Engineering Fracture Mechanics最新文献

{"title":"Investigating rock particle breakage using 3D coupled peridynamics-discrete element method: Emphasis on local surface features","authors":"","doi":"10.1016/j.engfracmech.2024.110585","DOIUrl":"10.1016/j.engfracmech.2024.110585","url":null,"abstract":"<div><div>Individual particle breakage within rock-based granular medium profoundly influences the overall macro-scale behavior of the assembly, with the strength being notably impacted by particle morphology and surficial features. However, the widely used numerical methods often oversimplify the realistic morphology, resulting in unrealistic particle breakage simulations. The current study addresses the limitation by specifically investigating the influence of local surface geometry on particle strength and breakage patterns. X-ray Computed Tomography (CT) images of particles were used to obtain the realistic geometry and Voronoi Parallel Linear Enumeration (VPLE), a morphology-preserving surface generation strategy was introduced to capture the complex surficial features. A coupled peridynamics-discrete element framework was proposed to simulate the breakage of individual rock based aggregates. The numerical framework was validated with Brazilian tests on basalt rock cores, and a rigorous comparison was made against other finite-discrete element methods. The study explores different extremes of particle morphology, considering the presence and absence of concavities in the breakage simulations. Robust computational geometry pipeline was employed to measure contact area and local radius of curvature during the breakage. The findings highlight that the concave features, along with the contact curvature significantly reduce the particle strength (<span><math><mrow><mo>≈</mo><mn>40</mn><mtext>%</mtext></mrow></math></span>) as opposed to the convex particle variants exhibiting higher strength. The presence of sharp surficial features led to multiple failure mechanisms, including initial asperity crushing and subsequent splitting failure. The present work strongly emphasizes the importance of considering realistic particle geometry in numerical simulations of granular materials undergoing crushing.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593658","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}

{"title":"Fatigue analysis of novel hole hemmed joints for hybrid busbars in electric vehicle batteries","authors":"","doi":"10.1016/j.engfracmech.2024.110590","DOIUrl":"10.1016/j.engfracmech.2024.110590","url":null,"abstract":"<div><div>This study investigates the fatigue behavior and failure modes of novel hole-hemmed joints, assessing their suitability as hybrid aluminum-copper busbars for electric vehicle batteries. The hole-hemmed joining process, which avoids the need for additional elements, heat, or welding, presents a sustainable solution for hybrid busbar manufacturing. The joints undergo quasi-static shear tests to determine failure mechanisms, strength, and failure displacements. A finite element model of the hole-hemmed process and shear test is developed to evaluate the impact of mechanical interlock on joint performance and to predict regions prone to crack initiation during fatigue testing. Shear fatigue tests and quasi-static shear post-fatigue tests reveal two primary failure modes: cracking at the edge of the aluminum outer sheet branch and bending of the copper inner sheet. The study also examines stiffness degradation and damage evolution during fatigue tests. A normalized load-cycle curve, plotting normalized fatigue load against fatigue life, is created to better predict joint fatigue life. Through comprehensive testing and modeling, the research provides a deep understanding of the mechanical performance of these novel hole-hemmed joints, underscoring their potential for use in hybrid busbars.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572934","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}

{"title":"Experimental study on the Mode l fracture toughness of frozen silty clay incorporating Digital image correlation","authors":"","doi":"10.1016/j.engfracmech.2024.110597","DOIUrl":"10.1016/j.engfracmech.2024.110597","url":null,"abstract":"<div><div>To investigate the effects of initial moisture content and temperature on the Mode I fracture toughness (<em>K</em>_Ic) of frozen silty clay, a series of three-point bending tests were conducted. Rectangular specimens with prefabricated cracks were tested, and digital image correlation (DIC) technology was employed to analyze the microscopic characteristics at the crack tip. The results indicate that the Mode I fracture toughness of frozen silty clay increases with decreasing temperature and increasing initial moisture content. Temperature governs the failure mode, with plastic failure predominantly occurring at high temperatures and brittle failure at low temperatures. Based on the load–displacement curves and DIC recordings, the macroscopic fracture process of the specimens can be categorized into three stages: elastic deformation, formation of the failure surface, and specimen failure. Additionally, the crack propagation process can be further divided into three stages: initiation and development of microcracks, transition from microcracks to macroscopic cracks, and rapid development of macroscopic cracks. These findings provide critical insights for slope stability research in cold regions and offer new perspectives for engineering design and construction in similar environments.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529420","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}

{"title":"Investigation on fatigue performance and microstructure of split sleeve cold expansion of TC4 holes","authors":"","doi":"10.1016/j.engfracmech.2024.110587","DOIUrl":"10.1016/j.engfracmech.2024.110587","url":null,"abstract":"<div><div>The exceptional performance of pivotal structural components serves to enhance the aircraft’s efficient and secure operational profile. The structural components are connected and assembled primarily through fastener holes. However, discontinuities in structural components can lead to stress concentrations around holes, resulting in fatigue failure of the structural components. This is significant in enhancing the fatigue performance of the hole structure. In this study, TC4 titanium alloy was strengthened by split sleeve cold expansion (SCE) technique and its effect on residual stress, microstructure and fatigue fracture was investigated. The results indicate that SCE induces residual compressive stress at the hole edges, thereby inhibiting fatigue crack propagation. Geometrically necessary dislocations are formed at the interface between the α phase and β phase to accommodate the strain gradient. Low angle grain boundaries (LAGBs) impede dislocation movement and accumulate dislocation density, leading to an increase in LAGB misorientation and subsequent transition to high angle grain boundaries. The SCE process led to the formation of subgrain boundaries and refined the grains in the material. The fatigue life of the material was extended by 6.2 times, with peak compressive residual stresses up to 244 MPa at the inlet side. The combined effects of residual compressive stresses, back stress and grain refinement contribute to improving the fatigue life of the hole structure.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529419","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}

{"title":"Excavation-induced cracking of clastic rock: A true triaxial instantaneous unloading study with varied levels of initial damage","authors":"","doi":"10.1016/j.engfracmech.2024.110595","DOIUrl":"10.1016/j.engfracmech.2024.110595","url":null,"abstract":"<div><div>The cracking and squeezing problem in deep engineering significantly constrains project construction. To reveal the cracking mechanism of rock under instantaneous unloading, a self-designed rigid true triaxial experimental apparatus, equipped with groundbreaking electromagnetic unloading and high-speed camera functions, was utilized to conduct instantaneous unloading tests on clastic rock with varied levels of initial damage. The results indicate that samples undergo severe and irreversible lateral dilation during instantaneous unloading, with dilational strain rapidly increasing at higher initial damage levels. Instantaneous unloading induces the generation of numerous tensile microcracks, which propagate and coalesce rapidly. The crack propagation speed, as well as the length and width of the cracks at failure, increase with the rise of the initial damage level. The samples eventually exhibit two distinct macroscopic fracture zones: a tensile fracture zone and a tensile-shear mixed fracture zone. Analysis of acoustic emission hits and energy indicates that higher initial damage levels correspond to greater unloading damage, with a higher overall proportion of tensile cracks throughout the experiment. Under the induction of blasting excavation, radial stress is rapidly unloaded, and dense tensile cracks emerge in the immediate surrounding rock, leading to cracking and squeezing towards the free face. Importantly, higher initial damage levels intensify the squeezing effect. The self-developed equipment serves as a crucial technical tool for researching excavation unloading, and the insights derived from this study provide valuable guidance for understanding cracking mechanisms and informing the construction of deep engineering projects.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553412","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}

{"title":"Development of Johnson-Cook-Distinct Lattice Spring Model and its application in projectile penetration into metal targets","authors":"","doi":"10.1016/j.engfracmech.2024.110571","DOIUrl":"10.1016/j.engfracmech.2024.110571","url":null,"abstract":"<div><div>Projectile penetration into metal targets plays an important role in modern protective structure engineering, damage assessmentin terrorist attacks, and car clash accident analysis, etc. The penetration process of metal target has been characterized by large deformation, high temperature, high pressure, and dynamic damage, which can be classified as a continuous-discontinuous dynamical process. To capture the dynamic responses of metal materials subjected to high-speed penetration, Johnson-Cook model has been implemented in a continuum-discrete model, namely, Distinct Lattice Spring Model (DLSM). This is achieved by redefining the constitutive model in DLSM, with plasticity hardening (plastic strain effects), strain rate, temperature, damage evolution, equation of state, etc., being taken into account, thus developing a new numerical model called JC-DLSM model. This model is validated through studying Taylor rod high-speed impact experiments, thin metal plate penetration experiments, and projectile impact experiments on titanium alloy targets. Good agreement between numerical modelling and experimental data has been achieved for all cases considered, thereby demonstrating the capability of JC-DLSM to reproduce the damage characteristics and ballistic limits of metals under high-speed impact/penetration. Then, the impacts of projectile shape, metal target surface configuration on the characteristics of penetration damage patterns have been investigated. This contributes to a better understanding of the damage mechanisms of metal targets upon penetration or impact, facilitating the computational means for analysing and optimizing the penetration resistance of protective engineering structures.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142561408","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}

{"title":"Effect of isotropy and anisotropy: toward understanding the fracture behavior of magnetoactive elastomers","authors":"","doi":"10.1016/j.engfracmech.2024.110553","DOIUrl":"10.1016/j.engfracmech.2024.110553","url":null,"abstract":"<div><div>Magnetoactive elastomers (MAEs) exhibit magneto-mechanical coupling and typically contain micron-sized spherical ferromagnetic particles embedded in an elastomeric matrix. Anisotropic particle arrangement in MAEs, achieved by curing the material in a magnetic field, offers tailored and enhanced magneto-mechanical coupling compared to isotropic configurations. While tunable MAE properties such as the effective modulus and vibrational response have been relatively well studied, a thorough understanding of their fracture mechanisms, particularly in MAEs with microstructural anisotropy or composites with similar structures remains almost completely unexplored. Here, we characterize the fracture mechanisms of anisotropic and isotropic unmagnetized MAEs using experiments and simulations, focusing on the effects of spherical particles in anisotropic chain-like configurations. Specifically, we experimentally measure the fracture toughness of MAEs containing different volume fractions of particles, and with particles arranged both randomly and aligned at 0°, 45°, and 90° to the loading direction. Results show that anisotropic MAEs with particle chains aligned with the load direction can improve fracture toughness by up to almost 600%, whereas isotropic MAEs increase the fracture toughness by only 420%, compared to the pure elastomer. Scanning electron microscopy of the post-fractured surface reveals toughening mechanisms at micro-scale, such as chain waviness, particle agglomeration, and particle distribution. Simulations using a finite element method-based decoupled phase field-cohesive zone model on simplified geometries qualitatively support imaging interpretations. Overall, this work explains how internal geometry, including waviness in particle chains, chain alignment, and particle agglomerations affects fracture of MAEs and generally soft composites with chain-like geometries of spherical particles. These results have engineering applications in improving fracture properties of smart soft composites relevant to soft robotics, tunable vibration absorbers, and noise attenuators.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572937","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}

{"title":"Impact of elevated loading rates on the shape of the Master Curve (ASTM E1921) for a German RPV steel","authors":"","doi":"10.1016/j.engfracmech.2024.110588","DOIUrl":"10.1016/j.engfracmech.2024.110588","url":null,"abstract":"<div><div>The Master Curve Methodology (ASTM E1921) experimentally assesses a materials temperature-dependent fracture toughness, predominantly for quasi-static testing conditions. The treatment of elevated loading rates is described by the annex A1 of ASTM E1921 and A14 of ASTM E1820. This paper presents results of the evaluation of a large and standard-conforming database in order to verify the procedures recommended by the standard for elevated loading rates. Testing involved C(T)- and SEN(B)-specimens of the RPV-steel 22NiMoCr3-7 (A508 Grade 2) for loading rates of 10⁰ MPa√m/s ≤ <span><math><mrow><mover><mi>K</mi><mo>̇</mo></mover></mrow></math></span> ≤ 10⁴ MPa√m/s in the ductile to brittle transition region. While valid T₀-values were found, single-temperature T₀-values were observed to differ more than expected from multi-temperature T₀-values, which cannot be explained by the Master Curve uncertainty. The shape and underlying distribution of the Master Curve show deviations with increased loading rate. The shape factor p is optimized with respect to the individual data, and it increases with <span><math><mrow><mover><mi>K</mi><mo>̇</mo></mover></mrow></math></span>, but deviations are not completely overcome. This can be linked to a change in distribution, which was demonstrated by an optimization of minimum fracture toughness K_min, which increases with temperature. It is argued that the cause for the observations is linked to both heating processes and local crack arrest that severely influence macroscopic fracture behavior. Also, an individual adjustment of p or K_min is not helpful due to the material-dependency in practice. It is recommended that fracture mechanics testing at elevated loading rates is performed close to or below T₀ in order to minimize the influence of dynamic loading conditions on the assessment.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553414","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}

{"title":"Finite element modeling for cohesive/adhesive failure of adhesive structures with a thermosetting resin","authors":"","doi":"10.1016/j.engfracmech.2024.110552","DOIUrl":"10.1016/j.engfracmech.2024.110552","url":null,"abstract":"<div><div>In this study, we established a novel method based on the finite element method (FEM) for predicting the strength of adhesive structures. Viscoplasticity, void growth, and cohesive zone model were introduced into the FEM to create a nonlinear damage growth (NDG) model. This model was used to comprehensively analyze the process zones within the adhesive layer. Furthermore, the embedded process zone approach was used to develop an interface constitutive law that averages the mechanical response of the adhesive layer. This modified Ma–Kishimoto (MMK) model can accurately represent the adhesive layer as an interface element and is computationally efficient. Furthermore, the study obtained the necessary interface properties for the MMK model from the NDG model, creating a numerical material test that can approximate the effect of the process zone. To validate the proposed method, single-lap shear tests were performed, and the accuracy of the predicted strength and deformation field was evaluated. The damage evolution in the NDG model and the MMK model were compared, and the scope of application of the MMK model was discussed. The results of this study can be used as a reference for the failure mechanism of thermosetting adhesives and establishment of design indices for adhesive structural strength.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572932","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}

{"title":"An anisotropic eigenfracture approach accounting for mixed fracture modes in wooden structures by the Representative Crack Element framework","authors":"","doi":"10.1016/j.engfracmech.2024.110572","DOIUrl":"10.1016/j.engfracmech.2024.110572","url":null,"abstract":"<div><div>Finite Element analysis of anisotropic fracture phenomena in wood is a challenging task, particularly when dealing with intricate loading scenarios and mode-specific behavior. The appeal of energetically motivated approaches, such as the eigenfracture method, is that they enable simulation of fracture without prior knowledge of the crack path. The promising eigenfracture method has shown good numerical performance for isotropic materials, and this contribution showcases its application to anisotropic materials. Wood is one such anisotropic material and in this manuscript, the directional dependence of both elasticity and fracture evolution are incorporated into the eigenfracture approach. Further, the eigenfracture approach is used in conjunction with Representative Crack Elements (RCE), which permit accurate modeling of physical crack deformations. The governing equations are systematically derived and implemented into the Finite Element framework. By representative numerical examples, some advantages over the alternative phase-field method are demonstrated. Another highlight of this work is that it is possible to provide a realistic ratio of the energy release rates parallel to and perpendicular to the fiber direction in order to achieve physically accurate crack patterns. Additionally, the calculation effort is reduced, because the unknowns required to determine the crack kinematics can be solved analytically at the material level, a feature that also enables parallelization.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572935","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}