European Journal of Mechanics A-Solids最新文献

{"title":"Overcoming limitations of electrostatic bow snap-through in bistable microbeams via prestress tuning","authors":"Lior Medina","doi":"10.1016/j.euromechsol.2025.105802","DOIUrl":"10.1016/j.euromechsol.2025.105802","url":null,"abstract":"<div><div>A curved bistable microbeam subjected to electrostatic loading from an electrode facing its concave side may exhibit a bow snap-through (<span><math><mrow><mi>B</mi><mi>S</mi><mi>T</mi></mrow></math></span>) response, depending on the applied voltage, initial conditions, and beam geometry. However, for stress-free microbeams, achieving <span><math><mrow><mi>B</mi><mi>S</mi><mi>T</mi></mrow></math></span> has been shown to be quite challenging, since the conditions required for a successful actuation are limited. In the present work, <span><math><mrow><mi>B</mi><mi>S</mi><mi>T</mi></mrow></math></span> is studied in the presence of prestress, enabling the development of expanded necessary conditions and upper bounds for <span><math><mrow><mi>B</mi><mi>S</mi><mi>T</mi></mrow></math></span>. The conditions are derived using an undamped, single-degree-of-freedom (DoF) reduced-order (RO) model, obtained via Galerkin’s decomposition. Subsequent analysis of the acquired conditions reveals that the introduction of prestress can be leveraged to tune the behaviour of a microbeam and overcome the constraints inherent to the stress-free beam. More specifically, it is shown that compressive prestress can increase the design-initial conditions space where <span><math><mrow><mi>B</mi><mi>S</mi><mi>T</mi></mrow></math></span> can be achieved, facilitating a controlled equilibrium shift in bistable structures via bow actuation. These new insights and conditions provide practical guidelines for both researchers and engineers in designing and tuning microbeams using prestress, thus overcoming the limitations of a stress-free beam and obtain a successful <span><math><mrow><mi>B</mi><mi>S</mi><mi>T</mi></mrow></math></span>, supporting the development of efficient, nonvolatile, and low-power bistable devices.</div></div>","PeriodicalId":50483,"journal":{"name":"European Journal of Mechanics A-Solids","volume":"115 ","pages":"Article 105802"},"PeriodicalIF":4.2,"publicationDate":"2025-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144739383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A nonlocal variational principle for the converse flexoelectric effect based on simplified strain gradient elasticity","authors":"A.R. El-Dhaba","doi":"10.1016/j.euromechsol.2025.105817","DOIUrl":"10.1016/j.euromechsol.2025.105817","url":null,"abstract":"<div><div>In this paper, we investigate how displacement variations affect electrical internal state variables, including polarization, polarization gradients, and the electric field. Our analysis is based on a hypothesis initially proposed by Stratton and later refined by Landau and Lifshitz. We focus on <strong>the converse flexoelectric effect</strong> in isotropic elastic dielectric materials within the framework of the simplified strain gradient theory of elasticity. This approach, combined with the variational principle applied to the strain energy functional and the virtual work of external forces, introduces nonlinearity into the equation of motion for the mathematical model, while the electrostatic equations governing polarization and its gradient remain linear. The direct solution method cannot obtain an analytical solution in the presence of nonlinearity; therefore, we turn to the exponential reductive perturbation method (ERPT) to obtain hierarchical solutions for the problem. Three cases will be analyzed, comparing the lattice parameter of the internal structure of STO with the length scale parameter used in the mathematical model. The results will be plotted and discussed in detail.</div></div>","PeriodicalId":50483,"journal":{"name":"European Journal of Mechanics A-Solids","volume":"115 ","pages":"Article 105817"},"PeriodicalIF":4.2,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144739304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiaxial fatigue life prediction of notched components considering normal and shear energy gradient","authors":"Jumei Lu ,&nbsp;Wen Liu ,&nbsp;Jianhui Liu ,&nbsp;Youtang Li ,&nbsp;Shengchuan Wu","doi":"10.1016/j.euromechsol.2025.105812","DOIUrl":"10.1016/j.euromechsol.2025.105812","url":null,"abstract":"<div><div>Theory of critical distance (TCD) is a simple and reliable evaluation criterion. In view of the fact that the model based on energy parameters can take both stress and strain responses into account, the energy-based TCD is constructed. Meanwhile, the modified energy gradient is used to characterize the notch geometric feature effect, which integrates the notch effect and the geometric size effect. The normal/shear energy gradient is employed to correct normal/shear critical distance, and a novel approach for calculating equivalent strain energy density is presented. The critical plane gradient ratio is defined to depict the effect of shear energy and normal energy on fatigue damage. As to the analysis above, an energy-based TCD and prediction procedure of notched components are developed. The fatigue test of Q355(D) is carried out, and the existing test data of materials (En8 steel, En3B steel, C40 steel, TC4 alloy, 7050-T7451 alloy) are selected to verify the proposed model. The calculation results of the energy-TCD approach (point method and line method) are compared with other typical energy-based models (SWT model, MSWT model, Liu model, CXH model), and the proposed model obtained better precision.</div></div>","PeriodicalId":50483,"journal":{"name":"European Journal of Mechanics A-Solids","volume":"115 ","pages":"Article 105812"},"PeriodicalIF":4.2,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144722721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nonlinear dynamic analysis and optimization of sandwich plate and shell panels with auxetic core and functionally graded Zr-MgO/Al facesheets","authors":"Krishan Kumar Gupta,&nbsp;S. Pradyumna","doi":"10.1016/j.euromechsol.2025.105788","DOIUrl":"10.1016/j.euromechsol.2025.105788","url":null,"abstract":"<div><div>In the present investigation, the geometric parameters (rib thickness, inclined cell angle, vertical cell rib length, and inclined cell rib length) of auxetic honeycomb core and material parameters (volume fraction coefficient) of the functionally graded Zr-MgO/Al facesheets of the sandwich plate and shell panels are optimized for the first time. The dynamic analysis is carried out considering a higher-order shear deformation theory and employing a <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> eight-noded isoparametric element with nine degrees of freedom per node. The material properties of the functionally graded material (FGM) facesheets are graded in the thickness direction according to a basic power law distribution in terms of the volume fractions of the constituents. The artificial bee colony algorithm is used to optimize volume fraction coefficient and different parameters of the auxetic core of the sandwich panel. The mechanical properties of the original material and the geometrical features of the unit cells are used to determine the mechanical properties of the auxetic core. The equivalent elastic parameters and density of facesheets are obtained using two micromechanical models i.e., rule of mixture (RM) and Mori–Tanaka (MT) methods. The analysis is further extended to nonlinear vibration analysis of FGM sandwich plate and shell panels. Geometrical nonlinearity is taken into consideration using the von Kármán type nonlinear strain–displacement equations.</div></div>","PeriodicalId":50483,"journal":{"name":"European Journal of Mechanics A-Solids","volume":"115 ","pages":"Article 105788"},"PeriodicalIF":4.4,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficient dynamic modeling and real-time control of the planar variable-length hard-magnetic concentric tube robots","authors":"Zheng Chen,&nbsp;Hui Ren,&nbsp;Ping Zhou,&nbsp;Wei Fan","doi":"10.1016/j.euromechsol.2025.105816","DOIUrl":"10.1016/j.euromechsol.2025.105816","url":null,"abstract":"<div><div>Recently, emerging hard-magnetic concentric tube robots (HMCTR) have shown great potential in applications such as tumor-ablation surgery. However, their development is greatly limited by complex dynamics due to geometric nonlinearity from large deformations, time-varying free segment lengths, and the complexity of magnetoelastic behavior, which also makes real-time, accurate control difficult. In this work, an efficient modeling and nonlinear model predictive control (NMPC) framework is proposed for the planar variable-length HMCTRs. An efficient global angular parameterization method (GAPM) is first developed, which features pre-integrable and concise inertial forces and accurately captures the large deformations of continuum robots using only a small number of degrees of freedom. A nonlinear model predictive control (NMPC) scheme that explicitly enforces actuator limits, measurement disturbances, and minimum safety-distance constraints. Simulation results demonstrate robust trajectory tracking and safe-distance navigation under both uniform and non-uniform magnetic fields, with near-real-time performance. These findings underscore the framework's computational efficiency and control accuracy, highlighting its potential for clinical translation in HMCTR navigation and tracking.</div></div>","PeriodicalId":50483,"journal":{"name":"European Journal of Mechanics A-Solids","volume":"115 ","pages":"Article 105816"},"PeriodicalIF":4.2,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144722618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Johnson and Cook damage and flow stress model parameters of a rolled stainless steel 304 alloy","authors":"İbrahim Berk Akdoğan ,&nbsp;Kemal Davut ,&nbsp;Mustafa Güden ,&nbsp;Hacer İrem Erten ,&nbsp;Alper Taşdemirci ,&nbsp;Farshid Khosravi Maleki ,&nbsp;Mustafa Sabri Gök","doi":"10.1016/j.euromechsol.2025.105805","DOIUrl":"10.1016/j.euromechsol.2025.105805","url":null,"abstract":"<div><div>Previous studies on stainless steel 304 alloy (SS 304) have mostly focused on the stress-strain behavior as function of the volume fraction of deformation induced martensite and the applied strain and strain rate. Although equally important, the failure/fracture of this alloy has not been thoroughly investigated so far. In the present study, the Johnson and Cook (JC) damage model parameters of a rolled-SS 304 alloy, valid at a high strain rate (2900 s⁻¹), were experimentally determined and numerically validated along with the JC flow stress parameters. The tensile failure strain of the alloy decreased as the strain rate increased from 10⁻³ to 10⁻¹ s⁻¹ and to 2900 s⁻¹. Experimentally lower flow stresses at 2900 s⁻¹ than at 1x10⁻³ s⁻¹ were also found at the strains above 0.2, which was attributed to the adiabatic heating that declined the extend of the martensitic transformation at increasing strains. The determined damage and flow stress model parameters were further calibrated with the results of the numerical models of the quasi-static and high strain rate tension tests. Microscopic analyses and the hardness measurements on the untested and tested specimens confirmed the martensitic transformation and the highest hardness values were found in the specimens tested at 1x10⁻³ s⁻¹. The martensite volume fraction as function strain rate until about necking strain (homogeneous deformation) was calculated and also microscopically determined using the electron back-scatter diffraction (EBSD) for the specimens tested at different strain rates. The results indicated the highest martensite volume fraction in the specimens tested at 10⁻³ s⁻¹ (0.55–0.6) and the lowest in the specimens tested at the high strain rate (0.27–0.30). An agreement between the calculated and the EBSD determined martensite volume fractions was shown for the studied alloy.</div></div>","PeriodicalId":50483,"journal":{"name":"European Journal of Mechanics A-Solids","volume":"115 ","pages":"Article 105805"},"PeriodicalIF":4.2,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144722600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Possible cohesive fracture path leading to the rapidest failure of ductile materials under dynamic tension","authors":"Bian Xu ,&nbsp;Hongsheng Yang ,&nbsp;Zhenhua Song ,&nbsp;Fenghua Zhou ,&nbsp;Yuxuan Zheng","doi":"10.1016/j.euromechsol.2025.105811","DOIUrl":"10.1016/j.euromechsol.2025.105811","url":null,"abstract":"<div><div>Fracture velocity for a solid undergoing high-rate plastic flow with an internal fracture depends on a cohesive fracture path at a fracture point and momentum transport process from the surrounding medium to a fracture point. Assuming a more complex nonlinear relationship between fracture cohesion and fracture opening displacement, fracture evolution under different damage models, critical fracture time, Mott wave propagation distance, and analytical or numerical solutions of the average size of fragments are derived in this study. A step-like cohesive fracture path leads to the quickest fracture process, with the step stress on the fracture point being 2/3 of its strength, while maintaining constant fracture strength and energy among all conceivable cohesive fracture paths. For a wide range of loading strain rates, the damage time had a minimum value regardless of the damage evolution path selected for material failure for various damage models. Results obtained in this study based on the principle of rapidest unloading provide a reference to study the intrinsic damage mechanisms in fracture processes.</div></div>","PeriodicalId":50483,"journal":{"name":"European Journal of Mechanics A-Solids","volume":"115 ","pages":"Article 105811"},"PeriodicalIF":4.2,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144739384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electromechanical modeling of localized micro-scale piezoelectric interaction at impact site","authors":"Milad Hasani ,&nbsp;Sam Riahi ,&nbsp;Alireza Rezania","doi":"10.1016/j.euromechsol.2025.105799","DOIUrl":"10.1016/j.euromechsol.2025.105799","url":null,"abstract":"<div><div>The non-conformal contact between a moving spherical ball and a fixed piezoelectric layer results in a micro-scale contact area. This research investigates the localized micro-scale piezoelectric interaction at the contact area on the piezoelectric layer's electrical response under the impact excitation. The ball indentation causes time-variable 3D mechanical stress and electric displacement distributions around the impact site in the piezoelectric layer. In this study, an innovative semi-analytical model is developed that divides the piezoelectric layer into two zones. This technique enables 2D-axisymmetric analysis of non-axially symmetric patches, reducing computational complexity. The results indicate that a high-voltage zone appears beneath the contact area, which can significantly contribute to the piezoelectric's electrical response. For instance, under a specific impact excitation and electrical boundary condition, the peak voltage across the piezoelectric thickness reaches 600 V while the output voltage is 1 V. Validation and comparison against experimental tests and the FEM method confirm the accuracy and efficiency of this model in the prediction of piezoelectric's transient voltage signal and voltage peak applicable to energy harvesting and sensory applications. Finally, the developed model is applied in the practical optimization of an implantable energy harvester for biomedical applications.</div></div>","PeriodicalId":50483,"journal":{"name":"European Journal of Mechanics A-Solids","volume":"115 ","pages":"Article 105799"},"PeriodicalIF":4.2,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144724007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhancing the creep resistance of 3D-printed polylactic acid at varied operating temperatures by heat treatment: An experimental and numerical analysis","authors":"Siddharth Kumar ,&nbsp;Shrushti Maheshwari ,&nbsp;Arbinndo Sinha ,&nbsp;Zafar Alam ,&nbsp;Sarthak S. Singh","doi":"10.1016/j.euromechsol.2025.105813","DOIUrl":"10.1016/j.euromechsol.2025.105813","url":null,"abstract":"<div><div>Creep deformation significantly affects polymer design, especially for polylactic acid (PLA), which is prone to deformation at high temperatures. This study investigates the impact of heat treatment as a post-processing technique on the short-term creep behavior of 3D-printed PLA, emphasizing the role of increased crystallinity in improving creep resistance. PLA samples were analyzed in untreated (UT) and heat-treated (HT) states at temperatures of 75 °C and 90 °C for varying curing durations, with differential scanning calorimetry employed to measure crystallinity levels. Creep tests conducted in tensile mode at room temperature (27 °C) revealed that the PLA sample heat-treated at 90 °C for 2 h (HT90(2h)) exhibited the highest resistance to creep deformation. Further evaluations at elevated temperatures (37 °C and 47 °C) indicated that HT90(2h) had a reduced creep rate than UT, with effectiveness enhanced by a factor of 1.85 at 47 °C. Increased crystallinity inhibits chain mobility in crystalline lamella, improving stiffness and creep resistance. A nonlinear viscoelastic Burgers model was utilized to predict the creep response under varying thermal and mechanical loads, with the model parameters dependent on crystallinity, stress, and temperature. The multi-curve optimization technique in MATLAB was used to analyze loading and unloading behavior at different stresses and temperatures. The linear viscoelastic Burgers model could trace the creep data at 27 °C, while the nonlinear version captured the creep response with increasing stress at elevated temperatures. Thus, heat treatment enhances PLA's creep resistance, improving its suitability for high-temperature, long-term mechanical applications.</div></div>","PeriodicalId":50483,"journal":{"name":"European Journal of Mechanics A-Solids","volume":"115 ","pages":"Article 105813"},"PeriodicalIF":4.4,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Acoustic wave behavior in rotating functionally graded piezomagnetic media with impedance boundaries","authors":"S. Guha ,&nbsp;V. Gupta ,&nbsp;M. Biswas ,&nbsp;M. Mahanty ,&nbsp;B.P. Sarangi ,&nbsp;A. Haty ,&nbsp;S. Nain","doi":"10.1016/j.euromechsol.2025.105786","DOIUrl":"10.1016/j.euromechsol.2025.105786","url":null,"abstract":"<div><div>This study examines the reflection characteristics of coupled waves in a functionally graded piezomagnetic medium, incorporating rotational dynamics and impedance boundary conditions. A comprehensive theoretical framework is developed by integrating flexomagnetic coupling, strain gradient elasticity, micro-rotational inertia, and spatial material gradation. The surface is modeled with impedance-type boundary conditions to simulate realistic interface behaviors. A secular equation governing wave motion is derived, and the reflection characteristics of five distinct coupled wave modes are analyzed in terms of energy ratios, dispersion relations, and incidence angle variations. Numerical simulations demonstrate that both rotation and impedance boundaries significantly influence the redistribution of energy among reflected waves, while functional grading enhances anisotropic responses. The presence of rotational motion alters the dynamic coupling between wave modes, and impedance boundaries introduce partial energy absorption and phase shifts, offering refined control over wave propagation. These findings are especially relevant for designing advanced sensors, actuators, and surface acoustic wave (SAW) devices in magneto-electro-elastic systems. The study contributes a novel wave reflection framework by integrating functionally graded properties, rotational effects, and boundary impedance, offering new insights into energy transfer mechanisms under complex material and boundary conditions.</div></div>","PeriodicalId":50483,"journal":{"name":"European Journal of Mechanics A-Solids","volume":"115 ","pages":"Article 105786"},"PeriodicalIF":4.4,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704258","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}