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KIscc and static load crack growth rate data were developed with 1 in.


For zero applied load the microcracks are found to be partially opened and a linear relationship is found between the closure load measured for the microcracks and the zero load crack opening normalized to crack length.


This relationship holds regardless of the ambient humidity during fatigue, although there are significant changes in the zero load crack openings developed with humidity.


For low interstitialhydrogen concentrations ≈10 ppm, sustainedload crack growth is controlled by creep at the crack tip.


Sustained load crack growth in zircaloy4 at elevated temperatures

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 In this paper, a fracture model named equivalent crack fracture model(ECFM) to deal with the crack tip nonlinearity of concrete is proposed. In order to study crack extension and fracture of concrete, more specific calculation formulae of this model to the fracture tests of concrete are got, and a program DESIGN1 is developed on the basis of these formulae and numerical iteration method. ECFM and program DESIGN1,are verified by comparing measured and calculated results, and the complete process of crack extension... In this paper, a fracture model named equivalent crack fracture model(ECFM) to deal with the crack tip nonlinearity of concrete is proposed. In order to study crack extension and fracture of concrete, more specific calculation formulae of this model to the fracture tests of concrete are got, and a program DESIGN1 is developed on the basis of these formulae and numerical iteration method. ECFM and program DESIGN1,are verified by comparing measured and calculated results, and the complete process of crack extension and the fracture laws of concrete are investigated by means of ECFM and DEIGN1.  本文基于线弹性断裂力学和叠加原理提出了处理混凝土裂纹尖端微裂区的等效裂纹断裂模型,推导出该模型在混凝土断裂试验中的具体计算公式,编制了计算荷载裂纹张开位移全曲线的程序DESIGNl。通过比较不同的计算结果与试验结果验证了提出的模型和计算方法,同时研究了混凝土的断裂规律及裂纹扩展全过程。  The method for calculating strain softeningdiagram is obtained based on the characteristics of concrete which has only a strain softening diagram and a complete loadcrack opening displacement (PCOD)curve by means of the minimum square method and equivalent crack fracture model (ECFM) of concrete, and a program DESIGN2 has been developed in this paper. The complete PCOD curves of concretes with different watercement ratio, maximum aggregate size, and compressive strength have been measured using wedge splitting... The method for calculating strain softeningdiagram is obtained based on the characteristics of concrete which has only a strain softening diagram and a complete loadcrack opening displacement (PCOD)curve by means of the minimum square method and equivalent crack fracture model (ECFM) of concrete, and a program DESIGN2 has been developed in this paper. The complete PCOD curves of concretes with different watercement ratio, maximum aggregate size, and compressive strength have been measured using wedge splitting test. The parameters of strain softening diagram of every concrete are calculated, and the relationships between strain softening diagram and the basic parameters studied in this paper are discussed. The calculated results show that there exists no certain relationship between the parameters of strain softening diagram.  本文基于混凝土的应变软化曲线与荷载裂纹张开位移全曲线相对应的特点,根据最小二乘法原理和混凝土等效裂纹断裂模型推导出计算应变软化曲线的方法,编制了计算程序DESIGN2。同时实测了具有不同水灰比、粗集料最大粒径、抗压强度的混凝土的荷载裂纹张开位移全曲线,通过计算探讨了混凝土应变软化曲线随基本参数的变化规律。结论表明,混凝土应变软化曲线参数之间定值关系并不存在。  In this paper the experimental study on mixed mode fracture energy of concrete was conducted by using single edge notched specimen subjected to fourpoint loading. Three series of specimens with various depths, lengths and thickness were considered. Measurements of the maximum loads were made and lots of load load point displacement,loadCMOD and loadCMSD were obtained simultaneously. Mixed mode fracture energy of concrete was calculated from the experimental results and was compared with mode I fracture energy... In this paper the experimental study on mixed mode fracture energy of concrete was conducted by using single edge notched specimen subjected to fourpoint loading. Three series of specimens with various depths, lengths and thickness were considered. Measurements of the maximum loads were made and lots of load load point displacement,loadCMOD and loadCMSD were obtained simultaneously. Mixed mode fracture energy of concrete was calculated from the experimental results and was compared with mode I fracture energy of concrete. The influence of specimen size on mixed mode fracture energy was analyzed. The three failure mechanisms of concrere specimens were discussed. The fracture analysis of fourpoint shear beams were made by use of the Smeared Crack Model. The results of the finite element analysis was found to be in good agreement with the experimental results.  利用单边切口四点剪切梁进行了混凝土ⅠⅡ见复合型断裂G_F~*的试验研究.试验过程中除测得了极限荷载P_(max)外,还测得了各试件的荷载加载点位移(F_1δ_1、F_2δ_2)全过程曲线,荷载裂纹嘴张开位移(Craek Mouth Open Displacement)曲线和荷载裂纹嘴滑移位移(Craek Mouth Slide Displacement)曲线.根据试验结果计算了混凝土ⅠⅡ复合型断裂能G_F~*,分析了试件尺寸对G_F~*的影响规律并与混凝土Ⅰ型断裂能G_F进行了比较,讨论了试件的三种不同破坏形态及其断裂机理.利用抹平裂缝模型(Smeared Crack Model)对四点剪切梁试件进行了断裂分析,计算结果与试验结果吻合较好.   << 更多相关文摘 
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