Pub Date : 2024-10-09DOI: 10.1016/j.tafmec.2024.104712
The fracture mechanical property of coal rock constitutes an important mechanical constraint for hydraulic fracturing of coal reservoir, and its three-dimensional fracture characteristics hold great significance for coal-bed methane mining. In this study, non-invasive methods were employed to investigate the pore structure and permeability of coal, aiming to understand the gas storage, distribution, and mobility of coal from various regions. To assess the influence of geological stress on coal during coal-bed methane mining, a three-point bending test was conducted to determine the characteristics of coal I/III mixed fractures. The experimental results indicate that with the decrease of the modal mixing parameter Me, the fracture area expends, the fracture load Pf and fracture energy Ef increase, while the fracture toughness declines. The 3D fracture criterion is utilized to predict the toughness ratio of coal rock I/III mixed fracture. The 3D-MTS and 3D-MMTSN criteria offer the upper and lower limits of prediction respectively. The 3D-MTSED criterion proves to be a more appropriate fracture criterion for analyzing the 3D fracture.
煤岩的断裂力学性质是煤储层水力压裂的重要力学约束条件，其三维断裂特征对煤层气开采具有重要意义。本研究采用非侵入方法研究煤的孔隙结构和渗透性，旨在了解不同地区煤的瓦斯储存、分布和流动性。为评估煤层气开采过程中地质应力对煤炭的影响，进行了三点弯曲试验，以确定煤炭 I/III 混合裂缝的特征。实验结果表明，随着模态混合参数 Me 的减小，断裂面积增大，断裂载荷 Pf 和断裂能 Ef 增加，而断裂韧性下降。利用三维断裂准则预测了煤岩 I/III 混合断裂的韧性比。3D-MTS 和 3D-MMTSN 准则分别提供了预测的上限和下限。事实证明，3D-MTSED 准则是分析三维断裂的更合适的断裂准则。
{"title":"Study on I/III mixed fracture characteristics of coal in different regions of China","authors":"","doi":"10.1016/j.tafmec.2024.104712","DOIUrl":"10.1016/j.tafmec.2024.104712","url":null,"abstract":"<div><div>The fracture mechanical property of coal rock constitutes an important mechanical constraint for hydraulic fracturing of coal reservoir, and its three-dimensional fracture characteristics hold great significance for coal-bed methane mining. In this study, non-invasive methods were employed to investigate the pore structure and permeability of coal, aiming to understand the gas storage, distribution, and mobility of coal from various regions. To assess the influence of geological stress on coal during coal-bed methane mining, a three-point bending test was conducted to determine the characteristics of coal I/III mixed fractures. The experimental results indicate that with the decrease of the modal mixing parameter M<sup>e</sup>, the fracture area expends, the fracture load P<sub>f</sub> and fracture energy E<sub>f</sub> increase, while the fracture toughness declines. The 3D fracture criterion is utilized to predict the toughness ratio of coal rock I/III mixed fracture. The 3D-MTS and 3D-MMTSN criteria offer the upper and lower limits of prediction respectively. The 3D-MTSED criterion proves to be a more appropriate fracture criterion for analyzing the 3D fracture.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433995","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.tafmec.2024.104705
Supercritical CO2 (SC-CO2), as an innovative non-aqueous fracturing fluid, has gained extensive application in arid regions. However, its influence on the fracture propagation behavior of shale in very short timescales remains poorly understood. Therefore, a series of three-point bending tests were conducted on shale samples with 0°-90° bedding inclinations. To describe the influence of water-heat-SC-CO2 treatment, a damage fracture constitutive model based on a normal distribution was developed. The theoretical fitting curves of this constitutive model agree well with the experimental results. The whole crack propagation processes were captured using the ultra-fast time resolution method, achieving a time resolution of fast to 15 ps. Identical three-point bending tests were repeated after subjecting the shale samples to water-heat-SC-CO2 treatment for 48 h. The experimental results reveal that after the water-heat-SC-CO2 treatment, there were significant changes in the key mechanical parameters of shale samples. Moreover, the influence of water-heat-SC-CO2 was observed to increase progressively with the bedding inclinations. And by combining the image captured by the ultra-fast time resolution method with this constitutive model, the fracture behavior change of the shale sample after water-heat-SC-CO2 treatment predominantly is affected by the weak planes of shale, with negligible influence on the matrix.
{"title":"The influence of SC-CO2 on the shales’ fracture behavior described by using ultra-fast time resolution method and the damage fracture constitutive model: A case study of the Cretaceous Qingshankou formation in Gulong Depression, Songliao Basin, NE China","authors":"","doi":"10.1016/j.tafmec.2024.104705","DOIUrl":"10.1016/j.tafmec.2024.104705","url":null,"abstract":"<div><div>Supercritical CO<sub>2</sub> (SC-CO<sub>2</sub>), as an innovative non-aqueous fracturing fluid, has gained extensive application in arid regions. However, its influence on the fracture propagation behavior of shale in very short timescales remains poorly understood. Therefore, a series of three-point bending tests were conducted on shale samples with 0°-90° bedding inclinations. To describe the influence of water-heat-SC-CO<sub>2</sub> treatment, a damage fracture constitutive model based on a normal distribution was developed. The theoretical fitting curves of this constitutive model agree well with the experimental results. The whole crack propagation processes were captured using the ultra-fast time resolution method, achieving a time resolution of fast to 15 ps. Identical three-point bending tests were repeated after subjecting the shale samples to water-heat-SC-CO<sub>2</sub> treatment for 48 h. The experimental results reveal that after the water-heat-SC-CO<sub>2</sub> treatment, there were significant changes in the key mechanical parameters of shale samples. Moreover, the influence of water-heat-SC-CO<sub>2</sub> was observed to increase progressively with the bedding inclinations. And by combining the image captured by the ultra-fast time resolution method with this constitutive model, the fracture behavior change of the shale sample after water-heat-SC-CO<sub>2</sub> treatment predominantly is affected by the weak planes of shale, with negligible influence on the matrix.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433991","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.tafmec.2024.104714
The phase field model is a promising method for simulating fatigue crack growth (FCG) behavior. However, the conventional phase field (PF) model may not adequately account for constraint effects, where fracture toughness is affected by geometries. Therefore, stress triaxiality is incorporated into the PF model by modifying the fracture energy release rates to consider constraint effects. The model successfully simulates the FCG behavior of different geometries, such as CT, SENB, and MT specimens, as well as the mixed-mode FCG behavior of CTS specimens and other complex geometries. All simulations agree well with experiments, proving that our model is capable to capture the constraint effects in FCG behavior. These findings indicate that stress triaxiality is important to capture the constraint effects.
{"title":"An improved phase-field model for fatigue crack growth considering constraint effects","authors":"","doi":"10.1016/j.tafmec.2024.104714","DOIUrl":"10.1016/j.tafmec.2024.104714","url":null,"abstract":"<div><div>The phase field model is a promising method for simulating fatigue crack growth (FCG) behavior. However, the conventional phase field (PF) model may not adequately account for constraint effects, where fracture toughness is affected by geometries. Therefore, stress triaxiality is incorporated into the PF model by modifying the fracture energy release rates to consider constraint effects. The model successfully simulates the FCG behavior of different geometries, such as CT, SENB, and MT specimens, as well as the mixed-mode FCG behavior of CTS specimens and other complex geometries. All simulations agree well with experiments, proving that our model is capable to capture the constraint effects in FCG behavior. These findings indicate that stress triaxiality is important to capture the constraint effects.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433993","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.tafmec.2024.104710
A new mixed mode I/II fracture criterion based on strain energy release rate theory is proposed for investigating fracture behavior in cracked functionally graded materials. In this study, the crack is assumed to be located along the material gradation and within the brittle side of the material. For the first time in this type of material, the fracture process zone and the energy dissipated in this region are considered to enhance the prediction accuracy of the proposed criterion. The mechanical and fracture properties of the damage zone are characterized using the microcrack density parameter. A novel method for manufacturing functionally graded materials is introduced, offering numerous advantages by controlling the gel time of the resin. The critical mixed mode and pure mode II fracture toughness of the fabricated specimens are determined through three-point and four-point bending tests. A comparison of the experimental data with the fracture limit curve demonstrates the effectiveness of the newly proposed criterion for investigating mixed mode fracture in functionally graded materials.
基于应变能释放率理论，提出了一种新的 I/II 混合模式断裂准则，用于研究开裂功能分级材料的断裂行为。在这项研究中，假定裂缝位于材料的脆性侧，并沿着材料的梯度分布。在这类材料中，首次考虑了断裂过程区和在该区域耗散的能量，以提高拟议准则的预测精度。利用微裂纹密度参数对损伤区的机械和断裂特性进行了表征。介绍了一种制造功能分级材料的新方法，该方法通过控制树脂的凝胶时间提供了诸多优势。通过三点和四点弯曲试验，确定了制造试样的临界混合模式和纯模式 II 断裂韧性。通过将实验数据与断裂极限曲线进行比较，证明了新提出的标准在研究功能分级材料混合模式断裂方面的有效性。
{"title":"A novel mixed mode fracture criterion for functionally graded materials considering fracture process zone","authors":"","doi":"10.1016/j.tafmec.2024.104710","DOIUrl":"10.1016/j.tafmec.2024.104710","url":null,"abstract":"<div><div>A new mixed mode I/II fracture criterion based on strain energy release rate theory is proposed for investigating fracture behavior in cracked functionally graded materials. In this study, the crack is assumed to be located along the material gradation and within the brittle side of the material. For the first time in this type of material, the fracture process zone and the energy dissipated in this region are considered to enhance the prediction accuracy of the proposed criterion. The mechanical and fracture properties of the damage zone are characterized using the microcrack density parameter. A novel method for manufacturing functionally graded materials is introduced, offering numerous advantages by controlling the gel time of the resin. The critical mixed mode and pure mode II fracture toughness of the fabricated specimens are determined through three-point and four-point bending tests. A comparison of the experimental data with the fracture limit curve demonstrates the effectiveness of the newly proposed criterion for investigating mixed mode fracture in functionally graded materials.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433992","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.tafmec.2024.104702
In fatigue testing the number of cycles and crack length to failure are recognised to be stochastic quantities necessitating repetitive testing to draw out statistically meaningful measures. The origin of this phenomena is uncertainty in the detailed microstructure, where (from a microstructural perspective) there exists no two identical test pieces. The situation is further compounded under scaled testing of polycrystalline specimens due to a form of coarsening with scaled samples containing less grains than the full-size test piece with samples drawn from the same material stock. Although microstructural uncertainly impedes predictability, implying the need for a probabilistic framework, it is nonetheless important to capture deterministic aspects that feature in any stochastic model. The theory advanced in this paper builds on the finite similitude scaling theory and the two-experiment first-order rule that features length as an invariant. Length invariance is shown to be critically important for fatigue as it caters for the many aspects of the microstructure that are not scaled under scaled testing. A diffusional stochastic model is introduced in the paper that is constrained by the first-order finite similitude rule. The approach is shown to enforce necessary determinism despite the uncertainties present and unlike many of the rules that are currently applied in fatigue analysis, it is applicable over a large range of length scales. Popular growth laws for long cracks are examined under the new framework, which transpires to be remarkably straightforward to apply.
{"title":"The stochastic response of fatigue crack growth in scaled components","authors":"","doi":"10.1016/j.tafmec.2024.104702","DOIUrl":"10.1016/j.tafmec.2024.104702","url":null,"abstract":"<div><div>In fatigue testing the number of cycles and crack length to failure are recognised to be stochastic quantities necessitating repetitive testing to draw out statistically meaningful measures. The origin of this phenomena is uncertainty in the detailed microstructure, where (from a microstructural perspective) there exists no two identical test pieces. The situation is further compounded under scaled testing of polycrystalline specimens due to a form of coarsening with scaled samples containing less grains than the full-size test piece with samples drawn from the same material stock. Although microstructural uncertainly impedes predictability, implying the need for a probabilistic framework, it is nonetheless important to capture deterministic aspects that feature in any stochastic model. The theory advanced in this paper builds on the <em>finite similitude scaling theory</em> and the two-experiment first-order rule that features <em>length</em> as an invariant. Length invariance is shown to be critically important for fatigue as it caters for the many aspects of the microstructure that are not scaled under scaled testing. A diffusional stochastic model is introduced in the paper that is constrained by the first-order finite similitude rule. The approach is shown to enforce necessary determinism despite the uncertainties present and unlike many of the rules that are currently applied in fatigue analysis, it is applicable over a large range of length scales. Popular growth laws for long cracks are examined under the new framework, which transpires to be remarkably straightforward to apply.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419411","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 : 2024-10-09DOI: 10.1016/j.tafmec.2024.104713
The fracture behavior of AA 7050-T6/CFRP adhesive joints was investigated under mode I and II loading. Digital Image Correlation (DIC) provided precise measurements of crack length and crack tip opening/shear displacement (CTOD/CTSD), while the Extended Global Method (EGM) was used to determine the Energy Release Rate (ERR) and resistance curves (R-curves) for each fracture mode. The direct method was applied to establish the traction-separation law (TSL) and bridging law. Based on observed failure mechanisms, a novel cohesive law with five linear components was proposed, with parameters derived from experimentally obtained TSL and bridging law. Experimental determination of cohesive zone lengths for both fracture modes was achieved using the DIC technique, which was then compared with analytical predictions. Finally, the five-linear and trapezoidal cohesive zone model (CZM) was used to simulate the mode I and mode II fracture processes, respectively, within a finite element framework.
研究了 AA 7050-T6/CFRP 粘合剂接头在模式 I 和模式 II 载荷下的断裂行为。数字图像相关（DIC）提供了裂缝长度和裂缝顶端张开/剪切位移（CTOD/CTSD）的精确测量，而扩展全局法（EGM）则用于确定每种断裂模式的能量释放率（ERR）和阻力曲线（R-curves）。直接法用于建立牵引分离定律（TSL）和桥接定律。根据观察到的断裂机制，提出了一种包含五个线性分量的新型内聚律，其参数来自实验获得的牵引分离律和桥接律。利用 DIC 技术对两种断裂模式的内聚区长度进行了实验测定，并与分析预测结果进行了比较。最后，在有限元框架内使用五线性和梯形内聚区模型（CZM）分别模拟了模式 I 和模式 II 的断裂过程。
{"title":"Assessing fracture behavior in Composite-Metal bonded joints under opening and sliding Modes: Insights from Experiments, CZM, and FEA","authors":"","doi":"10.1016/j.tafmec.2024.104713","DOIUrl":"10.1016/j.tafmec.2024.104713","url":null,"abstract":"<div><div>The fracture behavior of AA 7050-T6/CFRP adhesive joints was investigated under mode I and II loading. Digital Image Correlation (DIC) provided precise measurements of crack length and crack tip opening/shear displacement (CTOD/CTSD), while the Extended Global Method (EGM) was used to determine the Energy Release Rate (ERR) and resistance curves (R-curves) for each fracture mode. The direct method was applied to establish the traction-separation law (TSL) and bridging law. Based on observed failure mechanisms, a novel cohesive law with five linear components was proposed, with parameters derived from experimentally obtained TSL and bridging law. Experimental determination of cohesive zone lengths for both fracture modes was achieved using the DIC technique, which was then compared with analytical predictions. Finally, the five-linear and trapezoidal cohesive zone model (CZM) was used to simulate the mode I and mode II fracture processes, respectively, within a finite element framework.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418860","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.tafmec.2024.104711
Asymmetrical single-edge notched beam (ASENB) specimen is among the suitable specimens for measuring full mode I/II fracture parameters. However, in lack of a standard or common method, researchers used this specimen with different geometers, which have proven can affect the results. This research evaluated the effect of ASENB’s geometry on fracture parameters numerically and experimentally. First, the finite element method determined the geometry factors (YI and YII) and non-singular (T-stress) fracture parameters. Then, the experimental fracture tests were conducted using ceramic material. Results show it is more reasonable to express the YI and YII based on S1/L and S2/H, instant S1/L, and S2/L. In other words, the geometry factors can be expressed better based on the height of the specimen and not length. So, for ASENB specimens tested in conventional S1/L of 0.7 to 0.9, the pure mode-II condition was generated in 0.05 < S2/H < 0.14. The modeling showed that the non-singular term of fracture (T-stress) was significant compared to fracture toughness, so the Biaxiality was measured as 0.5 to −2.5, more significant for pure mode-II and almost regardless of the a/H ratio. As experimental tests show, the relative length of the ASENB specimen has an insignificant effect on measured fracture toughness, so a more compact specimen with L/H of about 2 to 4 can suggested for tests.
{"title":"Effect of length-to-height ratio on fracture properties of asymmetrical single-edge notched beam (ASENB) specimen made of ceramic under full range mixed mode I/II loading state","authors":"","doi":"10.1016/j.tafmec.2024.104711","DOIUrl":"10.1016/j.tafmec.2024.104711","url":null,"abstract":"<div><div>Asymmetrical single-edge notched beam (ASENB) specimen is among the suitable specimens for measuring full mode I/II fracture parameters. However, in lack of a standard or common method, researchers used this specimen with different geometers, which have proven can affect the results. This research evaluated the effect of ASENB’s geometry on fracture parameters numerically and experimentally. First, the finite element method determined the geometry factors (<em>Y<sub>I</sub></em> and <em>Y<sub>II</sub></em>) and non-singular (<em>T</em>-stress) fracture parameters. Then, the experimental fracture tests were conducted using ceramic material. Results show it is more reasonable to express the <em>Y<sub>I</sub></em> and <em>Y<sub>II</sub></em> based on <em>S</em><sub>1</sub>/<em>L</em> and <em>S</em><sub>2</sub>/<em>H</em>, instant <em>S</em><sub>1</sub>/<em>L,</em> and <em>S</em><sub>2</sub>/<em>L</em>. In other words, the geometry factors can be expressed better based on the height of the specimen and not length. So, for ASENB specimens tested in conventional <em>S</em><sub>1</sub>/<em>L</em> of 0.7 to 0.9, the pure mode-II condition was generated in 0.05 < <em>S</em><sub>2</sub>/<em>H</em> < 0.14. The modeling showed that the non-singular term of fracture (<em>T</em>-stress) was significant compared to fracture toughness, so the Biaxiality was measured as 0.5 to −2.5, more significant for pure mode-II and almost regardless of the <em>a</em>/<em>H</em> ratio. As experimental tests show, the relative length of the ASENB specimen has an insignificant effect on measured fracture toughness, so a more compact specimen with <em>L</em>/<em>H</em> of about 2 to 4 can suggested for tests.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419410","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 : 2024-10-05DOI: 10.1016/j.tafmec.2024.104708
This paper addresses the determination of the energy release rate in an orthotropic elastic material such as wood with a three-dimensional view of the problem. The mixed mode loading associated with the anisotropy of the material required mode decoupling by isolating the energy release rates in mode I, mode II and in mode III. These energy release rates are calculated using the invariant integral M of Linear Elastic Fracture Mechanics (LEFM). This decoupling has necessitated the introduction of kinetically and statically admissible three-dimensional virtual displacement and stress fields in the vicinity of the crack front. The fracture mode decoupling strategy is presented and implemented through finite element modelling of a Mixed Mode Crack Growth (MMCG) specimen. Different thicknesses are investigated to highlight the 3D effects. The modelling highlighted the effect of Mode II at the edges of free surfaces for mixed loadings including mode III (mode III, mode (II+III) and mode (I+II+III)), while mode III was the predominant at the middle of the specimen. In cases of mixed mode (I+II), the energy release rate GI was highest at the middle of the specimen and lowest at the edges of the free surfaces, regardless of the degree of mixing for a given thickness. The correlation between the results obtained using the proposed approach and the non-dependence of the integration domain, as well as with the usual approaches employed in the literature, is demonstrated.
本文从三维角度探讨了如何确定木材等正交弹性材料的能量释放率。与材料各向异性相关的混合模式加载要求通过隔离模式 I、模式 II 和模式 III 中的能量释放率来进行模式解耦。这些能量释放率是通过线性弹性断裂力学（LEFM）的不变积分 M 计算得出的。这种解耦需要在裂缝前沿附近引入动力学和静力学上可接受的三维虚拟位移和应力场。通过对混合模式裂纹生长（MMCG）试样进行有限元建模，介绍并实施了断裂模式解耦策略。研究了不同厚度的试样，以突出三维效应。建模突出了混合载荷（包括模式 III、模式 (II+III) 和模式 (I+II+III)）下自由表面边缘的模式 II 的影响，而模式 III 在试样中部占主导地位。在混合模式（I+II）情况下，无论给定厚度的混合程度如何，试样中部的能量释放率 GI 最高，自由表面边缘最低。使用所提出的方法获得的结果与积分域的非依赖性以及文献中采用的通常方法之间的相关性得到了证明。
{"title":"Three-dimensional fracture modes decoupling by means of invariant integrals in wood under mixed mode loading","authors":"","doi":"10.1016/j.tafmec.2024.104708","DOIUrl":"10.1016/j.tafmec.2024.104708","url":null,"abstract":"<div><div>This paper addresses the determination of the energy release rate in an orthotropic elastic material such as wood with a three-dimensional view of the problem. The mixed mode loading associated with the anisotropy of the material required mode decoupling by isolating the energy release rates in mode I, mode II and in mode III. These energy release rates are calculated using the invariant integral M of Linear Elastic Fracture Mechanics (LEFM). This decoupling has necessitated the introduction of kinetically and statically admissible three-dimensional virtual displacement and stress fields in the vicinity of the crack front. The fracture mode decoupling strategy is presented and implemented through finite element modelling of a Mixed Mode Crack Growth (MMCG) specimen. Different thicknesses are investigated to highlight the 3D effects. The modelling highlighted the effect of Mode II at the edges of free surfaces for mixed loadings including mode III (mode III, mode (II+III) and mode (I+II+III)), while mode III was the predominant at the middle of the specimen. In cases of mixed mode (I+II), the energy release rate GI was highest at the middle of the specimen and lowest at the edges of the free surfaces, regardless of the degree of mixing for a given thickness. The correlation between the results obtained using the proposed approach and the non-dependence of the integration domain, as well as with the usual approaches employed in the literature, is demonstrated.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418859","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 : 2024-10-04DOI: 10.1016/j.tafmec.2024.104707
The fatigue life of surface layer (FSL) is innovatively characterized to accurately capture the effect of surface integrity on the fatigue behavior of the components. The sensitivity of FSL of 300 M ultrahigh strength steel to the surface integrity indexes induced by representative manufacturing processes was analyzed by analytical modeling and fatigue tests from the perspective of engineering fracture mechanics. The ultrasonic surface rolling process (USRP) was introduced to optimize the fatigue limit of 300 M steel, and the improvement in fatigue life was experimentally quantified. Besides, the fracture analysis was conducted to provide the reason why USRP can enhance the fatigue behavior of 300 M steel. The results show that FSL occupies a majority with percentage of over 95 % in the entire fatigue life and a strong relation with the machined surface defects, especially the surface machining marks. The excellent surface finishing effect and high compressive residual stresses induced by engineered USRP could transfer the crack source from surface machining marks into subsurface inclusions, which greatly prolongs the fatigue crack initiation life and thereby the entire fatigue life. To be specific, the fatigue life was elevated by more than 40 times and the fatigue strength was increased by 34.7 % after USRP for the tested 300 M steel.
表面层疲劳寿命（FSL）是一种创新性的表征，可准确捕捉表面完整性对部件疲劳行为的影响。从工程断裂力学的角度，通过分析建模和疲劳试验，分析了 300 M 超高强度钢的 FSL 对代表性制造工艺引起的表面完整性指标的敏感性。引入超声波表面滚压工艺（USRP）优化了 300 M 钢的疲劳极限，并通过实验量化了疲劳寿命的提高。此外，还进行了断裂分析，以提供 USRP 可改善 300 M 钢疲劳行为的原因。结果表明，FSL 在整个疲劳寿命中占绝大多数，比例超过 95%，且与加工表面缺陷，尤其是表面加工痕迹有很大关系。工程 USRP 卓越的表面精加工效果和诱导的高压缩残余应力可将裂纹源从表面加工痕迹转移到表面下夹杂物中，从而大大延长疲劳裂纹起始寿命，进而延长整个疲劳寿命。具体而言，经过 USRP 处理后，受测 300 M 钢的疲劳寿命提高了 40 多倍，疲劳强度提高了 34.7%。
{"title":"Surface fatigue characterization and its enhancement by the engineered ultrasonic rolling process for 300 M ultrahigh strength steel","authors":"","doi":"10.1016/j.tafmec.2024.104707","DOIUrl":"10.1016/j.tafmec.2024.104707","url":null,"abstract":"<div><div>The fatigue life of surface layer (FSL) is innovatively characterized to accurately capture the effect of surface integrity on the fatigue behavior of the components. The sensitivity of FSL of 300 M ultrahigh strength steel to the surface integrity indexes induced by representative manufacturing processes was analyzed by analytical modeling and fatigue tests from the perspective of engineering fracture mechanics. The ultrasonic surface rolling process (USRP) was introduced to optimize the fatigue limit of 300 M steel, and the improvement in fatigue life was experimentally quantified. Besides, the fracture analysis was conducted to provide the reason why USRP can enhance the fatigue behavior of 300 M steel. The results show that FSL occupies a majority with percentage of over 95 % in the entire fatigue life and a strong relation with the machined surface defects, especially the surface machining marks. The excellent surface finishing effect and high compressive residual stresses induced by engineered USRP could transfer the crack source from surface machining marks into subsurface inclusions, which greatly prolongs the fatigue crack initiation life and thereby the entire fatigue life. To be specific, the fatigue life was elevated by more than 40 times and the fatigue strength was increased by 34.7 % after USRP for the tested 300 M steel.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418857","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 : 2024-10-03DOI: 10.1016/j.tafmec.2024.104696
To improve computational efficiency, in this work, a coupling scheme between a phase field regularized cohesive zone model and a linear elastic model is proposed. According to the crack pattern, the entire solution domain is partitioned into different subregions, the phase field regularized cohesive zone model is applied only in the subregion where the crack appears, the linear elastic model is considered in the remaining region, combining the characteristics and advantages of the two models to improve computational efficiency. Secondly, in the light of the similarity between the phase field model governing equation and the heat transfer equation, the analogous relationships for different coefficients are given, and the coupling model is implemented using an equivalent thermal coupling framework, avoiding post-processing of complex element. Finally, the validity of the presented model is verified by some typical examples. The results indicate that the coupling model can be used to study the complex fracture process under different failure modes. Its load displacement response, energy characteristic and crack pattern are in line with that of the pure phase field regularized cohesive zone model and are in agreement with experiment and literature results. Meanwhile, compared to pure phase field model, the proposed coupling model consumes lower time cost.
{"title":"A simple and efficient solution scheme of coupling method between phase field regularized cohesive zone model and linear elastic model for fracture","authors":"","doi":"10.1016/j.tafmec.2024.104696","DOIUrl":"10.1016/j.tafmec.2024.104696","url":null,"abstract":"<div><div>To improve computational efficiency, in this work, a coupling scheme between a phase field regularized cohesive zone model and a linear elastic model is proposed. According to the crack pattern, the entire solution domain is partitioned into different subregions, the phase field regularized cohesive zone model is applied only in the subregion where the crack appears, the linear elastic model is considered in the remaining region, combining the characteristics and advantages of the two models to improve computational efficiency. Secondly, in the light of the similarity between the phase field model governing equation and the heat transfer equation, the analogous relationships for different coefficients are given, and the coupling model is implemented using an equivalent thermal coupling framework, avoiding post-processing of complex element. Finally, the validity of the presented model is verified by some typical examples. The results indicate that the coupling model can be used to study the complex fracture process under different failure modes. Its load displacement response, energy characteristic and crack pattern are in line with that of the pure phase field regularized cohesive zone model and are in agreement with experiment and literature results. Meanwhile, compared to pure phase field model, the proposed coupling model consumes lower time cost.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418852","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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