Papers by Keyword: Crack

Abstract: The embedded temperature and acoustic emission sensors were used for monitoring thermal gradient and crack development of the concrete in a large foundation. The results show that the vertical thermal gradient is obvious, while the transverse is relatively stable during 3 and 8 days, and when the peak temperature is reached at the third day after the concrete was cast, the crack development is most intense. Therefore, measures should be mainly taken to care the concrete, especially at the peak temperature.

Abstract: Huatugou in Qaidam Basin is a saline soil area with special geological condition, and there has special climatic conditions. The buildings appear serious cracks and inclined in this area. This article uses the investigation and inspection which we collect to analyze the present situation for the buildings. Explain why this situation happened and put forward some treatments.

Abstract: Cracks provide diffusion path for chloride ions transport from the external environment into the concrete, resulting in the durability degradation of concrete structures. In this paper, the boundary condition of cracked concrete and chloride diffusion coefficient in crack were analyzed. The time-dependent chloride diffusion model was established based on the time-dependent chloride diffusion coefficient and the Ficks second law of diffusion. The influence of crack on the concentration distribution of chloride ion in cracked concrete was quantificationally investigated.

Abstract: According to the quasi static test of reinforced concrete frame with construction joints in, the fracture crack sequence, fracture morphology and plastic hinge are studied in detail. Research shows that two kinds processing method of construction joint will not affect the destruction form of a frame structure, but destruction order .

Abstract: Discrete element model of fully sintering dental zirconia was constructed and calibrated. Based on the model, the dynamic process of low-speed milling of zirconia was simulated, and the effects of different cutting speeds, cutting widths and federates on the formation of surface cracks were also analyzed. Results show that residue cracks number and maximum depth increases significantly with increase of the cutting width, while the influence of cutting speed and federates is not distinct. That shows the possibility of high-speed machining on fully sintering dental zirconia with development of coating technology of cutting tool.

Abstract: Fatigue tests on lead zirconate titanate (PZT) were performed by using single-edge-V-notched specimens under cyclic mechanical loading with or without superposition of a DC electric field. Fatigue life was prolonged by applying a DC electric field to the PZT ceramics. To estimate the domain contribution, fatigue tests on barium strontium titanate (BST) ceramics in both ferroelectric and paraelectric phase were carried out. The fatigue life of the ferroelectric phase was much shorter than that of the paraelectric phase. Comparing the fatigue lives of two PZT ceramics with different values of coercive electric field (E_c) revealed that the fatigue life of the PZT with higher E_c is about one order of magnitude longer than that with lower E_c when the stress-intensity factor of fatigue test is low. It is therefore concluded that non-180°domain switching probably deteriorates the fatigue life of ferroelectric ceramics.

Abstract: The pipelines distribute extensively in China, but pipelines cracks caused pipeline damaged frequently. Once the pipeline’s cracks are considered in the seismic condition, the performance of pipelines will face many problems. The finite element method was used to analyze the seismic responses of pipeline’s cracks. According to fracture mechanics [1], the time-history responses of displacement, acceleration and stress of pipeline with crack defects and seamless pipeline were obtained, and the results were also compared and analyzed. The results indicate that cracks will cause the stress concentration of the pipeline, the pipeline cracks should be considered in seismic responses of pipelines to make the pipelines in safety and economy, and more attention should be paid to the design and study of pipelines with crack defects.

Abstract: This paper is mainly based on the basic principle of the extended finite element ,in the large commercial software abaqus on the platform of dynamic load eccentric mixed-mode of concrete failure process are numerically simulated, the results showed that the crack together under tension and shear ,crack extension direction and the direction of cracks was obvious deflection, and is in good agreement with the physical experiments, also shows that the extended finite element fracture problems have very good advantage.

Abstract: The use of Hilbert-Huang transform (Hilbert-Huang transform, HHT) on crack AE signal study, through empirical mode decomposition (empirical mode decomposition, EMD) AE signal is decompose into a number of intrinsic mode functions (Intrinsic mode Function, IMF), Hilbert spectrum and Hilbert marginal spectrum are calculated. The results show that crack depth structure bearing of acoustic emission are detected accurately by the number of acoustic emission events, time and crack the degree from Hilbert spectrum and Hilbert marginal spectrum.

Abstract: In this paper, the effect of a centrally located cutout (circular and elliptical) and cracksemanating from the cutout on the free flexural vibration behaviour of functionally graded materialplates in thermal environment is studied. The discontinuity surface is represented independent of themesh by exploiting the partition of unity method framework. A Heaviside function is used to capturethe jump in the displacement across the discontinuity surface and asymptotic branch functions areused to capture the singularity around the crack tip. An enriched shear flexible 4-noded quadrilateralelement is used for the spatial discretization. The properties are assumed to vary only in the thicknessdirection. The effective properties of the functionally graded material are estimated using the Mori-Tanaka homogenization scheme and the plate kinematics is based on the first order shear deformationtheory. The influence of the plate geometry, the geometry of the cutout, the crack length, the thermalgradient and the boundary conditions on the free flexural vibration is numerically studied.