Acta Mechanica Sinica最新文献

{"title":"Second overtone thickness-extensional vibrations in ZnO piezoelectric film bulk acoustic resonators: modified algorithm for 2D complex transcendental equations","authors":"Zinan Zhao \u0000 (,&nbsp;),&nbsp;Nian Li \u0000 (,&nbsp;),&nbsp;Feng Zhu \u0000 (,&nbsp;),&nbsp;Weiqiu Chen \u0000 (,&nbsp;)","doi":"10.1007/s10409-024-24414-x","DOIUrl":"10.1007/s10409-024-24414-x","url":null,"abstract":"<div><p>This article investigates the second overtone thickness-extensional (TE2) vibrations and associated mode-coupling behaviors in ZnO piezoelectric film bulk acoustic resonator (FBAR), utilizing its wave dispersion relation and the higher-order stress balance principle. By superimposing the general wave solutions of multiple eigenmodes within the frequency range of the TE2 mode, mode-coupling solutions for ZnO FBAR are constructed. The substitution of these mode-coupling solutions into the higher-order stress balance principle, as laterally weak boundary conditions, leads to the frequency spectrogram equation, determining the relationship between resonance frequency and plate length-to-thickness ratio. A modified algorithm that combines the bisection method and the complex modulus ratio method is developed to solve the dispersion equation and frequency spectrogram equation (namely a kind of 2D complex transcendental equations) accurately and efficiently. The obtained results indicate that the operational TE2 mode may couple to unwanted 3^rd thickness-shear, fundamental thickness-shear, and flexural modes. Moreover, the mode-coupling behaviors depend strongly on resonance frequencies and plate length-to-thickness ratio. The displacement distributions of total displacement components, alongside the main displacement components of all considered eigenmodes, clearly demonstrate the variety of coupling behaviors. According to the obtained frequency spectrograms, the desirable values of plate length-to-thickness ratio for a clean operating mode with very weak coupling intensity are determined. These findings are of vital importance for the understanding of the mode-coupling mechanism in overtone thickness-extensional FBARs, which will facilitate the structural design and optimization of FBAR devices.</p><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":7109,"journal":{"name":"Acta Mechanica Sinica","volume":"41 11","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143638189","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":"Effective thermo-mechanical properties of compliant solids with small compressible liquid inclusions","authors":"Xuechao Sun \u0000 (,&nbsp;),&nbsp;Fei Ti \u0000 (,&nbsp;),&nbsp;Feng Chen \u0000 (,&nbsp;),&nbsp;Shaobao Liu \u0000 (,&nbsp;),&nbsp;Tianjian Lu \u0000 (,&nbsp;)","doi":"10.1007/s10409-024-24575-x","DOIUrl":"10.1007/s10409-024-24575-x","url":null,"abstract":"<div><p>While liquid-filled porous materials widely exist in both natural and engineering fields, their overall thermo-mechanical behaviors are influenced by the combined effects of solid skeleton, pore-filling liquid, and pore structure. When the pores are sufficiently small (e.g., micro/nano-scale pores), surface effects also play a significant role. Accounting for surface effects and liquid compressibility, we develop a theoretical model to predict the effective thermo-mechanical properties of liquid-filled porous materials. Idealized spherical compressible liquid inclusions distributed randomly in an elastic solid matrix are considered, with two scenarios separately considered. In the first scenario, the liquid inclusions are isolated so that the liquid does not flow freely. The effective coefficient of thermal expansion (CTE) and effective bulk modulus of the two-phase material are obtained via the generalized self-consistent method. In the second scenario, the liquid inclusions are connected by microchannels. We adopt a top-down approach (the mixture theory) to establish general thermo-mechanical constitutive relations for liquid-filled porous materials with surface effects, and then use a bottom-up (micromechanics) approach to determine the coupling coefficients (effective thermo-mechanical parameters) in these constitutive relations. Results show that the presence of surface stress at the solid-liquid interface increases the effective CTE and decreases the effective bulk modulus, especially when liquid compressibility is relatively large; however, the decrease in surface stress caused by increasing temperature weakens such effect. This research not only reveals the mechanism of thermo-mechanical coupling in liquid-filled porous materials having small pores but also provides a theoretical basis for accurate prediction of their thermo-mechanical responses in complex load environments.</p><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":7109,"journal":{"name":"Acta Mechanica Sinica","volume":"41 11","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143638198","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":"Self-propulsion of a deformable ellipse with the controllable rotation through inviscid fluids","authors":"Zeyu Zhang \u0000 (,&nbsp;),&nbsp;Qi Su \u0000 (,&nbsp;),&nbsp;Ren Sun \u0000 (,&nbsp;)","doi":"10.1007/s10409-024-24398-x","DOIUrl":"10.1007/s10409-024-24398-x","url":null,"abstract":"<div><p>Self-propulsion of a deformable ellipse immersed in an unbounded inviscid fluid is discussed in order to explore the effect of the deformation and controlled rotation of the body coupled with the shift of its internal mass on the self-motion. The ellipse is capable of symmetric deformation along the two orthogonal axes and endowed with some self-regulation ability via the shift and rotation of its internal mass. From the model, the appropriate velocity potential induced by the motion of the ellipse with the deformation in an otherwise undisturbed fluid is derived, and then the equations of motion are obtained by means of integrals of the unsteady fluid pressure. The equations are utilized to explore self-translational behaviors of the ellipse through the cyclic shift of its internal mass and deformation coupled with its own controllable rotation. Analysis and numerical results show that the ellipse can break the kinematic time-reversal symmetry by properly adjusting its own rotation to coordinate with the deformation and the cyclic shift of the inner mass to meet a forward criterion, and push itself to move persistently forward without a regression at zero system momentum, exhibiting some basic serpentine movements according as the ellipse performs complete revolutions or oscillates between two extreme yaw angles during its self-motion.\u0000</p><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":7109,"journal":{"name":"Acta Mechanica Sinica","volume":"41 9","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142890420","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":"Hypergravity-induced wetting profile of high-G droplets on composite substrates","authors":"Yulin Huang \u0000 (,&nbsp;),&nbsp;Chaofeng Lü \u0000 (,&nbsp;),&nbsp;Guannan Wang \u0000 (,&nbsp;)","doi":"10.1007/s10409-024-24452-x","DOIUrl":"10.1007/s10409-024-24452-x","url":null,"abstract":"<div><p>The wetting phenomenon of composite substrates in hypergravitational environment has a huge application in electronic devices and astronaut healthcare in aerospace missions. In the present contribution, the governing equation of high-G droplets on the composite substrate is firstly established in the hypergravitational environment. Meanwhile, the apparent contact angles at the contact line between droplets and substrates with different stiffness gradients are achieved. Then, we analyze the effects of hypergravity factor and the substrate stiffness on the wetting profile of high-G droplets. By introducing the droplet volume and contact angle into the Bond number, the scaling law of the high-G droplet profile is established, and we find that the contact radius of the droplet <i>R</i> / <i>S</i>^0.5 has a linear relationship with <i>ρω</i>²<i>rl</i>²<i>S</i> / (<i>γ</i>_<i>LV</i><i>θ</i>), while the droplet height <i>H</i> / <i>S</i>^0.5 has a power-law relationship with <i>ρω</i>²<i>rl</i>²<i>S</i> / (<i>γ</i>_<i>LV</i><i>θ</i>). Finally, we explain the profiles of high-G droplets during the wetting process by illustrating energy components of the entire system and find that the substrate with positive triangular stiffness and inverted triangular stiffness show opposite evolution laws. On a substrate with inverted triangular stiffness, the gravitational potential energy is more dominant.</p><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":7109,"journal":{"name":"Acta Mechanica Sinica","volume":"41 11","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143571116","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":"Sloppiness of auto-discovered constitutive models for skeletal muscle","authors":"Wenyang Liu \u0000 (,&nbsp;),&nbsp;Jiabao Tang \u0000 (,&nbsp;),&nbsp;Yanlin Jiang \u0000 (,&nbsp;),&nbsp;Yiqi Mao \u0000 (,&nbsp;),&nbsp;Shujuan Hou \u0000 (,&nbsp;)","doi":"10.1007/s10409-024-24430-x","DOIUrl":"10.1007/s10409-024-24430-x","url":null,"abstract":"<div><p>Soft biological tissues are challenging materials for both testing and modeling. Despite the development of many constitutive models, the processing of choosing the most suitable model remains heuristic, relying significantly on personal experience and preference. Another issue is that the amount of collected experimental data is always finite. In this study, we trained a constitutive artificial neural network based on experimental data of cattle skeletal muscle tissue for the self-directed auto-discovery of constitutive models. The discovered models inherently satisfy thermodynamic consistency, material objectivity, polyconvexity, and necessary physical restrictions. Two constitutive models have been discovered by the trained neural network. Considering the constraints of finite experimental data, the generality and reliability of the auto-discovered constitutive models remain to be analyzed. Through experimental data of pig skeletal muscle tissue, we assess the goodness-of-fit and parameter identifiability of the automatically discovered constitutive models. At first glance, both auto-discovered models have excellent prediction accuracy. Further exploration from the perspective of information geometry suggests that one of the auto-discovered models is superior to the other in terms of parameter identifiability. The findings of the current work are expected to extend our understanding of auto-discovered constitutive models and offer a new perspective to advance machine learning-driven mechanics.</p><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":7109,"journal":{"name":"Acta Mechanica Sinica","volume":"41 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143645448","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":"Periodic partial slip contact of thermoelectric materials under flat punches or cylindrical punches","authors":"Yali Zhang \u0000 (,&nbsp;),&nbsp;Yueting Zhou \u0000 (,&nbsp;),&nbsp;Wenxian Yang \u0000 (,&nbsp;),&nbsp;Wenshuai Wang \u0000 (,&nbsp;),&nbsp;Shenghu Ding \u0000 (,&nbsp;)","doi":"10.1007/s10409-024-24676-x","DOIUrl":"10.1007/s10409-024-24676-x","url":null,"abstract":"<div><p>The study investigates the partial slip contact problem between thermoelectric material and periodic punches including flat and cylindrical punches under various loading conditions, including normal force, energy flux, and electric current density. When developing and enhancing thermoelectric devices intended for energy harvesting and temperature regulation, the relationship between punch geometry and thermoelectric material plays a crucial role. The periodic contact problem leads to the formation of a singular integral equation with a Hilbert kernel, distinguishing it from the traditional Cauchy kernel. It delves into the impact of the thermo-electric-mechanical coupling effect on the evolution of stick-slip zone length and contact stress during partial slip. By formulating the current nonlinear problem into a set of singular integral equations, the study identifies primary variables, including normal and tangential contact stresses, as well as slip and stick zones. The partial contact problem is further simplified by applying the Goodman approximation, enabling an iterative approach to determine the stick-slip zone, contact zone size, and stress distribution. Notably, the research reveals that factors such as the shape of the punch, the coefficient of friction, and TE parameters significantly influence stress strength and the characteristics of the stick-slip zone.</p><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":7109,"journal":{"name":"Acta Mechanica Sinica","volume":"41 11","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143638199","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 multiscale analytical model for superelastic deformation of gradient nano-grained NiTi shape memory alloys","authors":"Bo Xu \u0000 (,&nbsp;),&nbsp;Xingyu Zhou \u0000 (,&nbsp;),&nbsp;Chao Yu \u0000 (,&nbsp;)","doi":"10.1007/s10409-024-24342-x","DOIUrl":"10.1007/s10409-024-24342-x","url":null,"abstract":"<div><p>A multiscale nonlocal continuum model is proposed to describe the superelastic deformation of gradient nano-grained NiTi shape memory alloys (SMAs). At the mesoscopic scale, the polycrystalline aggregate is regarded as a composite, i.e., the grain-interior (GI) phase is assumed to be a cuboidal inclusion embedded in a matrix of grain-boundary (GB) phase. An intrinsic energetic length and a gradient energy are introduced into the Helmholtz free energy of the GI phase. The criterion of martensite transformation (MT) is derived based on the principle of virtual power and second law of thermodynamics. The hindering effect of GB on MT in GI phase is addressed. By deriving the analytical solution of the proposed model and introducing a scale transition rule, the overall and local stress-strain responses of the specimen at the macroscopic scale are obtained. The prediction capability of the proposed model is verified by comparing the analytical solution with the experiment. The influences of the distribution form for the grain size (GS) on the superelastic deformation of gradient nano-grained NiTi SMAs are further predicted and discussed. The analytical form and low computational cost of the proposed model make it an appropriate theoretical tool to design the gradient nano-grained SMAs with desired mechanical property.</p><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":7109,"journal":{"name":"Acta Mechanica Sinica","volume":"41 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143645447","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":"Highly stretchable radar absorber based on kirigami metastructures with tunable electromagnetic properties","authors":"Weimin Ding \u0000 (,&nbsp;),&nbsp;Zhong Zhang \u0000 (,&nbsp;),&nbsp;Shengyu Duan \u0000 (,&nbsp;),&nbsp;Zeang Zhao \u0000 (,&nbsp;),&nbsp;Hongshuai Lei \u0000 (,&nbsp;)","doi":"10.1007/s10409-024-24363-x","DOIUrl":"10.1007/s10409-024-24363-x","url":null,"abstract":"<div><p>The demand for lightweight and multifunctional surface structure in high-end equipment is steadily growing. The harmonization between flexibility and electromagnetic tunability has become a significant subject for stealth morphing aircraft. This paper presents a microwave absorbing structure based on the kirigami configuration, aiming at improving the conformality with the negative Poisson’s ratio characteristic and expanding the radar stealth range with tunability. A precise electromagnetic reflectivity model of the impedance surface was established by the inversion method, and an integrated optimization algorithm was employed to optimize the structural parameters based on numerical analysis. Specimens composed of thermoplastic polyurethane elastic colloids and resistive materials were prepared to assess the in-plane mechanical tensile and electromagnetic absorption performances through experimental methods. The results indicate that the original absorption band spans 6.2–11.1 GHz, shifts to 8–18 GHz with stretching at a panel rotation angle of 16°, and remains nearly constant for further stretching. The specimens adhere to complex curved surfaces well in experiments and maintain the electromagnetic absorption performance compared with flat surfaces. This research offers a valuable reference for designing electromagnetic stealth structures that are highly stretchable and adjustable.\u0000</p><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":7109,"journal":{"name":"Acta Mechanica Sinica","volume":"41 9","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142890518","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":"Vibration suppression of Timoshenko beams subjected to moving loads using an inertial nonlinear energy sink","authors":"Hao Sun \u0000 (,&nbsp;),&nbsp;Jie Chen \u0000 (,&nbsp;),&nbsp;Wei Zhang \u0000 (,&nbsp;),&nbsp;Dekun Liu \u0000 (,&nbsp;)","doi":"10.1007/s10409-024-24221-x","DOIUrl":"10.1007/s10409-024-24221-x","url":null,"abstract":"<div><p>The dynamics of beams subjected to moving loads are of practical importance since the responses caused by these loads can be greater than those under equivalent static loads in some cases. In this work, a novel inertial nonlinear energy sink (NES) is applied for the first time to achieve vibration suppression in beams under moving loads. Based on the Timoshenko beam theory, the nonlinear motion equations of a beam with an inertial NES are derived using the energy method and Lagrange equations. The Newmark-<i>β</i> method combined with the Heaviside step function is adopted to calculate the responses of the beam under moving loads of constant amplitude and harmonic excitation. The accuracy of the modelling derivation and solution methodology are validated through comparisons with results from other studies. The results demonstrate that the velocity and excitation frequency of the moving load significantly affect the response of the beam as well as the performance of the inertial NES. To enhance its effectiveness under various moving load conditions, parametric optimization is numerically performed. The optimized inertial NES can achieve good performance by efficiently reducing the maximum deflection of the beam. The findings of this study contribute to advancing the understanding and application of NESs in mitigating structural vibrations caused by moving loads.\u0000</p><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":7109,"journal":{"name":"Acta Mechanica Sinica","volume":"41 10","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142889681","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":"Vibration localization and reduction in plates via lightweight soft acoustic black hole and vibration absorbers","authors":"Jian Xue \u0000 (,&nbsp;),&nbsp;Hong-Wei Ma \u0000 (,&nbsp;),&nbsp;Li-Qun Chen \u0000 (,&nbsp;)","doi":"10.1007/s10409-024-24141-x","DOIUrl":"10.1007/s10409-024-24141-x","url":null,"abstract":"<div><p>A lightweight composite resonator, consisting of a soft material acoustic black hole (SABH) and multiple vibration absorbers, is embedded in a plate to achieve localization and absorption of low-frequency vibration energy. The combination of local and global admissible functions for displacement enhances the accuracy of the Ritz method in predicting vibration localization characteristics within the SABH domain. Utilizing soft materials for the SABH can reduce the mass and frequency of the composite resonator. Due to the lack of orthogonality between global vibration modes and localized modes, the low-frequency localized modes induced by the SABH are used to shape the initial global modes, thereby concentrating the global vibration of the plate in the SABH region. Consequently, the absorbers of the composite resonator only need to be a small fraction of the mass of the local SABH to achieve substantial vibration control of the host plate. This vibration localization strategy can significantly reduce the vibration amplitude of the host plate and enhance the effectiveness of lightweight absorbers in vibration reduction.</p></div>","PeriodicalId":7109,"journal":{"name":"Acta Mechanica Sinica","volume":"41 6","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142976546","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}