小直径磨棒磨削加工TiC颗粒增强钢基复合材料GT35

为探究TiC颗粒增强钢基复合材料GT35合理的加工参数和冷却润滑条件,研究其对切削力、表面质量及刀具磨损的影响规律,采用小直径磨棒以侧面磨削方式开展试验。结果表明：干磨削会引起磨棒烧伤,极压磨削油的润滑效果优于水基合成磨削液的;磨棒在极压磨削油润滑下,磨削工件12 min后进入稳定磨损状态,其主要磨损形式为磨粒破碎、磨粒磨耗和磨粒脱落;主轴转速对切削力的影响大于进给速度的,且转速越高,切削力越小;工件表面粗糙度主要与磨棒磨粒出露高度的平整度有关,受加工参数的影响较小。用小直径磨棒磨削加工GT35材料时,应选择极压磨削油润滑,高主轴转速、中速进给的加工方式,以获得良好的刀具寿命、工件加工表面质量及适当的加工效率。     

The location of atomic hydrogen in NiTi alloy: A first principles study

A first principles density functional theory study to investigate the H defect in NiTi alloy is presented. We have determined the interstitial H atom position in bulk B2 phase NiTi alloy. H positions on both the Ti and Ni terminated NiTi surfaces are calculated. Surface adsorptions of H atom on Ni/Ti terminated surfaces are calculated for a low surface coverage of 1.96 × 10¹⁴ cm^?2. We have also calculated the penetration barrier energy for an H atom from the surface site to the bulk lattice site.     

Analysis on Pseudo Excitation of Random Vibration for Structure of Time Flight Counter

Traditional computing method is inefficient for getting key dynamical parameters of complicated structure.Pseudo Excitation Method(PEM)is an effective method for calculation of random vibration.Due to complicated and coupling random vibration in rocket or shuttle launching,the new staging white noise mathematical model is deduced according to the practical launch environment.This deduced model is applied for PEM to calculate the specific structure of Time of Flight Counter(ToFC).The responses of power spectral density and the relevant dynamic characteristic parameters of ToFC are obtained in terms of the flight acceptance test level.Considering stiffness of fixture structure,the random vibration experiments are conducted in three directions to compare with the revised PEM.The experimental results show the structure can bear the random vibration caused by launch without any damage and key dynamical parameters of ToFC are obtained.The revised PEM is similar with random vibration experiment in dynamical parameters and responses are proved by comparative results.The maximum error is within 9%.The reasons of errors are analyzed to improve reliability of calculation.This research provides an effective method for solutions of computing dynamical characteristic parameters of complicated structure in the process of rocket or shuttle launching.     

A novel robot co-worker system for paint factories without the need of existing robotic infrastructure

This paper presents a human–robot co-working system to be applied to industrial tasks such as the production line of a paint factory. The aim is to optimize the picking task with respect to manual operation in a paint factory. The use of an agile autonomous robot co-worker reduces the time in the picking process of materials, and the reduction of the exposure time to raw materials of the worker improves the human safety. Moreover, the process supervision is also improved thanks to a better traceability of the whole process. The whole system consists of a manufacturing process management system, an autonomous navigation system, and a people detection and tracking system. The localization module does not require the installation of reflectors or visual markers for robot operation, significantly simplifying the system deployment in a factory. The robot is able to respond to changing environmental conditions such as people, moving forklifts or unmapped static obstacles like pallets or boxes. The system is not tied to specific manufacturing orders. It is fully integrated with the manufacturing process management system and it can process all possible orders as long as their components are placed into the warehouse. Real experiments to validate the system have been performed in a paint factory by a real holonomic platform and a worker. The results are promising from the evaluation of performance indicators such as exposure time of the worker to raw materials, automation of the process, robust and safe navigation, and the assessment of the end-user.     

端部双触点型压电驱动器

设计并制作了一种基于矩形块状压电陶瓷一阶纵振和二阶弯振模态耦合的直线型压电驱动器。该压电驱动器在矩形块状压电陶瓷的2个端部均布置1个氧化铝陶瓷触点,2个触点交替工作,提高了矩形块状压电陶瓷振子的振动利用率。采用有限元与实验结合的方法设计并优化了驱动器的结构尺寸。并通过实验发现,在电压峰-峰值600V下,该驱动器的最大空载速度为250mm/s,最大输出力为16N。最后,对驱动器中板簧发热问题进行了讨论和分析得出,板簧在设计时应尽可能远离驱动器的工作频率,否则会使板簧共振发热,影响驱动器的寿命,严重时将损坏驱动器内部结构。     

Ontology-based information modeling method for digital twin creation of as-fabricated machining parts

The Digital Twin concept, as the cutting edge of digital manufacturing solution for modern industries, plays a significant role in the Industry 4.0 era. One key enabling technology for developing a DT is the information modeling of physical products, so as to combine the physical world with the cyberspace more extensively and closely. Therefore, the modeling approach to managing as-fabricated data of physical products, which faithfully reflects the product's physical status, emerges to be pivotal. This paper addresses the problem of modeling as-fabricated parts in the machining process, which is difficult to accomplish by relevant methods, and hinders the long-term data archiving and reuse of process data. Furthermore, to fill the gap, an ontology-based information modeling method of as-fabricated parts is proposed as the recommendation to create DTs for as-fabricated parts. It provides a simple and standardized process for companies to create DTs of as-fabricated parts by specifying the information classification, the contents to be modeled and the modeling method. To validate the effectiveness of the proposed approach, a case study is undertaken in an aviation manufacturing plant at last. The result shows that the proposed information modeling methodology is readily to DT creation of as-fabricated parts.     

Friction and wear behavior of laser composite surfaced aluminium with silicon carbide

The present study concerns the wear behavior of laser composite surfaced Al with SiC and Al + SiC particulates. A thin layer of SiC and Al + SiC (at a ratio of 1:1 and dispersed in alcohol) were pre-deposited (thickness of 100 μm) on an Al substrate and laser irradiated using a high power continuous wave (CW) CO₂ laser. Irradiation leads to melting of the Al substrate with a part of the pre-deposited SiC layer, intermixing and followed by rapid solidification to form the composite layer on the surface. Following laser irradiation, a detailed characterization of the composite layer was undertaken in terms of microstructure, composition and phases. Mechanical properties like microhardness and wear resistance were evaluated in detail. The microstructure of the composite layer consists of a dispersion of partially melted SiC particles in grain refined Al matrix. Part of the SiC particles are dissociated into silicon and carbon leading to formation of the Al₄C₃ phase and free Si redistributed in the Al matrix. The volume fraction of SiC is maximum at the surface and decreases with depth. The microhardness of the surface improves by two to three times as compared to that of the as-received Al. A significant improvement in wear resistance in the composite surfaced Al is observed as compared to the as-received Al. The mechanism of wear for as-received vis-à-vis laser composite surfaced Al has been proposed.     

Experimental Investigation on the Compatibility of Nanoparticles with Vegetable Oils for Nanofluid Minimum Quantity Lubrication Machining

Several health and environmental related issues caused by the application of traditional cutting fluids in machining can be solved by implementing eco-friendly technologies such as minimum quantity lubrication (MQL). Moreover, nanofluid MQL has been proposed to enhance the cooling/lubricating properties of pure MQL and displays significantly good results for machinability. However, the mechanism on compatibility of nanoparticles with cutting fluids has not been explored. In this study, nanoparticles with different hardness and vegetable oils with different viscosity were selected for nanofluids preparation. The end milling experiments were carried out on 7050 material by applying MQL with particularly prepared nanofluids. The cutting force and surface roughness were measured corresponding to the machining performance. The compatibility of hardness of nanoparticles with viscosity of base fluids has been evaluated, and the mechanism has been analyzed by new-designed tribology tests. Results show that canola oil-based diamond nanofluids MQL exhibit the lowest cutting force and natural77 oil-based diamond nanofluids perform the lowest surface roughness with reduction of 10.71 and 14.92%, respectively, compared to dry machining condition. The research is novel and contributes to the machining of such materials at the industry level.     

Analysis on the Wear Performances of Cemented Carbide Tools Containing Ti in the Coatings When Machining Ti-6Al-4V Alloys

含钛涂层硬质合金刀具在加工Ti-6Al-4V合金时的磨损性能分析

孙剑飞1,2,3,杜大喜4,丁梓轩1,王凯1,白大山1,陈五一1,2

（1.北京航空航天大学 机械工程及其自动化学院,北京100191;

2.先进航空发动机协同创新中心,北京100191,中国;

3.北京市高效绿色数控加工工艺与装备工程技术研究中心,北京100191,中国;

4.北京航天石化技术装备工程有限公司,北京100166,中国）

摘要：由于钛元素的高亲和力,在加工钛合金时含钛涂层的硬质合金刀具似乎不是最佳的选择。然而在实践中,含钛涂层硬质合金刀具仍然广泛应用于钛合金的加工。为了系统的解释实践与理论之间的矛盾,进行了切削实验。使用俄歇电镜扫描切削区域来解析钛合金与硬质合金刀具之间的扩散过程。并通过分子热力学模拟Ti/Co扩散行为对这一过程进行仿真。实验和仿真结果表明,Ti/Co原子的相互扩散是导致扩散磨损的主要原因。溶解-扩散磨损是含钛涂层硬质合金刀具的主要磨损机制之一。此外,采用四种硬质合金刀具和另外两种金属陶瓷刀具以不同的速度切削Ti-6Al-4V合金,进一步验证含钛刀具在基体和图层中的高亲和力。实验结果表明,含钛硬质合金刀具一般不能用于钛合金的切削加工,但在合理的切削条件下,刀具与工件的亲和力较低。

关键词：磨损机理;Ti/Co扩散;分子热力学模拟;含钛硬质合金刀具;Ti-6Al-4V钛合金