Experimental study of the destruction in CFRP laminates at the macro-level by acoustic emission method

The author conducted experiments using the method of acoustic emission under uniaxial tension of specimens of CFRP laminates with different stacking, geometry and stress concentration. The influence of a mutual arrangement of the material destruction zone and the extensometer installation site on the nonlinear deformation is revealed. It is shown that the damage accumulation process is highly informative when determining the energy of AE pulses. The possibility of visualizing the formation and development of destruction zones in orthogonal directions, as well as the possibility of determining the moment of crack start from the apex of the notch during splitting, is established. The mechanism of alternating stress relaxation in two developed zones of destruction is revealed. The paper shows a high degree of correlation between mechanic and acoustic-emission events. Finally, the author suggests assessing the mechanical state of material with the account of obtained damages by the degree of its integrity (one to zero) depending on the load history, its individual geometric features and stress concentration.

Determination of the Extent of the Rock Destruction Zones around a Gasification Channel on the Basis of Strength Tests of Sandstone and Claystone Samples Heated at High Temperatures up to 1200 °C and Exposed to Water

This article presents the results of laboratory tests regarding the influence of high temperatures on changes in the strength and structural parameters of rocks that are present in the immediate vicinity of a gasification channel. Sandstone and claystone samples were heated at 300 °C, 600 °C, 900 °C and 1200 °C. Additionally, the heated samples were placed in water for 24 h. The results of the laboratory tests were used in the numerical simulation using RS2 software. The main goal of modeling was to determine the extent of the rock destruction zone around the gasification channel for dry and wet rock masses. In the numerical simulations, three widths of the gasification channel and three ranges of high-temperature impact were modeled. On the basis of the obtained results, it was found that the extent of rock destruction, both in the roof and in the floor, is greater by several percent for a wet rock mass. For the first time, this research presents the effect of water on heated rock samples in terms of the underground coal gasification process. The results of laboratory tests and numerical simulations clearly indicate a reduction in strength, deformation and structural parameters for the temperature of 1200 °C.

STUDIES OF THE SHAPED CHARGES EFFECT WITH A HEMISPHERICAL ECCENTRIC SHAPE RECESS FOR THE ROCKS DESTRUCTION

The method of outdoor installation of explosive charges is usually used in the destruction of rocks in conditions in which the method of drilling and blasting using borehole or borehole charges is difficult to apply due to objective conditions. The productivity of rock destruction by the outdoor installation of a concentrated charge is very low. This is due to the fact that such an explosion is characterized by a large loss of energy in the environment. The destruction of rocks by an explosion using shaped charges (CW) to destroy the rock is one solution to increase the useful energy of the destruction of the rock compared to charges placed outside. To achieve the optimal effect of destruction of the rock by cumulative charges, it is necessary to, so that for each type of rock, a specific type of shaped charges can be determined with the appropriate performance and efficiency of the use of explosives. The stronger the rock, the more efficient the short-circuit should be, and vice versa. Thus, for effective rock crushing, it is necessary to develop and produce a number of different types of shaped charges. The use of shaped explosive charges allows you to increase the utilization rate of the useful energy of the explosion and increase the destruction zone of the rock. At a fixed mass of the explosive, the destructive effect of the explosive charge placed on the surface of the rock, it depends on the shape of the charge and the geometric parameters of the charge. Shaped charges with an eccentric hemispherical shape have a coefficient of use of the useful energy of the explosion for the destruction of rock, more than 2.4 times compared to conventional concentrated charges of the same mass.

Determination of the regularities of the soil punching process by the working body with the asymetric tip

The presence of analytical dependencies describing the process of static soil puncture by a working body with a conical asymmetric tip is necessary to create installations with the ability to control the trajectory of the soil puncture. The paper considers the features of the process of interaction of an asymmetric conical tip with the ground. Analytical relationships were obtained to determine its reactions during a static puncture, the deviation of the head trajectory from a straight line, to determine the size of the soil compaction zone and the magnitude of the destructive force that acts on adjacent communications and other underground objects. It was found that with an increase in the value of the displacement of the top of the cone, for example, from its axis from 0.02 m to 0.08 m with a borehole diameter of 0.2 m, the value of soil resistance increases almost four times. The greatest resistance is achieved when piercing a hard sandy sand. It was found that with an increase in the displacement of the tip of the tip cone, the deviation of the trajectory increases. The piercing head achieves the greatest deviation from the straight trajectory of movement with a sharper cone and a greater asymmetric deviation of its top, and, for example, in hard sandy loam can be up to 0.17 m with a span of 10 m. It was found that the size of the soil destruction zone will be almost 1.8 times larger than the tip in the form of a symmetrical cone and reaches from 8 to 12 borehole diameters, depending on the type of soil. The maximum pressure on adjacent objects can reach from 0.06 MPa in hard-plastic clay to 0.09 MPa in hard sandy loam. The calculated dependences obtained for determining the power and technological parameters depending on the geometric dimensions of the asymmetric tip of the working body can be used to create installations with a controlled static puncture for use in the most common soil conditions.

Dental Implant Site Drilling and Induced Morphological Changes Correlated with Temperature in Pig’s Rib Used as the Human Jaw Model

The bone tissue destruction during drilling is still one of the crucial problems in implantology. In this study, the influence of drilling speed, coolant presence, and its temperature on bone tissue was tested using swine rib as a biological model of human jaws. The same method of drilling (with or without coolant) was used in all tested samples. The microscopic investigation estimated the size of the destruction zone and morphology of bone tissue surrounding the drilling canal. The achieved results were statistically elaborated. The study proved that the optimal drilling speed was ca. 1200 rpm, but the temperature of the used coolant had no significant influence on provoked bone destruction. Simultaneously, the drilling system without coolant compared to this with coolant has statistical importance on drilling results. Further in vivo studies will verify the obtained results.

Thermal and shock-wave effects of HIFU - effects on tissue-equivalent phantoms

The nature of changes in the structure of the PAG-3 biophantome under the action of HIFU indicates the significance of shock-wave shifts involved in the formation of the heat pattern and the destruction zone. The thermal effect is accompanied by the accumulation of thermal energy, the limitation of the thermal field, which predetermines the therapeutic efficiency of focused ultrasound exposure, however, it is advisable to take into account the role of mechanical effects in focused ultrasound therapy.

Correlation between the material constitution components in apatite-nepheline ores of the Khybiny Rock Massif (the Kola Peninsula)

Raw apatite-nepheline ores of the Khibiny alkaline massif are similar in terms of the set of ore-forming minerals and differ in their quantitative ratio. A special place among apatite-nepheline ores is occupied by ores of tectonically destroyed zones, which are widespread in the Khibiny apatite-nepheline deposits. Destruction zone ores are product of secondary changes in raw ores and are characterized by the presence of finely dispersed secondary minerals represented by hydrated micas, zeolites and clay minerals. In the aquatic environment they form colloidal sediments with active surface properties. This fact, as well as thin films of clay and other minerals formed on the surface of apatite grains, cause a decrease in the degree of hydrophobicity of fluorapatite and deterioration of the selectivity of apatite flotation. According to the analytical determinations of the chemical components of the ores and their mineralogical composition, a correlation-regression analysis of the ratio of the components of the material composition of the ores has been performed. The results of correlation-regression analysis have shown that the presence of hypergenically changed ores related to difficult-to-treat ones can be identified by lower ratios of sodium and potassium oxides, as well as sodium and aluminum relative to their average. The presence of products of nepheline change in all ores processed has allowed revealing the most stable correlation between nepheline and sodium oxide, rather than aluminum oxides, in contrast to the earlier opinion. The very high correlation relationship between fluorapatite, nepheline, and titanite and the oxides of phosphorus, sodium, and titanium, respectively, and the statistical significance of the correlation and regression coefficients allow determining the content of these minerals using the regression equations presented in the paper.

The Influence of Room and Pillar Method Geometry on the Deposit Utilization Rate and Rock Bolt Load

In this article, a model of ore deposit in form of a lense carried out in the MineScape program, is presented. The lense had a thickness of 30 m, length along the strike 200 m, and the depth buried was for 80 m to 110 m below the surface. In the first layer, counting from the lowest level, a room and pillar method with variable geometry was designed. The width and length dimensions for rooms and pillars were: 4 m, 5 m and 6 m, respectively. For the selected part of the deposit, three variants of the system with variable geometry of rooms and pillars were designed, for which the deposit utilization coefficient was determined. The next stage of the research was to determine the influence of the geometry of the pillars and rooms on the range of the rock destruction zone around room excavations. For this purpose, numerical calculations using the three-dimensional Examine 3D program, based on the boundary element method, were made. The results of numerical tests were used to calculate the load of the rock bolt support, which is currently used in the zinc and lead underground mine “Olkusz-Pomorzany” in Poland. Currently in the mine, the bolt spacing is 1 m × 1 m, and the technology for fixing the bolt rod is based on resin cartridges that completely fill the bolt hole. In order to spread the spacing of the rock bolt support and to apply segmental fixing of the bolt rod, in the laboratory tests, rock bolt supports with increased strength were tested. Based on the results obtained, it was found that the rock bolt can be installed segmentally, using a cement grout, and its spacing can be increased to 2 m.