Review of main manufacturing processes of complex hollow turbine blades

In view of their development at present, the advanced manufacturing processes of hollow turbine blades are reviewed thoroughly. There are several kinds of manufacturing technologies, including investment casting, laser metal direct forming and integrated manufacturing of ceramic cores shell, for hollow turbine blades, and their advantages and disadvantages are contrastively analysed. The development direction and the problems to be solved are put forward for manufacturing the hollow turbine blades to fulfil the increasing requirements of the high performance engine and energy conservation in the future.     

Real option approach to evaluate cores for remanufacturing in service markets

Acquisition of cores is important for the success of remanufacturing business, but evaluating the value of cores is difficult due to many uncertain issues in the remanufacturing system. In this paper, we examine the value of cores using the real option valuation (ROV) approach, which well captures the production flexibility and represents different operations options in remanufacturing. First, in a system where the demand of remanufactured products is low, we focus on the uncertainty of price. We compare the cases where disposing cores occurs only at the expiration time and before that. The model also identifies under which circumstances disposing core early brings in more benefit. Furthermore, we study a remanufacturing system where demand and return are both uncertain. In this case, a spread option is used for evaluating the marginal value of obtaining additional cores. This approach also brings the advantage of linking the correlation between demand and return, which in fact is often exhibited in remanufacturing. The numerical experiments indicate that this correlation has an impact on collecting policies. This study illustrates the possibility of using ROV for core pricing modelling, and the study results also provide some managerial insights in managing returned cores.     

软磁合金粉末特性对金属软磁粉芯的影响

软磁合金粉末作为制备金属软磁粉芯的原材料,是决定磁粉芯性能的关键因素之一。本文综述了软磁合金粉末的合金成分、形貌、粒度以及粉末纯度对软磁粉芯性能的影响。分析结果表明,铁硅铝磁粉芯具有最佳性价比,采用气雾化法生产的球形粉末具有最佳的软磁特性,软磁粉末越细,纯度越高,所制备的磁粉芯软磁性能越好。     

磁粉芯的研究进展

磁粉芯具有良好的软磁性能和频率特性,广泛应用于电感元件和变压器.分类介绍了纯铁粉芯、坡莫合金粉芯、铁硅铅粉芯、非晶和纳米晶粉芯的成分组成及其磁性能,重点阐述了粉末制备、绝缘包覆、压制成型和热处理等工艺参数对磁粉芯软磁性能的影响,最后指出新制备工艺的开发和相关理论模型的构建将成为未来磁粉芯研究的热点.     

The role of yttrium modifying A357 alloy with sand casting

The microstructure of A357 alloy modified by yttrium (Y) and its modification mechanism was investigated. The results show that under a sand casting condition, there was small or even no solution strengthening effect of Y on the A357 alloy. Y did not change the morphology of eutectic silicon but made it shorter, and Y increased the nucleation cores during its nucleation processes rather than promoting the formation of twinning during the growth processes. The solidification mode of many eutectic silicon phases changed from nucleating on the dendrites to heterogeneous nucleation of eutectic grains in the interdendritic liquid. The number and area of eutectic silicon clusters increased with increasing Y. A bright Al₂Si₂Y phase appeared even though Y was very low.     

飞机导流器零件的精密铸造

为解决导流器这一飞机发动机气道关键零件的成形问题并保证冶金质量，对熔模陶瓷壳型真空吸铸加压凝固方法的应用做了试验研究，结果表明。该技术可以显著提高金属液的充型能力和补缩能力，制出的导流器件符合技术要求，并已装机使用。     

The Collapse Response of Sandwich Beams with Aluminium Face Sheets and a Metal Foam Core

Plastic collapse modes of simply supported and clamped sandwich beams have been investigated experimentally and theoretically, for aluminium face sheets and Alporas foam core. The effect of clamped boundary conditions is to induce axial stretching after the initial yield mechanism. Hence, face sheet ductility dictates the level of energy absorption of the beam. Numerical and analytical predictions are validated by the available experimental evidence.     

Grain Size Effects on the Mechanical Behavior of Open‐cell Nickel Foams

The dependence of the mechanical behavior of nickel foams upon their grain size was studied. First, the grain coarsening phenomenon which occurs during the processing of foams was analyzed. A metallurgical characterization of the grain growth during heat treatment was performed. The grain size effects on the mechanical properties was then studied, namely, via the Hall‐Petch law. The foam walls being very thin, roughly 10 μm in thickness, grain growth and mechanical behavior might be different compared with conventional materials. The present results obtained with foams were compared with literature data on bulk pure nickel and with nickel foils of 10 and 50 μm in thickness which are good candidates for the modeling of the cell walls. The EBSD technique allowed observing the absence of preferred crystallographic orientations for both foams and foils. A mechanical model in the spirit of that by Gibson and Ashby was finally presented incorporating the grain size effect on yield strength and hardening modulus. This model provided a good estimation of the experimental data.     

真空铸造技术的研究现状

通过分析真空铸造在造型、充型、凝固过程中产生的现象，讨论了真空密封造型、实型真空铸造、真空吸铸、真空低压铸造、真空差压铸造等技术的现状，针对国内外发展现状提出今后真空熔模吸铸的研究与发展的方向。     

Vertical glaciology: The second discovery of the third dimension in climate research

The history of climate research in the 20th century has been characterised by a crucial shift from a geography-oriented, two-dimensional approach towards a physics-based, three-dimensional concept of climate. In the 1930s, the introduction of new technology, such as radiosondes, enabled climatologists to investigate the high atmosphere, which had previously been out of reach. This “conquest of the third dimension” challenged the surface-oriented, geographical notion of climate patterns and opened up climatology to a three-dimensional approach, which deeply changed the character of climate research. Two decades later, by drilling deep into polar glaciers and using the downward vertical dimension as an archive of the earth's history, ice core scientists began to reconstruct past climates layer by layer. The data retrieved in deep glacial layers contributed crucially to a temporal expansion of climate history far beyond human timescales. However, the inaccessibility of glaciers and the practical challenges of bringing fragile fragments of ice into transnational networks of scientific exchange meant that this vertical extension of climate knowledge production proceeded through a range of new scientific practices, and was shaped by new forms of international collaboration. Furthermore, this vertical approach to glaciers also asked for a new understanding of glacier volume. Drawing on archival and printed sources, I argue that ice core research represented a second discovery of the third dimension, this time downwards into the depth of the earth's surface, but again with decisive consequences for the research practice, for collaboration politics, and for understandings of climate, spatially as well as temporally.     

反向凝固连铸薄带技术及其若干基本问题探讨

简述了反向凝固薄带连铸技术的工艺原理,阐述了反向凝固技术的特点、竞争力,介绍了其研究现状,论了反向凝固技术所涉及的若干基本问题。     

Impact of carbon fibre/epoxy corrugated cores

The dynamic compressive response of corrugated carbon-fibre reinforced epoxy sandwich cores has been investigated using a Kolsky-bar set-up. Compression at quasi-static rates up to v₀ = 200 ms⁻¹ have been tested on three different slenderness ratios of strut. High speed photography was used to capture the failure mechanisms and relate these to the measured axial compressive stress. Experiments show significant strength enhancement as the loading rate increases. Although material rate sensitivity accounts for some of this, it has been shown that the majority of the strength enhancement is due to inertial stabilisation of the core members. Inertial strength enhancement rises non-linearly with impact velocity. The largest gains are associated with a shift to buckle modes composed of 2–3 half sine waves. The loading rates tested within this study are similar to those that are expected when a sandwich core is compressed due to a blast event.     

低损耗铁粉芯的制备与磁性研究

通过三层包覆法制备了铁粉芯,用XRD和BH分析仪对其结构和磁性能进行了分析。研究发现,在1kHz频率下初始磁导率随温度变化,样品具有良好的温度稳定性;在f=1kHz、Bm=1T的损耗为115.6W/cm3,样品具有低损耗特征。     

一种大型真空精密铸造炉结构布局的研究

本文首先分析了真空精密铸造炉在国内外的主流形式,并分析这些形式面对大型精密铸造时的不足.然后针对这些不足提出一种用于大型真空精密铸造炉结构布局及其衍生炉型.最后探讨了这种新的结构布局的发展机遇与前景.     

Transverse shear modulus and strength of honeycomb cores

The transverse shear mechanical behavior and failure mechanism of aluminum alloy honeycomb cores are investigated by the single block shear test in this paper. The transverse shear deformation process of honeycomb cores may be approximately categorized into four stages, namely elastic deformation, plastic deformation, fracture of cell walls and debonding of honeycomb cores/facesheets. The elastic deformation of unit cell under transverse shear displacement is also investigated by the finite element method, and the result shows that the bending deformation of the cell walls is similar to that of the cantilever beam. In order to precisely predict the equivalent transverse shear modulus and strength, not only shear deformation but also bending deformation of cell walls should be considered. Therefore, in the present paper, the equivalent transverse shear modulus and strength are predicted by application of the cantilever beam theory and thin plate shear buckling theory in conjunction with simplifying assumption as to the displacement in the cores. It is concluded that the contribution of bending deformation of cell walls to equivalent transverse shear modulus and strength is obvious with the decreasing height of cell walls.     

A parametric study on compressive characteristics of Wire-woven bulk Kagome truss cores

Compressive behaviors of the Wire-woven bulk Kagome (WBK) cores fabricated of stainless wires are experimentally investigated. Effects of geometrical parameters such as the wire diameter, strut length and number of layers on the compressive behaviors are studied. Also, behaviors of two different types of the specimen configurations, namely, pointed faced and flat faced specimens are compared to each other and analyzed. As the number of layers increases, the strength of the specimens slowly decreases. The compressive strength of WBK dominantly depends on the slenderness ratio. Difference in the specimen configurations results in the significant difference of the stress–strain responses for the specimens with slenderness ratio higher than a certain value. The compressive strength and energy absorption capability of WBK are as good as those of the regular truss type cellular metals, when the relative density is sufficiently high.     

点阵材料夹芯简支梁在冲击载荷下的动力响应

首先给出了两端可移点阵材料夹芯简支梁受到均布冲击载荷时的刚塑性动力响应分析,然后将理论预测的夹芯梁中点的最大挠度和结构响应时间与有限元结果进行了比较,理论预测结果与有限元计算结果一致性较好。通过与质量和材料相同的单层实心梁进行对比分析,证实了点阵材料夹芯简支梁具有很好的抗冲击性能。通过对四棱锥夹芯简支梁进行拓扑构型设计,发现两端可移夹芯简支梁的最大挠度和结构响应时间对芯层的相对密度和相对厚度、面板与杆元的夹角十分敏感。随着夹芯梁所承受的单位面积冲量增大 , 夹芯梁中点的挠度增大。通过对由应变率敏感的304不锈钢制成的四棱锥桁架夹芯梁进行精细有限元分析,发现当考虑应变率效应时,梁的最大挠度小于不考虑应变率时的最大挠度。     

细晶铸造K 403合金热处理工艺的研究

研究了固溶处理温度对细晶铸造K403合金的组织和性能的影响,最科确定热等静压后合适的热处理制度为：1180^ 10℃/4h 980℃/6h     

中断正火热处理工艺的研究与应用

对铸钢中断正火热处理工艺进行了研究。结果表明:铸钢件利用铸造余热进行中断正火法热处理后,其基体组织是下贝氏体+马氏体+少量残余奥氏体。因而使铸钢件的强度和韧性获得最佳匹配,并使铸钢件的耐磨性也相应得到提高。     

精铸技术在模具制造中的应用

本文叙述了熔模精铸模具、陶瓷型精铸模具、石膏型精铸模具和加压精铸模具的应用情况，由于精铸模具比机加工模具缩短了生产周期．降低了制造成本．故有很好的发展前景。文章还对陶瓷型精铸模具技术提出了六点改进意见。