Applied Sciences

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21 pages, 7736 KiB

Open AccessArticle

Heat Conduction and Cracking of Functionally Graded Materials Using an FDEM-Based Thermo-Mechanical Coupling Model

by Du Han, Hongwei Fan, Chengzeng Yan, Tie Wang, Yu Yang, Sajid Ali and Gang Wang

Appl. Sci. 2022, 12(23), 12279; https://doi.org/10.3390/app122312279 - 30 Nov 2022

Cited by 7 | Viewed by 1431

In this paper, the steady-state and transient heat transfer processes of functionally graded materials (FGMs) are analyzed using a coupled thermo-mechanical model in a GPU parallel multiphysics finite–discrete element software, namely MultiFracS. First, the coupled model to handle the heat transfer problem of [...] Read more.

In this paper, the steady-state and transient heat transfer processes of functionally graded materials (FGMs) are analyzed using a coupled thermo-mechanical model in a GPU parallel multiphysics finite–discrete element software, namely MultiFracS. First, the coupled model to handle the heat transfer problem of heterogeneous materials is verified. Then, the advantages and disadvantages of FGMs and composite materials in response to thermal shock loads are compared and the results indicate that FGMs can overcome extreme environments better than composite materials. Finally, the influence of the geometric distribution characteristics of the double-edge cracks in the gradient material plate on the crack propagation is analyzed. The simulation results show that the interaction between the cracks affects the crack propagation path under the thermal load. The inclination angle and spacing of double-edge cracks greatly influence crack propagation. Specifically, a larger inclination angle and spacing can lead to a smaller crack propagation angle. The approach in this paper provides a new quantitative tool for investigating the thermal, elastic, and cracking of functionally graded materials. Full article

(This article belongs to the Special Issue Multiphysics Modeling for Fracture and Fragmentation of Geomaterials)

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16 pages, 9896 KiB

Open AccessArticle

Investigation of the Mechanical Behaviour of Lingulid Sandstone Emphasizing the Influence from Pre-Existing Structural Defects—Part 2: Dynamic Testing and Numerical Modelling

by Pascal Forquin, Mahdi Saadati, Dominique Saletti, Bratislav Lukic, Federico Schiaffini, Kenneth Weddfelt and Per-Lennart Larsson

Appl. Sci. 2022, 12(22), 11621; https://doi.org/10.3390/app122211621 - 16 Nov 2022

Cited by 1 | Viewed by 1086

Abstract

In the present study, dynamic experiments are developed to investigate the induced damage modes when Lingulid sandstone is subjected to dynamic and impact loading. To do so, a series of spalling tests were carried out in order to investigate the material response at [...] Read more.

In the present study, dynamic experiments are developed to investigate the induced damage modes when Lingulid sandstone is subjected to dynamic and impact loading. To do so, a series of spalling tests were carried out in order to investigate the material response at high strain tension rates. This illustrates how structural defects influence the wave propagation in the tested sample, the loading-rate, and the resulting tensile strength. In addition, edge-on-impact tests were performed using both open and sarcophagus configurations. An ultra-high-speed image recording system is used in an open configuration for time-resolved visualisation of damage. The sarcophagus configuration gives the opportunity to visually compare the state of the cracking pattern prior to and after the test. This experimental work points-out that the pre-existing structural defects play a major role on impact loading. This is because the opening of cracks in mode I and the sliding of cracks in mode II are favoured, and by also restricting the fragmentation of the material caused by less critical defects. Next, a numerical simulation, only involving the so-called KST model, is presented to highlight the loading that would be applied to the target in the absence of structural defects. It demonstrates that in such a situation, a wide network of radial cracks would be expected. Finally, a numerical study involving the KST-DFH model illustrates the influence of a structural defect on the amount of damage generated in the target. Full article

(This article belongs to the Special Issue Multiphysics Modeling for Fracture and Fragmentation of Geomaterials)

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16 pages, 3806 KiB

Open AccessArticle

Investigation of the Mechanical Behaviour of Lingulid Sandstone Emphasising the Influence from Pre-Existing Structural Defects, Part 1: Model Identification Based on Static Experiments

by Pascal Forquin, Mahdi Saadati, Dominique Saletti, Bratislav Lukic, Frederico Schiaffini, Kenneth Weddfelt and Per-Lennart Larsson

Appl. Sci. 2022, 12(21), 10806; https://doi.org/10.3390/app122110806 - 25 Oct 2022

Cited by 2 | Viewed by 951

Abstract

A constitutive model able to describe both tensile damage and plastic deformation under confinement is a prerequisite to numerically simulate the behaviour of sandstone rock under an impact loading induced in a percussive drilling process. Therefore, model identification under both tensile and high [...] Read more.

A constitutive model able to describe both tensile damage and plastic deformation under confinement is a prerequisite to numerically simulate the behaviour of sandstone rock under an impact loading induced in a percussive drilling process. Therefore, model identification under both tensile and high confinement states is needed. In the present work, an experimental investigation was carried out in order to determine the mechanical properties of a sandstone rock for the purpose of advanced constitutive model identification. Different testing methods were used in quasistatic and dynamic loading regimes. This first part of the study is dedicated to static experiments, whereby three-point bend tests were first performed to evaluate the quasistatic tensile strength of the rock and its distribution by employing the Weibull statistics. Secondly, direct compression tests were conducted to evaluate the stiffness and strength in an unconfined condition. Afterwards, quasioedometric compression (QOC) tests were carried out in order to obtain the deviatoric and volumetric behaviours of the material as a function of the hydrostatic pressure (up to 375 MPa). In these QOC tests, the metallic confinement cell was instrumented with strain gauges to deduce the state of the stress and strain within the sample. A linear volumetric response along with a continuous increase of strength with the level of hydrostatic pressure was observed. This experimental work points out that, under unconfined loading (three-point bending and uniaxial compression), pre-existing structural defects play a major role leading to a highly scattered behaviour in terms of sample stiffness and ultimate applied load. On the other hand, under high confinement levels (QOC tests), beyond the nonlinear response of the curve foot, the influence from structural defects was observed to be small. Full article

(This article belongs to the Special Issue Multiphysics Modeling for Fracture and Fragmentation of Geomaterials)

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24 pages, 10834 KiB

Open AccessArticle

Research on the Dynamic Damage Properties and Determination of the Holmquist–Johnson–Cook Model Parameters for Sandstone

by Shufeng Liang, Shijun Hou and Shuaifeng Wu

Appl. Sci. 2022, 12(16), 8366; https://doi.org/10.3390/app12168366 - 21 Aug 2022

Cited by 2 | Viewed by 1522

Abstract

During blasting in engineering construction, the surrounding rock becomes unstable and is damaged under the impacts of multiple low-amplitude stress waves. It is of great practical significance to understand the damage evolution characteristics and the attenuation of the mechanical properties of rocks subjected [...] Read more.

During blasting in engineering construction, the surrounding rock becomes unstable and is damaged under the impacts of multiple low-amplitude stress waves. It is of great practical significance to understand the damage evolution characteristics and the attenuation of the mechanical properties of rocks subjected to multiple stress waves. Single impact and repeated impact tests for sandstone were carried out using a split Hopkinson pressure bar (SHPB) loading system. The single impact test results showed that the sandstone materials were strain-rate-dependent, and the dynamic constitutive curve could be divided into four stages, namely the linear elastic stage, the new crack formation stage, the plastic strengthening stage and the unloading stage. The failure pattern mostly indicated splitting tensile failure, and the impact damage threshold was 45 J. The relationship between the damage and stress wave amplitude was D = 0.0029·exp\({\boxed{f_{()}}}\)(5.4127•σ/76.13) − 0.0504. The repeated impact test results showed that the dynamic compressive strength and the dynamic elastic modulus decreased, while the failure strain increased gradually as the number of impacts (n) increased. The sandstone specimen under repeated impacts had only one fracture surface compared with the single impact failure pattern. The cumulative damage presented the development form of ‘rapid rise–steady development–rapid rise’, and the damage evolution law could be expressed by D = 0.265 − 0.328·ln⁡⁡⁡\({\boxed{f_{()}}}\)(ln13.989/n). Finally, a set of methods to determine the Holmquist–Johnson–Cook (HJC) model parameters for sandstone was proposed based on a single impact test, repeated impact test, uniaxial compression test and triaxial compression test. The numerical simulation results of the SHPB test showed that the dynamic constitutive curves of sandstone were in good agreement with the experimental results. Full article

(This article belongs to the Special Issue Multiphysics Modeling for Fracture and Fragmentation of Geomaterials)

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22 pages, 48477 KiB

Open AccessArticle

Numerical Study of Rock Damage Mechanism Induced by Blasting Excavation Using Finite Discrete Element Method

by Wenhui Ke, Xun Wang, Chengzeng Yan and Chuyin Qiao

Appl. Sci. 2022, 12(15), 7517; https://doi.org/10.3390/app12157517 - 26 Jul 2022

Cited by 5 | Viewed by 1717

Abstract

In this paper, the mechanism of rock damage induced by blasting excavation is numerically studied by using an FDEM-based multiphysics fracture analysis software, MultiFracS. Based on the drainage channel project of Guanggu 1st Road to Gaoxin 4th Road, a numerical model considering the [...] Read more.

In this paper, the mechanism of rock damage induced by blasting excavation is numerically studied by using an FDEM-based multiphysics fracture analysis software, MultiFracS. Based on the drainage channel project of Guanggu 1st Road to Gaoxin 4th Road, a numerical model considering the near-field fracture process is established to study the influence of a millisecond delay and construction technology on the blasting excavation. Firstly, the double side drift method model is established to analyze the influence of different millisecond delays on the peak blasting vibration velocity. Then, the rock fracture process of the surrounding rock around the blast holes under the blasting excavation construction technology of the double side drift method, the reserved core soil method, and the CRD method is studied, respectively. The numerical simulation results show that the mainshock phases of the blasting vibration velocity waveform generated by different bores overlap when the millisecond delay is small. With the increase in the millisecond delay, the mainshock phase is gradually separated, and the superposition effect of the blasting vibration is weakened. When the millisecond delay is greater than 40 ms, the peak blasting vibration velocity is not affected by the millisecond delay. In the three kinds of blasting excavation construction technologies, the double side drift method has a better effect on the deformation and the fracture control of the surrounding rock. The optimal millisecond delay and the rock fracture evolution process of the surrounding rock around blast holes with different blasting excavation construction technologies are obtained. Full article

(This article belongs to the Special Issue Multiphysics Modeling for Fracture and Fragmentation of Geomaterials)

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18 pages, 4364 KiB

Open AccessArticle

A Study on the Freeze–Thaw Damage and Deterioration Mechanism of Slope Rock Mass Based on Model Testing and Numerical Simulation

by Jiebing Zhu, Dongdong Xu, Bin Wang and Cong Li

Appl. Sci. 2022, 12(13), 6545; https://doi.org/10.3390/app12136545 - 28 Jun 2022

Cited by 2 | Viewed by 1424

Abstract

Engineering rock mass in cold regions has obvious freeze–thaw damage as a result of extreme differences in temperature, rainfall, snow, and other factors, which is one of the main causes of frequent geological disasters. Therefore, it is important to investigate the deterioration mechanism [...] Read more.

Engineering rock mass in cold regions has obvious freeze–thaw damage as a result of extreme differences in temperature, rainfall, snow, and other factors, which is one of the main causes of frequent geological disasters. Therefore, it is important to investigate the deterioration mechanism and evolution laws of rock mass freeze–thaw damage. Considering a hydropower station’s left bank slope in a cold region, model testing and numerical testing of slope rock mass failure under freeze–thaw conditions are here carried out by developing a generalized model. The results reveal that heat is transmitted from the outside to the inside of the slope and that the rate of temperature change varies with depth; the frost-heave force causes tensile cracks in the rock mass, with crack propagation taking the form of a circular arc; the presence of an original structural plane influences the propagation direction of the frost-heave crack, whereas the freezing rate of the fissure water influences the amplitude and growth rate of the frost-heave force. Additionally, a novel method of measuring frost-heave force is proposed. The largest frost-heave force caused by water–ice phase change is 19.3 kPa, which is equivalent to 3.17 MPa of the actual slope. Full article

(This article belongs to the Special Issue Multiphysics Modeling for Fracture and Fragmentation of Geomaterials)

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21 pages, 5535 KiB

Open AccessArticle

Calculation Method of the Blasting Throwing Energy and Its Variation Affected by the Burden

by Yonghui Huang, Zixiang Zhao, Zhiyu Zhang, Jiguo Zhou, Hongchao Li and Yanlin Li

Appl. Sci. 2022, 12(13), 6524; https://doi.org/10.3390/app12136524 - 27 Jun 2022

Cited by 1 | Viewed by 2501

Abstract

Precise control of casting velocity and effective throwing kinetic energy conversion efficiency in blasting engineering are challenges. To provide a theoretical basis and reference for the implementation plan and fine construction of the cast blasting project, we study the problems of casting velocity [...] Read more.

Precise control of casting velocity and effective throwing kinetic energy conversion efficiency in blasting engineering are challenges. To provide a theoretical basis and reference for the implementation plan and fine construction of the cast blasting project, we study the problems of casting velocity and energy consumption ratio of broken rock under the impact load of explosions in this manuscript. The calculation methods of casting velocity and throwing energy of broken rock under two blasting modes of spherical charge and cylindrical charge are established by using the theory of dimensional analysis and rock breaking by blasting. A large number of model tests are carried out by using high-speed photography. The results indicate that the casting velocity of broken rock after explosive initiation has two evident stages: instantaneous acceleration to a certain value and subsequent fluctuation; the velocity presents an ordinary distribution law with the step height, and the fitting correlation of high-speed photography results is more than 91%. With the minimum burden increasing from 0.12 m to 0.2 m, the energy consumption decreases from 1306.88 J to 747.49 J and the proportion of energy consumption decreases from 14.77% to 8.45%. Full article

(This article belongs to the Special Issue Multiphysics Modeling for Fracture and Fragmentation of Geomaterials)

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19 pages, 4038 KiB

Open AccessArticle

Peridynamics for Fracture Analysis of Reflective Cracks in Semi-Rigid Base Asphalt Pavement

by Zhichuang Shi, Jinchao Yue, Lingling Xu and Xiaofeng Wang

Appl. Sci. 2022, 12(7), 3486; https://doi.org/10.3390/app12073486 - 30 Mar 2022

Cited by 7 | Viewed by 2074

Abstract

Reflective cracking is one of the major forms of deterioration in semi-rigid base asphalt pavements. It is, therefore, very important to have a correct understanding of the internal crack propagation mechanism of asphalt pavement to propose the most effective remedial solution(s), which corresponds [...] Read more.

Reflective cracking is one of the major forms of deterioration in semi-rigid base asphalt pavements. It is, therefore, very important to have a correct understanding of the internal crack propagation mechanism of asphalt pavement to propose the most effective remedial solution(s), which corresponds to that mode of failure. In this study, two-dimensional asphalt pavement layered models are first established by modifying the peridynamics theory. Then, the influence of asphalt overlay thickness and load form on reflective crack propagation is explored. On this basis, the influence of friction between the tire and road surface on reflective crack propagation is analyzed. The results show that increasing the thickness of the asphalt overlay can inhibit reflective crack propagation, and the friction force accelerates reflective crack propagation when the direction of friction is the same as that of reflective crack propagation; otherwise, it inhibits reflective crack propagation. Additionally, the most unfavorable load position is the asymmetrical load when the vehicle is far from the reflective crack. Full article

(This article belongs to the Special Issue Multiphysics Modeling for Fracture and Fragmentation of Geomaterials)

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