High Resolution Optical Interference Measurements of Changes in Bond-Line Thickness—A Review

A novel moire optical interference method, originally developed¹ to measure the swelling displacement normal to the plane of a simple butt joint during water uptake at the joint edge, was subsequently used to investigate the unexpected occurrence of shrinkage and, at the same time, swelling during exposure to organic solvents. In later experiments, synergistic displacement fields generated during simultaneous exposure to water and organic solvents were studied. The same method has also been used to investigate the origin of adhesion failures at copper plated-through holes in thermally cycled multi-layer circuit boards.

The method employs a thin glass cover slip as one adherend. Changes in bondline thickness flex the cover slip thereby changing the gap between the latter and a nearby optical flat. By using monochromatic light to illuminate the specimen, interference between incident and reflected light is achieved. The small displacements of individual fringes associated with changes in gap size are used to generate moire patterns which bear a 1:1 relationship to the local changes in bondline thickness. Application of thin plate elasticity theory to the flexing of the cover slip yields the stress acting normal to the joint. The magnitude of this normal stress is strongly inhomogeneous, oscillating in sign and reaching compressive values as high as 50MNm^?2 for water uptake by a simple butt joint, and exceeding the yield strength of oxygen-free high conductivity copper (1MNm^?2) for the thermal expansion that accompanies simulated soldering of a multi-layer circuit board.

Attention is drawn to the high resolution achievable with the method. Changes in bond-line thickness of the order of Δ/10, where Δ is the wavelength of the light giving rise to the interference pattern, are readily resolved. It is pointed out that the method may well be sufficiently sensitive to detect the effects of different physical properties (thermal conductivity, specific heat capacity) of adherend surface on the nature of the cured adhesive and hence on the mechanical behaviour of the bond-line.     

再生纸造纸污水的物理化学法快速净化与循环回用

介绍物理化学法快速净化高浊度工业污水工艺技术和本净水器结构设计原理,重点介绍再生纸造纸污水净化和回用工艺技术的机理及应用实践。证明物化法混凝净化技术与流体力学设计技术的巧妙结合能成功地处理高浊度无机污水和高浓度有机污水,实现工业用水闭路循环。     

Nitrogen input, <Superscript>15</Superscript>N balance and mineral N dynamics in a rice–wheat rotation in southwest China

A field experiment and farm survey were conducted to test nitrogen (N) inputs, ¹⁵N-labelled fertilizer balance and mineral N dynamics of a rice–wheat rotation in southwest China. Total N input in one rice–wheat cycle averaged about 448 kg N ha⁻¹, of which inorganic fertilizer accounted for 63% of the total. The effects of good N management strategies on N cycling were clear: an optimized N treatment with a 27% reduction in total N fertilizer input over the rotation decreased apparent N loss by 52% and increased production (sum of grain yield of rice and wheat) compared with farmers’ traditional practice. In the ¹⁵N-labelled fertilizer experiment, an optimized N treatment led to significantly lower ¹⁵N losses than farmers’ traditional practice; N loss mainly occurred in the rice growing season, which accounted for 82% and 67% of the total loss from the rotation in farmers’ fields and the optimized N treatment, respectively. After the wheat harvest, accumulated soil mineral N ranged from 42 to 115 kg ha⁻¹ in farmers’ fields, of which the extractable soil NO₃ ⁻–N accounted for 63%. However, flooding soil for rice production significantly reduced accumulated mineral N after the wheat harvest: in the ¹⁵N experiment, farmers’ practice led to considerable accumulation of mineral N after the wheat harvest (125 kg ha⁻¹), of which 69% was subsequently lost after 13 days of flooding. Results from this study indicate the importance of N management in the wheat-growing season, which affects N dynamics and N losses significantly in the following rice season. Integrated N management should be adopted for rice–wheat rotations in order to achieve a better N recovery efficiency and lower N loss.     

CuZnAl形状记忆合金热机械循环滞回曲线与振动衰减特性研究

运用电子万能拉伸试验机、动态数据采集分析仪,测试了CuZnAl形状记忆合金的力-变形滞回曲线和安装有CuZnAl形状记忆合金耗能器框架结构的减振性能.借助透射电镜、X射线衍射仪,分析了CuZnAl形状记忆合金热机械循环过程中显微组织的变化.比较了不同热处理方式、不同相变点的CuZnAl形状记忆合金热机械循环后的滞回曲线面积及减振性能.试验结果表明:CuZnAl形状记忆合金用于框架结构的被动振动控制具有较好的减振性能,同时明显降低框架结构的振动频率.马氏体CuZnAl形状记忆合金耗能器具有较大的耗能能力,热机械循环数十次以后滞回面积亦大幅度减小,但相变点高的CuZnAl形状记忆合金的滞回面积减小幅度较小.     

干湿循环作用对混凝土抗氯离子渗透侵蚀性能的影响

为了加速模拟海洋潮差区环境对混凝土耐久性能的影响,掺入矿粉和纳米改性矿物掺合料,研究了氯盐干湿循环作用对混凝土抗氯离子侵蚀性能及微观结构的影响,并将干湿循环试验与常规浸泡试验进行了对比。结果发现,干湿循环作用粗化了混凝土试件表层孔结构,增大了孔径>50 nm的孔隙含量,显著提高了自由及总氯离子浓度;掺入纳米改性矿物掺合料能降低混凝土内部孔隙率,减少有害孔含量,提高混凝土内部氯离子结合能力;干湿循环60天后混凝土表层Ca（OH）₂逐渐被消耗,生成了Friedel盐和CaCO₃。      

Deformation and life assessment of high temperature materials under creep fatigue loading

The knowledge of mechanical long term behaviour under static and cyclic loading for high temperature components requires methodologies for life assessment in order to employ the full potential of materials. A phenomenological life time prediction concept which was developed for multi‐stage creep fatigue loading demonstrates the applicability of rules for synthesis of stress strain path and relaxation including an internal stress concept, as well as mean stress effects. Further, a creep fatigue interaction concept which was also developed covers a wide range of creep dominant loading as well as fatigue dominant loading. Service‐type experiments conducted at different strain rates and hold times for verification purposes demonstrate the acceptability of life prediction method for variation of conventional 1 %Cr‐steels as well as modern high chromium 9‐10 %Cr‐steels. Generally, the service life of components is influenced by multi‐axial behaviour. Multi‐axial experiments with e.g. notched specimens and with cruciform specimens accompanied by advanced methods for calculation of stress strain path and life time prediction stress conditions are of future interest.     

高温暴露试验对PBX药柱的影响

对Ｒ８５２。Ｈ７８１、Ｈ８７２、Ｈ８７１８、ＨＭＸ－１５９、８０２１等炸 药进行高温暴露试验，考究其药柱在高温暴露条件下，不可逆尺寸变化和密度变化，并用Ｘ光衍射法研究了试验闪后主体炸药的晶体结构变化。     

The static and fatigue strength of bolted joints in composites with hygrothermal cycling

The effects of hygrothermal cycling upon the performance of a bolted composite joint was examined. Bolt torque relaxed as the number of environmental cycles increased. Comparison with analytical results suggested that the bolt torque “zigzag” behavior probably results from the natural sensitivity of bolted composite joints to the existing ambient temperature and moisture. The washer effect and specimen surface finishes were investigated to study the friction effect on joint bearing performance. Fatigue tests of specimens exposed to hygrothermal cycling exhibited greater hole elongation than specimens not exposed. High preload does improve static failure strength and the fatigue life of specimens under room conditions. Tests run on IM6/3501-6 material specimens with hygrothermal cycling show reasonable declines in fatigue life. The moisture weight gains of composites under hygrothermal cycling exposure were measured and compared to numerical results; good correlation was obtained. As a result, bolt failure occurred in some fatigue tests and is most frequently associated with large thickness-to-diameter ratio. The peak-to-peak stress was defined to study the effect of the R-ratio on bolts for the bolt failure problem.     

混凝土构件中钢筋锈蚀的电加速技术对比试验研究

采用试验方法对实验室中常用的获取锈蚀钢筋混凝土构件的电加速锈蚀技术进行对比研究.共设计了8块混凝土板试件,考虑钢筋直径和锈蚀电流密度不同,分别采用全浸入法、半浸入法和干湿交替法进行电加速锈蚀,通过激光扫描建模对锈蚀钢筋表面特征进行统计分析,对比不同方法下的锈蚀不均匀性和锈胀裂缝发展.结果发现,半浸入法和小电流干湿交替法中钢筋实际锈蚀程度明显小于法拉第定律的预测值.钢筋区段最大截面锈蚀率与平均锈蚀率的比值可用来量化锈蚀不均匀性,该比值服从广义极值分布,并受钢筋直径和截断长度的影响.全浸入法得到锈蚀钢筋的不均匀性较差,胀裂开展速率最低,不宜采用.半浸入法得到锈蚀钢筋不均匀性好,但胀裂开展速率较低,在针对锈蚀钢筋本身的研究中可采用.干湿交替法在两方面表现均较好,建议采用,但外加电流密度不宜大于50 μA/cm2.     

高密度封装IC的高加速应力试验研究

采用在线监测技术对高密度封装IC样品进行温度步进试验、温度循环试验和振动步进试验等高加速应力试验,确定了产品的耐受应力极限,验证了本试验方案和试验监测技术的有效性和可行性。通过失效分析,确定了高加速应力下电路的失效模式和失效机理。结果表明:高密度塑封IC元件在高加速温循应力下比在随机振动应力下失效更为集中,温循试验在-65~165℃温度范围内,失效显著且集中在3个循环以内,主要包括塑封料和引线框架、基板的分层以及内键合点脱离,样品耐受随机振动量级超过50grms。研究结果可为器件级高加速应力试验研究提供参考。