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181.
182.
Y.S. Tai 《Theoretical and Applied Fracture Mechanics》2009,51(2):117-128
Reactive powder concrete (RPC), a composite that has been developed in recent years, is a special mixture that is cured to have a higher compressive strength than that of concrete (about 200 MPa). Adding a few steel fibers can markedly increase its mechanical properties, such as tensile and bending strength, impact resistance and toughness. Hence, RPC is highly promising for use in the containment structures of nuclear power plants and in the protection of military facilities. This study evaluates the resistance of ultra-high strength concrete targets by high-velocity impact experiments. Test variables include the impact velocity and the amount of steel fibers added. The experimental results reveal that RPC plates, because of their higher compressive strength, are more fragile than normal concrete (NC) plates. However, adding a small amount of steel fibers significantly improved the impact resistance of the target plates. Moreover, a numerical simulation based on the nonlinear finite element code LS-DYNA was performed. The results of the numerical simulation have a good agreement with the experimental data and can be used for further research. 相似文献
183.
对分布式光纤裂缝检测技术中光纤-混凝土复合体的微观力学行为进行了分析. 考虑了涂覆-护套、护套-混凝土双界面的状态非线性,混凝土采用双线性各向同性强化模型以消减局部应力集中,避免护套-混凝土之间的过度穿透. 采用试验确定的接触对力学参数,用ANSYS进行了数值模拟,得到了光纤-混凝土复合体的微观应力分布及光纤的曲率分布. 定量分析了缝宽与弯曲损耗的关系,计算结果与试验结果符合较好,从理论上验证了光纤布置方式、护套厚度对传感灵敏度和动态范围的影响,为分布式光纤裂缝检测技术提供了修正的微观力学分析理论和方法. 相似文献
184.
BEHAVIOR OF AIR-ENTRAINED CONCRETE AFTER FREEZE-THAW CYCLES 总被引:2,自引:0,他引:2
Huaishuai Shang Yupu Song Jinping Ou 《Acta Mechanica Solida Sinica》2009,22(3):261-266
The experimental study of air-entrained concrete specimens subjected to different cycles of freeze-thaw was completed. The dynamic modulus of elasticity, weight loss, the cubic compressive strength, compressive strength, tensile strength and cleavage strength of air-entrained concrete were measured after 0, 100, 200, 300, 400 cycles of freeze-thaw. The experimental results showed that the dynamic modulus of elasticity and strength decreased as the freeze-thaw was repeated. The influences of freeze-thaw cycles on the mechanical properties, the dynamic modulus of elasticity and weight loss were analyzed according to the experimental results. It can serve as a reference for the maintenance, design and the life prediction of dams, hydraulic structures, offshore structures, concrete roads and bridges in northern cold regions. 相似文献
185.
We use a mathematical technique, the self-similar functional renormalization, to construct formulas for the average conductivity
that apply for large heterogeneity, based on perturbative expansions in powers of a small parameter, usually the log-variance
of the local conductivity. Using perturbation expansions up to third order and fourth order in obtained from the moment equation approach, we construct the general functional dependence of the scalar hydraulic conductivity
in the regime where is of order 1 and larger than 1. Comparison with available numerical simulations show that the proposed method provides reasonable
improvements over available expansions. 相似文献
186.
We derive a novel integral equation relating the fluid pressure in a finger-like hydraulic fracture to the fracture width.
By means of an asymptotic analysis in the small height to length ratio limit we are able to establish the action of the integral
operator for receiving points that lie within three distinct regions: (1) an outer expansion region in which the dimensionless
pressure is shown to be equal to the dimensionless width plus a small correction term that involves the second derivative
of the width, which accounts for the nonlocal effects of the integral operator. The leading order term in this expansion is
the classic local elasticity equation in the PKN model that is widely used in the oil and gas industry; (2) an inner expansion
region close to the fracture tip within which the action of the elastic integral operator is shown to be the same as that
of a finite Hilbert transform associated with a state of plane strain. This result will enable pressure singularities and
stress intensity factors to be incorporated into analytic models of these finger-like fractures in order to model the effect
of material toughness; (3) an intermediate region within which the action of the Fredholm integral operator of the first kind
is reduced to a second kind operator in which the integral term appears as a small perturbation which is associated with a
convergent Neumann series. These results are important for deriving analytic models of finger-like hydraulic fractures that
are consistent with linear elastic fracture mechanics.
Submitted to Journal of Elasticity on February 5, 2007. Re-submitted with revisions on May 30, 2007. 相似文献
187.
Jian Zhou Guang Ye Erik Schlangen Klaas van Breugel 《Theoretical and Applied Fracture Mechanics》2008,49(2):199-205
The differential volume changes between repair material and substrate concrete induces stresses in concrete overlays. These stresses could cause the repair material cracking or the interface delamination, which facilitate the penetration of harmful substances into concrete and hence accelerate the deterioration of concrete overlays. In order to investigate the characteristics of these stresses, an analytical model has been developed based on the plate theory and the assumption of the linear relation between shear stress and slip at the interface. This model is able to calculate the tensile stress in the repair material, shear and normal stresses at the interface and the corresponding strains. With this model, the influence of the interface shear stiffness, the dimension of the concrete overlay, and the elastic moduli of two materials on stresses and strains was studied. 相似文献
188.
189.
利用LS-DYNA程序的用户自定义模型功能,在LS-DYNA程序中嵌入了用于描述混凝土及钢筋混凝土侵彻贯穿的动态损伤模型。模型拉伸部分用Taylor-Chen-Kuszmaul(TCK)模型描述,体现了应变率对拉伸作用的敏感性;压缩部分则采用Holmquist-Johnson-Cook(HJC) 强度模型。模型中考虑了拉伸损伤、压缩损伤、应变软化、静水压力效应以及应变率效应。利用该方法对弹体攻角非正侵彻混凝土靶过程中的弹体变形、混凝土靶的损伤破坏、弹体的速度变化规律及弹体的变形进行了计算,并将计算结果与实验结果进行了比较,结果表明,采用该模型可以较好地模拟弹体非正侵彻混凝土过程。 相似文献
190.
采用60%的超细工业废渣取代水泥制备了抗压强度达200 MPa的生态型活性粉末混凝土(RPC),采用分离式霍普金森压杆装置对不同纤维掺量的RPC材料进行了4种方式的多次冲击压缩实验。定义了材料多次冲击压缩标准化强度,揭示了冲击次数、冲击方式、纤维掺量对材料抗多次冲击性能的影响规律。研究表明随着纤维掺量的提高,材料抗多次冲击的能力不断提高。随着冲击次数的增加,材料的损伤程度不断增大,标准化强度不断下降。随着冲击方式的改变,材料首次冲击的损伤增加,第2次和第3次冲击下材料峰值应力下降速度提高。 相似文献