Engineering Fracture Mechanics最新文献_第4页

An adaptive SBFEM based on a nonlocal macro/meso damage model for fracture simulation of quasibrittle materials 基于非局部宏观/介质损伤模型的自适应 SBFEM，用于准脆性材料的断裂模拟

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-31 DOI: 10.1016/j.engfracmech.2024.110601

Peng Zhang , Chengbin Du , Wenhu Zhao , Shouyan Jiang , Nina Gong , Nouredine Bourahla , Zhiyong Qi

An adaptive scaled-boundary finite element method (SBFEM) is proposed to simulate the crack damage and propagation of quasibrittle materials on the basis of a nonlocal macro/meso damage model. The mesoscopic damage is defined by the deformation of the material bond between the two pairs in the model. First, the structure is discretized via an arbitrary polygon–quadtree mesh. During the damage propagation process, the damage value in each damaged element is determined by the model. Once the damage of an element reaches the damage threshold, the damaged element automatically undergoes mesh refinement until the refined mesh size meets the minimum mesh size requirement. This refinement strategy does not require manual intervention and is automatically implemented by computational software, greatly enhancing the computational efficiency of crack simulation. The transition elements between the refined area and the original elements are discretized using elements with a 2:1 size ratio, ensuring the high quality and efficiency of the automatically subdivided mesh. The nonlinear damage problem is solved iteratively via the arc-length method. The accuracy and efficiency of the proposed algorithm are verified through three numerical examples. The results also indicate that our method is not sensitive to mesh configurations, as commonly encountered in classic local damage mechanics. Moreover, increasing the mesh density results in smoother crack paths and higher computational accuracy.

在非局部宏观/介观损伤模型的基础上，提出了一种自适应比例边界有限元法（SBFEM）来模拟准脆性材料的裂纹损伤和扩展。介观损伤由模型中两对材料键的变形定义。首先，通过任意多边形四叉树网格对结构进行离散化。在损伤传播过程中，每个受损元素的损伤值由模型确定。一旦某个元素的损伤值达到损伤阈值，受损元素就会自动进行网格细化，直到细化后的网格尺寸满足最小网格尺寸要求。这种细化策略无需人工干预，由计算软件自动执行，大大提高了裂纹模拟的计算效率。细化区域与原始元素之间的过渡元素采用尺寸比为 2:1 的元素离散化，确保了自动细分网格的高质量和高效率。非线性损伤问题通过弧长法迭代求解。通过三个数值实例验证了所提算法的准确性和效率。结果还表明，我们的方法对网格配置并不敏感，这在经典局部损伤力学中很常见。此外，增加网格密度可获得更平滑的裂纹路径和更高的计算精度。

{"title":"An adaptive SBFEM based on a nonlocal macro/meso damage model for fracture simulation of quasibrittle materials","authors":"Peng Zhang , Chengbin Du , Wenhu Zhao , Shouyan Jiang , Nina Gong , Nouredine Bourahla , Zhiyong Qi","doi":"10.1016/j.engfracmech.2024.110601","DOIUrl":"10.1016/j.engfracmech.2024.110601","url":null,"abstract":"<div><div>An adaptive scaled-boundary finite element method (SBFEM) is proposed to simulate the crack damage and propagation of quasibrittle materials on the basis of a nonlocal macro/meso damage model. The mesoscopic damage is defined by the deformation of the material bond between the two pairs in the model. First, the structure is discretized via an arbitrary polygon–quadtree mesh. During the damage propagation process, the damage value in each damaged element is determined by the model. Once the damage of an element reaches the damage threshold, the damaged element automatically undergoes mesh refinement until the refined mesh size meets the minimum mesh size requirement. This refinement strategy does not require manual intervention and is automatically implemented by computational software, greatly enhancing the computational efficiency of crack simulation. The transition elements between the refined area and the original elements are discretized using elements with a 2:1 size ratio, ensuring the high quality and efficiency of the automatically subdivided mesh. The nonlinear damage problem is solved iteratively via the arc-length method. The accuracy and efficiency of the proposed algorithm are verified through three numerical examples. The results also indicate that our method is not sensitive to mesh configurations, as commonly encountered in classic local damage mechanics. Moreover, increasing the mesh density results in smoother crack paths and higher computational accuracy.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"312 ","pages":"Article 110601"},"PeriodicalIF":4.7,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A lattice modelling framework for fracture-induced acoustic emission wave propagation in concrete 混凝土中断裂诱发声发射波传播的网格建模框架

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-30 DOI: 10.1016/j.engfracmech.2024.110589

Yubao Zhou , Beyazit Bestami Aydin , Fengqiao Zhang , Max A.N. Hendriks , Yuguang Yang

To date, there is no comprehensive approach available that can explicitly model the complete transient waveforms of acoustic emissions (AE) induced by fracture processes in brittle and quasi-brittle materials like concrete. The complexity of AE modelling arises from the intricate coupling between the local discontinuity of material fracturing and the global continuity of elastic wave propagation in solids. Among others, the lattice type models are promising approaches, as they are known to be a matured modelling approach to simulate the fracturing process in concrete-like materials. Nevertheless, like other discrete element methods (DEM), they are currently limited to describing the number and rate of AE events (broken elements) in the fracture process and cannot explicitly model wave generation and propagation. In this study, we propose a lattice modeling framework to simulate the propagation of complete waveforms of fracture-induced AE signals in concrete. A proportional-integral-derivative (PID) control algorithm is incorporated in an explicit time integration procedure to reduce dynamic noise from spurious oscillations. Additionally, a Rayleigh damping-based calculation method and corresponding calibration procedure are proposed to model the attenuation of AE signals due to material damping. Using the developed approach, we systematically investigate the feasibility of lattice models for elastic wave propagation simulation, the dependence of lattice mesh sizes and the choice of numerical damping parameters. These results lead to a systematic framework which can be employed in simulating wave propagation with attenuation using DEM models in general including lattice models.

迄今为止，还没有一种全面的方法可以明确模拟混凝土等脆性和准脆性材料断裂过程引起的声发射（AE）的完整瞬态波形。声发射建模的复杂性源于材料断裂的局部不连续性与弹性波在固体中传播的全局连续性之间错综复杂的耦合关系。其中，晶格模型是一种很有前途的方法，因为众所周知，它是模拟混凝土类材料断裂过程的成熟建模方法。然而，与其他离散元素方法（DEM）一样，它们目前仅限于描述断裂过程中 AE 事件（断裂元素）的数量和速率，无法明确模拟波的产生和传播。在本研究中，我们提出了一种网格建模框架，用于模拟混凝土中断裂诱发的 AE 信号的完整波形传播。在显式时间积分过程中加入了比例积分-派生（PID）控制算法，以减少杂散振荡产生的动态噪声。此外，我们还提出了基于瑞利阻尼的计算方法和相应的校准程序，以模拟材料阻尼对 AE 信号的衰减。利用所开发的方法，我们系统地研究了用于弹性波传播模拟的晶格模型的可行性、晶格网格大小的依赖性以及数值阻尼参数的选择。这些结果形成了一个系统框架，可用于使用 DEM 模型（包括网格模型）模拟带有衰减的波传播。

{"title":"A lattice modelling framework for fracture-induced acoustic emission wave propagation in concrete","authors":"Yubao Zhou , Beyazit Bestami Aydin , Fengqiao Zhang , Max A.N. Hendriks , Yuguang Yang","doi":"10.1016/j.engfracmech.2024.110589","DOIUrl":"10.1016/j.engfracmech.2024.110589","url":null,"abstract":"<div><div>To date, there is no comprehensive approach available that can explicitly model the complete transient waveforms of acoustic emissions (AE) induced by fracture processes in brittle and quasi-brittle materials like concrete. The complexity of AE modelling arises from the intricate coupling between the local discontinuity of material fracturing and the global continuity of elastic wave propagation in solids. Among others, the lattice type models are promising approaches, as they are known to be a matured modelling approach to simulate the fracturing process in concrete-like materials. Nevertheless, like other discrete element methods (DEM), they are currently limited to describing the number and rate of AE events (broken elements) in the fracture process and cannot explicitly model wave generation and propagation. In this study, we propose a lattice modeling framework to simulate the propagation of complete waveforms of fracture-induced AE signals in concrete. A proportional-integral-derivative (PID) control algorithm is incorporated in an explicit time integration procedure to reduce dynamic noise from spurious oscillations. Additionally, a Rayleigh damping-based calculation method and corresponding calibration procedure are proposed to model the attenuation of AE signals due to material damping. Using the developed approach, we systematically investigate the feasibility of lattice models for elastic wave propagation simulation, the dependence of lattice mesh sizes and the choice of numerical damping parameters. These results lead to a systematic framework which can be employed in simulating wave propagation with attenuation using DEM models in general including lattice models.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"312 ","pages":"Article 110589"},"PeriodicalIF":4.7,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Multiple edge cracks in a coated semi-infinite medium due to non-Fourier thermal shock 非傅里叶热冲击导致涂层半无限介质出现多条边缘裂缝

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-30 DOI: 10.1016/j.engfracmech.2024.110594

Xingsheng Xu, Xuejun Chen

In this wok, based on the non-Fourier C-V model, the problem for multiple edge cracks is investigated for a coating-substrate pair subjected to a sudden temperature drop at the surface of coating. The temperature and resulting thermal stresses without cracks are obtained by the method of Laplace transform. By numerically solving the singular integral equations, the thermal stress intensity factors (SIFs) are evaluated. The results from the Fourier model and C-V heat conduction model are presented for comparison. Two dimensionless quantities are proposed to account for the coupling effects of heat conduction parameters (i.e., thermal conductivity, thermal diffusivity, and thermal relaxation time). Numerical results are presented for the thermal SIF as a function of normalized quantities such as time, crack depth, material constants and crack spacing. The findings in this work are expected to provide references for maintaining the integrity of the coating-substrate pair in the extreme heat transfer applications.

本文基于非傅里叶 C-V 模型，研究了涂层表面温度骤降时涂层-基体对的多边缘裂纹问题。通过拉普拉斯变换的方法得到了温度和由此产生的无裂缝热应力。通过数值求解奇异积分方程，评估了热应力强度因子（SIF）。傅立叶模型和 C-V 热传导模型的结果进行了比较。提出了两个无量纲量来考虑热传导参数（即热导率、热扩散率和热弛豫时间）的耦合效应。数值结果显示了热 SIF 与时间、裂纹深度、材料常数和裂纹间距等归一化量的函数关系。这项工作的研究结果有望为在极端传热应用中保持涂层-基底对的完整性提供参考。

引用次数: 0

Study on dynamic mechanical characteristics of specimens with cavity under prestressing conditions 预应力条件下带空腔试样的动态力学特性研究

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-30 DOI: 10.1016/j.engfracmech.2024.110602

Xiang Zhang , Yang Yang , Renshu Yang , Jin Li , Shulin Chen , De Li

Deep defect-bearing rock bodies are typically subjected to in-situ stresses and dynamic loading. This study investigates the failure characteristics of cavity specimens containing square holes and circular holes by employing different static-dynamic coupled loading experiments using a triaxial SHPB device that can facilitate static-dynamic coupled loading. Based on SHPB experiments, strain field analysis, and 3D laser scanning modelling techniques, this study comparatively analyses the effects of impact velocity and stress environment on the strength, stress–strain curve characteristics, dynamic damage process, and damage characteristics of square and circular hole specimens. The experiment proposes using elevation maps to characterise the damage characteristics of the specimen under impact loading. It ultimately relates the experimental results to field rockbursts and tunnel excavation, which has significant implications for guiding field practice to a certain extent. The experimental results showed that the stress environment under dynamic perturbation has a bidirectional effect (both favourable and unfavourable) on the strength of the specimens containing defects, which manifests as a difference in the characteristics of the stress–strain curves. When damage occurs near the cavity of the specimen, the stress–strain curve exhibits type I characteristics. When the entire specimen destabilises, the stress–strain curve shows type II characteristics. Under the same conditions, the strength of the specimens with square holes is significantly lower than those with circular holes. The 3D laser scanning results indicated that the damage is primarily concentrated near the cavity, and compared to the circular hole specimen, the damage area of the square hole specimen is mainly attributed to shear-tension damage, resulting in the collapse of the slabs on the upper and lower sides of the cavity.

深部含缺陷岩体通常会受到原位应力和动态载荷的作用。本研究利用可促进静-动耦合加载的三轴 SHPB 设备，通过不同的静-动耦合加载实验，研究了含有方孔和圆孔的空腔试样的破坏特征。本研究基于 SHPB 实验、应变场分析和三维激光扫描建模技术，比较分析了冲击速度和应力环境对方孔和圆孔试件强度、应力应变曲线特征、动态损伤过程和损伤特征的影响。实验提出使用高程图来描述试样在冲击加载下的损伤特征。最终将实验结果与野外岩爆和隧道开挖联系起来，在一定程度上对指导野外实践具有重要意义。实验结果表明，动态扰动下的应力环境对含有缺陷的试件强度有双向影响（有利和不利），表现为应力-应变曲线特征的不同。当损坏发生在试样空腔附近时，应力应变曲线呈现 I 型特征。当整个试样失稳时，应力-应变曲线表现出 II 型特征。在相同条件下，方孔试样的强度明显低于圆孔试样。三维激光扫描结果表明，破坏主要集中在空腔附近，与圆孔试样相比，方孔试样的破坏区域主要是剪切-张力破坏，导致空腔上下两侧的板块坍塌。

{"title":"Study on dynamic mechanical characteristics of specimens with cavity under prestressing conditions","authors":"Xiang Zhang , Yang Yang , Renshu Yang , Jin Li , Shulin Chen , De Li","doi":"10.1016/j.engfracmech.2024.110602","DOIUrl":"10.1016/j.engfracmech.2024.110602","url":null,"abstract":"<div><div>Deep defect-bearing rock bodies are typically subjected to in-situ stresses and dynamic loading. This study investigates the failure characteristics of cavity specimens containing square holes and circular holes by employing different static-dynamic coupled loading experiments using a triaxial SHPB device that can facilitate static-dynamic coupled loading. Based on SHPB experiments, strain field analysis, and 3D laser scanning modelling techniques, this study comparatively analyses the effects of impact velocity and stress environment on the strength, stress–strain curve characteristics, dynamic damage process, and damage characteristics of square and circular hole specimens. The experiment proposes using elevation maps to characterise the damage characteristics of the specimen under impact loading. It ultimately relates the experimental results to field rockbursts and tunnel excavation, which has significant implications for guiding field practice to a certain extent. The experimental results showed that the stress environment under dynamic perturbation has a bidirectional effect (both favourable and unfavourable) on the strength of the specimens containing defects, which manifests as a difference in the characteristics of the stress–strain curves. When damage occurs near the cavity of the specimen, the stress–strain curve exhibits type I characteristics. When the entire specimen destabilises, the stress–strain curve shows type II characteristics. Under the same conditions, the strength of the specimens with square holes is significantly lower than those with circular holes. The 3D laser scanning results indicated that the damage is primarily concentrated near the cavity, and compared to the circular hole specimen, the damage area of the square hole specimen is mainly attributed to shear-tension damage, resulting in the collapse of the slabs on the upper and lower sides of the cavity.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"312 ","pages":"Article 110602"},"PeriodicalIF":4.7,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of nanofiller alignment on the mode-I cohesive parameters of CNF-doped GFRP composites 纳米填料排列对掺杂 CNF 的 GFRP 复合材料 I 模内聚力参数的影响

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110591

Amit Chanda, Akash Deep, Mohd Tauheed, Rahul Kumar, Naresh V. Datla

Fiber reinforced polymer (FRP) composites with enhanced interlaminar fracture properties are crucial for many structural applications. Use of through-thickness nanofillers and their alignment are proven as beneficial to improve the out-of-plane fracture properties of laminated composites. However, the effect of nanofiller alignment on the traction-separation behavior of multiscale FRPs is still unknown. In this study, we investigated the effect of carbon nanofiber (CNF) alignment on the mode-I interlaminar fracture toughness (ILFT) and cohesive parameters of unidirectional glass fiber reinforced polymer (GFRP) laminates. Double cantilever beam (DCB) specimens of control GFRP and electric field-aligned CNF-doped GFRP were fabricated, and the aligned CNFs enhanced both the initiation and steady-state ILFT by 80.4% and 21.1%, respectively. Scanning electron microscopy of fracture surfaces indicated the multiscale fiber bridging as one of the key toughening mechanisms in aligned specimens. The cohesive parameters (traction separation law, TSL) were extracted using a DIC-based direct method and the peak traction of aligned CNF-doped GFRP specimens increased by 93.8% compared to that of control specimens. The experimentally obtained traction separation laws were utilized in numerical modeling (as tri-linear cohesive zone model) and the numerically predicted load–displacement responses of different specimens matched satisfactorily with experimental findings. The experimental identification of cohesive parameters considering effect of nanofiller alignment would certainly help in better failure prediction and safe design of laminated composites.

具有增强层间断裂性能的纤维增强聚合物（FRP）复合材料对许多结构应用至关重要。事实证明，使用通厚纳米填料及其排列有利于改善层状复合材料的平面外断裂性能。然而，纳米填料排列对多尺度玻璃钢牵引分离行为的影响仍然未知。在本研究中，我们研究了碳纳米纤维（CNF）配向对单向玻璃纤维增强聚合物（GFRP）层压板的模I层间断裂韧性（ILFT）和内聚参数的影响。研究人员制作了双悬臂梁（DCB）试样，试样分别为对照GFRP和电场配向的CNF掺杂GFRP，配向的CNF分别提高了80.4%和21.1%的起始和稳态ILFT。断裂表面的扫描电子显微镜显示，多尺度纤维桥接是对齐试样的关键增韧机制之一。使用基于 DIC 的直接方法提取了内聚力参数（牵引力分离定律，TSL），与对照试样相比，掺杂 CNF 的对齐 GFRP 试样的峰值牵引力增加了 93.8%。实验得出的牵引力分离定律被用于数值建模（作为三线性内聚区模型），不同试样的载荷-位移响应数值预测结果与实验结果完全吻合。考虑到纳米填料排列的影响，通过实验确定内聚参数肯定有助于更好地预测层状复合材料的失效和安全设计。

{"title":"Effect of nanofiller alignment on the mode-I cohesive parameters of CNF-doped GFRP composites","authors":"Amit Chanda, Akash Deep, Mohd Tauheed, Rahul Kumar, Naresh V. Datla","doi":"10.1016/j.engfracmech.2024.110591","DOIUrl":"10.1016/j.engfracmech.2024.110591","url":null,"abstract":"<div><div>Fiber reinforced polymer (FRP) composites with enhanced interlaminar fracture properties are crucial for many structural applications. Use of through-thickness nanofillers and their alignment are proven as beneficial to improve the out-of-plane fracture properties of laminated composites. However, the effect of nanofiller alignment on the traction-separation behavior of multiscale FRPs is still unknown. In this study, we investigated the effect of carbon nanofiber (CNF) alignment on the mode-I interlaminar fracture toughness (ILFT) and cohesive parameters of unidirectional glass fiber reinforced polymer (GFRP) laminates. Double cantilever beam (DCB) specimens of control GFRP and electric field-aligned CNF-doped GFRP were fabricated, and the aligned CNFs enhanced both the initiation and steady-state ILFT by 80.4% and 21.1%, respectively. Scanning electron microscopy of fracture surfaces indicated the multiscale fiber bridging as one of the key toughening mechanisms in aligned specimens. The cohesive parameters (traction separation law, TSL) were extracted using a DIC-based direct method and the peak traction of aligned CNF-doped GFRP specimens increased by 93.8% compared to that of control specimens. The experimentally obtained traction separation laws were utilized in numerical modeling (as tri-linear cohesive zone model) and the numerically predicted load–displacement responses of different specimens matched satisfactorily with experimental findings. The experimental identification of cohesive parameters considering effect of nanofiller alignment would certainly help in better failure prediction and safe design of laminated composites.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110591"},"PeriodicalIF":4.7,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Experimental and numerical investigation on rock fracturing and fragmentation under coupled static pressure and blasting 静压和爆破耦合作用下岩石断裂和破碎的实验和数值研究

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110593

Kewei Liu , Xudong Li , Jiacai Yang , Zilong Zhou , Yanyan Sha , Zhixian Hong

The blasting technique is widely adopted to break rock in civil and mining engineering, and its operation is generally subjected to static pressure due to tectonic and gravitational stresses. In the present study, the rock fracturing and fragmentation under coupled static pressure (uniaxial pressure and confining pressure) and blasting are experimentally and numerically investigated. First, 11 blast tests with 100-mm cubic red sandstone samples are carried out based on a biaxial loading system. Then, the blast-produced rock fragmentation in blast testing is numerically modeled using finite element method with LS-DYNA, and the explosion pressure attenuation and fracture evolution in rock samples are numerically reproduced. The simulated rock fragmentation data are obtained by image processing in ImageJ, and the fragment size distribution of red sandstone under combined static stress and blasting is characterized using Weibull distribution. Accordingly, the effects of uniaxial pressure and confining pressure on blast-created rock fragmentation are quantitatively compared and analyzed, and the corresponding mechanisms are discussed and revealed. The current findings indicate that the static pressure plays a role in increasing blast-induced compressive stress and reducing tensile stress in both radial and hoop directions and thus results in a decrease in the length and number of fractures propagating vertically to the direction of applied pressure, further leading to the creation of coarser fragmentation. Blasting under confining pressure produces larger fragments than that under uniaxial pressure. The average fragment size increases quickly at first and then increases slowly with the increase of static stress, which can be well characterized using a logarithm equation. Based on current findings, increasing the free surface is crucial in practical blasting to improve rock fragmentation performance under blasting.

爆破技术在土木工程和采矿工程中被广泛用于破碎岩石，其操作一般受到构造应力和重力的静压作用。本研究对静压（单轴压力和约束压力）和爆破耦合作用下的岩石断裂和破碎进行了实验和数值研究。首先，基于双轴加载系统，对 100 毫米立方体红砂岩样本进行了 11 次爆破试验。然后，使用 LS-DYNA 有限元方法对爆破试验中产生的岩石破碎进行了数值建模，并对岩石样本中的爆炸压力衰减和断裂演化进行了数值再现。利用 ImageJ 软件对模拟岩石破碎数据进行图像处理，并利用 Weibull 分布表征了红砂岩在静应力和爆破共同作用下的破碎粒度分布。据此，定量比较和分析了单轴压力和约束压力对爆破产生的岩石破碎的影响，并讨论和揭示了相应的机理。目前的研究结果表明，静压在径向和环向都起到了增加爆破引起的压应力和减少拉应力的作用，从而导致垂直于施加压力方向的裂缝长度和数量减少，进一步导致产生更粗的破碎。与单轴压力下的爆破相比，约束压力下的爆破产生的碎片更大。随着静应力的增加，平均碎片尺寸开始迅速增大，然后缓慢增大，这可以用对数方程很好地描述。根据目前的研究结果，在实际爆破中，增加自由表面对于提高爆破下的岩石破碎性能至关重要。

{"title":"Experimental and numerical investigation on rock fracturing and fragmentation under coupled static pressure and blasting","authors":"Kewei Liu , Xudong Li , Jiacai Yang , Zilong Zhou , Yanyan Sha , Zhixian Hong","doi":"10.1016/j.engfracmech.2024.110593","DOIUrl":"10.1016/j.engfracmech.2024.110593","url":null,"abstract":"<div><div>The blasting technique is widely adopted to break rock in civil and mining engineering, and its operation is generally subjected to static pressure due to tectonic and gravitational stresses. In the present study, the rock fracturing and fragmentation under coupled static pressure (uniaxial pressure and confining pressure) and blasting are experimentally and numerically investigated. First, 11 blast tests with 100-mm cubic red sandstone samples are carried out based on a biaxial loading system. Then, the blast-produced rock fragmentation in blast testing is numerically modeled using finite element method with LS-DYNA, and the explosion pressure attenuation and fracture evolution in rock samples are numerically reproduced. The simulated rock fragmentation data are obtained by image processing in ImageJ, and the fragment size distribution of red sandstone under combined static stress and blasting is characterized using Weibull distribution. Accordingly, the effects of uniaxial pressure and confining pressure on blast-created rock fragmentation are quantitatively compared and analyzed, and the corresponding mechanisms are discussed and revealed. The current findings indicate that the static pressure plays a role in increasing blast-induced compressive stress and reducing tensile stress in both radial and hoop directions and thus results in a decrease in the length and number of fractures propagating vertically to the direction of applied pressure, further leading to the creation of coarser fragmentation. Blasting under confining pressure produces larger fragments than that under uniaxial pressure. The average fragment size increases quickly at first and then increases slowly with the increase of static stress, which can be well characterized using a logarithm equation. Based on current findings, increasing the free surface is crucial in practical blasting to improve rock fragmentation performance under blasting.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110593"},"PeriodicalIF":4.7,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Unified cohesive zone model (UCZM) for fracturing and fragmenting solids 用于压裂和破碎固体的统一粘聚区模型 (UCZM)

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110598

Zhou Lei , Earl E. Knight , Antonio Munjiza , Esteban Rougier

A Unified Cohesive Zone Model (UCZM), which inherits most of the advantages while overcoming the shortcomings of existing Cohesive Zone Models (CZMs), is proposed. Similar to the traditional extrinsic CZM approach, UCZM dynamically inserts the cohesive elements into the system based on local material states (e.g., stress, strain). However, the transition from continua to discontinua is smoothly achieved, thereby eliminating the “time-discontinuous” issue seen in the extrinsic CZM. Moreover, within the novel UCZM framework, the point of transition from continua to discontinua is controllable through the introduction of crack initialization criteria. As a result, the UCZM allows any material models (e.g., elastic, plastic, damage models) for continuum solids and for discrete fracture behavior to work together. In essence, both an enhanced extrinsic cohesive zone model and an intrinsic cohesive zone model can be represented by the proposed unified model. The proposed UCZM has been verified through different numerical examples. The work demonstrates that the UCZM is a highly effective approach for modeling fracture and fragmentation processes in solids.

本文提出了一种统一内聚区模型（UCZM），它继承了现有内聚区模型（CZM）的大部分优点，同时也克服了其缺点。与传统的外在 CZM 方法类似，UCZM 根据局部材料状态（如应力、应变）动态地将内聚元素插入系统中。不过，从连续到不连续的过渡是平稳实现的，从而消除了外在 CZM 中的 "时间不连续 "问题。此外，在新颖的 UCZM 框架内，通过引入裂纹初始化标准，可以控制从连续到不连续的过渡点。因此，UCZM 允许连续固体和离散断裂行为的任何材料模型（如弹性、塑性、损伤模型）协同工作。从本质上讲，增强的外内聚区模型和内聚区模型都可以用所提出的统一模型来表示。所提出的 UCZM 已通过不同的数值实例得到验证。研究结果表明，UCZM 是模拟固体断裂和破碎过程的一种非常有效的方法。

{"title":"Unified cohesive zone model (UCZM) for fracturing and fragmenting solids","authors":"Zhou Lei , Earl E. Knight , Antonio Munjiza , Esteban Rougier","doi":"10.1016/j.engfracmech.2024.110598","DOIUrl":"10.1016/j.engfracmech.2024.110598","url":null,"abstract":"<div><div>A Unified Cohesive Zone Model (UCZM), which inherits most of the advantages while overcoming the shortcomings of existing Cohesive Zone Models (CZMs), is proposed. Similar to the traditional extrinsic CZM approach, UCZM dynamically inserts the cohesive elements into the system based on local material states (e.g., stress, strain). However, the transition from continua to discontinua is smoothly achieved, thereby eliminating the “time-discontinuous” issue seen in the extrinsic CZM. Moreover, within the novel UCZM framework, the point of transition from continua to discontinua is controllable through the introduction of crack initialization criteria. As a result, the UCZM allows any material models (e.g., elastic, plastic, damage models) for continuum solids and for discrete fracture behavior to work together. In essence, both an enhanced extrinsic cohesive zone model and an intrinsic cohesive zone model can be represented by the proposed unified model. The proposed UCZM has been verified through different numerical examples. The work demonstrates that the UCZM is a highly effective approach for modeling fracture and fragmentation processes in solids.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"312 ","pages":"Article 110598"},"PeriodicalIF":4.7,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Far-field reactivation of natural fractures by stress shadow effect 通过应力阴影效应实现天然断裂的远场再激活

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110596

ZiHan Zhang , Hao Yu , WenLong Xu , Quan Wang , SiWei Meng , Xu Jin , He Liu , HengAn Wu

Hydraulic fracturing is the most important means to achieve the reservoir stimulation of tight formations like shale, where the reservoir permeability is enhanced after the interaction between hydraulic fracture (HF) and natural fractures (NFs). Apart from the widely known direct intersection behaviors between HF and NFs (i.e., the HF meets the NFs), the NFs may also be reactivated by the stress shadow effect of HF, but the failure mechanism and reactivation modes are still unclear. To address this, the far-field reactivation of NFs under the stress shadow effect is described based on a hybrid phase field model (PFM) with the frictional contact criterion, where the open or slip conditions can be quantitatively calculated using the Mohr-Coulomb yield function along the contact interface of NFs. The zone with reactivated NFs is divided into mode II and mixed mode dominated sub-zones respectively, and the phase diagram of reactivation behaviors is summarized as variations of the location and angle of the NF. The NF reactivation modes are discussed under different geological conditions (strength of NFs, distribution angle of NFs, and initial stress difference). It could be found that the higher initial stress ratio leads to more mode II reactivated NFs, and NFs strengths and angles influence both mode II and mixed mode zones notably. The NF reactivation tends to take place with lower strength, higher injection rate, higher initial stress ratio, and special angle (e.g., HF are perpendicular to NFs), during which the permeability enhancement and reservoir stimulation are evaluated by the phase field model.

水力压裂是实现页岩等致密地层储层增渗的最重要手段，水力压裂（HF）与天然裂缝（NFs）相互作用后，储层渗透率得到提高。除了广为人知的水力压裂与天然裂缝直接交汇行为（即水力压裂与天然裂缝交汇）外，天然裂缝还可能因水力压裂的应力阴影效应而被重新激活，但其失效机理和重新激活模式仍不清楚。针对这一问题，本文基于混合相场模型（PFM）和摩擦接触准则，描述了应力阴影效应下 NFs 的远场再活化，其中开放或滑移条件可通过沿 NFs 接触界面的莫尔-库仑屈服函数进行定量计算。有再活化 NF 的区域被分别划分为模式 II 和混合模式占主导地位的子区域，再活化行为的相图归纳为 NF 位置和角度的变化。讨论了不同地质条件（NFs 强度、NFs 分布角度和初始应力差）下的 NF 再激活模式。研究发现，较高的初始应力比会导致更多的模式 II 再活化 NF，而 NF 的强度和角度对模式 II 和混合模式区都有显著影响。NF再活化倾向于在较低强度、较高注入率、较高初始应力比和特殊角度（如高频与NF垂直）条件下发生，在此过程中，渗透率的提高和储层的激励作用可通过相场模型进行评估。

{"title":"Far-field reactivation of natural fractures by stress shadow effect","authors":"ZiHan Zhang , Hao Yu , WenLong Xu , Quan Wang , SiWei Meng , Xu Jin , He Liu , HengAn Wu","doi":"10.1016/j.engfracmech.2024.110596","DOIUrl":"10.1016/j.engfracmech.2024.110596","url":null,"abstract":"<div><div>Hydraulic fracturing is the most important means to achieve the reservoir stimulation of tight formations like shale, where the reservoir permeability is enhanced after the interaction between hydraulic fracture (HF) and natural fractures (NFs). Apart from the widely known direct intersection behaviors between HF and NFs (i.e., the HF meets the NFs), the NFs may also be reactivated by the stress shadow effect of HF, but the failure mechanism and reactivation modes are still unclear. To address this, the far-field reactivation of NFs under the stress shadow effect is described based on a hybrid phase field model (PFM) with the frictional contact criterion, where the open or slip conditions can be quantitatively calculated using the Mohr-Coulomb yield function along the contact interface of NFs. The zone with reactivated NFs is divided into mode II and mixed mode dominated sub-zones respectively, and the phase diagram of reactivation behaviors is summarized as variations of the location and angle of the NF. The NF reactivation modes are discussed under different geological conditions (strength of NFs, distribution angle of NFs, and initial stress difference). It could be found that the higher initial stress ratio leads to more mode II reactivated NFs, and NFs strengths and angles influence both mode II and mixed mode zones notably. The NF reactivation tends to take place with lower strength, higher injection rate, higher initial stress ratio, and special angle (e.g., HF are perpendicular to NFs), during which the permeability enhancement and reservoir stimulation are evaluated by the phase field model.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110596"},"PeriodicalIF":4.7,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Synergistic toughening of epoxy resin by block ionomers and carbon nanofibers 嵌段离子聚合物和碳纳米纤维对环氧树脂的协同增韧作用

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110584

Weifu Sun , Dandan Gao , Dianyu E

Epoxy has been widely used in practical applications because of its excellent properties such as high tensile strength, high stiffness, strong chemical stability and excellent thermal performance, however, the brittleness has limited its further potentials. In this work, ternary polymer composites have been prepared by incorporating acidified carbon nanofibers (CNFs) and sulfonated polystyrene-block-poly (ethylene-co-butylene)-block-polystyrene (SSEBS) into epoxy resin using solution processing method. The synergistic strengthening and toughening effects of the hybrid fillers have been explored using quasi-static mechanical tests and microscopic morphology characterization. The mechanical properties of the ternary composites have been optimized by varying the loading amount of SSEBS and CNFs. The results show that when the loading amounts of SSEBS and CNFs are 10 wt% and 0.75 wt%, respectively, the composites deliver the highest fracture toughness of 1.39 KJ/m², which has been enhanced by a factor of 500 % as compared with pure epoxy while the tensile strength has been increased slightly without sacrificing its strength.

环氧树脂具有拉伸强度高、刚度大、化学稳定性强和热性能优异等优良特性，因此在实际应用中得到了广泛应用，但其脆性限制了其进一步的发展潜力。在这项工作中，采用溶液加工方法将酸化碳纳米纤维（CNF）和磺化聚苯乙烯-块状聚（乙烯-共丁烯）-块状聚苯乙烯（SSEBS）加入环氧树脂中，制备了三元聚合物复合材料。通过准静态力学测试和微观形态表征，探索了混合填料的协同增强和增韧效果。通过改变 SSEBS 和 CNF 的添加量，优化了三元复合材料的力学性能。结果表明，当 SSEBS 和 CNF 的添加量分别为 10 wt% 和 0.75 wt% 时，复合材料的断裂韧性最高，达到 1.39 KJ/m2，与纯环氧树脂相比提高了 500%，而拉伸强度在不牺牲强度的情况下略有提高。

{"title":"Synergistic toughening of epoxy resin by block ionomers and carbon nanofibers","authors":"Weifu Sun , Dandan Gao , Dianyu E","doi":"10.1016/j.engfracmech.2024.110584","DOIUrl":"10.1016/j.engfracmech.2024.110584","url":null,"abstract":"<div><div>Epoxy has been widely used in practical applications because of its excellent properties such as high tensile strength, high stiffness, strong chemical stability and excellent thermal performance, however, the brittleness has limited its further potentials. In this work, ternary polymer composites have been prepared by incorporating acidified carbon nanofibers (CNFs) and sulfonated polystyrene-block-poly (ethylene-co-butylene)-block-polystyrene (SSEBS) into epoxy resin using solution processing method. The synergistic strengthening and toughening effects of the hybrid fillers have been explored using quasi-static mechanical tests and microscopic morphology characterization. The mechanical properties of the ternary composites have been optimized by varying the loading amount of SSEBS and CNFs. The results show that when the loading amounts of SSEBS and CNFs are 10 wt% and 0.75 wt%, respectively, the composites deliver the highest fracture toughness of 1.39 KJ/m<sup>2</sup>, which has been enhanced by a factor of 500 % as compared with pure epoxy while the tensile strength has been increased slightly without sacrificing its strength.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110584"},"PeriodicalIF":4.7,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Investigating fracture mechanics in 3D-printed rocks using the hybrid finite-discrete element method 利用有限元-离散元混合方法研究三维打印岩石的断裂力学

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110592

Yimin Cao, Guanglei Cai, Huanyu Wu, Qi Zhao

We describe our contribution to the Damage Mechanics Challenge in employing the hybrid finite-discrete element method (FDEM) to investigate the fracturing process of notched three-point bending experiments on additively manufactured synthetic rocks. The calibrated numerical models can reproduce and adequately predict laboratory results in terms of load–displacement behavior and fracture pattern, suggesting that the FDEM approach could simulate the damage evolution and the fracturing of the rock. We identify several obstacles that prevent more accurate prediction of the fracturing process, particularly the difficulties in calibrating the fracture energy values for different failure modes. These highlight the directions for future research.

我们介绍了我们在 "损伤力学挑战赛 "中采用有限元-离散元混合方法（FDEM）研究添加制造的合成岩石上缺口三点弯曲实验的断裂过程所做的贡献。经过校准的数值模型可以再现并充分预测实验室结果中的载荷-位移行为和断裂模式，这表明 FDEM 方法可以模拟岩石的损伤演变和断裂。我们发现了一些妨碍更准确预测断裂过程的障碍，特别是在校准不同破坏模式的断裂能量值方面存在的困难。这些都凸显了未来研究的方向。

引用次数: 0