Pub Date : 2026-04-01Epub Date: 2026-02-06DOI: 10.1016/j.tafmec.2026.105492
Qiang Zeng , Zhaoxin Du , Tianhao Gong , Shuzhi Zhang
In this study, a multiscale, partially lamellar TC18 (Ti-5Al-5Mo-5 V-1Cr-1Fe) alloy was fabricated by isothermal annealing followed by aging. The effects of temperature variations at different processing stages on the microstructural evolution and mechanical properties were systematically investigated. Crack propagation behavior was characterized through in situ tensile and three-point bending tests. The results reveal that the combination of multiscale features and lamellar structures enables the TC18 alloy to achieve an excellent strength–toughness balance. Notably, variations in the primary α phase (αp) content during the annealing stage have a significant impact on the alloy's fracture toughness and fracture behavior. Lower annealing temperatures promote the formation of numerous α clusters, which facilitate slip during deformation to accommodate strain; consequently, crack propagation is mainly governed by slip accumulation and separation. Furthermore, the key microstructural features contributing to crack deflection include coarse αp phases, α clusters, and grain-boundary α (αGB). Slip activity within coarse αp phases and α clusters induces dislocation pile-ups at phase or cluster boundaries, thereby promoting crack deflection. Additionally, coarse αp phases and α clusters with “soft” orientations (aligned at ±40° to ±70° relative to the tensile axis) significantly enhance the alloy's fracture toughness.
{"title":"Mechanistic transition from slip-driven to shear-band-controlled crack propagation induced by α-phase variation in multiscale TC18 alloy","authors":"Qiang Zeng , Zhaoxin Du , Tianhao Gong , Shuzhi Zhang","doi":"10.1016/j.tafmec.2026.105492","DOIUrl":"10.1016/j.tafmec.2026.105492","url":null,"abstract":"<div><div>In this study, a multiscale, partially lamellar TC18 (Ti-5Al-5Mo-5 V-1Cr-1Fe) alloy was fabricated by isothermal annealing followed by aging. The effects of temperature variations at different processing stages on the microstructural evolution and mechanical properties were systematically investigated. Crack propagation behavior was characterized through in situ tensile and three-point bending tests. The results reveal that the combination of multiscale features and lamellar structures enables the TC18 alloy to achieve an excellent strength–toughness balance. Notably, variations in the primary α phase (α<sub>p</sub>) content during the annealing stage have a significant impact on the alloy's fracture toughness and fracture behavior. Lower annealing temperatures promote the formation of numerous α clusters, which facilitate slip during deformation to accommodate strain; consequently, crack propagation is mainly governed by slip accumulation and separation. Furthermore, the key microstructural features contributing to crack deflection include coarse α<sub>p</sub> phases, α clusters, and grain-boundary α (α<sub>GB</sub>). Slip activity within coarse α<sub>p</sub> phases and α clusters induces dislocation pile-ups at phase or cluster boundaries, thereby promoting crack deflection. Additionally, coarse α<sub>p</sub> phases and α clusters with “soft” orientations (aligned at ±40° to ±70° relative to the tensile axis) significantly enhance the alloy's fracture toughness.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105492"},"PeriodicalIF":5.6,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189096","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 : 2026-04-01Epub Date: 2026-01-09DOI: 10.1016/j.tafmec.2026.105452
Xiangdong Zhang , Yao Dong , Wenliang Li , Yu Zhang , Lijuan Su , Guanjun Cai , Qiong Wu
The accumulation of coal gangue (CG) as an industrial solid waste has become increasingly severe, and its resource utilization is of great significance for promoting low-carbon development in the construction industry. To enhance the utilization of coal gangue (CG), this study introduces for the first time a composite modification technique combining “physical coating and chemical immersion” for coal gangue aggregate (CGA), which was used to fabricate coal gangue aggregate concrete (CGAC). Through multi-scale experiments and characterization techniques, the synergistic modification mechanisms of the composite method on the properties of coal gangue aggregate (CGA) and concrete are systematically investigated, with a focus on analyzing the mechanical characteristics and fracture behavior of CGAC. Experimental results indicate that the composite modification significantly improves the fundamental physical and mechanical properties of CGA, optimizing its morphological characteristics, including sphericity, elongation, flatness, and angularity. The mechanical properties of the modified CGAC are notably enhanced, with 28d compressive strength, splitting tensile strength, and flexural strength increasing by 39.7%, 45.1%, and 42.5%, respectively, compared to the control group. Based on three-point bending fracture tests combined with digital image correlation (DIC) technology, it is found that the cracking load, ultimate load, fracture toughness, and fracture energy of the composite-modified CGAC are significantly improved, demonstrating superior crack resistance. Microscopic tests reveal that sodium silicate and silane coupling agents chemically strengthen the interfacial bonding between the cement matrix and CGA, forming a dense interfacial transition zone (ITZ), which further enhances the overall performance of CGAC. By leveraging the synergistic mechanism of “physical coating to address structural defects + chemical immersion to enhance interfacial chemistry,” this approach achieves dual reinforcement of the interfacial transition zone (ITZ). Compared to single modification methods, it leads to significant improvements in key properties such as aggregate mechanical strength and concrete fracture toughness. This study provides a solid theoretical foundation and practical technical support for the research on the fracture mechanical properties of CGAC.
{"title":"Study on the mechanical properties and fracture behavior of coal gangue aggregate concrete modified by physical-chemical composite","authors":"Xiangdong Zhang , Yao Dong , Wenliang Li , Yu Zhang , Lijuan Su , Guanjun Cai , Qiong Wu","doi":"10.1016/j.tafmec.2026.105452","DOIUrl":"10.1016/j.tafmec.2026.105452","url":null,"abstract":"<div><div>The accumulation of coal gangue (CG) as an industrial solid waste has become increasingly severe, and its resource utilization is of great significance for promoting low-carbon development in the construction industry. To enhance the utilization of coal gangue (CG), this study introduces for the first time a composite modification technique combining “physical coating and chemical immersion” for coal gangue aggregate (CGA), which was used to fabricate coal gangue aggregate concrete (CGAC). Through multi-scale experiments and characterization techniques, the synergistic modification mechanisms of the composite method on the properties of coal gangue aggregate (CGA) and concrete are systematically investigated, with a focus on analyzing the mechanical characteristics and fracture behavior of CGAC. Experimental results indicate that the composite modification significantly improves the fundamental physical and mechanical properties of CGA, optimizing its morphological characteristics, including sphericity, elongation, flatness, and angularity. The mechanical properties of the modified CGAC are notably enhanced, with 28d compressive strength, splitting tensile strength, and flexural strength increasing by 39.7%, 45.1%, and 42.5%, respectively, compared to the control group. Based on three-point bending fracture tests combined with digital image correlation (DIC) technology, it is found that the cracking load, ultimate load, fracture toughness, and fracture energy of the composite-modified CGAC are significantly improved, demonstrating superior crack resistance. Microscopic tests reveal that sodium silicate and silane coupling agents chemically strengthen the interfacial bonding between the cement matrix and CGA, forming a dense interfacial transition zone (ITZ), which further enhances the overall performance of CGAC. By leveraging the synergistic mechanism of “physical coating to address structural defects + chemical immersion to enhance interfacial chemistry,” this approach achieves dual reinforcement of the interfacial transition zone (ITZ). Compared to single modification methods, it leads to significant improvements in key properties such as aggregate mechanical strength and concrete fracture toughness. This study provides a solid theoretical foundation and practical technical support for the research on the fracture mechanical properties of CGAC.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105452"},"PeriodicalIF":5.6,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978848","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 : 2026-04-01Epub Date: 2026-01-08DOI: 10.1016/j.tafmec.2026.105453
Bing Fan , Li Song , Bowen Guo , Guojie Luo , Zhimeng Gao , Weiping Wu , Hongliang Fang , Tong Li , Zhong Liu
This study investigates the influence of sulfate corrosion and freeze-thaw cycles on the mixed mode I-II damage and fracture behavior of concrete. First, the mass loss and dynamic elastic modulus of concrete beams after different freeze-thaw cycles were measured, and the internal pore structure and mineral composition were analyzed using NMR and XRD. Subsequently, fracture tests under quasi-static loading were conducted on concrete beams in combination with the acoustic emission technique. The evolution patterns of the AE energy, AF-RA parameters, and b-value under sulfate corrosion and freeze-thaw cycles were systematically analyzed. Finally, the finite element method was employed to explore the mixed mode I-II damage scale and double-K fracture parameters. Results indicate that: (1) the coupling effect of freeze-thaw cycles and sulfate erosion exhibits a dual-mechanism behavior, characterized by initial matrix micro-densification followed by accelerated damage propagation, which ultimately culminates in significant deterioration of the fracture bearing capacity of the material. (2) with an increase in freeze-thaw cycles, the accumulated AE energy at peak load, the shear failure ratio, the critical damage scale, and the double-K fracture toughness for both mode I and mixed mode I-II cracks exhibit a consistent pattern of an initial increase followed by a subsequent decrease. (3) compared with mode I fracture, mixed mode I-II fracture exerts effects on the proportion of shear failure, critical damage scale, and cumulative AE energy, whereas it exerts a relatively minor effect on the double-K fracture parameters. (4) in contrast to water freeze-thaw environment, sulfate solution freeze-thaw induces significantly different evolutionary patterns in cumulative AE energy, AF, RA, and b-value
{"title":"Investigation of mixed mode I-II damage and fracture properties of concrete subjected to sulfate corrosion and freeze-thaw cycles","authors":"Bing Fan , Li Song , Bowen Guo , Guojie Luo , Zhimeng Gao , Weiping Wu , Hongliang Fang , Tong Li , Zhong Liu","doi":"10.1016/j.tafmec.2026.105453","DOIUrl":"10.1016/j.tafmec.2026.105453","url":null,"abstract":"<div><div>This study investigates the influence of sulfate corrosion and freeze-thaw cycles on the mixed mode I-II damage and fracture behavior of concrete. First, the mass loss and dynamic elastic modulus of concrete beams after different freeze-thaw cycles were measured, and the internal pore structure and mineral composition were analyzed using NMR and XRD. Subsequently, fracture tests under quasi-static loading were conducted on concrete beams in combination with the acoustic emission technique. The evolution patterns of the AE energy, AF-RA parameters, and b-value under sulfate corrosion and freeze-thaw cycles were systematically analyzed. Finally, the finite element method was employed to explore the mixed mode I-II damage scale and double-K fracture parameters. Results indicate that: (1) the coupling effect of freeze-thaw cycles and sulfate erosion exhibits a dual-mechanism behavior, characterized by initial matrix micro-densification followed by accelerated damage propagation, which ultimately culminates in significant deterioration of the fracture bearing capacity of the material. (2) with an increase in freeze-thaw cycles, the accumulated AE energy at peak load, the shear failure ratio, the critical damage scale, and the double-K fracture toughness for both mode I and mixed mode I-II cracks exhibit a consistent pattern of an initial increase followed by a subsequent decrease. (3) compared with mode I fracture, mixed mode I-II fracture exerts effects on the proportion of shear failure, critical damage scale, and cumulative AE energy, whereas it exerts a relatively minor effect on the double-K fracture parameters. (4) in contrast to water freeze-thaw environment, sulfate solution freeze-thaw induces significantly different evolutionary patterns in cumulative AE energy, AF, RA, and b-value</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105453"},"PeriodicalIF":5.6,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978844","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 : 2026-04-01Epub Date: 2026-02-04DOI: 10.1016/j.tafmec.2026.105470
Chao Wang, Kaiyun Wang, Tao Zhu, Jingke Zhang, Bing Yang, Shoune Xiao, Guangwu Yang
The surface fatigue crack growth mechanism of welded structures under random loads in service is complex, and the assessment method based on failure life lacks an effective description of the crack growth process. This study investigates the surface crack evolution mechanism in welded joints under random fatigue loading. First, a series of experiments were conducted to determine the through-thickness crack growth rate parameters of aluminum alloy butt joints. These experiments revealed the influence of thickness and stress ratio on the fatigue crack growth rate. The normalization of the growth rate of surface cracks under variable fatigue loading was achieved through the introduction of the constraint factor of surface cracks and the crack closure function(ΔKeff-da/dN). Moreover, the effect of mean stress on the crack growth threshold was considered to describe the crack growth behavior of welded joints more accurately under near-threshold conditions and at high stress ratios. Furthermore, a two-stage model for surface fatigue crack growth in welded joints under variable-amplitude loading is proposed. The random load was converted into an equivalent variable-amplitude load spectrum, enabling a dynamic calculation of the surface fatigue crack growth life. Finally, this model significantly narrows the prediction error for test fatigue life from −25% ∼ 45% under the BS7910 standard analytical method to within −15% ∼ 25%, verifying the effectiveness of the proposed life assessment method for variable-amplitude fatigue crack growth in welded joints.
{"title":"Equivalent fatigue crack growth rate model and life assessment method for the surface of welded joints under variable amplitude loading","authors":"Chao Wang, Kaiyun Wang, Tao Zhu, Jingke Zhang, Bing Yang, Shoune Xiao, Guangwu Yang","doi":"10.1016/j.tafmec.2026.105470","DOIUrl":"10.1016/j.tafmec.2026.105470","url":null,"abstract":"<div><div>The surface fatigue crack growth mechanism of welded structures under random loads in service is complex, and the assessment method based on failure life lacks an effective description of the crack growth process. This study investigates the surface crack evolution mechanism in welded joints under random fatigue loading. First, a series of experiments were conducted to determine the through-thickness crack growth rate parameters of aluminum alloy butt joints. These experiments revealed the influence of thickness and stress ratio on the fatigue crack growth rate. The normalization of the growth rate of surface cracks under variable fatigue loading was achieved through the introduction of the constraint factor of surface cracks and the crack closure function(Δ<em>K</em><sub>eff</sub>-d<em>a</em>/d<em>N</em>). Moreover, the effect of mean stress on the crack growth threshold was considered to describe the crack growth behavior of welded joints more accurately under near-threshold conditions and at high stress ratios. Furthermore, a two-stage model for surface fatigue crack growth in welded joints under variable-amplitude loading is proposed. The random load was converted into an equivalent variable-amplitude load spectrum, enabling a dynamic calculation of the surface fatigue crack growth life. Finally, this model significantly narrows the prediction error for test fatigue life from −25% ∼ 45% under the BS7910 standard analytical method to within −15% ∼ 25%, verifying the effectiveness of the proposed life assessment method for variable-amplitude fatigue crack growth in welded joints.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105470"},"PeriodicalIF":5.6,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189016","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 : 2026-04-01Epub Date: 2026-01-23DOI: 10.1016/j.tafmec.2026.105454
Zheng Ma , Hai Pu , Kangsheng Xue , Hao Zhang , Xiaoyan Liu , Gaobo Qu , Dejun Liu , Qingyu Yi
Ensuring rock mass stability is a fundamental prerequisite for the long-term safety, reliability, and sustainability of underground engineering structures. In this study, sandstone specimens containing parallel pre-existing fractures were selected as research objects. By integrating acoustic emission (AE) and digital image correlation (DIC) techniques, the mechanical response and strain localization evolution of prefabricated sandstone under uniaxial loading were systematically investigated. To quantitatively evaluate the stability characteristics, a comprehensive stability index (SI) was established based on three key parameters: the strength reduction parameter (IC), brittleness parameter (Iσ), and energy storage parameter (IU). The Analytic Hierarchy Process (AHP) was applied to determine the relative weights of these parameters, enabling quantitative comparison of sandstone stability under varying fracture geometries. The results demonstrate that the presence of multiple prefabricated fractures markedly degrades the mechanical integrity of sandstone, leading to a reduction in peak strength ranging from approximately 30% to 60%. As the flaw dip angle increases, the peak AE amplitude rises correspondingly, and the failure mode transitions from axial mixed tensile failure to oblique tensile–shear failure. With an increase in the rock bridge angle, AE activity becomes more intense, and the dominant failure mechanism shifts from shear to tensile cracking around the rock bridge zone. Specimens classified within the stable zone generally exhibited larger dip angles (approximately 75°) and rock bridge angles (greater than 90°), whereas those within the hazardous zone were characterized by lower dip angles (approximately 15°) and smaller rock bridge angles (less than or equal to 60°). For specimens with rock bridge angles greater than 90°, approximately 55.6% exhibited pronounced brittle behavior, suggesting a heightened potential for rockburst occurrence.
{"title":"Bearing stability assessment of flawed sandstone considering multi-parameter coupling and analytic hierarchy process: effects of flaw geometric configuration","authors":"Zheng Ma , Hai Pu , Kangsheng Xue , Hao Zhang , Xiaoyan Liu , Gaobo Qu , Dejun Liu , Qingyu Yi","doi":"10.1016/j.tafmec.2026.105454","DOIUrl":"10.1016/j.tafmec.2026.105454","url":null,"abstract":"<div><div>Ensuring rock mass stability is a fundamental prerequisite for the long-term safety, reliability, and sustainability of underground engineering structures. In this study, sandstone specimens containing parallel pre-existing fractures were selected as research objects. By integrating acoustic emission (AE) and digital image correlation (DIC) techniques, the mechanical response and strain localization evolution of prefabricated sandstone under uniaxial loading were systematically investigated. To quantitatively evaluate the stability characteristics, a comprehensive stability index (SI) was established based on three key parameters: the strength reduction parameter (<em>I</em><sub>C</sub>), brittleness parameter (<em>I</em><sub>σ</sub>), and energy storage parameter (<em>I</em><sub>U</sub>). The Analytic Hierarchy Process (AHP) was applied to determine the relative weights of these parameters, enabling quantitative comparison of sandstone stability under varying fracture geometries. The results demonstrate that the presence of multiple prefabricated fractures markedly degrades the mechanical integrity of sandstone, leading to a reduction in peak strength ranging from approximately 30% to 60%. As the flaw dip angle increases, the peak AE amplitude rises correspondingly, and the failure mode transitions from axial mixed tensile failure to oblique tensile–shear failure. With an increase in the rock bridge angle, AE activity becomes more intense, and the dominant failure mechanism shifts from shear to tensile cracking around the rock bridge zone. Specimens classified within the stable zone generally exhibited larger dip angles (approximately 75°) and rock bridge angles (greater than 90°), whereas those within the hazardous zone were characterized by lower dip angles (approximately 15°) and smaller rock bridge angles (less than or equal to 60°). For specimens with rock bridge angles greater than 90°, approximately 55.6% exhibited pronounced brittle behavior, suggesting a heightened potential for rockburst occurrence.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105454"},"PeriodicalIF":5.6,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189023","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 : 2026-04-01Epub Date: 2026-01-22DOI: 10.1016/j.tafmec.2026.105475
Tong Sun , Yuanqing Wang , Yongjiu Shi , Jianlei Zou
This study investigates the low-temperature fracture behavior of Q355 steel welded joints in the base metal (BM), weld metal (WM), and heat-affected zone (HAZ) over a testing temperature range from 23 °C to −100 °C. V-notch Charpy impact tests and Single-Edge Notched Bend (SENB) fracture toughness tests under different constraint conditions were conducted to obtain impact energy (KV2), J-R curves, and characteristic values (J1C and Jmax). The reference temperature T0 was evaluated using the Master Curve method, and the ductile-to-brittle transition temperature Tt was determined by Boltzmann fitting. The results show that KV2 decreases markedly with decreasing temperature in all regions, indicating a clear ductile-to-brittle transition. The BM exhibits the highest stability of low-temperature toughness, followed by the WM, while the HAZ shows the greatest scatter and the highest sensitivity to temperature reduction. For standard SENB specimens, J-R curves and J1C values remain nearly constant in the ductile regime, whereas significant differences emerge in the mixed and brittle regimes, with the BM showing the lowest T0 and the HAZ the highest. For non-standard SENB specimens, reducing crack length and specimen thickness lowers constraint levels and leads to increased fracture toughness and reduced T0. Transition temperatures Tt obtained from Charpy impact and fracture toughness tests differ significantly, with J1C providing a conservative assessment and Jmax reflecting crack-propagation resistance. Overall, the low-temperature fracture behavior of Q355 steel welded joints is strongly influenced by testing temperature, constraint condition, and material region, with the HAZ remaining the most critical zone for low-temperature fracture resistance.
{"title":"Experimental study on the toughness properties of Q355 steel welded joint considering constraint effects and low-temperature conditions","authors":"Tong Sun , Yuanqing Wang , Yongjiu Shi , Jianlei Zou","doi":"10.1016/j.tafmec.2026.105475","DOIUrl":"10.1016/j.tafmec.2026.105475","url":null,"abstract":"<div><div>This study investigates the low-temperature fracture behavior of Q355 steel welded joints in the base metal (BM), weld metal (WM), and heat-affected zone (HAZ) over a testing temperature range from 23 °C to −100 °C. V-notch Charpy impact tests and Single-Edge Notched Bend (SENB) fracture toughness tests under different constraint conditions were conducted to obtain impact energy (<em>KV</em>2), <em>J</em>-R curves, and characteristic values (<em>J</em><sub>1C</sub> and <em>J</em><sub>max</sub>). The reference temperature <em>T</em><sub>0</sub> was evaluated using the Master Curve method, and the ductile-to-brittle transition temperature <em>T</em><sub>t</sub> was determined by Boltzmann fitting. The results show that <em>KV</em>2 decreases markedly with decreasing temperature in all regions, indicating a clear ductile-to-brittle transition. The BM exhibits the highest stability of low-temperature toughness, followed by the WM, while the HAZ shows the greatest scatter and the highest sensitivity to temperature reduction. For standard SENB specimens, <em>J</em>-R curves and <em>J</em><sub>1C</sub> values remain nearly constant in the ductile regime, whereas significant differences emerge in the mixed and brittle regimes, with the BM showing the lowest <em>T</em><sub>0</sub> and the HAZ the highest. For non-standard SENB specimens, reducing crack length and specimen thickness lowers constraint levels and leads to increased fracture toughness and reduced <em>T</em><sub>0</sub>. Transition temperatures <em>T</em><sub>t</sub> obtained from Charpy impact and fracture toughness tests differ significantly, with <em>J</em><sub>1C</sub> providing a conservative assessment and <em>J</em><sub>max</sub> reflecting crack-propagation resistance. Overall, the low-temperature fracture behavior of Q355 steel welded joints is strongly influenced by testing temperature, constraint condition, and material region, with the HAZ remaining the most critical zone for low-temperature fracture resistance.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105475"},"PeriodicalIF":5.6,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189101","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 : 2026-04-01Epub Date: 2026-02-07DOI: 10.1016/j.tafmec.2026.105483
Alessandra Lingua , Antoine Sanner , François Hild , David S. Kammer
Toughening in heterogeneous lattice materials is commonly attributed to crack path tortuosity, but the relative importance of this and other mechanisms remains unclear because direct experimental evidence is scarce. Here, we introduce isolated, well-controlled defects into brittle lattice specimens and use mechanical testing with digital image correlation to track crack growth at the scale of individual cells. This approach allows us to experimentally evaluate how local imperfections influence fracture processes. We find that defects do not affect crack initiation or peak load, yet they can increase the work to failure. Crack path tortuosity contributes to this increase in some configurations but is not statistically significant in others, indicating that it is not the sole governing toughening mechanism. Instead, we observe ligament bridging, a mechanism that has not been reported experimentally in lattice materials, and find that it contributes to enhanced work to failure. These results show that targeted defects can activate toughening mechanisms beyond tortuosity, providing an additional route for designing fracture-resistant lattice materials.
{"title":"Breaking better: How defects activate multiple toughening mechanisms in lattice materials","authors":"Alessandra Lingua , Antoine Sanner , François Hild , David S. Kammer","doi":"10.1016/j.tafmec.2026.105483","DOIUrl":"10.1016/j.tafmec.2026.105483","url":null,"abstract":"<div><div>Toughening in heterogeneous lattice materials is commonly attributed to crack path tortuosity, but the relative importance of this and other mechanisms remains unclear because direct experimental evidence is scarce. Here, we introduce isolated, well-controlled defects into brittle lattice specimens and use mechanical testing with digital image correlation to track crack growth at the scale of individual cells. This approach allows us to experimentally evaluate how local imperfections influence fracture processes. We find that defects do not affect crack initiation or peak load, yet they can increase the work to failure. Crack path tortuosity contributes to this increase in some configurations but is not statistically significant in others, indicating that it is not the sole governing toughening mechanism. Instead, we observe ligament bridging, a mechanism that has not been reported experimentally in lattice materials, and find that it contributes to enhanced work to failure. These results show that targeted defects can activate toughening mechanisms beyond tortuosity, providing an additional route for designing fracture-resistant lattice materials.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105483"},"PeriodicalIF":5.6,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189093","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 : 2026-04-01Epub Date: 2026-02-06DOI: 10.1016/j.tafmec.2026.105502
Yunru Wang , Mao Zhou , Fengfei He , Wenyu Zhang , Feifei Qin , Shiming Dong
Accurately evaluating the temperature-dependent fracture toughness of rocks is essential for ensuring the long-term stability of deep underground engineering structures. However, conventional high-temperature fracture tests are operationally complex, time-consuming, and costly, which restricts their wide application in engineering design. To address these challenges, this study proposes a physics-informed Transformer framework designed to achieve high-accuracy predictions of Mode I, Mode II, and mixed-mode I–II fracture toughness under small-sample conditions. A temperature-dependent, multi-material database consisting of 120 Center-Cracked Brazilian Disk (CCBD) test cases was established for model training and validation. By embedding physically interpretable constraints into the Transformer model, the model effectively learns nonlinear couplings among input variables, enabling a synergistic integration of physical mechanisms and data-driven prediction. The proposed model maintains excellent accuracy despite limited data availability and demonstrates strong predictive performance across different temperatures and fracture modes. The results indicate that the method provides a reliable and interpretable approach for high-temperature fracture toughness prediction, offering an efficient, economical, and engineering-practical alternative in scenarios where experimental data are difficult to obtain.
{"title":"Prediction of rock fracture toughness using a physics-integrated transformer model","authors":"Yunru Wang , Mao Zhou , Fengfei He , Wenyu Zhang , Feifei Qin , Shiming Dong","doi":"10.1016/j.tafmec.2026.105502","DOIUrl":"10.1016/j.tafmec.2026.105502","url":null,"abstract":"<div><div>Accurately evaluating the temperature-dependent fracture toughness of rocks is essential for ensuring the long-term stability of deep underground engineering structures. However, conventional high-temperature fracture tests are operationally complex, time-consuming, and costly, which restricts their wide application in engineering design. To address these challenges, this study proposes a physics-informed Transformer framework designed to achieve high-accuracy predictions of Mode I, Mode II, and mixed-mode I–II fracture toughness under small-sample conditions. A temperature-dependent, multi-material database consisting of 120 Center-Cracked Brazilian Disk (CCBD) test cases was established for model training and validation. By embedding physically interpretable constraints into the Transformer model, the model effectively learns nonlinear couplings among input variables, enabling a synergistic integration of physical mechanisms and data-driven prediction. The proposed model maintains excellent accuracy despite limited data availability and demonstrates strong predictive performance across different temperatures and fracture modes. The results indicate that the method provides a reliable and interpretable approach for high-temperature fracture toughness prediction, offering an efficient, economical, and engineering-practical alternative in scenarios where experimental data are difficult to obtain.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105502"},"PeriodicalIF":5.6,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189017","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 : 2026-04-01Epub Date: 2025-12-27DOI: 10.1016/j.tafmec.2025.105422
Quanle Zou , Haolong Zheng , Chuanqi Zhu , Xiaoyan Sun , Yulin Hu
Rocks in underground engineering often undergo deformation and fracture within complex environments characterized by varying disturbance intensities, which directly impact engineering stability and disaster prevention. However, current understanding of sandstone fracture mechanisms under coupled loading rate and fracture mode remains relatively limited. Herein, three-point bending tests were conducted to thoroughly investigate the deformation and fracture characteristics of sandstone under different loading rates and fracture modes, and further reveal the corresponding mechanism. It is indicated that the peak load, elastic modulus, and fracture toughness of sandstone specimens all exhibit strong dependence on loading rate and fracture mode. Crack propagation paths are governed by the coupling of the above-mentioned two factors. Specimens exhibiting mixed fracture modes will display distinctive fracture characteristics. Furthermore, it is found that the deformation and fracture in sandstone specimens are governed by the competition between the time effects induced by loading rate and the spatial configuration of the crack. At low loading rates, the spatial configuration dominates the failure details, while high loading rates diminish these differences, promoting simplified dynamic instability failure in the specimens. These findings provide valuable insights into sandstone fracture processes and deep rock mass engineering stability assessment.
{"title":"Influence of loading rate and fracture mode on fracture characteristics of sandstone: Insights from semi-circular bending tests","authors":"Quanle Zou , Haolong Zheng , Chuanqi Zhu , Xiaoyan Sun , Yulin Hu","doi":"10.1016/j.tafmec.2025.105422","DOIUrl":"10.1016/j.tafmec.2025.105422","url":null,"abstract":"<div><div>Rocks in underground engineering often undergo deformation and fracture within complex environments characterized by varying disturbance intensities, which directly impact engineering stability and disaster prevention. However, current understanding of sandstone fracture mechanisms under coupled loading rate and fracture mode remains relatively limited. Herein, three-point bending tests were conducted to thoroughly investigate the deformation and fracture characteristics of sandstone under different loading rates and fracture modes, and further reveal the corresponding mechanism. It is indicated that the peak load, elastic modulus, and fracture toughness of sandstone specimens all exhibit strong dependence on loading rate and fracture mode. Crack propagation paths are governed by the coupling of the above-mentioned two factors. Specimens exhibiting mixed fracture modes will display distinctive fracture characteristics. Furthermore, it is found that the deformation and fracture in sandstone specimens are governed by the competition between the time effects induced by loading rate and the spatial configuration of the crack. At low loading rates, the spatial configuration dominates the failure details, while high loading rates diminish these differences, promoting simplified dynamic instability failure in the specimens. These findings provide valuable insights into sandstone fracture processes and deep rock mass engineering stability assessment.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105422"},"PeriodicalIF":5.6,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145876970","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 : 2026-04-01Epub Date: 2026-01-06DOI: 10.1016/j.tafmec.2026.105447
A. Bovsunovsky , M. Borodii , O. Bovsunovsky
Catastrophic failures of steam turbines, which occurred in the history of thermal power engineering, were caused by the long-term accumulation of fatigue damage and sudden application of dynamic torque. The dynamic torque is the result of abnormal operating modes of a turbogenerator at the connection of turbogenerator to the power network with an inaccurate synchronization, as well as at short circuit on a turbogenerator. So, this a real engineering problem. Under certain conditions, such a load causes intense torsional vibrations of the turbine shaft, sufficient for its disintegration in condition of crack presence. Given the problem, the method to estimate the critically dangerous sizes of circular, transverse and longitudinal crack, at which a short circuit on a turbogenerator will lead to the disintegration of the turbine shaft, has been created. The method was applied to estimate the critically dangerous size of crack in K-220-44-2 M and K-325-23.5 turbine shafts. It was based on the dynamic torques in the most stressed sections of the turbine shafts because of a short circuit. The crack for which the stress intensity factor reaches the fracture toughness of the rotor steel is considered as critically dangerous. It is assumed that such a crack will lead to disintegration of the shaft because of a short circuit. Using the method, the critical size of circular, transverse and longitudinal crack in K-220-44-2 M and K-325-23.5 turbine shafts were determined in a certain range of the rotor steel fracture toughness.
{"title":"Integrity conditions of К-220-44-2М and К-325-23.5 turbine shafts at a short circuit on a turbogenerator in the presence of crack","authors":"A. Bovsunovsky , M. Borodii , O. Bovsunovsky","doi":"10.1016/j.tafmec.2026.105447","DOIUrl":"10.1016/j.tafmec.2026.105447","url":null,"abstract":"<div><div>Catastrophic failures of steam turbines, which occurred in the history of thermal power engineering, were caused by the long-term accumulation of fatigue damage and sudden application of dynamic torque. The dynamic torque is the result of abnormal operating modes of a turbogenerator at the connection of turbogenerator to the power network with an inaccurate synchronization, as well as at short circuit on a turbogenerator. So, this a real engineering problem. Under certain conditions, such a load causes intense torsional vibrations of the turbine shaft, sufficient for its disintegration in condition of crack presence. Given the problem, the method to estimate the critically dangerous sizes of circular, transverse and longitudinal crack, at which a short circuit on a turbogenerator will lead to the disintegration of the turbine shaft, has been created. The method was applied to estimate the critically dangerous size of crack in K-220-44-2 M and K-325-23.5 turbine shafts. It was based on the dynamic torques in the most stressed sections of the turbine shafts because of a short circuit. The crack for which the stress intensity factor reaches the fracture toughness of the rotor steel is considered as critically dangerous. It is assumed that such a crack will lead to disintegration of the shaft because of a short circuit. Using the method, the critical size of circular, transverse and longitudinal crack in K-220-44-2 M and K-325-23.5 turbine shafts were determined in a certain range of the rotor steel fracture toughness.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105447"},"PeriodicalIF":5.6,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145940289","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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