Structural modifications of Callovo-Oxfordian argillite under hydration/dehydration conditions

The clay minerals are among the first silicated minerals to be transformed physically and chemically during changes of temperature, pressure, relative humidity and fluid composition. One of the first physical processes, extremely rapid, is the hydration and/or dehydration of swelling clays minerals. These processes could generate changes of the clay structure and consequently the texture of an argillaceous rock. In order to observe in situ structural modifications on a deep argillaceous rock “argillite” (Parisian basin, in France) according hydration–dehydration cycles, an Environmental Scanning Electron Microscope (ESEM) was used. This instrument allows the possibility to observe geological samples in their natural state without preliminary preparation or modification. Two types of samples were prepared, parallel and perpendicular to the lithology. Then, each sample was submitted to three water condensation/evaporation cycles.The observed samples were from the Callovo-Oxfordian formations in HTM 80743, HTM 983, HTM 02618 and EST 2159 cores. ESEM observations show that the water sensitivity of these bulk samples depends directly on the clay mineral proportion in the rock, and on the clay family present. It is also obvious that the water sensitivity depends on the anisotropy of the pore structure and the particle size and total porosity. The main structural modifications observed were the cracking of the surface, particles aggregation/disaggregating and opening/closing of pores and/or cracks.     

乙烯裂解炉用高温隔热材料性能的优化

为了提高我国石化行业乙烯裂解炉内衬用轻质隔热耐火材料的安全性和隔热效率 ,对国产高温隔热材料的热物理性能进行了探讨 ,并且与国外同类产品进行了对比分析。指出了提高隔热材料的使用寿命 ,主要是通过改良砖材结构中的矿相组成 ;而提高国产高温隔热砖性能的技术途径是对显微组织结构 (主要为气孔形状、大小 )的优化以及对Fe2 O3含量的控制     

Computation of Mixed-Mode Stress Intensity Factors for Cracks in Three-Dimensional Functionally Graded Solids

This work applies a two-state interaction integral to obtain stress intensity factors along cracks in three-dimensional functionally graded materials. The procedures are applicable to planar cracks with curved fronts under mechanical loading, including crack-face tractions. Interaction-integral terms necessary to capture the effects of material nonhomogeneity are identical in form to terms that arise due to crack-front curvature. A discussion reviews the origin and effects of these terms, and an approximate interaction-integral expression that omits terms arising due to curvature is used in this work to compute stress intensity factors. The selection of terms is driven by requirements imposed by material nonhomogeneity in conjunction with appropriate mesh discretization along the crack front. Aspects of the numerical implementation with (isoparametric) graded finite elements are addressed, and examples demonstrate the accuracy of the proposed method.     

某厂主厂房框架梁裂缝分析及处理

本文对某厂主厂房框架梁裂缝产生的原因进行了分析、鉴定，并针对裂缝的分布情况及大小提出了不同的加固处理方法，经生产证实，该主厂房框架梁加固方法成功可靠。     

株洲冶炼厂133m钢筋砼烟囱的加固

对株洲冶炼厂１３３ｍ钢筋砼烟囱经过３０多年的二氧化硫气体影响的现状进行了分析，介绍了在烟囱正常使用的前提下进行加固处理的方案，并对类似的烟囱如何延长其使用寿命和加固中注意的问题提出了几点建议。     

乙烯裂解炉及其管道设计

乙烯是最基本的化工原料之一,对我国经济发展起到重要的支撑作用。结合以往工程设计的实践经验,简要介绍了几种乙烯裂解炉的型式与特点,并就乙烯装置裂解炉的管道设计谈了自己的思路与方法,对裂解炉区重要管系的设计进行了分析和说明。     

发电厂主厂房受地基变位影响空间结构仿真计算研究

根据某火电厂厂房上部结构受到地基蠕滑变形影响，引起主要构件受损或破坏这一实际，对整体空间结构，按照地基变形发展趋势及结构物加固后的实际刚度，用有限元法作了空间仿真计算研究。     

中国大跨径混凝土梁桥典型病害剖析及防治技术简介

预应力混凝土梁桥以其结构刚度好、行车平顺、养护简单等一系列优点而备受工程界欢迎。然而近年来,大跨径预应力混凝土梁桥在施工过程或使用阶段,普遍出现各种不同性质的病害,最常见的病害为箱梁开裂和结构长期下挠;这些病害对桥梁的耐久性和营运的安全性构成了威胁,甚至在一定程度上阻碍、制约了大跨径预应力混凝土梁桥的发展。针对既有大跨径预应力混凝土梁桥的病害,病害成因分析、对桥梁损伤的诊断、损伤桥梁的修复加固方法是该类桥梁应用中亟待解决的问题。本文首先阐述我国现有大跨径梁桥的病害状况;大跨径预应力混凝土梁桥产生这些病害的原因,涉及设计计算、施工工艺、养护管理、材料性质等多个方面,针对各典型病害分析其原因,并给出相应的预防措施,以期对实际工程有所裨益。     

Modeling for prediction of restrained shrinkage effect in concrete repair

A general model of autogenous shrinkage caused by chemical reaction (chemical shrinkage) is developed by means of Arrhenius' law and a degree of chemical reaction. Models of tensile creep and relaxation modulus are built based on a viscoelastic, three-element model. Tests of free shrinkage and tensile creep were carried out to determine some coefficients in the models. Two-dimensional FEM analysis based on the models and other constitutions can predict the development of tensile strength and cracking. Three groups of patch-repaired beams were designed for analysis and testing. The prediction from the analysis shows agreement with the test results. The cracking mechanism after repair is discussed.     

Residual Stress Measurement and Fatigue Crack Growth Prediction after Cold Expansion of Cracked Fastener Holes

The cold expansion technique is often used to introduce beneficial compressive stress at fastener holes, and can be used for remedial work where cracks already exist. In this paper, results are presented showing the effect of preexisting cracks on the residual stress field produced by cold expanding a fastener hole, and on subsequent fatigue crack growth. The effect on the residual stresses was experimentally evaluated in two ways: indirectly, in terms of retained expansion and directly, by measurement of the stresses using the X-ray and neutron diffraction techniques. The retained expansion ratio showed that cold expansion is more sensitive to the existence of precracks at lower levels of applied interference, and the inlet and outlet faces have different behavior. The stress measurements showed that preexisting cracks reduce the compressive residual stresses more on the mandrel inlet face than on the outlet face and in the middle of the specimen. The effect on fatigue crack growth rates was modeled using a linear-elastic fracture mechanics approach. It was found that cold expansion of a hole containing a preexisting crack longer than 1 mm introduces little benefit for subsequent fatigue crack growth behavior.