1,721,396 research outputs found
Corrected values for boiling points and enthalpies of vaporization of elements in handbooks
Get PDFThe scientific community relies upon the veracity of the scientific data in handbooks and databases. In a previous work, the authors developed a systematic, intelligent, and potentially automatic method to detect errors in such resources based on artificial neural networks (ANNs). This method revealed variations from (10 to 900) % in tables of property data for elements in the periodic table and pointed out the ones that are most probably correct. In this paper, we focus on the details of employing this method for analyzing the data of boiling points and enthalpies of vaporization recorded in different handbooks. The method points out the values that are likely to be correct. To verify the method employed, a detailed discussion of the data with reference to the original literature sources is given as well as factors that may affect the accuracy of the prediction.<br/
A novel heterogeneous CPU/GPGPU-accelerated 3D CDEM and its application to modeling deep roadway excavation
No full textTo improve the accuracy and computational efficiency of the CDEM for deep coal mine roadway excavation modeling, this study proposes a heterogeneous CPU/GPGPU-accelerated solver that integrates a mixed continuous-discontinuous media algorithm. The solver employs an explicit time integration method combined with a modular approach for 3D tetrahedral solid finite elements and fracturable penalty springs, which model rock fracture behavior and the transition from continuum to discontinuum in rock masses. To maximize computational efficiency, the solver uses a hybrid CPU/GPGPU framework with SIMD parallel techniques, achieving up to 600-fold speedup on a single GPGPU. The solver's accuracy is validated for both quasi-static and dynamic problems, and its scalability across different hardware accelerators is demonstrated. Modeling results from the 22nd mining area of the Quandian coal mine show significant shear deformation and crack evolution in the soft rock, particularly at the intersection of the roof slab and sidewall, where stress concentration and large deformation are most pronounced. These findings validate the efficiency and reliability of the proposed method for simulating and analyzing underground excavation processes
An interface constitutive model of plastic tensile-compressive damage under impact loading based on continuous-discontinuous framework
No full textBullet penetration test is a classic impact loading test, which involves complex dynamic elastic-plastic response. Conventionally, this process was often described using a single high -strain -rate constitutive model, which could only capture a specific type of failure during the impact damage process. Furthermore, these constitutive models were mostly defined on element and posed the risk of computational divergence(element distortion). In this work, a novel constitutive model for combined tensile-compressive damage in interface element was developed within a Continuous-Discontinuous Element Method(CDEM) framework. This model successfully captures the processes of pit formation and target collapse during projectile penetration. The tension and compression damage parts of the developed interface constitutive model were validated through Brazilian splitting test and interface direct shear test. Subsequently, bullet penetration test is simulated and the postpenetration velocity is compared with published results from other studies, with computational errors found to be within 2.56%, thus validating the accuracy of the developed interface constitutive model
Virtual displacement based discontinuity layout optimization
No full textDiscontinuity layout optimization (DLO) is a relatively new upper bound limit analysis method. Compared to classic topology optimization methods, aimed at obtaining the optimum design of a structure by considering its self-weight, building cost, or bearing capacity, DLO optimizes the failure pattern of the structure under specific loading conditions and constraints by minimizing the dissipation energy. In this work, we present a modified DLO algorithm that contains all of the advantages of DLO. It is referred to virtual displacement-based discontinuity layout optimization (VDLO). VDLO takes the stress state of a loaded structure as a snapshot and correspondingly provides the optimum failure pattern, which greatly extends the application potential of DLO. Numerical examples indicate the effectiveness and flexibility of VDLO. It is regarded as a highly promising supplemental tool for other numerical methods in element-/node-based frameworks
Wind Field Digital Twins Sandbox System for Transmission Towers
No full textGiven the digitalization trends within the field of engineering, we propose a practical approach to engineering digitization. This method is established based on a physical sandbox model, camera equipment and simulation technology. We propose an image processing modeling method to establish high-precision continuous mathematical models of transmission towers. The calculation of the wind field is realized by using wind speed calculations, a load-wind-direction-time algorithm and the Continuum-Discontinuum Element Method (CDEM). The sensitivity analysis of displacement- and acceleration-controlled transmission tower loads under two different wind direction conditions is conducted. The results show that the digital model exhibits a proportional relationship with the physical dimensions of the transmission tower model. The error between the numerical simulation results and the experimental results falls within a reasonable range. Nodes at higher positions of the transmission tower experience significantly higher forces compared to those at lower positions, and the structural forms with larger windward projected areas yield similar simulation results. The proposed digital twin system can help monitor the performance of structural bodies and assess the disaster degree in extreme conditions. It can guide specific maintenance and repair tasks
Continuous-discontinuous element method for three-dimensional thermal cracking of rocks
No full textThermal cracking of rocks can significantly affect the durability of underground structures in engineering practices such as geothermal energy extraction, storage of nuclear waste and tunnelling in freeze-thaw cycle induced areas. It is a scenario of strong coupled thermomechanical process involving discontinuity behaviours of rocks. In this context, a numerical model was proposed to investigate the thermal cracking of rocks, in a framework of the continuous-discontinuous element method (CDEM) for efficiently capturing the initiation and propagation of multiple cracks. A simplex integration strategy was adopted to account for the influences of temperature-dependent material properties. Several benchmark tests were considered and the obtained results were compared with analytical solutions and numerical results from the literature. The results show that the fracture degree of the cases when considering temperature-dependent material parameters had 10% differences approximately compared with the cases with constant parameters. (C) 2023 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
A simple and efficient three-dimensional spring element model for pore seepage problems
No full textThis study introduces a novel spring element model for efficient simulation of nonlinear seepage in porous media. The model discretizes the simulation domain into tetrahedral elements and constructs orthogonal Three-dimensional permeability networks within each element, establishing a quantitative relationship between pipe flow and nodal pressure differences. By developing a mathematical model linking network flow to nodal pressure differences, the method enables precise allocation of pipe flow in the local coordinate system and accurate transformation to the global coordinate system, thereby determining nodal flow and velocity. The Three-Dimensional Seepage Spring Element Method (3D-SSEM) simplifies the element flow matrix in finite element analysis to three essential pipe permeability stiffness values, thereby reducing computational complexity. Coupled with parallel computing strategies, the algorithm achieves significant improvements in computational efficiency and memory usage. The method is validated through four numerical examples, demonstrating high efficiency and accuracy in solving saturated-unsaturated seepage problems. Compared with analytical solutions and other numerical methods, it exhibits superior convergence and reduced solution time while maintaining precision. Additionally, the method effectively simulates complex coupled processes in large-scale real-world environments, offering robust support for practical engineering design optimization
Numerical Analysis of Perforation during Hydraulic Fracture Initiation Based on Continuous-Discontinuous Element Method
No full textPerforation is a pivotal technique employed to establish main flow channels within the reservoir formation at the outset of hydraulic fracturing operations. Optimizing perforation designs is critical for augmenting the efficacy of hydraulic fracturing and boosting oil or gas production. In this study, we employ a hybrid finite-discrete element method, known as the continuous - discontinuous element method (CDEM), to simulate the initiation of postperforation hydraulic fractures and to derive enhanced design parameters. The model incorporates the four most prevalent perforation geometries, as delineated in an engineering technical report. Real -world perforations deviate from the ideal cylindrical shape, exhibiting variable cross-sectional profiles that typically manifest as an initial constriction followed by an expansion, a feature consistent across all four perforation types. Our simulations take into account variations in perforation hole geometries, cross-sectional diameters, and perforation lengths. The findings show that perforations generated by the 39g DP3 HMX perforating bullet yield the lowest breakdown pressure, which inversely correlates with increases in sectional diameter and perforation length. Moreover, this study reveals the relationship between breakdown pressure and fracture degree, providing valuable insights for engineers and designers to refine perforation strategies
Exploring correlations between properties using artificial neural networks
No full textThe traditional aim of materials science is to establish the causal relationships between composition, processing, structure, and properties with the intention that, eventually, these relationships will make it possible to design materials to meet specifications. This paper explores another approach. If properties are related to structure at different scales, there may be relationships between properties that can be discerned and used to make predictions so that knowledge of some properties in a compositional field can be used to predict others. We use the physical properties of the elements as a dataset because it is expected to be both extensive and reliable and we explore this method by showing how it can be applied to predict the polarizability of the elements from other properties
Predicting the structural stability and formability of ABO3-Type perovskite compounds using artificial neural networks
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