Theoretical and Applied Fracture Mechanics最新文献_第2页

Dynamic mixed mode I/II fracture toughness and failure behaviour of freshwater ice under impact loading 冲击荷载下淡水冰的动态 I/II 混合模式断裂韧性和破坏行为

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-19 DOI: 10.1016/j.tafmec.2024.104769

Yiheng Zhang , Xiaobin Li , Wei Chen , Qing Wang , Duanfeng Han , Yu Hu

The dynamic mixed mode I/II fracture toughness of ice involves its fracture resistance under complex impact loading, which is essential for impact or blasting parameter selection and evaluation. The notched semi-circular bend (SCB) method was applied to determine the dynamic mixed mode I/II fracture toughness of freshwater ice based on a modified split Hopkinson pressure bar setup. The effects of loading rate and grain size on the mixed mode I/II fracture toughness of ice were comprehensively explored. A high-speed digital camera was adopted to record the crack propagation path and measure the crack propagation velocity. The experimental results indicate that the dynamic effective fracture toughness of SCB ice samples is dependent on the loading rate, particularly for mode I dominated loading. The dynamic fracture toughness decreases as the grain size increases from 0.8 to 4.5 mm. Subsequently, the fracture resistance was compared with the theoretical predictions based on some brittle fracture criteria. The generalized maximum tangential stress-based semi-analytical (SA-GMTS) criterion provides a good prediction for the dynamic mixed mode I/II fracture toughness of ice. For mixed mode I/II, the crack propagation velocities rise with the increase of loading rates. However, the grain size has little effect on the velocities. These results improve the understanding of the dynamic complex fracturing mechanism in ice engineering applications.

冰的动态混合模式 I/II 断裂韧性涉及其在复杂冲击载荷下的抗断裂性，对于冲击或爆破参数的选择和评估至关重要。基于改进的分体式霍普金森压力棒装置，采用缺口半圆弯曲（SCB）法测定了淡水冰的动态混合模式 I/II 断裂韧性。全面探讨了加载速率和粒度对冰的 I/II 混合模式断裂韧性的影响。采用高速数码相机记录裂纹扩展路径并测量裂纹扩展速度。实验结果表明，SCB 冰样品的动态有效断裂韧性与加载速率有关，尤其是以模式 I 为主导的加载。动态断裂韧性随着晶粒尺寸从 0.8 毫米增加到 4.5 毫米而降低。随后，根据一些脆性断裂标准，将断裂韧性与理论预测值进行了比较。基于广义最大切向应力的半解析准则（SA-GMTS）对冰的动态混合模式 I/II 断裂韧度进行了很好的预测。对于 I/II 混合模式，裂纹扩展速度随着加载速率的增加而增加。然而，晶粒大小对速度的影响很小。这些结果加深了人们对冰工程应用中动态复合断裂机制的理解。

{"title":"Dynamic mixed mode I/II fracture toughness and failure behaviour of freshwater ice under impact loading","authors":"Yiheng Zhang , Xiaobin Li , Wei Chen , Qing Wang , Duanfeng Han , Yu Hu","doi":"10.1016/j.tafmec.2024.104769","DOIUrl":"10.1016/j.tafmec.2024.104769","url":null,"abstract":"<div><div>The dynamic mixed mode I/II fracture toughness of ice involves its fracture resistance under complex impact loading, which is essential for impact or blasting parameter selection and evaluation. The notched semi-circular bend (SCB) method was applied to determine the dynamic mixed mode I/II fracture toughness of freshwater ice based on a modified split Hopkinson pressure bar setup. The effects of loading rate and grain size on the mixed mode I/II fracture toughness of ice were comprehensively explored. A high-speed digital camera was adopted to record the crack propagation path and measure the crack propagation velocity. The experimental results indicate that the dynamic effective fracture toughness of SCB ice samples is dependent on the loading rate, particularly for mode I dominated loading. The dynamic fracture toughness decreases as the grain size increases from 0.8 to 4.5 mm. Subsequently, the fracture resistance was compared with the theoretical predictions based on some brittle fracture criteria. The generalized maximum tangential stress-based semi-analytical (SA-GMTS) criterion provides a good prediction for the dynamic mixed mode I/II fracture toughness of ice. For mixed mode I/II, the crack propagation velocities rise with the increase of loading rates. However, the grain size has little effect on the velocities. These results improve the understanding of the dynamic complex fracturing mechanism in ice engineering applications.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"135 ","pages":"Article 104769"},"PeriodicalIF":5.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142721130","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 DEM analyses of type I fracture characteristics of waste rock aggregate reinforced cemented tailing backfill 废石骨料加固水泥尾矿回填土 I 型断裂特性的实验和 DEM 分析

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-19 DOI: 10.1016/j.tafmec.2024.104764

Tianyu Zhu , Zhonghui Chen , Zhongyu Wang , Jian Cao , Jianshuai Hao , Zihan Zhou

In the downward filling mining method, the fracture of the roof of the filling body with cracks will seriously endanger the lives of the workers. In this study, uniaxial compression tests, splitting tensile tests and three-point bending fracture tests were performed on cemented waste rock tailing backfill (CWTB) with prefabricated notches, and the effect of waste rock aggregate content (10%, 20%, 30%, 40%, and 50%) on the basic mechanical parameters and fracture characteristics of the CWTB was analyzed in conjunction with digital image correlation (DIC) techniques. The safety warning parameter before the unstable fracture of CWTB was proposed. The toughening mechanism of aggregates was revealed. The results show that the incorporation of waste rock aggregate significantly improves the strength, fracture toughness, and fracture energy of CWTB. The multiple toughening mechanisms of waste rock aggregate synergistically improve the crack resistance of CWTB and prolong the time between initiation of cracking and unstable fracture. The content of waste rock aggregate changes the failure modes and crack extension paths of CWTB. Meanwhile, microscopic damage mechanism of CWTB was explored using PFC3D. The simulation results show that compared with cemented tailing backfill (CTB), aggregate-induced crack bifurcation and deflection effects increased the number of microcracks in CWTB, reduce the rate of microcracks in the stable extension period, and make its fracture surface rougher and more tortuous.

在下向充填采矿法中，充填体顶板裂缝断裂将严重危及工人的生命安全。本研究对预制槽口的胶结废石尾矿回填体（CWTB）进行了单轴压缩试验、劈裂拉伸试验和三点弯曲断裂试验，并结合数字图像相关（DIC）技术分析了废石骨料含量（10%、20%、30%、40%和50%）对CWTB基本力学参数和断裂特性的影响。提出了 CWTB 不稳定断裂前的安全预警参数。揭示了聚集体的增韧机理。结果表明，掺入废石骨料可显著提高 CWTB 的强度、断裂韧性和断裂能。废石骨料的多种增韧机制协同提高了 CWTB 的抗裂性能，延长了从开裂到不稳定断裂之间的时间。废石骨料的含量改变了 CWTB 的破坏模式和裂纹扩展路径。同时，利用 PFC3D 对 CWTB 的微观破坏机理进行了探讨。模拟结果表明，与固结尾矿回填（CTB）相比，骨料诱发的裂缝分叉和挠曲效应增加了 CWTB 的微裂缝数量，降低了稳定扩展期的微裂缝速率，并使其断裂面更加粗糙和曲折。

{"title":"Experimental and DEM analyses of type I fracture characteristics of waste rock aggregate reinforced cemented tailing backfill","authors":"Tianyu Zhu , Zhonghui Chen , Zhongyu Wang , Jian Cao , Jianshuai Hao , Zihan Zhou","doi":"10.1016/j.tafmec.2024.104764","DOIUrl":"10.1016/j.tafmec.2024.104764","url":null,"abstract":"<div><div>In the downward filling mining method, the fracture of the roof of the filling body with cracks will seriously endanger the lives of the workers. In this study, uniaxial compression tests, splitting tensile tests and three-point bending fracture tests were performed on cemented waste rock tailing backfill (CWTB) with prefabricated notches, and the effect of waste rock aggregate content (10%, 20%, 30%, 40%, and 50%) on the basic mechanical parameters and fracture characteristics of the CWTB was analyzed in conjunction with digital image correlation (DIC) techniques. The safety warning parameter before the unstable fracture of CWTB was proposed. The toughening mechanism of aggregates was revealed. The results show that the incorporation of waste rock aggregate significantly improves the strength, fracture toughness, and fracture energy of CWTB. The multiple toughening mechanisms of waste rock aggregate synergistically improve the crack resistance of CWTB and prolong the time between initiation of cracking and unstable fracture. The content of waste rock aggregate changes the failure modes and crack extension paths of CWTB. Meanwhile, microscopic damage mechanism of CWTB was explored using PFC3D. The simulation results show that compared with cemented tailing backfill (CTB), aggregate-induced crack bifurcation and deflection effects increased the number of microcracks in CWTB, reduce the rate of microcracks in the stable extension period, and make its fracture surface rougher and more tortuous.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"135 ","pages":"Article 104764"},"PeriodicalIF":5.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142721132","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

Interpolating CTS specimens’ mode I and II stress intensity factors using artificial neural networks 利用人工神经网络插值 CTS 试样的模式 I 和模式 II 应力强度因子

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-19 DOI: 10.1016/j.tafmec.2024.104761

R. Baptista , V. Infante , L.F.P. Borrego , E.R. Sérgio , D.M. Neto , F.V. Antunes

Fracture mechanics parameters, such as the stress intensity factor (SIF), are fundamental for the analysis of fracture, fatigue crack growth and crack paths. SIFs of a cracked body can be determined either experimentally or numerically. Analytical solutions of SIF are very useful, but their determination from discrete values can be extremely complex when there are many independent variables. In this paper, artificial neural networks (ANN) are proposed to predict mode I and II stress intensity factors in a CTS specimen under mixed mode loading conditions. Trained with numerical data, the performance of different network architectures and backpropagation algorithms was assessed. Using at least 10 neurons, in the hidden layers, made it possible for the designed solution to match the performance of analytical solutions. Increasing the number of neurons, allowed the model performance to improve up to 90%, when compared with previous analytical solutions. This increases the quality of fracture and fatigue studies done with the CTS sample.

应力强度因子（SIF）等断裂力学参数是分析断裂、疲劳裂纹生长和裂纹路径的基础。裂纹体的 SIF 可以通过实验或数值方法确定。SIF 的解析解非常有用，但当存在许多独立变量时，从离散值确定 SIF 可能会非常复杂。本文提出了人工神经网络（ANN）来预测混合模式加载条件下 CTS 试样的模式 I 和模式 II 应力强度因子。通过使用数值数据进行训练，评估了不同网络结构和反向传播算法的性能。在隐藏层中至少使用 10 个神经元，可使设计方案与分析方案的性能相匹配。与之前的分析解决方案相比，增加神经元数量可使模型性能提高 90%。这提高了对 CTS 样品进行断裂和疲劳研究的质量。

{"title":"Interpolating CTS specimens’ mode I and II stress intensity factors using artificial neural networks","authors":"R. Baptista , V. Infante , L.F.P. Borrego , E.R. Sérgio , D.M. Neto , F.V. Antunes","doi":"10.1016/j.tafmec.2024.104761","DOIUrl":"10.1016/j.tafmec.2024.104761","url":null,"abstract":"<div><div>Fracture mechanics parameters, such as the stress intensity factor (SIF), are fundamental for the analysis of fracture, fatigue crack growth and crack paths. SIFs of a cracked body can be determined either experimentally or numerically. Analytical solutions of SIF are very useful, but their determination from discrete values can be extremely complex when there are many independent variables. In this paper, artificial neural networks (ANN) are proposed to predict mode I and II stress intensity factors in a CTS specimen under mixed mode loading conditions. Trained with numerical data, the performance of different network architectures and backpropagation algorithms was assessed. Using at least 10 neurons, in the hidden layers, made it possible for the designed solution to match the performance of analytical solutions. Increasing the number of neurons, allowed the model performance to improve up to 90%, when compared with previous analytical solutions. This increases the quality of fracture and fatigue studies done with the CTS sample.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104761"},"PeriodicalIF":5.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142704492","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

Acoustic emission characteristics and cracking mechanism analysis of anisotropic shale containing a circular hole under uniaxial compression 单轴压缩条件下含圆孔的各向异性页岩的声发射特征和裂纹机理分析

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-19 DOI: 10.1016/j.tafmec.2024.104771

Xianhui Feng , Huilin Liu , Xu Chen , Weiche Chang , Kaizong Xia , Qifeng Guo , Liyuan Liu , Mingjie Li

Shale is a kind of layered sedimentary rock widely existing in nature. In slope engineering, tunnel engineering, shale gas engineering and other practical engineering, layer structure and orientation will lead to the structural strength reduction, easy to cause safety accidents. In this study, the acoustic emission (AE) characteristics and fracture modes of shale samples containing a circular hole were investigated by uniaxial compression tests with different bedding angles. The experimental results revealed that the fracture modes of the sample are affected not only by the dip angle of bedding, but also by the stress concentration caused by the hole. Different fracture modes lead to differences in AE characteristics such as ring number, b-value, energy and peak frequency. Compared with shear failure, the cumulative AE count and peak frequency of tensile failure are higher, and the change frequency of the b-value is higher. Additionally, according to the RA-AF distribution characteristics of the shale samples, AF = 10RA + 21 was confirmed as the dividing line of different crack types, and the dividing result was consistent with that of macroscopic cracks. According to this dividing line, the crack evolution process was analyzed, and it was found that the tensile cracks and shear cracks were concentrated in the peak stress and phase of crack steady growth respectively. The study of AE characteristics of shale will provide experimental basis and reference for guiding related engineering practice.

页岩是自然界广泛存在的一种层状沉积岩。在边坡工程、隧道工程、页岩气工程等实际工程中，层状结构和走向会导致结构强度降低，易引发安全事故。本研究通过不同基底角的单轴压缩试验，研究了含圆孔页岩样品的声发射（AE）特性和断裂模式。实验结果表明，样品的断裂模式不仅受到垫层倾角的影响，还受到孔洞造成的应力集中的影响。不同的断裂模式会导致 AE 特性的差异，如环数、b 值、能量和峰值频率。与剪切破坏相比，拉伸破坏的 AE 累积次数和峰值频率更高，b 值的变化频率也更高。此外，根据页岩样品的 RA-AF 分布特征，确定 AF = 10RA + 21 为不同裂纹类型的分界线，其分界结果与宏观裂纹的分界结果一致。根据该分界线分析了裂纹的演变过程，发现拉伸裂纹和剪切裂纹分别集中在应力峰值阶段和裂纹稳定增长阶段。页岩的 AE 特性研究将为指导相关工程实践提供实验依据和参考。

{"title":"Acoustic emission characteristics and cracking mechanism analysis of anisotropic shale containing a circular hole under uniaxial compression","authors":"Xianhui Feng , Huilin Liu , Xu Chen , Weiche Chang , Kaizong Xia , Qifeng Guo , Liyuan Liu , Mingjie Li","doi":"10.1016/j.tafmec.2024.104771","DOIUrl":"10.1016/j.tafmec.2024.104771","url":null,"abstract":"<div><div>Shale is a kind of layered sedimentary rock widely existing in nature. In slope engineering, tunnel engineering, shale gas engineering and other practical engineering, layer structure and orientation will lead to the structural strength reduction, easy to cause safety accidents. In this study, the acoustic emission (AE) characteristics and fracture modes of shale samples containing a circular hole were investigated by uniaxial compression tests with different bedding angles. The experimental results revealed that the fracture modes of the sample are affected not only by the dip angle of bedding, but also by the stress concentration caused by the hole. Different fracture modes lead to differences in AE characteristics such as ring number, <em>b-</em>value, energy and peak frequency. Compared with shear failure, the cumulative AE count and peak frequency of tensile failure are higher, and the change frequency of the <em>b-</em>value is higher. Additionally, according to the RA-AF distribution characteristics of the shale samples, AF = 10RA + 21 was confirmed as the dividing line of different crack types, and the dividing result was consistent with that of macroscopic cracks. According to this dividing line, the crack evolution process was analyzed, and it was found that the tensile cracks and shear cracks were concentrated in the peak stress and phase of crack steady growth respectively. The study of AE characteristics of shale will provide experimental basis and reference for guiding related engineering practice.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"135 ","pages":"Article 104771"},"PeriodicalIF":5.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142721195","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

Study on the mechanisms of time-dependent crack propagation and the gradual collapse of roadways in soft–hard composite strata 软硬复合地层中随时间变化的裂缝扩展和路面逐渐坍塌机理研究

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-17 DOI: 10.1016/j.tafmec.2024.104763

Binxu Wang , Ying Chen , Tingchun Li , Qingwen Zhu , Yiteng Du

As mineral extraction extends to deeper strata, the creep deformation differences between soft and hard rocks are further amplified by high stress. This increases the demand for controlling the lifecycle deformation of soft–hard composite rock roadways (S-HRs). This paper investigates the time-dependent characteristics of soft–hard composite rock composed of mudstone and sandstone (M-SR) via laboratory experiments and the damage bond model previously proposed by the author. The results show that crack propagation in M-SR exhibits a clear time-dependent effect, with the creep damage of mudstone being greater than that of sandstone, and this trend increases over time. Over 90 % of microcracks during the first two creep stages develop and coalesce in the mudstone, whereas crack propagation in the sandstone is inhibited. This process plays a critical guiding role in the final failure mode of the M-SR. After excavation, a tensile stress zone forms around the S-HR, with more drastic changes occurring on the sidewalls. This zone expands over time, whereas the deep compressive stress in the roof and floor shifts toward the sidewalls, exacerbating the depth of sidewall failure and continuously inducing the flow of the rock mass into the roadway from the sidewalls. After 48 days, the deformation of the sidewalls increases by 281 %. Increasing the support of sidewalls is a viable approach to solve this issue, and the support range should extend beyond the stress concentration zone. Leveraging the feedback mechanism between the roof and the sidewalls helps reduce creep damage and deformation on the sidewalls.

随着矿产开采向更深地层延伸，高应力进一步扩大了软岩和硬岩之间的蠕变变形差异。这就增加了控制软硬复合岩路面（S-HR）生命周期变形的要求。本文通过实验室实验和作者之前提出的损伤粘结模型，研究了由泥岩和砂岩组成的软硬复合岩（M-SR）随时间变化的特性。结果表明，M-SR 中的裂纹扩展表现出明显的时间依赖效应，泥岩的蠕变损伤大于砂岩，并且这种趋势随着时间的推移而加剧。在前两个蠕变阶段，90% 以上的微裂缝在泥岩中发展和凝聚，而砂岩中的裂缝扩展受到抑制。这一过程对 M-SR 的最终破坏模式起着至关重要的指导作用。开挖后，S-HR 周围会形成一个拉伸应力区，侧壁会发生更剧烈的变化。随着时间的推移，该区域不断扩大，而顶板和底板的深层压应力则向侧壁移动，加剧了侧壁的破坏深度，并不断诱导岩体从侧壁流入巷道。48 天后，侧壁的变形增加了 281%。增加侧壁支护是解决这一问题的可行方法，支护范围应超出应力集中区。利用车顶和侧壁之间的反馈机制有助于减少侧壁的蠕变损伤和变形。

{"title":"Study on the mechanisms of time-dependent crack propagation and the gradual collapse of roadways in soft–hard composite strata","authors":"Binxu Wang , Ying Chen , Tingchun Li , Qingwen Zhu , Yiteng Du","doi":"10.1016/j.tafmec.2024.104763","DOIUrl":"10.1016/j.tafmec.2024.104763","url":null,"abstract":"<div><div>As mineral extraction extends to deeper strata, the creep deformation differences between soft and hard rocks are further amplified by high stress. This increases the demand for controlling the lifecycle deformation of soft–hard composite rock roadways (S-HRs). This paper investigates the time-dependent characteristics of soft–hard composite rock composed of mudstone and sandstone (M-SR) via laboratory experiments and the damage bond model previously proposed by the author. The results show that crack propagation in M-SR exhibits a clear time-dependent effect, with the creep damage of mudstone being greater than that of sandstone, and this trend increases over time. Over 90 % of microcracks during the first two creep stages develop and coalesce in the mudstone, whereas crack propagation in the sandstone is inhibited. This process plays a critical guiding role in the final failure mode of the M-SR. After excavation, a tensile stress zone forms around the S-HR, with more drastic changes occurring on the sidewalls. This zone expands over time, whereas the deep compressive stress in the roof and floor shifts toward the sidewalls, exacerbating the depth of sidewall failure and continuously inducing the flow of the rock mass into the roadway from the sidewalls. After 48 days, the deformation of the sidewalls increases by 281 %. Increasing the support of sidewalls is a viable approach to solve this issue, and the support range should extend beyond the stress concentration zone. Leveraging the feedback mechanism between the roof and the sidewalls helps reduce creep damage and deformation on the sidewalls.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104763"},"PeriodicalIF":5.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142704495","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

Deep learning for characterizing fracture toughness from the nanoindentation image of a complex heterogeneous medium 利用深度学习从复杂异质介质的纳米压痕图像表征断裂韧性

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-17 DOI: 10.1016/j.tafmec.2024.104759

A. Sakhaee-Pour

Fracture toughness is a fundamental property characterized using nanoindentation, and it typically requires elastic modulus, applied load, and crack length. This study demonstrates that deep learning can predict fracture toughness using only nanoindentation images. A deep-learning model is designed, incorporating a pretrained Visual Geometry Group model with 16 layers (VGG16) and fully connected layers. The study augments 3,546 original nanoindentation images of shale to increase them to 21,276 images and employs the adaptive momentum (Adam) solver with a learning rate of 0.0002. The nanoindentation images contain complex patterns distinct from the simple topologies of homogeneous media, such as pure silica. Results show that the model accurately determines normalized fracture toughness, with a mean squared error (MSE) of 0.0014, indicating that the model effectively learns to interpret the underlying features. Additionally, once trained, the model predicts fracture toughness much faster than the existing approach based on K-means clustering. More importantly, this study suggests that nanoindentation images of complex porous media convey crucial information, including elastic modulus, applied load, and hardness. The results and the proposed model have applications in characterizing heterogeneous media with complex structures.

断裂韧性是利用纳米压痕技术表征的一项基本特性，通常需要弹性模量、外加载荷和裂缝长度。本研究证明，深度学习可以仅利用纳米压痕图像预测断裂韧性。该研究设计了一个深度学习模型，其中包含一个带 16 层（VGG16）和全连接层的预训练视觉几何组模型。研究将页岩的 3546 张原始纳米压痕图像增加到 21276 张，并采用学习率为 0.0002 的自适应动量（Adam）求解器。纳米压痕图像包含有不同于纯硅石等均质介质简单拓扑结构的复杂模式。结果表明，该模型能准确确定归一化断裂韧性，平均平方误差 (MSE) 为 0.0014，表明该模型能有效地学习解释基本特征。此外，一旦经过训练，该模型预测断裂韧性的速度比基于 K-means 聚类的现有方法快得多。更重要的是，这项研究表明，复杂多孔介质的纳米压痕图像能传递关键信息，包括弹性模量、外加载荷和硬度。研究结果和提出的模型可用于表征具有复杂结构的异质介质。

{"title":"Deep learning for characterizing fracture toughness from the nanoindentation image of a complex heterogeneous medium","authors":"A. Sakhaee-Pour","doi":"10.1016/j.tafmec.2024.104759","DOIUrl":"10.1016/j.tafmec.2024.104759","url":null,"abstract":"<div><div>Fracture toughness is a fundamental property characterized using nanoindentation, and it typically requires elastic modulus, applied load, and crack length. This study demonstrates that deep learning can predict fracture toughness using only nanoindentation images. A deep-learning model is designed, incorporating a pretrained Visual Geometry Group model with 16 layers (VGG16) and fully connected layers. The study augments 3,546 original nanoindentation images of shale to increase them to 21,276 images and employs the adaptive momentum (Adam) solver with a learning rate of 0.0002. The nanoindentation images contain complex patterns distinct from the simple topologies of homogeneous media, such as pure silica. Results show that the model accurately determines normalized fracture toughness, with a mean squared error (MSE) of 0.0014, indicating that the model effectively learns to interpret the underlying features. Additionally, once trained, the model predicts fracture toughness much faster than the existing approach based on <em>K</em>-means clustering. More importantly, this study suggests that nanoindentation images of complex porous media convey crucial information, including elastic modulus, applied load, and hardness. The results and the proposed model have applications in characterizing heterogeneous media with complex structures.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"135 ","pages":"Article 104759"},"PeriodicalIF":5.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142721131","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 prefabricated flaw angle on the mechanical properties and failure characteristics of stratified cemented tailings backfill

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-16 DOI: 10.1016/j.tafmec.2024.104760

Shuaijun Chen , Wenjing Qin , Aibing Jin , Yiqing Zhao , Zhihao Li

The process of exposing stratified cemented tailings backfill (SCTB) underground is prone to damage due to blasting disturbances. To investigate the effect of flaws on the mechanical properties and failure characteristics of exposed SCTB, prefabricated flaws were used to simulate blasting damage. In this study, a uniaxial compression test, based on the digital image correlation (DIC) method, was used to investigate the mechanical characteristics of SCTB under different flaw dip angles. Additionally, the Particle Flow Code program was used to analyze the propagation of secondary cracks. The results show that: (1) With an increase in the flaw angle, the uniaxial compressive strength (UCS) of SCTB samples exhibit an initial decrease followed by an increase, and the elastic modulus of SCTB samples exhibit an increase. (2) When the flaw angle is between 0° and 45°, wing cracks and resistance tensile cracks mainly develop at the end of the flaw. For flaw angles between 60° and 75°, coplanar secondary cracks form at the end of the flaw and penetrate the stratified surface. (3) There are three main forms of crack propagation at the stratified surface: cracks passing through the stratified surface without deflecting, cracks deflecting at the stratified surface, and cracks that do not penetrate the stratified surface. (4) When cracks pass through the stratified surface without deflecting, the X-direction stress on both sides of the stratified surface changes synergistically, resulting in a large stress value. When the crack propagation direction deflects at the stratified surface, the X-direction stress differs on both sides, with smaller stress observed on the side away from the flaw. The larger the deflection angle of the crack propagation, the smaller the X-direction stress on the side away from the flaw. These results provide a basis for the stability evaluation and strength design of SCTB with flaws.

{"title":"Effect of prefabricated flaw angle on the mechanical properties and failure characteristics of stratified cemented tailings backfill","authors":"Shuaijun Chen , Wenjing Qin , Aibing Jin , Yiqing Zhao , Zhihao Li","doi":"10.1016/j.tafmec.2024.104760","DOIUrl":"10.1016/j.tafmec.2024.104760","url":null,"abstract":"<div><div>The process of exposing stratified cemented tailings backfill (SCTB) underground is prone to damage due to blasting disturbances. To investigate the effect of flaws on the mechanical properties and failure characteristics of exposed SCTB, prefabricated flaws were used to simulate blasting damage. In this study, a uniaxial compression test, based on the digital image correlation (DIC) method, was used to investigate the mechanical characteristics of SCTB under different flaw dip angles. Additionally, the Particle Flow Code program was used to analyze the propagation of secondary cracks. The results show that: (1) With an increase in the flaw angle, the uniaxial compressive strength (UCS) of SCTB samples exhibit an initial decrease followed by an increase, and the elastic modulus of SCTB samples exhibit an increase. (2) When the flaw angle is between 0° and 45°, wing cracks and resistance tensile cracks mainly develop at the end of the flaw. For flaw angles between 60° and 75°, coplanar secondary cracks form at the end of the flaw and penetrate the stratified surface. (3) There are three main forms of crack propagation at the stratified surface: cracks passing through the stratified surface without deflecting, cracks deflecting at the stratified surface, and cracks that do not penetrate the stratified surface. (4) When cracks pass through the stratified surface without deflecting, the X-direction stress on both sides of the stratified surface changes synergistically, resulting in a large stress value. When the crack propagation direction deflects at the stratified surface, the X-direction stress differs on both sides, with smaller stress observed on the side away from the flaw. The larger the deflection angle of the crack propagation, the smaller the X-direction stress on the side away from the flaw. These results provide a basis for the stability evaluation and strength design of SCTB with flaws.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"135 ","pages":"Article 104760"},"PeriodicalIF":5.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142743173","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

Study on the damage and fracture behaviors of fiber-reinforced cementitious composites by peridynamic simulation 通过周动态模拟研究纤维增强水泥基复合材料的损伤和断裂行为

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-16 DOI: 10.1016/j.tafmec.2024.104758

Man Wang , Liang Li , Jianjun Ma , Jun Wu , Xiuli Du

A novel numerical model for the damage and fracture behaviors of fiber-reinforced cementitious composites (FRCC) is introduced based on Peridynamic (PD) theory. This Peridynamic fiber-reinforced Cementitious Composites (PD-FRCC) model improves the bond-based PD theory’s capability to describe the intrinsic microstructural heterogeneity and macroscopic nonlinear mechanical properties of cementitious by introducing key damage correction factors. A semi-discrete method is used to simulate the reinforcement effect of fibers, where a proportion of cementitious matrix bonds are randomly selected as fiber-reinforced bonds based on fiber content and length. The effectiveness and stability of the proposed numerical model are validated by numerical simulation examples. These examples include tensile tests of single-fiber cementitious plates, static tensile tests of steel-polyethylene hybrid fiber reinforced engineered cementitious composites (ST/PE-ECC), and tensile failure simulations of double-notched beams. The results demonstrate that the proposed numerical model accurately captures the complex morphology and propagation of FRCC cracks, and showcases high predictive accuracy. The significant impact of fiber bridging on material toughness and ductility during crack propagation is emphasized, revealing that fibers not only suppress initial crack growth but also lead crack propagation along complex paths, thereby extending crack propagation time and enhancing fracture resistance.

基于 "周动力"（PD）理论，介绍了纤维增强水泥基复合材料（FRCC）损伤和断裂行为的新型数值模型。该 Peridynamic 纤维增强水泥基复合材料（PD-FRCC）模型通过引入关键损伤校正因子，提高了基于粘接的 PD 理论描述水泥基固有微观结构异质性和宏观非线性力学性能的能力。采用半离散方法模拟纤维的加固效应，即根据纤维含量和长度随机选择一定比例的水泥基粘结作为纤维加固粘结。通过数值模拟实例验证了所提出数值模型的有效性和稳定性。这些实例包括单纤维水泥基板的拉伸试验、钢-聚乙烯混合纤维增强工程水泥基复合材料（ST/PE-ECC）的静态拉伸试验以及双缺口梁的拉伸破坏模拟。结果表明，所提出的数值模型准确地捕捉到了 FRCC 裂纹的复杂形态和扩展过程，具有很高的预测精度。研究强调了纤维桥接在裂纹扩展过程中对材料韧性和延展性的重要影响，揭示了纤维不仅能抑制初始裂纹生长，还能引导裂纹沿复杂路径扩展，从而延长裂纹扩展时间并增强抗断裂性能。

{"title":"Study on the damage and fracture behaviors of fiber-reinforced cementitious composites by peridynamic simulation","authors":"Man Wang , Liang Li , Jianjun Ma , Jun Wu , Xiuli Du","doi":"10.1016/j.tafmec.2024.104758","DOIUrl":"10.1016/j.tafmec.2024.104758","url":null,"abstract":"<div><div>A novel numerical model for the damage and fracture behaviors of fiber-reinforced cementitious composites (FRCC) is introduced based on Peridynamic (PD) theory. This Peridynamic fiber-reinforced Cementitious Composites (PD-FRCC) model improves the bond-based PD theory’s capability to describe the intrinsic microstructural heterogeneity and macroscopic nonlinear mechanical properties of cementitious by introducing key damage correction factors. A semi-discrete method is used to simulate the reinforcement effect of fibers, where a proportion of cementitious matrix bonds are randomly selected as fiber-reinforced bonds based on fiber content and length. The effectiveness and stability of the proposed numerical model are validated by numerical simulation examples. These examples include tensile tests of single-fiber cementitious plates, static tensile tests of steel-polyethylene hybrid fiber reinforced engineered cementitious composites (ST/PE-ECC), and tensile failure simulations of double-notched beams. The results demonstrate that the proposed numerical model accurately captures the complex morphology and propagation of FRCC cracks, and showcases high predictive accuracy. The significant impact of fiber bridging on material toughness and ductility during crack propagation is emphasized, revealing that fibers not only suppress initial crack growth but also lead crack propagation along complex paths, thereby extending crack propagation time and enhancing fracture resistance.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104758"},"PeriodicalIF":5.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142704493","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

Shear mode solutions to penny-shaped crack problems in two-dimensional hexagonal piezoelectric quasicrystal media 二维六边形压电准晶介质中的笔形裂缝问题的剪切模求解

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-16 DOI: 10.1016/j.tafmec.2024.104762

Yuan Li , Shuhang Tang , Pengyun Li , Jingli Ren , Minghao Zhao

This study investigates shear mode penny-shaped crack problems in an infinite three-dimensional body composed of a two-dimensional hexagonal quasicrystal medium with piezoelectric effect. The crack is subjected to a set of shear phonon and phason loadings within the crack plane. This shear mode crack problem is transformed into a mixed boundary value problem in the upper half space. Subsequently, it is elegantly solved utilizing Fabrikant’s potential theory method. The boundary integral–differential equations governing three-dimensional shear mode crack problems in two-dimensional hexagonal piezoelectric quasicrystals are derived with the phonon and phason displacement discontinuities serving as unknown variables. Closed-form solutions for all physical field quantities are presented, not merely limited to the crack surface, but rather extended comprehensively to the entire space. Key fracture mechanics parameters, such as phonon and phason displacement discontinuities, stress intensity factors at the crack tip, and energy release rate, are explicitly derived. Numerical results are provided to validate the obtained analytical solutions and illustrate the distribution of the electric-phason-phonon coupling field around the crack in graphical form. Additionally, these numerical results also compare the fracture mechanics parameters of the chosen piezoelectric quasicrystal with its corresponding non-piezoelectric quasicrystal, thereby investigating the influence of piezoelectric effect on quasicrystals. The obtained solution can be used as a benchmark for the experimental and numerical study of shear mode cracks in piezoelectric quasicrystals.

本研究探讨了由具有压电效应的二维六方准晶介质组成的无限三维体中的剪切模式笔形裂缝问题。该裂缝在裂缝平面内受到一组剪切声子和声子载荷。该剪切模式裂缝问题被转化为上半空间的混合边界值问题。随后，利用 Fabrikant 的势理论方法对其进行了优雅的求解。推导出了二维六方压电准晶体中三维剪切模裂纹问题的边界积分微分方程，并将声子和声子位移不连续作为未知变量。提出了所有物理场量的闭式解，不仅局限于裂纹表面，而是全面扩展到整个空间。明确推导出了关键的断裂力学参数，如声子和法森位移不连续度、裂纹顶端的应力强度因子和能量释放率。提供的数值结果验证了所获得的分析解，并以图表形式说明了裂纹周围电-声子耦合场的分布。此外，这些数值结果还比较了所选压电准晶体与相应非压电准晶体的断裂力学参数，从而研究了压电效应对准晶体的影响。所获得的解决方案可作为压电准晶体剪切模裂纹实验和数值研究的基准。

{"title":"Shear mode solutions to penny-shaped crack problems in two-dimensional hexagonal piezoelectric quasicrystal media","authors":"Yuan Li , Shuhang Tang , Pengyun Li , Jingli Ren , Minghao Zhao","doi":"10.1016/j.tafmec.2024.104762","DOIUrl":"10.1016/j.tafmec.2024.104762","url":null,"abstract":"<div><div>This study investigates shear mode penny-shaped crack problems in an infinite three-dimensional body composed of a two-dimensional hexagonal quasicrystal medium with piezoelectric effect. The crack is subjected to a set of shear phonon and phason loadings within the crack plane. This shear mode crack problem is transformed into a mixed boundary value problem in the upper half space. Subsequently, it is elegantly solved utilizing Fabrikant’s potential theory method. The boundary integral–differential equations governing three-dimensional shear mode crack problems in two-dimensional hexagonal piezoelectric quasicrystals are derived with the phonon and phason displacement discontinuities serving as unknown variables. Closed-form solutions for all physical field quantities are presented, not merely limited to the crack surface, but rather extended comprehensively to the entire space. Key fracture mechanics parameters, such as phonon and phason displacement discontinuities, stress intensity factors at the crack tip, and energy release rate, are explicitly derived. Numerical results are provided to validate the obtained analytical solutions and illustrate the distribution of the electric-phason-phonon coupling field around the crack in graphical form. Additionally, these numerical results also compare the fracture mechanics parameters of the chosen piezoelectric quasicrystal with its corresponding non-piezoelectric quasicrystal, thereby investigating the influence of piezoelectric effect on quasicrystals. The obtained solution can be used as a benchmark for the experimental and numerical study of shear mode cracks in piezoelectric quasicrystals.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104762"},"PeriodicalIF":5.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142704494","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

Numerical prediction and experiments for 3D crack propagation in brittle materials based on 3D-generalized maximum tangential strain criterion 基于三维广义最大切向应变准则的脆性材料三维裂纹扩展数值预测与实验

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-14 DOI: 10.1016/j.tafmec.2024.104747

Yang Ju , Yihao Zhang , Hang Yu

Accurately predicting and tracing the three-dimensional (3D) propagation and fracture trajectory of a crack inside brittle materials is challenging. One difficulty is that the 3D crack propagation exhibits complex I/II/III mixed-mode expansion, and there is a lack of accurate crack initiation criteria and effective simulation methods. In our previous studies, the 3D-generalized maximum tangential strain (3D-GMTSN) criterion was proposed to determine the direction and onset of 3D fracture initiation. In this study, a Python program based on the 3D-GMTSN criterion is developed and integrated into FRANC3D to predict the 3D propagation trajectory of an arbitrary crack inside brittle solids. To verify the reliability of the new method, three different types of 3D crack modes, namely Internal Inclined Cracks Cuboid (IICC), Edge Notched Disc Bend (ENDB), and Three-Point Bending (TPB), are used for fracture experiments. The 3D crack propagation morphology is identified using high-resolution CT imaging techniques. The IICC, ENDB, and TPB models are simulated using the new method and the conventional numerical method based on the maximum shear stress (MSS), maximumtensile stress (MTS), and maximum energy release rate (MERR) criteria. Comparisons indicate that the proposed method based on the 3D-GMTSN criterion can predict the 3D crack propagation trajectory more accurately than the conventional methods.

准确预测和追踪脆性材料内部裂纹的三维（3D）扩展和断裂轨迹具有挑战性。困难之一在于三维裂纹扩展表现出复杂的 I/II/III 混合模式扩展，而且缺乏准确的裂纹起始标准和有效的模拟方法。在之前的研究中，我们提出了三维广义最大切向应变（3D-GMTSN）准则来确定三维断裂的起始方向和起始点。本研究基于 3D-GMTSN 判据开发了 Python 程序，并将其集成到 FRANC3D 中，用于预测脆性固体内部任意裂纹的三维传播轨迹。为了验证新方法的可靠性，在断裂实验中使用了三种不同类型的三维裂纹模式，即内部倾斜裂纹立方体（IICC）、边缘缺口圆盘弯曲（ENDB）和三点弯曲（TPB）。利用高分辨率 CT 成像技术识别三维裂纹扩展形态。使用新方法和基于最大剪切应力 (MSS)、最大拉伸应力 (MTS) 和最大能量释放率 (MERR) 标准的传统数值方法对 IICC、ENDB 和 TPB 模型进行了模拟。比较结果表明，与传统方法相比，基于 3D-GMTSN 准则的拟议方法能更准确地预测三维裂纹扩展轨迹。

{"title":"Numerical prediction and experiments for 3D crack propagation in brittle materials based on 3D-generalized maximum tangential strain criterion","authors":"Yang Ju , Yihao Zhang , Hang Yu","doi":"10.1016/j.tafmec.2024.104747","DOIUrl":"10.1016/j.tafmec.2024.104747","url":null,"abstract":"<div><div>Accurately predicting and tracing the three-dimensional (3D) propagation and fracture trajectory of a crack inside brittle materials is challenging. One difficulty is that the 3D crack propagation exhibits complex I/II/III mixed-mode expansion, and there is a lack of accurate crack initiation criteria and effective simulation methods. In our previous studies, the 3D-generalized maximum tangential strain (3D-GMTSN) criterion was proposed to determine the direction and onset of 3D fracture initiation. In this study, a Python program based on the 3D-GMTSN criterion is developed and integrated into FRANC3D to predict the 3D propagation trajectory of an arbitrary crack inside brittle solids. To verify the reliability of the new method, three different types of 3D crack modes, namely Internal Inclined Cracks Cuboid (IICC), Edge Notched Disc Bend (ENDB), and Three-Point Bending (TPB), are used for fracture experiments. The 3D crack propagation morphology is identified using high-resolution CT imaging techniques. The IICC, ENDB, and TPB models are simulated using the new method and the conventional numerical method based on the maximum shear stress (MSS), maximumtensile stress (MTS), and maximum energy release rate (MERR) criteria. Comparisons indicate that the proposed method based on the 3D-GMTSN criterion can predict the 3D crack propagation trajectory more accurately than the conventional methods.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"135 ","pages":"Article 104747"},"PeriodicalIF":5.0,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142721129","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