Hysteresis characteristics of oxidation-thermodynamic for residual coal in goaf under uniaxial stress

Fuel ◽  
2021 ◽  
Vol 306 ◽  
pp. 121750
Author(s):  
Yong-liang Xu ◽  
Ze-jian Liu ◽  
Lan-yun Wang ◽  
Zhi-guang Lv ◽  
Jin-dong Wu ◽  
...  
Keyword(s):  
Uniaxial Stress ◽  
Residual Coal ◽  
Hysteresis Characteristics

scholarly journals Influence Mechanism of Nitrogen Injection Into Closed Fire Zone On the Re-Ignition For Residual Coal in Goaf

2021 ◽  
Author(s):  
Yong-liang XU ◽  
Ze-jian LIU ◽  
Xing-lin WEN ◽  
Lan-yun Wang ◽  
Zhi-guang LV ◽  
...  
Keyword(s):  
Functional Groups ◽  
Uniaxial Stress ◽  
Filling Material ◽  
Nitrogen Injection ◽  
Fire Zone ◽  
Ignition Mechanism ◽  
Mine Fires ◽  
Ignition Characteristics ◽  
Temperature Programmed ◽  
Residual Coal

Abstract Coal is the foundation of Chinese energy and economic structure, and the unsealing of coal mine fires would cause a great risk of coal re-ignition. The uniaxial compression equipped with a temperature-programmed (UCTP) device was built to explore the influence of pressure-bearing state on the re-ignition characteristics of residual coal. The Scanning Electron Microscope (SEM), Synchronous Thermal Analyzer (STA) and Fourier Transform Infrared Absorption Spectrometer (FTIR) was applied to investigate the microscopic structure and thermal effect of the coal samples. Moreover, the microscopic effect of uniaxial stress on coal re-ignition was revealed, and the re-ignition mechanism was also obtained. As the uniaxial stress increases, the number, depth and length of the fractures in the pretreated coal increase, and the filling material increases. The application of uniaxial stress causes the thermal conductivity to change periodically, which enhances the heat transfer inhibition effect of nitrogen and prolongs the oxidation exothermic stage. The content of oxygen-containing functional groups has a high correlation with apparent activation energy, and coal samples at 6 MPa are more likely to re-ignition when the fire zone is unsealed. Uniaxial stress controls the re-ignition mechanism by changing the structure of fractures and pores. The side chains and functional groups in the coal structure are easier to break under thermal-stress coupling. The higher the ·OH content, the more difficult it is to re-ignition. The research results have laid a solid theoretical foundation for the safe unsealing of coal field fire areas, tightened the common bond between the actual industry and the experimental theory in the closed fire area, and provided theoretical guidance for preventing coal re-ignition.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

On the correlation “powder dispersivity – hysteresis characteristics” for (Sm,Zr)(Co,Cu,Fe)z-based magnets

2018 ◽  
pp. 47-52
Author(s):  
N.A. Dormidontov ◽  
◽  
G.S. Burkhanov ◽  
N.B. Kolchugina ◽  
A.G. Dormidontov ◽  
...  
Keyword(s):  
Hysteresis Characteristics

Effect Analysis of Nitrogen Injection on the Variation of “Oxidation Zone” in Coal Mine Gob Based on Numerical Simulation

2016 ◽  
Vol 9 (1) ◽  
pp. 47-54
Author(s):  
Jing Shen ◽  
Mingran Chang
Keyword(s):  
Numerical Simulation ◽  
Coal Mine ◽  
Heat Dissipation ◽  
Spontaneous Combustion ◽  
Oxidation Zone ◽  
Effect Analysis ◽  
Mine Fire ◽  
Nitrogen Injection ◽  
The Difference ◽  
Residual Coal

One of the main reasons for coal mine fire is spontaneous combustion of residual coal in gob. As the difference of compaction degree of coal and rock, the underground gob can be considered as a porous medium and divided into “three zones” in accordance with the criteria. The “three zones” are “heat dissipation zone”, “oxidation zone” and “choking zone”, respectively. Temperature programming experiments are taken and numerical simulation with obtained experimental data is utilized to analyze the distribution of “three zones” in this paper. Different width and depth of “oxidation zone” are obtained when the inlet air velocity is changed. As the nitrogen injection has inhibition effect on spontaneous combustion of residual coal in gob, nitrogen is injected into the gob. The widths of “oxidation zone” are compared before and after nitrogen injection. And ultimately the optimum location and volume of nitrogen injection are found out.

scholarly journals Hysteresis Modeling and Compensation of Fast Steering Mirrors with Hysteresis Operator Based Back Propagation Neural Networks

Micromachines ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 732
Author(s):  
Kairui Cao ◽  
Guanglu Hao ◽  
Qingfeng Liu ◽  
Liying Tan ◽  
Jing Ma
Keyword(s):  
Neural Network ◽  
Back Propagation ◽  
Hysteresis Model ◽  
Cooperative Movement ◽  
Hysteresis Operator ◽  
The Neural Network ◽  
Hysteresis Nonlinearity ◽  
Hysteresis Modeling ◽  
Hysteresis Characteristics ◽  
Inverse Hysteresis

Fast steering mirrors (FSMs), driven by piezoelectric ceramics, are usually used as actuators for high-precision beam control. A FSM generally contains four ceramics that are distributed in a crisscross pattern. The cooperative movement of the two ceramics along one radial direction generates the deflection of the FSM in the same orientation. Unlike the hysteresis nonlinearity of a single piezoelectric ceramic, which is symmetric or asymmetric, the FSM exhibits complex hysteresis characteristics. In this paper, a systematic way of modeling the hysteresis nonlinearity of FSMs is proposed using a Madelung’s rules based symmetric hysteresis operator with a cascaded neural network. The hysteresis operator provides a basic hysteresis motion for the FSM. The neural network modifies the basic hysteresis motion to accurately describe the hysteresis nonlinearity of FSMs. The wiping-out and congruency properties of the proposed method are also analyzed. Moreover, the inverse hysteresis model is constructed to reduce the hysteresis nonlinearity of FSMs. The effectiveness of the presented model is validated by experimental results.

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