Review of calibration strategies for discrete element model in quasi-static elastic deformation

Abstract This study first reviewed theories of the mechanical response of structures under loading, and the discrete element method provides a route for studying mechanical response including elastic deformation and structure failure. However, the direct acquisition of the microscopic parameters from the governing equations of the discrete element method via experiments encounters challenges. One possible strategy to obtain these microscopic parameters is parameter calibration that are widely used by researchers. Secondly, the governing equations and failure criterion of the discrete element method are summarized, and the microscopic parameters that would be calibrated are pinpointed. Next, the principles of classical calibration methods of discrete element method are explicated in detail, alongside the validation and discussion of their properties. Lastly, this study examined the applicability of calibrated parameters and points out that the size ratio, porosity, maximum radius, and minimum radius of particles should be identical in both the geometric calibration model and that for applications

Multi-Motor Cooperative Control Strategy for Speed Synchronous Control of Construction Platform

Barrel-type structures are ubiquitous in industry and life. A novel construction platform of barrel-type structures is introduced, and it involves a multi-motor system. The synchronous control of multiple motors has great importance. To guarantee the high precision, high stability, and fast response for the collaborative control of multiple motors, this paper proposes a multi-motor cooperative control strategy. Firstly, a speed synchronization control structure between multiple permanent magnet synchronous motors (PMSM) is designed by way of the mean coupling control structure. Then, the conventional PID controller is improved by machine learning. Moreover, a radial basis function neural (RBF) network is introduced to the conventional PID algorithm for system identification processing, and the gradient descent algorithm is used for parameter updating. An improved variable speed integral term is introduced into the integral term of the conventional PID algorithm to eliminate the error as soon as possible. Finally, it is verified via numerical simulation experiments that show the multi-motor cooperative control strategy has high anti-interference ability and robustness

Hydro-Damage Properties of Red-Bed Mudstone Failures Induced by Nonlinear Seepage and Diffusion Effect

Nonlinear catastrophes caused by geological fluids are a fundamental issue in rock mechanics and the geoengineering hazard field. For the consideration of hydrodynamic force on red-bed mudstone softening damage, X-ray visualization tests on the fissure flow in mudstone block failure under hydrodynamic force was performed in this study based on block scale, and the physical phenomena of fissure seepage and nonlinear diffusion were further explored. A new method for evaluating the hydro-damage degrees of rocks using an X-ray image analysis was proposed, and the quantitative relation of diffusion coefficients of hydro-damage and seepage was established. The research results revealed that the hydrodynamic force promoted the fluid-filled fissure behavior in mudstone specimen failure. Furthermore, the seepage and diffusion phenomena of fluid in rocks during failures were indicated using X-ray imaging. A dual mechanical behavior was presented in the nonlinear seepage and abnormal diffusion of a red mudstone geological body under hydrodynamic conditions. The damaged degree of mudstone was aggravated by the effect of hydrodynamic force, and the initial seepage–diffusion coefficient with respect to lower hydro-damage was larger than the final seepage–diffusion coefficient with respect to higher hydro-damage of rocks with a decreasing nonlinear trend

Variations in Permeability and Mechanical Properties of Basaltic Rocks Induced by Carbon Mineralization

Carbon capture, utilization, and storage (CCUS/CCS) is a strategic choice for ensuring energy security and reducing carbon dioxide emissions across the globe. The injection of CO2 into the basaltic reservoir is one strategy for the permanent disposal of carbon emissions. Basaltic rocks, which are widely distributed in Hainan Island, are capable of CO2 geological sequestration. In this study, the reaction of CO2-NaOH/Ca(OH)2-basaltic rocks under conditions of 6.0 M Pa and 30 °C was performed using basaltic samples collected from the Fushan area of the Hainan Province to evaluate the sequestration of CO2 in basalt by mineralization. Then, the effect of CO2 mineralization on the permeability and mechanical properties of basaltic rocks was evaluated using X-ray computer tomography and triaxial compression testing at 21.0 MPa. In addition, microwave technology was used to irradiate the basaltic rocks before mineralization. Changes in the permeability of basalt before and after mineralization and microwave irradiation were simulated numerically, and their effects on the mechanical strength deterioration of basalt were analyzed according to the rock mechanics using triaxial testing. Based on these results, a new method for the induction of basalt deterioration, mineralization, CO2 injectivity, and storage capacity using microwave irradiation is proposed for use in CCUS/CCS engineering

Investigation of Hydro-mechanical Behaviour of Excavation Induced Damage Zone of Callovo-Oxfordian Claystone: Numerical Modeling and In-situ Experiment

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A Functional Air-Stable Li_9.8GeP_1.7Sb_0.3S_11.8I_0.2 Superionic Conductor for High-Performance All-Solid-State Lithium Batteries

Solid-state electrolytes (SSEs) based on sulfides have become a subject of great interest due to their superior Li-ion conductivity, low grain boundary resistance, and adequate mechanical strength. However, they grapple with chemical instability toward moisture hypersensitivity, which decreases their ionic conductivity, leading to more processing requirements. Herein, a Li9.8GeP1.7Sb0.3S11.8I0.2 (LGPSSI) superionic conductor is designed with a Li+ conductivity of 6.6 mS cm-1 and superior air stability based on hard and soft acids and bases (HSAB) theory. The introduction of optimal antimony (Sb) and iodine (I) into the Li10GeP2S12 (LGPS) structure facilitates fast Li-ion migration with low activation energy (Ea) of 20.33 kJ mol–1. The higher air stability of LGPSSI is credited to the strategic substitution of soft acid Sb into (Ge/P)­S4 tetrahedral sites, examined by Raman and X-ray photoelectron spectroscopy techniques. Relatively lower acidity of Sb compared to phosphorus (P) realizes a stronger Sb–S bond, minimizing the evolution of toxic H2S (0.1728 cm3 g–1), which is ∼3 times lower than pristine LGPS when LGPSSI is exposed to moist air for 120 min. The NCA//Li–In full cell with a LGPSSI superionic conductor delivered the first discharge capacity of 209.1 mAh g–1 with 86.94% Coulombic efficiency at 0.1 mA cm–2. Furthermore, operating at a current density of 0.3 mA cm–2, LiNbO3@NCA/LGPSSI/Li–In cell demonstrated an exceptional reversible capacity of 117.70 mAh g–1, retaining 92.64% of its original capacity over 100 cycles