Improvement of workpiece quality in face milling of aluminum alloys

The compliance with the quality requirements of components is essential for the functionality of the whole product. With respect to parts with face-milled faces, the surface quality and the shape of the workpiece edges are of great interest. Frequently, these faces take over the function of seal faces where high demands on the surface integrity and burr formation exist. To ensure the workpiece quality that is required, nowadays additional processes for deburring are often necessary. To avoid deburring, the modification of machining processes is a promising approach. In this study, the influence of process cooling on workpiece quality is investigated. Using this approach, two effects are expected. The cooling is used to minimize a reduction of flow stress generated from the process heat, which than leads to a lower formability. The second effect relates to the kinetic energy of the snow blast for deburring by deformation and breakage of the burrs. Using a process cooling with carbon dioxide, the surface quality is enhanced and the burr formation is minimized.     

Com4~立达纱——纱线之精选

2011年9月,在巴塞罗那国际纺织机械展览会(ITMA 2011)上,来自瑞士的Rieter(立达)公司首次同时展出了其拥有的4种纺纱系统:环锭纺、紧密纺、转杯纺和喷气纺,从而成为全球能够提供所有4种纺纱技术的独家供应商。最近,立达将其拥有的纱线品牌Com4从高品质紧密纱延伸至了所有4种纱线,包括Com4ring环锭纱、Com4compact紧密纱、Com4rotor转杯纱和Com4jet喷气纱。这4种纺纱技术有着不同的工艺特点和自身优势,可生产不同结构、性能和应用领域的纱线。如何选择适合的纺纱技术是纱线制造商投资决策时面临的难题。本刊将在本期和2013年第8、10和12期刊发立达公司Iris Biermann女士撰写的一组文章,来介绍这4种纱线不同的特点和性能以及4种纺纱技术的实际应用及差异,评估市场对4种纱线在不同纺织应用中的需求,为纱线生产商提供全面、客观、有针对性的建议,并告知客户如何直接从Com4立达纱的市场推广活动中获益。     

Autocoro上纺聚酯纱

介绍了Schlafhorst公司设计的、用于Autocoro纺纱机上的新型部件。通过测试，证明纤维上的纺丝助剂对纺纱性能的影响。     

Influence of cutting edge geometry and cutting edge radius on the stability of micromilling processes

The occurrence of tool vibrations in the micromilling process is undesirable because of its negative influence on the quality of microstructures. Due to the small dimensions of the undeformed chip parameter, the influence of the cutting edge on the chip formation and on the regenerative effect seems to be larger than in macrodimensions. Within this paper the results of an experimental investigation with micro end-milling cutters (d = 1 mm) are presented. Additionally, the influences of the cutting edge radius, the corner radius, and the feed per tooth on the tool vibration trajectories, the process forces, and chatter and its causes are discussed.     

Machining of High Strength Light Weight Alloys for Engine Applications

The use of high strength materials with low density in engines and vehicles gains more and more intention for the reduction of weight in moving parts. Currently, γ-titaniumaluminides as well as aluminum-metal-matrix-composites are considered as appropriate materials for this purpose. In spite of their outstanding material properties, problems occur when machining operations are carried out. These problems emerge from the high strength and the abrasive reinforcing particles. This paper presents research on the machining of a γ-TiAl-alloy as well as an Al-MMC-alloy. Investigations of the turning process were focused on ascertaining conditions for an economical and a high-quality machining process.     

Static and Cyclic Crack Growth Behavior of Ultrafine-Grained Al Produced by Different Severe Plastic Deformation Methods

Fracture-mechanics experiments were carried out on ultrafine-grained (UFG) samples of aluminum and two Al alloys to obtain the fracture behavior under static and cyclic loading. The UFG materials investigated show crack resistance behavior under static loading, which was confirmed by ductile fracture surfaces. Under cyclic load, the crack growth rate was described well by the ESACRACK model. The crack propagation results show no influence of the type of the severe plastic deformation method in the Paris region but more effect in the threshold region. This article is based on a presentation made in the symposium entitled “Ultrafine-Grained Materials: from Basics to Application,” which occurred September 25–27, 2006 in Kloster Irsee, Germany.     

Cutting edge rounding: An innovative tool wear criterion in drilling CFRP composite laminates

An evenly and smoothly distributed abrasion wear, observed along the entire cutting edge of an uncoated carbide drill bit in drilling CFRPs, is due to the highly abrasive nature of the carbon fibres. A very few researchers have only quoted this wear mode as being responsible for giving rise to the rounding of the cutting edge, or its bluntness. However, this wear feature has seldom been investigated, unlike the conventional flank wear in practice. This paper offers a new approach in unveiling and introducing the cutting edge rounding (CER) – a latent wear characteristic as a measure of sharpness/bluntness – of uncoated cemented carbide tools during drilling CFRP composite laminates. Four different types of drills (conventional and specialised) were tested to assess the applicability and relevance of this new wear feature. Mechanical loads (drilling thrust and torque) were recorded, and the hole entry and exit delamination were quantified. For the utilised tools, the accruing magnitude of CER was also recorded, in parallel with studying their conventional flank wear. Very appreciable correlations between the CER and the drilling loads, and also the quantitative delamination results are observed. Results reveal that this new wear type develops almost similarly for the selected tools and is practically independent of their respective conventional flank wear patterns. Moreover, a distinct, non-zero magnitude of the CER for a very fresh tool state may provide researchers with some lucid information in further studying the results during wear tests, more emphatically. The CER correlations with quantitative delamination results are noticed quite comparable to those of the conventional flank wear via statistical linear regression analyses.     

A statistical model of fatigue damage evolution in particulate-reinforced metal-matrix-composites

A statistical model of fatigue damage evolution has been developed for particulate-reinforced metal-matrix-composites (MMCs) by taking into considerations both the initial damage distribution and the effect of particulate reinforcement on fatigue damage development. The growth of microscopically fatigue-damaged regions in particulate-reinforced MMCs is considered as a stochastic process, and both the non-equilibrium statistical method and minimum strength principle are used to establish the evolution equation of fatigue damage. The fatigue damage evolution equation developed in the present study characterizes not only the kinetic process of fatigue damage evolution but also sets up the relationship between the mechanism of fatigue damage growth of the microscopically damaged regions and the result of fatigue damage, i.e. degradation of mechanical properties of particulate-reinforced MMCs. A new expression for calculating the cumulative fatigue damage and a new formula for predicting the average fatigue strength of the particulate-reinforced MMCs are derived. Experimental data of 2080Al/SiC_p composites are analysed and compared with results obtained with the present model. It is shown that the experimental results can be described well by the calculations.     

Energy-Absorbing TRIP-Steel/Mg-PSZ Composite Honeycomb Structures Based on Ceramic Extrusion at Room Temperature

Porous materials have received extensive attention for energy absorption in the last few years. In terms of this study, austenitic TRIP-steel/Mg-PSZ-composite honeycomb structures are formed with different mixing proportions due to ceramic extrusion at room temperature. Their specific energy absorption SEA as well as their compression strength have been registered as a function of the compressive strain. X-ray diffractometry (XRD), electron backscatter diffraction (EBSD) as well as electron dispersive X-ray (EDX) analysis support the microstructure characterization. The zirconia addition has mainly contributed as a hard phase in a ductile TRIP steel matrix and has reinforced the composite material up to a compressive strain of about 24%.