共查询到20条相似文献,搜索用时 15 毫秒
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Jie Mao Hai‐Feng Zhang Hua‐Meng Fu Ai‐Min Wang Hong Li Zhuang‐Qi Hu 《Advanced Engineering Materials》2009,11(12):986-991
The glass1‐forming ability of two alloys, Zr64.9Al7.9Ni10.7Cu16.5 and Zr47Cu37.5Ag7.5Al8, prepared by arc‐melting a mixture of Zr, Cu, Al, Ni and Ag elements is studied as a function of casting temperature. Other processing parameters such as the alloy melt mass, and the vacuum and injection pressures during the copper‐mold‐casting process are kept constant so just the influence of the casting temperature is considered. The casting temperature determines the characteristics of the liquid melt and the cooling rate. The glass‐forming ability is discussed in terms of dissipation of pre‐exiting, metastable local‐ordering clusters that act as nucleation sites promoting crystallization, the cooling rate at high casting temperatures, and the presence of oxygen in the alloys, which is increased at high casting temperatures. It is found that the glass‐forming ranges of alloys shrink as the glass‐forming size approaches a critical value. The optimum temperatures are around 1450 K and 1550 K for Zr64.9Al7.9Ni10.7Cu16.5 and Zr47Cu37.5Ag7.5Al8 alloys respectively. The alloys were studied by XRD, TEM, oxygen‐level determination, and DSC. 相似文献
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Shear behaviour of a glass fibre/polypropylene composite is characterized over a wide range of strain rates and forming temperatures using the bias extension test. A temperature- and rate-dependent material model is here introduced to describe the observed behaviour. The model is based on a continuous approach and formulated considering a stress objective derivative based on the warp and weft yarns rotation. The effects of temperature and strain rate on the shear behaviour are analysed via bias extension test simulations. Temperature change in the sheet during forming was measured. This data is used to model cooling during forming. Isothermal and transient forming simulations were performed in order to show the effects of temperature and forming speed on the obtained shear angle distribution. It was found that at low forming speeds the assumption of isothermal forming is not valid anymore since the cooling of the sheet affects the shear behaviour. 相似文献
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Utilization of recycled glass derived from cathode ray tube glass as fine aggregate in cement mortar 总被引:2,自引:0,他引:2
Rapid advances in the electronic industry led to an excessive amount of early disposal of older electronic devices such as computer monitors and old televisions (TV) before the end of their useful life. The management of cathode ray tubes (CRT), which have been a key component in computer monitors and TV sets, has become a major environmental problem worldwide. Therefore, there is a pressing need to develop sustainable alternative methods to manage hazardous CRT glass waste. This study assesses the feasibility of utilizing CRT glass as a substitute for natural aggregates in cement mortar. The CRT glass investigated was an acid-washed funnel glass of dismantled CRT from computer monitors and old TV sets. The mechanical properties of mortar mixes containing 0%, 25%, 50%, 75% and 100% of CRT glass were investigated. The potential of the alkali-silica reaction (ASR) and leachability of lead were also evaluated. The results confirmed that the properties of the mortar mixes prepared with CRT glass was similar to that of the control mortar using sand as fine aggregate, and displayed innocuous behaviour in the ASR expansion test. Incorporating CRT glass in cement mortar successfully prevented the leaching of lead. We conclude that it is feasible to utilize CRT glass in cement mortar production. 相似文献
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目的 研究金属复合板在冷却过程中的温度变化规律以及经过冷却后金属复合板的表面及内部温度分布规律.方法 利用二维有限差分法对金属复合板材冷却过程中的温度变化规律进行了分析,从理论上推导了使用等步长节点法求解温度的差分方程,通过设置合理的边界条件解决了金属复合板基板和复板接触界面互相影响的传热问题.结果 通过设置等步长节点的有限差分法计算得出金属复合板冷却过程的温度变化规律以及冷却后金属复合板的表面及内部温度分布,对比有限元软件模拟计算和有限差分程序计算结果,得出结论.结论 界面处温度高,越靠近两边温度越低,通过与有限元软件模拟计算作对比,验证了差分法计算的准确性. 相似文献
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《Computational Materials Science》2008,43(4):732-735
Molecular-dynamics simulations have been used to study the local structure evolution and the glass formation in the Cu40Ag60 melts rapidly cooled under high pressures. With the increase of pressures, the glass forming ability of alloy is improved. Our simulation results reveal that more compacted local structure with more ideal icosahedra than defected icosahedra is obtained. Both the annihilation of the free volume of the system and the increase of the number of the ideal icosahedra under high pressures contribute to the glass formation of the Cu40Ag60 alloy. 相似文献
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玻璃冷却速率对锂铝硅微晶玻璃晶化行为和结构的影响 总被引:1,自引:0,他引:1
玻璃成型过程中冷却速率对Li2O-Al2O3-SiO2(LAS)微晶玻璃的晶化行为及其结构均匀性具有重要影响. 有限元分析表明, 10 mm厚玻璃冷却速率显著低于2 mm厚玻璃, 冷却15 s以上玻璃的中心温度仍高于700℃, 对应的基础玻璃极易出现“析晶结石”. 利用DTA、IR、SEM等技术分析不同厚度LAS玻璃及其微晶玻璃的显微结构, 8 mm厚的玻璃冷却速率低, 样品心部析出初始晶核, 并在热处理阶段形成β-锂辉石固溶体相, 而样品表面层却为β-石英固溶体相; 与此相反, 3 mm厚的玻璃冷却速率高, 没有初始晶核生成, 热处理后得到单一均匀的β-石英固溶体相. 因此, 提高玻璃冷却速率、控制玻璃温度均匀性是制备结构均匀LAS微晶玻璃的关键. 相似文献
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Jan Schroers 《Advanced materials (Deerfield Beach, Fla.)》2010,22(14):1566-1597
Bulk metallic glass (BMG) formers are multicomponent alloys that vitrify with remarkable ease during solidification. Technological interest in these materials has been generated by their unique properties, which often surpass those of conventional structural materials. The metastable nature of BMGs, however, has imposed a barrier to broad commercial adoption, particularly where the processing requirements of these alloys conflict with conventional metal processing methods. Research on the crystallization of BMG formers has uncovered novel thermoplastic forming (TPF)‐based processing opportunities. Unique among metal processing methods, TPF utilizes the dramatic softening exhibited by a BMG as it approaches its glass‐transition temperature and decouples the rapid cooling required to form a glass from the forming step. This article reviews crystallization processes in BMG former and summarizes and compares TPF‐based processing methods. Finally, an assessment of scientific and technological advancements required for broader commercial utilization of BMGs will be made. 相似文献
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Basic study of a glass substrate in dry etching system 总被引:1,自引:0,他引:1
Hee-Hwan Choe 《Vacuum》2006,81(3):344-346
Electrostatic Chucks (ESCs) in the dry etchers for the TFT-LCD fabrications have been investigated briefly. The behaviors of glass encountering electric fields in the presence of plasma were studied. In some conditions, it has been shown that the electric force and the pressure by He backside cooling acting on the glass might be larger than the gravitational force. With a simple model, the stability condition of glass substrate was obtained. 相似文献
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张克鹏 《制冷与空调(北京)》2020,(2):21-24,30
针对某新能源商用车电池组液冷板系统,采用商用CFD软件进行流场分析,并对其进行散热降温计算和试验验证,最后对液冷板进行设计方案优化。结果表明:采用优化方案后,液冷板电芯最高温度低于温度限值(50℃),电芯之间的温差小于4℃,能够满足电池组的热管理要求,保证电池组工作处在合理温度范围内。 相似文献
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The glass forming ranges of cobalt-base binary and ternary thin film alloys containing zirconium, titanium, niobium, molybdenum, vanadium and silicon have been studied in the cobalt-rich region. The minimum solute concentration for glass formation decreased with increasing difference in atomic radii or Pauling's electronegativity, as well as the cooling rate. Cobalt-base binary alloys readily showing glass formation are shown on the glass formation diagram. The values of atomic size effect in alloys sputtered at room temperature were about 0.065, and decreased with increase of cooling rate. The value was decreased in alloys having a large heat of formation. In ternary cobalt alloys containing zirconium, niobium, molybdenum and vanadium, the glass forming range could not be interpreted as the concept of atomic size effect alone. 相似文献
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Modeling of heat transfer and solidification of composite roll was established and used to predict the thermal history and solidification process of roll during spray forming. Evolution of temperature field of the preform and cooling rate in the growing deposit during spray deposition and post-deposition were numerically simulated. 相似文献
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目的研究热冲压过程中板料的温度变化及相变情况。方法采用Abaqus软件建立了热力耦合模型,对U形件热冲压成形及冷却淬火过程进行了数值模拟,分析了板料及模具的温度分布变化,并研究了板料不同区域的冷却速率,最后进行了热冲压试验。结果研究结果表明,板料经冷却淬火后,温度分布均匀,且冷却速率均大于临界冷却速率,板料可以发生完全马氏体相变。结论板料的底部冷却速率最快,淬火后为分布均匀的、细小的马氏体组织,最终通过热冲压试验验证了模拟结果的准确性。 相似文献
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Henry S. -Y. Hsich 《Journal of Materials Science》1979,14(11):2581-2588
The glass workability during the forming process has been discussed from the aspects of rheology, heat transfer, and microstructure. The rheological behaviour and heat-transfer characteristic of glass determine the workability of glass. However, the accidentally caused changes of glass structure during melting, fining and forming can affect the workability; therefore, the apparent liquidus temperature and crystal structure of bad workability glass have been studied and compared with the good workability glass. It is found that the apparent liquidus temperature study seems to be an effective method for determining the good and bad workability glasses. The results from the mechanical strengths study of the good workability glass shows evidence of microvoids of the order of 400 Å existing in the glass structure. However, there is no such evidence in the bad workability glass; therefore, it is believed that a large flaw size, or stress concentration around the inclusions existed in the bad workability glass. 相似文献
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由于多电子枪显象管玻壳是一个变厚度组合壳体 ,很难用板壳经典理论进行求解 ,所以在设计九电子枪彩管玻壳时用有限元方法预先知道该玻壳的应力分布。通过修改设计参数 ,使九电子枪彩管玻壳能满足强度要求。在设计玻屏时采用非均匀有理B样条的曲面分析方法 ,锥体采用四条组合的非均匀有理B样条曲线旋转一周得到。本设计实现了玻屏表面外形和曲率变化及玻壳结构设计的全参数化 ,提高了玻壳的设计效率。本文还给出了计算玻壳外型的公式和一些技术参数。计算机仿真结果表明 :4 2英寸九电子枪彩色无支撑CRT的玻壳既能满足强度要求 ,又具有好的视觉效果 相似文献
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通过铜模吸铸法得到Mg65Cu25Gd10块体非晶舍金,用差示扫描量热仪(DSC)研究其晶化动力学和玻璃转变行为,玻璃转变温度Tg,晶化起始温度Tx,晶化峰值温度Tp都与加热速率有关,通过Kissinger方程可以得到表面激活能,发现晶化初始激活能Ex小于峰值激活能Ep,表明形核过程比生长过程容易,讨论了此非晶舍金的玻璃形成能力,根据JMA方程非等温模型研究了晶化动力学,Avrami参数表明在不同温度下的晶化机制是不同的. 相似文献
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SU Xiao-ping XU Lian School of Mechanical Power Engineering Nanjing University of Technology Nanjing P.R.China 《国际设备工程与管理》2008,13(3)
We point out that the finite element method offers a great functional improvement for analyzing the stamp forming process of an automobile panel. Using the finite element theory and the simulation method of sheet stamping forming, the element model of sheet forming is built based on software HyperMesh,and the simulation of the product′s sheet forming process is analyzed based on software Dynaform. A series of simulation results are obtained. It is clear that the simulation results from the theoretical basis... 相似文献
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目的解决汽车覆盖件因为冲压变形复杂,成形工艺参数难以确定的问题。方法分析了汽车前围外板的成形工艺,研究了复杂型面拉深模具的型面设计,以有限元分析软件AUTOFORM为平台,对其冲压成形过程进行了数值模拟。根据模拟结果(成形极限图、材料流动分布及材料变薄率)对拉延型面及工艺参数进行了优化。结果所得零件材料最大减薄率为17.3%,在SPCE(t=0.8 mm)材质减薄率安全范围内(18.7%),消除了成形过程中的暗伤开裂风险,成形结果得到了大大改善。结论 CAE仿真能够预测零件成形过程中存在的缺陷,优化工艺参数,指导模具设计工作。将优化结果用于指导实际生产,得到了符合质量要求的拉延零件。 相似文献