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Low velocity zone of upper mantle and its effect on PdSwr phase related to 670 kmdiscontinuity
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作者 魏东平 周蕙兰 王志秋 《Acta Seismologica Sinica(English Edition)》 CSCD 2000年第1期67-74,共8页
This paper studied some properties of PdSwr phase related to 670 km discontinuities in detail, and theoretically processed a preliminary analysis to this phase. We discussed the relationships between the incident angl... This paper studied some properties of PdSwr phase related to 670 km discontinuities in detail, and theoretically processed a preliminary analysis to this phase. We discussed the relationships between the incident angle ih of PdSwr phase with its path, epicentral distance, travel-time and relative amplitude due to low velocity zone (LVZ) of upper mantle, and preliminarily pointed out the main characters of PdSwr phase recorded in seismogram. The PdSwr phase is concentrated in range of 13.5~96.5. When epicentral distance is greater than 33, the start point of PdSwr phase is relatively well distinguishable and could thus be determined more easily. When the epicentral distance is between 13.5 to 33, the triplication of PdSwr's travel-time curve could be slightly distinguished due to the low velocity zone and 220 km seismic velocity discontirluity of upper mantle. The relevant observed PdSwr phase should be in a more complex pattern and it should be more difficult to determine its start point 展开更多
关键词 low velocity zone discontinuity incident angle of seismic ray TRAVEL-TIME epicentral distance
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A DUCTILE FRACTURE CRITERION BASED ON THREEDIMENSIONAL VOID MODEL 被引量:1
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作者 J.K. Huang X.H. Dong 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2008年第3期227-234,共8页
A fracture criterion derived from a microscopic point of view is proposed and has proved to be effective in the analysis of uniaxial tension. On the one hand, a method of predicting a ductile fracture is proposed usin... A fracture criterion derived from a microscopic point of view is proposed and has proved to be effective in the analysis of uniaxial tension. On the one hand, a method of predicting a ductile fracture is proposed using a three-dimensional void model and the assumption of velocity discontinuity. The relationship between the void volume fraction and the critical strain to fracture, calculated with the help of the new model, shows the same tendency as that obtained from the modified Thomason model. On the other hand, the mechanical and metallographic analyses of the uniaxial tension experiment are performed using four kinds of carbon steel. The relationship between the void volume fraction and the critical strain to fracture, calculated from the new model, agrees better with the result obtained from the experiment, rather than that calculated by the modified Thomason model, which confirms the validity of the ductile fracture criterion based on the three-dimensional void model. 展开更多
关键词 Fracture criterion Uniaxial tension velocity discontinuity Mechanical and metallographic analyses
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