The fracture characterization of highly irradiated Type 316 stainless steel

The fracture characteristics of 20% cold worked Type 316 stainless steel irradiated at 377–400°C to a fluence of 11 × 1022n/cm² (E > 0.1 MeV) were evaluated based on SEM fractography andJ-integral fracture toughness data. Compact tension specimens were tested at temperatures ranging from 232 to 649°C. A significant reduction in fracture toughness after irradiation was observed, which correlated well with the fracture morphology of the material. It was found that irradiation induces a shift in the transgranular-intergranular fracture transition temperature to a lower temperature. Irradiated specimens exhibited transgranular channel fracture from 232 to 538°C and intergranular fracture at 649°C, while unirradiated specimens failed in a transgranular ductile fracture mode up to 549°C. SEM fractographs revealed plate-like, faceted fracture surfaces of irradiated specimens. The faceted fracture appearance is associated with flow localization and dislocation channeling, phenomena that undoubtedly contribute to the decrease in fracture toughness. The possibility that ordered -phase particles are partially responsible for the reduced toughness as well as for irradiation hardening is discussed.

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Résumé En utilisant la fractographie SEM et des données de ténacité à la rupture basées sur l'intégrale J, on a évalue les caractéristiques à la rupture d'un acier inoxydable type 316 écroui de 20% et irradié à 377–400°C sous un flux intégré de 11.1022 n/cm² (c > 0.1 MeV).Des éprouvettes de traction compactes ont été soumises à essai à des températures comprises entre 232 et 649°C. On a observé une réduction significative de la ténacité à la rupture due à l'irradiation, ceci étant confirmé par la morphologie de la rupture. L'irradiation provoque un glissement de la température de transition de rupture intergranulaire-transgranulaire vers une température plus basse. Des échantillons irradiés ont fait état d'une rupture transgranulaire entre 232 et 530°C et d'une rupture intergranulaire à 649°C.Par contre, des échantillons non irradiés se sont rompus de manière transgranulaire jusqu'à 649°C. Les microfractographies révèlent, sur les éprouvettes irradiées, des surfaces de rupture à facettes, qui sont associées à une localisation de l'écoulement plastique et à une concentration des dislocations, phénomène qui, sans nul doute, contribue à réduire la ténacité à la rupture. On discute de la possibilité d'une responsabilité partielle de particules de phase y' dans la réduction de la ténacité et dans le durcissement dus à l'irradiation.

     

Some experiments on estimating the 3-d motion parameters of a rigid body from two consecutive image frames

This paper describes the results of some experiments on estimating the 3-D motion parameters of a rigid body from two consecutive TV images, and discusses several factors which affect the accuracy of the results. These factors include the sizes of the motion parameters themselves, the accuracy of the raw data, and the number of point correspondences. In addition, we address two related topics: determining corner positions to subpixel accuracy and matching point patterns with different scales.     

PE,PP专家系统

简述了专家系统的发展及在塑料加工中的应用特点,介绍了成功地开发PE、PP专家系统的方法、技术及实现功能,并提出了采用压缩库大大节约存贮空间的新途径。     

膜催化反应器的分析与模拟

分析了膜反应器的出现、发展和最新研究。论述了几种膜反应器中气体的传递机理,定量分析了膜反应器中控制传递与反应的模型方程式以及计算机模拟和实验研究结果。最后评价了两类膜反应器的操作特性,以⊿n<0、⊿n=0和⊿n>0三类不同的催化反应作为模型反应与传统的PFR 和 MFR 的操作特性作了对比。     

Transport anomalies and magnetic properties of Sn x Eu1.2−x Mo6S8 alloys

We have measured the resistance R, magnetoresistance, and magnetization of sintered samples of the compounds Sn _x Eu_1.2–x Mo₆S₈, where x = 0, 0.12, 0.24, and 0.48. A large resistance anomaly beginning at T ~ 100 K and extending to low temperatures is found in all of the alloys except x = 0.48, which had a high superconducting transition temperature T _c ~ 11.3 K. The resistance anomaly, which appears to be correlated with the depression of T _c, is also correlated with a large negative magnetoresistance at temperatures T 12 K. For all samples except x = 0.48, that part of the magnetoresistance attributed to spin-flip scattering is proportional to the square of the magnetization M ² and is 30–40% of R (0) for some samples. Magnetization measurements are consistent with a spin-7/2 paramagnetic behavior of Eu²⁺ ions when allowance is made for a concentration of 20–30% nonmagnetic (J = 0) Eu³⁺ ions as determined from Mössbauer measurements. The experimental results are inconsistent with predictions of dilute magnetic alloy Kondo models. We speculate that the resistance anomaly and suppression of T _c for x 0.24 are associated with a semiconductor-like behavior.Work performed under the auspices of the U.S. DOE.Work supported by NSF Research Grant DMR 78-2428.     

谈公共设施中的环境陶艺形态

探讨公共设施环境陶艺形态的类型、表现手法及特点,指出公共设施中的环境陶艺形态设计要强调实用与审美、环境相统一。     

A structural model for the cholesterol-phosphatidylcholine complexes in bilayer membranes

Based on the structural properties of phospholipid and cholesterol molecules, and making use of the known structural and motional effects of cholesterol and its analogs on phospholipid bilayers, a model for the cholesterol-phosphatidylcholine complex is proposed. In this model, the 3β-hydroxyl group of cholesterol is assumed to engage in hydrogen bonding with the carbonyl oxygen of the fatty acyl groups in phospholipids. Some specific configurations of the saturated and unsaturated fatty acyl chains of the phospholipid are suggested to participate in van der Waals attractive interactions with the α and β surface of the steroid nucleus.