• Title/Summary/Keyword: Dynamic fracture process analysis

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Dynamic fracture instability in brittle materials: Insights from DEM simulations

  • Kou, Miaomiao;Han, Dongchen;Xiao, Congcong;Wang, Yunteng
    • Structural Engineering and Mechanics
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    • v.71 no.1
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    • pp.65-75
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    • 2019
  • In this article, the dynamic fracture instability characteristics, including dynamic crack propagation and crack branching, in PMMA brittle solids under dynamic loading are investigated using the discrete element method (DEM) simulations. The microscopic parameters in DEM are first calibrated using the comparison with the previous experimental results not only in the field of qualitative analysis, but also in the field of quantitative analysis. The calibrating process illustrates that the selected microscopic parameters in DEM are suitable to effectively and accurately simulate dynamic fracture process in PMMA brittle solids subjected to dynamic loads. The typical dynamic fracture behaviors of solids under dynamic loading are then reproduced by DEM. Compared with the previous experimental and numerical results, the present numerical results are in good agreement with the existing ones not only in the field of qualitative analysis, but also in the field of quantitative analysis. Furthermore, effects of dynamic loading magnitude, offset distance of the initial crack and initial crack length on dynamic fracture behaviors are numerically discussed.

Experimental and Numerical Study on the Dynamic Fracture Processes of PMMA Block by NRC Vapor Pressure Fracture Agent (NRC 증기압 암석 파쇄제에 의한 PMMA 블록의 동적 파괴 과정에 관한 실험 및 수치해석적 연구)

  • Gyeongjo Min
    • Journal of Korean Society of Disaster and Security
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    • v.16 no.1
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    • pp.91-103
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    • 2023
  • This study aims to investigate the dynamic fracture characteristics of rocks and rock-like materials subjected to the Nonex Rock Cracker (NRC), a vapor pressure crushing agent that produces vapor pressure by instantaneously vaporizing a liquid mixture crystallized through the thermite reaction. Furthermore, the study seeks to develop an analytical technique for predicting the fracture pattern. A dynamic fracture test was performed on a PMMA block, an artificial brittle material, using the NRC. High-speed cameras and dynamic pressure gauges were employed to capture the moment of vapor pressure generation and measure the vapor pressure-time history, respectively. The 2-dimensional Dynamic Fracture Process Analysis (2D DFPA) was used to simulate the fracture process caused by the vapor pressure, with the applied pressure determined based on the vapor pressure-time history. The proposed analytical method was used to examine various fracture patterns with respect to granite material and high-performance explosives.

Development and Validation of the GPU-based 3D Dynamic Analysis Code for Simulating Rock Fracturing Subjected to Impact Loading (충격 하중 시 암석의 파괴거동해석을 위한 GPGPU 기반 3차원 동적해석기법의 개발과 검증 연구)

  • Min, Gyeong-Jo;Fukuda, Daisuke;Oh, Se-Wook;Cho, Sang-Ho
    • Explosives and Blasting
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    • v.39 no.2
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    • pp.1-14
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    • 2021
  • Recently, with the development of high-performance processing devices such as GPGPU, a three-dimensional dynamic analysis technique that can replace expensive rock material impact tests has been actively developed in the defense and aerospace fields. Experimentally observing or measuring fracture processes occurring in rocks subjected to high impact loads, such as blasting and earth penetration of small-diameter missiles, are difficult due to the inhomogeneity and opacity of rock materials. In this study, a three-dimensional dynamic fracture process analysis technique (3D-DFPA) was developed to simulate the fracture behavior of rocks due to impact. In order to improve the operation speed, an algorithm capable of GPGPU operation was developed for explicit analysis and contact element search. To verify the proposed dynamic fracture process analysis technique, the dynamic fracture toughness tests of the Straight Notched Disk Bending (SNDB) limestone samples were simulated and the propagation of the reflection and transmission of the stress waves at the rock-impact bar interfaces and the fracture process of the rock samples were compared. The dynamic load tests for the SNDB sample applied a Pulse Shape controlled Split Hopkinson presure bar (PS-SHPB) that can control the waveform of the incident stress wave, the stress state, and the fracture process of the rock models were analyzed with experimental results.

Study on the Precise Controlling of Fracture Plane in Smooth Blasting Method (SB발파에서 파단면 제어의 고도화에 관한 연구)

  • Cho, Sang-Ho;Jeong, Yun-Young;Kim, Kwang-Yum;Kaneko, Katsuhiko
    • Tunnel and Underground Space
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    • v.19 no.4
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    • pp.366-372
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    • 2009
  • Recently, in order to achieve smooth fracture plane and minimize the excavation damage zone in rock blasting, controlled blasting methods which utilize new technologies such as electronic delay detonator (EDD) and a notched charge hole have been suggested. In this study, smooth blastings utilizing three wing type notched charge holes are simulated to investigate the influence of explosive initial density on the resultant fracture plane and damage zone using dynamic fracture process analysis (DFPA) code. Finally, based on the dynamic fracture process analyses, novel smooth blasting method, ED-Notch SB (Electronic Detonator Notched Charge Hole Smooth Blasting) is suggested.

A smeared crack model for seismic failure analysis of concrete gravity dams considering fracture energy effects

  • Hariri-Ardebili, Mohammad Amin;Seyed-Kolbadi, Seyed Mahdi;Mirzabozorg, Hasan
    • Structural Engineering and Mechanics
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    • v.48 no.1
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    • pp.17-39
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    • 2013
  • In the present paper, a coaxial rotating smeared crack model is proposed for mass concrete in three-dimensional space. The model is capable of applying both the constant and variable shear transfer coefficients in the cracking process. The model considers an advanced yield function for concrete failure under both static and dynamic loadings and calculates cracking or crushing of concrete taking into account the fracture energy effects. The model was utilized on Koyna Dam using finite element technique. Dam-water and dam-foundation interactions were considered in dynamic analysis. The behavior of dam was studied for different shear transfer coefficients considering/neglecting fracture energy effects. The results were extracted at crest displacement and crack profile within the dam body. The results show the importance of both shear transfer coefficient and the fracture energy in seismic analysis of concrete dams under high hydrostatic pressure.

Influence of the Initiation Error of the Delay Detonator on the Rock Fracture Process in Smooth Blasting (SB발파에서 지발뇌관의 기폭초시오차가 암반파괴과정에 미치는 영향)

  • 조상호;양형식;금자승비고
    • Tunnel and Underground Space
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    • v.14 no.2
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    • pp.121-132
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    • 2004
  • Dynamic fracture processes of rock were analyzed to investigate the influence of the initiation error of the delay detonator in smooth blasting. The analysis models for the smooth blasting considered two blast geometries with three charge holes, and the simultaneous initiations without initiation error, with the initiation error of electronic delay detonator and with the initiation error of pyrotechnically delay detonator(DS detonator) were applied to the charge holes. In order to examine the effect of electronic and DS initiation detonator on the smooth blasting, the fracture process results were analyzed statistically.

Numerical Study on Ground Vibration Reduction and Fragmentation in a Controlled Blasting Utilizing Directional U Shape Charge Holder (U형 장약홀더를 이용한 발파공법에서 지반진동 저감특성 및 파괴효율에 관한 수치해석적 연구)

  • Kim, Hyon-Soo;Baek, Beom-Hyun;Oh, Se-Wook;Han, Dong-Hun;Cho, Sang-Ho
    • Explosives and Blasting
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    • v.34 no.1
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    • pp.11-18
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    • 2016
  • It is necessary to minimize ground vibration and noise due to blasting work in urban environment. The blast induced ground vibration and noise are generally generated by a portion of detonation energy, where most of the energy is utilized for rock breakage and movement of rock mass. Recently a blast method utilizing U-shaped steel charge holder was suggested to reduce the ground vibration without decreasing destructive power toward the free surface. In this study, single hole blasting utilizing U-shaped steel charge holder were simulated and the stress waves caused by the detonation of explosives were monitored using AUTODYN software. In order to examine the fragmentation efficiency of the U-shaped steel charge holder, one free face blasting models which adapt the blast induced stress waves were simulated by dynamic fracture process analysis (DFPA) code. In addition, the general blasting models were also simulated to investigate the fragmentation effectiveness of the U-shaped steel charge holder in rock blasting.

Determining Parameters of Dynamic Fracture Process Analysis(DFPA) Code to Simulate Radial Tensile Cracks in Limestone Blast (석회암 내 방사상 발파균열을 예측하기 위한 동적파괴과정 해석법의 입력물성 결정법에 관한 연구)

  • Kim, Hyon-Soo;Kang, Hyeong-Min;Jung, Sang-Sun;Kim, Seung-Kon;Cho, Sang-Ho
    • Explosives and Blasting
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    • v.31 no.2
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    • pp.6-13
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    • 2013
  • Recently, complaints or environmental problems caused by the noise and dust generated from crusher of the mine and quarry are emerging. Therefore mining facilities such as crushers and mills have been installed in an underground. In order to facilitate crusher equipments in the underground, excavation of large space is required and then the stability of the large space underground structure is an important issue. In this study, the blast experiments, which use a block of the limestone, are performed. Based on the blast experiments, the numerical model was prepared and simulated using dynamic fracture process analysis code(DFPA) with considering the rising time of applied borehole pressure and microscopic tensile strength variation. Comparing the non-dimensional crack length and no-dimensional tensile strength obtained from blast experiments and numerical analyses, the input parameters of DFPA code for predicting a radial tensile crack in limestone blasting were determined.

Numerical Study on the Crack-propagation Controlling in Blasting Using Notched Charge Hole (노치 장약공을 이용한 발파균열제어에 관한 수치해석적 연구)

  • Cho, Sang-Ho;Park, Seung-Hwan;Kim, Kwang-Yeom;Nakamura, Yuichi;Kaneko, Katsuhiko
    • Explosives and Blasting
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    • v.26 no.1
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    • pp.49-55
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    • 2008
  • Mechanical excavation techniques employing tunnel boring machines (TBM) and rock splitters have been proposed to minimize rock damage for tunnel and underground waste repository facilities. Such a mechanical excavation, however, is extremely expensive and not applicable in all cases. For these reasons, controlled blasting using notched charge holes have been suggested to achieve crack growth along specific directions and inhibit growth along other directions. This study introduces a dynamic fracture process analysis code to simulate fracture processes of rock which has a notched charge hole.

Numerical Study on the Reduction of Blast-induced Damage Zone (최외곽공 주변암반의 발파굴착 손상영역 저감에 관한 수치해석적 연구)

  • Park, Se-Woong;Oh, Se-Wook;Min, Gyeong-Jo;Fukuda, Daisuke;Cho, Sang-Ho
    • Explosives and Blasting
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    • v.37 no.3
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    • pp.25-33
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    • 2019
  • Controlling the blast-induced damage zone(BDZ) in mining excavation is a significant issue for the safety of employees and the maintenance of facilities. Numerous studies have been conducted to accurately predict the BDZ in underground mining. This study employed the dynamic fracture process analysis (DFPA) to estimate the BDZ from a single hole blasting. The estimated BDZ were compared with the results obtained by Swedish empirical equation. The DFPA was also used to investigate the control mechanism of BDZ and fracture plane formation around perimeter holes for underground mining blasting.