An eight‐node hybrid‐stress solid‐shell element for geometric non‐linear analysis of elastic shells

This paper presents eight‐node solid‐shell elements for geometric non‐linear analysis of elastic shells. To subdue shear, trapezoidal and thickness locking, the assumed natural strain method and an ad hoc modified generalized laminate stiffness matrix are employed. A selectively reduced integrated element is formulated with its membrane and bending shear strain components taken to be constant and equal to the ones evaluated at the element centroid. With the generalized stresses arising from the modified generalized laminate stiffness matrix assumed to be independent from the ones obtained from the displacement, an extended Hellinger–Reissner functional can be derived. By choosing the assumed generalized stresses similar to the assumed stresses of a previous solid element, a hybrid‐stress solid‐shell element is formulated. Commonly employed geometric non‐linear homogeneous and laminated shell problems are attempted and our results are close to those of other state‐of‐the‐art elements. Moreover, the hybrid‐stress element converges more readily than the selectively reduced integrated element in all benchmark problems. Copyright © 2002 John Wiley & Sons, Ltd.     

Recrystallization/precipitation behaviour in microalloyed steels

Microalloyed high-strength low-alloy (HSLA) steels contain additions of Nb, V, Ti, or in combination, in amounts of 0.01 to 0.1 weight percent to improve mechanical properties, which are strongly dependent on the thermomechanical interaction taking place in the course of rolling mill processes. The recrystallizatian of hat-twisted austenite has been investigated in a cylindrical specimen (f 6×50 mm) machined from hat rolled plates of 0,052 wt % Niobium microalloyed steel. Continuous and interrupted torsion test were carried out in the temperature range 1123 K to 1173 K after a solution treatment of 1.5 minutes at 1423 K and torque-twist data were analysed. The various methods were discussed for obtaining results from torsion tests. The effect of precipitation kinetics was appreciated by way of connection t_p/t_p(red), where t_p is the experimental measured time for the peak stress and t_p(red) is the newly defined reduced time. The softening ratio X and time t_0.05R for start of static recrystallization were established.

The correlation between precipitation and recrystallization is presented as a graphs for chosen requirements (temperature of austenitization, carbon and niobium content and strain rate). If temperature goes below 850°C, the restoration processes are hardly suppressed, both are limited by diffusion and Nb(CN) precipitation, which are extended dynamically in the range of strains rates 10⁻² to 1 s⁻¹.

In the present paper, an attempt is made to derive the PRTT diagram and to define all mathematical equations for describing recrystallization times t_0.05R, t_0.5R, t_0.95R and t_0.05P for the start of precipitation. In real metal forming processes such as the hot rolling of plates or strips the knowledge of these parameters and results is extremely important for the the correct microstructure and sheet quality to be obtained.     

Use of TNSAC in phosphate adsorption studies and relationships. Isotherm relationships and utility in the field

There is a need for developing low cost, easily and abundantly available, yet efficient, adsorbents for the removal of phosphates during the tertiary treatment of wastewaters. The tamarind nut shell activated carbon (TNSAC) prepared on a laboratory scale has been used to evaluate its performance for phosphate adsorption. This paper describes the laboratory production of this adsorbent material in its various forms, and discusses the effects of the TNSAC process variables (the unrinsed and rinsed forms of the TNSAC and the impregnation ratio) on its performance in adsorbing phosphate. The material has been shown to be a good alternative adsorbent. As much as 95% phosphate removal by the unrinsed TNSAC is possible in about 30 min under the test conditions. The phosphate adsorbing capacity is about two times higher for the unrinsed TNSAC in comparison to the rinsed TNSAC. The adsorption rates, however, transit to extremely low rates towards the end when equilibrium conditions could be attained in about 2 h contact time. The phosphate removal mechanics are adsorption and precipitation/ion exchange when unrinsed TNSAC is used, and adsorption alone for the rinsed TNSAC. The maximum phosphate removal is found to take place at an impregnation ratio of 1.0 for both forms of the TNSAC.     

连续式超临界流体萃取进卸料装置

概括了超临界流体萃取技术和包括连续式操作在内的超临界流体萃取装置的研究现状 ,提出了一种通过球形进、卸料器完成固相物料超临界流体萃取连续化进卸料的装置 ,介绍了该装置的结构和工作原理 ,给出装置中各主要部件的计算方法。     

鞍钢1780mm热轧生产线"三电"工程施工概述

概述了鞍钢1780mm生产线技术改造工程中供电、传动及自动控制系统的构成、安装及调试技术要点,以及技术经济效果评述,可供同类工程施工参考.     

新抗冲型ACR的合成与研究

采用种子乳液聚合法制备了含有PBA＼PMMA＼PS三种组分的丙烯酸酯类抗冲型改性剂ACR，在ACR的幔层结构中引入接枝剂甲基丙烯酸烯丙酯（ALMA）来完善幔层结构，从而实现核一壳之间良好的结合，用红外光谱（FTIR）和差示扫描量热法（DSC）对ACR的组成和结构进行表征。研究结果表明：由PBA＼PMMA＼PS三组分构成的ACR在抗冲击性能上要略优于由简单的PBA＼PMMA构成的ACR，苯乙烯单体（St）最多可以取代大约1／3壳层的甲基丙烯酸甲酯（MMA），甲基丙烯酸烯丙酯（ALMA）的引入对幔层结构的完善起了显著的作用。     

热带钢连轧机工作辊温度场和热凸度预报模型

采用一种具有较高精度的样条有限条法对轧制过程中工作辊的温度场和热凸度进行计算和预报。结果证明，该模型理论计算值与现场实测值吻合较好，可以较准确地计算和预报热带钢连轧机工作辊的热凸度。     

热丝辅助ECR CVD制备cBN薄膜

立方氮化硼(cBN)是一种具有广泛应用价值的Ⅲ-Ⅴ族二元化合物，其优异性质可与金刚石相比拟或胜之．立方氮化硼的制备与性能研究是近二十年来材料领域关注的焦点之一．我们用热丝辅助ECR CVD方法制备了cBN薄膜，并初步探讨了热丝对cBN形成的作用．偏压并不是cBN形成的唯一主要条件，活性粒子也有非常关键的作用．