水轮机上冠的铸造

叙述了水轮机上冠不同以往的铸造方法.新铸造方案中采用了立撞立浇、集中补缩、分层浇注等新工艺、新方法,从而使生产出的产品完全达到了用户的质量要求.     

水电站转轮上冠的铸造

通过从材质和结构方面对不锈钢铸件上冠的铸造工艺性能分析,制定出针对性的铸造工艺方案,从而顺利完成上冠的铸造生产,为以后生产同类不锈钢铸件做了较为全面的技术储备。     

大型不锈钢上冠的研制

介绍ZG0Cr16Ni5Mo新材料科研成果及国内首件大吨位不锈钢上冠工艺技术文件的制定.     

大型水轮机上冠铸造工艺设计与优化

本文在对上冠的结构及技术要求进行深入分析后,运用有关金属凝固中的顺序凝固原则和铸造工艺设计的大孔出流理论的知识,设计了出了上冠铸件的初步铸造工艺方案,然后使用铸造模拟仿真软件Flow-3D对所设计的初步铸造工艺的金属液体的充型和凝固的过程进行了模拟仿真,得到了仿真结果,通过对模拟结果的分析发现了初步铸造工艺在充型以及凝固过程中可能存在的一些不足,然后针对这些问题提出了工艺改进措施,改进之后再进行仿真,最后得出了较理想的工艺。     

水轮机泵轮上冠及下环铸造工艺研究

本文重点介绍通过选择有效的工艺方案和合理的工艺参数，成功生产出尺寸精度高、内部质量好的不锈钢上冠、下环产品。     

Plastic limit analyses of circular plates with respect to unified yield criterion

Plastic limit analysis of a circular plate under uniform transverse loading is presented in terms of an unified yield criterion (UYC). Exact and unified solutions of load-carrying capacities, moment fields and velocity fields for simply supported circular plate, clamped circular plate and annular plate in plastic limit state are derived. Moment fields of the three typical circular plates correspond to different distribution fields on the yield curves. Maximum and minimum plastic limit solutions are deduced for the three types of circular plates by selecting the weighted coefficients with upper and lower bound values in the unified yield criterion. Moment fields and velocity fields with respect to the three special criteria, namely the Tresca criterion, the Mises criterion (close-form solution) and the twin shear stress criterion are illustrated and compared. The paper presents an effective analytical method to compute the exact plastic limit solution for circular plates in terms of a piecewise linear yield criterion.     

消失模铸造工艺在密集小孔平板类铸件中的应用

密集小孔平板铸件的普通砂型铸造工艺十分复杂,而且合格率低,铸件难以清理。介绍采用消失模铸造工艺生产带有密集小孔平板类铸件的工艺方法。实践表明,该法具有独特优越性,生产出的孔板变形小、表面光洁;孔的内壁光滑、棱角清晰。     

Dynamic axial crushing of short to long circular aluminium tubes with agglomerate cork filler

Cork is a complex natural cellular material with quite unknown or not well understood properties. It is available in the natural and in the agglomerate form and it is an ecological and very durable material. That is why it is used today as thermal and acoustic insulator, as a seal and as an energy-absorbing medium in flooring, shoes and packaging, among others. However, the application of agglomerate cork as filler inside structural thin-walled sections, in order to increase the energy absorption, has not been much explored. Dynamic experimental tests were carried out on empty and micro-agglomerate cork-filled tubes with 22 and 50 mm in internal diameter (D) and length (L), respectively, and numerical simulations were performed with the finite element method software LS-DYNA^TM, showing good agreement in terms of load–displacement curves and deformation patterns. Having validated the numerical model with experiments, the finite element model was used to undertake a systematic study of circular tubular structures impacted at 10 m/s. The load-deformation characteristics, energy-absorption response and collapse mode transitions of empty and cork-filled aluminium tubes with varying diameters and thicknesses (t), lengths of 25, 300 and 350 mm, but with constant slenderness ratios D/t and D/L were thus studied. Relevant comparisons were raised, showing that the slenderness ratios are very important parameters that globally govern the percentage increase in energy absorbed by tubular structures after cork-filling during an impact loading.     

Tribological behaviour of stainless steel with respect to that of DLC in terms of energetic aspects

Abstract

The tribological behaviour of stainless steel (SUS 440C) relative to that of diamond-like carbon (DLC) was investigated in terms of tribometer input energy. The DLC was prepared on tungsten carbide (WC) substrates using radio frequency plasma chemical vapour deposition with benzene (C₆H₆) as a gas source. The stainless steel ball, as the counterpart, was tribotested. The input energy was calculated using the applied load, friction coefficient and sliding distance obtained from each tribotest. The wear loss of the ball increased as the sliding distance increased, whereas wear loss of the DLC was not directly observed. During evaluation of the input energy, the wear rate of the stainless steel ball decreased as the input energy increased. We propose a method for evaluating tribological properties using the input energy and discuss the wear behaviour of the stainless steel based on the input energy.     

iTNC530数控系统中使用标准循环与变量编程实现矩形椭圆的漏斗型加工

利用iTNC530数控系统提供的标准固定循环与变量计算功能实现漏斗形状的自由加工.灵活的结合两种编程方式,使加工程序段大量减少,并可自由控制加工工艺,极大的提高了加工效率.     

薄壁不锈钢零件冷风加工探讨

针对不锈钢制做的薄壁测试模型的难切削性,采用了冷风切削加工技术。实验结果表明,这种方法能够加工出达到测试模型要求的零件。冷风切削不锈钢的实验成功,为航空实验水平上台阶,创造了条件。     

Parametric combination resonance instability characteristics of laminated composite curved panels with circular cutout subjected to non-uniform loading with damping

The dynamic instability of laminated composite doubly curved panels with centrally located circular cutout, subjected to non-uniform compressive in-plane harmonic edge loading is investigated. The present work deals with the problem of the occurrence of combination resonances in contrast to simple resonances in parametrically excited antisymmetric angle-ply and symmetric cross-ply laminated composite doubly curved panels with central circular cutout. The method of multiple scales is used to obtain analytical expressions for the simple and combination resonance instability regions. It is shown that other cases of the combination resonance can be of major importance and yield a significantly enlarged instability region in comparison to the principal instability region. The effects of non-uniform edge loading, centrally located circular cutout, damping, number of layers, orthotropy, the static load factor and the width-to-thickness ratio on dynamic instability behavior of simply supported laminated composite doubly curved panels are studied. The results show that under localized edge loading, combination resonance instability zones are as important as simple resonance instability zones. The effects of damping show that there is a finite critical value of the dynamic load factor for each instability region below which doubly curved panels cannot become dynamically unstable. A central circular cutout has the destabilizing effect on the dynamic stability behavior of laminated composite doubly curved panels subjected to non-uniform edge loading. This example of simultaneous excitation of two modes, each oscillating steadily as its own natural frequency, may be of considerable interest in vibration testing of actual structures.     

高水头水轮机导叶漏水的处理

在高水头电站的导水机构改造中,通过对导水机构和转轮空蚀情况的分析和对比,同时运用空蚀理论,研究了空蚀产生的原因、危害,进而得出了处理方法。并分析了O型密封圈在导叶轴颈密封中的使用,获取了一些处理导叶漏水的经验。     

A predictive hybrid force modeling in turning: application to stainless steel dry machining with a coated groove tool

The International Journal of Advanced Manufacturing Technology - This paper presents an hybrid numerical/analytical modeling for estimation of cutting forces in machining process. The approach...