The Effect of Confining Pressures on Rock Fracturing under Dynamic Loads

2011 ◽  
Vol 320 ◽  
pp. 255-258
Author(s):  
Zhe Ming Zhu ◽  
Zhi Rong Zhou ◽  
Yong Qian Li ◽  
Ye Xue Li
Keyword(s):  
Numerical Model ◽  
Material Properties ◽  
Rock Sample ◽  
Equations Of State ◽  
Linear Equations ◽  
Dynamic Loads ◽  
Rock Fracturing ◽  
Mining Depth ◽  
Confining Pressures ◽  
Dynamic Fracturing

In order to investigate the effect of confining pressures on rock dynamic fracturing under dynamic loads, a 2D finite difference dynamic numerical model for a circular rock sample with a single centralized borehole is developed. According to the material properties and loading conditions, shock and linear equations of state are combined and applied to the rock material in this model. A modified principal stress failure criterion is applied to determining material status. It is shown that as the increase of mining depth, the extent of blasting-induced damage of rock increases significantly.

Numerical Prediction of Rock Fracturing During the Process of Excavation

2012 ◽  
pp. 225-237 ◽  
Author(s):  
Zhangtao Zhou ◽  
Zheming Zhu ◽  
XinXing Jin ◽  
Hao Tang
Keyword(s):  
Equation Of State ◽  
Numerical Model ◽  
Failure Criterion ◽  
Material Properties ◽  
Igneous Rock ◽  
Surrounding Rock ◽  
Rock Blasting ◽  
Rock Fracturing ◽  
Fracturing Process ◽  
Blasting Excavation

During the process of excavation, blasting can induce cracking inside the surrounding rock. Considering the effects of material properties and loading conditions, a rock blasting excavation model with two successive excavation steps was developed through the use of AUTODYN code. Four kinds of equation of state (EOS), linear, shock, JWL, and compaction were applied to the materials employed in this numerical model. A modified principal stress failure criterion was applied to determining material statuses, and TNT explosive and a relatively homogeneous igneous rock, diorite, were used in this numerical model. By using this numerical model, rock fracturing process during blasting excavation was simulated, and rock fracturing process during two successive excavations is presented.

Numerical Prediction of Rock Fracturing During the Process of Excavation

2010 ◽  
Vol 1 (2) ◽  
pp. 12-23 ◽  
Author(s):  
Zhangtao Zhou ◽  
Zheming Zhu ◽  
XinXing Jin ◽  
Hao Tang
Keyword(s):  
Equation Of State ◽  
Numerical Model ◽  
Failure Criterion ◽  
Material Properties ◽  
Igneous Rock ◽  
Surrounding Rock ◽  
Rock Blasting ◽  
Rock Fracturing ◽  
Fracturing Process ◽  
Blasting Excavation

During the process of excavation, blasting can induce cracking inside the surrounding rock. Considering the effects of material properties and loading conditions, a rock blasting excavation model with two successive excavation steps was developed through the use of AUTODYN code. Four kinds of equation of state (EOS), linear, shock, JWL, and compaction were applied to the materials employed in this numerical model. A modified principal stress failure criterion was applied to determining material statuses, and TNT explosive and a relatively homogeneous igneous rock, diorite, were used in this numerical model. By using this numerical model, rock fracturing process during blasting excavation was simulated, and rock fracturing process during two successive excavations is presented.

Thermal Cycling Simulation during Remelting Process of the Steel ASTM A743-CA6NM

2014 ◽  
Vol 1082 ◽  
pp. 100-105
Author(s):  
Camila Almeida Martins ◽  
Jhon Jairo Ramirez-Behainne
Keyword(s):  
Numerical Model ◽  
Thermal Cycling ◽  
Material Properties ◽  
Three Dimensional ◽  
Fusion Line ◽  
Maximum Deviation ◽  
Experimental Measurements ◽  
Ansys Fluent ◽  
Simplifying Assumptions ◽  
Volume Method

This study aimed to model numerically the thermal cycling resulting from the steel ASTM A743-CA6NM remelting process. The problem was solved with the support of the commercial software ANSYS / FLUENT ® 14.5 for the three-dimensional case using the finite volume method. The following simplifying assumptions were adopted: heat loss by natural convection, absence of radiation, no phase change, concentrated heat source, and thermophysical properties independent of temperature. The results were analyzed for two different current intensities: 90A and 130A, and compared with experimental measurements. The peak temperatures of the thermocouples near the fusion line for the current of 130A were well represented by the numerical model, with a maximum deviation of 9.62%. In the case of the more remote thermocouples from the fusion line, the best results were obtained for the current of 90A, not exceeding 5% of deviation. In general, it was found that the tested body is heated faster than in simulations. This can be considered as a consequence of the simplification in material properties, which were assumed constants with temperature. The results of this study demonstrate that, given the adopted simplifications, the numerical model was able to satisfactorily reproduce the experimentally measured thermal cycles.

Impact Localization on a Composite Plate With Unknown Material Properties Using PWAS Transducers and Wavelet Transform

2017 ◽  
Author(s):  
Asaad Migot ◽  
Victor Giurgiutiu
Keyword(s):  
Wavelet Transform ◽  
Nonlinear Equations ◽  
Material Properties ◽  
Composite Plate ◽  
Linear Equations ◽  
Active Sensors ◽  
Piezoelectric Wafer Active Sensors ◽  
Piezoelectric Wafer ◽  
The Impact ◽  
Impact Localization

In this work, an impact experiment on a composite plate with unknown material properties (its group velocity profile is unknown) is implemented to localize the impact points. A pencil lead break is used to generate acoustic emission (AE) signals which are acquired by six piezoelectric wafer active sensors (PWAS). These sensors are distributed with a particular configuration in two clusters on the plate. The time of flight (TOF) of acquired signals is estimated at the starting points of these signals. The continuous wavelet transform (CWT) of received signals are calculated with AGU Vallen wavelet program to get the accurate values of the TOF of these signals. Two methods are used for determining the coordinates of impact points (localization the impact point). The first method is the new technique (method 1) by Kundu. This technique has two linear equations with two unknowns (the coordinate of AE source point). The second method is the nonlinear algorithm (method 2). This algorithm has a set of six nonlinear equations with five unknowns. Two MATLAB codes are implemented separately to solve the linear and nonlinear equations. The results show good indications for the location of impact points in both methods. The location errors of calculated impact points are divided by constant distance to get independent percentage errors with the site of the coordinate.

scholarly journals A general existence result for isothermal two-phase flows with phase transition

2019 ◽  
Vol 16 (04) ◽  
pp. 595-637
Author(s):  
Maren Hantke ◽  
Ferdinand Thein
Keyword(s):  
Phase Transition ◽  
Euler Equations ◽  
Equations Of State ◽  
Linear Equations ◽  
Two Phase Flows ◽  
Kinetic Relation ◽  
Two Phase ◽  
Uniqueness Results ◽  
Wide Range ◽  
Isothermal Euler Equations

Liquid–vapor flows with phase transitions have a wide range of applications. Isothermal two-phase flows described by a single set of isothermal Euler equations, where the mass transfer is modeled by a kinetic relation, have been investigated analytically in [M. Hantke, W. Dreyer and G. Warnecke, Exact solutions to the Riemann problem for compressible isothermal Euler equations for two-phase flows with and without phase transition, Quart. Appl. Math. 71(3) (2013) 509–540]. This work was restricted to liquid water and its vapor modeled by linear equations of state. The focus of this work lies on the generalization of the primary results to arbitrary substances, arbitrary equations of state and thus a more general kinetic relation. We prove existence and uniqueness results for Riemann problems. In particular, nucleation and cavitation are discussed.

scholarly journals Renovation and Strengthening of Wooden Beams With CFRP Bands Including the Rheological Effects

2016 ◽  
Vol 22 (3) ◽  
pp. 93-102 ◽  
Author(s):  
Krzysztof Kula ◽  
Tomasz Socha
Keyword(s):  
Numerical Model ◽  
Linear Equations ◽  
Rheological Models ◽  
Work Analysis ◽  
Calculation Results

Abstract The paper presents a work analysis of wooden beams reinforced with glued composite bands from the top and resin inclusions, taking into account the rheology of materials. The paper presents numerical model of the multimaterial beam work including rheological phenomena described by linear equations of viscoelasticity. For the construction of this model one used MES SIMULIA ABAQUS environment in which were prepared its own procedures containing rheological models. The calculation results were compared with the literature data. One has done an analysis of the advisability of the use of CFRP reinforcements bands in terms of rheological phenomena.

Numerical determination of pressure-dependent effective thermal conductivity in Berea sandstone

2021 ◽  
Author(s):  
Mirko Siegert ◽  
Marcel Gurris ◽  
Erik Hans Saenger
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Numerical Model ◽  
Effective Thermal Conductivity ◽  
Rock Sample ◽  
Rock Physics ◽  
Contact Phase ◽  
Data Set ◽  
Computed Tomography Images ◽  
Thermal Conductivities

<p>Within the scope of the present work, the pressure-dependent effective thermal conductivity of rock samples is simulated. Our workflow can be assigned to the field of digital rock physics. In a first step, a 3D micro-CT scan of a rock sample is taken. Subsequently, the resulting greyscale images are analysed and segmented depending on the occurring phases. Based on this data set, a computational mesh is created and the corresponding thermal conductivities are assigned to each phase. Finally the numerical simulations can be carried out.<br>For the representation of the pressure dependency we use the approach proposed by Saenger [1]. By making use of the watershed algorithm, boundaries between the individual grains of the rock sample are detected and assigned to an artificial contact phase. In the course of several simulations, the thermal conductivity of the contact phase is continuously increased. Starting with the thermal conductivity of the pore phase and ending with the thermal conductivity of the grain phase. A linear correlation is used to match the thermal conductivity of the contact phase with the pressure of a given experimental data set. This enables a direct comparison between simulation and measurement.<br>In a further step, the numerical model is calibrated to optimise the agreement between experimental data and simulation results. In particular, starting from two calibration points of the experimental data set, an adjustment of the thermal conductivities in the numerical model is carried out. While the thermal conductivity of the pore phase is held constant during the whole calibration process, thermal conductivities of the grain and contact phase are adjusted.</p><p>References<br>[1] Saenger et al. 2016. Analysis of high-resolution X-ray computed tomography images of Bentheim sandstone under elevated confining pressures. Geophysical Prospecting, 64(4), 848–859.</p><p> </p>

Influence of the Bolt Material Properties on the Ultimate Capacity of End Plate Bolted Joint Subjected to Column Loss

2021 ◽  
Vol 885 ◽  
pp. 133-139
Author(s):  
Roberto Tartaglia ◽  
Alessia Campiche
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Material Properties ◽  
Finite Element Simulations ◽  
Material Strength ◽  
Bolted Joint ◽  
Ultimate Capacity ◽  
Catenary Action ◽  
Beneficial Effects ◽  
End Plate

This paper investigates the performance of extended stiffened end-plate bolted beam-to-column joints subjected a column loss scenario by means of finite element simulations. An advanced numerical model was developed, and its effectiveness was validated against the experimental results. The influence of the bolt strengthening on the column loss action was investigated changing the grade of bolts. The results showed that the joint performance under column loss scenario are deeply related to the development of the catenary action that depends from the connection ductility; therefore increasing the bolt material strength will provide beneficial effects on the joint capacity under the column loss.

A high-pressure technique for determining the microcrack porosities of damaged brittle materials

1995 ◽  
Vol 73 (5-6) ◽  
pp. 330-337 ◽  
Author(s):  
Douglas R. Schmitt ◽  
Yong Yi Li
Keyword(s):  
High Pressure ◽  
Rock Sample ◽  
Vertical Direction ◽  
Total Porosity ◽  
Stress Relief ◽  
Tensor Form ◽  
Substantial Fraction ◽  
The Earth ◽  
Confining Pressures ◽  
Solid Compounds

The microcrack porosity of a damaged brittle material is found by accurately measuring the compressibilities under a hydrostatic pressure to 200 MPa. Crack apertures are sensitive to the stress applied normal to their plane and, as a result, at low confining pressures the bulk of the strain records the response of the progressive closure of these cracks. At higher pressures when much of the microcrack porosity is closed the observed strains are nearly the same as that expected for the solid compounds within the rock. The higher pressure response may then be used to estimate the expected solid strains that are removed from those observed to leave that portion of the strain due to microcrack porosity. This procedure differs from that of other workers who either ignore the portion of the strain due to intrinsic compression or account for it indirectly by taking the derivative of the observed strain curves. The final results may be analyzed in tensor form to show possible anisotropies in microcrack orientations within a given sample. An example of the experiment on a rock sample that was damaged during removal from the earth by drilling yielded a microcrack porosity of 0.79%, which was a substantial fraction of the total porosity near 5%. At 200 MPa, the principal crack strains had magnitudes of 1.86, 2.61, and 3.39 mstrains; the orientation of this last and greatest magnitude strain differing from the vertical direction by approximately 20°. This suggests that the planes of the predominant family of microcracks within the test piece were subhorizontal. This suggests that a portion of the microcracks result from drilling-induced damage and not solely from stress relief of the sample upon removal from the earth.

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