Acta Mechanica最新文献

{"title":"Coupling of shearing and size effects on thermal buckling of microbeams","authors":"Chengyun Long,&nbsp;Weichao Zhou,&nbsp;Zizheng Cai,&nbsp;Daji He,&nbsp;Bing Zhao","doi":"10.1007/s00707-024-04167-8","DOIUrl":"10.1007/s00707-024-04167-8","url":null,"abstract":"<div><p>Accurate assessment of the thermal buckling behavior of microdevices is critical for the safe and secure operation of MEMS. However, the coupling of shearing and size effects on the thermal buckling of microbeams remains elusive and needs to be clarified. Here, we propose a theoretical model for the thermal buckling of microbeams that considers both the shearing and size effects, based on the modified gradient elasticity theory combined with the Timoshenko beam model. The explicit analytical forms of the deflection, the bending angle, the shearing angle and the critical buckling temperature rise are presented. The results show that the bending angle increases with the length/thickness ratio while the shearing angle decreases. It is confirmed that the shearing effect cannot be ignored in the thermal buckling of the doubly clamped microbeams with low aspect ratio. The size effect is captured in the thermal buckling of microbeams, which shows an increase in thermoelastic strength with the size reduction. The coupling effect on thermal buckling shows a weakening of the shearing effect by the size effect as the microbeam size decreases. This work could provide a theoretical reference for the design and monitoring of microdevices operating in high temperature environments.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"236 2","pages":"729 - 743"},"PeriodicalIF":2.3,"publicationDate":"2024-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143513184","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}

{"title":"On the use of feed-forward neural networks in the context of surrogate aeroelastic simulations","authors":"Bruno A. Roccia,&nbsp;Marcelo Ruiz,&nbsp;Cristian G. Gebhardt","doi":"10.1007/s00707-024-04165-w","DOIUrl":"10.1007/s00707-024-04165-w","url":null,"abstract":"<div><p>For a few decades now, the proliferation of digital computers has driven the development of increasingly complex models to study the physical phenomena that are part of our reality. Particularly, in the field of aeronautics and renewable energy (wind), correct aeroelastic modeling is crucial for many reasons: structural and aerodynamic optimization, determining operational envelopes, and avoiding destructive aeroelastic phenomena such as divergence or flutter, among others. Furthermore, the study of systems involving multiple fields of physics (aerodynamics, structural dynamics, control, etc.) is characterized by exhibiting highly nonlinear phenomena (limit cycle oscillations, bifurcations, chaos, etc.), which are very challenging to capture with linear approximations or simplified models. In this work, we present a comprehensive statistical analysis of the performance of shallow feed-forward neural networks (FNNs) to capture supercritical Hopf bifurcations when dealing with aeroelastic flutter. The FNNs are trained by considering data sets generated by using two different aeroelastic models of increasing complexity. For the structural model, we consider a two-degree-of-freedom model consisting of an airfoil oscillating in pitch and plunge. The aerodynamic forces are accounted for by using two different flow solvers: (1) a non-compressible two-dimensional linear (but ergodic) model based on Wagner’s theory (referred as Fung’s model), which results in analytical expressions for the lift and aerodynamic moment, and (2) a two-dimensional version of the well-known unsteady vortex-lattice method (UVLM). The assessment of the resulting FNN-based models is carried out through a Monte Carlo experiment over <i>R</i> replicates. As a measure of performance, we use the mean-squared error test associated with the estimators, here the system’s response and its consistent aerodynamic coefficients. We also discuss, in detail, the behavior of FNN-based surrogate aeroelastic frameworks when they are trained with data coming from Fung-based or UVLM-based aeroelastic simulations. Furthermore, we highlight a number of challenges faced by shallow FNNs, as well as some difficulties when integrated into surrogate aeroelastic environments. Finally, we provide explanations to questions raised throughout the article and conjecture some others without a definitive answer.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"236 2","pages":"673 - 705"},"PeriodicalIF":2.3,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00707-024-04165-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143513334","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}

{"title":"Time-varying frequency characteristics of accelerated rotating functionally graded material beams under thermal shock","authors":"Luping Jiang,&nbsp;Yan Qing Wang","doi":"10.1007/s00707-024-04172-x","DOIUrl":"10.1007/s00707-024-04172-x","url":null,"abstract":"<div><p>In this paper, the time-varying frequency behavior of accelerated rotating functionally graded material (FGM) beams under thermal shock is investigated. The temperature and material properties are assumed to vary along the beam thickness direction. The transient temperature field of the rotating FGM beams under the convective heat transfer boundary condition is obtained through the one-dimensional transient heat conduction equation with temperature-dependent material properties. Based on the Timoshenko beam theory, the governing equation of the beams is obtained via Hamilton’s principle. The assumed mode method is used to calculate the time-varying natural frequency of the beams with variable speed and temperature. The present results are verified by comparison with finite element results obtained by ANSYS. Results show that considering the temperature dependence of the elastic modulus is important in analyzing time-varying natural frequencies of accelerated rotating FGM beams under thermal shock. However, the temperature dependence of Poisson’s ratio, thermal conductivity and specific heat capacity can be disregarded. Under thermal shock, temperature plays a dominant role in the natural frequencies of accelerated rotating FGM beams in the initial acceleration process, while rotational speed dominates the later acceleration process.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"236 2","pages":"707 - 728"},"PeriodicalIF":2.3,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143513333","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}

{"title":"Instability characteristics of variable stiffness composite panels under thermomechanical loadings","authors":"Satyajeet Dash,&nbsp;Tanish Dey,&nbsp;Rajesh Kumar","doi":"10.1007/s00707-024-04154-z","DOIUrl":"10.1007/s00707-024-04154-z","url":null,"abstract":"<div><p>Variable stiffness laminated composite (VSLC) structures offer significant advantages for tailoring mechanical properties. However, their stability under non-uniform thermomechanical loadings, particularly for shell panels using semi-analytical approach, remains underexplored. Most research has focused on constant stiffness laminates, leaving a gap in understanding how varying fiber orientations affect VSLC buckling behavior. Thus, the present study develops a semi-analytical model to investigate the instability characteristics of VSLC plates and shallow cylindrical shell panels under non-uniform thermomechanical loads. Initially, the pre-buckling stress distributions within the panels are evaluated by minimizing the membrane strain energy. Subsequently, a displacement-based Ritz method is employed to obtain the matrix representation of the governing equations for instability problems. Finite element calculations are also conducted using ABAQUS to verify the obtained semi-analytical results. Additionally, the study examines the effects of fiber orientation, ply sequence, geometry, and boundary conditions, showing that fiber center angle significantly enhances buckling strength.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"236 2","pages":"631 - 654"},"PeriodicalIF":2.3,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143513252","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}

{"title":"Mechanics of delaminated composite beams subjected to retarded follower force with multiple time delay","authors":"András Szekrényes","doi":"10.1007/s00707-024-04161-0","DOIUrl":"10.1007/s00707-024-04161-0","url":null,"abstract":"<div><p>In this work the problem of a delaminated composite cantilever beam subjected to a retarded periodically changing follower axial force is taken into consideration. The equation of motion is deduced based on a previous work including finite element discretization in space. On the other hand the delayed system is captured by the Chebyshev polynomials of the first kind in the time domain. The most important aspect of the model is that multiple time delay is considered, i.e., the principal period of the parametric excitation is not equal to the delay. Under these conditions the stability of the system is investigated using the Floquet theory and the unit circle criterion. The stability diagrams are determined for large number of cases focusing essentially on the effect of delamination on the stable domains. The main conclusion is that although the delamination length and thicknesswise position does not have an essential effect on the stability domains, the definite offset of the limit curves may be observed. In contrast, the relation of time delay and principal period influences substantially the shape and nature of limit curves on certain parameter planes.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"236 2","pages":"655 - 672"},"PeriodicalIF":2.3,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00707-024-04161-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143513251","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}

{"title":"Analytical results describing plane thermoelastic fields and effective thermal expansion under the assumption of temperature dependency","authors":"Kunkun Xie,&nbsp;Haopeng Song,&nbsp;Peter Schiavone,&nbsp;Cunfa Gao","doi":"10.1007/s00707-024-04160-1","DOIUrl":"10.1007/s00707-024-04160-1","url":null,"abstract":"<div><p>We apply complex variable methods to develop analytical solutions of the inhomogeneity problem in which an inhomogeneity is embedded in an infinite matrix subjected to remote uniform thermal loads. We assume a nonlinear thermoelastic constitutive relationship and study the corresponding thermoelastic field as well as the effective thermal expansion under the assumption of non-uniform thermal expansion. Numerical results reveal the significant effect of temperature-dependent properties on the distribution of thermoelastic fields. In addition, the magnitude of the effective thermal expansion is shown to have a linear relationship with a newly introduced parameter <i>K</i>, which indicates that the temperature dependency of the matrix should not be neglected under non-uniform thermal expansion.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"236 1","pages":"541 - 562"},"PeriodicalIF":2.3,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994375","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}

{"title":"Effective magneto-electro-elastic moduli for multiferroic nanofibrous composites with imperfect interface","authors":"Lihong Chang,&nbsp;Simiao Cheng,&nbsp;Jiansheng Zhang,&nbsp;Wenshuai Wang","doi":"10.1007/s00707-024-04168-7","DOIUrl":"10.1007/s00707-024-04168-7","url":null,"abstract":"<div><p>As an important class of functional materials, the multiferroic piezoelectric/piezomagnetic nanocomposites are widely used in sensors and actuators of advanced functional devices. The interface effects have become a key issue in designing and regulating the physical properties of such nanocomposites. This paper investigates the magneto-electro-elastic (MEE) responses for multiferroic fibrous nanocomposites with imperfectly bonded interface under far-field anti-plane shear and in-plane electric and magnetic loadings. On this basis, the analytical solutions of the effective MEE moduli of the multiferroic nanocomposites are obtained by using a generalized self-consistent method combined with the complex variable method. The present analytical solutions considering the nanointerface stresses and imperfect interface effect are verified by comparing with existing analytical solutions for simplified problem. Numerical analysis is conducted for different types of composite materials, and the effect of nanointerface stresses, imperfect interface parameters and volume fraction on the six components of MEE effective modulus is discussed in detail. The proposed theoretical estimation of effective moduli has certain theoretical value for the design and optimization of multiferroic nanocomposites.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"236 1","pages":"563 - 584"},"PeriodicalIF":2.3,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994434","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}

{"title":"Bending, free vibration and buckling of layered piezoelectric semiconductor nanoplates based on modified couple stress theory","authors":"Miao Zhang,&nbsp;Junhong Guo","doi":"10.1007/s00707-024-04156-x","DOIUrl":"10.1007/s00707-024-04156-x","url":null,"abstract":"<div><p>This paper presents bending deformation, free vibration and buckling behaviors of three-dimensional (3D) layered piezoelectric semiconductor (PS) nanoplates with modified couple-stress effect. Analytical solutions of the extended displacements and stresses of layered PS nanoplates of bending deformation, natural frequency of free vibration and the critical buckling load under compression are derived by using the propagator matrix method. Numerical examples are provided to show the effects of the initial carrier concentration, material length scale parameter, stacking sequence of nanoplates, thickness of nanoplates, width-to-length ratio of nanoplates and loading type on the bending deformation, vibrational response, and stability of layered PS nanoplates. The results indicate that the initial carrier concentration has a significant impact on electron concentration perturbation. An increase in material length scale parameter results in enhancement of natural frequency and critical buckling load. The present results provide a new thought for the adjustment and controlling of 3D static and dynamic behaviors in the layered PS structures.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"236 1","pages":"519 - 540"},"PeriodicalIF":2.3,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994376","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}

{"title":"On static and dynamic stability of bio-inspired composite plates under variable axial load","authors":"Nazira Mohamed,&nbsp;Mohamed A. Eltaher,&nbsp;Salwa A. Mohamed,&nbsp;Alaa A. Abdelrahman","doi":"10.1007/s00707-024-04164-x","DOIUrl":"10.1007/s00707-024-04164-x","url":null,"abstract":"<div><p>Recently, bio-inspired composite structures with helicoidal schemes and designs are used in many applications instead of the classical composite structures due to their high damage tolerance and high impact energy absorption properties. However, their static and dynamic stability under variable axial loads is not addressed. Thus, this study intends to analyze the uniaxial, biaxial buckling and vibration behaviors of bio-inspired helicoidal composite plate under variable in-plane edge load, for the first time. Based on the first order shear deformation theory (FOSDT), mathematical model of helicoidal orientation schemes of bio-inspired composite plate structure under variable in plane edge loads are presented. Six different profiles of the axial loads are included in the analysis. The governing equilibrium equations and the associated boundary conditions are deduced in detail. After that, the two-dimensional differential quadrature method (2D-DQM) is exploited to discretize the buckling problem in the space domain and convert the linear partial differential equations with variable coefficients to linear eigenvalue problem in terms of displacement field. Combining the separation of variables method and 2D-DQM to solve the linear vibration problem with variable in-plane axial load. Numerical analysis is presented to discuss effects of the fiber orientation schemes, type of axial load, boundary conditions, on the buckling loads, natural frequencies, and mode shapes of bio-inspired composite plates. The proposed methodology as well as obtained results are supportive in design and manufacturing of advanced bio-inspired composite structures which can be widely in medical, environmental as well as energy-saving technologies.</p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"236 1","pages":"499 - 518"},"PeriodicalIF":2.3,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994507","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}

{"title":"Thermal buckling response of foam core smart sandwich nanoplates with electro-elastic and magneto-strictive layers","authors":"Adem Fatih Ozalp,&nbsp;Ismail Esen","doi":"10.1007/s00707-024-04155-y","DOIUrl":"10.1007/s00707-024-04155-y","url":null,"abstract":"<div><p>This study modeled and analyzed the thermomechanical buckling behavior of smart magneto-electro-elastic (MEE) sandwich nanoplates using nonlocal elasticity, strain gradient elasticity, and higher-order plate theory. The sandwich nanoplate consists of ceramic and metal functional graded foam structure in the core layer and is composed of magneto-strictive and electro-elastic materials in the surface layers. Due to the functionally graded feature in the core layer, pure metal/metal foam, pure ceramic/ceramic foam, and metal + ceramic foam structures are modeled. The foam structure can be distributed uniformly and symmetrically throughout the thickness of the core layer. The effects of nonlocal elasticity, strain gradient elasticity, foam distribution, and foam void ratio of the core layer on the thermomechanical buckling behavior of the smart sandwich nanoplate have been examined in a broad framework. Additionally, the effects of electro-elastic and magneto-strictive material characteristics of smart surface plates on thermomechanical buckling response were examined according to the applied external electric and magnetic potential intensities. It is observed that the foam structure and foam void fraction ratio in the core layer are effective on the thermomechanical buckling behavior of the smart sandwich nanoplate. Moreover, it is concluded that the applied external electric and magnetic potential can change the thermomechanical buckling behavior of the sandwich nanoplate. </p></div>","PeriodicalId":456,"journal":{"name":"Acta Mechanica","volume":"236 1","pages":"469 - 497"},"PeriodicalIF":2.3,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142995862","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}