锻压变形工艺参数对锻模模膛充填性的研究

针对锻模模膛充填困难的特点,以2A12铝合金为研究对象,以棒料模锻后的充填高度为控制目标,采用有限元数值模拟和虚拟试验相结合的方法,模拟模锻过程,分析坯料的变形行为,讨论温度、应变、应变速率等的变化和分布情况,研究不同工艺参数对模膛充填性的影响。结合正交试验与有限元数值模拟技术,对模膛充填性的影响因素进行研究,得出模膛充填能力影响因素的主次顺序、各因素的影响趋势及最优搭配方案。同时以纯铅为模拟材料,对模锻过程进行物理模拟。     

熔融挤压快速成型中支撑工艺的研究

针对单喷头的熔融挤压快速成型制作成型件的特点,必须保证能很好地去除支撑才能得到制件的要求,对熔融挤压快速成型中支撑工艺进行了研究。支撑关系到零件的加工成败、加工时间和表面质量等,提出了支撑的一些生成原则和设置辅助支撑的作用。根据挤出丝的截面形状,建立了支撑丝宽的数学模型,对生成支撑的重要工艺参数进行了分析,结果表明:栅格宽度w较出料速度v对支撑间的间隙L0影响要大,但当层高h由0.2 mm变为0.1 mm时,栅格宽度对支撑间间隙的影响基本不变,而出料速度对支撑间间隙的影响成倍增长,并进行了实验验证。     

DYNAMIC CHARACTERISTICS OF LARGE FLOW RATING ELECTRO- HYDRAULIC PROPORTIONAL CARTRIDGE VALVE

A kind of cartridge servo proportional valve is discussed, which can be used for controlling large flow rate with high performance. By analyzing the structure principle of the valve, the transfer fimction of the valve is derived. With the transfer function, some structure elements that may affect its performance are investigated. Through the numerical simulation and test study, some principles of optimality and effective methods for improving the dynamic performance of the valve are proposed. The test results conform to the results of the theoretical analysis and simulation, which proves the correctness of the study and simulation works. The paper provides theoretical basis for engineering applications and series expanding design works     

石化乙烯厂C4201一次机流量改造方案探讨

对茂名石化乙烯厂的乙烯气C4201一次机的流量改造方案进行了探讨。通过考虑各种流量调节方法的特点和C4201一次机的实际工作要求,分析比较了可用于C4201机流量调节的各种方案。针对初步优选的减小气缸内径的改造方案,阐述了在改造中需要考虑的工程问题,以及改造成本和经济效益方面的简单评价。采用的工程设计和研究方法,对压缩机流量调节方案的抉择和一般工程设计方案评价有参考意义。     

纯钛微细群孔的超声辅助光刻电解加工

采用光刻电解技术,可以选用对环境污染影响小、成本较低的腐蚀液,实现难蚀除金属材料的微细阵列结构加工,优于化学腐蚀方法。为克服电解过程中局部产生的热量和析氢造成的腐蚀不均,进行了纯钛（Ti的质量分数为99.6%）微细群孔的超声辅助光刻电解加工试验研究。试验结果表明,超声能显著改善极间工作液的循环,通过合理选择极间距离、电参数和声场参数等工艺条件,可以有效降低表面粗糙度,材料蚀除速率达到30μm/min。

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温轧原始组织及冷却速率对低碳微合金钢终态组织的影响

为了研究温轧原始组织及冷却速率对材料终态组织的影响,利用两种低碳微合金钢在不施加变形的前提下结合快速加热及冷却工艺,对不同条件下的终态组织进行了比较。结果表明:合金元素含量较高的钢中,温轧组织不同对终态组织的影响比较显著,其中以原始组织为温轧回火马氏体的更能有效获得细化和多相的终态组织;随着冷却速率的增加,铁素体平均晶粒尺寸减小,且在合金元素含量较高的钢中,更容易获得贝氏体和马氏体组织,而合金元素含量较低的钢中,冷却速率对终态组织的影响不大。     

应力比r对构件疲劳裂纹扩展的影响分析

应用能量释放率法及Paris公式对疲劳裂纹扩展问题进行了研究,详细分析比较了在不同应力比r作用下,对箱形构件未穿透型裂纹剖面各积分点的应力强度因子及裂纹扩展速率的影响.所得结论可为工程设计及裂纹无损检测人员提供一定参考.     

Triboengineering properties of ceramic oxide coatings under boundary friction against steel

The triboengineering properties of ceramic-oxide coatings are studied during boundary friction against steel 45. Ceramic-oxide coatings formed by microplasma oxidation can be used within a wide range of pressures (8–36 MPa) and sliding velocities (0.05–2 m/s) to ensure lower friction coefficient and wear rate of the materials in contact as compared to a steel-steel pair. The improved triboengineering characteristics of tribojoints with ceramic oxide are attributed to the formation of nanostructures (with 40–100 nm elements) and surface smoothing up to R _a = 5.1 nm. The nanostructure and frictional surface morphology of steel are found to be a result of oil I-40A modification by high-dispersed wear products of ceramics in the friction zone playing the role of a nanosize additive to the lubricating material.     

Contact stress of O-ring under uniform squeeze rate by photoelastic experimental hybrid method

In this paper, photoelastic experimental hybrid methods using the external traction free boundary condition and that using the relative equation of two stress functions in contact problems are developed. The validities of these two methods are confirmed through experiments and discussions. Hertz’s contact theory and the two photoelastic experimental hybrid methods explained are applied to the analysis of the contact stress of an O-ring under 10% or 20% squeeze rate. The photoelastic experimental hybrid method using the relative equation of two stress functions in contact problems was found to be more effective. When the squeeze rates of an O-ring were 10% or 20%, the maximum of absolute σ _x was greater than the maximum of absolute σ _y , but was almost equal. Maximums of absolute τ _xy were 1/8 of absolute σ _x and 1/5 of absolute σ _x when the squeeze rates of the O-ring were 10% and 20%, respectively. This paper was recommended for publication in revised form by Associate Jai-Sug Hawong received a B.S. degree in Mechanical Engineering from Yeungnam Uni-versity in 1974. Then he received his M.S. degree and Ph.D. degree from Yeungnam University in Korea in 1976 and from Kanto Gakuin University in Japan in 1990, respectively. Prof. Hawong is currently a professor at the school of Mechanical Engineering at Yeungnam University, in Gyeongsan city, Korea. He is currently serving as an vise-president of Korea Society Mechanical Engineering. Prof. Hawong’s research interests are the areas of static and dynamic fracture mechanics, stress analysis, experimental mechanics for stress analysis and composite material etc.     

Nature and removal of the modified layer in Cu CMP with ferric nitrate as oxidizer

Chemical mechanical polishing (CMP) has been introduced in the semiconductor manufacturing industry in order to achieve global planarization of wafer surfaces. Lately, copper has replaced aluminum for its better electrical and mechanical properties.Cu CMP consists in the transformation of the copper surface layer to copper oxide, which is then removed by alumina abrasive particles. The oxidizer is the chemical agent that transforms the copper into copper oxide.We have been studying the influence of ferric nitrate as oxidizer on the copper CMP.We evaluated the nature of the copper oxide with XPS observation. We found it was cuprous oxide (Cu₂O) that was actually removed by the abrasive particles.We observed that the removal rate increased with the oxidizer concentration for low concentrations, but was almost constant for higher concentrations.We also evaluated what becomes of the polishing residues for short time processes, once they are removed from the surface. The remaining copper particles are too small to be responsible for any posterior damage of the surface.