scholarly journals Numerical Damping Calibration Study of Particle Element Method-Based Dynamic Relaxation Approach for Modeling Longwall Top-Coal Caving

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2348
Author(s):  
Hongbin Li ◽  
Dongyin Li ◽  
Weiyu Zhang ◽  
Huamin Li ◽  
Shen Wang ◽  
...  
Keyword(s):  
Calibration Method ◽  
Dynamic Relaxation ◽  
Rock Breakage ◽  
Flow Problems ◽  
Multi Scale ◽  
Coal Particles ◽  
Numerical Damping ◽  
Solution Equation ◽  
Longwall Top Coal Caving ◽  
Explicit Dynamic

When using the explicit dynamic relaxation approach (DRA) to model the quasi-static rock breakage, fragmentation, and flow problems, especially the top-coal caving question, introducing numerical damping into the solution equation is inevitable for reducing the vibration frequency and impact speed of mesh nodes, which is significantly affect the fidelity of the computation results. Although the DRA has been widely adopted to simulate top-coal caving, the reasonable value and calibration method of numerical damping are still open issues. In this study, the calibration process of reasonable numerical damping for modeling top-coal caving is investigated by comparing with the experimental results, in which several geometry parameters of the drawing funnel are selected as the calibration indexes. The result shows that the most reasonable numerical damping value is 0.07 for the numerical modeling of interval top-coal caving in extra-thick coal seams. Finally, the correlation between the numerical damping and the physical top-coal drawing process is discussed. The numerical damping indirectly reflects the fragmentation in multi scale of coal mass and friction interaction between coal particles during the caving process, which reduces the vibration intensity of the top-coal caving system and dissipates the kinetic energy.

scholarly journals A Hybrid Method for Inland Ship Recognition Using Marine Radar and Closed-Circuit Television

2021 ◽  
Vol 9 (11) ◽  
pp. 1199
Author(s):  
Xinglong Liu ◽  
Yicheng Li ◽  
Yong Wu ◽  
Zhiyuan Wang ◽  
Wei He ◽  
...  
Keyword(s):  
Region Of Interest ◽  
Weather Conditions ◽  
Calibration Method ◽  
Closed Circuit ◽  
Automatic Identification ◽  
Identification System ◽  
Closed Circuit Television ◽  
Multi Scale ◽  
Marine Radar ◽  
Ship Recognition

Vessel recognition plays important role in ensuring navigation safety. However, existing methods are mainly based on a single sensor, such as automatic identification system (AIS), marine radar, closed-circuit television (CCTV), etc. To this end, this paper proposes a coarse-to-fine recognition method by fusing CCTV and marine radar, called multi-scale matching vessel recognition (MSM-VR). This method first proposes a novel calibration method that does not use any additional calibration target. The calibration is transformed to solve an N point registration model. Furthermore, marine radar image is used for coarse detection. A region of interest (ROI) area is computed for coarse detection results. Lastly, we design a novel convolutional neural network (CNN) called VesNet and transform the recognition into feature extraction. The VesNet is used to extract the vessel features. As a result, the MVM-VR method has been validated by using actual datasets collected along different waterways such as Nanjing waterway and Wuhan waterway, China, covering different times and weather conditions. Experimental results show that the MSM-VR method can adapt to different times, different weather conditions, and different waterways with good detection stability. The recognition accuracy is no less than 96%. Compared to other methods, the proposed method has high accuracy and great robustness.

scholarly journals Multi-scale modelling of the trabecular bone elastoplastic behaviour under compression loading

2012 ◽  
Author(s):  
A. Jaziri ◽  
J. Rahmoun ◽  
H. Naceur ◽  
P. Drazetic ◽  
E. Markiewicz
Keyword(s):  
Mechanical Properties ◽  
Porous Media ◽  
Velocity Field ◽  
Trabecular Bone ◽  
Yield Criterion ◽  
Micromechanical Model ◽  
Coupled Model ◽  
Multi Scale ◽  
Scale Modelling ◽  
Explicit Dynamic

We propose a new elastoplastic damage coupled model for the modelling of trabecular bone behaviour. The damage is carried out thanks to the limit analysis based on the MCK criterion. We first present the methodology allowing the estimation of elastic anisotropic properties of porous media by means of Mori–Tanaka homogenisation scheme. Then, we present the formulation of the integrated yield criterion derived by considering trial velocity field inspired from the Eshelby inhomogeneous inclusion solution. The obtained micromechanical model is implemented via a UMAT routine within the explicit dynamic code LS-DYNA. The proposed micromechanical model has been applied successfully for the modelling of some biomechanics applications to estimate the mechanical properties of the bovine trabecular bone.

scholarly journals Micromechanical modeling of ductile fracture of human humerus

2020 ◽  
Vol 14 (2) ◽  
pp. 6952-6960
Author(s):  
J. Rahmoun ◽  
H. Naceur ◽  
P. Drazetic ◽  
C. Fontaine
Keyword(s):  
Ductile Fracture ◽  
Impact Load ◽  
Damage Model ◽  
Scale Model ◽  
Micromechanical Modeling ◽  
Formulation Development ◽  
Multi Scale ◽  
Proposed Model ◽  
Explicit Dynamic ◽  
Development And Validation

This paper deals with the formulation, development and validation of a newly developed micromechanical-based model for the modeling of the nonlinear ductile fracture of human humerus. The originality of the present works concerns the coupling between the micromechanical formulation based on the Mori-Tanaka homogenization scheme for cylindrical voids and the Marigo nonlinear ductile damage model based on the porosity growth. The proposed model was implemented as a User Material UMAT within the explicit dynamic software LS-DYNA and validated by numerical and experimental analysis conducted by a drop tower impact of human humerus. The outcome of the proposed multi-scale model appears to correctly predict the general trends observed experimentally via the good estimation of the ultimate impact load and the fracture patterns of the human humerus.

A Locking-Free Face-Based S-FEM via Averaging Nodal Pressure using 4-Nodes Tetrahedrons for 3D Explicit Dynamics and Quasi-statics

2018 ◽  
Vol 15 (06) ◽  
pp. 1850043 ◽  
Author(s):  
Chen Jiang ◽  
Xu Han ◽  
Zhi-Qian Zhang ◽  
G. R. Liu ◽  
Guang-Jun Gao
Keyword(s):  
Exhaust System ◽  
Computational Time ◽  
Dynamic Relaxation ◽  
Free Face ◽  
Explicit Dynamics ◽  
Tetrahedral Elements ◽  
Car Exhaust ◽  
Incompressible Solids ◽  
Explicit Dynamic ◽  
Nodal Pressure

A locking-free face-based S-FEM, combined with the Averaging Nodal Pressure (ANP) technique, is proposed to solve explicit dynamics of geometric nonlinear nearly-incompressible solids, using simplest linear tetrahedral elements (FS-FEM/ANP-T4). An explicit Adaptive Dynamic Relaxation (ADR) technique is also implemented for the analysis of quasi-static problems. Our studies have found that the proposed method has better accuracy and convergence compared to the standard FEM with ANP (FEM/ANP) and previous selective face-based and Node-based S-FEM (FS/NS-FEM). With the ADR, proposed method can reach the nonlinear quasi-static response much faster than the conventional explicit dynamic relaxation. No temporal instability is observed in FS-FEM/ANP-T4 in large deformation case. In addition, FS-FEM/ANP-T4 also equips the robustness against mesh distortion as FS/NS-FEM but uses less computational time. It has also been applied to solve a practical 3D problem, a rubber hanger for the car exhaust system. FS-FEM/ANP-T4 can be considered as an excellent numerical method other than FS/NS-FEM for simulating rubber-like materials.

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