Pub Date : 2024-10-16DOI: 10.1016/j.engfracmech.2024.110555
Minghao Zhang , Zengqiang Cao , Xinglong Gong , Qi Hu , Mengchen Yu , Lubin Huo
To investigate the mechanical response and damage behavior of aircraft fuselage composite structures under out-of-plane impact loads more efficiently and flexibility, this paper proposed a novel impact approach and testing platform based on inductive coils to yield electromagnetic impact force. The influence of system key parameters on the electromagnetic loading waveforms were analyzed using an electromagnetic field finite element model. Single/repeated impact tests on CFRP/aluminium alloy (Al) riveted structures were conducted at different voltages (energies) based on this approach. The results indicate that the electromagnetic impact (EMI) approach exhibits significant advantages in both variable strain rate loading and continuous impact loading scenarios. This device can efficiently achieve multi-point and multiple impact loading. The electromagnetic impact forces with various amplitudes and pulse-widths can be accurately obtained by altering voltage and capacitance values, which can demonstrate the good experimental consistency of such test approach. Besides, with this test method, the load threshold for damage formation can be clearly defined: once the impact force exceeds the damage threshold load, the delamination area of the CFRP laminates expand as the impact energy increases. Note that when the provided out-of-plane impact load is slightly higher than the damage threshold load by changing the voltage, significant delamination damage may suddenly manifest in any one impact event of the repeated impacts.
{"title":"A novel impact approach based on electromagnetic loading technology: A case study on CFRP/Al riveted structures","authors":"Minghao Zhang , Zengqiang Cao , Xinglong Gong , Qi Hu , Mengchen Yu , Lubin Huo","doi":"10.1016/j.engfracmech.2024.110555","DOIUrl":"10.1016/j.engfracmech.2024.110555","url":null,"abstract":"<div><div>To investigate the mechanical response and damage behavior of aircraft fuselage composite structures under out-of-plane impact loads more efficiently and flexibility, this paper proposed a novel impact approach and testing platform based on inductive coils to yield electromagnetic impact force. The influence of system key parameters on the electromagnetic loading waveforms were analyzed using an electromagnetic field finite element model. Single/repeated impact tests on CFRP/aluminium alloy (Al) riveted structures were conducted at different voltages (energies) based on this approach. The results indicate that the electromagnetic impact (EMI) approach exhibits significant advantages in both variable strain rate loading and continuous impact loading scenarios. This device can efficiently achieve multi-point and multiple impact loading. The electromagnetic impact forces with various amplitudes and pulse-widths can be accurately obtained by altering voltage and capacitance values, which can demonstrate the good experimental consistency of such test approach. Besides, with this test method, the load threshold for damage formation can be clearly defined: once the impact force exceeds the damage threshold load, the delamination area of the CFRP laminates expand as the impact energy increases. Note that when the provided out-of-plane impact load is slightly higher than the damage threshold load by changing the voltage, significant delamination damage may suddenly manifest in any one impact event of the repeated impacts.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110555"},"PeriodicalIF":4.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529422","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}
Pub Date : 2024-10-15DOI: 10.1016/j.engfracmech.2024.110551
Ch. Knisovitis , A.E. Giannakopoulos , Ares J. Rosakis
This work investigates the deformation and polarization fields around a finite anti-plane shear (mode III) crack growing dynamically under steady-state conditions. The leading tip of this finite crack breaks the material while the trailing tip heals it. This fast moving finite crack (referred to as a rupture “pulse” in the geophysics literature) propagates with a constant velocity and with the mechanical and the electrical fields that remain invariant with respect to an observer moving with the crack-tips. This problem belongs to the first type of steady state crack growth problems according to the classification of Freund. The “prototype” problem which refers to an isotropic, body subjected to fracture under tensile loading was first proposed and solved by Yoffe, while finite cracks (or shear pulses) were also analyzed by Freund and by Rice. In the above cases the material was assumed to be linear elastic. Our analysis extends these studies to flexoelectric materials, and it is both theoretical and numerical. It discusses the asymptotic structure of the crack-tip displacement and the polarization fields; it calculates the dynamic energy release rate and presents their dependence on crack-tip velocity. Comparisons are made to the available, classical, elasto-dynamic solutions and to the static case. The influence of the electrical properties of the material on strengthening is also analyzed. Dynamic fracture of flexoelectric materials is of relevance to both the study of earthquake source mechanics and to the analysis of the reliability of micro-electronic devices. This is because both rocks and ceramics are flexoelectric. Indeed, during earthquake rupture processes, dynamic, in-plane shear (Mode-II) and out of plane shear (Mode-III), cracks propagate along faults and exhibit both mechanical and electrical polarization signatures. At an entirely different length scale, flexoelectric ceramics are currently used as sensors and transducers and can experience dynamic shear failure along interfaces when subjected to dynamic loading (e.g. impact.). Failure by dynamic fracture can be detrimental to both their mechanical reliability and electrical functionality.
{"title":"Anti-plane Yoffe-type crack in flexoelectric material","authors":"Ch. Knisovitis , A.E. Giannakopoulos , Ares J. Rosakis","doi":"10.1016/j.engfracmech.2024.110551","DOIUrl":"10.1016/j.engfracmech.2024.110551","url":null,"abstract":"<div><div>This work investigates the deformation and polarization fields around a finite anti-plane shear (mode III) crack growing dynamically under steady-state conditions. The leading tip of this finite crack breaks the material while the trailing tip heals it. This fast moving finite crack (referred to as a rupture “pulse” in the geophysics literature) propagates with a constant velocity and with the mechanical and the electrical fields that remain invariant with respect to an observer moving with the crack-tips. This problem belongs to the first type of steady state crack growth problems according to the classification of Freund. The “prototype” problem which refers to an isotropic, body subjected to fracture under tensile loading was first proposed and solved by Yoffe, while finite cracks (or shear pulses) were also analyzed by Freund and by Rice. In the above cases the material was assumed to be linear elastic. Our analysis extends these studies to flexoelectric materials, and it is both theoretical and numerical. It discusses the asymptotic structure of the crack-tip displacement and the polarization fields; it calculates the dynamic energy release rate and presents their dependence on crack-tip velocity. Comparisons are made to the available, classical, elasto-dynamic solutions and to the static case. The influence of the electrical properties of the material on strengthening is also analyzed. Dynamic fracture of flexoelectric materials is of relevance to both the study of earthquake source mechanics and to the analysis of the reliability of micro-electronic devices. This is because both rocks and ceramics are flexoelectric. Indeed, during earthquake rupture processes, dynamic, in-plane shear (Mode-II) and out of plane shear (Mode-III), cracks propagate along faults and exhibit both mechanical and electrical polarization signatures. At an entirely different length scale, flexoelectric ceramics are currently used as sensors and transducers and can experience dynamic shear failure along interfaces when subjected to dynamic loading (e.g. impact.). Failure by dynamic fracture can be detrimental to both their mechanical reliability and electrical functionality.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110551"},"PeriodicalIF":4.7,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529424","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}
Pub Date : 2024-10-15DOI: 10.1016/j.engfracmech.2024.110556
Wenyue Zhang , Yiming Su , Yufeng Jiang , Zhiqiang Hu , Jingtao Bi , Wentao He
This study establishes a data-driven surrogate model within a machine learning (ML) framework for the rapid and accurate prediction of crack extension paths and fatigue life in tubular T-joints. A data-driven program is developed by integrating principal components analysis (PCA), fatigue crack propagation theory and multilayer perceptron neural network (MLP NN). The dataset of ML model is established by co-simulation of ABAQUS and FRANC3D, and the data dimension is reduced by data reconstruction and PCA to improve the computational efficiency. The stress intensity factor (SIF) is predicted by MLP NN model along with the crack front to drive 3D cracks propagation automatically, which enhances calculation efficiency significantly compared with finite element method. The prediction performance of MLP NN and other three ML models are compared, which demonstrates that the prediction accuracy of the framework built by MLP NN model is higher. The data-driven surrogate model is applied to predict the SIF, propagation path and fatigue life of cracks with different depth-to-length (c/a) ratios and initial positions in tubular T-joints, which confirms its excellent accuracy and robustness in terms of the fatigue crack propagation analysis.
本研究在机器学习（ML）框架内建立了一个数据驱动的代用模型，用于快速准确地预测管状 T 形接头的裂纹扩展路径和疲劳寿命。通过整合主成分分析（PCA）、疲劳裂纹扩展理论和多层感知器神经网络（MLP NN），开发了一个数据驱动程序。通过 ABAQUS 和 FRANC3D 的协同仿真建立了 ML 模型的数据集，并通过数据重构和 PCA 降低了数据维度，从而提高了计算效率。通过 MLP NN 模型预测应力强度因子（SIF）和裂纹前沿，自动驱动三维裂纹扩展，与有限元方法相比，计算效率显著提高。比较了 MLP NN 和其他三种 ML 模型的预测性能，结果表明 MLP NN 模型构建的框架预测精度更高。应用数据驱动的代用模型预测了管状 T 型接头中不同深度长度比 (c/a) 和初始位置的裂纹的 SIF、扩展路径和疲劳寿命，证实了该模型在疲劳裂纹扩展分析方面具有出色的准确性和鲁棒性。
{"title":"Data-driven fatigue crack propagation and life prediction of tubular T-joint: A fracture mechanics based machine learning surrogate model","authors":"Wenyue Zhang , Yiming Su , Yufeng Jiang , Zhiqiang Hu , Jingtao Bi , Wentao He","doi":"10.1016/j.engfracmech.2024.110556","DOIUrl":"10.1016/j.engfracmech.2024.110556","url":null,"abstract":"<div><div>This study establishes a data-driven surrogate model within a machine learning (ML) framework for the rapid and accurate prediction of crack extension paths and fatigue life in tubular T-joints. A data-driven program is developed by integrating principal components analysis (PCA), fatigue crack propagation theory and multilayer perceptron neural network (MLP NN). The dataset of ML model is established by co-simulation of ABAQUS and FRANC3D, and the data dimension is reduced by data reconstruction and PCA to improve the computational efficiency. The stress intensity factor (SIF) is predicted by MLP NN model along with the crack front to drive 3D cracks propagation automatically, which enhances calculation efficiency significantly compared with finite element method. The prediction performance of MLP NN and other three ML models are compared, which demonstrates that the prediction accuracy of the framework built by MLP NN model is higher. The data-driven surrogate model is applied to predict the SIF, propagation path and fatigue life of cracks with different depth-to-length (<em>c/a</em>) ratios and initial positions in tubular T-joints, which confirms its excellent accuracy and robustness in terms of the fatigue crack propagation analysis.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110556"},"PeriodicalIF":4.7,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529423","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}
Pub Date : 2024-10-14DOI: 10.1016/j.engfracmech.2024.110554
Qunjie Zhang , Jun Zhang , Junnan Liu , Zheting Jia , Ziqing Chen
The aim of this study was to establish a method for evaluating notch fatigue behavior through crystal plasticity finite element (CPFE) simulations based on the actual microstructure of the nickel-based alloy Inconel 718 (IN718). Initially, the equivalent plastic strain, εeps, which reflects the comprehensive slip at the grain scale, was employed to analyze the fatigue crack initiation mechanism of IN718, revealing that twinning and triple junctions of grain boundaries were high-risk locations for fatigue crack initiation. Next, fatigue simulations were performed on notched specimens using the CPFE model, with a material-level CPFE model particularly employed at the notch root. The increment of εeps, Δεeps, in a stable cycle was used as the fatigue damage control parameter and correlated with the fatigue life, Nf, revealing that the Δεeps-Nf relationship at material-level satisfied the form of the Mason-Coffin model. Finally, fatigue life prediction of IN718 notched specimens was carried out based on the Δεeps-Nf relationship, with the predicted results falling within the 2-fold scatter band, demonstrating good prediction accuracy.
{"title":"Crystal plasticity-driven evaluation of notch fatigue behavior in IN718","authors":"Qunjie Zhang , Jun Zhang , Junnan Liu , Zheting Jia , Ziqing Chen","doi":"10.1016/j.engfracmech.2024.110554","DOIUrl":"10.1016/j.engfracmech.2024.110554","url":null,"abstract":"<div><div>The aim of this study was to establish a method for evaluating notch fatigue behavior through crystal plasticity finite element (CPFE) simulations based on the actual microstructure of the nickel-based alloy Inconel 718 (IN718). Initially, the equivalent plastic strain, <em>ε<sub>eps</sub></em>, which reflects the comprehensive slip at the grain scale, was employed to analyze the fatigue crack initiation mechanism of IN718, revealing that twinning and triple junctions of grain boundaries were high-risk locations for fatigue crack initiation. Next, fatigue simulations were performed on notched specimens using the CPFE model, with a material-level CPFE model particularly employed at the notch root. The increment of <em>ε<sub>eps</sub></em>, Δ<em>ε<sub>eps</sub></em>, in a stable cycle was used as the fatigue damage control parameter and correlated with the fatigue life, <em>N<sub>f</sub></em>, revealing that the Δ<em>ε<sub>eps</sub></em>-<em>N<sub>f</sub></em> relationship at material-level satisfied the form of the Mason-Coffin model. Finally, fatigue life prediction of IN718 notched specimens was carried out based on the Δ<em>ε<sub>eps</sub></em>-<em>N<sub>f</sub></em> relationship, with the predicted results falling within the 2-fold scatter band, demonstrating good prediction accuracy.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110554"},"PeriodicalIF":4.7,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446961","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}
Pub Date : 2024-10-12DOI: 10.1016/j.engfracmech.2024.110548
Yahui Peng , Haitao Zhao , Hang Sun , Mingqing Yuan , Zhiqiang Li , Qiubao Ouyang , Ji’an Chen
A strain gradient plasticity model with strengthening effect and damage effect (SGSED) is developed under the continuum medium framework for particle-reinforced heterogeneous matrix composites (PRHMCs). Boron carbide (B4C) particle-reinforced ultrafine-grained (UFG)/fine-grained (FG) heterogeneous matrix composites (B4Cp/(UFG/FG)) are fabricated, in which the UFG region consisted of carbon nanotubes (CNTs)/6061 aluminum (Al) flakes with grains in the ultrafine range and the FG region is processed via 6061Al. The SGSED model is written into the user subroutines using commercial finite element (FE) calculation software, and the three-dimensional (3D) FE representative volume element (RVE) for B4Cp/(UFG/FG) composites is established, from which the distribution of the interface-affected-zone (IAZ) formed of the strain gradient caused by the uncoordinated deformation of the UFG-FG heterogeneous matrix and reinforced phase-matrix is calculated. The evolution of the strain gradient in the deformation process of composites and the influence of the strain gradient on the progressive damage and crack evolution of composites are analyzed, and the strain gradient strengthening-toughening mechanism of composites is revealed. It is found that the IAZ has a considerable strengthening-toughening effect on the composites, which can reduce stress concentration at the interface between the reinforced phase and the matrix, and slow down the crack propagation of the matrix.
{"title":"Strain-gradient and damage failure behavior in particle reinforced heterogeneous matrix composites","authors":"Yahui Peng , Haitao Zhao , Hang Sun , Mingqing Yuan , Zhiqiang Li , Qiubao Ouyang , Ji’an Chen","doi":"10.1016/j.engfracmech.2024.110548","DOIUrl":"10.1016/j.engfracmech.2024.110548","url":null,"abstract":"<div><div>A strain gradient plasticity model with strengthening effect and damage effect (SGSED) is developed under the continuum medium framework for particle-reinforced heterogeneous matrix composites (PRHMCs). Boron carbide (B<sub>4</sub>C) particle-reinforced ultrafine-grained (UFG)/fine-grained (FG) heterogeneous matrix composites (B<sub>4</sub>C<sub>p</sub>/(UFG/FG)) are fabricated, in which the UFG region consisted of carbon nanotubes (CNTs)/6061 aluminum (Al) flakes with grains in the ultrafine range and the FG region is processed via 6061Al. The SGSED model is written into the user subroutines using commercial finite element (FE) calculation software, and the three-dimensional (3D) FE representative volume element (RVE) for B<sub>4</sub>C<sub>p</sub>/(UFG/FG) composites is established, from which the distribution of the interface-affected-zone (IAZ) formed of the strain gradient caused by the uncoordinated deformation of the UFG-FG heterogeneous matrix and reinforced phase-matrix is calculated. The evolution of the strain gradient in the deformation process of composites and the influence of the strain gradient on the progressive damage and crack evolution of composites are analyzed, and the strain gradient strengthening-toughening mechanism of composites is revealed. It is found that the IAZ has a considerable strengthening-toughening effect on the composites, which can reduce stress concentration at the interface between the reinforced phase and the matrix, and slow down the crack propagation of the matrix.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110548"},"PeriodicalIF":4.7,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446962","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}
The microstructure and mechanical properties of 7075/6061 high-strength dissimilar aluminum alloy fusion welds, after TiC nanoparticle-assisted welding and heat treatment, were discussed, and their fatigue performance was analyzed. The results indicate that the significant increase in hardness at the weld zone with T6 treatment compared to T5 is due to the solution treatment providing supersaturated solid solution for subsequent aging precipitation. T5 treatment causes the precipitation in the heat affected zones, thereby increasing the hardness of these regions. The joints exhibit excellent yield strength and tensile strength after heat treatment, with the elongation performance being optimal in T6 state. The fatigue performance of dissimilar aluminum alloy joints treated with nanoparticle and heat treatment is superior to the joints with single riveting. Porosity defects and microcracks generated during welding are prone to stress concentration, with interconnected pores and easily propagating cracks forming fatigue sources for pores and cracks. The crack propagation behavior is influenced by the pinning effect of TiC nanoparticles at the grain boundaries, and the second phase particles hinder crack propagation along the grain boundaries, forcing cracks to extend towards the 6061 side or the HAZ of the lower strength 6061 matrix. It demonstrates that the method of combining nanoparticle-assisted melt inert-gas welding and T6 heat treatment improves the fatigue life of 7075/6061 dissimilar aluminum alloy joints.
{"title":"Research on the microstructure, mechanical and fatigue performance of 7075/6061 dissimilar aluminum alloy fusion welding joint treated by nanoparticle and post-weld heat treatment","authors":"Baijun Zhang , Yongkang Zhang , Kangsheng Zheng , Yuanqing Chi","doi":"10.1016/j.engfracmech.2024.110550","DOIUrl":"10.1016/j.engfracmech.2024.110550","url":null,"abstract":"<div><div>The microstructure and mechanical properties of 7075/6061 high-strength dissimilar aluminum alloy fusion welds, after TiC nanoparticle-assisted welding and heat treatment, were discussed, and their fatigue performance was analyzed. The results indicate that the significant increase in hardness at the weld zone with T6 treatment compared to T5 is due to the solution treatment providing supersaturated solid solution for subsequent aging precipitation. T5 treatment causes the precipitation in the heat affected zones, thereby increasing the hardness of these regions. The joints exhibit excellent yield strength and tensile strength after heat treatment, with the elongation performance being optimal in T6 state. The fatigue performance of dissimilar aluminum alloy joints treated with nanoparticle and heat treatment is superior to the joints with single riveting. Porosity defects and microcracks generated during welding are prone to stress concentration, with interconnected pores and easily propagating cracks forming fatigue sources for pores and cracks. The crack propagation behavior is influenced by the pinning effect of TiC nanoparticles at the grain boundaries, and the second phase particles hinder crack propagation along the grain boundaries, forcing cracks to extend towards the 6061 side or the HAZ of the lower strength 6061 matrix. It demonstrates that the method of combining nanoparticle-assisted melt inert-gas welding and T6 heat treatment improves the fatigue life of 7075/6061 dissimilar aluminum alloy joints.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110550"},"PeriodicalIF":4.7,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441538","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}
Pub Date : 2024-10-11DOI: 10.1016/j.engfracmech.2024.110549
Tao Hu , Xianglong Li , Jianguo Wang , Jun Ma , Qiwen Hu , Ting Zuo
The objective of presplit blasting is to achieve directional fracturing of rock and obtain a smooth fracture surface. Axial decoupling spherical charge presplit blasting (PSB-ADSC) is a novel design method. To investigate the smoothness of the fracture surface and the formation and development process of pre-cracks under PSB-ADSC conditions, a spherical charge blast load was applied to a cement mortar model with seven boreholes. The characteristics of the fracture surface and the formation process of the pre-cracks were analyzed. Firstly, fractal theory was utilized to study the spatial variation in fractal dimension on the fracture surfaces. Secondly, high-speed photography was employed to examine the formation and development of pre-cracks. Finally, based on digital image correlation method, the strain development process on the free surface was revealed. The results indicate that the PSB-ADSC method can produce pre-cracks, fracture surfaces, and half-cast holes similar to those of traditional presplit blasting. Moreover, the distribution of the charges has a significant impact on the effectiveness of PSB-ADSC. Therefore, in the axial direction of the borehole, the fractal dimension increases with the distance from the spherical charges. In the borehole diameter direction, the smoothness of the fracture surface gradually decreases with the distance from the borehole. Macroscopic cracks and strain concentration areas first appear at the central position of the specimen, where the explosive stress wave superposition is strongest. The quasi-static action of the detonation gas plays a major role in the formation of the fracture surface and pre-cracks. Once the constraint effect weakens, the pre-cracks will rapidly propagate.
{"title":"Fracture behavior and fracture surface smoothness of rock-like model subjected to axial decoupling spherical charging","authors":"Tao Hu , Xianglong Li , Jianguo Wang , Jun Ma , Qiwen Hu , Ting Zuo","doi":"10.1016/j.engfracmech.2024.110549","DOIUrl":"10.1016/j.engfracmech.2024.110549","url":null,"abstract":"<div><div>The objective of presplit blasting is to achieve directional fracturing of rock and obtain a smooth fracture surface. Axial decoupling spherical charge presplit blasting (PSB-ADSC) is a novel design method. To investigate the smoothness of the fracture surface and the formation and development process of pre-cracks under PSB-ADSC conditions, a spherical charge blast load was applied to a cement mortar model with seven boreholes. The characteristics of the fracture surface and the formation process of the pre-cracks were analyzed. Firstly, fractal theory was utilized to study the spatial variation in fractal dimension on the fracture surfaces. Secondly, high-speed photography was employed to examine the formation and development of pre-cracks. Finally, based on digital image correlation method, the strain development process on the free surface was revealed. The results indicate that the PSB-ADSC method can produce pre-cracks, fracture surfaces, and half-cast holes similar to those of traditional presplit blasting. Moreover, the distribution of the charges has a significant impact on the effectiveness of PSB-ADSC. Therefore, in the axial direction of the borehole, the fractal dimension increases with the distance from the spherical charges. In the borehole diameter direction, the smoothness of the fracture surface gradually decreases with the distance from the borehole. Macroscopic cracks and strain concentration areas first appear at the central position of the specimen, where the explosive stress wave superposition is strongest. The quasi-static action of the detonation gas plays a major role in the formation of the fracture surface and pre-cracks. Once the constraint effect weakens, the pre-cracks will rapidly propagate.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110549"},"PeriodicalIF":4.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441536","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}
Pub Date : 2024-10-10DOI: 10.1016/j.engfracmech.2024.110544
Zhibiao Guo , Jingwei Gao , Jinglin You
The combination of rock and concrete lining structures is a typical composite structure in the field of engineering. This study is based on the concept of equivalent strain energy and establishes a mechanical equivalent model for rock-concrete assemblies (RCA). Assuming that both rock and concrete satisfy the Mohr-Coulomb criterion, we derive the shear failure criterion of the equivalent model considering the roughness of the rock-concrete interface. The applicability of the model was verified through uniaxial and triaxial tests on eight different types of RCA structures. The research results indicate that an increase in confining pressure enhances the strength of the RCA. When the confining pressure reaches a certain value, concrete only experiences shear failure, and no macroscopic cracks appear in the rock. The structure of the RCA tends towards isotropy. As the height ratio of the RCA increases, its strength decreases. At minimal concrete height ratios, the strength of the RCA gradually approaches that of concrete. This study can provide valuable insights for designing and evaluating stability in engineering rock bodies within diverse geological environments.
{"title":"Research on compression failure criteria and characteristics of rock-concrete assemblies with rough interfaces","authors":"Zhibiao Guo , Jingwei Gao , Jinglin You","doi":"10.1016/j.engfracmech.2024.110544","DOIUrl":"10.1016/j.engfracmech.2024.110544","url":null,"abstract":"<div><div>The combination of rock and concrete lining structures is a typical composite structure in the field of engineering. This study is based on the concept of equivalent strain energy and establishes a mechanical equivalent model for rock-concrete assemblies (RCA). Assuming that both rock and concrete satisfy the Mohr-Coulomb criterion, we derive the shear failure criterion of the equivalent model considering the roughness of the rock-concrete interface. The applicability of the model was verified through uniaxial and triaxial tests on eight different types of RCA structures. The research results indicate that an increase in confining pressure enhances the strength of the RCA. When the confining pressure reaches a certain value, concrete only experiences shear failure, and no macroscopic cracks appear in the rock. The structure of the RCA tends towards isotropy. As the height ratio of the RCA increases, its strength decreases. At minimal concrete height ratios, the strength of the RCA gradually approaches that of concrete. This study can provide valuable insights for designing and evaluating stability in engineering rock bodies within diverse geological environments.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110544"},"PeriodicalIF":4.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438058","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}
Pub Date : 2024-10-10DOI: 10.1016/j.engfracmech.2024.110545
Su Wang , Mian Chen , Yalong Hao , Changjun Zhao , Tong Zhou
Considering the high construction cost of horizontal adjacent well monitoring and the lack of vertical adjacent well fiber optic for obtaining fracturing information, this paper proposes the use of deviated wells with fiber optics for monitoring purposes. To demonstrate the advantages of deviated well fiber optics and the feasibility of their deployment, this paper constructs a forward model based on the finite element coupled with cohesive element approach to simulate the strain induced by the propagation of a single hydraulic fracture in horizontal wells on deviated well fiber optics, and conducts a numerical simulation analysis of the strain induced by the propagation of a single hydraulic fracture on deviated well fiber optics. The results show that the strain evolution induced by single-fracture propagation in deviated well fiber optics can be divided into four stages: strain-enhancing, strain-converging, tensile strain-expanding, and linear strain-converging. The strain evolution characteristics of deviated well fiber optics are manifested as follows: a “heart-shaped” tensile strain convergence zone with a certain deviation appears in the middle, which subsequently converges into a tensile strain convergence band, with compressive strain convergence zones on both sides, and an expanding tensile strain convergence zone on the outer side of the compressive strain convergence band. The analysis finds that when the well inclination angle is greater than 45°, the strain response characteristics of deviated well fiber optics are mainly governed by the width expansion of the fracture, and when less than 45°, they are mainly governed by the height expansion of the fracture. Changes in the azimuth angle can cause a deviation of the “heart-shaped” tensile strain area and the compressive strain convergence zone in the fiber-optic strain waterfall plot, with larger deviations corresponding to smaller azimuth angles. The depth at which the deviated well fiber optics are deployed, reaching the depth of the horizontal section of the horizontal well, can reflect the upward expansion of the fracture height. The results of the analysis illustrate the advantages of deviated well fiber optics in obtaining both fracture width and height expansion information simultaneously and propose a method for selecting suitable deviated well fiber-optic construction parameters based on fracturing monitoring needs. This research can reduce the construction cost of deploying fiber optics in adjacent wells and has significant implications for guiding the layout of adjacent well fiber optics.
{"title":"Evolution mechanism of deviated well fiber-optic strain induced by single-fracture propagation during fracturing in horizontal wells","authors":"Su Wang , Mian Chen , Yalong Hao , Changjun Zhao , Tong Zhou","doi":"10.1016/j.engfracmech.2024.110545","DOIUrl":"10.1016/j.engfracmech.2024.110545","url":null,"abstract":"<div><div>Considering the high construction cost of horizontal adjacent well monitoring and the lack of vertical adjacent well fiber optic for obtaining fracturing information, this paper proposes the use of deviated wells with fiber optics for monitoring purposes. To demonstrate the advantages of deviated well fiber optics and the feasibility of their deployment, this paper constructs a forward model based on the finite element coupled with cohesive element approach to simulate the strain induced by the propagation of a single hydraulic fracture in horizontal wells on deviated well fiber optics, and conducts a numerical simulation analysis of the strain induced by the propagation of a single hydraulic fracture on deviated well fiber optics. The results show that the strain evolution induced by single-fracture propagation in deviated well fiber optics can be divided into four stages: strain-enhancing, strain-converging, tensile strain-expanding, and linear strain-converging. The strain evolution characteristics of deviated well fiber optics are manifested as follows: a “heart-shaped” tensile strain convergence zone with a certain deviation appears in the middle, which subsequently converges into a tensile strain convergence band, with compressive strain convergence zones on both sides, and an expanding tensile strain convergence zone on the outer side of the compressive strain convergence band. The analysis finds that when the well inclination angle is greater than 45°, the strain response characteristics of deviated well fiber optics are mainly governed by the width expansion of the fracture, and when less than 45°, they are mainly governed by the height expansion of the fracture. Changes in the azimuth angle can cause a deviation of the “heart-shaped” tensile strain area and the compressive strain convergence zone in the fiber-optic strain waterfall plot, with larger deviations corresponding to smaller azimuth angles. The depth at which the deviated well fiber optics are deployed, reaching the depth of the horizontal section of the horizontal well, can reflect the upward expansion of the fracture height. The results of the analysis illustrate the advantages of deviated well fiber optics in obtaining both fracture width and height expansion information simultaneously and propose a method for selecting suitable deviated well fiber-optic construction parameters based on fracturing monitoring needs. This research can reduce the construction cost of deploying fiber optics in adjacent wells and has significant implications for guiding the layout of adjacent well fiber optics.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110545"},"PeriodicalIF":4.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433802","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}
Pub Date : 2024-10-09DOI: 10.1016/j.engfracmech.2024.110526
Pengfei Liu , Zhanghua Chen , Chao Xu , Jianxin Dong , He Jiang
In this work, a dislocation density-based crystal plasticity phase-field model (CP-PFM) is developed to simulate fatigue crack growth in nickel-based superalloys. Through normalization validation, the plastic dissipation work and crystallographic work are shown to be consistent with the fatigue indicator factors (FIPs), cumulative equivalent plastic strain and cumulative shear strain, and the two energies are computed as the main driving forces of the phase field. Both driving force models are able to obtain fatigue crack growth in close approximation to the experimental rate. However, the model with crystallographic work as the main driving force obtains crack growth paths that are in better agreement with electron backscattering pattern (EBSD) observations, which is attributed to its greater ability to characterize the microstructural susceptibility of fatigue crack growth. Specifically, the model is able to capture the tendency of cracks to crack along the close-packed planes and the hindering effect of grains with large misorientation angles on fatigue crack growth, which together contribute to the curved morphology of fatigue cracks. The combination of large grains or grains with small misorientation angles favors persistent slip band (PSB) formation and leads to softening of the crack tip, which results in lower fatigue crack growth rates.
{"title":"A crystal plasticity phase-field model for microstructure sensitive fatigue crack growth in a superalloy","authors":"Pengfei Liu , Zhanghua Chen , Chao Xu , Jianxin Dong , He Jiang","doi":"10.1016/j.engfracmech.2024.110526","DOIUrl":"10.1016/j.engfracmech.2024.110526","url":null,"abstract":"<div><div>In this work, a dislocation density-based crystal plasticity phase-field model (CP-PFM) is developed to simulate fatigue crack growth in nickel-based superalloys. Through normalization validation, the plastic dissipation work and crystallographic work are shown to be consistent with the fatigue indicator factors (FIPs), cumulative equivalent plastic strain and cumulative shear strain, and the two energies are computed as the main driving forces of the phase field. Both driving force models are able to obtain fatigue crack growth in close approximation to the experimental rate. However, the model with crystallographic work as the main driving force obtains crack growth paths that are in better agreement with electron backscattering pattern (EBSD) observations, which is attributed to its greater ability to characterize the microstructural susceptibility of fatigue crack growth. Specifically, the model is able to capture the tendency of cracks to crack along the close-packed planes and the hindering effect of grains with large misorientation angles on fatigue crack growth, which together contribute to the curved morphology of fatigue cracks. The combination of large grains or grains with small misorientation angles favors persistent slip band (PSB) formation and leads to softening of the crack tip, which results in lower fatigue crack growth rates.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"311 ","pages":"Article 110526"},"PeriodicalIF":4.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441537","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}
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