Theoretical and Applied Fracture Mechanics最新文献

{"title":"Does double pre-notches have a greater impact than single pre-notch on the mechanical and fracture behavior of rock? Insights from three-point bending tests using the numerical approach of grain-based model","authors":"","doi":"10.1016/j.tafmec.2024.104624","DOIUrl":"10.1016/j.tafmec.2024.104624","url":null,"abstract":"<div><p>The mechanical performance of rock masses is significantly impacted by the existence of cracks. Distribution of the cracks may result in different mechanical or fracture behaviors of rock. To gain a preliminary understanding of such problems, a series of numerical tests of three-point bending (TPB) are designed and carried out with the consideration of single pre-notch and double pre-notches. The numerical method of grain-based model (GBM) approach is employed in this paper, with a validation implemented by comparing the results with previous experiments to demonstrate the reliability of this model. Afterward, a comprehensive investigation, including the mechanical behavior, strength characteristics, crack evolution and progressive failure mechanism of the above mentioned TPB tests are conducted. The conclusions are as follows: (1) During TPB tests, as the offset distance increases, the fracture mode of the single pre-notched specimens gradually transitions from Mode I to Mode II, with the peak fracture toughness occurring at a mixed Mode I-II fracture condition (2<em>p</em>/<em>s</em> = 0.4). Moreover, the failure angle, notch open degree and expansion area all tend to rise regardless of specimens of single or double pre-notches. (2) A thorough exploration of crack evolution shows that the specimens primarily fracture during the crack propagation and failure stages. Shear failure predominates among these stages, with microcracks mostly occurring inside the rock mineral grains. (3) When offset distance increases to a certain degree (2<em>p</em>/<em>s</em> = 0.8), the fracture of specimen ceases to be governed by the pre-notch; instead, it occurs directly from the middle of the beam specimen. This phenomenon can be attributed to the reduction of stress concentration at the notch tip, as inferred from analysis of the contact force chain. (4) In double pre-notched specimen, microcracks initiate at both pre-notches, but the final failure results from crack propagation at one notch tip. Compared to single pre-notched specimen, the presence of double pre-notches exhibits superior fracture resistance performance.</p></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141997356","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":"Cyclic stress–strain behavior of additively manufactured gamma prime strengthened superalloy at elevated temperatures","authors":"","doi":"10.1016/j.tafmec.2024.104623","DOIUrl":"10.1016/j.tafmec.2024.104623","url":null,"abstract":"<div><p>The γ́-precipitation hardened nickel-based superalloy IN939 manufactured by laser powder bed fusion (L-PBF) was subjected to cyclic loading to determine the cyclic stress–strain curve by short-cut procedure. The effect of building on loading direction/orientation was investigated. 〈0<!--> <!-->0<!--> <!-->1〉 crystallographic texture along the building direction was observed. The cyclic stress–strain curves were measured at 800 °C and 900 °C and the differences in cyclic plasticity were revealed. The specimens prepared by L-PBF with a building direction parallel to the loading axis exhibited the highest cumulative plastic deformation at both temperatures, while L-PBF with a building direction perpendicular to the loading axis was the lowest. Elastic moduli were determined and the differences were attributed to the crystallographic texture. In addition, conventionally cast IN939 was investigated as the reference material. Minor microstructural changes due to cyclic straining were inspected by transmission electron microscopy.</p></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142002210","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":"Explicit phase-field material point method for thermally induced fractures","authors":"","doi":"10.1016/j.tafmec.2024.104618","DOIUrl":"10.1016/j.tafmec.2024.104618","url":null,"abstract":"<div><p>Thermally induced fractures in solids pose significant challenges in various fields, such as aerospace, deep underground, and civil engineering structures. Numerical methods are effective for addressing such problems, with recent advancements in phase-field and material point methods demonstrating notable advantages in crack simulation. This paper presents a computational approach within an explicit material point method framework for coupling the solutions of temperature, displacement, and phase (damage) fields. The displacement and phase fields are intricately linked through a history-dependent strain field and degradation function. The model incorporates temperature-induced strains from temperature gradients for coupling the temperature and displacement fields. In addition, the model accounts for the detrimental effects of cracks on heat conduction, ensuring a comprehensive representation of the coupled system. Two numerical examples involving thermomechanical coupling and dynamic crack branching were used to validate the effectiveness of the proposed method. Finally, the proposed method was applied to simulate the thermal shock and large deformations of thin circular ceramic specimens, successfully replicating the initiation and propagation of cracks observed during the experiment. The simulated thermally induced fractures exhibited periodic and hierarchical characteristics consistent with the experimental findings.</p></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142049306","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":"Quantitative calculation of rock strain concentration and corresponding damage evolution analysis","authors":"","doi":"10.1016/j.tafmec.2024.104615","DOIUrl":"10.1016/j.tafmec.2024.104615","url":null,"abstract":"<div><p>Understanding the critical strain and damage evolution process of sandstone can help engineers more accurately predict the failure modes and critical states of sandstone in actual engineering structures. Therefore, this article quantitatively analyzes the strain field data obtained through digital image correlation (DIC), and for the first time establishes a strain concentration calculation model (SCCM) to analyze the critical strain, compaction, and damage evolution process of sandstone under uniaxial compression conditions. The experimental results show that both elastic and plastic strain zones exist on the specimen surface. The proportion curve of strain concentration calculated by SCCM indicates that the strain field <em>ε</em>₁ generally undergoes two stages: the elastic strain fluctuation stage and the plastic strain development stage. In contrast, the strain field <em>ε</em>₂ exhibits roughly three stages: a rapid change phase, a slow change phase, and a stability phase. Microscopic strain analysis reveals an overlap between the compaction and damage processes of the specimen, and the critical strain value <em>ε_md</em> for micro-damage in the specimen is significantly smaller than values obtained by traditional discrimination methods. Specifically, when the defect width of the specimen is 15 mm and 40 mm, the mean <em>ε_md</em> vaules are approximately 0.006016 and 0.00539, respectively. In contrast, the mean critical strain values determined by traditional discrimination methods are 0.0180 and 0.0178, respectively. The above research results provide a new method for analyzing the strain field data of geotechnical materials, serving the optimization of engineering structure design.</p></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142041181","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":"Influence of fissure distribution characteristics on the dynamic response of fissured Rock: Quantity and spacing","authors":"","doi":"10.1016/j.tafmec.2024.104620","DOIUrl":"10.1016/j.tafmec.2024.104620","url":null,"abstract":"<div><p>The impact test of red sandstone with different fissure distribution was carried out by Split Hopkinson Pressure Bar (SHPB). The failure process of the specimen in the time dimension was captured by high-speed camera and digital image correlation (DIC). The crushing characteristics of the specimen were discussed from the fractal dimension. Furthermore, the influence of fissure distribution characteristics (quantity and spacing of fissures) on the mechanical properties and fracture behavior of fissured red sandstone was analyzed. The experimental results show that the fissure spacing is negatively correlated with the dynamic compressive strength and peak strain of specimen, while the fissure quantity is negatively correlated with the dynamic compressive strength and positively correlated with the peak strain. Cracks are categorized into five types based on the manner of their initiation and expansion. The crack initiation and propagation are jointly affected by tensile stress and shear stress, but the tensile stress is dominant. With the increase of the fissure quantity, the failure mode changes from tensile failure to tensile-shear mixed failure. The increase of fissure spacing does not change its failure mode, but the formation mode of the main crack changes. The fractal dimension increases with the increase of the fissure quantity, and decreases with the increase of the fissure spacing, i.e., the larger the fissure quantity is, the higher the degree of fragmentation is, and the larger the fissure spacing is, the lower the degree of fragmentation is. The research results can provide a theoretical reference for the study of dynamic failure mechanism of rock mass with non-persistent discontinuities.</p></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141993390","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":"Study on the dynamic fracture behavior of anisotropic CCNBD shale specimens under different impact angles","authors":"","doi":"10.1016/j.tafmec.2024.104616","DOIUrl":"10.1016/j.tafmec.2024.104616","url":null,"abstract":"<div><p>Drilling and fracturing are the key technologies for shale gas extraction, while most of the loads generated during rock drilling or fracturing are dynamic. In this study, dynamic impact experiments were conducted on the cracked chevron-notched Brazilian disc shale specimens with different chevron-notched crack (CNC) inclinations (<em>β</em>) and layer inclinations (<em>α</em>) by the split Hopkinson pressure bar. The results show that the dynamic peak load and dissipated energy increases with the increase of <em>β</em>, <em>α</em>, and strain rate, but their changing trends are different. The generation and expansion of cracks during the specimen failure process are mainly affected by <em>β</em>. As <em>β</em> increases, the failure type of the specimen can be divided into pure mode I fracture, mode I-II mixed fracture, pure mode II fracture, mixed tension-shear failure, and Brazilian splitting failure. The increase in strain rate will lead to a decrease in the time for crack initiation and propagation as well as an increase in secondary cracks. In addition, the mode I fracture toughness (<em>K</em>_Ⅰ<em>_C</em>) and mode II fracture toughness (<em>K</em>_Ⅱ<em>_C</em>) both grow with the increase of <em>α</em> and strain rate. The <em>K</em>_Ⅱ<em>_C</em> predicted by the generalized maximum tangential stress criterion (GMST) exhibits more accurate.</p></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142021486","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":"Atomistic and continuum Ascertainment of The crack tip stress fields in anisotropic elastic cubic media","authors":"","doi":"10.1016/j.tafmec.2024.104613","DOIUrl":"10.1016/j.tafmec.2024.104613","url":null,"abstract":"<div><p>The article provides a comparative analysis of stresses associated with the crack tip in an anisotropic elastic medium with cubic crystalline symmetry of elastic properties under mixed loading conditions obtained by two fundamentally different approaches: atomistic simulations and continuum fracture mechanics methods. The atomistic modelling approach is premised on the application of the molecular dynamics (MD) method implemented in the open source code program Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The continuum mechanics approach is based on the classical elasticity theory of anisotropic media, in which the mechanical fields associated with the crack tip are represented by the crack tip stress and displacement series expansions generalizing the well-known classical asymptotical presentation of M. Williams to the case of anisotropic media. Using the MD method, a large series of computations of the loading of monocrystalline copper and aluminum plates with a face-centered cubic crystal lattice weakened by a central crack applying the embedded atom potential (EAM) was implemented. MD modeling is aimed at determining the atomic stresses and strains near the crack tip. The computed atomic stresses were compared with the stress field determined by the continuum elasticity theory of anisotropic media for crystal lattices with cubic symmetry of elastic properties. A comparative analysis was carried out for the angular dependencies of the stress and strain tensor components at various selected distances from the crack tip for the entire range of mixed deformation forms starting from pure tensile loading and ending with forms close to pure transverse shear. It is ascertained that the crack tip fields determined on the basis of two fundamentally different approaches, precisely, discrete and continuum, are completely consistent with each other. It is established that mathematical methods of continuum fracture mechanics can be applied to describe stress, strain and displacement fields at the atomic level.</p></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141984888","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":"Assessment of structural materials containing notch-type defects: A comprehensive validation of the FAD-TCD methodology on metallic and non-metallic materials","authors":"","doi":"10.1016/j.tafmec.2024.104612","DOIUrl":"10.1016/j.tafmec.2024.104612","url":null,"abstract":"<div><p>This paper provides a comprehensive description, and the subsequent validation, of a structural integrity assessment methodology of structural materials containing notch-type defects. The approach is based on the combination of Failure Assessment Diagrams (FAD) and the Theory of Critical Distances (TCD). The former provides the general assessment tool, which is exactly the same one as that used for crack-like defects, whereas the latter provides the notch effect correction required for the analysis of this type of defects. Finally, the proposed methodology is validated on a number of metallic and non-metallic structural materials, with 1,106 experimental results on different types of testing specimens, covering four structural steels, aluminium alloys 7075-T651 and 6060-T66, PVC, PMMA, PA6, fibre-reinforced PA6, 3D printed (Fused Filament Fabrication) ABS, PLA and graphene reinforced PLA, granite and limestone. The results show how the FAD-TCD methodology provides safe reasonably conservative assessments on the mentioned structural materials in the presence of notch-type defects.</p></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0167844224003628/pdfft?md5=bae510efc2cc42e3b8c6d5b84f8f9fa8&pid=1-s2.0-S0167844224003628-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141991369","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":"Study on the mixed fracture characteristics of concrete-rock Brazilian disks with different fracture angles","authors":"","doi":"10.1016/j.tafmec.2024.104614","DOIUrl":"10.1016/j.tafmec.2024.104614","url":null,"abstract":"<div><p>The fracture characteristics of cracked straight-through Brazilian discs for concrete-rock composites (CSTBD-CRC) with different fracture inclination angles (Mode I-II) were investigated to evaluate the stability of concrete reinforcement engineering. Acoustic emission (AE) and digital image correlation (DIC) techniques were employed to study crack propagation and fracture modes in CSTBD-CRC Brazil splitting tests, as well as the entropy evolution of AE and DIC. Additionally, 3D scanning technology and fractal theory were utilized to investigate the effect of the fracture mode on the fracture surface morphology. The results indicate that both the fracture energy and peak load of the CSTBD-CRC increase with increasing fracture inclination angle. Moreover, the section fractal dimensions of 0°, 10°, 15° and 25° samples are 2.01879, 2.01528, 2.01186, and 2.01072. Shear fracture mode increases as the dip angle increases and the fracture surface morphology decreases in fractal dimension. Notably, sharp increases in entropy values for both AE and DIC occurred at peak load, suggesting their use as failure criteria for CSTBD-CRC specimens. Furthermore, cracks were found to initiate at the tips of preexisting cracks within the concrete. The displacement in the x direction undergoes the most significant changes on both sides of the crack during crack growth, while the strain in the x direction experiences its greatest variations at the crack location.</p></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141984841","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":"Advances in low cycle fatigue probabilistic modeling","authors":"","doi":"10.1016/j.tafmec.2024.104611","DOIUrl":"10.1016/j.tafmec.2024.104611","url":null,"abstract":"<div><p>New advances in the probabilistic S-N model proposed by Castillo and Canteli are presented. The requirements for a S-N model derivation to be valid are emphasized, in particular, that of the compatibility between the statistical distributions of lifetime and stress reference variable. The definition of the generalized reference variable (GRV) in the S-N field, as <span><math><mrow><mi>GRV</mi><mo>=</mo><mi>ψ</mi><mo>·</mo><msub><mi>σ</mi><mi>M</mi></msub></mrow></math></span>, where <span><math><mi>ψ</mi></math></span> is a non-dimensional factor derived from the <span><math><mrow><mi>σ</mi><mo>-</mo><mi>ε</mi></mrow></math></span> law of the material, allows the former model to be applied to LCF data. The new model ensures the incontrovertible and unitary definition of the scatter band in the S-N field and the justification of an asymptotic lower limit of the lifetime, <span><math><mrow><msub><mi>N</mi><mn>0</mn></msub><mo>.</mo></mrow></math></span> As a result, the stress- and strain-based approaches can be envisaged as a unique probabilistic <span><math><mrow><mi>ψ</mi><msub><mi>σ</mi><mi>M</mi></msub><mo>-</mo><mi>N</mi></mrow></math></span> approach applicable in the three conventional, i.e., LCF, HCF and VHCF domains. An extension as the <span><math><mrow><mi>ψ</mi><msub><mi>σ</mi><mi>M</mi></msub><mo>-</mo><mi>R</mi><mo>-</mo><mi>N</mi></mrow></math></span> model that includes the stress ratio effect is presented. The utility of the model is confirmed with the assessment of LCF data from different external experimental campaigns.</p></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0167844224003616/pdfft?md5=573b5691be7e74f6e4d6665b3391b5f6&pid=1-s2.0-S0167844224003616-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142041258","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}