考虑空穴多级形核的损伤材料内时本构关系

本文提出了多级形核的损伤模型,建立了无形核损伤变量与无形核损伤能释放率、形核损伤变量与形核损伤能释放率之间的损伤发展的内蕴时间演变关系。     

TiS夹杂物对D6AC超高强度钢强韧性的影响

一般钢中加Ti可使晶粒细化,从而提高钢的强韧性。但D6AC超高强度铟中可否加Ti的问题,一直存在争论。因为加Ti后,可能生成含Ti夹杂物而使韧性降低。为了改善D6AC钢的韧性,首先需要弄清这一问题。本文系统研究了含Ti夹杂物对D6AC钢强韧性的影响,并与同一钢种中,含有常见的MnS夹杂物进行比较,得出: 1.TiS夹杂物对强度和延伸率的影响不明显; 2.TiS夹杂物对面缩率、冲击韧性和断裂韧性稍有影响; 3.TiS开裂％随应变增大而增加,但在同一应变下却低于MnS; 4.TiS夹杂物使K_(1C)值降低的幅度低于MnS,因此,D6AC钢中加Ti可以改善强韧性。     

熔融条件对聚苯硫醚/尼龙6共混物结晶与熔融行为的影响

用ＤＳＣ研究了熔融温度与熔融时间对聚苯硫醚／尼龙６共混物中两组分的结晶行为的影响。虽然熔融条件不同,共混物中ＰＰＳ组分的熔体结晶温度比纯ＰＰＳ的高出２０～４０℃随熔融温度提高和熔融时间延长而降低;但其熔点、结晶与熔融热比纯ＰＰＳ的低。表明ＰＡ６熔体对ＰＰＳ结晶有成核作用,ＰＰＳ与ＰＡ６组分之间存在的相互作用受熔融条件的影响。     

表面活性剂对硅酸结晶行为影响的研究

探讨了表面活性剂对硅酸结晶行为的影响，着重讨论了非离子表面活性剂的加速结晶作用。通过结晶形态、结晶速度、表面张力等的观察和测定，提出了活性剂聚集体和胶团的成核机理。     

渐缩渐扩喷嘴临界流动的空穴核化模型

在西安交通大学高压汽水实验台架上进行了破口型式为渐缩渐扩喷嘴的临界流实验，实验参数为：入口压力３，０～１６．ＯＭＰａ，入口欠热度０～６０°Ｃ。对应临界质量流速为４０～１２０×１０３ｋｇ／ｍ２ｓ。实验表明，闪蒸起始点处的热力非平衡性随入口欠热度的增加而减小，入口为饱和状态时热力非平衡性最大。提出了一个新的空穴核化模型来预测闪蒸起始点处的减压值。该模型中含有一个由实验确定的系数，并被实验证实，该系数仅为入口欠热度的函数。将该模型计算的临界流量与临界流量的实验值进行了比较，取得了满意的结果。     

铝酸钠溶液种分成核和附聚研究进展

系统总结了铝酸钠溶液种分成核和附聚过程研究进展,铝酸钠溶液种分过程中,成核和附聚过程是影响氢氧化铝产品质量的主要因素之一,众多研究者对成核和附聚过程进行了大量系统的工作。得到了一些普遍性的结论。工业条件下的种分过程晶体生长速率很小,铝酸钠溶液种分成核过程主要为二次成核,依靠附聚过程得到砂状氢氧化铝,研究表明,上述过程都与晶种的表面形貌密切相关,晶种表面性以及各种强化方法对铝酸钠溶液种分的成核和附聚过程的影响仍有待于深入研究。     

Sr Microalloying for Refining Grain Size of AZ91D Magnesium Alloy

The grain refining process of an AZ91D Mg alloy by Sr addition was studied and the heterogeneous nucleating particles of α-Mg were investigated by electron probe microanalysis （EPMA）. With 0.6 wt% Sr addition, the mean grain size of AZ91D alloy was refined from 235.4μm to 52.5 μm at the one-half radius of the ingot. The morphology of primary crystal changed from a sixford symmetrical shape to a petallike shape, Mg-Sr-Al-Fe-Mn heterogeneous nucleating particles were observed at the grain centers and Sr solute atoms presented segregation along the grain boundaries. Grain refinement was facilitated by both the Mg-Sr-Al- Fe-Mn nucleating particles and the Sr solute atoms, and the former played a dominate role in the process.     

Defect propagation at a circular interface

In this paper a nonlinear, nonuniform cohesive zone is employed to study the detailed features of quasi-static defect evolution in a simple, planar elastic system consisting of a circular inclusion embedded in an unbounded matrix subject to different remote loading configurations. The inclusion–matrix interface is assumed to be described by Needleman-type force-separation relations characterized by an interface strength, a characteristic force length and a shear stiffness parameter. Interface defects are modeled by an interface strength which varies with interface coordinate. Infinitesimal strain equilibrium solutions, which allow for rigid body inclusion displacement, are sought by eigenfunction approximation of the solution of the governing interfacial integral equations. For equibiaxial tension, quasi-static defect initiation and propagation occur under increasing remote load. For decreasing characteristic force length, a transition occurs from more or less uniform decohesion along the bond line to propagation of a crack-like defect. In the later case a critical failure load is well defined and interface failure is shown to be defect dominated (brittle decohesion). For interfaces with large characteristic force length, the matrix “lifts off” the inclusion accompanied by a delay in defect propagation (ductile decohesion). The decohesion modes ultimately give rise to a cavity with the inclusion situated within it on the side opposite to the original defect. Results for small characteristic force length show consistency with England’s results for the sharp arc crack on a circular interface (England AH (1966) ASME J Appl Mech 33:637–640) Stress oscillation and contact at the tip of the defect are observed primarily for small characteristic force lengths under extremely small loading. Results for remote tension, compression and pure shear loading are discussed as well. In the final section of the paper the results obtained in the first part are utilized to estimate the plane effective bulk response of a composite containing a dilute distribution of inclusions with randomly oriented interface defects.     

Foreign Particle Promoted Crystalline Nucleation for Growing High‐Quality Ultrathin Rubrene Films

Introducing foreign particles or agents as nucleator is an efficient way to promote crystallization in the crystal growth field, with the advantage to speed up the crystallizing rate and control the growth process. However, in the field of organic crystalline film growth, where the crystallization and morphology modulation are of significant importance in optoelectronics, this method has rarely been utilized. Particularly, some potential high‐performance materials such as rubrene face the problem of crystallization during film formation. Here a strategy is reported to promote the crystallization of rubrene films in the initial stage assisted by foreign particles. Highly ordered thin film from the sub‐monolayer stage can be achieved. Efficient charge transport and high mobility up to 2.95 cm² V^?1 s^?1 are achieved on thus ultrathin crystalline films. Such a method enables the well controlling of the film growth from the very early stage and produces uniform crystalline films with good reproducibility, thus highly promising to yield desired optoelectrical properties and applications.