To enhance the mining efficiency of hard-to-extract coal seams, this study proposes a novel coal pre-fracturing technique using high-pressure water injection through boreholes. Theoretical models and finite element simulations were established to analyze the fracturing mechanics and compare the efficacy of straight versus inclined boreholes. An experimental system was subsequently designed to validate the cutting performance of pre-split coal walls against non-pre-split counterparts. The key findings demonstrate the superior performance of inclined boreholes in pre-splitting, which produced higher peaks in equivalent stress (25
This paper presents an innovative framework for generating artificial neural networks to predict dynamic stresses in steel truss bridges under multiple-vehicle loading. A finite element model of the bridge is established and updated using test data through a response surface method. The generated dynamic stress datasets are used to train an artificial neural network to predict dynamic stresses in the bridge under an arbitrary single vehicle. Finally, given the dynamic stresses under a single vehicle, those under multiple vehicles are determined by superposition. The results indicate that the correlation coefficient and root-mean-square error of the predicted dynamic stress at the critical joint of a steel truss bridge are 0.993 and 0.74, respectively. The artificial neural network provides an accurate prediction of dynamic stress in the bridge under single-vehicle loading. This research develops a promising tool for efficiently predicting dynamic stresses in bridges.
The challenge of improving the strength properties of materials used in the manufacture of modern machine parts and industrial equipment prompts a search for solutions. The development and creation of new materials require long-term research and significant financial and technological investments. However, modifying widely used, well-known industrial materials to meet specific industrial needs is a far more promising approach to solving this problem. One of the main approaches to improving the physical and mechanical properties—specifically, strength and wear resistance—of parts and structural elements made from such materials is treating the working surfaces of these products with specific physical fields, namely high-temperature diffusion gas-ion environments. This paper examines the effect of various concentrations and compositions of high-temperature gas media, as a corrosive factor, on the deformation behavior of molybdenum. A study was conducted to assess the effect of high-temperature gas media (argon, ammonia, nitrogen-hydrogen, and nitrogen-hydrogen-ammonia mixtures) on the short-term creep behavior of specimens of chemically pure molybdenum under linear-stress conditions. The results of these studies on such effects on its creep behavior were analyzed. In a first approximation, an analytical relationship was derived to approximate molybdenum creep curves in a high-temperature, aggressive gas environment as a function of the percentage composition of its components.
The results of static and cyclic hydraulic tests of a pilot batch of cylinders are presented, along with an assessment of the evolution of the metal’s structural state during loading using coercivity-based control. Significant differences were found in the kinetics of the anisotropy coefficient of the metal’s structural state—as determined by coercivity monitoring—relative to the load during elastic and plastic deformation, which are associated with the formation of residual stresses. The initial state and elastic deformation together constitute a stable structural configuration that accounts for these patterns. The onset of plastic deformation causes an abrupt shift of 36
This study addresses the problem of improving the efficiency of fine grinding of basalt raw materials and industrial waste with the aim of extracting the silicate component for the production of construction materials. The aim of the study is to experimentally determine the influence of the clearance in unilateral elastic couplings and the degree of chamber filling with grinding media on the degree of grinding in a vibroimpact multi-frequency mill. The study was conducted using a full factorial experiment and analysis of variance for basalt raw material with a particle size of up to 10 mm. Dependencies were established between the mill’s operating parameters and the particle size distribution of the ground products. It was shown that optimal filling degree values range from 0.82 to 0.93, and the maximum degree of grinding is achieved at a gap of 3.0 mm. A statistically significant influence of the studied factors was revealed, among which the gap in the elastic bonds plays a dominant role. The results obtained allow for the rational determination of optimal parameters for vibroimpact mills, improving the efficiency of raw material processing and reducing energy consumption. Experimental studies were conducted on the properties of a cement-sand mixture (CSM) with the addition of mechanically activated fly ash from thermal power plants. The preparatory stage involved mechanically screening the fly ash on an MVG multi-frequency screen to obtain a minus 40 μm fraction. Mechanically activated fly ash was produced by grinding the minus 40 μm fraction in a vibrating mill chamber with multi-frequency vibroimpact excitation. Mechanical activation of the 40 μm fraction was carried out under two time regimes: 15-minute and 30-minute activation periods. The storage time of the mechanically activated fly ash prior to specimen preparation was also varied. To determine the optimal fly ash content, the percentage of fly ash added to the mixture was varied. The highest strength of the specimens was observed at a 10
