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The volume of trees and branches grown in Uzbekistan is increasing year by year. Foreign experiences on processing and use of antlers are analyzed. According to the analysis, it became known that in recent years the volume of bushy tree branches in our republic has increased by 2-3 times, and there is a need to prepare and use various products from the branches. Taking this into account, in our country, creation of the bushy tree branch crushing apparatus, one of the crucial jobs is the construction plan and the technological work method. Based on this, the number of rotations of the screw of the crushing device was studied. Researches were carried out by changing the number of revolutions of the screw or auger of the grinding machine from 800 r/min to 1200 r/min. When the number of revolutions of the grinding screw is 1000 r/min, the amount of small fractions in the content of crushed branches and the smallest amount of indestructibility was achieved, and it was found that the quality of crushing branches has an acceptable value.

The discrete element method (DEM) is used widely to study the crushing behaviour of granular materials from a microscale perspective. However, a crushing criterion that can be suitable for triggering particle crushing for different coordination numbers (CNs) is still lacking. To develop a crushing criterion, particle crushing tests are conducted for different CNs via the DEM. Crushable spherical agglomerates are made by bonding smaller sub-spheres. Based on the results of simulations, a new crushing criterion invariant to the coordination number effect is proposed. The crushing criterion is simply expressed in terms of the three principal stresses of the particles. Furthermore, the applicability of the criterion is verified under various conditions, such as different numbers of sub-sphere, shapes of particles, microscale parameters and loading patterns. By using the new criterion, the particle strengths obtained from the single particle crushing tests can be used as the crushing strengths for the particles under multiple contact loading conditions in DEM simulations.

The worldwide mining industry consumes a vast amount of energy in reduction of fragment size from mining to mineral processing with an extremely low-energy efficiency, particularly in ore crushing and grinding. Regarding such a situation, this article describes the effects of rock fragmentation by blasting on the energy consumption, productivity, minerals’ recovery, operational costs in the whole size reduction chain from mining to mineral processing, and the sustainability of mining industry. The main factors that influence rock fragmentation are analysed such as explosive, initiator, rock, and energy distribution including blast design, and the models for predicting rock fragmentation are briefly introduced. In addition, two important issues—fines and ore blending—are shortly presented. Furthermore, the feasibility of achieving an optimum fragmentation (satisfied by a minimum cost from drilling-blasting to crushing-grinding, maximum ore recovery ratio, high productivity, and minimum negative impact on safety and environment) is analysed. The analysis indicates that this feasibility is high. Finally, the measures and challenges for achieving optimum fragmentation are discussed.HighlightsThe effects of rock fragmentation on the whole size reduction chain from mining to mineral processing are described.The main factors influencing rock fragmentation by blasting are analysed.Main models for predicting rock fragmentation are briefly introduced and commented on.The feasibility, measures, and challenges of achieving optimum fragmentation are analysed.

The aim of this paper is to evaluate the influence of the crushing process used to obtain recycled concrete aggregates on the performance of concrete made with those aggregates. Two crushing methods were considered: primary crushing, using a jaw crusher, and primary plus secondary crushing (PSC), using a jaw crusher followed by a hammer mill. Besides natural aggregates (NA), these two processes were also used to crush three types of concrete made in laboratory (L20, L45 e L65) and three more others from the precast industry (P20, P45 e P65). The coarse natural aggregates were totally replaced by coarse recycled concrete aggregates. The recycled aggregates concrete mixes were compared with reference concrete mixes made using only NA, and the following properties related to the mechanical and durability performance were tested: compressive strength; splitting tensile strength; modulus of elasticity; carbonation resistance; chloride penetration resistance; water absorption by capillarity; water absorption by immersion; and shrinkage. The results show that the PSC process leads to better performances, especially in the durability properties.

Auxetic honeycomb structures are promising metamaterials with outstanding mechanical properties, and can be potentially used in energy absorption applications. In this study, a novel modified re-entrant hybrid auxetic metamaterial inspired by Islamic motif art is designed by integrating four-pointed double re-entrant motifs with symmetric semi-hexagonal unit cells to achieve a high energy absorption capacity (EAC). Theoretical analyses and numerical simulations are performed to examine the dynamic crushing behavior of the four-pointed double re-entrant combined structure (FDRCS). The developed finite element models (FEMs) are validated by the experiments under quasi-static compression. The deformation mode and stress-strain curves are further studied under low, medium, and high crushing velocities. The theoretically predicted plateau stress of the FDRCS under different crushing velocities is consistent with the numerical simulation results. The crushing stress and the EAC of the FDRCS are influenced by the geometric parameters and crushing velocities. The FDRCS exhibits a negative Poisson’s ratio (NPR), owing to the four-point re-entrant structure (RES). Moreover, the specific energy absorption (SEA) of these structures is higher than that of nonauxetic hexagonal and auxetic re-entrant structures, owing to the generation of more plastic hinges that dissipate more energy during dynamic crushing.

The current straw micro-crusher is often utilized within a circular crushing chamber, leading to the formation of a circulation layer that impacts the efficiency of crushing. This study proposes an airfoil crushing chamber to disrupt the circulation layer and modify particle motion characteristics. Based on CFD-DEM analysis with flow field characteristics, motion trajectory, crushing rate, motion speed, and force magnitude as evaluation indices, the crushing performance and flow field distribution of both chamber types are compared. Test results indicate that the airfoil crushing chamber outperforms the circular one, thereby validating the accuracy of the theoretical and numerical analyses.

It has been found that the physical and mechanical properties of rockfill materials deteriorate when subjected to wetting–drying cycles. Previous studies have mainly focused on the variations of mechanical properties of rockfill materials with wetting–drying cycles. However, the effects of wetting–drying cycles on the breakage characteristics of rock grains still remain unclear. In this study, we perform extensive single grain crushing tests on slate rock grains that have suffered from different wetting–drying cycles. We then investigate the effects of cyclic wetting–drying on the crushing strength, fracture energy, and fragment size distribution of slate rock grains. The results show that both the crushing strength and fracture energy per volume decrease exponentially with increasing wetting–drying cycles, indicating that the deterioration of the mechanical properties of slate grains gradually slows down. The size of fragments follows a fractal distribution, and the fractal dimension shows a linear relationship with the number of wetting–drying cycles, suggesting more small fragments for highly deteriorated rock grains. SEM scanning indicates that the micropores and cracks expand due to wetting–drying cycles. An X-ray diffraction analysis shows that the mineral composition content of slate grains changes after wetting–drying cycles.

To explore the physicochemical characters of barley grass, ultra‐micro‐crushing (UMC) technology combined with air drying or freeze drying was carried out. After barley grass was air‐dried at 70°C or freeze‐dried at 15°C, it was grinded for 30, 60, 90, and 120 min using UMC, respectively. After combined processing, moisture content, particle size, odor, color, microstructure, water and oil‐holding capacity, the content of flavonoid and chlorophyll, water activity, and sensory qualities were determined. The particle size of barley grass powder decreased, and lightness value was increased; water and oil‐holding capacity decreased significantly (p ≤ .05), whereas swelling and dissolving capacity increased in the processed grass powder. On the other hand, the total flavonoid content increased significantly (p ≤ .05). Barley grass odor features sulfide aroma, and its microstructure demonstrates lamellar morphology with some fewer fragmented pieces. The results suggested combined UMC at 90–120 min will be suitable for processing barley grass powder. UMC technology combined with different drying methods has a great progress in the future processing of barley grass powder.

Coal and gas outbursts are small-scale geological disasters controlled by tectonic movement, and tectonic coal is widespread in outburst zones. In this study, we compare tectonic and intact coal specimens to examine the basic properties of tectonic coal. We estimate the different energies and limits of the crushing work ratio of coal from five typical outburst cases using on-site outburst data, and discuss the relationship between outbursts and tectonic coal. The results show that tectonic coal is a product of tectonic movement and its original primary structure is destroyed during the tectonic process. Compared with intact coal, tectonic coal shows low strength properties and a crushing work ratio of 22.11 J/m2. The specific surface area and total pore volume of the minipores, mesopores, and macropores of the coal strongly increase under conditions of intense tectonism, which indicates that tectonic coal has a very high capacity for rapid initial gas desorption. An adequate supply of gas is required to transport outburst coal, such that the existence of coal particles smaller than the critical diameter is important. Our calculations indicate that the crushing work ratio of coal from the five outburst case ranges from 22.19 to 78.67 J/m2. Only the crushing work ratio of tectonic coal satisfies the requirement for these cases. Therefore, the properties of the tectonic coal and crushing work ratio for the five cases indicate that the widespread occurrence of tectonic coal plays a crucial role in outbursts.

Particle crushing, shear banding, interface abrasion and migration of crushing products all have the potential to influence the behaviour of displacement piles in sands. This paper considers these particulate processes, reporting experiments with model displacement piles installed in uniform pressurised sand and parallel interface ring shear tests. The findings offer new insights into the mechanics of displacement piles in sands.