Experimental Study on Mechanical Properties, Failure Behavior and Energy Evolution of Different Coal-Rock Combined Specimens

To investigate the effect of the pure coal/rock strength on the mechanical behavior, failure behavior, and energy evolution of coal-rock combined (CRC) specimens, an AG-X250 Shimadzu Precision Universal Test was used to conduct uniaxial compressive loading, uniaxial cyclic loading, and unloading compression experiments on pure coal, pure rock, and different CRC specimens. The results show that the uniaxial compressive strength, Young’s modulus, and peak strain of the CRC specimen mainly depend on the coal specimen instead of the rock strength. The major failure modes of CRC were the shearing fracture and axial splitting failure, and for the CRC specimen with the same hard rock, the CRC specimen severely failed due to axial splitting cracks. In addition, the released elastic energy Ue, dissipated energy Ud, and kinetic energy Ur increase with increasing rock mass/coal strength, and for CRC specimen with the same coal, the greater the difference in strength between the rock and coal is, the greater the kinetic energy is

Study on Thermal Energy Conversion Theory in Drilling Process of Coal and Rock Mass with Different Stresses

In view of the problem that the evolutionary mechanism of bit temperature during the drilling process is still unclear and the influencing factors are complex, this paper analyzes the causes of heat generation and the factors of heat production when the drill bit interacts with the coal and rock mass. Considering the stress field distribution of coal and rock mass and the dynamic characteristics of drilling, a three-dimensional mechanical structure model of bit drilling is established in this paper, based on the energy conservation theory and introducing the friction heat micro-distribution mechanism. The corresponding relationship between coal stress and the bit temperature variation rate is obtained in this paper. Therefore, the temperature rise condition model and the coal stress identification model can be verified, combined with the existing experimental data. The result shows that the temperature of bit drilling is affected by factors such as bit geometry and drilling parameters, as well as the strength and stress state of the coal and rock. Without considering other factors, the rate of increase in bit temperature is proportional to the stress of the coal and rock mass. Based on the research results, the temperature rate of the drill bit can be used as an index to identify the stress areas of coal and rock mass. Research results provide a theoretical basis for the identification of high-stress risk areas in coal mines

Recent progress in research on bonding technologies of W/Cu monoblocks as the divertor for nuclear fusion reactors

Divertor components with excellent comprehensive performance are a new research focus for nuclear fusion reactors. However, the excessive mismatch in the coefficient of thermal expansion (CTE) between W and Cu poses a challenge for their application in the divertor. This paper provides a review of the recent progress in the bonding technologies of W/Cu monoblocks, where the W/Cu monoblock refers to any monoblock assembly with a direct W to Cu interface. The bonding technologies of W/Cu monoblocks with bonding interface materials (brazing and diffusion bonding) and W/Cu monoblocks with bonding interface structures (surface nanosizing technologies of W, coating, and explosive welding) are described in detail. The advantages and limitations of each technology are commented upon. Furthermore, the preparation of W/Cu monoblocks with a W-Cu gradient interlayer and W-Cu functionally graded materials (W-Cu FGMs) with full composition distribution is reviewed. These approaches aim to improve the performance of the W/Cu monoblocks. The mechanical, high heat flux (HHF) resistance, and irradiation resistance performance of the W/Cu monoblocks are summarized and evaluated. These performances are crucial for the successful application of W/Cu monoblocks in the divertor. Finally, based on the comprehensive review, future developments and potential research challenges for W/Cu monoblocks are proposed. This provides insights into the direction of future research in this field