Pub Date : 2025-02-28DOI: 10.1016/j.eml.2025.102310
Jinguo Lin , Li Yu , Cen Chen , Tzu-Chiang Wang , Feng Liu
Recent years, microstructures are taken advantage to promote the improvement of both strength and ductility in metallic solids, or in other words to tailor the strain hardening behavior. Despite complicacy of microstructures, following the same processing protocol, it could guide as-cast samples all the way to the target structure and properties, which suggests that establishing a processing history dependent strain hardening model could be a way out for a better behavior description or even performance prediction. Based on a nonlinear transformation to strain, the common regularity of the processing history influence to metallic solids’ strain hardening behavior is uncovered, which helps us to model the processing history dependent strain hardening and its validity is confirmed by comparing with eighteen experimental data sets (66 stress-strain curves). Our theoretical model enables quantitatively describing the processing history dependence of strain hardening and even could be possibly used to characterize processing methods, which may provide insights into the strategy of evading strength–ductility trade-off.
{"title":"A unified phonon-softening-based model to uncover processing history dependent strain hardening in metallic solids","authors":"Jinguo Lin , Li Yu , Cen Chen , Tzu-Chiang Wang , Feng Liu","doi":"10.1016/j.eml.2025.102310","DOIUrl":"10.1016/j.eml.2025.102310","url":null,"abstract":"<div><div>Recent years, microstructures are taken advantage to promote the improvement of both strength and ductility in metallic solids, or in other words to tailor the strain hardening behavior. Despite complicacy of microstructures, following the same processing protocol, it could guide as-cast samples all the way to the target structure and properties, which suggests that establishing a processing history dependent strain hardening model could be a way out for a better behavior description or even performance prediction. Based on a nonlinear transformation to strain, the common regularity of the processing history influence to metallic solids’ strain hardening behavior is uncovered, which helps us to model the processing history dependent strain hardening and its validity is confirmed by comparing with eighteen experimental data sets (66 stress-strain curves). Our theoretical model enables quantitatively describing the processing history dependence of strain hardening and even could be possibly used to characterize processing methods, which may provide insights into the strategy of evading strength–ductility trade-off.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"76 ","pages":"Article 102310"},"PeriodicalIF":4.3,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143562486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-02-27DOI: 10.1016/j.eml.2025.102305
Chloé Zarader, Xin Ning
Bistable ultra-thin composite booms capable of self-deploying from coiled stable configuration to extended shape offer significant potential for lightweight deployable space structures. This paper explores the effects of ply-level thickness and angle defects on the bistable behavior of ultra-thin composite booms with circular cross-sections made from carbon fiber-reinforced epoxy (CF-Epoxy) and glass fiber-reinforced polypropylene (GF-PP) laminates. The results show that the curvatures and coiling angles are more sensitive to ply angle defects than to ply thickness imperfections. This work investigates the influence of uniform temperature variations on the bistability of the booms and the shapes of stable equilibrium states. The results suggest that the CF-Epoxy boom can maintain bistability with a wide range of temperatures, but the GF-PP boom would lose bistability in typical temperatures in space. The temperature variations have stronger effects on the coiled stable state than the extended stable shape. Furthermore, the paper investigates the combined effects of imperfections and temperature variations on the CF-Epoxy boom. Ply-level imperfections generally intensify the effects of temperature variations on the curvatures and angles of the stable states. Combined with temperature variations, ply angle imperfections still have greater effect on the curvatures than ply thickness imperfections.
{"title":"Structural effects of ply-level imperfections and extreme temperatures on bistable ultra-thin composite booms","authors":"Chloé Zarader, Xin Ning","doi":"10.1016/j.eml.2025.102305","DOIUrl":"10.1016/j.eml.2025.102305","url":null,"abstract":"<div><div>Bistable ultra-thin composite booms capable of self-deploying from coiled stable configuration to extended shape offer significant potential for lightweight deployable space structures. This paper explores the effects of ply-level thickness and angle defects on the bistable behavior of ultra-thin composite booms with circular cross-sections made from carbon fiber-reinforced epoxy (CF-Epoxy) and glass fiber-reinforced polypropylene (GF-PP) laminates. The results show that the curvatures and coiling angles are more sensitive to ply angle defects than to ply thickness imperfections. This work investigates the influence of uniform temperature variations on the bistability of the booms and the shapes of stable equilibrium states. The results suggest that the CF-Epoxy boom can maintain bistability with a wide range of temperatures, but the GF-PP boom would lose bistability in typical temperatures in space. The temperature variations have stronger effects on the coiled stable state than the extended stable shape. Furthermore, the paper investigates the combined effects of imperfections and temperature variations on the CF-Epoxy boom. Ply-level imperfections generally intensify the effects of temperature variations on the curvatures and angles of the stable states. Combined with temperature variations, ply angle imperfections still have greater effect on the curvatures than ply thickness imperfections.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"76 ","pages":"Article 102305"},"PeriodicalIF":4.3,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143548388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-27DOI: 10.1016/j.eml.2025.102302
Sathvik Sanagala, Kaushik Bhattacharya
Photomechanically active materials undergo reversible deformation on illumination, making them ideal for remote, tether-free actuation. Much of the work on these materials has focused on one-dimensional structures, such as strips. In this paper, we explore photomechanically active two-dimensional structures such as sheets and shells. When illuminated, such structures undergo spontaneous bending due to the limited penetration of light. However, the geometry of the shell constrains possible deformation modes: changes in Gauss curvature lead to in-plane stretching, against which shells are very stiff. Therefore, there is a complex coupling between the photomechanical actuation and the mechanical behavior of a shell. We develop and implement a novel approach to study photomechanically active shells. This method is a discrete shell model which captures the interplay between actuation, stretching, bending, and geometric changes. Through a series of examples, we explore these complex interactions, demonstrating how one can design shells that deform to follow the source of illumination.
{"title":"Artificial sunflower: Light-induced deformation of photoactive shells","authors":"Sathvik Sanagala, Kaushik Bhattacharya","doi":"10.1016/j.eml.2025.102302","DOIUrl":"10.1016/j.eml.2025.102302","url":null,"abstract":"<div><div>Photomechanically active materials undergo reversible deformation on illumination, making them ideal for remote, tether-free actuation. Much of the work on these materials has focused on one-dimensional structures, such as strips. In this paper, we explore photomechanically active two-dimensional structures such as sheets and shells. When illuminated, such structures undergo spontaneous bending due to the limited penetration of light. However, the geometry of the shell constrains possible deformation modes: changes in Gauss curvature lead to in-plane stretching, against which shells are very stiff. Therefore, there is a complex coupling between the photomechanical actuation and the mechanical behavior of a shell. We develop and implement a novel approach to study photomechanically active shells. This method is a discrete shell model which captures the interplay between actuation, stretching, bending, and geometric changes. Through a series of examples, we explore these complex interactions, demonstrating how one can design shells that deform to follow the source of illumination.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"76 ","pages":"Article 102302"},"PeriodicalIF":4.3,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143562487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-02-23DOI: 10.1016/j.eml.2025.102299
Md Nahid Hasan , Sharat Paul , Taylor E. Greenwood , Robert G. Parker , Yong Lin Kong , Pai Wang
We investigate the effect of a constant static bias force on the dynamically induced shape morphing of a pre-buckled bistable beam, focusing on the beam’s ability to change its vibration to be near different stable states under harmonic excitation. Our study explores four categories of oscillatory motions: switching, reverting, vacillating, and intra-well in the parameter space. We aim to achieve transitions between stable states of the pre-buckled bistable beam with minimal excitation amplitude. Our findings demonstrate the synergistic effects between dynamic excitation and static bias force, showing a broadening of the non-fractal region for switching behavior (i.e., switching from the first stable state to the second stable state) in the parameter space. This study advances the understanding of the dynamics of key structural components for multi-stable mechanical metamaterials, offering new possibilities for novel designs in adaptive applications.
{"title":"Harmonically induced shape morphing of bistable buckled beam with static bias","authors":"Md Nahid Hasan , Sharat Paul , Taylor E. Greenwood , Robert G. Parker , Yong Lin Kong , Pai Wang","doi":"10.1016/j.eml.2025.102299","DOIUrl":"10.1016/j.eml.2025.102299","url":null,"abstract":"<div><div>We investigate the effect of a constant static bias force on the dynamically induced shape morphing of a pre-buckled bistable beam, focusing on the beam’s ability to change its vibration to be near different stable states under harmonic excitation. Our study explores four categories of oscillatory motions: switching, reverting, vacillating, and intra-well in the parameter space. We aim to achieve transitions between stable states of the pre-buckled bistable beam with minimal excitation amplitude. Our findings demonstrate the synergistic effects between dynamic excitation and static bias force, showing a broadening of the non-fractal region for switching behavior (i.e., switching from the first stable state to the second stable state) in the parameter space. This study advances the understanding of the dynamics of key structural components for multi-stable mechanical metamaterials, offering new possibilities for novel designs in adaptive applications.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"76 ","pages":"Article 102299"},"PeriodicalIF":4.3,"publicationDate":"2025-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143529388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Knitted fabrics are two-dimensional-like structures formed by stitching one-dimensional yarn into three-dimensional curves. Plain stitch or stockinette stitch, one of the most fundamental knitting stitches, consists of periodic lattices of bent yarns, where three-dimensional (3D) curling behavior naturally emerges at the edges. The elasticity and geometry of knitted fabrics have been studied in previous studies, primarily based on 2D modeling. Still, the relation between 3D geometry and the mechanics of knitted fabrics has not been clarified so far. The curling behavior of knits is intricately related to the forces and moments acting on the yarns, geometry of the unit knitted loops, mechanical properties, and contacts, hence requiring a 3D analysis. Here, we show that the curling of plain knits emerges through the elasticity and geometry of the knitted loops, combining desktop-scale experiments and reduced elasticity-based simulations. We find that by changing the horizontal and vertical knitting numbers, three types of curl shapes emerge: side curl and top/bottom curl shapes, which are curled only horizontally and vertically, and double curl shape, in which both curl shapes appear together. We uncover that the knit is side-curled when the knitted loop is vertically elongated, while we observe double curl and then top/bottom curl as the loop becomes horizontally elongated. Furthermore, we find that this characteristic loop shape affects the mechanical properties of knitted fabrics. The fundamental mechanism of intricate shape deformation is clarified through the force and moment balance along yarn whose centerline shape is discretized through the B-spline curves, where elastic stretching, bending, and contact mechanics are taken into account. We reveal that the 3D structure of the single knitted loop plays a critical role in the curling behavior. Our results imply that the change in shape per a single knitted loop has the potential to control the 3D natural overall shape of knitted fabrics. The 3D curling behavior of knitted fabrics is useful for industrial applications such as composite materials, wearable devices, and actuators. Our findings could be applied in predicting or designing more complex 3D shapes made of knitted fabrics.
{"title":"Curling morphology of knitted fabrics: Structure and Mechanics","authors":"Kotone Tajiri , Riki Murakami , Shunsuke Kobayashi , Ryuichi Tarumi , Tomohiko G. Sano","doi":"10.1016/j.eml.2025.102300","DOIUrl":"10.1016/j.eml.2025.102300","url":null,"abstract":"<div><div>Knitted fabrics are two-dimensional-like structures formed by stitching one-dimensional yarn into three-dimensional curves. Plain stitch or stockinette stitch, one of the most fundamental knitting stitches, consists of periodic lattices of bent yarns, where three-dimensional (3D) curling behavior naturally emerges at the edges. The elasticity and geometry of knitted fabrics have been studied in previous studies, primarily based on 2D modeling. Still, the relation between 3D geometry and the mechanics of knitted fabrics has not been clarified so far. The curling behavior of knits is intricately related to the forces and moments acting on the yarns, geometry of the unit knitted loops, mechanical properties, and contacts, hence requiring a 3D analysis. Here, we show that the curling of plain knits emerges through the elasticity and geometry of the knitted loops, combining desktop-scale experiments and reduced elasticity-based simulations. We find that by changing the horizontal and vertical knitting numbers, three types of curl shapes emerge: side curl and top/bottom curl shapes, which are curled only horizontally and vertically, and double curl shape, in which both curl shapes appear together. We uncover that the knit is side-curled when the knitted loop is vertically elongated, while we observe double curl and then top/bottom curl as the loop becomes horizontally elongated. Furthermore, we find that this characteristic loop shape affects the mechanical properties of knitted fabrics. The fundamental mechanism of intricate shape deformation is clarified through the force and moment balance along yarn whose centerline shape is discretized through the B-spline curves, where elastic stretching, bending, and contact mechanics are taken into account. We reveal that the 3D structure of the single knitted loop plays a critical role in the curling behavior. Our results imply that the change in shape per a single knitted loop has the potential to control the 3D natural overall shape of knitted fabrics. The 3D curling behavior of knitted fabrics is useful for industrial applications such as composite materials, wearable devices, and actuators. Our findings could be applied in predicting or designing more complex 3D shapes made of knitted fabrics.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"76 ","pages":"Article 102300"},"PeriodicalIF":4.3,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-02-17DOI: 10.1016/j.eml.2025.102304
Weidong Yan , Wengen Ouyang , Ze Liu
The moiré superlattice, arising from the interlayer twisting of van der Waals (vdW) layered materials, dominates their in-plane and out-of-plane deformations, playing a pivotal role in determining the physical and mechanical properties of vdW layered materials. However, simulating the moiré superlattice-dependent mechanical behavior encounters spatiotemporal limitations from atomistic simulations. In this work, a general coarse-grained (CG) model is developed for twisted vdW layered materials, where moiré superlattices are represented as coarse particles with equivalent system energy. Comparative analysis with MD simulation results demonstrates that the developed CG model accurately reproduce the mechanical properties of vdW layered materials while capturing the influence of moiré superlattices on the out-of-plane deformation. Notably, the CG model significantly enhances computational efficiency, achieving orders of magnitude improvement depending on the twisted angle. This approach paves the way for large-scale computational simulation of twisted vdW layered materials and bridge the gap between atomistic simulations at nanoscale and experiments at micro/macroscale.
{"title":"A coarse-grained mechanical framework for twisted van der Waals layered materials","authors":"Weidong Yan , Wengen Ouyang , Ze Liu","doi":"10.1016/j.eml.2025.102304","DOIUrl":"10.1016/j.eml.2025.102304","url":null,"abstract":"<div><div>The moiré superlattice, arising from the interlayer twisting of van der Waals (vdW) layered materials, dominates their in-plane and out-of-plane deformations, playing a pivotal role in determining the physical and mechanical properties of vdW layered materials. However, simulating the moiré superlattice-dependent mechanical behavior encounters spatiotemporal limitations from atomistic simulations. In this work, a general coarse-grained (CG) model is developed for twisted vdW layered materials, where moiré superlattices are represented as coarse particles with equivalent system energy. Comparative analysis with MD simulation results demonstrates that the developed CG model accurately reproduce the mechanical properties of vdW layered materials while capturing the influence of moiré superlattices on the out-of-plane deformation. Notably, the CG model significantly enhances computational efficiency, achieving orders of magnitude improvement depending on the twisted angle. This approach paves the way for large-scale computational simulation of twisted vdW layered materials and bridge the gap between atomistic simulations at nanoscale and experiments at micro/macroscale.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"76 ","pages":"Article 102304"},"PeriodicalIF":4.3,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143463423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Implantable biomedical devices often contain rigid components such as microneedles, Si chips, and sensors, that can frequently come in physical contact with soft biological tissue. Brain-computer-interfaces (or BCIs) are an example of such devices where an array of microelectrodes is inserted in the brain to record neuronal activity, stimulate neurons for neuro-prosthetics, and treat neurodegenerative diseases. Recently, CMU Array, a customizable ultra-high-density aerosol jet (AJ) 3D nanoprinted BCI platform was developed by the authors to record action potentials from throughout the 3D volume of the brain. Although the mechanics of insertion of a single sharp needle in biological tissue has been studied, the behavior of an array is still not fully understood. In this paper, we develop a linear elastic model for insertion of multiple microneedles in close proximity with each other and determine the severity of the bed-of-nails effect, when interacting strain fields from neighboring needles fail to cause clean needle insertion into the tissue. We then carry out experiments where an array of 3D-printed and sintered microneedles (80–90 µm diameter, 1 mm long, tip radius of the order of 10 µm) are inserted in agarose, that acts as a phantom brain. We show that our model can predict the experimentally measured peak force, agarose displacement, and energy absorbed during insertion for arrays with microneedles at increasing distance from one another. We show that for our system, the microneedles in the array act completely independent of each other when they are roughly 8–10 needle diameters apart, consistent with the model predictions. This work is fundamental to the understanding of the insertion mechanics and related deformation/damage caused by rigid microscale objects implanted in various soft biological tissue.
{"title":"Bed-of-Nails effect: Unraveling the insertion behavior of aerosol jet 3D printed microneedle array in soft tissue","authors":"Sanjida Jahan , Arushi Jain , Stefano Fregonese , Chunshan Hu , Mattia Bacca , Rahul Panat","doi":"10.1016/j.eml.2025.102301","DOIUrl":"10.1016/j.eml.2025.102301","url":null,"abstract":"<div><div>Implantable biomedical devices often contain rigid components such as microneedles, Si chips, and sensors, that can frequently come in physical contact with soft biological tissue. Brain-computer-interfaces (or BCIs) are an example of such devices where an array of microelectrodes is inserted in the brain to record neuronal activity, stimulate neurons for neuro-prosthetics, and treat neurodegenerative diseases. Recently, CMU Array, a customizable ultra-high-density aerosol jet (AJ) 3D nanoprinted BCI platform was developed by the authors to record action potentials from throughout the 3D volume of the brain. Although the mechanics of insertion of a single sharp needle in biological tissue has been studied, the behavior of an array is still not fully understood. In this paper, we develop a linear elastic model for insertion of multiple microneedles in close proximity with each other and determine the severity of the bed-of-nails effect, when interacting strain fields from neighboring needles fail to cause clean needle insertion into the tissue. We then carry out experiments where an array of 3D-printed and sintered microneedles (80–90 µm diameter, 1 mm long, tip radius of the order of 10 µm) are inserted in agarose, that acts as a phantom brain. We show that our model can predict the experimentally measured peak force, agarose displacement, and energy absorbed during insertion for arrays with microneedles at increasing distance from one another. We show that for our system, the microneedles in the array act completely independent of each other when they are roughly 8–10 needle diameters apart, consistent with the model predictions. This work is fundamental to the understanding of the insertion mechanics and related deformation/damage caused by rigid microscale objects implanted in various soft biological tissue.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102301"},"PeriodicalIF":4.3,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143428821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-02-03DOI: 10.1016/j.eml.2025.102297
Lizhe Wang , Fuyuan Liu , Min Chen , Zhiyun Mao , Geng Chen , Zhichao Zhang , Zhouyi Xiang
In recent years, advanced soft computing methodologies have emerged as more effective than traditional approaches in estimating fatigue properties. However, a significant research gap remains in efficiently and accurately evaluating the multiaxial loading capacities of lattice structures and the impact of mesoscale design parameters, especially under unknown cyclic conditions during operation. To address this, we propose a data-driven methodology that integrates a multiscale shakedown evaluation method with a hybrid machine learning (HML) model. Our HML model, incorporating ensemble learning techniques and hyperparameter tuning via random search, accurately predicts the multiaxial shakedown fatigue loading capacity of a representative peanut-shaped auxetic lattice structure with parameterized geometry. The HML model's exceptional performance, demonstrated by a Normalized Root Mean Squared Error (NRMSE) of 0.018 and a coefficient of determination (R2) of 0.945, underscores its reliability, precision, and practicality. Additionally, sensitivity-based parametric analyses reveal the significant influence of center distance and edge width on the multiaxial fatigue properties of the lattice structure. This work offers an efficient tool for quantifying the contributions of various design parameters and loading conditions to multiaxial shakedown loading capacities.
{"title":"Synergizing machine learning and multiscale shakedown method for shakedown loading capacity evaluation of parameterized lattice structures","authors":"Lizhe Wang , Fuyuan Liu , Min Chen , Zhiyun Mao , Geng Chen , Zhichao Zhang , Zhouyi Xiang","doi":"10.1016/j.eml.2025.102297","DOIUrl":"10.1016/j.eml.2025.102297","url":null,"abstract":"<div><div>In recent years, advanced soft computing methodologies have emerged as more effective than traditional approaches in estimating fatigue properties. However, a significant research gap remains in efficiently and accurately evaluating the multiaxial loading capacities of lattice structures and the impact of mesoscale design parameters, especially under unknown cyclic conditions during operation. To address this, we propose a data-driven methodology that integrates a multiscale shakedown evaluation method with a hybrid machine learning (HML) model. Our HML model, incorporating ensemble learning techniques and hyperparameter tuning via random search, accurately predicts the multiaxial shakedown fatigue loading capacity of a representative peanut-shaped auxetic lattice structure with parameterized geometry. The HML model's exceptional performance, demonstrated by a Normalized Root Mean Squared Error (NRMSE) of 0.018 and a coefficient of determination (R<sup>2</sup>) of 0.945, underscores its reliability, precision, and practicality. Additionally, sensitivity-based parametric analyses reveal the significant influence of center distance and edge width on the multiaxial fatigue properties of the lattice structure. This work offers an efficient tool for quantifying the contributions of various design parameters and loading conditions to multiaxial shakedown loading capacities.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"75 ","pages":"Article 102297"},"PeriodicalIF":4.3,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143360549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-02-03DOI: 10.1016/j.eml.2025.102298
Yihang Xiao , Yimin Zeng , Binhong Liu , Ruobing Bai , Wei Hong , Canhui Yang
In engineering applications, hydrogels are often susceptible to fatigue loads, either static or dynamic. Extensive efforts have been devoted to studying dynamic fatigue facture of hydrogels, which promotes the understanding of underlying mechanisms and facilitates the design and synthesis of fatigue-fracture-resistant hydrogels under cyclic loads. In stark contrast, lifetime of hydrogels under static loading is much less investigated and hydrogels resistant to delayed fracture have not been reported. Here we propose a mechanism against delayed fracture by deconcentrating stress at crack tip through spontaneous network reconfiguration, during which reversible crosslinks dissociate to relieve stress and reassociate to reconstruct the polymer network in a stress-free manner. We validate the proposed mechanism by investigating the delayed fracture behaviors of polyacrylamide hydrogels with reversible and irreversible crosslinks. We show that a hydrogel with reversible crosslinks exhibits a threshold against delayed fracture, > 132 J/m2, one order of magnitude higher than that of its counterpart with irreversible crosslinks, ∼13 J/m2, which obeys the Lake-Thomas prediction. We provide further validations, including experimental observations on training-enhanced fracture stretch, decreased threshold for delayed fracture at a lower rate of network reconfiguration, prominent stress relaxation, as well as numerical simulations. Evidently, spontaneous network reconfiguration offers an effective way to deconcentrate stress at the crack tip for prolonged resistance to fracture.
{"title":"Prolonged fracture resistance of hydrogels through spontaneous network reconfiguration","authors":"Yihang Xiao , Yimin Zeng , Binhong Liu , Ruobing Bai , Wei Hong , Canhui Yang","doi":"10.1016/j.eml.2025.102298","DOIUrl":"10.1016/j.eml.2025.102298","url":null,"abstract":"<div><div>In engineering applications, hydrogels are often susceptible to fatigue loads, either static or dynamic. Extensive efforts have been devoted to studying dynamic fatigue facture of hydrogels, which promotes the understanding of underlying mechanisms and facilitates the design and synthesis of fatigue-fracture-resistant hydrogels under cyclic loads. In stark contrast, lifetime of hydrogels under static loading is much less investigated and hydrogels resistant to delayed fracture have not been reported. Here we propose a mechanism against delayed fracture by deconcentrating stress at crack tip through spontaneous network reconfiguration, during which reversible crosslinks dissociate to relieve stress and reassociate to reconstruct the polymer network in a stress-free manner. We validate the proposed mechanism by investigating the delayed fracture behaviors of polyacrylamide hydrogels with reversible and irreversible crosslinks. We show that a hydrogel with reversible crosslinks exhibits a threshold against delayed fracture, > 132 J/m<sup>2</sup>, one order of magnitude higher than that of its counterpart with irreversible crosslinks, ∼13 J/m<sup>2</sup>, which obeys the Lake-Thomas prediction. We provide further validations, including experimental observations on training-enhanced fracture stretch, decreased threshold for delayed fracture at a lower rate of network reconfiguration, prominent stress relaxation, as well as numerical simulations. Evidently, spontaneous network reconfiguration offers an effective way to deconcentrate stress at the crack tip for prolonged resistance to fracture.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"75 ","pages":"Article 102298"},"PeriodicalIF":4.3,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143198083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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