Evaluation method of dam behavior during construction and reservoir filling and application to real dams

In this paper we analyzed a real fill-type dam, named the Minami-Aiki Dam, to verify a numerical consolidation method with an elastoplastic model for unsaturated soils. The validities were conducted by comparing the analyzed and measured values during construction and impounding. The settlements calculated showed good agreement to those observed. Though the changing patterns of the measured and calculated pore water pressures were similar, the amounts of pore water pressures induced by the self-weights of embankment and the dissipation speeds were different. The earth pressures measured at the bottom of the core zone showed good agreement with those calculated. This method is valid for estimating behavior of fill-type dams during construction and impounding.     

Fe-Cr-Mn奥氏体合金的辐照体胀与诱起晶界偏析行为的研究SCIEI

本文采用电子束辐照,研究了Fe-15Cr-xMn合金以及添加W,V合金的孔洞体胀和诱起晶界偏析行为,并对包含晶界在内的辐照区进行成分分析。结果表明,在Fe-Cr-Mn系合金中孔洞体胀孕育期可以被强烈抑制,晶界偏析也减少。特别是,合金中添加W,V效果更加明显。用Mn代替Ni,通常要发生体胀和相的不稳定性,由于反Kirkendall效应导致Ni和Mn的扩散行为不同,使Fe富集在尾闾处,局部地区形成铁素体,有利于减少体胀和晶界偏析。     

Effect of shot peening on fatigue limit of surface flawed samples

The effects of shot peening on the fatigue limit of specimens having a semicircular notch of varied surface length, 2a , are investigated. In the case of un-peened specimens, the fatigue limit of specimens having a notch of a = 0.05 mm was equal to that of the un-notched specimens. However, the fatigue limit of a = 0.3 mm was 46% smaller than that of the un-notched specimens. On the contrary, in the case of peened specimens, the fatigue limit of a = 0.2 mm was equal to that of the un-notched specimens and furthermore, that of a = 0.3 mm was only 5% smaller than that of the un-notched specimens. Multiple non-propagating cracks were observed in peened specimens after fatigue testing. The stress intensity factor of the maximum non-propagating crack size corresponded to that of a = 0.2 mm notch. These results indicate that shot peening increases fatigue limit and decreases the likelihood that a surface flaw will result in failure.     

A new methodology to guarantee the structural integrity of Al2O3/SiC composite using crack healing and a proof test

Structural ceramics are brittle and sensitive to flaws. As a result, the structural integrity of a ceramic component may be seriously affected by inherent flaws. Self-crack-healing is an excellent answer to this problem. At the moment, however, there is no technique to heal embedded flaws. Therefore, a technique to guarantee the reliability of ceramic components is demanded, and thus a technique using crack healing followed by proof test was developed by K. Ando et al. to accomplish this. With this technique, testing the mechanical behaviour of the crack-healed zone is very important for ensuring the structural integrity of a ceramic component. In this study, first Al₂O₃/SiC composite with an excellent crack-healing ability was sintered. Second, a crack was introduced on the sample (3 mm × 4 mm × 36 mm), which reduced the bending strength by about 80%, and subsequently the crack was healed. Third, a proof test was carried out on the crack-healed sample. Last, using the crack-healed and proof-tested sample, a fracture test was carried out up to 1373 K. The measured minimum fracture stress (σ_Fmin) was compared with the theoretical minimum strength (σ_G) from room temperature (R.T.) to 1373 K. It was concluded that σ_G showed good agreement with σ_Fmin up to 1373 K and that the crack healing followed by proof test was an excellent technique to increase the survival probability by administering a proof test and to guarantee the reliability of Al₂O₃/SiC composite.     

超声回波特征值的统计学分析方法

介绍了一种基于统计学假设检验理论进行模式识别中的特征评价与选择的方法，该方法理论意义比较清楚，计算简单，能够选出合适的特征，其实现是采用统计学中t检验方法来进行的，即用检验各组样本特征之间差异是否显著，来评价所提取的特征值的优劣；采用启发武方法和判别分析来进一步考察所提取的特征值的分类效果．实现了超声回波特征空间的降维处理与最佳特征子集选择。     

Threshold and growth mechanism of fatigue cracks under mode II and III loadings

ABSTRACT The fatigue crack growth behaviour of 0.47% carbon steel was studied under mode II and III loadings. Mode II fatigue crack growth tests were carried out using specially designed double cantilever (DC) type specimens in order to measure the mode II threshold stress intensity factor range, ΔK_IIth. The relationship ΔK_IIth > ΔK_Ith caused crack branching from mode II to I after a crack reached the mode II threshold. Torsion fatigue tests on circumferentially cracked specimens were carried out to study the mechanisms of both mode III crack growth and of the formation of the factory‐roof crack surface morphology. A change in microstructure occurred at a crack tip during crack growth in both mode II and mode III shear cracks. It is presumed that the crack growth mechanisms in mode II and in mode III are essentially the same. Detailed fractographic investigation showed that factory‐roofs were formed by crack branching into mode I. Crack branching started from small semi‐elliptical cracks nucleated by shear at the tip of the original circumferential crack.     

Bearing failure in plain woven C_C composites

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Formation and microwave dielectric properties of Sr(Ga0.5Ta0.5)O3-based complex perovskites

The Sr(Ga0.5Ta0.5)O3-based perovskites with O2- and/or Sr2+ vacancies were formed by changing the A-site and/or B-site cation ratios. The Sr-deficient perovskites with a limited composition of Sr0.86(Ga0.36Ta0.64)O3 could be obtained, whereas oxygen vacancies were hardly created. The B′-site Ga3+ cation could be replaced with large Sc3+, In3+, Y3+, Nd3+ and La3+. The crystal symmetry of the complex perovskites changed from cubic (B′=Ga3+, Sc3+, In3+) to tetragonal (B′=La3+) through rhombohedral (B′=Y3+, Nd3+). The dielectric permittivities of these ceramics indicated no distinct dependence on the B′-site cation species. The temperature coefficient of permittivity might be associated with the symmetry change of the perovskite phases. Higher microwave Qf values, >Qf=38 000 GHz, were obtained for our complex perovskite ceramics, except with B′=La3+. This revised version was published online in July 2006 with corrections to the Cover Date.     

Difference of histology and elemental composition of the cervical enamels among human permanent teeth

The purpose of this study is to clarify the difference of histology and elemental composition of the cervical enamels among the human permanent teeth. The re-ground surfaces at the cervical enamels of them were observed under scanning electron microscopy (SEM). The contents of seven elements were analyzed quantitatively with electron probe microanalyzer (EPMA). The widths of the rod sections at the cervical enamels were larger than those at the cuspal enamels. The rod sections at the mesial cervical enamels in the incisors were more obscure and more decayed by acid solution than those in the premolars and molars. The calcium and phosphorus contents of the cervical enamels were significantly lower than those of the cuspal enamels. The carbon content of the cervical enamels was significantly higher than that of the cuspal enamels. The calcium and phosphorus contents of the cervical enamels were the significantly highest in the premolars. The carbon and sodium contents of the cervical enamels were significantly highest in the premolars. It is thought that the calcification level is lower, while the content of organic matter is higher at the cervical enamels than those at the cuspal enamels. It is considered that the sodium causes high calcification.     

新日本钢铁公司高强度汽车用钢板的开发

在对汽车提高燃料利用率、节能和提高冲撞安全性的要求日益强烈的情况下,不增加车体重量而提高安全性的方法之一,就是使用高强度钢板.钢板高强度化带来的最大问题就是钢板加工性能变差.为适应用户的要求,新日铁已经开发出各种高强度钢板.本文对适应于汽车不同部位的、具有良好成形性的各种高强钢板的特点及冲撞吸收能、疲劳强度等特性进行了介绍.