【作者】 余珂；

【导师】 胡兆吉；

【作者基本信息】 南昌大学 ， 化工过程机械， 2007， 硕士

【摘要】 在石油化工、能源冶金等典型过程工业的关键技术装备中大量存在着高温环境下服役的设备与管道。蠕变失效是这些高温设备与管道的主要失效形式之一，是危害设备长周期安全运行的主要因素。因此，对高温焊接结构蠕变规律的研究，是高温结构强度设计与寿命预测的重要基础，不仅具有重要的理论研究价值而且具有重要的工程应用价值。本文针对高温结构中不匹配焊接接头的蠕变速率问题，通过对稳态蠕变条件下多种简单构件的蠕变变形速率计算公式的推导，给出了静定结构和非静定结构蠕变变形速率的通用计算式，并通过紧凑拉伸试样的有限元分析计算考察了通用公式的适用性，为非均质材料焊接结构蠕变断裂控制参量C~*的理论计算奠定了理论基础。取得的研究成果如下：(1)分析讨论了高温下焊接接头的特性及其蠕变失效的基本类型，阐述了焊接结构的高温蠕变机理和蠕变过程的三个阶段；描述了焊接结构高温蠕变本构方程及稳态蠕变阶段用以表征蠕变裂纹扩展的断裂力学控制参量C~*。(2)首次推导了稳态蠕变条件下单一材料或多种材料构成的典型静定结构，如简单拉伸条件下杆状结构的加载线位移速率(?)、纯弯曲加载条件下悬臂梁的挠度变形速率(?)、纯扭转条件下的圆形杆状结构的扭转变形速率(?)等结构蠕变变形速率的计算式。在此基础上，给出了稳态蠕变条件下静定结构蠕变变形速率的通用计算式。(3)通过对典型静不定结构在稳态蠕变条件下的蠕变变形速率，如简单拉伸加载条件下二力杆结构的蠕变变形速率(?)_i、纯弯曲加载条件下多种材料层叠梁的蠕变曲率变化速率(?)、受内压作用的多层厚壁圆筒的径向蠕变变形速率(?)_i等的计算，给出了多种材料静不定结构的稳态蠕变变形速率计算的通用计算式。(4)针对广泛应用于实际工程中的紧凑拉伸试样(CT)，利用ABAQUS结构有限元分析软件，对两种材料构成的CT试样和三种材料的内压厚壁主蒸汽管线焊接接头进行了稳态蠕变的有限元分析计算，结果表明：作为一种典型的非均质材料的静定结构和静不定结构，蠕变变形速率的有限元计算结果与静定结构和静不定结构通用公式计算所得的结果吻合很好，以此验证了通用公式的适用性。更多还原

【Abstract】 Many components and pipes at high temperature conditions are used in petrochemical plants, energy sources and metallurgical plants. Creep failure is one of the main failures of the high temperature components and pipes, and is the main factor to affect in a long cycle operation. Therefore, the researches in creep for high temperature welded components are an important foundation for the design of high temperature components and life prediction, and it has important value both in theoretical research and in engineering. In this paper, the creep deformations rates for the mismatch weld joints were studied. The general formulations of steady-state creep deformation rates for statically determinate structures and statically indeterminate structures had been derived based on the formulations of various simple components under creep deformation. A lot of finite element analysis on compact tension(CT)specimen and thick-walled main steam pipe was used to confirm the applicability for the general formulation. The study in this paper gives a theoretical based on calculations of creep fracture parameter C~* for heterogeneous material welded structure and the achievements are as follows:(1) The properties of weld joints under high temperature and the basic types of failure for weld joints were discussed. The mechanism and the three stages of creep were briefly introduced, and the constitutive equation in high-temperature creep and the fracture mechanics control parameter C~* which indicates the properties for creep crack growth under the steady-state creep condition were emphatically described.(2) The analytical solutions of creep deformation rate for typical statically determinate structures under steady-state creep condition were discussed, such as the load line displacement rate (?) of rod-shaped structures in a simple tensile load, the deflection rate (?) and the slope angle rateθof cantilever beam in pure bending and the rotation angle rate (?) of a circular rod-shaped structure in pure torsion were calculated. Based on the calculation formula of creep deformation for a single material or multi-material statically determinate structures under the steady-state creep, a general formulation to calculate the for creep deformation rate for multi-material components was presented in the first time.(3) The analytical solutions of creep deformation rate for typical statically indeterminate structures under the steady-state creep condition were discussed, such as the formula of the creep deformation rate (?)_i of two-bar structure in a simple axial tensile, the curvature rate (?) of multi-layer beam in pure bending, the radial deformation rate (?)_i of the thick-walled cylinder under internal pressure were analyzed. Based on the expressions of creep deformation rate for two and three materials of statically indeterminate structure, a general formulation for the steady-state creep deformation rate of multi-material components can be obtained.(4) Compact Tension(CT)Specimen with two-material widely used in practical engineering and the typical weld joint with three-material in an ax-symmetrical thick-walled main steam pipe were analyzed by ABAQUS finite element(FE)under steady-state creep deformation condition. It was shown that the creep deformation rates gained by finite element method were well agreed with the one by general formulations, therefore the general formulations proposed in this paper was proved to be accurate and can be used in calculation for creep deformation rates.更多还原