Pub Date : 2026-01-01Epub Date: 2025-11-06DOI: 10.1016/j.ijengsci.2025.104407
Yuntang Li, Zhitong Sun, Cong Zhang, Jie Jin, Yuan Chen, Bingqing Wang, Juan Feng
An aerostatic thrust bearing lubricated by supercritical carbon dioxide (ATB-SCO2) is ideal axial support component for the rotating shaft of an SCO2 cycle power generator. However, little literature is related to the performance analysis of an ATB-SCO2 and laminar model is commonly used, leading to significant errors in bearing performance predictions. In this article, the modified Reynolds equation based on Elrod-Ng turbulence model and orifice discharge equation are combined and solved by finite difference method for calculating the static performance of an ATB-SCO2. Moreover, the turbulence effect on ATB-SCO2 static performance is investigated by analyzing the flow field characteristics in lubricating film. The results indicate that SCO2 on thrust plate is in a turbulent state. Load capacity and stiffness calculated by turbulence model are larger while mass flow rate is lower compared to those of obtained by laminar model. The fluid velocity varies steeply near-wall and smoothly in middle of lubricating film due to the increased effective viscosity in middle of lubricating film. Load capacity and stiffness increase with the increase of supply pressure and rotational speed, and decrease with the growth of film thickness. Furthermore, the static performance of an ATB-SCO2 is significantly influenced by pressure-equalizing groove depth (when the depth is <50 µm) and restrictor number, and the effects of pressure-equalizing groove width can be neglected.
{"title":"Performance analysis of an aerostatic thrust bearing lubricated by supercritical CO2 utilizing Elrod-Ng turbulence model","authors":"Yuntang Li, Zhitong Sun, Cong Zhang, Jie Jin, Yuan Chen, Bingqing Wang, Juan Feng","doi":"10.1016/j.ijengsci.2025.104407","DOIUrl":"10.1016/j.ijengsci.2025.104407","url":null,"abstract":"<div><div>An aerostatic thrust bearing lubricated by supercritical carbon dioxide (ATB-SCO<sub>2</sub>) is ideal axial support component for the rotating shaft of an SCO<sub>2</sub> cycle power generator. However, little literature is related to the performance analysis of an ATB-SCO<sub>2</sub> and laminar model is commonly used, leading to significant errors in bearing performance predictions. In this article, the modified Reynolds equation based on Elrod-Ng turbulence model and orifice discharge equation are combined and solved by finite difference method for calculating the static performance of an ATB-SCO<sub>2</sub>. Moreover, the turbulence effect on ATB-SCO<sub>2</sub> static performance is investigated by analyzing the flow field characteristics in lubricating film. The results indicate that SCO<sub>2</sub> on thrust plate is in a turbulent state. Load capacity and stiffness calculated by turbulence model are larger while mass flow rate is lower compared to those of obtained by laminar model. The fluid velocity varies steeply near-wall and smoothly in middle of lubricating film due to the increased effective viscosity in middle of lubricating film. Load capacity and stiffness increase with the increase of supply pressure and rotational speed, and decrease with the growth of film thickness. Furthermore, the static performance of an ATB-SCO<sub>2</sub> is significantly influenced by pressure-equalizing groove depth (when the depth is <50 µm) and restrictor number, and the effects of pressure-equalizing groove width can be neglected.</div></div>","PeriodicalId":14053,"journal":{"name":"International Journal of Engineering Science","volume":"218 ","pages":"Article 104407"},"PeriodicalIF":5.7,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145463871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-01Epub Date: 2025-11-04DOI: 10.1016/j.ijengsci.2025.104403
S. El-Borgi , M. Trabelssi , N. Challamel , J.N. Reddy
This study develops a rigorous analytical framework for investigating the static bending behavior of micromorphic and nonlocal strain gradient Timoshenko beams, with particular emphasis on capturing size-dependent effects in micro- and nano-scale structural elements. The model is derived using a variational principle and it consists of a set of governing equations and boundary conditions that incorporate two distinct internal length-scales, one associated with nonlocal stress gradients and the other with strain gradient effects. The obtained system of two coupled differential equations governs the deflection and the rotation of the beam. Uncoupling both equations leads to sixth- and fifth-order differential equations for the deflection and the rotation, respectively. Exact solutions are obtained for standard boundary configurations, including simply-supported, clamped–clamped, and cantilever cases, under both point and distributed loads. The analytical model is shown to be theoretically equivalent to a class of two-length-scale nonlocal strain gradient theories, thereby offering a consistent and unified description of scale-dependent mechanics in microstructured beams. A distinct series-based solution is also constructed to verify the closed-form micromorphic results. Verification against established reference solutions demonstrates the accuracy and generality of the proposed model. A series of parametric studies is conducted to quantify the role of internal length-scales, revealing that the model successfully predicts both stiffening and softening trends, depending on the microstructural configuration. The derived exact solutions provide a reliable benchmark for assessing numerical schemes and serve as a foundation for further studies involving advanced materials with microstructural complexity.
{"title":"Static bending of micromorphic Timoshenko beams","authors":"S. El-Borgi , M. Trabelssi , N. Challamel , J.N. Reddy","doi":"10.1016/j.ijengsci.2025.104403","DOIUrl":"10.1016/j.ijengsci.2025.104403","url":null,"abstract":"<div><div>This study develops a rigorous analytical framework for investigating the static bending behavior of micromorphic and nonlocal strain gradient Timoshenko beams, with particular emphasis on capturing size-dependent effects in micro- and nano-scale structural elements. The model is derived using a variational principle and it consists of a set of governing equations and boundary conditions that incorporate two distinct internal length-scales, one associated with nonlocal stress gradients and the other with strain gradient effects. The obtained system of two coupled differential equations governs the deflection and the rotation of the beam. Uncoupling both equations leads to sixth- and fifth-order differential equations for the deflection and the rotation, respectively. Exact solutions are obtained for standard boundary configurations, including simply-supported, clamped–clamped, and cantilever cases, under both point and distributed loads. The analytical model is shown to be theoretically equivalent to a class of two-length-scale nonlocal strain gradient theories, thereby offering a consistent and unified description of scale-dependent mechanics in microstructured beams. A distinct series-based solution is also constructed to verify the closed-form micromorphic results. Verification against established reference solutions demonstrates the accuracy and generality of the proposed model. A series of parametric studies is conducted to quantify the role of internal length-scales, revealing that the model successfully predicts both stiffening and softening trends, depending on the microstructural configuration. The derived exact solutions provide a reliable benchmark for assessing numerical schemes and serve as a foundation for further studies involving advanced materials with microstructural complexity.</div></div>","PeriodicalId":14053,"journal":{"name":"International Journal of Engineering Science","volume":"218 ","pages":"Article 104403"},"PeriodicalIF":5.7,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145435048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-01Epub Date: 2025-11-03DOI: 10.1016/j.ijengsci.2025.104404
A. Vattré , Z. Zhang , E. Pan
A unified dislocation-based framework is developed for the three-dimensional analysis of internal and horizontal penny-shaped cracks embedded in multilayered transversely isotropic half-spaces. The proposed formulation covers all three classical fracture modes I, II, and III, while accounting for elastic mismatch, crack depth, and imperfect interfacial contact within arbitrary layup stacking sequences. The fundamental Green’s solutions, corresponding to the elastic response induced by continuous distributions of unit-concentrated dislocation sources, are expanded using a Fourier–Bessel series system of vector functions composed of longitudinal, gradient-type meridional, and curl-type torsional modal fields. This modal decomposition establishes a canonical correspondence between fracture modes and basis components, thereby enabling mixed-mode representations by linear superposition. The displacement field is represented by spectral Love-type expansion coefficients, where the Love numbers are computed only once. The unknown displacement discontinuity is discretized using a ring-wise collocation method and subsequently determined to satisfy the prescribed crack-face loading for each fracture mode. By means of the dual-variable and position technique, recursive layer-by-layer propagation schemes are constructed to ensure internal continuity conditions and to incorporate imperfect contact through normal and tangential interfacial springs, leading to stable and fast convergence for multilayered structures. Stress intensity factors and energy release rates are extracted by matching the near-tip asymptotic behavior of the displacement discontinuity, showing excellent agreement with benchmark reference solutions, and further extending to depth-dependent mode I, II, III, and mixed-mode fracture in layered configurations. The capabilities of the formulation are illustrated by examining titanium-based multilayer systems under mode I loading. The contrast between stiff and soft gradient-layered configurations reveals how stiffness variation and interfacial compliance modulate both stress concentration and crack-face separation. The soft gradient architecture, while producing a greater crack opening, yields a reduced normalized mode I stress intensity factor compared to the stiff layered configuration. The analysis emphasizes symmetry deviations, fracture-mode-dependent discontinuities, and the localized nature of displacement and stress fields. The results provide insight into internal fracture phenomena in coated structures, layered ceramics, and stratified functional materials, and support the design of multilayer systems with improved durability and damage tolerance.
{"title":"A spectral dislocation-based framework for 3D internal fracture in layered transversely isotropic half-spaces with imperfect interfaces","authors":"A. Vattré , Z. Zhang , E. Pan","doi":"10.1016/j.ijengsci.2025.104404","DOIUrl":"10.1016/j.ijengsci.2025.104404","url":null,"abstract":"<div><div>A unified dislocation-based framework is developed for the three-dimensional analysis of internal and horizontal penny-shaped cracks embedded in multilayered transversely isotropic half-spaces. The proposed formulation covers all three classical fracture modes I, II, and III, while accounting for elastic mismatch, crack depth, and imperfect interfacial contact within arbitrary layup stacking sequences. The fundamental Green’s solutions, corresponding to the elastic response induced by continuous distributions of unit-concentrated dislocation sources, are expanded using a Fourier–Bessel series system of vector functions composed of longitudinal, gradient-type meridional, and curl-type torsional modal fields. This modal decomposition establishes a canonical correspondence between fracture modes and basis components, thereby enabling mixed-mode representations by linear superposition. The displacement field is represented by spectral Love-type expansion coefficients, where the Love numbers are computed only once. The unknown displacement discontinuity is discretized using a ring-wise collocation method and subsequently determined to satisfy the prescribed crack-face loading for each fracture mode. By means of the dual-variable and position technique, recursive layer-by-layer propagation schemes are constructed to ensure internal continuity conditions and to incorporate imperfect contact through normal and tangential interfacial springs, leading to stable and fast convergence for multilayered structures. Stress intensity factors and energy release rates are extracted by matching the near-tip asymptotic behavior of the displacement discontinuity, showing excellent agreement with benchmark reference solutions, and further extending to depth-dependent mode I, II, III, and mixed-mode fracture in layered configurations. The capabilities of the formulation are illustrated by examining titanium-based multilayer systems under mode I loading. The contrast between stiff and soft gradient-layered configurations reveals how stiffness variation and interfacial compliance modulate both stress concentration and crack-face separation. The soft gradient architecture, while producing a greater crack opening, yields a reduced normalized mode I stress intensity factor compared to the stiff layered configuration. The analysis emphasizes symmetry deviations, fracture-mode-dependent discontinuities, and the localized nature of displacement and stress fields. The results provide insight into internal fracture phenomena in coated structures, layered ceramics, and stratified functional materials, and support the design of multilayer systems with improved durability and damage tolerance.</div></div>","PeriodicalId":14053,"journal":{"name":"International Journal of Engineering Science","volume":"218 ","pages":"Article 104404"},"PeriodicalIF":5.7,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145427962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-01Epub Date: 2025-11-06DOI: 10.1016/j.ijengsci.2025.104415
Mani Reddipaga , K. Kannan
Human brain tissue exhibits a nonlinear viscoelastic response characterised by relaxation, creep, and loading-rate dependence. Under quasi-static conditions, its elastic behaviour shows pronounced tension–compression asymmetry and greater shear stiffness in compression than in tension under combined loading. Capturing these features with fewer parameters remains a challenge. To ensure physical consistency, isotropic hyperelastic models are required to satisfy the Baker–Ericksen (B–E) inequalities. Leveraging the physical interpretation of Lode invariants, we construct a stored energy function through a priori analysis of B–E inequalities, achieving maximal tension–compression asymmetry by satisfying these inequalities. The resulting two-parameter stored energy function is benchmarked against existing models using the nonlinear shear modulus and Mooney’s asymmetry function under uniaxial deformation. Among these, the proposed model yields a correct bounded response consistent with experimental brain tissue data. The model is then extended to viscoelasticity using K.R. Rajagopal’s thermodynamic approach, where the viscoelastic constitutive equations are derived from the two scalar functions: the stored energy and the rate of dissipation. The developed stored energy is employed for both equilibrium and non-equilibrium contributions, and a simple quadratic dissipation function is chosen. Constitutive equations are derived by extremizing the rate of dissipation function subject to constraints such as incompressibility and the second law of thermodynamics. Validation against experimental data of Budday et al. (2017) shows that the proposed four-parameter model captures key mechanical features of brain tissue, including tension–compression asymmetry, hysteresis, and relaxation, while showing closer agreement than the six-parameter Budday–Ogden model for shear superposed on tension/compression deformation.
{"title":"On the construction of a viscoelastic constitutive model for brain tissue maximizing tension–compression asymmetry","authors":"Mani Reddipaga , K. Kannan","doi":"10.1016/j.ijengsci.2025.104415","DOIUrl":"10.1016/j.ijengsci.2025.104415","url":null,"abstract":"<div><div>Human brain tissue exhibits a nonlinear viscoelastic response characterised by relaxation, creep, and loading-rate dependence. Under quasi-static conditions, its elastic behaviour shows pronounced tension–compression asymmetry and greater shear stiffness in compression than in tension under combined loading. Capturing these features with fewer parameters remains a challenge. To ensure physical consistency, isotropic hyperelastic models are required to satisfy the Baker–Ericksen (B–E) inequalities. Leveraging the physical interpretation of Lode invariants, we construct a stored energy function through a priori analysis of B–E inequalities, achieving maximal tension–compression asymmetry by satisfying these inequalities. The resulting two-parameter stored energy function is benchmarked against existing models using the nonlinear shear modulus and Mooney’s asymmetry function under uniaxial deformation. Among these, the proposed model yields a correct bounded response consistent with experimental brain tissue data. The model is then extended to viscoelasticity using K.R. Rajagopal’s thermodynamic approach, where the viscoelastic constitutive equations are derived from the two scalar functions: the stored energy and the rate of dissipation. The developed stored energy is employed for both equilibrium and non-equilibrium contributions, and a simple quadratic dissipation function is chosen. Constitutive equations are derived by extremizing the rate of dissipation function subject to constraints such as incompressibility and the second law of thermodynamics. Validation against experimental data of Budday et al. (2017) shows that the proposed four-parameter model captures key mechanical features of brain tissue, including tension–compression asymmetry, hysteresis, and relaxation, while showing closer agreement than the six-parameter Budday–Ogden model for shear superposed on tension/compression deformation.</div></div>","PeriodicalId":14053,"journal":{"name":"International Journal of Engineering Science","volume":"218 ","pages":"Article 104415"},"PeriodicalIF":5.7,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145461733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-01Epub Date: 2025-11-06DOI: 10.1016/j.ijengsci.2025.104406
Ning Cao , Tongtong Liu , Xingchen Chen , Ying Wu , Xiang Li
Mechanical metamaterials have attracted extensive attention for their unconventional mechanical responses. Among them, compression-twist (CT) materials introduce new opportunities for programmable mechanical behavior. However, achieving continuous control of stiffness and Poisson’s ratio over wide ranges remains challenging. While negative Poisson’s ratio (NPR) metamaterials have been widely explored for their auxetic effects, their tunability and multi-physical performance are still limited. Here, we design four three-dimensional (3D) mechanical metamaterials—CT-NPR, CT-positive Poisson’s ratio (CT-PPR), augmented CT (ACT)-NPR, and ACT-PPR—by combining CT and NPR architectures. These structures exhibit tunable Poisson’s ratios and stiffness spanning over an extremely wide range. Numerical simulations and theoretical analysis reveal that CT-NPR and CT-PPR are bending-dominated with low stiffness, whereas ACT-NPR and ACT-PPR are stretching-dominated with high stiffness. Then, the metamaterials are fabricated via 3D printing, and their mechanical properties are characterized using quasi-static compression tests. Experimental results are consistent with theoretical predictions, confirming NPR behavior in CT-NPR and ACT-NPR, and positive Poisson’s ratio behavior in CT-PPR and ACT-PPR. Additionally, CT-PPR exhibits a distinctive two-step deformation process without self-contact, while energy absorption studies show that ACT-NPR achieves superior energy dissipation and CT-PPR maintains a stable deformation mode. This work provides a new framework for designing programmable mechanical metamaterials with potential applications in shape-morphing devices, energy absorbers, medical instruments, smart actuators, and crashworthy structures.
{"title":"Compression-twist induced 3D mechanical metamaterial with programmable mechanical properties","authors":"Ning Cao , Tongtong Liu , Xingchen Chen , Ying Wu , Xiang Li","doi":"10.1016/j.ijengsci.2025.104406","DOIUrl":"10.1016/j.ijengsci.2025.104406","url":null,"abstract":"<div><div>Mechanical metamaterials have attracted extensive attention for their unconventional mechanical responses. Among them, compression-twist (CT) materials introduce new opportunities for programmable mechanical behavior. However, achieving continuous control of stiffness and Poisson’s ratio over wide ranges remains challenging. While negative Poisson’s ratio (NPR) metamaterials have been widely explored for their auxetic effects, their tunability and multi-physical performance are still limited. Here, we design four three-dimensional (3D) mechanical metamaterials—CT-NPR, CT-positive Poisson’s ratio (CT-PPR), augmented CT (ACT)-NPR, and ACT-PPR—by combining CT and NPR architectures. These structures exhibit tunable Poisson’s ratios and stiffness spanning over an extremely wide range. Numerical simulations and theoretical analysis reveal that CT-NPR and CT-PPR are bending-dominated with low stiffness, whereas ACT-NPR and ACT-PPR are stretching-dominated with high stiffness. Then, the metamaterials are fabricated via 3D printing, and their mechanical properties are characterized using quasi-static compression tests. Experimental results are consistent with theoretical predictions, confirming NPR behavior in CT-NPR and ACT-NPR, and positive Poisson’s ratio behavior in CT-PPR and ACT-PPR. Additionally, CT-PPR exhibits a distinctive two-step deformation process without self-contact, while energy absorption studies show that ACT-NPR achieves superior energy dissipation and CT-PPR maintains a stable deformation mode. This work provides a new framework for designing programmable mechanical metamaterials with potential applications in shape-morphing devices, energy absorbers, medical instruments, smart actuators, and crashworthy structures.</div></div>","PeriodicalId":14053,"journal":{"name":"International Journal of Engineering Science","volume":"218 ","pages":"Article 104406"},"PeriodicalIF":5.7,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145448081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-01Epub Date: 2025-10-21DOI: 10.1016/j.ijengsci.2025.104397
Matteo Franzoi, Davide Bigoni, Andrea Piccolroaz
Two-dimensional architected materials are often realized as periodic grids of elastic beams. Conventional homogenization methods represent these structures as equivalent elastic solids but neglect shear deformation in the constituent beams. This article addresses this limitation by incorporating shear deformability through Timoshenko beam theory, enabling accurate modeling of stubby beams. Moreover, shearable beams with extreme mechanical characteristics can be obtained through the design of appropriate microstructures. Introducing shearable beams into the grid expands the design space, allowing, for instance, the control of the effective Poisson’s ratio beyond the limits achievable with slender beams.
{"title":"Homogenization of architected materials incorporating shearable beams","authors":"Matteo Franzoi, Davide Bigoni, Andrea Piccolroaz","doi":"10.1016/j.ijengsci.2025.104397","DOIUrl":"10.1016/j.ijengsci.2025.104397","url":null,"abstract":"<div><div>Two-dimensional architected materials are often realized as periodic grids of elastic beams. Conventional homogenization methods represent these structures as equivalent elastic solids but neglect shear deformation in the constituent beams. This article addresses this limitation by incorporating shear deformability through Timoshenko beam theory, enabling accurate modeling of stubby beams. Moreover, shearable beams with extreme mechanical characteristics can be obtained through the design of appropriate microstructures. Introducing shearable beams into the grid expands the design space, allowing, for instance, the control of the effective Poisson’s ratio beyond the limits achievable with slender beams.</div></div>","PeriodicalId":14053,"journal":{"name":"International Journal of Engineering Science","volume":"218 ","pages":"Article 104397"},"PeriodicalIF":5.7,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145360522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-12-01Epub Date: 2025-07-31DOI: 10.1016/j.ijengsci.2025.104358
Asif Equbal, Paragmoni Kalita
Hemodynamic variables are vital for understanding the progression of cardiovascular diseases, but their accuracy depends on assumptions about arterial wall behaviour. Although the left anterior descending (LAD) branch of the left coronary artery (LCA) has been reported to be highly susceptible to atherosclerosis, there is a significant lack of studies comparing the effects of different wall models in this context. This study employs two-way fluid-structure interaction (FSI) simulations to investigate the impact of rigid, elastic, and hyperelastic wall models on the hemodynamics of a moderately stenosed LAD branch in an idealised LCA. The non-Newtonian properties of blood are captured using the Carreau viscosity model. Key hemodynamic parameters—primary velocity (), streamwise vorticity, time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), and fractional flow reserve (FFR)—are evaluated across these models. Results show that the rigid model mostly exhibits higher and TAWSS at the stenosis throat compared to the elastic and hyperelastic models. It overestimates the peak TAWSS by 6.22 % and 14.46 % relative to the elastic and hyperelastic models, respectively, suggesting a higher risk of plaque rupture in rigid walls. In terms of plaque progression, both the pre- and post-stenotic regions of the arterial wall show the most extensive affected areas in the hyperelastic model compared to the rigid and elastic models, indicated by severe negative and critically low values of TAWSS, and critically high values of OSI and RRT. The FFR value is the highest for the hyperelastic model (0.95), followed by the elastic (0.94) and rigid models (0.91). These findings underscore the importance of incorporating arterial wall flexibility in hemodynamic studies to improve risk assessment and clinical accuracy.
{"title":"Effect of wall models on hemodynamics in left coronary artery: A comparative numerical study","authors":"Asif Equbal, Paragmoni Kalita","doi":"10.1016/j.ijengsci.2025.104358","DOIUrl":"10.1016/j.ijengsci.2025.104358","url":null,"abstract":"<div><div>Hemodynamic variables are vital for understanding the progression of cardiovascular diseases, but their accuracy depends on assumptions about arterial wall behaviour. Although the left anterior descending (LAD) branch of the left coronary artery (LCA) has been reported to be highly susceptible to atherosclerosis, there is a significant lack of studies comparing the effects of different wall models in this context. This study employs two-way fluid-structure interaction (FSI) simulations to investigate the impact of rigid, elastic, and hyperelastic wall models on the hemodynamics of a moderately stenosed LAD branch in an idealised LCA. The non-Newtonian properties of blood are captured using the Carreau viscosity model. Key hemodynamic parameters—primary velocity (<span><math><msub><mi>V</mi><mi>p</mi></msub></math></span>), streamwise vorticity, time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), and fractional flow reserve (FFR)—are evaluated across these models. Results show that the rigid model mostly exhibits higher <span><math><msub><mi>V</mi><mi>p</mi></msub></math></span> and TAWSS at the stenosis throat compared to the elastic and hyperelastic models. It overestimates the peak TAWSS by 6.22 % and 14.46 % relative to the elastic and hyperelastic models, respectively, suggesting a higher risk of plaque rupture in rigid walls. In terms of plaque progression, both the pre- and post-stenotic regions of the arterial wall show the most extensive affected areas in the hyperelastic model compared to the rigid and elastic models, indicated by severe negative <span><math><msub><mi>V</mi><mi>p</mi></msub></math></span>and critically low values of TAWSS, and critically high values of OSI and RRT. The FFR value is the highest for the hyperelastic model (0.95), followed by the elastic (0.94) and rigid models (0.91). These findings underscore the importance of incorporating arterial wall flexibility in hemodynamic studies to improve risk assessment and clinical accuracy.</div></div>","PeriodicalId":14053,"journal":{"name":"International Journal of Engineering Science","volume":"217 ","pages":"Article 104358"},"PeriodicalIF":5.7,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144738286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-12-01Epub Date: 2025-08-29DOI: 10.1016/j.ijengsci.2025.104376
Asghar Zajkani , Michael Khonsari
This paper presents an analytical framework for thermodynamical modeling of creep damage and fracture in materials through the lens of entropy production. Building on the second law of thermodynamics and principles of irreversible processes, the study establishes a unified coupling between a phenomenological damage law and continuum damage mechanics. The model links creep deformation to internal entropy generation and introduces a process-dependent damage exponent to ensure physically consistent and mathematically robust damage evolution. A key contribution is to introduce Creep Fracture Entropy (CFE)—a novel, material-specific thermodynamic index that serves as a reliable predictor of creep failure. By deriving time-dependent expressions for strain, strain rate, and entropy production, the model captures the full progression of creep behavior, without requiring empirical stage segmentation. The model is validated against a range of experimental data from various alloys, manifesting strong agreement with the observed strain and entropy trends. Notably, the calculated CFE values remain confined within a narrow range for each material, highlighting their intrinsic nature of constancy and reliability as fracture indicators. The thermodynamic formulation presented here enhances predictive accuracy for creep life assessment, emphasizing entropy as a pivotal damage variable in irreversible thermodynamics.
{"title":"Creep fracture entropy: A thermomechanical damage-based failure index","authors":"Asghar Zajkani , Michael Khonsari","doi":"10.1016/j.ijengsci.2025.104376","DOIUrl":"10.1016/j.ijengsci.2025.104376","url":null,"abstract":"<div><div>This paper presents an analytical framework for thermodynamical modeling of creep damage and fracture in materials through the lens of entropy production. Building on the second law of thermodynamics and principles of irreversible processes, the study establishes a unified coupling between a phenomenological damage law and continuum damage mechanics. The model links creep deformation to internal entropy generation and introduces a process-dependent damage exponent to ensure physically consistent and mathematically robust damage evolution. A key contribution is to introduce Creep Fracture Entropy (CFE)—a novel, material-specific thermodynamic index that serves as a reliable predictor of creep failure. By deriving time-dependent expressions for strain, strain rate, and entropy production, the model captures the full progression of creep behavior, without requiring empirical stage segmentation. The model is validated against a range of experimental data from various alloys, manifesting strong agreement with the observed strain and entropy trends. Notably, the calculated CFE values remain confined within a narrow range for each material, highlighting their intrinsic nature of constancy and reliability as fracture indicators. The thermodynamic formulation presented here enhances predictive accuracy for creep life assessment, emphasizing entropy as a pivotal damage variable in irreversible thermodynamics.</div></div>","PeriodicalId":14053,"journal":{"name":"International Journal of Engineering Science","volume":"217 ","pages":"Article 104376"},"PeriodicalIF":5.7,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144913286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-12-01Epub Date: 2025-09-19DOI: 10.1016/j.ijengsci.2025.104382
Markus Kaczvinszki, Wei Wu
We consider weak singular surfaces in the sense of Hadamard and Thomas. The jump condition for the velocity gradient across such singular surfaces is well established and often used in the bifurcation analysis of localized deformation. In this paper, we present the jump conditions for the Rivlin–Ericksen tensors for the first time. With regards to a material motion, the jump conditions are derived for both propagating and standing singular surfaces. We showcase the geometric structure of strain acceleration discontinuities and the additional restrictions posed by incompressibility. It turns out, for standing (i.e. material) discontinuities the jumps of all higher-order Rivlin–Ericksen tensors depend nonlinearly on the jump of the velocity gradient. This enables a simple setting for the description of discontinuities in certain non-Newtonian constitutive models.
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Pub Date : 2025-12-01Epub Date: 2025-09-21DOI: 10.1016/j.ijengsci.2025.104387
Arava R. Korakh, Lior Medina
The study presents a rigorous global stability analysis of a weakly coupled and electrostatically actuated double micro-beam structure. The analysis is conducted using a reduced-order (RO) model, from which an eigenvalue analysis is carried, to determine stable and unstable points along a given equilibrium curve, thus providing stable and unstable branches, that are differentiated by limit points. Under such an analysis, it is found that unlike classical structures, limit points will not necesserally coincide with extremum points in a given curve. In the current study, the analysis is extended to a range of parameters to create a global stability analysis, prompting global limit points maps, used to determine their evolution, as well as determine various stability thrsholds. The study is carried out in two stages. First, it is studied when the structure is mechanically loaded, solidifying the analysis paradigm while also serving as a preliminary validation tool, where a finite element (FE) model serves as the reference. The analysis then moves to study the effect of electrostatic load, where direct solutions of finite differences (FD) were used as the reference, after establishing their merit at the previous stage. It is shown that while a double micro-beam can become bistable when mechanically loaded, it will transform under electrostatic load to include hitherto unknown complex limit point maps, prompting tri-, quad- and quintstability, alongside new dynamic configurations, as well as unorthodox branch formations. It is shown that the model can project stability shifts of the structure and be used as a design tool for compact tristable actuators.
{"title":"Global limit points behaviour and multistable thresholds in electrostatically actuated double micro-beam structures","authors":"Arava R. Korakh, Lior Medina","doi":"10.1016/j.ijengsci.2025.104387","DOIUrl":"10.1016/j.ijengsci.2025.104387","url":null,"abstract":"<div><div>The study presents a rigorous global stability analysis of a weakly coupled and electrostatically actuated double micro-beam structure. The analysis is conducted using a reduced-order (RO) model, from which an eigenvalue analysis is carried, to determine stable and unstable points along a given equilibrium curve, thus providing stable and unstable branches, that are differentiated by limit points. Under such an analysis, it is found that unlike classical structures, limit points will not necesserally coincide with extremum points in a given curve. In the current study, the analysis is extended to a range of parameters to create a global stability analysis, prompting global limit points maps, used to determine their evolution, as well as determine various stability thrsholds. The study is carried out in two stages. First, it is studied when the structure is mechanically loaded, solidifying the analysis paradigm while also serving as a preliminary validation tool, where a finite element (FE) model serves as the reference. The analysis then moves to study the effect of electrostatic load, where direct solutions of finite differences (FD) were used as the reference, after establishing their merit at the previous stage. It is shown that while a double micro-beam can become bistable when mechanically loaded, it will transform under electrostatic load to include hitherto unknown complex limit point maps, prompting tri-, quad- and quintstability, alongside new dynamic configurations, as well as unorthodox branch formations. It is shown that the model can project stability shifts of the structure and be used as a design tool for compact tristable actuators.</div></div>","PeriodicalId":14053,"journal":{"name":"International Journal of Engineering Science","volume":"217 ","pages":"Article 104387"},"PeriodicalIF":5.7,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145095235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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