Pub Date : 2024-09-21DOI: 10.1016/j.engfracmech.2024.110493
This work describes a probabilistic framework for cleavage fracture of ferritic–pearlitic steels incorporating experimental measurements of microcrack distribution associated with the cracking of the pearlitic microstructure. A central objective of this study is to explore and further extend application of a probabilistic framework incorporating the statistics of microcracks to predict specimen geometry effects on the fracture toughness distribution for a typical ferritic–pearlitic structural steel. Fracture toughness values for an ASTM A572 Grade 50 structural steel derived from fracture tests using conventional SE(B) specimens with varying thickness and -ratios provide the cleavage fracture resistance data needed to assess specimen geometry effects on the probability distribution of -values. The present exploratory study successfully predicts the measured statistical distribution of cleavage fracture toughness in shallow crack specimens and provides further support of the proposed probabilistic model as a more advanced and effective engineering-level procedure in fracture assessment methodologies.
{"title":"A probabilistic model to predict specimen geometry effects on fracture toughness in ferritic–pearlitic steels","authors":"","doi":"10.1016/j.engfracmech.2024.110493","DOIUrl":"10.1016/j.engfracmech.2024.110493","url":null,"abstract":"<div><div>This work describes a probabilistic framework for cleavage fracture of ferritic–pearlitic steels incorporating experimental measurements of microcrack distribution associated with the cracking of the pearlitic microstructure. A central objective of this study is to explore and further extend application of a probabilistic framework incorporating the statistics of microcracks to predict specimen geometry effects on the fracture toughness distribution for a typical ferritic–pearlitic structural steel. Fracture toughness values for an ASTM A572 Grade 50 structural steel derived from fracture tests using conventional SE(B) specimens with varying thickness and <span><math><mrow><mi>a</mi><mo>/</mo><mi>W</mi></mrow></math></span>-ratios provide the cleavage fracture resistance data needed to assess specimen geometry effects on the probability distribution of <span><math><msub><mrow><mi>J</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span>-values. The present exploratory study successfully predicts the measured statistical distribution of cleavage fracture toughness in shallow crack specimens and provides further support of the proposed probabilistic model as a more advanced and effective engineering-level procedure in fracture assessment methodologies.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314966","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 : 2024-09-21DOI: 10.1016/j.engfracmech.2024.110497
This study investigates the fracture behavior of additively manufactured round-tip V-notched diagonally loaded square plate (RV-DLSP) specimens with different notch opening angles and tip radii produced from the Polylactic acid (PLA) with raster orientation using the fused deposition modeling (FDM) technique. PLA is known for its ductile behavior, making it a suitable material for various engineering applications. Also, the layer-wise manufacturing process in FDM technique makes the PLA specimens be actually anisotropic. To take the nonlinearity and anisotropy of PLA simultaneously into consideration in prediction of the fracture loads of RV-DLSP specimens, the present study employs the Virtual Isotropic Material Concept (VIMC) and modified Equivalent Material Concept (MEMC) in a two-level strategy of simplifying PLA to an isotropic linear elastic virtual material. Then, the mean stress (MS) and maximum tangential stress (MTS) criteria are utilized to estimate the fracture loads. The theoretical estimations reveal that the VIMC-MEMC-RV-MS criterion is the most accurate model, demonstrating its effectiveness in predicting the fracture behavior of RV-DLSP specimens. Additionally, the VIMC-MEMC-RV-MTS criterion shows commendable accuracy, particularly for the specimens with 30 (deg.) notch opening angle. The scanning electron microscopy (SEM) analysis of the fracture surfaces provides further insights into the fracture mechanisms of RV-DLSP specimens. Notably, distinct fracture patterns are observed based on variations in the notch geometry. Specimens with smaller notch tip radii exhibit fiber cleavage, while those with larger radii display greater fiber interpenetration. These SEM observations are consistent with the fracture load data, which indicates higher fracture loads with increasing the notch opening angle and tip radius. By integrating VIMC and MEMC with the two fracture criteria, accurate predictions of the notch fracture toughness can be achieved, facilitating the design and optimization of 3D-printed PLA components against fracture.
{"title":"Tensile fracture prediction of 3D-printed V-notched PLA specimens: Application of VIMC-MEMC in conjunction with brittle fracture criteria","authors":"","doi":"10.1016/j.engfracmech.2024.110497","DOIUrl":"10.1016/j.engfracmech.2024.110497","url":null,"abstract":"<div><div>This study investigates the fracture behavior of additively manufactured round-tip V-notched diagonally loaded square plate (RV-DLSP) specimens with different notch opening angles and tip radii produced from the Polylactic acid (PLA) with <span><math><msub><mrow><mo>[</mo><mn>0</mn><mo>/</mo><mn>90</mn><mo>/</mo><mn>45</mn><mo>/</mo><mo>-</mo><mn>45</mn><mo>]</mo></mrow><mi>s</mi></msub></math></span> raster orientation using the fused deposition modeling (FDM) technique. PLA is known for its ductile behavior, making it a suitable material for various engineering applications. Also, the layer-wise manufacturing process in FDM technique makes the PLA specimens be actually anisotropic. To take the nonlinearity and anisotropy of PLA simultaneously into consideration in prediction of the fracture loads of RV-DLSP specimens, the present study employs the Virtual Isotropic Material Concept (VIMC) and modified Equivalent Material Concept (MEMC) in a two-level strategy of simplifying PLA to an isotropic linear elastic virtual material. Then, the mean stress (MS) and maximum tangential stress (MTS) criteria are utilized to estimate the fracture loads. The theoretical estimations reveal that the VIMC-MEMC-RV-MS criterion is the most accurate model, demonstrating its effectiveness in predicting the fracture behavior of RV-DLSP specimens. Additionally, the VIMC-MEMC-RV-MTS criterion shows commendable accuracy, particularly for the specimens with 30 (deg.) notch opening angle. The scanning electron microscopy (SEM) analysis of the fracture surfaces provides further insights into the fracture mechanisms of RV-DLSP specimens. Notably, distinct fracture patterns are observed based on variations in the notch geometry. Specimens with smaller notch tip radii exhibit fiber cleavage, while those with larger radii display greater fiber interpenetration. These SEM observations are consistent with the fracture load data, which indicates higher fracture loads with increasing the notch opening angle and tip radius. By integrating VIMC and MEMC with the two fracture criteria, accurate predictions of the notch fracture toughness can be achieved, facilitating the design and optimization of 3D-printed PLA components against fracture.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314963","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 : 2024-09-21DOI: 10.1016/j.engfracmech.2024.110515
In this study, the researchers have developed a Multiphysics-Lattice Discrete Particle Model (M-LDPM) framework that deals with coupled-fracture-poroflow problems. The M-LDPM framework uses two lattice systems, the LDPM tessellation and the Flow Lattice Element (FLE) network, to represent the heterogeneous internal structure of typical quasi-brittle materials like concrete and rocks, and to simulate the material’s mechanical and transport behavior at the aggregate scale. The researchers revisited the LDPM governing equations and added the influence of fluid pore pressure. They also derived the Flow Lattice Model (FLM) governing equations for pore pressure flow through mass conservation balances for uncracked and cracked volumes. The M-LDPM framework was implemented using Abaqus user element subroutine VUEL for the explicit dynamic procedure of LDPM and user subroutine UEL for the implicit transient procedure of FLM. The coupling of the two models was achieved using Interprocess Communication (IPC) between Abaqus solvers. The M-LDPM framework can simulate the variation of permeability induced by fracturing processes by relating the transport properties of flow elements with local cracking behaviors. The researchers validated the M-LDPM framework by comparing the numerical simulation outcomes with analytical solutions of classical benchmarks in poromechanics.
{"title":"An interprocess communication-based two-way coupling approach for implicit–explicit multiphysics lattice discrete particle model simulations","authors":"","doi":"10.1016/j.engfracmech.2024.110515","DOIUrl":"10.1016/j.engfracmech.2024.110515","url":null,"abstract":"<div><div>In this study, the researchers have developed a Multiphysics-Lattice Discrete Particle Model (M-LDPM) framework that deals with coupled-fracture-poroflow problems. The M-LDPM framework uses two lattice systems, the LDPM tessellation and the Flow Lattice Element (FLE) network, to represent the heterogeneous internal structure of typical quasi-brittle materials like concrete and rocks, and to simulate the material’s mechanical and transport behavior at the aggregate scale. The researchers revisited the LDPM governing equations and added the influence of fluid pore pressure. They also derived the Flow Lattice Model (FLM) governing equations for pore pressure flow through mass conservation balances for uncracked and cracked volumes. The M-LDPM framework was implemented using Abaqus user element subroutine VUEL for the explicit dynamic procedure of LDPM and user subroutine UEL for the implicit transient procedure of FLM. The coupling of the two models was achieved using Interprocess Communication (IPC) between Abaqus solvers. The M-LDPM framework can simulate the variation of permeability induced by fracturing processes by relating the transport properties of flow elements with local cracking behaviors. The researchers validated the M-LDPM framework by comparing the numerical simulation outcomes with analytical solutions of classical benchmarks in poromechanics.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142322616","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 : 2024-09-21DOI: 10.1016/j.engfracmech.2024.110519
To simulate structural crack propagation and predict fatigue life, the extended finite element method (XFEM) combined with the virtual crack closure technique (VCCT) is adopted in this paper. Firstly, the underlying principles of the XFEM-VCCT framework are elaborated comprehensively, mainly including the calculation of crack tip energy release rate based on VCCT, the simulation of element cracking utilizing the phantom nodes, and the computation of structural responses under cyclic loading through the direct cyclic analysis. In addition, to calculate the crack propagation length, an interpolation method to obtain the crack tip coordinates is developed based on tracking and locating the crack by the level set functions. Meanwhile, to compensate the defect that the fatigue life is often overestimated when dealing with the complex mode crack in complex structure through XFEM-VCCT, a simple improved algorithm based on the average rate concept is proposed without altering the XFEM-VCCT framework. Based on specific examples, the necessity and accuracy of the improved algorithm are fully verified by comparing with the original method, and the fatigue life predicted by the improved algorithm is more consistent with reality. Finally, this method is successfully applied to the simulation and analyses for a typical ship stiffened plate structure, demonstrating good engineering applicability.
{"title":"Structural fatigue crack propagation simulation and life prediction based on improved XFEM-VCCT","authors":"","doi":"10.1016/j.engfracmech.2024.110519","DOIUrl":"10.1016/j.engfracmech.2024.110519","url":null,"abstract":"<div><div>To simulate structural crack propagation and predict fatigue life, the extended finite element method (XFEM) combined with the virtual crack closure technique (VCCT) is adopted in this paper. Firstly, the underlying principles of the XFEM-VCCT framework are elaborated comprehensively, mainly including the calculation of crack tip energy release rate based on VCCT, the simulation of element cracking utilizing the phantom nodes, and the computation of structural responses under cyclic loading through the direct cyclic analysis. In addition, to calculate the crack propagation length, an interpolation method to obtain the crack tip coordinates is developed based on tracking and locating the crack by the level set functions. Meanwhile, to compensate the defect that the fatigue life is often overestimated when dealing with the complex mode crack in complex structure through XFEM-VCCT, a simple improved algorithm based on the average rate concept is proposed without altering the XFEM-VCCT framework. Based on specific examples, the necessity and accuracy of the improved algorithm are fully verified by comparing with the original method, and the fatigue life predicted by the improved algorithm is more consistent with reality. Finally, this method is successfully applied to the simulation and analyses for a typical ship stiffened plate structure, demonstrating good engineering applicability.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142310254","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 : 2024-09-21DOI: 10.1016/j.engfracmech.2024.110508
Developing fracture-resistant high-strength steels is an attractive prospect for various structural applications. In this work, a combination of carburizing heat treatment (CHT) and shot peening (SP) was used to develop combined strengthening (CS) mechanisms and to improve the mechanical strength and dynamic fracture toughness of 18CrNiMo7-6 alloy steel. Standard tensile tests and split Hopkinson pressure bar tests were conducted to investigate the strength and dynamic fracture toughness of the 18CrNiMo7-6 alloy steel. The crack initiation and propagation of samples were studied using scanning electron microscopy and transmission electron microscopy. Microstructure characterization and molecular dynamic simulations indicated that the excellent dynamic fracture toughness of the CS samples could be attributed to the grain refinement after strengthening and the formation of numerous slip bands at the crack tips, reducing the stress concentration at the crack tips. The Cr23C6 precipitates have a positive effect on the strength improvement of 18CrNiMo7-6 alloy steel. The results showed that this research can be used to guide the design of steels with high-strength and high-dynamic fracture toughness.
{"title":"Dynamic fracture toughness and crack propagation mechanism of a heterogeneous heterostructured material under combined strengthening mechanisms","authors":"","doi":"10.1016/j.engfracmech.2024.110508","DOIUrl":"10.1016/j.engfracmech.2024.110508","url":null,"abstract":"<div><div>Developing fracture-resistant high-strength steels is an attractive prospect for various structural applications. In this work, a combination of carburizing heat treatment (CHT) and shot peening (SP) was used to develop combined strengthening (CS) mechanisms and to improve the mechanical strength and dynamic fracture toughness of 18CrNiMo7-6 alloy steel. Standard tensile tests and split Hopkinson pressure bar tests were conducted to investigate the strength and dynamic fracture toughness of the 18CrNiMo7-6 alloy steel. The crack initiation and propagation of samples were studied using scanning electron microscopy and transmission electron microscopy. Microstructure characterization and molecular dynamic simulations indicated that the excellent dynamic fracture toughness of the CS samples could be attributed to the grain refinement after strengthening and the formation of numerous slip bands at the crack tips, reducing the stress concentration at the crack tips. The Cr<sub>23</sub>C<sub>6</sub> precipitates have a positive effect on the strength improvement of 18CrNiMo7-6 alloy steel. The results showed that this research can be used to guide the design of steels with high-strength and high-dynamic fracture toughness.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314967","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 : 2024-09-21DOI: 10.1016/j.engfracmech.2024.110517
The effective macroscopic properties of composites are determined by the intricate interactions among the individual components within their microstructure. Preserving these microscopic details during the failure simulation of macrostructures presents significant challenges. This work proposes a multiscale modeling framework to numerically predict the macroscopic fracture properties of unidirectional fiber-reinforced composites based on micromechanical analysis. In this study, 2D representative volume elements (RVEs) combined with the phase-field method are utilized to simulate fiber-reinforced composites under transverse loadings. A series of representative loading conditions are employed to investigate cracking patterns and to construct failure strength envelopes of the composites subjected to different multiaxial proportional loadings. By extracting the softening curve from the uniaxial tensile simulation of the RVE and fitting it with a tenth-order polynomial, the homogenized cohesive law, combined with the phase-field method, is applied to the damage analysis of macroscopic heterogeneous materials. The homogenized model of unidirectional fiber reinforced composites is numerically validated through simulations of a 2D flat plate. The simulation results demonstrate the excellent potential of the proposed multiscale modeling framework to accurately and efficiently predict the progressive failure and fracture behavior of fiber-reinforced composites in engineering applications.
{"title":"A multiscale modeling for progressive failure behavior of unidirectional fiber-reinforced composites based on phase-field method","authors":"","doi":"10.1016/j.engfracmech.2024.110517","DOIUrl":"10.1016/j.engfracmech.2024.110517","url":null,"abstract":"<div><div>The effective macroscopic properties of composites are determined by the intricate interactions among the individual components within their microstructure. Preserving these microscopic details during the failure simulation of macrostructures presents significant challenges. This work proposes a multiscale modeling framework to numerically predict the macroscopic fracture properties of unidirectional fiber-reinforced composites based on micromechanical analysis. In this study, 2D representative volume elements (RVEs) combined with the phase-field method are utilized to simulate fiber-reinforced composites under transverse loadings. A series of representative loading conditions are employed to investigate cracking patterns and to construct failure strength envelopes of the composites subjected to different multiaxial proportional loadings. By extracting the softening curve from the uniaxial tensile simulation of the RVE and fitting it with a tenth-order polynomial, the homogenized cohesive law, combined with the phase-field method, is applied to the damage analysis of macroscopic heterogeneous materials. The homogenized model of unidirectional fiber reinforced composites is numerically validated through simulations of a 2D flat plate. The simulation results demonstrate the excellent potential of the proposed multiscale modeling framework to accurately and efficiently predict the progressive failure and fracture behavior of fiber-reinforced composites in engineering applications.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142322617","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 : 2024-09-21DOI: 10.1016/j.engfracmech.2024.110510
The dominant failure mode was characterized as debonding in the novel non-welded wrapped composite joint made with GFRP composites wrapped around steel sections. Glass fiber composite-steel three-point end notched flexure (3ENF) and four-point end notched flexure (4ENF) specimens were utilized to experimentally investigate mode II fracture behavior of this composite-steel bonded interface. Two new methods were proposed with the help of digital image correlation (DIC) technique to quantify fracture data during the tests: 1) the “shear strain scaling method” to quantify the crack length a; 2) the asymptotic analysis method based on the longitudinal displacement distribution along the height of the specimen at the pre-crack tip to quantify the crack tip opening displacement (CTOD). To numerically simulate the mode II fracture behavior, a four-linear traction-separation law was proposed in the cohesive zone modeling (CZM) where the softening behavior with a plateau was defined by the authors between traditionally considered initiation and fiber bridging behavior. The experimental and numerical approaches were validated mutually through good matches between the test and FEA results. 3ENF test provided good insight into softening behavior while 4ENF contributed to quantification of fiber bridging. These findings contribute to a more comprehensive characterization and understanding of the ductile fracture behavior of bi-material bonded joints, especially in mode II failure scenarios.
用玻璃纤维增强复合材料包裹钢截面制成的新型非焊接包裹复合材料接头的主要失效模式为脱粘。利用玻璃纤维复合材料-钢三点末端缺口挠曲（3ENF）和四点末端缺口挠曲（4ENF）试样对这种复合材料-钢粘接界面的模式 II 断裂行为进行了实验研究。在数字图像相关（DIC）技术的帮助下，提出了两种新方法来量化试验过程中的断裂数据：1) 用 "剪切应变缩放法 "量化裂纹长度 a；2) 用基于裂纹前端试样高度的纵向位移分布的渐近分析法量化裂纹尖端张开位移 (CTOD)。为了对模式 II 断裂行为进行数值模拟，作者在内聚区建模（CZM）中提出了四线性牵引分离定律，并在传统的起始行为和纤维桥接行为之间定义了具有高原的软化行为。通过试验和有限元分析结果之间的良好匹配，实验和数值方法得到了相互验证。3ENF 试验很好地揭示了软化行为，而 4ENF 则有助于量化纤维架桥。这些发现有助于更全面地描述和理解双材料粘接接头的韧性断裂行为，尤其是在模式 II 失效情况下。
{"title":"Mode II fracture behavior of glass fiber composite-steel bonded interface–experiments and CZM","authors":"","doi":"10.1016/j.engfracmech.2024.110510","DOIUrl":"10.1016/j.engfracmech.2024.110510","url":null,"abstract":"<div><div>The dominant failure mode was characterized as debonding in the novel non-welded wrapped composite joint made with GFRP composites wrapped around steel sections. Glass fiber composite-steel three-point end notched flexure (3ENF) and four-point end notched flexure (4ENF) specimens were utilized to experimentally investigate mode II fracture behavior of this composite-steel bonded interface. Two new methods were proposed with the help of digital image correlation (DIC) technique to quantify fracture data during the tests: 1) the “shear strain scaling method” to quantify the crack length <em>a</em>; 2) the asymptotic analysis method based on the longitudinal displacement distribution along the height of the specimen at the pre-crack tip to quantify the crack tip opening displacement (CTOD). To numerically simulate the mode II fracture behavior, a four-linear traction-separation law was proposed in the cohesive zone modeling (CZM) where the softening behavior with a plateau was defined by the authors between traditionally considered initiation and fiber bridging behavior. The experimental and numerical approaches were validated mutually through good matches between the test and FEA results. 3ENF test provided good insight into softening behavior while 4ENF contributed to quantification of fiber bridging. These findings contribute to a more comprehensive characterization and understanding of the ductile fracture behavior of bi-material bonded joints, especially in mode II failure scenarios.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0013794424006738/pdfft?md5=0ce5a0fec68ab83fe6fd12e2ef2c1995&pid=1-s2.0-S0013794424006738-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142310252","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 : 2024-09-21DOI: 10.1016/j.engfracmech.2024.110518
Discontinuous bonding is a common adhesion state in multilayer structures within the shipbuilding, automotive, and semiconductor industries, as well as in biological adhesion. Based on the cohesive theory and the Euler-Bernoulli beam model, we investigate the peeling behavior of a film from the rigid substrate subjected to periodic and discontinuous bonding. Different from the continuous bonding model, the peeling force during the peeling process exhibits repeated fluctuations. The increase and decrease of peeling force correspond respectively to the initiation of cohesive zones within the non-bonded and bonded segments. Furthermore, the bonding state at the crack tip influences the change pace of the energy release rate. Specifically, when the cohesive zone initiates within a bonded segment, the decrease in the energy release rate accelerates noticeably as the crack tip enters a non-bonded segment. Additionally, the influence of diverse bonding ratios and varying periodic lengths is discussed. This paper provides insights into the peeling behavior under discontinuous bonding effects in nature, and offers potential applications for the optimization and design of multilayer structures.
{"title":"The peeling behavior of film/substrate systems with periodic and discontinuous bonding","authors":"","doi":"10.1016/j.engfracmech.2024.110518","DOIUrl":"10.1016/j.engfracmech.2024.110518","url":null,"abstract":"<div><div>Discontinuous bonding is a common adhesion state in multilayer structures within the shipbuilding, automotive, and semiconductor industries, as well as in biological adhesion. Based on the cohesive theory and the Euler-Bernoulli beam model, we investigate the peeling behavior of a film from the rigid substrate subjected to periodic and discontinuous bonding. Different from the continuous bonding model, the peeling force during the peeling process exhibits repeated fluctuations. The increase and decrease of peeling force correspond respectively to the initiation of cohesive zones within the non-bonded and bonded segments. Furthermore, the bonding state at the crack tip influences the change pace of the energy release rate. Specifically, when the cohesive zone initiates within a bonded segment, the decrease in the energy release rate accelerates noticeably as the crack tip enters a non-bonded segment. Additionally, the influence of diverse bonding ratios and varying periodic lengths is discussed. This paper provides insights into the peeling behavior under discontinuous bonding effects in nature, and offers potential applications for the optimization and design of multilayer structures.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142322614","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 : 2024-09-21DOI: 10.1016/j.engfracmech.2024.110506
Film cooling holes are the main cooling structures in nickel-based single-crystal cooling turbine blades. To evaluate the low-cycle fatigue life of irregular gas film holes, nine types of Ni-based single-crystal flat-plate test pieces with irregular film cooling holes of different shapes were designed in this study. Fatigue tests were performed at high temperature (850 ℃) and the multiscale fracture mechanisms of the samples analyzed in detail. The stress–strain field around the irregular film cooling holes was analyzed based on crystal plasticity theory using the finite element method. Three life prediction models based on the Coffin–Manson–Basquin formula, maximum principal strain, and crystal plasticity theory were proposed to predict the fatigue life of irregular film-cooled pore structures. The predicted results are all within the double-error band.
{"title":"Fatigue fracture mechanism and life assessment for irregular film cooling hole structures in Ni-based single crystal turbine blades","authors":"","doi":"10.1016/j.engfracmech.2024.110506","DOIUrl":"10.1016/j.engfracmech.2024.110506","url":null,"abstract":"<div><div>Film cooling holes are the main cooling structures in nickel-based single-crystal cooling turbine blades. To evaluate the low-cycle fatigue life of irregular gas film holes, nine types of Ni-based single-crystal flat-plate test pieces with irregular film cooling holes of different shapes were designed in this study. Fatigue tests were performed at high temperature (850 ℃) and the multiscale fracture mechanisms of the samples analyzed in detail. The stress–strain field around the irregular film cooling holes was analyzed based on crystal plasticity theory using the finite element method. Three life prediction models based on the Coffin–Manson–Basquin formula, maximum principal strain, and crystal plasticity theory were proposed to predict the fatigue life of irregular film-cooled pore structures. The predicted results are all within the double-error band.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142322613","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 : 2024-09-21DOI: 10.1016/j.engfracmech.2024.110500
Fatigue crack growth properties of materials are crucial for evaluating damage tolerance in additive manufacturing (AM) metallic structures. However, the unique microstructures and defects of AM materials result in highly complex fatigue crack growth behaviors. Currently, there is a lack of systematic fatigue crack growth rate measurement methods specifically targeting this characteristic. Therefore, taking directed energy deposited Ti-6Al-4V titanium alloy as the object of the study, fatigue crack growth tests were conducted in three orthogonal build orientations of the material using marker load method. Additionally, the visual measurement and compliance methods were also employed to measure fatigue crack growth rates, and the anisotropy of fatigue crack growth property was analyzed. Subsequently, anisotropic fatigue crack growth behaviors were characterized by optical microscope, scanning electron microscope, confocal microscope, and electron backscatter diffraction, suggesting that the microstructure is the primary factor affecting overall fatigue crack growth. Furthermore, nanoindentation tests were conducted to obtain the micromechanical properties within and among columnar grains in different build orientations, clarifying the homogeneity and anisotropy of mechanical properties. Finally, a fatigue crack growth rate measurement method based on marker load method was established, and the advantages of this method in AM materials and structures were summarized by comparing the results with those obtained using these two mature methods.
材料的疲劳裂纹生长特性对于评估增材制造（AM）金属结构的损伤容限至关重要。然而，AM 材料独特的微观结构和缺陷导致了高度复杂的疲劳裂纹生长行为。目前，还缺乏专门针对这一特性的系统疲劳裂纹生长率测量方法。因此，以定向能沉积 Ti-6Al-4V 钛合金为研究对象，采用标记载荷法在材料的三个正交构建方向上进行了疲劳裂纹生长测试。此外，还采用目测法和顺应性法测量了疲劳裂纹生长率，并分析了疲劳裂纹生长特性的各向异性。随后，通过光学显微镜、扫描电子显微镜、共聚焦显微镜和电子反向散射衍射对各向异性的疲劳裂纹生长行为进行了表征，表明微观结构是影响整体疲劳裂纹生长的主要因素。此外，还进行了纳米压痕测试，以获得不同构建方向的柱状晶粒内部和之间的微观力学性能，从而明确力学性能的均匀性和各向异性。最后，建立了基于标记载荷法的疲劳裂纹生长率测量方法，并通过与这两种成熟方法的结果对比，总结了该方法在 AM 材料和结构中的优势。
{"title":"Characterization of fatigue crack growth in directed energy deposited Ti-6Al-4V by marker load method","authors":"","doi":"10.1016/j.engfracmech.2024.110500","DOIUrl":"10.1016/j.engfracmech.2024.110500","url":null,"abstract":"<div><div>Fatigue crack growth properties of materials are crucial for evaluating damage tolerance in additive manufacturing (AM) metallic structures. However, the unique microstructures and defects of AM materials result in highly complex fatigue crack growth behaviors. Currently, there is a lack of systematic fatigue crack growth rate measurement methods specifically targeting this characteristic. Therefore, taking directed energy deposited Ti-6Al-4V titanium alloy as the object of the study, fatigue crack growth tests were conducted in three orthogonal build orientations of the material using marker load method. Additionally, the visual measurement and compliance methods were also employed to measure fatigue crack growth rates, and the anisotropy of fatigue crack growth property was analyzed. Subsequently, anisotropic fatigue crack growth behaviors were characterized by optical microscope, scanning electron microscope, confocal microscope, and electron backscatter diffraction, suggesting that the microstructure is the primary factor affecting overall fatigue crack growth. Furthermore, nanoindentation tests were conducted to obtain the micromechanical properties within and among columnar grains in different build orientations, clarifying the homogeneity and anisotropy of mechanical properties. Finally, a fatigue crack growth rate measurement method based on marker load method was established, and the advantages of this method in AM materials and structures were summarized by comparing the results with those obtained using these two mature methods.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142310255","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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