Subjects -> MINES AND MINING INDUSTRY (Total: 82 journals)
Showing 1 - 42 of 42 Journals sorted alphabetically
Applied Earth Science : Transactions of the Institutions of Mining and Metallurgy     Hybrid Journal   (Followers: 4)
Archives of Mining Sciences     Open Access   (Followers: 1)
BHM Berg- und Hüttenmännische Monatshefte     Hybrid Journal   (Followers: 1)
Canadian Mineralogist     Full-text available via subscription   (Followers: 5)
CIM Journal     Hybrid Journal  
Clay Minerals     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 11)
Environmental Geochemistry and Health     Hybrid Journal   (Followers: 2)
European Journal of Mineralogy     Hybrid Journal   (Followers: 12)
Extractive Industries and Society     Hybrid Journal   (Followers: 2)
Gems & Gemology     Full-text available via subscription   (Followers: 1)
Geology of Ore Deposits     Hybrid Journal   (Followers: 3)
Geomaterials     Open Access   (Followers: 2)
Geotechnical and Geological Engineering     Hybrid Journal   (Followers: 8)
Ghana Mining Journal     Full-text available via subscription   (Followers: 3)
Gold Bulletin     Hybrid Journal  
International Journal of Coal Geology     Hybrid Journal   (Followers: 2)
International Journal of Coal Preparation and Utilization     Hybrid Journal   (Followers: 1)
International Journal of Coal Science & Technology     Open Access   (Followers: 1)
International Journal of Hospitality & Tourism Administration     Hybrid Journal   (Followers: 14)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 8)
International Journal of Mining and Geo-Engineering     Open Access  
International Journal of Mining and Mineral Engineering     Hybrid Journal   (Followers: 5)
International Journal of Mining Engineering and Mineral Processing     Open Access   (Followers: 5)
International Journal of Mining Science and Technology     Open Access   (Followers: 4)
International Journal of Mining, Reclamation and Environment     Hybrid Journal   (Followers: 4)
International Journal of Rock Mechanics and Mining Sciences     Hybrid Journal   (Followers: 6)
Journal of Analytical and Numerical Methods in Mining Engineering     Open Access  
Journal of Applied Geophysics     Hybrid Journal   (Followers: 15)
Journal of Central South University     Hybrid Journal   (Followers: 1)
Journal of China Coal Society     Open Access  
Journal of Convention & Event Tourism     Hybrid Journal   (Followers: 4)
Journal of Geology and Mining Research     Open Access   (Followers: 11)
Journal of Human Resources in Hospitality & Tourism     Hybrid Journal   (Followers: 8)
Journal of Materials Research and Technology     Open Access   (Followers: 2)
Journal of Metamorphic Geology     Hybrid Journal   (Followers: 15)
Journal of Mining Institute     Open Access  
Journal of Mining Science     Hybrid Journal   (Followers: 2)
Journal of Quality Assurance in Hospitality & Tourism     Hybrid Journal   (Followers: 5)
Journal of Sustainable Mining     Open Access   (Followers: 2)
Journal of the Southern African Institute of Mining and Metallurgy     Open Access   (Followers: 5)
Lithology and Mineral Resources     Hybrid Journal   (Followers: 3)
Lithos     Hybrid Journal   (Followers: 9)
Mine Water and the Environment     Hybrid Journal   (Followers: 4)
Mineral Economics     Hybrid Journal  
Mineral Processing and Extractive Metallurgy : Transactions of the Institutions of Mining and Metallurgy     Hybrid Journal   (Followers: 11)
Mineral Processing and Extractive Metallurgy Review     Hybrid Journal   (Followers: 4)
Mineralium Deposita     Hybrid Journal   (Followers: 4)
Mineralogia     Open Access   (Followers: 2)
Mineralogical Magazine     Hybrid Journal   (Followers: 1)
Mineralogy and Petrology     Hybrid Journal   (Followers: 2)
Minerals     Open Access  
Minerals & Energy - Raw Materials Report     Hybrid Journal  
Minerals Engineering     Hybrid Journal   (Followers: 9)
Mining Engineering     Full-text available via subscription   (Followers: 5)
Mining Journal     Full-text available via subscription   (Followers: 3)
Mining Report     Hybrid Journal   (Followers: 2)
Mining Technology : Transactions of the Institutions of Mining and Metallurgy     Hybrid Journal   (Followers: 2)
Mining, Metallurgy & Exploration     Hybrid Journal  
Natural Resources & Engineering     Hybrid Journal  
Natural Resources Research     Hybrid Journal   (Followers: 8)
Neues Jahrbuch für Mineralogie - Abhandlungen     Full-text available via subscription   (Followers: 1)
Physics and Chemistry of Minerals     Hybrid Journal   (Followers: 4)
Podzemni Radovi     Open Access  
Rangeland Journal     Hybrid Journal   (Followers: 1)
Réalités industrielles     Full-text available via subscription  
Resources Policy     Hybrid Journal   (Followers: 4)
Reviews in Mineralogy and Geochemistry     Hybrid Journal   (Followers: 4)
Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica     Open Access  
Rock Mechanics and Rock Engineering     Hybrid Journal   (Followers: 6)
Rocks & Minerals     Hybrid Journal   (Followers: 2)
Rudarsko-geološko-naftni Zbornik     Open Access  
Stainless Steel World     Full-text available via subscription   (Followers: 17)
Transactions of Nonferrous Metals Society of China     Hybrid Journal   (Followers: 9)
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Journal of Central South University
Journal Prestige (SJR): 0.336
Citation Impact (citeScore): 1
Number of Followers: 1  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 2095-2899 - ISSN (Online) 2227-5223
Published by Springer-Verlag Homepage  [2469 journals]
  • Li1.4Al0.4Ti1.6(PO4)3 coated Li1.2Ni0.13Co0.13Mn0.54O2 for enhancing
           electrochemical performance of lithium-ion batteries

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      Abstract: Abstract Lithium (Li)-rich manganese (Mn)-based cathode Li1.2Ni0.13Co0.13Mn0.54O2 (LRNCM) has attracted considerable attention owing to its high specific discharge capacity and low cost. However, unsatisfactory cycle performance and poor rate property hinder its large-scale application. The fast ionic conductor has been widely used as the cathode coating material because of its superior stability and excellent lithium-ion conductivity rate. In this study, Li1.2Ni0.13Co0.13Mn0.54O2 is modified by using Li1.4Al0.4Ti1.6(PO4)3 (LATP) ionic conductor The electrochemical test results show that the discharge capacity of the resulting LRNCM@LATP1 sample is 198 mA·h/g after 100 cycles at 0.2C, with a capacity retention of 81%. Compared with the uncoated pristine LRNCM (188.4 mA·h/g and 76%), LRNCM after the LATP modification shows superior cycle performance. Moreover, the lithium-ion diffusion coefficient DLi+ is a crucial factor affecting the rate performance, and the DLi+ of the LRNCM material is improved from 4.94×10−13 to 5.68×10−12 cm2/s after modification. The specific capacity of LRNCM@LATP1 reaches 102.5 mA·h/g at 5C, with an improved rate performance. Thus, the modification layer can considerably enhance the electrochemical performance of LRNCM.
      PubDate: 2022-05-20
       
  • Experimental study on the shear behavior of grout-infilled specimens and
           micromechanical properties of grout-rock interface

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      Abstract: Abstract The grout-rock interfacial property is one of the key factors associated with the strength of grouted rock masses. In this study, direct shear tests and nanoindentation tests were adopted to investigate the mechanical properties of the grout-rock interface at both the macroscale and microscale. The cohesion of the cement specimens was higher than that of the grout-infilled joint specimens, while their internal friction angle was lower than that of the grout-infilled joint specimens. A “separation method” for identifying the different phases according to the qualitative and quantitative estimations was introduced, and the irregular interfacial transition zone (ITZ) thickness and elastic modulus were estimated. The ITZ thickness of the grout-infilled sandstone specimen ranged from 0 to 30 µm, whereas it was within the range of 10–40 µm for the grout-infilled mudstone specimen. The average elastic modulus of the ITZ in grout-infilled sandstone and mudstone specimens was approximately 58.2% and 54.1% lower than that of the bulk grout, respectively. Regarding the incidence of the rock type, the interlacing between the grout and sandstone was better developed. The ITZ with a higher porosity and lower modulus had a significant effect on the mechanical properties of the grout-infilled specimens.
      PubDate: 2022-05-19
       
  • Discrete element method for adhesion properties evaluation of deep-sea
           sediment from macro and micro perspectives

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      Abstract: Abstract The adhesion between the mining machine and the deep-sea sediments will significantly affect the driving performance of the mining machine in the deep-sea environment. When the mining machine and the deep-sea sediment interaction simulation was carried out, the accuracy of the particle interaction parameters will directly affect the simulation results. This study proposed a method to systematically calibrate the interaction parameters between deep-sea sediment and grouser through the combination of experiment and simulation. The uniaxial compression test and macro adhesion test and corresponding discrete element numerical simulation were carried out, modifying the contact parameters until the simulation results are close to the experimental results. Then the micro-parameters of the JKR adhesion contact model were back calibrated with the test results, and the contact parameters between soil particle-soil particle and soil particle-metal are calibrated. Besides, the adhesion test shows that the adhesion forces were ranked in the order of 5052<STi80<TA2<TC4 under the same surface roughness, which indicates the aluminum alloy 5052 has the best anti-adhesion performance. The relationship between surface adhesion force and microscopic contact parameters was studied by discrete element numerical simulation, and the result shows that the coefficient of static friction and the coefficient of rolling friction has little effect on adhesion force. While it is mainly affected by the coefficient of restitution and surface energy, the surface adhesion force tends to decrease with the increase of the coefficient of restitution and increase with the growth of surface energy. The obtained parameters of soil particle to soil particle and soil particle to metal affecting the adhesion can contribute to the design optimization for the grouser of mining machines to decrease surface adhesion and enhance its movability and mining efficiency.
      PubDate: 2022-05-19
       
  • Fractal model of thermal elasto-plastic contact of rough surfaces

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      Abstract: Abstract Without considering the influence of heat, existing fractal contact models are not applicable to analyze the contacts when the temperature changes. For this problem, the normal load model and the normal stiffness model of thermal elasto-plastic contact of rough surfaces are developed respectively in this paper. The proposed model is based on the normal contact mechanics model of fractal theory of anisotropic and thermal elasto-plastic contact theory which can be used to characterize the rough surface thermodynamic properties. Then the validity of the model is verified. Finally, the influence of main parameters on the total normal load and the whole normal stiffness of thermal elasto-plastic contact at the interface is analyzed by contact simulation. The results show that the total normal load of thermal elasto-plastic contact increases with the increases of temperature. The whole normal stiffness of thermal elasto-plastic contact increases with increasing coefficient of linear expansion, scale factor, temperature difference or fractal dimension, but decreases with increasing fractal roughness. This model expands basic theory and applications of traditional models, and can be used to calculate and analyze the contacts when the temperature changes.
      PubDate: 2022-05-19
       
  • Model tests on uplift capacity of double-belled pile influenced by
           distance between bells

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      Abstract: Abstract To optimize the distance between the bells in pile design, this paper reports a series of small scale tests on the uplift capacity of double belled piles embedded in dry dense sand considering different bell space ratios. Finite element modelling is also performed to evaluate the range of soil failure around the piles during pile uplift displacement. Test results show that when bell space ratio is 6 or 8, the uplift capacity reaches the peak value. The upper bell bears more load than the lower one for the piles with bell space ratio less than 6, while the lower bell bears more load than the upper one for the piles with bell space ratio larger than 8.
      PubDate: 2022-05-04
       
  • Complex geometric modeling and tooth contact analysis of a helical face
           gear pair with arc-tooth

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      Abstract: Abstract A complex geometric modeling method of a helical face gear pair with arc-tooth generated by an arc-profile cutting (APC) disc is proposed, and its tooth contact characteristics are analyzed. Firstly, the spatial coordinate system of an APC face gear pair is established based on meshing theory. Combining the coordinate transformation matrix and the tooth profile of the cutter, the equations of the curve envelope of the APC face gear pair are obtained. Then the surface equations are solved to extract the point clouds data by programming in MATLAB, which contains the work surface and the fillet surface of the APC face gear pair. And the complex geometric model of the APC face gear pair is built by fitting its point clouds. At last, through the analysis of the tooth surface contact, the sensitivity of the APC face gear to the different types of mounting errors is obtained. The results show that the APC face gear pair is the most sensitive to mounting errors in the tooth thickness direction, and it should be strictly controlled in the actual application.
      PubDate: 2022-05-04
       
  • A new discriminative sparse parameter classifier with iterative removal
           for face recognition

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      Abstract: Abstract Face recognition has been widely used and developed rapidly in recent years. The methods based on sparse representation have made great breakthroughs, and collaborative representation-based classification (CRC) is the typical representative. However, CRC cannot distinguish similar samples well, leading to a wrong classification easily. As an improved method based on CRC, the two-phase test sample sparse representation (TPTSSR) removes the samples that make little contribution to the representation of the testing sample. Nevertheless, only one removal is not sufficient, since some useless samples may still be retained, along with some useful samples maybe being removed randomly. In this work, a novel classifier, called discriminative sparse parameter (DSP) classifier with iterative removal, is proposed for face recognition. The proposed DSP classifier utilizes sparse parameter to measure the representation ability of training samples straight-forward. Moreover, to avoid some useful samples being removed randomly with only one removal, DSP classifier removes most uncorrelated samples gradually with iterations. Extensive experiments on different typical poses, expressions and noisy face datasets are conducted to assess the performance of the proposed DSP classifier. The experimental results demonstrate that DSP classifier achieves a better recognition rate than the well-known SRC, CRC, RRC, RCR, SRMVS, RFSR and TPTSSR classifiers for face recognition in various situations.
      PubDate: 2022-05-04
       
  • Markov chain-based platoon recognition model in mixed traffic with
           human-driven and connected and autonomous vehicles

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      Abstract: Abstract Many vehicle platoons are interrupted while traveling on roads, especially at urban signalized intersections. One reason for such interruptions is the inability to exchange real-time information between traditional human-driven vehicles and intersection infrastructure. Thus, this paper develops a Markov chain-based model to recognize platoons. A simulation experiment is performed in Vissim based on field data extracted from video recordings to prove the model’s applicability. The videos, recorded with a high-definition camera, contain field driving data from three Tesla vehicles, which can achieve Level 2 autonomous driving. The simulation results show that the recognition rate exceeds 80% when the connected and autonomous vehicle penetration rate is higher than 0.7. Whether a vehicle is upstream or downstream of an intersection also affects the performance of platoon recognition. The platoon recognition model developed in this paper can be used as a signal control input at intersections to reduce the unnecessary interruption of vehicle platoons and improve traffic efficiency.
      PubDate: 2022-05-04
       
  • Effect of Ni/Fe ratio on activation sintering and mechanical properties of
           molybdenum nickel iron alloy

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      Abstract: Abstract In order to improve the low ductility of the Mo-Ni alloy, Fe is added and the effects of Ni/Fe mass ratio on the densification behavior, microstructure evolution and mechanical properties of alloy were investigated. The experimental results show that when iron is added to 95Mo-5Ni alloy, the formation of brittle intermetallic phase δ-MoNi at the grain boundary is avoided. Meanwhile, the grain growth of Mo is also effectively inhibited in the sintering process. However, the addition of iron reduces the degree of densification of alloy since the activation effect of Ni is superior to that of Fe. From the experimental results, it could be concluded that the maximum hardness and bending strength are achieved by 95Mo-1.5Ni-3.5Fe alloy, which are HV 614 and 741 MPa, respectively. Combined with the analyses of bending fracture mechanism, the improvement relative to Mo-Ni alloy is likely attributed to the inhibition of the brittle phase.
      PubDate: 2022-05-04
       
  • Effects of confining pressure on deformation failure behavior of jointed
           rock

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      Abstract: Abstract For a deeper understanding of the deformation failure behavior of jointed rock, numerical compression simulations are carried out on a rock specimen containing non-persistent joints under confining pressure with the bonded-particle model. The microscopic parameters which can reflect the macroscopic mechanical properties and failure behavior of artificial jointed specimens are firstly calibrated. Then, the influence of joint inclination and confining pressure on stress — strain curves, crack patterns, and contact force distributions of jointed rock are investigated. The simulation results show that both the compressive strength and elastic modulus of the specimens increase with increasing confining pressure, and these two mechanical parameters decrease first and then increase with the increase of joints inclination. The sensitivity of strength and elastic modulus to confining pressure is not the same in different joints inclinations, which has the least impact on specimens with α=90°. Under low confining pressure, the failure modes are controlled by the joint inclination. As the confining pressure increased, the initiation and propagation of tensile crack are gradually inhibited, and the failure mode is transferred from tensile failure to shear-compression failure. Finally, the reinforcement effect of prestressed bolt support on engineering fractured rock mass is discussed.
      PubDate: 2022-04-29
       
  • Effect of Na2O on transition and stability of dicalcium silicate based on
           sintering process

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      Abstract: Abstract The phase transition, morphology, stability and pulverization performance of dicalcium silicate (C2S) with different Na2O additions during the high-temperature sintering process were studied using XRD, SEM-EDS, FT-IR, and Raman spectra methods. When the CaO to SiO2 molar ratio is 2.0 and the Na2O to SiO2 molar ratio is below 0.20, the crystalline calcium silicate compounds include γ-C2S and β-C2S. As the Na2O addition increases, the proportion, crystallinity and grain size of β-C2S in the sintered products increase, those parameters of γ-C2S decrease, and the content of amorphous phase increases. Na2O mainly forms solid solutions in β-C2S and inhibits the transition of β-C2S to γ-C2S, resulting in the sintered products unpulverized. The stability of sintered products in alkali solution decreases significantly with the increasing Na2O additions, and the β-C2S solid solution with Na2O is less stable than γ-C2S. The mechanism that Na2O affects the transition of C2S as well as its stability was also discussed, which can give actual guidance for the treatment of low-grade alumina-containing resources by the sintering process.
      PubDate: 2022-04-29
       
  • Optical and electrical properties of room temperature prepared α-IGZO
           thin films using an In2Ga2ZnO7 ceramic target

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      Abstract: Abstract In this study, a high-purity In2Ga2ZnO7 ceramic target was used to deposit indium gallium zinc oxide (IGZO) films by RF magnetron sputtering technology. The microstructure, growth state, optical and electrical properties of the IGZO films were studied. The results showed that the surface of the IGZO film was uniform and smooth at room temperature. As the substrate temperature increased, the surface roughness of the film gradually increased. From room temperature to 300 ° C, all the films maintained amorphous phase and good thermal stabilities. Moreover, the transmission in the visible region decreased from 91.93% to 91.08%, and the band gap slightly decreased from 3.79 to 3.76 eV. The characterization of the film via atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) demonstrated that the film prepared at room temperature exhibited the lowest surface roughness and the largest content of oxygen vacancies. With the rise in temperature, the non-homogeneous particle distribution, increase in the surface roughness, and reduction in the number of oxygen vacancies resulted in lower performance of the α-IGZO film. Comprehensive analysis showed that the best optical and electrical properties can be obtained by depositing IGZO films at room temperature, which indicates their potential applications in flexible substrates.
      PubDate: 2022-04-01
       
  • Elastoplastic analysis of solid structures using penalty-based couple
           stress finite element method within framework of Cosserat continuum

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      Abstract: Abstract To obviate the complexities of the straight forward couple stress finite element method, the penalty-based couple stress finite element method (named PcouFEM) within the framework of the Cosserat continuum is utilized to obtain the approximate solution by relaxing the C1 continuity. To examine the performance of the PcouFEM, three well-known numerical examples are investigated. For the analysis on stress concentration around the circular hole of the planestrain specimen, it was found that as long as the penalty factor Gc is not less than 5 times the shear modulus of the classical continuum G (i. e., Gc⩾5G), the stress concentration factors calculated by the PcouFEM with the reduced integration scheme agree well with the analytical solutions. For the strain localization analysis in the uniaxial compression test, it was observed that by applying the PcouFEM, the pathologically mesh-dependent problem associated with the conventional FEM can be alleviated or even removed, and based on numerical simulations, it is recommended to define 5G⩽Gc⩽10G from the perspective of numerical accuracy. For the soil slope subjected to an eccentric load through the rigid strip footing, it was found that the mesh-dependent problem of the shear band simulation can be largely alleviated by applying the PcouFEM.
      PubDate: 2022-04-01
       
  • Hourly traffic flow forecasting using a new hybrid modelling method

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      Abstract: Abstract Short-term traffic flow forecasting is a significant part of intelligent transportation system. In some traffic control scenarios, obtaining future traffic flow in advance is conducive to highway management department to have sufficient time to formulate corresponding traffic flow control measures. In hence, it is meaningful to establish an accurate short-term traffic flow method and provide reference for peak traffic flow warning. This paper proposed a new hybrid model for traffic flow forecasting, which is composed of the variational mode decomposition (VMD) method, the group method of data handling (GMDH) neural network, bi-directional long and short term memory (BILSTM) network and ELMAN network, and is optimized by the imperialist competitive algorithm (ICA) method. To illustrate the performance of the proposed model, there are several comparative experiments between the proposed model and other models. The experiment results show that 1) BILSTM network, GMDH network and ELMAN network have better predictive performance than other single models; 2) VMD can significantly improve the predictive performance of the ICA-GMDH-BILSTM-ELMAN model. The effect of VMD method is better than that of EEMD method and FEEMD method. To conclude, the proposed model which is made up of the VMD method, the ICA method, the BILSTM network, the GMDH network and the ELMAN network has excellent predictive ability for traffic flow series.
      PubDate: 2022-04-01
       
  • Preparation of porous silica from natural chlorite via selective acid
           leaching and its application in methylene blue adsorption

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      Abstract: Abstract In this study, porous silica with high surface area was prepared through selective leaching of thermally activated chlorite in HCl solution. In the process, chlorite was activated by pre-calcining treatment, then activated components (MgO, Al2O3, and Fe2O3) were selectively leached by acid solution, resulting in the formation of nanopores in situ. The morphology, structure, surface area and pore-size distribution of the material were characterized by XRD, TG/DSC, 27Al MAS NMR, SEM, TEM and N2 adsorption-desorption isotherms. The highest specific surface area (SBET=333 m2/g) was obtained by selectively leaching the 600 °C calcined chlorite from 3 mol/L HCl at 90 °C for 2 h. The pore sizes and specific surface areas can be controlled by calcination and leaching conditions. The 27Al MAS NMR spectra of the samples revealed the relationship between structural transformation and the selective acid leaching properties of thermal-activated chlorite, demonstrating that AlVI transfers into AlV when chlorite changes into activated chlorite during thermal activation, and the coordinations of Al has a significant effect on acid solubility of chlorite. The as-prepared porous silica showed favorable adsorption abilities with capacity of 148.79 mg/g for methylene blue at pH of about 7 and temperature of 25 °C, indicating its promising potential in adsorption application.
      PubDate: 2022-04-01
       
  • Effect of variable thickness cross rolling on edge crack and
           microstructure gradient of AZ31 magnesium alloy

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      Abstract: Abstract The hot rolling experiment of AZ31 magnesium alloy was carried out by laying anoverlay mold at the initial temperature of 400 °C. According to the Mizushima automatic plan view pattern control system (MAS) rolling theory and the cross rolling process, different reductions in the middle and edges of the magnesium alloy were realized, and the influence of the regional controlled reduction rolling on the edge cracks and microstructure gradient of the magnesium alloy were analyzed. It is shown that this rolling approach has reduced the maximum edge crack depth of the rolled piece by 56.85%, and there is a weakening tendency in the base surface texture of the strip edge, the base surface texture density drops from 23.97 to 17.48 after ordinary flat rolling. It exhibits basal texture gradients from the edge to the middle of the sheet along the RD direction, which reflected the uneven deformation of the sheets. It is suitable for the processing of metal molds that require large edge reductions such as mobile phone shells, and provided a theoretical basis for the variable thickness rolling of the magnesium alloy strip.
      PubDate: 2022-04-01
       
  • Experimental investigation on mechanical behaviors of granites after
           high-temperature exposure

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      Abstract: Abstract To investigate the influence of temperature on the physical, mechanical and acoustic emission characteristics of granites, uniaxial compression test, variable-angle shear test, acoustic emission signal monitoring and the measurement of physical parameters including mass, size and P-wave velocity were carried out on granite samples treated at temperatures T ranging from 25 to 900 ° C. The results show that the density and P-wave velocity decrease gradually with increasing T. As the temperature increases, the peak compressive stress decreases while the peak strain increases, due to the fact that a high temperature induces the escaping of waters within granites, the expanding of mineral grains and the generations of fractures. With the increment of T, both the peak shear stress and the cohesion decrease, whereas the frictional angle increases. During the compressing and shearing tests, the maximum acoustic emission counts show a decreasing trend when T increases from 25 to 900 °C. When T exceeds 573 °C, the crystal lattice structure of quartz changes from α-phase to β-phase, decreasing the mechanical behavior of granites to a great extent. In addition, the results also indicate that T=500–600 °C is the critical temperature ramge to characterize the influence of temperature on the physical, mechanical and acoustic emission characteristics of granites.
      PubDate: 2022-04-01
       
  • Grain boundary effects on spall behavior of high purity copper cylinder
           under sweeping detonation

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      Abstract: Abstract A series of sweeping detonation experiments were conducted to study the grain boundary effects during the primary spallation of high-purity copper cylinder. The free surface velocity profile of the shocked samples was measured by Doppler pins systems. The soft-recovered samples were characterized by optical and electron backscatter diffraction microscopy, and the effects of microstructures like grain boundaries, and crystal orientation on spall behavior were investigated. The results indicated that the critical stress of deformation twinning in cylindrical copper increased. The nucleation sites of spallation damage were determined by the joint influence of the grain orientation (Taylor factor) and the angle between grain boundaries and radial impact-stress direction. Voids were prone to nucleating at the grain boundaries perpendicular to the radial impact-stress direction. Nevertheless, the number of voids nucleated at boundaries was relatively different from the results obtained from the plate impact experiment and plate sweeping detonation experiment, which is a result of the curvature that existed in the cylindrical copper and the obliquity of the impact-stress direction during sweeping detonation loading.
      PubDate: 2022-04-01
       
  • Numerical analysis on mixed lubrication performance of journal-thrust
           coupled microgroove bearings with different bottom shapes

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      Abstract: Abstract The purpose of the present study is to establish a mixed lubrication model for the journal-thrust coupled microgroove bearings (also referred as coupled bearings) used for the ship shaftless rim-driven thrusters. During the hydrodynamic modelling, the coupling hydrodynamic pressure between the journal bearing and the thrust bearing is considered. The mixed lubrication performances of the microgroove journal-thrust bearing with five different bottom shapes, including rectangle, semi-ellipse, right triangle, isosceles triangle and left triangle, are compared. Based on the numerical results, the optimal microgroove bottom shape of the journal bearing and tilting angle of the thrust pad are determined. Additionally, the comparative analysis shows that the coupled bearing with left triangle microgroove bottom shape exhibits the optimal mixed lubrication performance. The numerical result also indicates that the optimal inclination angle of the thrust bearing pad is 0.01° for the current simulation case.
      PubDate: 2022-04-01
       
  • Impact of ultrasonic power on liquid fraction, microstructure and physical
           characteristics of A356 alloy molded through cooling slope

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      Abstract: Abstract This study involves A356 alloy molded through ultrasonically vibrated cooling slope. The slope alongside ultrasonic power enables indispensable shear for engendering slurry from which the semisolid cast/heat treated billets got produced. An examination demonstrates ultrasonically vibrated cooling slope influencing the liquid fraction/microstructure/physical characteristics of stated billets. The investigation encompasses five diverse ultrasonic powers (0, 75, 150, 200, 250 W). The ultrasonic power of 150 W delivers finest/rounded microstructure with enhanced physical characteristics. Microstructural modifications reason physical transformations because of grain refinement and grain-boundary/Hall-Petch strengthening. A smaller grain size reasons a higher strength/shape factor and an increased homogeneity reasons a higher ductility. Microstructural characteristics get improved by reheating. It is owing to coalescence throughout temperature homogenization. The physical characteristics is improved by reheating because of a reduced porosity and enhanced dissolution besides augmented homogeneity. A direct comparison remains impossible owing to unavailability of researches on ultrasonically vibrated cooling slope.
      PubDate: 2022-03-31
       
 
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