矿岩接触带充填体早期承载特性试验研究

为研究胶结充填体早期强度时的矿岩接触带力学作用机理,根据不同充填体情况下的矿房矿柱受力特点简化了相应的力学模型,分析矿岩顶板和矿柱的力学作用机理并进行了相关的模拟实验。选用没有强度的橡皮泥作为早期强度的胶结充填体,通过电阻应变仪对接触带内置电阻应变片和表壁粘贴电阻应变片的应变值进行比较,分析在不断加载过程中接触带及各处的应变变化情况,同时进行数值模拟的相关验证工作。结果表明,在荷载作用下接触带处拉压应力发生突变,挤压造成充填体内部向中心区域挤压。     

Flow behavior of Plasticine used in physical modeling of metal forming processes

In this study, compression tests were conducted to determine the flow behavior of various types of Plasticine. True stress–true strain relations are presented in the form of a well-known power law equation. It is shown that the strength coefficient and the strain hardening exponent vary significantly among the Plasticine with different colors commercially available. Furthermore, since three dimensional simulations require arranging slabs of alternating colors to form a grid pattern, two different colors, exhibiting similar flow characteristics, are identified. The flow behavior of the composite model is usually not the same as that of the individual colors. The results presented in this paper allow selection of the type of Plasticine which most closely resembles the strain hardening characteristic of the actual metal, thereby satisfying the “similarity condition” of the Physical Modeling Technique.     

Physical modeling of equal channel angular pressing using plasticine

We report here the results of our physical modeling study of the equal channel angular pressing process using two-colour constituent plasticine workpieces in a metallic die. The workpieces, usually called billets, are made up of discs as well as spherical balls. They are deformed repeatedly with and without changing the orientation between successive passes. Both square and round dies with inner channel intersection angle of 90° are used. The flow patterns are revealed by sectioning the billet after a requisite number of passes. Thorough mixing of the two constituents with a drastic reduction in the section size of each constituent of the plasticine workpiece was observed after 15 passes. The initial shape of the constituents of the billet does not affect the final flow pattern of the microstructure. Material accumulation of the two colour constituents of plasticine was observed in some regions of the billet along the central region at a low and intermediate number of passes.