基于龄期度法对早龄期混凝土结构温度应力的分析

为合理确定早龄期混凝土的性能,考虑养护温度对混凝土力学性能的发展过程及终值的影响,引入了龄期度法,并以某高层大体积混凝土基础底板的温度场和应力场的有限元计算为例,讨论了应用龄期度法对早龄期混凝土结构温度应力计算问题。在有限元分析中应用龄期度法,要求每个单元都具有不同的材料属性,并且每个单元的材料属性都要随荷载步改变,计算中满足了上述两个要求,并通过计算说明了该基础底板实测内外温差超过规范规定的温差限值而未出现裂缝的原因。     

Analysis of singular stress fields at multi‐material corners under thermal loading

The scaled boundary finite‐element method is extended to the modelling of thermal stresses. The particular solution for the non‐homogeneous term caused by thermal loading is expressed as integrals in the radial direction, which are evaluated analytically for temperature changes varying as power functions of the radial coordinate. When applied to model a multi‐material corner, only the boundary of the problem domain is discretized. The boundary conditions on the straight material interfaces and the side‐faces forming the corner are satisfied analytically without discretization. The stress field is expressed semi‐analytically as a series solution. The stress distribution along the radial direction, including both the real and complex power singularity and the power‐logarithmic singularity, is represented analytically. The stress intensity factors are determined directly from their definitions in stresses. No knowledge on asymptotic expansions is required. Numerical examples are calculated to evaluate the accuracy of the scaled boundary finite‐element method. Copyright © 2005 John Wiley & Sons, Ltd.     

Stress integration and mesh refinement for large deformation in geomechanics

This paper first discusses alternative stress integration schemes in numerical solutions to large‐ deformation problems in hardening materials. Three common numerical methods, i.e. the total‐Lagrangian (TL), the updated‐Lagrangian (UL) and the arbitrary Lagrangian–Eulerian (ALE) methods, are discussed. The UL and the ALE methods are further complicated with three different stress integration schemes. The objectivity of these schemes is discussed. The ALE method presented in this paper is based on the operator‐split technique where the analysis is carried out in two steps; an UL step followed by an Eulerian step. This paper also introduces a new method for mesh refinement in the ALE method. Using the known displacements at domain boundaries and material interfaces as prescribed displacements, the problem is re‐analysed by assuming linear elasticity and the deformed mesh resulting from such an analysis is then used as the new mesh in the second step of the ALE method. It is shown that this repeated elastic analysis is actually more efficient than mesh generation and it can be used for general cases regardless of problem dimension and problem topology. The relative performance of the TL, UL and ALE methods is investigated through the analyses of some classic geotechnical problems. Copyright © 2005 John Wiley & Sons, Ltd.     

乌江某水电站压力钢管的安全性评价

基于WDL610钢的NDT评价和断裂评定表明,乌江某水电站压力钢管在焊态情况有足够的断裂抗力,是安全的.同时鉴于工程实际情况可以免除消除残余应力处理.     

受钢工况钢包壁应力场的模拟与分析

ANSYS程序是进行热和结构分析的好工具,它在钢包上的应用非常广泛。以钢包二维截面为研究对象,分别讨论受钢工况下耐火材料物性参数和不同的工作层厚度对包壁应力场分布的影响,从而为钢包设计提供一些依据。     

Sintering products molded by injecting ceramic and metal powders

The injection molding products with different volume ratios of ZrO2 ceramic powder to 316L stainless steel powder were prepared. Properties and structure of the products were characterized by X-ray diffraction(XRD), scanning electron microscope(SEM) and transmission electron microscope (TEM). The results show that the compressive stress exists in the products and the bend strength reaches 300 MPa. ZrO2 phase and stainless steel phase are uniform in samples. The toughness of ceramic increases with the increasing the content of stainless steel. Through TEM study of the interface, some crystalline orientation relationships are determined.     

预应力CFRP布加固混凝土梁的端部剥离应力分析

采用预应力碳纤维增强塑料(CFRP)对混凝土结构进行补强加固的方法是工程界近年来的研究热点之一.作者在弹性理论的基础上,推导了预应力CFRP布加固梁在均布荷载作用下端部剥离应力的计算公式.     

深井巷道围岩应力场、应变场和温度场耦合作用研究

建立了耦合条件下岩体的应力-应变关系,推导出不同变温范围条件下巷道围岩的应力和应变.实例计算表明:巷道围岩在耦合情况下比非耦合情况下的切向应力、周边位移、破碎区和塑性区半径都有较大的增加,并提出了提高耦合条件下改善巷道围岩体稳定性的措施.     

BT20合金高温变形行为的研究

为实现BT20合金锻造的数值模拟和合理制定其热成形工艺参数,利用Thermecmastor-Z型热模拟试验机对该材料在热成形条件下的变形抗力进行了研究,考察了变形温度、应变速率及变形程度与变形抗力之间的关系,并利用冶金学方法对其进行了分析.结果表明,应变速率和变形温度的变化强烈影响着合金流变应力的大小,流变应力随变形温度升高而降低,随应变速率提高而增大.通过真实σ-ε曲线,回归出可综合反映锻造热力参数对材料成形性能影响的本构方程.     

钢包用滑板的热应力有限元分析

连铸钢包使用的滑动激光器是控制连铸生产过程的关键设备之一。为了确定501滑板使用中产生裂纹的原因，抑制裂纹形成，提高滑板使用寿命，本文应用有限元法进行了滑板热应力分析，并与生产中使用的滑板比较，有限元分析显示：在滑板材质一定的情况下，滑板形状以及滑板的预紧能力和固定方式是影响滑板使用寿命的基本因素。