Papers by Keyword: Crack

Abstract: In this study, crack propagation in PPS thrust bearings under rolling contact fatigue (RCF) in water was observed, and relation between subsurface crack and internal shear stress parallel to the surface was investigated. It was found the cause of flaking was subsurface crack. They were evaluated in terms of contact stress and friction between their faces. It was discovered that subsurface cracks distributed around shear stress peak, and flaking failure was dominated by subsurface shear stress.

Abstract: Reinforced corbels are frequently used in industrial halls. A number of existing corbels are prestressed by unbonded tendons or bars in order to increase their load-bearing capacity, decrease the deflections and restrain cracks spreading. The goal of the project was experimental validation of the reinforced concrete corbel strengthened using unbonded tendons via CSFM (Compatible Stress Field Method). The method is based on materially nonlinear calculation considering the tension stiffening effect of rebars and compression softening of concrete. These effects and other assumptions implemented in CSFM capture real behavior of reinforced concrete members. Besides, CSFM is verified using an independent analysis, which is based on similar assumptions as those in Compatible Stress Field Method.

Abstract: In this study, Na₂CO₃ solution as a self-healing agent was impregnated in LWA for autonomic self-healing on cracked cementitious material. The results showed that under the joint action of expansive agent, crystalline additive, phosphate and carbonate, the crack area showed a high self-healing efficiency (close to 70%) after curing in the still water 28d. SEM-EDS test results showed that in addition to ettringite and C-S-H/C-A-S-H, there was also a large amount of CaCO₃ crystal in the depths of the crack.

Abstract: TP321 stainless steel is widely used in hydrogenation refining pipes owing to its excellent performance of creep stress resistance and high-temperature resistance. In this study, thermal simulation tests were carried out on the welding heat-affected zone (HAZ) of TP321 stainless steel at temperatures of 1300 °C, 1100 °C, and 850°C using a Gleeble 3800 testing machine. Slow strain tensile tests were conducted under the condition of electrolytic hydrogen charging (EHC) and the metallographic microstructure of cracks as well as the morphology of fractures were analyzed in detail. The result shows that hydrogen can change the fracture mode of tensile specimen and the cracks initiated from and near the specimen surface after EHC. Hydrogen significantly decreases the plastic deformation capability of HAZ in TP321 stainless steel. The reduction of area after the fracture decreases by 58%, 41%, and 45% for HAZ at 1300 °C, 1100 °C, and 850 °C, respectively. The existence of δ ferrite was considered to be the main reason for the aggravation of hydrogen-induced plasticity loss.

Abstract: This paper attempts to investigate the fracture toughness of the cracked concrete repaired by polymethyl methacrylate (PMMA) - a thermo-plastic polymer resin. A single-edged notch beam in three-point bending test was conducted to examine the performance of cracked concrete beam after reparation. Three concrete crack widths of 1 mm, 5 mm, 10 mm were designated to be repaired and examed. The fracture properties include critical stress intensity factor K_IC by Jenq and Shah and fracture energy G_F by Hillerburg, were evaluated for the concrete before cracking and after reparation. Four sand contents of 0%, 10%, 20% and 40% by volume were used in the PMMA mortars. From the testing results, it appears that the load capacity and fracture toughness of repaired concrete increased with the increasing sand content. And, the PMMA mortar made repaired concrete better strength and fracture toughness as well.

Abstract: The purpose of this study is to explore the forms and characteristics of reflection crack in asphalt overlay of old cement pavement, so as to provide reference for effective prevention and treatment of reflection crack.By means of ANSYS finite element software, considering the coupling effect of temperature and vehicle in different working conditions, the influence of cooling on asphalt overlay was analyzed, and the location and form of crack were discussed.The analysis results show that tensile crack and shear crack are more likely to occur near the joint of old cement pavement, and shear crack is more likely to occur in areas outside the joint, about 1/2 wheel length from the joint of cement pavement.The prevention and treatment of crack at different locations should be carried out according to different working conditions.

Abstract: The contribution focuses on the effect of selected input parameters on probabilistic estimation of chloride induced reinforced concrete bridge deck corrosion initiation. The reinforced concrete bridge deck with steel protected by epoxy-coating is considered. A finite element diffusion model in conjunction with a probabilistic method using Monte Carlo technique is used to address the inherited randomness of input variables. Presented parametric study shows the sensitivity of estimation of the corrosion initiation likelihood on variation of input parameters.

Abstract: In this article, molecular dynamics simulations have been performed to study the effect of crack on the tensile strength of a bicrystal of Zr. Bicrystal with a symmetric tilt grain boundary, with crack and without crack, are generated along [0001] tilt axis. This is further subjected to tensile loading and the stress strain response of the bicrystals with and without crack is studied. The strength of the bicrystal with crack is lower than the one without crack.

Abstract: The receiving of plain problem by analytical appearance with horizontal edges on the endless layer of propagation of the vertical crack and the dependence of the inner pressure of crack is observed. It supposed that the bottom edge of the layer is fixed to absolutely hard semi-flatness, but the upper edge is free. In this respect, we have tried to get the propagation measure of the opening and the analytical aspect of pressure change dependence acting inside it, by method of local modifications using the received solutions. The corresponding methods of approximate illustration of functional dependence are used. In the environment of the opening and the received measure of crack propagation the analytical expressions of distribution of stresses give the full image of peculiarities of those dependences for that immeasurable domain and correspond to the received results by method of modifications. The received formulas may be applied by solving concrete applicable problems and in studies of opportunities of cracks’ propagation for environment of fragile material. Those opportunities are increasing moreover if we take into account that the solutions are received for immeasurable environment.

Abstract: The problem of stress state of an elastic piecewise-homogeneous wedge-shaped body at an antiplane deformation, consisting of heterogeneous wedges with different shear modules and opening of apex angles is considered, when a system of arbitrary finite number of collinear cracks is located on the interface line of the heterogeneous materials and the boundary faces of the compound wedge are reinforced with stringers of finite lengths. The solution of the problem is reduced to solving a system of three singular integral equations (SIE) using the Mellin integral transform, which based on quadrature formulas Gauss for calculating SIE with Cauchy kernel and ordinary integrals reduces to a system of systems of linear algebraic equations (SLAE). As a result, the characteristics of the problem are expressed by explicit simple structures algebraic formulas.