Steric hindrance as a rate controlling step in stress corrosion cracking

The effect of steric hindrance in the stress corrosion cracking (SCC) of Ag-15Pd (a/o) in AgI forming solutions was studied at room temperature. The solutions used were 1 M KI at a potential higher than that of AgI formation, and iodine dissolved in different n-alcohols. It was found that Ag-15Pd (a/o) is susceptible to intergranular stress corrosion cracking in those solutions. The SCC susceptibility measured as percentage of elongation to rupture and crack propagation rate is related to the size of the active species. While in KI aqueous solutions, as well as in iodine saturated benzene or iodine saturated toluene, the rate controlling step (RCS) was the reaction at the tip of the crack, in alcoholic-iodine solutions, the diffusion rate of the iodine containing molecules became the RCS.     

Sn-9Zn无铅钎料合金的压蠕变行为研究

试验研究了Sn-9Zn合金钎料在温度为40～100℃和压力为9．3～18．6MPa范围内的压蠕变行为。结果表明：随温度和应力的升高，合金的压蠕变量增大，稳态蠕变速率的对数分别与应力对数和温度呈较好的线性关系，稳态蠕变速率符合半经验公式。在不同的温度下，应力指数n相近，平均值为5．74；不同的应力下，表观激活能Qa相差不大，平均值为51．95kJ／mol，材料结构常数为0．03，压蠕变变形是位错滑移和位错攀移共同作用的结果，控制稳态蠕变速率的主要因素为位错管道扩散过程控制下的位错攀移。     

螺栓轴向应力超声测量技术

简要介绍螺栓轴向应力超声测量的基本原理和测量方法，推导了螺栓伸长量和轴向应力的计算公式，介绍了测试过程中探头的选择、表面状态要求、温度补偿以及测量的适用条件。实际应用表明，该方法容易实施，测量精确度较高。     

The effect of corrosion inhibiting pigments on environmentally assisted cracking of high strength aluminum alloy

The effects of some corrosion inhibiting pigments on environmentally assisted cracking of 7075-T76 aluminum alloy were examined in 3.5% NaCl (pH=6.2) solution. In order to study the inhibition mechanism of these pigments in environmentally assisted cracking of aluminum alloy, electrochemical polarization tests were carried out in 3.5% NaCl (pH=6.2 and 3) and 0.1 M HCl solutions respectively with the presence and absence of these pigments. The results showed that the effects of the pigments on environmentally assisted cracking of aluminum alloy were exhibited mainly at crack initiation and the early stage of crack propagation. A nontoxic compound, composed of phosphate, molybdate, citrate, and thiazole/imidazole derivatives, was a promising pigment to inhibit environmentally assisted cracking of the alloy.     

反渗透前不锈钢换热器失效的原因及其防护

嘉兴发电厂二期工程化学补给水系统两套板框式316不锈钢加热器在短时间内相继损坏失效,在对换热器运行条件、失效宏观特征、腐蚀产物特征和材料化学成分的分析后,得出了应力腐蚀破裂的结论,并提出了相应的防范措施。     

液压缸结构设计的有限元法

采用有限元方法对液压机中的主液压缸进行结构设计。得到了详细的应力、应变分布云图及应力集中和最大变形的位置。根据分析结果，优化设计方案，并重新进行数值模拟，使设计达到要求。     

数控焊接机CNC系统软件的研究与实现

插补软件是ＣＮＣ系统软件的重要部分，本文以自行研制的ＳＫＨＪ－４焊接机８数控系统为例，重点就该焊机ＣＮＣ系统的插补软件，详细讨论了焊接轨迹插补算法理论，以及在ＣＮＣ软件开发方面应考虑的主要问题。     

球磨过程中的碰撞行为分析

本文通过对行星球磨过程的分析，研究了行星球磨过程中的磨球碰撞行为，建立了球磨工艺参数与磨球运动速度。平均自由程及碰撞频率的理论关系。结果表明：随球磨转速提高，磨球运动速度和碰撞频率将增大，装料量一定时，提高球料比，磨球运动速率和平均自由程都将减小，碰撞频率增大，装料量和球料比一定时，磨球半径愈小，磨球运动的平均自由程减减小，碰撞频率增大。     

Figure of merit for the quality of ZrO2 coatings on stainless steel and nickel-based alloy surfaces

A figure of merit (FOM) has been developed to define the quality of ceramic (e.g., ZrO₂) coatings on metal and alloy [Type 304SS and Alloy 600] surfaces. Zirconia (ZrO₂) coatings were developed as a means of protecting the metal/alloy surfaces from stress corrosion cracking (SCC) in boiling water reactor (BWR) primary heat transport circuits, by inhibiting the cathodic reaction (reduction of oxygen and hydrogen peroxide) on the surface external to the crack. The distribution of pores in the coating plays an important role in corrosion prevention, such that the lower the porosity of the coating, the better the protection afforded to the system against SCC. Since the reactors operate at high temperature (e.g., at 288 °C under full power conditions), the temperature dependence of the FOM was investigated. The figure of merit (FOM) was developed by measuring impedance data over a wide range of frequency (10 mHz-5 kHz) at temperatures of 25, 100, 200, and 288 °C in hydrogenated, buffered solutions, with the hydrogen electrode reaction (HER) being used as a “fast” redox couple. An “equivalent circuit” analog was first developed from the bare surface impedance data and this analog was then employed in a second step to model the pore bottom in defining the pore distribution on the coated surface. A lognormal distribution (LND) of the pores was assumed and the parameters of the LND were determined using a constrained optimization technique to fit the model to the experimental data for the coated surface at different temperatures. The results suggest that, as temperature increases, the coating becomes more porous, making the substrate more susceptible to corrosion cracking. At 288 °C, 87% of the SS and 85% of the Ni-alloy surfaces become porous with the pore radius varying from 0.0001 cm to 0.01 cm.     

压力容器无损检测--磁记忆检测技术

金属磁记忆检测是当前无损检测领域的一种新技术,可发现压力容器的应力集中区域,实现压力容器损伤的早期诊断。介绍了磁记忆检测的原理、标准现状、仪器要求及其在压力容器制造、检验过程中的应用,并对压力容器磁记忆检测存在的问题进行了探讨。