Papers by Keyword: Damage Characteristics

Abstract: Metallic glasses (MGs) exhibit extremely high strength and superior resistance to corrosion. They are also supposed to be resistant against displacive irradiation due to their inherent disordered structure, and thereby are viewed as potential candidates for applications in irradiation environments. However, the structures and properties evolution of metallic glasses, especially bulk metallic glasses (BMGs), under irradiation has not been fully understood up to now. In this work, the structural stability and damage characteristics of a Zr-based BMG under helium ions irradiation environment were investigated. Meanwhile, the effect of structural relaxation and crystallization on the irradiation response of the BMG was also studied. Results show that the BMG reserves the amorphous structure within the studied range of fluence, and exhibits better irradiation resistance compared to that of the crystalline alloys. In our opinion, the initial free volume concentration affects the damage morphology of the BMG, while partial crystallization will lead to significantly embrittlement under irradiation.

Abstract: For the purpose of research on behavior of argillaceous dolomite suffering from frequent cryogenic freezing weather in Guizhou region, the rock was processed into cylinder samples (diameter 50mm&height 100mm). Using BCD-218 cryogenic digital control equipment, in saturated state, the samples were frozen (-20°C) and thawed (20°C), each 12 hours for one cycle, total 30 times. Then, Longitudinal wave velocity (LWV), macroscale and mass varying with freezing-thawing cycles were respectively tested by RS-ST01C nonmetal supersonic test meter, vernier caliper (0.02mm), APT457A electronic balance (0.01g). Also, appearance characteristics were observed constantly. Lastly, the micro reason for changes in macro parameters of the rock was explained. The results show that the freezing-thawing deterioration form of argillaceous dolomite is spallation mode, and LWV decreases obviously with the increase of freezing-thawing cycles (FTC),maximum drop of 14.8%,while mass has a small increase, maximum change rate of 0.5%. Macroscopic properties are obviously affected by freezing and thawing cycles. Key words: argillaceous dolomite, freezing-thawing cycles, supersonic detection, damage characteristics

Abstract: The dynamic Davidenkov model is used to model dynamic characteristics of soils, and plastic-damage model is used to model dynamic characteristics of station structure concrete. So that, considering the influence of soil-station structure interaction for 2D finite element analysis, the dynamic interaction of soil-station structure is modeled. The damage characteristics and energy response of station structure under seismic motion is analyzed. The result shows that damping energy and hysteretic energy are monotone increasing under ground motion, and the seismic characteristic has significant effect on the energy response of subway station structure. Furthermore, concentration effect of hysteretic energy of subway station structure is measured by hysteretic energy density. It is found that the hysteretic energy is the most centralized in the column, so the dynamic response of the columns is the maximum. Furthermore, the nonlinear damage evolution law of station structure is analyzed. The law of local and global damage index is consistent essentially, and the damage index is increased by the effect of accumulative deformation.

Abstract: Unstable rock is the typical geological disaster in areas of highway, city and mine. Energy from rupture of unstable rock passes around by excitation wave, which produces significant excitation effect to adjacent unstable rock, and which is one of important reasons to cause the cascading collapse. By the method of wave mechanics calculation equation of peak velocity from unstable rock caused by rest energy through interface between unstable rocks was deduced and established. Based on the rule of Sweden and Canmet, authors proposed damage criteria of unstable rock under excitation effect. According to damage mechanics, authors set up estimation method of microcrack being likely activated to rest unstable rock under excitation effect. Example analysis shows that problem considering excitation damage is an important way of promoting the scientific and transient security analysis of unstable rock. Research results have a positive significance for science reveals of unstable rock failure mechanism.

Abstract: A total of 18 specimens’ damage processes of concrete under split load in 1d, 3d, 5d, 7d, 14d and 28d ages are monitored by acoustic emission (AE) technique and corresponding typical AE characteristics are summarized. The results show that splitting tensile strength of concrete and the number of AE hits are both showing a gradual increase with the growth of age. During the process of splitting failure of concrete specimens in 14d and 28d, AE hits in higher duration and amplitude are collected, It shows that the older concretes tends to release more energy, at last, AE parameters which are in higher correlation with the development of mechanical properties for early age concrete are given. Related research conclusions can provide the foundation for the research of strength development and damage mechanism of early age concretes.

Abstract: In this work the fracture process of steel honeycomb sandwich beams has been investigate by situ acoustic emission(AE) technique. Pre-cracks were made both for L-direction and W-direction specimens subjected to out-plane three-points bending loads. Damage initiation sites were observed in the vicinity of the crack tip. A series of curves among the AE counts, AE hits, AE amplitude, AE energy and loading time were obtained. Damage characteristics were discussed based on the above parameters. The results indicate AE characteristic parameters can reflect the damage and failure process of specimens. A good agreement was found between the experimental and analytical results.