择最优的工艺方案.     

Tribological Behaviour of Nanostructured Al2O3-3 wt% TiO2 Coating Against Steel in Dry Sliding

Nanostructured and conventional Al₂O₃-3 wt% TiO₂ coatings were deposited by atmospheric plasma spraying. The wear and friction properties of both coatings against a steel ball under dry friction conditions were examined. It was found that the wear resistance of the nanostructured Al₂O₃-3 wt% TiO₂ coating was superior to that of the corresponding conventional counterpart. The improvement in wear resistance of the nanostructured coating was attributed to its higher toughness and cohesion strength between splats. As for the nanostructured coating, the wear mechanism was mainly adhesion with micro-abrasion at low loads (20 N). At high loads (80 N), the wear of the nanostructured coating was controlled by plastic deformation and associated delamination along the splat boundaries, which was similar to that of the conventional coating at low loads. However, the failure of the conventional coating was predominantly brittle fracture within the splats and delamination between splats at high loads.     

Micro removal of ceramic material (Al2O3) in the precision ultrasonic machining

Ultrasonic machining process is an efficient and economical means of precision machining of ceramic materials. However, the mechanics of the process with respect to crack initiation and propagation, and stress development in the ceramic workpiece subsurface are still not well understood. This article presents experimental simulation of the process mechanics in an attempt to analyze the material removal mechanism in machining of ceramic (Al₂O₃). It is found that low-impact force causes only structural disintegration and particle dislocation. The high-impact force contributes to cone cracks and subsequent crater damage.     

Preparation of TiO2 nanowire gas nanosensor by AFM anode oxidation

Applications of atomic force microscopy (AFM) to the fabrication of chemical nanosensors are presented in this paper. Using AFM cantilever as cathode, the surface of Ti thin film is oxidized to form a few tens of nanometers wide oxidized metal semiconductor wire, which works as a nanowire-based hydrogen sensor. The reaction mechanism is proposed. The AFM observations of fabrication of a TiO₂ nanowire are carried out. The sensitive characteristic of such TiO₂ nanowires to hydrogen is investigated.     

机械结构参数化三级优化设计方法研究与实现

针对传统设计方法的设计结果安全系数过高、结构材料浪费严重的问题,在深入研究优化设计方法的基础上,根据现有优化设计方法的不足,提出机械结构的参数化三级优化设计方法。通过建立统一数据管理机制,将优化设计与参数化设计技术相结合,在基于变密度法的拓扑优化设计与单元生死技术的基础上,以结构最大柔度为优化目标,体积和平衡条件为约束条件,小密度单元为杀死单元,实现了参数化的连续体结构拓扑优化;研究了基于拓扑优化结果数据的参数化CAD模型生成技术,通过建立关键点实现了拓扑优化结果CAD模型的自动生成;在此基础上,研究了形状优化设计和尺寸优化设计与参数化设计技术相结合的优化方法;通过优化结果数据提取,快速进行优化结果模型的生成,实现了机械结构的快速参数化三级优化,避免了现有结构优化设计过程中手动进行模型修改更新操作复杂、浪费时间的弊端;最后,以某型号汽车转向器支架为例,验证了该方法的有效性。     

Tribological properties of Mn-Zn-Fe magnetic fluids under magnetic field

A controllable and variable magnetic field was got by improving the oil cup of a MS-800 four-ball tester. By this improved four-ball tester, the tribological properties of Mn_0.78Zn_0.22Fe₂O₄ magnetic fluid in the magnetic field were tested. The worn surfaces of the steel balls lubricated with 6 wt% Mn_0.78Zn_0.22Fe₂O₄ magnetic fluid under different magnetic fields were observed by using a scanning electron microscope (SEM), while the elemental compositions of the wear scars were analyzed by means of energy dispersive spectrometry (EDS). It was found that the Mn_0.78Zn_0.22Fe₂O₄ nanoparticles had a diameter about 20 nm. Under magnetic field, the 46^# turbine oil containing 6 wt% Mn_0.78Zn_0.22Fe₂O₄ nanoparticles showed much better friction-reducing and anti-wear abilities compared with lubrication without magnetic field. The worn surface, lubricated by 6 wt% Mn_0.78Zn_0.22Fe₂O₄ magnetic fluid lubricated under the effect of magnetic field, is smooth and the plowing is almost disappeared. Moreover, it is found that 22 mT magnetic induction is the optimum magnetic induction. Form theory study we found that under the effect of magnetic field, the bearing capacity increasing with the increasing of magnetic induction. When the eccentricity is small, the side leakage is highly decreased.     

A web-based advisory system for process and material selection in concurrent product design for a manufacturing environment

This paper reports the work of selecting suitable manufacturing processes and materials in concurrent design for manufacturing environment. In the paper, a fuzzy knowledge-based decision support method is proposed for multi-criteria decision-making in evaluating and selecting possible manufacturing process/material combinations in terms of the total production cost. Based on the proposed method, a prototype Web-based knowledge-intensive manufacturing consulting service system (WebMCSS) with the client-knowledge server architecture is developed to help designers/users find good processes and materials while still at the conceptual level of design. The system, as one of the important parts of an advanced design for manufacturing tool, is a concept level process and material selection tool that can be used as both a standalone application and a Java applet freely available via the Web. Interlinked with Web pages of tutorials, and reference pages explaining the facets, fabrication processes and material choices, the system performs reasoning and calculations using the process capability and material property data from the remote Web-based database and knowledge base that can be maintained and updated via the Internet. The use of the system is illustrated with an example.     

退火温度对二氧化钛薄膜的性能影响

为了获得性能优良的二氧化钛薄膜,采用电子束蒸发沉积方法制备二氧化钛薄膜,并分别在300、600、900℃空气中对样品进行退火处理以改善所制备二氧化钛薄膜的性能。分别采用X射线衍射(XRD)、原子力显微镜(AFM)以及分光光度计研究了退火温度对二氧化钛薄膜结构和光学性能的影响。结果表明,退火处理可以使二氧化钛薄膜由非晶态薄膜转换为金红石型薄膜,且金红石晶型成分随退火温度的加大而增大,同时退火处理可以改善二氧化钛薄膜在300~1 200nm光谱范围的总吸光率以及增大二氧化钛薄膜的应用范围。     

Concurrent process tolerance design based on minimum product manufacturing cost and quality loss

In a concurrent design environment, a robust optimum method is presented to directly determine the process tolerances from multiple correlated critical tolerances in an assembly. With given distributions of multiple critical assembly dimensions, the Taguchi quadric quality loss function is first derived. The quality loss is then expressed as the function of pertinent process tolerances. A nonlinear optimal model is established to minimize the summation of manufacturing costs and product quality loss. An example illustrates the proposed model and the solution method .     

Analysis of robust stability and performance for two-degree of freedom control structure with dynamic controller

In the two-degree of freedom control, the performance of good command following and disturbance rejection are considered separately. Qualitatively, good performance is equivalent to minimizing the energy of the error for any inputs. In this work, usingH _∞-formulation in the frequency domain, robust stability and robust performance specifications have been analyzed for the two-degree of freedom control structure with a dynamic controller. When the two-degree of freedom system having a feed-forward loop is controlled by a dynamic controller, two different performance weight functions are imposed and the robust performance specification is proposed in terms of the return ratio and feed-forward loop. The design algorithm in the frequency domain is illustrated for the simplified retail model of Industrial Dynamics to compare three kinds of control laws, which are the output feedback control scheme and two additional dynamic control ones. Numerical simulation results show that the dynamic control laws provide a larger robust stability margin than the output feeback control one and has good performance robustness for disturbance rejection at low frequencies.     

High-temperature tribological properties of spark-plasma-sintered Al2O3 composites containing barite-type structure sulfates

Al₂O₃–50BaSO₄–20Ag, Al₂O₃–50BaSO₄–10SiO₂, Al₂O₃–50(mass%)SrSO₄, Al₂O₃–50PbSO₄–5SiO₂, Al₂O₃–50BaSO₄ and Al₂O₃–50BaCrO₄ composites (mass%) were prepared by spark plasma sintering and their microstructure and high-temperature tribological properties were evaluated. Al₂O₃–50BaSO₄–20Ag composites (mass%) showed the lowest friction coefficients at the temperature ranging from 473 to 1073 K. Thin Ag film was observed on the wear tracks of the composites above 473 K. In addition, the friction coefficients of Al₂O₃ composites containing SrSO₄ and PbSO₄ were as low as those of Al₂O₃–BaSO₄ and Al₂O₃–BaCrO₄ composites at the temperatures up to 1073 K. The thin films formed on the wear tracks of the Al₂O₃–SrSO₄ composites were composed of Al₂O₃ and SrSO₄ phases, while the films formed on the wear tracks of the Al₂O₃–PbSO₄–SiO₂ composites consisted of Al₂O₃, PbSO₄ and SiO₂ phases.     

几种新型多学科设计优化算法及比较

归纳和评述了二级集成系统综合法、分级目标传递法和子空间自主式优化方法3类基于系统分解的新算法及其改进算法,阐述了3种算法的基本思想、结构体系及其特点,讨论了它们对优化对象的适应性,并从分解标准、级数、收敛性和代理模型等方面对它们进行了比较.     

Complete modeling and parameter optimization for virtual ring rolling

Virtual manufacturing, usually consisting of complete modeling and optimization, of a manufacturing process has recently become one of the research trends in the area of process designing and selection. With the aim to realize complete modeling of a ring rolling process, a complex actuation mechanism model of a heavy radial-axial ring rolling machine has been established in this study. Moreover, a self-modified computer program for controlling the real-time movements of two guide rollers and two conical rollers in a ring rolling process has been developed. An optimization objective function has been proposed for saving the rolling time, in which the slip rate is regarded as the state variable. With this function, the virtual ring rolling process for producing a titanium alloy ring with a rectangular section has been successfully conducted using the finite element method. The simulation results are in good agreement with the experimental findings. Thus, the feasibility of the proposed method has been demonstrated. The computational result also reveals that the proposed optimization method can reduce the rolling time by about 28%.     

制造系统通用作业计划与蚁群算法优化

分析了基本作业方式的“通用-特例”关系,提出了全面研究上述基本作业方式的通用作业计划的概念,建立了通用作业计划非连接图模型及基于蚁群算法的优化方法。算例研究假定一制造系统包含开放作业、异顺序作业、混杂流水作业三种作业方式,将其按照通用作业计划方式采用蚁群算法进行优化,所得的近优加工流程时间显著优于采用穷举法对三种作业方式分别优化所得的最优解。     

A general dynamics and control model of a class of multi-DOF manipulators for active vibration control

A general dynamic model of a class of parallel platforms for vibration control applications based on Kane's method is presented. A general parallel platform is composed of a moving platform, a base platform, and i limbs with identical kinematic structure. Each limb connects the mobile platform to the base platform by j + 1 hinges and j struts, where the prismatic actuator is fixed at one of the struts. The hinges can be replaced by any other kind of conventional hinges or flexure hinges. The control system architecture based on mixed H₂/H_∞ synthesis method is introduced for a class of parallel platforms as a multiple-input/multiple-output (MIMO) problem for the purpose of active vibration isolation. A case study is illustrated and the theoretical analysis is validated at last.     

Tribological Properties of Polymer Composites Containing Barite (BaSO4) or Potassium Titanate (K2O · 6(TiO2))

Tribological properties of particulate barite (BaSO₄) and potassium titanate (K₂O·6(TiO₂)) whiskers, the two major ingredients currently used for commercial brake friction materials, were investigated. A novolac resin was used as a binder for test specimens and a block-on-disk tribometer was used to assess friction characteristics of the two ingredients. Experimental results showed that the BaSO₄-filled composite produced large frictional oscillations and created severe damage on the gray iron counter surface, while the composite filled with the same amount of K₂O·6(TiO₂) whiskers showed smooth sliding without large friction force fluctuation. The cause of the different frictional behavior was investigated by considering stick-slip and mechanical properties of the composites, which was largely based on the morphology of the two ingredients and their role in reinforcing the composite. The results from this comparative study suggest that the friction characteristics of commercial friction materials can be strongly affected by the two ingredients, which have been considered as minor constituents for brake performance.