Theoretical and Applied Fracture Mechanics最新文献

{"title":"Harnessing waste for sustainable construction: A novel synthesizing activators from waste for one-part geopolymer concrete and evaluating its fracture toughness","authors":"","doi":"10.1016/j.tafmec.2024.104745","DOIUrl":"10.1016/j.tafmec.2024.104745","url":null,"abstract":"<div><div>Geopolymer concrete garners significant attention due to its potential to mitigate pressing global challenges, such as CO₂ emissions and waste management for disposal. However, using more expensive commercial activators has posed a significant obstacle to practical implementation. Therefore, scientists want to develop methods to extract powdered activators from agricultural and industrial waste materials. To this end, the study has sought to create innovative activators derived from waste glass powder (WGP) and silica-rich rice husk ash (RHA) to create one-part geopolymer concrete (OPGC). Ground granulated blast-furnace slag is utilized as a precursor material for preparing binder, with varying ratios of WGP/RHA to sodium hydroxide (NaOH) from 0.50 to 1.75 at 0.25 intervals. Twenty-four distinct mixtures of OPGC were prepared using the materials mentioned above and evaluated for their compressive strength and fracture toughness. The primary objective of this research is to evaluate the mode I, III, and I/III fracture toughness of OPGC using edge-notched disc bend specimens. Additionally, a 1 % steel fiber dosage was introduced into the OPGC to reduce brittleness. The microstructural characteristics were examined through X-ray diffraction and scanning electron microscopy. Findings reveal that the fracture toughness of OPGC improves with the RHA to NaOH ratio up to 1.0, peaking at 1.09 MPa·m^0.5. Likewise, the fracture toughness increases with the WGP to NaOH ratio up to 0.75, reaching a peak value of 1.20 MPa·m^0.5. Beyond these respective ratios, a decrease in fracture toughness was observed. Nonetheless, incorporating fibers into OPGC consistently improved the fracture toughness across all mixtures. Mode I fracture toughness is greater than I/III and III, emphasizing the significance of Mode III compared to other fracture modes.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142592947","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":"Analysis of tooth root three-dimensional fatigue crack initiation, propagation, and fatigue life for spur gear transmission","authors":"","doi":"10.1016/j.tafmec.2024.104741","DOIUrl":"10.1016/j.tafmec.2024.104741","url":null,"abstract":"<div><div>The gears in aviation gear systems are susceptible to fatigue fracture due to high-speed, heavy-load, and load alternation operating conditions. Therefore, a numerical calculation model with multiple mesh positions loading form has been proposed in this paper to analyze the fatigue crack initiation and propagation behavior, and to estimate the fatigue life of these gears. The fatigue life of the gear is determined by separately calculating the fatigue crack initiation life and the fatigue crack propagation life. The tooth root fatigue stress and the fatigue initiation life are calculated by the multi-axial fatigue life prediction method with the Smith-Watson-Topper criterion and the critical plane method. Afterwards, the tooth root stress–strain field is calculated in Finite element (FE) software and the stress intensity factors of the crack tip are calculated in three-dimensional (3D) crack analysis software. Then, the tooth root fatigue crack propagation trajectory and the fatigue crack propagation life are obtained separately. Finally, the influence mechanism of the loading conditions, the geometry parameters of gears, and the initial crack positions on the tooth root fatigue crack initiation life, propagation life, and fatigue crack propagation trajectory are analyzed, and a tooth fatigue test bench is built for verifying the crack propagation trajectory.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578631","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":"Measurement of fracture toughness in high-strength alloys via modified limit load analysis using flat-end cylindrical indenter","authors":"","doi":"10.1016/j.tafmec.2024.104740","DOIUrl":"10.1016/j.tafmec.2024.104740","url":null,"abstract":"<div><div>In this paper, fracture toughness (K_J) was measured for high strength rail steels and AL2024-T351 via chamfered cylindrical flat-end indentation. The indentation loading focused on applying the J-integral approach to curves of load versus indentation depth up to the crack initiation point based on a modified limit load via multiple indenter sizes. To promote single indenter size for practical use, virtual indenter sizes were proposed based on geometrical similarities, where the stress intensity factors according to J-integral approach were extrapolated to minimize the contribution of the plastic component of J-integral (J_P). However, when the indentation method for K_J is applied to high strength rail steels, a consideration for the modification of the J-integral approach is suggested with the inclusion of stress triaxiality effect to accommodate the pressure sensitivity experienced in compression-based testing for some materials. The K_J values were seen to agree well with fracture toughness from conventional testing (K_IC) for all materials in the study showing a relative difference below 5% except the JP rail steel, which showed only a relative difference of 16%. This is based on the condition that pressure sensitivity effect is present for the rail steels and not for AL2024-T351. The study also compares different indenter sizes, which show similar pressure and normalized depth profiles consequently offering the potential for a non-destructive means to measure mechanical properties and fracture toughness via micro-sized indenters. This opens an opportunity for further studies in material characterization capabilities across a wide range of industries in the future.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578633","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":"Fracture assessment of blunt V-notched 3D-printed ABS: Proposing a new specimen for testing and different criteria for prediction","authors":"","doi":"10.1016/j.tafmec.2024.104742","DOIUrl":"10.1016/j.tafmec.2024.104742","url":null,"abstract":"<div><div>In this research, a new specimen, called double-edge notched diagonally loaded square plate (DEN-DLSP), is proposed and tested in order to examine the tensile fracture behavior of blunt V-notched Acrylonitrile Butadiene Styrene (ABS) material additively manufactured by using the fused deposition modeling (FDM) method. This test specimen is actually a modified version of the round-tip V-notched diagonally loaded square plate (RV-DLSP) specimen having two edge round-tip V-notches instead of the internal rhombic slot with blunt V-shaped corners. The DEN-DLSP specimen requires less material for fabrication, and dealing with FDM-made polymeric materials, it can be produced without generating undesired local sites of stress concentration. Five different raster angles in unidirectional orientations, the notch opening angle of 90 (deg.), and three different notch tip radii are examined in this study. It is shown that the virtual isotropic material concept (VIMC) in combination with the point stress (PS), mean stress (MS), and averaged strain energy density (ASED) criteria as well as the extended finite element method (XFEM) coupled with the cohesive zone model (CZM) could be satisfactorily used to estimate the fracture loads of the 3D-printed DEN-DLSP specimens. It is revealed that using DEN-DLSP specimen for the mode I notch fracture toughness testing of 3D-printed ABS material is successful, and it is suggested to be used in similar tests for other additively manufactured polymeric materials as well as various engineering materials.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572531","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":"Lignin fiber reinforced gypsum-cement composite materials: Investigation of fracture properties and freeze–thaw behaviors","authors":"","doi":"10.1016/j.tafmec.2024.104738","DOIUrl":"10.1016/j.tafmec.2024.104738","url":null,"abstract":"<div><div>The weak crack resistance and water stability of gypsum-cement composite materials limit their further development in the construction sector. In order to enhance the performance and extend the application of gypsum-cement composite materials, gypsum-cement composite materials were prepared using gypsum, granulated blast furnace slag, cement, and lignin fiber. Cement content ranged from 10 % to 20 %, while lignin fiber content varied between 0 and 0.4 % by weight. To assess their fracture performance and moisture durability, three-point bending (TPB) fracture tests and compressive tests were conducted on these mixtures. Furthermore, Scanning Electron Microscopy (SEM) was utilized to explore the role of fibers in improving the mixture’s properties. The results demonstrated a clear correlation between increased cement content and improvements in both fracture toughness (<em>K</em>_IC) and fracture energy (<em>G</em>_F). Optimal performance regarding the stress intensity factor was observed at a 0.2 % lignin fiber content after curing for both 7 and 28 days. Despite this, the inclusion of 0.4 % fiber content in specimens with 20 % cement resulted in the highest fracture energies, suggesting an enhanced deformation capacity even though peak loads decreased. After 5 F-T cycles, specimens incorporating 0.2 % fiber exhibited the lowest loss rate of <em>K</em>_IC and <em>G</em>_F. With a cement content of 10 %, the compressive strengths rose with higher fiber content across all specimens undergoing identical freeze–thaw cycles. Conversely, at a 20 % cement content, maximum strength was achieved with a 0.2 % fiber content, establishing it as the optimal fiber concentration due to its resistance to compressive strength loss during freeze–thaw testing. SEM analysis revealed that lignin fiber ends were well-integrated within the matrix, with Calcium Silicate Hydrates (C-S-H) clearly visible on fiber surfaces. Additional entrapped air voids in the gypsum-cement composite material were generated due to the porous structure of lignin fiber, which could arrest the crack growth energy provided optimum fiber was incorporated. In addition, the bridging effect fiber also contributes to the overall strength and durability of the mixtures.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554574","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":"Defect characteristics-based low-cycle fatigue life prediction model for additive manufactured Ti-6Al-4 V alloys","authors":"","doi":"10.1016/j.tafmec.2024.104737","DOIUrl":"10.1016/j.tafmec.2024.104737","url":null,"abstract":"<div><div>Volumetric defect is a significant factor that influences the fatigue life assessment accuracy in additive manufactured (AM) metals. In order to accurately assess the effects of volumetric defects on fatigue property of AM alloys, this study investigates the influence of geometric characteristics such as size, location, and shape of volumetric defects on low-cycle fatigue (LCF) properties. The results indicate that these factors have a significant influence on the fatigue life of material, and the volumetric defect location is found to be the most critical factor. In order to identify the critical volumetric defects on the fatigue fracture, a defect characteristic parameter “<em>P</em>” is proposed to characterize the influence of volumetric defect characteristics on the fatigue performance of material. Subsequently, a low-cycle fatigue life prediction model for AM metals that considers the geometrical characteristics of volumetric defects is established based on the relationship between <em>P</em>-parameter and low-cycle fatigue life. The accuracy of the prediction model is within 1.5x error band, which is significantly improved compared to the Manson-Coffin (M−C) model and Smith-Watson-Topper (SWT) model.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578632","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":"A peridynamic compensated critical energy density criterion for mixed-mode fracturing in quasi-brittle materials","authors":"","doi":"10.1016/j.tafmec.2024.104736","DOIUrl":"10.1016/j.tafmec.2024.104736","url":null,"abstract":"<div><div>This study integrates a compensated critical energy density criterion (CCED) into the ordinary state-based peridynamics framework to enable detailed analysis of mode I, mode II, and mixed-mode fracturing. The proposed bond failure criterion builds upon the advantages of the traditional critical energy density (CED) to enable precise calculation of strain energy density. Additionally, the critical bond rotation criterion (CR) is employed to account for shear bonds that the CED might overlook. Using the peridynamic differential operator (PDDO) format in formulating the entire computational framework enhances both accuracy and numerical stability. The model’s validation is conducted through benchmark examples, including the mode I double cantilever beam test, the mode II compact shear test, and a mixed-mode mechanical fracturing test in pre-notched specimens with central borehole loading. Convergence studies, comparative analyses with finite element method simulations and theoretical solutions thoroughly examine the proposed model’s performance and accuracy.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554573","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 of individual lack-of-fusion defects in the fatigue performance of laser-powder bed fusion Ti6Al4V alloys: A finite element analysis","authors":"","doi":"10.1016/j.tafmec.2024.104735","DOIUrl":"10.1016/j.tafmec.2024.104735","url":null,"abstract":"<div><div>Laser-Powder Bed Fusion (L-PBF) techniques have revolutionized the production of Ti6Al4V alloys across various industries. However, the widespread adoption of L-PBF Ti6Al4V alloys is impeded by their inadequate fatigue performance, particularly in high cycle regimes. A significant contributing factor to this limitation is the presence of internal defects inherent to the L-PBF process, act as sites for fatigue crack initiation. Previous investigations have focused on the fatigue performance of L-PBF Ti6Al4V alloys with gas porosities, while research on lack-of-fusions (LOFs) which are recognized as the most detrimental defects, remains limited. In order to deepen our understanding of the factors influencing the reduced fatigue performance observed in L-PBF Ti6Al4V alloys associated with inherent LOFs, this study employed three-dimensional (3D) finite element analysis approaches. Such approaches allow to assess fatigue indicator parameters to evaluate fatigue life and predict fatigue crack propagation. A 3D average Smith-Watson-Topper method has been proposed, which is able to rationally estimate the fatigue life of L-PBF Ti6Al4V. In addition, a novel finite element method has been developed to accurately calculate stress intensity factors along irregular shaped crack front of a notch-like feature embedded on a LOF. Additionally, parametric studies were conducted to gain further insights into the influence of LOFs on fatigue performance. The results shown the presence of embedded humps and notch-like features, and their topologies play key roles in the fatigue performance of LOF predominated L-PBF Ti6Al4V alloys.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572528","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 of type-I crack propagation in rock monitored by fiber Bragg grating","authors":"","doi":"10.1016/j.tafmec.2024.104734","DOIUrl":"10.1016/j.tafmec.2024.104734","url":null,"abstract":"<div><div>The occurrence of rock mass engineering disasters can be reduced significantly by obtaining the key information in the process of rock internal fracture accumulation and evolution through advanced monitoring means and taking certain preventive measures. Through fiber Bragg grating monitoring tests of the type-I crack propagation in rock, the spectral characteristics of the fiber Bragg grating in the process of rock failure were analyzed, the bandwidth expansion was extracted to characterize the local tensile strain during the crack propagation process, and the damage variable based on the bandwidth expansion was calculated to describe the type-I crack propagation process. The research results showed the following: (1) The fiber Bragg grating generated a non-uniform local tensile strain during type-I crack propagation. The bandwidth expansion of the wave spectrum was positively correlated with the local tensile strain. The change in the characteristics of the wave spectrum could provide the local real strain in the process of crack propagation. (2) During the steady propagation of the type-I crack, the bandwidth increased obviously, while the number of acoustic emission events was relatively small, and most of them were in the process zone. The gentle increase in the bandwidth corresponded to the unstable growth stage of the type-I crack, which could be used as a precursor of rock sample instability. During loading, the maximum tensile strain of the type-I crack was 6 %, while the maximum shear strain reached 1.8 %, primarily attributed to tensile failure. The average value of fracture toughness K_IC, based on the equivalent linear elastic fracture mechanics model, was determined to be 1.21 MPa·m^1/2, and the average value of fracture energy G_f was calculated as 57.7 N/m. The variation of peak reflectivity in fiber Bragg grating was associated with the closure of pre-existing defects and the propagation of microcracks in rocks, resulting in unstable shear strain at crack extension sites. (3) The damage variable <em>D</em> defined by the bandwidth broadening began to become concentrated and accumulated in the crack steady growth stage, and it increased slowly in the crack intensification and evolution stage. The grating was sensitive to changes when it was pasted to the surface at 90°, but it could easily fracture or become unable to capture spectral signals in time. Based on a comprehensive comparison, the monitoring effect was the best when the grating was pasted at 60° relative to the crack.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554571","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":"Failure characteristics and pressure relief effectiveness of non-persistent jointed rock mass with holes","authors":"","doi":"10.1016/j.tafmec.2024.104733","DOIUrl":"10.1016/j.tafmec.2024.104733","url":null,"abstract":"<div><div>In tunnel engineering, the rock mass contains a significant number of irregularly distributed joints, and typically exhibits high energy accumulation, thereby posing a risk of rockburst occurrence. Therefore, it is of paramount importance to investigate the fracture propagation behavior in jointed rock masses and assess the impact of borehole pressure relief on mitigating rockburst occurrences for effective prevention and control measures. This paper focuses on failure characteristics and pressure relief effectiveness of non-persistent jointed rock mass with holes through laboratory testing and numerical simulation. In laboratory experiments, rock samples are prepared to include a range of crack dip angles and circular holes. Then, the crack propagation law of crack inclination and circular hole is studied by AE and DIC technology. The experimental results show that with the increase of fracture dip angle, the peak strength and energy change of the sample decrease first and then increase. Due to the existence of holes, the crack propagation direction of the original crack is changed. After drilling, the strain energy of the sample is obviously reduced, which shows that the drilling pressure relief effect is obvious, which can effectively reduce the energy accumulated inside the rock mass and reduce the risk of rockburst. Finally, the PFC numerical simulation software is used to analyze the micro-failure process and energy change law of the sample from three aspects: the relative position of cracks and holes, the diameter of boreholes and the spacing of boreholes. Further understanding of the energy dissipation law and mechanical behavior characteristics of jointed rock mass provides a reference for exploring the pressure relief effect of rock mass and preventing rockburst.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554577","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}