吐温-85对冷轧钢在盐酸溶液中的缓蚀性能

用失重法研究了吐温-85(聚氧乙烯山梨醇三油酸酯)对冷轧钢在盐酸溶液中的缓蚀作用,详细考察了缓蚀剂质量浓度(10～100mg/L)、温度(20～50℃)、腐蚀浸泡时间(6～144h)和盐酸浓度(1.0～8.0mol/L)对缓蚀性能的影响.结果表明:吐温-85对冷轧钢在1.0mol/L HCl溶液中具有良好的缓蚀作用,缓蚀率随缓蚀剂质量浓度的增加而增大,但随温度和盐酸浓度的增加而减小.通过Arrhenius公式和Mathur经验动力学公式分别求出了相应的腐蚀动力学参数(表观活化能Ea, 指前因子A,速率常数k, 动力学常数B),并根据这些参数讨论了吐温-85的缓蚀行为.     

Cellular/dendritic transition,dendritic growth and microhardness in directionally solidified monophasic Sn-2%Sb alloy

Horizontal directional solidification experiments were carried out with a monophasic Sn-2%Sb (mass fraction) alloy to analyze the influence of solidification thermal parameters on the morphology and length scale of the microstructure. Continuous temperature measurements were made during solidification at different positions along the length of the casting and these temperature data were used to determine solidification thermal parameters, including the growth rate (V_L) and the cooling rate (T_R). High cooling rate cells and dendrites are shown to characterize the microstructure in different regions of the casting, with a reverse dendrite-to-cell transition occurring for T_R>5.0 K/s. Cellular (l_c) and primary dendrite arm spacings (l₁) are determined along the length of the directionally-solidified casting. Experimental growth laws relating l_c and l₁ to V_L and T_R are proposed, and a comparative analysis with results from a vertical upward directional solidification experiment is carried out. The influence of morphology and length scale of the microstructure on microhardness is also analyzed.     

聚电解质的层层自组装模型及参数探讨

利用静电自组装技术在载波片基底上制备了壳聚糖/磺化木质素多层薄膜,并运用紫外―可见(UV-Vis)光谱等方法对其组装过程进行了表征。结果表明:壳聚糖/磺化木质素层层自组装是一个指数增长过程,其指数增长的数学模型可以描述为:Y=a×en/b+c,其中Y代表膜增长过程的吸光度、频率、质量、厚度等物理性能,n代表层数;a、b和c为常数。由于许多文献报道的自组装例也都可以用此指数增长模型进行描述,为此结合实验和文献数据对影响参数a、b和c的因素进行了探讨。     

一种基于PSO算法的闭环辨识方法

闭环模型辨识一直是工业先进控制领域中的一个主要课题。而现在基于粒子群优化算法PSO的辨识,大多都是连续开环系统的辨识。离散闭环模型辨识在计算机控制、运算量等方面比连续开环系统的辨识有较大的优势。文中讨论了PSO的时变惯性权重算法与参数初值的设置和选择方法。通过仿真实验表明,PSO与最小二乘递推算法相比,在有效性和一致性方面,有着明显的优势。PSO算法是一种有效地解决优化问题的群集智能算法,它的突出特点是算法中需要选择的参数少,程序实现简单,并在种群数量、寻优速度等方面较其他进化算法具有一定的优势。该方法在实际项目的应用中取得了较好的效果,应用前景广阔。     

低匹配对接接头形状参数对三点弯曲应力集中系数的影响

弹性阶段以提高低匹配接头弯曲承载能力为目标,基于有限单元法针对X形坡口低匹配对接接头三点弯曲形状设计,从材料力学方法角度出发,考察了双侧余高对称时低匹配对接接头的焊缝余高、盖面焊道宽度、焊趾过渡圆弧半径等形状参数对三个危险区弯曲应力集中系数的影响.结果表明,对母材与焊缝交界处突变区与焊缝底部中心区的影响规律为焊缝余高影响最大,盖面焊道宽度影响次之,焊趾圆弧半径影响最小;对焊趾部位影响规律为盖面焊道宽度的影响较大,焊趾圆弧半径和焊缝余高影响均较小.选择合适的形状参数可以提高低匹配接头弯曲承载能力.     

单脉冲模式下电参数对镁合金微弧氧化膜耐蚀性的影响

硅铝复合电解液体系中利用单脉冲工作模式在AZ9ID镁合金表面制备了一系列微弧氧化膜层.采用四因素三水平正交实验研究单脉冲工作模式下电流密度、正占空比、氧化时间和频率对膜层耐蚀性的影响.结果表明:各电参数对膜层耐蚀性的影响程度由高到低排列依次是氧化时间、正占空比、电流密度、频率;制备较优耐蚀性膜层的电参数为:电流密度22 A/dm2,正占空比40％,氧化时间12 min,频率500 Hz;在较优工艺方案下制得的试样与镁合金相比,其自腐蚀电位提高了36.4 mV,腐蚀电流密度下降了1个数量级.     

基于正交实验和CAE技术的梳子注射成型工艺参数优化设计

注射成型工艺参数是影响塑件质量的主要原因,文章以PP塑料成型梳子为例,采用正交实验设计技术与MoldFlow数值模拟技术相结合,优化梳子成型工艺参数,大大减少调整工艺参数次数,节约原料。     

An analysis of shrinkage defects in aluminium and aluminium-copper castings

The influence of casting parameters and alloy composition on the formation of shrinkage defects has been studied using a T-piece test casting. Macro shrinkage defects were found in pure aluminium and aluminium 0.4wt% copper castings, but not in aluminium 1, 2, and 4.5 wt.% copper alloys. The thermal data which were in general, reproducible to +/-5% showed that a negative temperature gradient prevailed in the pure and aluminium 0.4wt% aluminium alloy right up to the end of freezing. In the aluminium 1, 2 and 4.5 wt.% copper alloys the initial negative gradient changes to become positive after approximately one half of the total solidification time has elapsed. The gradient was only of the order of 2°C/mm. Variations in pouring temperature of about 50°C and filling times of a factor of three changed the solidification times by 10% only. Such variations did not change the relative freezing times at different locations in the uniform section castings. Solidification times for the 15 mm horizontal section of the castings (a/b = 0.6) were similar to those of the 25 mm sections (a/b = 1) showing that even in this simple case the modulus concept is invalid. The form of the cavities in the feeder heads is a function of the metal cast, the gas content and the grain structure. The results formed the basis of validation tests for a computer shrinkage model.**     

Mechanism of hot cracking in the heat affected zone of repair welds. Repair weld cracking of service‐exposed HP‐modified heat‐resisting cast alloys (3rd report)

For several decades it has been possible to observe a tendency to light structures, particularly when they are destined to develop power and movement by consuming energy, especially when this energy derives from conventional fuel (petroleum derivates).

Lighter means of transport permit savings on fuel consumption and contribute to the environmental protection due to the reduction of greenhouse gases. The first approach in this direction had been the utilization of innovative materials able to offer further improved mechanical strength.

Nevertheless, this way presents natural limits depending on the loss of rigidity, hence excessive deformability even in the elastic field. This fact leads to the necessity to add stiffeners and reinforcing elements, but this at the same time means increase again the heaviness. Under these conditions more complex structural solutions step forward as the ‘sandwich’-structures manufacturable in a modular way provided with remarkable versatility in terms of design and choice of material. In the 1990s a European research project named ‘Sandwich’ financed by the European Union had given a significant contribution to the industrialization of structural solutions, which present a high level of innovations using aforementioned structures.

The present work proposes a preliminary study and several results of an investigation, which has as the main subject the production of innovative structural sandwich panels, in other words hybrid-sandwich panels in steel-aluminium assembled using two different joining technologies as laser and FSW, which can successively be connected as well to steel structures as to aluminium ones.     

Self-feed device behaviour evaluation designed for assessment of operability of coated electrodes

The objective of the present work is to evaluate the effectiveness of a self-feed device for coated electrodes. This device is able to eliminate disturbances from manual operation or the use of automatic control systems during the study of coated electrode behaviour. The conjugation of different methods such as short-circuit time statistical analysis and metallographic analysis (penetration, heat-affected zone, shape and mean distance between successive solidification fronts) together with the analysis of the electric arc and electrode melting parameters allows us to obtain relationships between arc behaviour, mass transfer processes and bead appearance. This permits the extraction of criteria to describe process stability and the behaviour of the feed device employed. An appropriate statistical methodology was obtained to process the ‘duration of the short-circuit’ parameter through an appropriate adjustment of empirical distributions to a log-normal model. The self-feed device for coated electrode welding allows the repeatable and reproducible execution of welding beads in the flat position, keeping the arc length based on physical and chemical characteristics of the electrode during welding trials using 125, 140 and 160 A.