Pub Date : 2024-10-19DOI: 10.1016/j.tafmec.2024.104726
John Hebert, M.M. Khonsari
The concept of debonding entropy provides insight into the physical mechanisms of fracture. It sheds light on how the fracture phenomenon is more intimately related to degradation and entropy. This paper aims to investigate the relationships between debonding entropy and fundamental concepts in fracture mechanics. A direct, simple relationship between debonding entropy and the J-integral value at fracture is developed and validated. The validation of this relation displays the connection between fracture mechanics and entropic degradation.
{"title":"On the relation between entropy and crack driving force","authors":"John Hebert, M.M. Khonsari","doi":"10.1016/j.tafmec.2024.104726","DOIUrl":"10.1016/j.tafmec.2024.104726","url":null,"abstract":"<div><div>The concept of debonding entropy provides insight into the physical mechanisms of fracture. It sheds light on how the fracture phenomenon is more intimately related to degradation and entropy. This paper aims to investigate the relationships between debonding entropy and fundamental concepts in fracture mechanics. A direct, simple relationship between debonding entropy and the J-integral value at fracture is developed and validated. The validation of this relation displays the connection between fracture mechanics and entropic degradation.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104726"},"PeriodicalIF":5.0,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532617","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 : 2024-10-18DOI: 10.1016/j.tafmec.2024.104724
Abdalrhaman Koko , Thorsten H. Becker
To characterise mixed-mode fracture, including mode , a combination of Arcan fixture, that offers both in-plane and out-of-plane loading, and stereo digital image correlation (DIC) has proven valuable for measuring in-plane and out-of-plane surface displacement and deformation fields while allowing for direct stress intensity factor (SIF) extraction throughout the tests, but it comes with many caveats. Using stereo DIC, the mixed mode fracture behaviour of PMMA is analysed using a novel mode decomposition technique that combines experimental and analytical approaches. This technique divides the measured displacement field from digital image correlation into three distinct components: a symmetric field (), an in-plane anti-symmetric field (), and an out-of-plane antisymmetric field (), decomposed by a difference operation on the reflected and non-reflected fields about the crack plane. Then, the strain energy release rate of the crack is calculated for each loading mode using finite elements without knowledge of the sample geometry or nominal loading condition. Our work revealed parasitic loading modes induced by the Archan fixture plus other intrinsic sources related to load accommodation. Nevertheless, the calculated SIFs measured during stable crack growth were normalised using different fracture toughness () values with of 1.82 ± 0.32 MPa m0.5, providing the best fit to the fracture loci with an R2 of 0.95. This value agrees well with the ASTM-obtained value of 1.7 MPa m0.5.
{"title":"Mixed-mode fracture: Combination of Arcan fixture and stereo-DIC","authors":"Abdalrhaman Koko , Thorsten H. Becker","doi":"10.1016/j.tafmec.2024.104724","DOIUrl":"10.1016/j.tafmec.2024.104724","url":null,"abstract":"<div><div>To characterise mixed-mode fracture, including mode <span><math><mrow><mi>I</mi><mi>I</mi><mi>I</mi></mrow></math></span>, a combination of Arcan fixture, that offers both in-plane and out-of-plane loading, and stereo digital image correlation (DIC) has proven valuable for measuring in-plane and out-of-plane surface displacement and deformation fields while allowing for direct stress intensity factor (SIF) extraction throughout the tests, but it comes with many caveats. Using stereo DIC, the mixed mode fracture behaviour of PMMA is analysed using a novel mode decomposition technique that combines experimental and analytical approaches. This technique divides the measured displacement field from digital image correlation into three distinct components: a symmetric field (<span><math><msup><mrow><mi>u</mi></mrow><mi>I</mi></msup></math></span>), an in-plane anti-symmetric field (<span><math><msup><mrow><mi>u</mi></mrow><mrow><mi>II</mi></mrow></msup></math></span>), and an out-of-plane antisymmetric field (<span><math><msup><mrow><mi>u</mi></mrow><mrow><mi>III</mi></mrow></msup></math></span>), decomposed by a difference operation on the reflected and non-reflected fields about the crack plane. Then, the strain energy release rate of the crack is calculated for each loading mode using finite elements without knowledge of the sample geometry or nominal loading condition. Our work revealed parasitic loading modes induced by the Archan fixture plus other intrinsic sources related to load accommodation. Nevertheless, the calculated SIFs measured during stable crack growth were normalised using different fracture toughness (<span><math><msub><mi>K</mi><mrow><mi>IC</mi></mrow></msub></math></span>) values with <span><math><msub><mi>K</mi><mrow><mi>IC</mi></mrow></msub></math></span> of 1.82 ± 0.32 MPa m<sup>0.5</sup>, providing the best fit to the fracture loci with an R<sup>2</sup> of 0.95. This value agrees well with the ASTM-obtained value of 1.7 MPa m<sup>0.5</sup>.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104724"},"PeriodicalIF":5.0,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532843","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}
Pub Date : 2024-10-14DOI: 10.1016/j.tafmec.2024.104722
Yanliang Li , Jiming Li , P.G. Ranjith , Yongjiang Luo , Xinxin Zhang , Qilei Yin
Rocks containing varying degrees of microcracks have a significant influence on their mechanical behavior. Understanding the effect of pre-existing microcracks (PEMs) on rock fracture mechanisms has scientific and practical value in areas such as geothermal energy, nuclear waste disposal and deep mining. We employed a thermally induced approach to create PEMs in granite rock, and quantified characteristic parameters of PEMs by visualization methods, focusing on the quantitative relationships between the PEMs and the mechanical strength and acoustic emission (AE) properties of the rock. We find that the distribution characteristics of thermally induced PEMs obey a lognormal distribution, and the length of individual thermally induced PEMs is almost independent of temperature. The density and orientation of PEMs together determine the variation of the longitudinal wave velocity and rock strength, with the effect of microcrack density dominating. The AE signal suggests that PEMs can affect the fracture behavior and fracture mechanism, depending on the relative dominance of pre-existing and stress-induced microcracks. The AF-RA values show that PEMs lead to an important shift in the fracture mechanism of the rock. When the microcrack density is low, tensile mode dominates the rock failure. Conversely, the shear mechanism dominates the rock fracture.
{"title":"Statistical analysis of thermally induced pre-existing microcracks and their influence on fracture behaviours of granite rock","authors":"Yanliang Li , Jiming Li , P.G. Ranjith , Yongjiang Luo , Xinxin Zhang , Qilei Yin","doi":"10.1016/j.tafmec.2024.104722","DOIUrl":"10.1016/j.tafmec.2024.104722","url":null,"abstract":"<div><div>Rocks containing varying degrees of microcracks have a significant influence on their mechanical behavior. Understanding the effect of pre-existing microcracks (PEMs) on rock fracture mechanisms has scientific and practical value in areas such as geothermal energy, nuclear waste disposal and deep mining. We employed a thermally induced approach to create PEMs in granite rock, and quantified characteristic parameters of PEMs by visualization methods, focusing on the quantitative relationships between the PEMs and the mechanical strength and acoustic emission (AE) properties of the rock. We find that the distribution characteristics of thermally induced PEMs obey a lognormal distribution, and the length of individual thermally induced PEMs is almost independent of temperature. The density and orientation of PEMs together determine the variation of the longitudinal wave velocity and rock strength, with the effect of microcrack density dominating. The AE signal suggests that PEMs can affect the fracture behavior and fracture mechanism, depending on the relative dominance of pre-existing and stress-induced microcracks. The AF-RA values show that PEMs lead to an important shift in the fracture mechanism of the rock. When the microcrack density is low, tensile mode dominates the rock failure. Conversely, the shear mechanism dominates the rock fracture.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104722"},"PeriodicalIF":5.0,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142437827","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.tafmec.2024.104721
Mengxi Wei , Lan Qiao , Liyun Li , Qingwen Li , Lu Chen
The flaws (fractures) widely existing in rock mass pose a threat on the stability of many underground cavities. This study aims at investigating the failure process of a cavity affected by adjacent flaws. A number of slate specimens containing a circular cavity and a pre-existing flaw pair were tested under uniaxial compression. Varied flaw configurations were obtained by changing the flaw inclination angle with respect to horizontal and the spacing between flaw pair and cavity. Three main types of cracks emanated from the pre-existing flaw tips, and played a dominant role in the failure process of cavity, comprising primary wing cracks (tensile cracks) and two types of secondary cracks (quasi-coplanar shear cracks and oblique shear cracks). The initiation and propagation of these cracks were highly dependent on the flaw pair configurations. When the pre-existing flaw pairs were non-parallel to the loading direction, (1) mostly, coalescence occurred both in the tensile and compressive stress concentration regions around cavity; (2) in most cases, the quasi-coplanar and oblique shear cracks were the predominant cracks leading to the coalescence between the compressive stress concentration regions of cavity and the pre-existing flaw pair tips. When the pre-existing flaws were parallel to the loading direction, the combination of inclined shear cracks and tensile cracks or inclined shear cracks only dominated the failure of cavity. The initiation angles of wing cracks, quasi-coplanar shear cracks and oblique shear cracks agreed well with the theoretical predictions by the maximum tangential strain criterion (MTSN), Mohr-Coulomb criterion (M−C) and maximum shear stress criterion (MSS), respectively.
{"title":"Crack coalescence and failure behaviors in slate specimens containing a circular cavity and a pre-existing flaw pair under uniaxial compression","authors":"Mengxi Wei , Lan Qiao , Liyun Li , Qingwen Li , Lu Chen","doi":"10.1016/j.tafmec.2024.104721","DOIUrl":"10.1016/j.tafmec.2024.104721","url":null,"abstract":"<div><div>The flaws (fractures) widely existing in rock mass pose a threat on the stability of many underground cavities. This study aims at investigating the failure process of a cavity affected by adjacent flaws. A number of slate specimens containing a circular cavity and a pre-existing flaw pair were tested under uniaxial compression. Varied flaw configurations were obtained by changing the flaw inclination angle with respect to horizontal and the spacing between flaw pair and cavity. Three main types of cracks emanated from the pre-existing flaw tips, and played a dominant role in the failure process of cavity, comprising primary wing cracks (tensile cracks) and two types of secondary cracks (quasi-coplanar shear cracks and oblique shear cracks). The initiation and propagation of these cracks were highly dependent on the flaw pair configurations. When the pre-existing flaw pairs were non-parallel to the loading direction, (1) mostly, coalescence occurred both in the tensile and compressive stress concentration regions around cavity; (2) in most cases, the quasi-coplanar and oblique shear cracks were the predominant cracks leading to the coalescence between the compressive stress concentration regions of cavity and the pre-existing flaw pair tips. When the pre-existing flaws were parallel to the loading direction, the combination of inclined shear cracks and tensile cracks or inclined shear cracks only dominated the failure of cavity. The initiation angles of wing cracks, quasi-coplanar shear cracks and oblique shear cracks agreed well with the theoretical predictions by the maximum tangential strain criterion (MTSN), Mohr-Coulomb criterion (M−C) and maximum shear stress criterion (MSS), respectively.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104721"},"PeriodicalIF":5.0,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142444601","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}
Based on the distributed dislocation function, the complex function of arbitrary position and branch cross-crack group under hydraulic-mechanical in the infinite plate is derived and the maximum Mode I and Mode II stress intensity factors (SIFs) of cross-crack group are obtained. The influence of cross-crack group geometry parameters on the maximum SIFs is analyzed and the multiple cross-cracks dangerous zone is obtained. Using the maximum shear and tensile SIF ratio criterion as a basis, the initiation process of double cross-cracks is predicted and verified by red sandstone double cross-cracks uniaxial compression test. Results show that for the double cross-crack in an infinite plate, h/a should be greater than 8 and the value of α2 should not range from 75° to 90° to avoid possible cracking. For the triple cross-crack in an infinite plate, when the water pressure is low (less than 5 MPa), the influence of the stress field exceeds the influence of water pressure. For red sandstone samples with double cross-cracks under uniaxial compression, the inner tips of cross-cracks always connected and penetrated and the inner and outer tips of cross-cracks often eventually joined together. The multiple cross-crack initiation criterion was validated by the good agreement between the test results and the prediction results of red sandstone with double cross-cracks. All the initiation mechanisms are Mode I fracture.
基于分布式位错函数，推导了无限板在水力机械作用下任意位置和分支交叉裂纹组的复函数，并得到了交叉裂纹组的最大模态 I 和模态 II 应力强度因子（SIF）。分析了交叉裂纹组几何参数对最大 SIF 的影响，并得出了多交叉裂纹危险区。以最大剪切和拉伸 SIF 比准则为基础，预测了双交叉裂缝的起始过程，并通过红砂岩双交叉裂缝单轴压缩试验进行了验证。结果表明，对于无限板中的双交叉裂缝，h/a 应大于 8，α2 的值不应在 75° 至 90° 之间，以避免可能出现的裂缝。对于无限板中的三重交叉裂缝，当水压较低时（小于 5 兆帕），应力场的影响超过水压的影响。对于在单轴压缩条件下出现双交叉裂缝的红砂岩样品，交叉裂缝的内侧尖端总是相连并贯通，交叉裂缝的内侧尖端和外侧尖端往往最终连接在一起。红砂岩双交叉裂缝的测试结果与预测结果之间的良好一致性验证了多重交叉裂缝起始标准。所有的起始机制都是模式 I 断裂。
{"title":"Cross-crack group interaction and initiation mechanism under hydraulic-mechanical coupling","authors":"Qingqing Shen, Lvlin Xiang, Qiyun Wang, Jiajun Zeng, Zhengyang Tang","doi":"10.1016/j.tafmec.2024.104720","DOIUrl":"10.1016/j.tafmec.2024.104720","url":null,"abstract":"<div><div>Based on the distributed dislocation function, the complex function of arbitrary position and branch cross-crack group under hydraulic-mechanical in the infinite plate is derived and the maximum Mode I and Mode II stress intensity factors (SIFs) of cross-crack group are obtained. The influence of cross-crack group geometry parameters on the maximum SIFs is analyzed and the multiple cross-cracks dangerous zone is obtained. Using the maximum shear and tensile SIF ratio criterion as a basis, the initiation process of double cross-cracks is predicted and verified by red sandstone double cross-cracks uniaxial compression test. Results show that for the double cross-crack in an infinite plate, <em>h/a</em> should be greater than 8 and the value of <em>α</em><sub>2</sub> should not range from 75° to 90° to avoid possible cracking. For the triple cross-crack in an infinite plate, when the water pressure is low (less than 5 MPa), the influence of the stress field exceeds the influence of water pressure. For red sandstone samples with double cross-cracks under uniaxial compression, the inner tips of cross-cracks always connected and penetrated and the inner and outer tips of cross-cracks often eventually joined together. The multiple cross-crack initiation criterion was validated by the good agreement between the test results and the prediction results of red sandstone with double cross-cracks. All the initiation mechanisms are Mode I fracture.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104720"},"PeriodicalIF":5.0,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142444600","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.tafmec.2024.104718
Wenjing Zhou , Haitao Li , Zhifan Wang , Linji Ying , Zi’ang Wang , Shuwei Chen , Yibo Li , Jixin Chen , Ottavia Corbi
This study investigates the Mode II fracture properties in the RL and TL planes of parallel neosinocalamus affinis bamboo strand lumber. Eighty End-Notched Flexure (ENF) specimens were designed, varying pre-crack lengths and specimen widths. Digital Image Correlation (DIC) was employed to analyze strain variations during the development of the fracture process zone (FPZ) and crack propagation stages. The Compliance Based Beam Method (CBBM) and equivalent crack length calculations were used to determine the strain energy release rate (GIIC) of PNABSL. R curves and crack growth rate curves revealed that crack propagation in the RL and TL planes. The results indicated that Mode II fracture propagation in both the RL and TL planes of PNABSL predominantly exhibited self-similar cracking, though the fracture surfaces were rough and uneven, with noticeable fiber bridging. The study found that Mode II fracture propagation was less stable in the RL plane compared to the TL plane, which is attributed to the easier fracturing of thick-walled fiber cells in the RL plane. The critical strain energy release rate for PNABSL was determined, offering valuable insights into its fracture behavior.
本研究探讨了平行新竹刨花板在 RL 和 TL 平面上的模式 II 断裂特性。研究人员设计了八十个端面缺口挠曲（ENF）试样，试样的预裂缝长度和宽度各不相同。采用数字图像关联法（DIC）分析断裂过程区（FPZ）和裂纹扩展阶段的应变变化。采用基于顺应性的梁法（CBBM）和等效裂纹长度计算来确定 PNABSL 的应变能释放率（GIIC）。R 曲线和裂纹增长率曲线显示裂纹在 RL 和 TL 平面上扩展。结果表明，PNABSL 的 RL 和 TL 平面上的模式 II 断裂扩展主要表现为自相似裂纹，但断裂面粗糙不平，并伴有明显的纤维桥接。研究发现，与 TL 面相比，RL 面的模式 II 断裂扩展稳定性较差，这是因为 RL 面的厚壁纤维单元更容易断裂。研究还确定了 PNABSL 的临界应变能释放率，为了解其断裂行为提供了宝贵的资料。
{"title":"Mode II fracture properties of parallel neosinocalamus affinis bamboo strand lumber","authors":"Wenjing Zhou , Haitao Li , Zhifan Wang , Linji Ying , Zi’ang Wang , Shuwei Chen , Yibo Li , Jixin Chen , Ottavia Corbi","doi":"10.1016/j.tafmec.2024.104718","DOIUrl":"10.1016/j.tafmec.2024.104718","url":null,"abstract":"<div><div>This study investigates the Mode II fracture properties in the RL and TL planes of parallel <em>neosinocalamus affinis</em> bamboo strand lumber. Eighty End-Notched Flexure (ENF) specimens were designed, varying pre-crack lengths and specimen widths. Digital Image Correlation (DIC) was employed to analyze strain variations during the development of the fracture process zone (FPZ) and crack propagation stages. The Compliance Based Beam Method (CBBM) and equivalent crack length calculations were used to determine the strain energy release rate (<em>G</em><sub>II</sub><sub>C</sub>) of PNABSL. R curves and crack growth rate curves revealed that crack propagation in the RL and TL planes. The results indicated that Mode II fracture propagation in both the RL and TL planes of PNABSL predominantly exhibited self-similar cracking, though the fracture surfaces were rough and uneven, with noticeable fiber bridging. The study found that Mode II fracture propagation was less stable in the RL plane compared to the TL plane, which is attributed to the easier fracturing of thick-walled fiber cells in the RL plane. The critical strain energy release rate for PNABSL was determined, offering valuable insights into its fracture behavior.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104718"},"PeriodicalIF":5.0,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532839","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.tafmec.2024.104719
Yong Niu , Zewen Chen , Shengqi Yang , Yunjin Hu , Bolong Liu , Caijun Shao , Yanhui Guo
Comprehending the cracking evolution and failure mechanism of flawed rocks under compression-dominating stresses is essential to evaluating the stability of rock engineering. In this work, a newly developed geometry-constraint-based non-ordinary state-based peridynamic (GC-NOSBPD) theory that can eliminate the numerical oscillation is applied to predict the development of new cracks of flawed rocks under compression-dominating stresses. The failure of bonds between particles is judged by the bond-associated stress-based fracture criteria. The cracking evolution trajectories of semi-disc and disc specimens containing flaws are traced. The effects of flaw inclination angle on the cracking trajectories are analyzed. The cracking evolution paths of rock-like specimens with two flaws under uniaxial and biaxial compression are molded. The effects of confining stress on the growth of new cracks are investigated. The confining stress restrains the propagation of tensile cracks, but it is easy to promote the growth of shear cracks. The concentration and transfer effects of stress can plainly revel the failure mechanism of flawed rocks. The present numerical method is reasonable to predict the tensile and shear failure modes of flawed specimens under compression-dominating stresses.
{"title":"Cracking evolution and failure mechanism of brittle rocks containing pre-existing flaws under compression-dominating stresses: Insight from numerical approach","authors":"Yong Niu , Zewen Chen , Shengqi Yang , Yunjin Hu , Bolong Liu , Caijun Shao , Yanhui Guo","doi":"10.1016/j.tafmec.2024.104719","DOIUrl":"10.1016/j.tafmec.2024.104719","url":null,"abstract":"<div><div>Comprehending the cracking evolution and failure mechanism of flawed rocks under compression-dominating stresses is essential to evaluating the stability of rock engineering. In this work, a newly developed geometry-constraint-based non-ordinary state-based peridynamic (GC-NOSBPD) theory that can eliminate the numerical oscillation is applied to predict the development of new cracks of flawed rocks under compression-dominating stresses. The failure of bonds between particles is judged by the bond-associated stress-based fracture criteria. The cracking evolution trajectories of semi-disc and disc specimens containing flaws are traced. The effects of flaw inclination angle on the cracking trajectories are analyzed. The cracking evolution paths of rock-like specimens with two flaws under uniaxial and biaxial compression are molded. The effects of confining stress on the growth of new cracks are investigated. The confining stress restrains the propagation of tensile cracks, but it is easy to promote the growth of shear cracks. The concentration and transfer effects of stress can plainly revel the failure mechanism of flawed rocks. The present numerical method is reasonable to predict the tensile and shear failure modes of flawed specimens under compression-dominating stresses.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104719"},"PeriodicalIF":5.0,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441439","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.tafmec.2024.104716
Minghua Lin , Wei Yang , Baiquan Lin , Yang Shen , Xiangliang Zhang , Ting Liu , Tong Liu
In-situ stress plays a pivotal role in controlling both the propagation speed and trajectory of blast-induced cracks. Previous studies have primarily placed emphasis on the qualitative analysis of the propagation morphology of such cracks, but the principal stress axis rotation effect under static-dynamic coupling loading was ignored. Consequently, the mechanical mechanism of the propagation of blast-induced cracks has not been figured out yet. In this study, a combination of laboratory tests, theoretical analysis, and numerical simulations was employed to explore the influence mechanism of the principal stress axis rotation effect on the propagation of blast-induced cracks under in-situ stress. The results suggest that the hydrostatic pressure does not change the propagation trajectory of blast-induced cracks, but a higher hydrostatic pressure will inhibit both their propagation speed and length. In contrast, the deviatoric stress can change the propagation trajectory of blast-induced cracks, and a higher deviatoric stress makes it easier for blast-induced cracks to deflect to the maximum loading stress direction. Besides, the propagation of blast-induced cracks exhibits different features in different stages under in-situ stress. In the zone near the blast source, the dynamic stress is dominant; the maximum principal stress of the mass points is distributed in the radial direction; and blast-induced cracks expand mainly along the radial direction. On the contrary, in the zone far from the blast source, the static load is dominant; the maximum stress direction of the mass point alters to the maximum loading stress direction; and blast-induced cracks deflect from the radial direction to the maximum loading stress direction. Therefore, the propagation of blast-induced cracks under in-situ stress is a dynamic process in which dynamic and static stresses compete for crack initiation, and the changes in both stress value and principal stress direction are identified as the main reasons for the deflection of blast-induced cracks.
{"title":"Influence mechanism of the principal stress axis rotation effect on the propagation of blast-induced cracks under in-situ stress","authors":"Minghua Lin , Wei Yang , Baiquan Lin , Yang Shen , Xiangliang Zhang , Ting Liu , Tong Liu","doi":"10.1016/j.tafmec.2024.104716","DOIUrl":"10.1016/j.tafmec.2024.104716","url":null,"abstract":"<div><div>In-situ stress plays a pivotal role in controlling both the propagation speed and trajectory of blast-induced cracks. Previous studies have primarily placed emphasis on the qualitative analysis of the propagation morphology of such cracks, but the principal stress axis rotation effect under static-dynamic coupling loading was ignored. Consequently, the mechanical mechanism of the propagation of blast-induced cracks has not been figured out yet. In this study, a combination of laboratory tests, theoretical analysis, and numerical simulations was employed to explore the influence mechanism of the principal stress axis rotation effect on the propagation of blast-induced cracks under in-situ stress. The results suggest that the hydrostatic pressure does not change the propagation trajectory of blast-induced cracks, but a higher hydrostatic pressure will inhibit both their propagation speed and length. In contrast, the deviatoric stress can change the propagation trajectory of blast-induced cracks, and a higher deviatoric stress makes it easier for blast-induced cracks to deflect to the maximum loading stress direction. Besides, the propagation of blast-induced cracks exhibits different features in different stages under in-situ stress. In the zone near the blast source, the dynamic stress is dominant; the maximum principal stress of the mass points is distributed in the radial direction; and blast-induced cracks expand mainly along the radial direction. On the contrary, in the zone far from the blast source, the static load is dominant; the maximum stress direction of the mass point alters to the maximum loading stress direction; and blast-induced cracks deflect from the radial direction to the maximum loading stress direction. Therefore, the propagation of blast-induced cracks under in-situ stress is a dynamic process in which dynamic and static stresses compete for crack initiation, and the changes in both stress value and principal stress direction are identified as the main reasons for the deflection of blast-induced cracks.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104716"},"PeriodicalIF":5.0,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528456","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.tafmec.2024.104715
Rui-Guo Yan , Wen-Jing Wang , Ran Ding , Yi-Ming Zeng , Wei Shan , Yi Yin , Xi-Shu Wang
As critical load-bearing components of high-speed trains, the design and evaluation of axles primarily adhere to the principle of infinite life, supplemented by systematic flaw detection to ensure their operational safety. The establishment of detection intervals heavily depends on damage tolerance analysis informed by fracture mechanics. The size effect has a great influence on the fracture mechanical properties of materials, and how to accurately assess the remaining life considering the dimensional effects has been an open question in terms of safety in the railroad industry. Consequently, this research focuses on full-scale axle crack propagation tests, exploring the fracture mechanics properties critical to the life analysis of full-scale axle cracks under very high cycle fatigue (VHCF) condition. The findings demonstrate that size effects profoundly affect the fatigue fracture properties of high-speed train axles, especially regarding fatigue crack growth thresholds. Importantly, within the stable growth region, variations in fatigue crack growth rates across different scales prove to be minimal. Subsequently, a finite element model of the full-scale axle was established using the fatigue crack growth rate curve derived from experimental data. The validity of this FEA model was confirmed through bench test results, and predictions of the residual life for axles with cracks were formulated. This comprehensive analysis provides the foundation for developing an ultrasonic detection interval schedule for axles.
{"title":"Research on size effects in fracture properties and residual life prediction for high-speed train axles","authors":"Rui-Guo Yan , Wen-Jing Wang , Ran Ding , Yi-Ming Zeng , Wei Shan , Yi Yin , Xi-Shu Wang","doi":"10.1016/j.tafmec.2024.104715","DOIUrl":"10.1016/j.tafmec.2024.104715","url":null,"abstract":"<div><div>As critical load-bearing components of high-speed trains, the design and evaluation of axles primarily adhere to the principle of infinite life, supplemented by systematic flaw detection to ensure their operational safety. The establishment of detection intervals heavily depends on damage tolerance analysis informed by fracture mechanics. The size effect has a great influence on the fracture mechanical properties of materials, and how to accurately assess the remaining life considering the dimensional effects has been an open question in terms of safety in the railroad industry. Consequently, this research focuses on full-scale axle crack propagation tests, exploring the fracture mechanics properties critical to the life analysis of full-scale axle cracks under very high cycle fatigue (VHCF) condition. The findings demonstrate that size effects profoundly affect the fatigue fracture properties of high-speed train axles, especially regarding fatigue crack growth thresholds. Importantly, within the stable growth region, variations in fatigue crack growth rates across different scales prove to be minimal. Subsequently, a finite element model of the full-scale axle was established using the fatigue crack growth rate curve derived from experimental data. The validity of this FEA model was confirmed through bench test results, and predictions of the residual life for axles with cracks were formulated. This comprehensive analysis provides the foundation for developing an ultrasonic detection interval schedule for axles.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104715"},"PeriodicalIF":5.0,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532838","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.tafmec.2024.104709
Xiang Yu , Jianping Zuo , Lingto Mao , Ying Li , Liu Yang
Rock-like containing non-parallel conjugate flaws specimens (NPCFS) were prepared and uniaxial compression crack propagation tests were conducted employing acoustic emission (AE) and digital image correlation (DIC) techniques. The results show that: the angle of conjugate unilateral cracks increases, the average load-bearing capacity of the rock rises. Dominant frequencies from different conjugate defect angles exhibit distinct bimodal characteristics (low-frequency: 80–140 kHz, intermediate-frequency: 260–320 kHz). The concept of AE dominant frequency ratio β is proposed and introduced to quantify the strength of macro-scale failure of the specimens. The AE multiparameter is proposed to predict the failure load, and the mean value of failure load is predicted to be in the range of 86–93 % (failure load), the prediction interval of Ib value is in the range of 95–99 %, the prediction interval of critical slowing down variance value is in the range of 90–95 %, while the prediction interval of autocorrelation coefficient is in the range of 83–90 %. A favorable correlation was observed between AE events in NPCFS and surface deformations observed through DIC technology. Both ends of the conjugate flaw cannot propagate simultaneously; once one extends, the other ceases further expansion, forming a primary failure line that propagates towards the direction of the primary compressive stress.
{"title":"Crack propagation behavior and failure prediction of rocks with non-parallel conjugate flaws: Insights from the perspective of acoustic emission and DIC","authors":"Xiang Yu , Jianping Zuo , Lingto Mao , Ying Li , Liu Yang","doi":"10.1016/j.tafmec.2024.104709","DOIUrl":"10.1016/j.tafmec.2024.104709","url":null,"abstract":"<div><div>Rock-like containing non-parallel conjugate flaws specimens (NPCFS) were prepared and uniaxial compression crack propagation tests were conducted employing acoustic emission (AE) and digital image correlation (DIC) techniques. The results show that: the angle of conjugate unilateral cracks increases, the average load-bearing capacity of the rock rises. Dominant frequencies from different conjugate defect angles exhibit distinct bimodal characteristics (low-frequency: 80–140 kHz, intermediate-frequency: 260–320 kHz). The concept of AE dominant frequency ratio <em>β</em> is proposed and introduced to quantify the strength of macro-scale failure of the specimens. The AE multiparameter is proposed to predict the failure load, and the mean value of failure load is predicted to be in the range of 86–93 % (failure load), the prediction interval of <em>Ib</em> value is in the range of 95–99 %, the prediction interval of critical slowing down variance value is in the range of 90–95 %, while the prediction interval of autocorrelation coefficient is in the range of 83–90 %. A favorable correlation was observed between AE events in NPCFS and surface deformations observed through DIC technology. Both ends of the conjugate flaw cannot propagate simultaneously; once one extends, the other ceases further expansion, forming a primary failure line that propagates towards the direction of the primary compressive stress.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"134 ","pages":"Article 104709"},"PeriodicalIF":5.0,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441438","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号