Pub Date : 2024-09-23DOI: 10.1016/j.ijmecsci.2024.109741
Minjie Song , Shaoning Geng , Yue Qiu , Boan Xu , Yilin Wang , Ping Jiang , Yun Hu , Shixuan Li
A comprehensive understanding of the dynamic evolution of weld microstructure under external loads can provide key insights for high-performance laser welding. A novel in-situ EBSD-DIC simulation method is introduced to study the microstructure evolution of laser welded aluminum alloys under uniaxial tensile action. An advanced crystal plastic finite element model (CPFEM) is developed, which combines the real microstructure, grain orientation and grain size effects. The results show that the dislocation density in columnar grain zone is higher than that in equiaxed grain zone. The continuous accumulation of dislocations in the columnar region results in a high work-hardening rate. This high work hardening rate enhances the plastic deformation capacity of the columnar crystal region, resulting in local strain concentration. Columnar zones are more prone to fracture because the high-strain region is a potential fracture site. In addition, low Angle grain boundary (LAGBs) is one of the reasons that the dislocation density of the columnar grain zone is higher than that of equiaxed grain zone during tensile process, which is conducive to dislocation slip of columnar grains. This study is a fundamental innovation in simulating the microstructure evolution of laser welding. This marks a major breakthrough in simulating the evolution of crystallographic features such as grain orientation, microstress and strain and dislocation density under external loads. This work can further provide practical guidance for “microstructure characteristics - mechanical property regulation”.
{"title":"In-situ EBSD-DIC simulation of microstructure evolution of aluminum alloy welds","authors":"Minjie Song , Shaoning Geng , Yue Qiu , Boan Xu , Yilin Wang , Ping Jiang , Yun Hu , Shixuan Li","doi":"10.1016/j.ijmecsci.2024.109741","DOIUrl":"10.1016/j.ijmecsci.2024.109741","url":null,"abstract":"<div><div>A comprehensive understanding of the dynamic evolution of weld microstructure under external loads can provide key insights for high-performance laser welding. A novel in-situ EBSD-DIC simulation method is introduced to study the microstructure evolution of laser welded aluminum alloys under uniaxial tensile action. An advanced crystal plastic finite element model (CPFEM) is developed, which combines the real microstructure, grain orientation and grain size effects. The results show that the dislocation density in columnar grain zone is higher than that in equiaxed grain zone. The continuous accumulation of dislocations in the columnar region results in a high work-hardening rate. This high work hardening rate enhances the plastic deformation capacity of the columnar crystal region, resulting in local strain concentration. Columnar zones are more prone to fracture because the high-strain region is a potential fracture site. In addition, low Angle grain boundary (LAGBs) is one of the reasons that the dislocation density of the columnar grain zone is higher than that of equiaxed grain zone during tensile process, which is conducive to dislocation slip of columnar grains. This study is a fundamental innovation in simulating the microstructure evolution of laser welding. This marks a major breakthrough in simulating the evolution of crystallographic features such as grain orientation, microstress and strain and dislocation density under external loads. This work can further provide practical guidance for “microstructure characteristics - mechanical property regulation”.</div></div>","PeriodicalId":56287,"journal":{"name":"International Journal of Mechanical Sciences","volume":"284 ","pages":"Article 109741"},"PeriodicalIF":7.1,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142306456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-21DOI: 10.1016/j.ijmecsci.2024.109742
Weicheng Huang , Tianzhen Liu , Zhaowei Liu , Peifei Xu , Mingchao Liu , Yuzhen Chen , K. Jimmy Hsia
In this paper, we propose a novel one-dimensional (1D) discrete differential geometry (DDG)-based numerical method for geometrically nonlinear mechanics analysis (e.g., buckling and snapping) of axisymmetric shell structures. Our numerical model leverages differential geometry principles to accurately capture the complex nonlinear deformation patterns exhibited by axisymmetric shells. By discretizing the axisymmetric shell into interconnected 1D elements along the meridional direction, the in-plane stretching and out-of-bending potentials are formulated based on the geometric principles of 1D nodes and edges under the Kirchhoff–Love hypothesis, and elastic force vector and associated Hessian matrix required by equations of motion are later derived based on symbolic calculation. Through extensive validation with available theoretical solutions and finite element method (FEM) simulations in literature, our model demonstrates high accuracy in predicting the nonlinear behavior of axisymmetric shells. Importantly, compared to the classical theoretical model and three-dimensional (3D) FEM simulation, our model is highly computationally efficient, making it suitable for large-scale real-time simulations of nonlinear problems of shell structures such as instability and snap-through phenomena. Moreover, our framework can easily incorporate complex loading conditions, e.g., boundary nonlinear contact and multi-physics actuation, which play an essential role in the use of engineering applications, such as soft robots and flexible devices. This study demonstrates that the simplicity and effectiveness of the 1D discrete differential geometry-based approach render it a powerful tool for engineers and researchers interested in nonlinear mechanics analysis of axisymmetric shells, with potential applications in various engineering fields.
{"title":"Discrete differential geometry-based model for nonlinear analysis of axisymmetric shells","authors":"Weicheng Huang , Tianzhen Liu , Zhaowei Liu , Peifei Xu , Mingchao Liu , Yuzhen Chen , K. Jimmy Hsia","doi":"10.1016/j.ijmecsci.2024.109742","DOIUrl":"10.1016/j.ijmecsci.2024.109742","url":null,"abstract":"<div><div>In this paper, we propose a novel one-dimensional (1D) discrete differential geometry (DDG)-based numerical method for geometrically nonlinear mechanics analysis (e.g., buckling and snapping) of axisymmetric shell structures. Our numerical model leverages differential geometry principles to accurately capture the complex nonlinear deformation patterns exhibited by axisymmetric shells. By discretizing the axisymmetric shell into interconnected 1D elements along the meridional direction, the in-plane stretching and out-of-bending potentials are formulated based on the geometric principles of 1D nodes and edges under the Kirchhoff–Love hypothesis, and elastic force vector and associated Hessian matrix required by equations of motion are later derived based on symbolic calculation. Through extensive validation with available theoretical solutions and finite element method (FEM) simulations in literature, our model demonstrates high accuracy in predicting the nonlinear behavior of axisymmetric shells. Importantly, compared to the classical theoretical model and three-dimensional (3D) FEM simulation, our model is highly computationally efficient, making it suitable for large-scale real-time simulations of nonlinear problems of shell structures such as instability and snap-through phenomena. Moreover, our framework can easily incorporate complex loading conditions, e.g., boundary nonlinear contact and multi-physics actuation, which play an essential role in the use of engineering applications, such as soft robots and flexible devices. This study demonstrates that the simplicity and effectiveness of the 1D discrete differential geometry-based approach render it a powerful tool for engineers and researchers interested in nonlinear mechanics analysis of axisymmetric shells, with potential applications in various engineering fields.</div></div>","PeriodicalId":56287,"journal":{"name":"International Journal of Mechanical Sciences","volume":"283 ","pages":"Article 109742"},"PeriodicalIF":7.1,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142327464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2024-09-21DOI: 10.1016/j.ijmecsci.2024.109748
Zinan Zhao , Nian Li , Yilin Qu , Weiqiu Chen
<div><div>The method of frequency spectrum quantitative prediction (FSQP) is extended to investigate high-frequency and mode-coupling vibrations of piezoelectric film bulk acoustic resonators (FBARs) subject to initial stress-strain biasing fields for the first time. In numerical examples, we explore the cases of uniaxial compressive and tensile initial stresses along the in-plane and thickness directions, respectively. Derived from the nonlinear electroelastic theory, the governing and constitutive equations for piezoelectric films under complex stress-strain biasing states are formulated. Based on these formulations, the first step of the FSQP involves obtaining exact dispersion curves of bulk waves propagating in FBARs with different stress-strain biasing fields through the classical displacement method. Subsequently, mode-coupling solutions of physical fields are constructed for the prestressed FBARs operating with the thickness-extensional mode by superimposing relevant eigenmodes in dispersion curves. The second step of the FSQP involves deriving Hamilton's principle of piezoelectric film with initial stress-strain biasing fields using the perturbation method. Finally, the frequency spectrograms describing coupling vibration intensities between the thickness-extensional mode and unwanted eigenmodes are obtained by substituting mode-coupling solutions into Hamilton's principle, which verifies the effectiveness of the extended FSQP method for addressing dynamic problems in FBARs with biasing fields. The influences of both the amplitudes and orientations of initial stresses on the frequency spectral curves are examined. Mode-shape diagrams and displacement distributions of mutually coupled eigenmodes are presented to illustrate diverse mode-coupling behaviors in thickness-extensional FBARs under complex stress-strain biasing states. Numerical results indicate that the stress-strain biasing fields significantly affect the electromechanical properties of piezoelectric films, including effective elastic, piezoelectric, and dielectric constants. Consequently, these stress-strain biasing states exert substantial changes in frequencies and propagation wavenumbers of various mode branches within frequency ranges of the thickness-extensional mode branch. Furthermore, due to changes in propagation wavenumber, frequency spectral curves experience remarkable horizontal shifts along the length-to-thickness ratio axis, significantly altering mode-coupling behaviors of FBARs. Induced initial strains can enhance shift amplitudes of frequency spectral curves caused by initial stresses. In addition, stress-strain biasing fields result in significant shifts of frequency spectral curves along the frequency axis through the strain-stiffening or -softening effect, which can be harnessed to modulate resonance frequencies of FBARs. This study offers a solid foundation for frequency tunability, mode-coupling control, and structural designs in FBAR devices with residu
{"title":"Coupled vibrations of thickness-extensional FBARs under stress-strain biasing state","authors":"Zinan Zhao , Nian Li , Yilin Qu , Weiqiu Chen","doi":"10.1016/j.ijmecsci.2024.109748","DOIUrl":"10.1016/j.ijmecsci.2024.109748","url":null,"abstract":"<div><div>The method of frequency spectrum quantitative prediction (FSQP) is extended to investigate high-frequency and mode-coupling vibrations of piezoelectric film bulk acoustic resonators (FBARs) subject to initial stress-strain biasing fields for the first time. In numerical examples, we explore the cases of uniaxial compressive and tensile initial stresses along the in-plane and thickness directions, respectively. Derived from the nonlinear electroelastic theory, the governing and constitutive equations for piezoelectric films under complex stress-strain biasing states are formulated. Based on these formulations, the first step of the FSQP involves obtaining exact dispersion curves of bulk waves propagating in FBARs with different stress-strain biasing fields through the classical displacement method. Subsequently, mode-coupling solutions of physical fields are constructed for the prestressed FBARs operating with the thickness-extensional mode by superimposing relevant eigenmodes in dispersion curves. The second step of the FSQP involves deriving Hamilton's principle of piezoelectric film with initial stress-strain biasing fields using the perturbation method. Finally, the frequency spectrograms describing coupling vibration intensities between the thickness-extensional mode and unwanted eigenmodes are obtained by substituting mode-coupling solutions into Hamilton's principle, which verifies the effectiveness of the extended FSQP method for addressing dynamic problems in FBARs with biasing fields. The influences of both the amplitudes and orientations of initial stresses on the frequency spectral curves are examined. Mode-shape diagrams and displacement distributions of mutually coupled eigenmodes are presented to illustrate diverse mode-coupling behaviors in thickness-extensional FBARs under complex stress-strain biasing states. Numerical results indicate that the stress-strain biasing fields significantly affect the electromechanical properties of piezoelectric films, including effective elastic, piezoelectric, and dielectric constants. Consequently, these stress-strain biasing states exert substantial changes in frequencies and propagation wavenumbers of various mode branches within frequency ranges of the thickness-extensional mode branch. Furthermore, due to changes in propagation wavenumber, frequency spectral curves experience remarkable horizontal shifts along the length-to-thickness ratio axis, significantly altering mode-coupling behaviors of FBARs. Induced initial strains can enhance shift amplitudes of frequency spectral curves caused by initial stresses. In addition, stress-strain biasing fields result in significant shifts of frequency spectral curves along the frequency axis through the strain-stiffening or -softening effect, which can be harnessed to modulate resonance frequencies of FBARs. This study offers a solid foundation for frequency tunability, mode-coupling control, and structural designs in FBAR devices with residu","PeriodicalId":56287,"journal":{"name":"International Journal of Mechanical Sciences","volume":"284 ","pages":"Article 109748"},"PeriodicalIF":7.1,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-21DOI: 10.1016/j.ijmecsci.2024.109732
Francisco Javier Ramírez-Gil , Emilio Carlos Nelli Silva , Wilfredo Montealegre-Rubio
This paper presents a novel approach for designing functionally graded porous structures (FGPSs) at a macroscopic scale, where the main goal is to maximize their stiffness when subjected to time varying loads. Topology optimization is used to achieve the complex task of designing the size, shape, and distribution of pores in porous structures. We employ a local volume constraint that smoothly varies in space, leading to the formation of a graded structure consisting of varying sizes and shapes of solid and empty regions. Further constraints, such as global volume and static compliance, are incorporated into the optimization framework to improve the results. The modified solid isotropic material with penalization (SIMP) model is applied to interpolate the material properties. The design variables are filtered, and the projection technique is employed to obtain black-and-white topologies. The method of moving asymptotes (MMA) solves the optimization problem, which is a gradient-based algorithm. Sensitivities are computed using the adjoint variable method (AVM) within the discretize-then-differentiate strategy. The linear elastodynamic problem resulting from the transient finite element analysis (FEA) is solved with the implicit Newmark- scheme. Several numerical examples are provided to demonstrate the effectiveness of the proposed approach in producing multiple closed- and open-cell composite foams tailored to specific design criteria. The optimized FGPSs have the potential to fulfill the requirements for both lightweight and energy absorption in applications subjected to dynamic loads, such as those found in the automotive, aerospace and biomedical industries.
{"title":"Design of topology-optimized functionally graded porous structures under transient loads","authors":"Francisco Javier Ramírez-Gil , Emilio Carlos Nelli Silva , Wilfredo Montealegre-Rubio","doi":"10.1016/j.ijmecsci.2024.109732","DOIUrl":"10.1016/j.ijmecsci.2024.109732","url":null,"abstract":"<div><div>This paper presents a novel approach for designing functionally graded porous structures (FGPSs) at a macroscopic scale, where the main goal is to maximize their stiffness when subjected to time varying loads. Topology optimization is used to achieve the complex task of designing the size, shape, and distribution of pores in porous structures. We employ a local volume constraint that smoothly varies in space, leading to the formation of a graded structure consisting of varying sizes and shapes of solid and empty regions. Further constraints, such as global volume and static compliance, are incorporated into the optimization framework to improve the results. The modified solid isotropic material with penalization (SIMP) model is applied to interpolate the material properties. The design variables are filtered, and the projection technique is employed to obtain black-and-white topologies. The method of moving asymptotes (MMA) solves the optimization problem, which is a gradient-based algorithm. Sensitivities are computed using the adjoint variable method (AVM) within the discretize-then-differentiate strategy. The linear elastodynamic problem resulting from the transient finite element analysis (FEA) is solved with the implicit Newmark-<span><math><mi>β</mi></math></span> scheme. Several numerical examples are provided to demonstrate the effectiveness of the proposed approach in producing multiple closed- and open-cell composite foams tailored to specific design criteria. The optimized FGPSs have the potential to fulfill the requirements for both lightweight and energy absorption in applications subjected to dynamic loads, such as those found in the automotive, aerospace and biomedical industries.</div></div>","PeriodicalId":56287,"journal":{"name":"International Journal of Mechanical Sciences","volume":"284 ","pages":"Article 109732"},"PeriodicalIF":7.1,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-20DOI: 10.1016/j.ijmecsci.2024.109745
Andrzej Baczmański , Sebastian Wroński , Manuel François , Léa Le Joncour , Benoit Panicaud , Chedly Braham , Aleksandra Ludwik , Krzysztof Wierzbanowski , Vincent Klosek
In this work, a novel method for determination of the stress tensor for groups of grains having preferred texture orientations and Critical Resolved Shear Stresses (CRSSs) necessary for activation of slip systems was applied to study the elastic-plastic properties of textured duplex steel. The methodology is based on in situ neutron diffraction measurements of lattice strains for groups of grains in the ferritic and austenitic phases during tensile test.
Using the stress tensors determined for selected grains, the evolution of the Resolved Shear Stress (RSS) was analysed. As a result, for the first time CRSS values for slip systems activated in both phases of duplex steels have been determined directly from experimental data. The important advantage of the used novel methodology is that the grain stress tensor and CRSSs were determined for representative volumes of polycrystalline grains, without the use of any elastic-plastic models. It was found that, due to the heat treatment of the material, the ferritic phase is significantly harder than the austenitic phase, leading to high yield stress value for the steel under study. For the first time, the evolution of the stress tensor and RSS for austenitic grains with different orientations was determined experimentally and the different mechanical behaviour of these grains was demonstrated.
Finally, the experimental data were compared with the multi-scale Elastic-Plastic Self-Consistent (EPSC) model, which used experimental CRSSs as input data. The agreement of the predicted grain stress and macroscopic stress-strain relationship with the experimental results obtained from the tensile test positively verified the Eshelby-type grain interaction used in the EPSC model. Determining representative CRSS values from the experiment for two-phase textured material, as done for the first time in this work, reduces the number of input parameters of mechanical multiscale models by increasing their unambiguity and allowing their verification.
{"title":"Study of grain stresses and crystallographic slips in duplex steel using neutron diffraction","authors":"Andrzej Baczmański , Sebastian Wroński , Manuel François , Léa Le Joncour , Benoit Panicaud , Chedly Braham , Aleksandra Ludwik , Krzysztof Wierzbanowski , Vincent Klosek","doi":"10.1016/j.ijmecsci.2024.109745","DOIUrl":"10.1016/j.ijmecsci.2024.109745","url":null,"abstract":"<div><div>In this work, a novel method for determination of the stress tensor for groups of grains having preferred texture orientations and Critical Resolved Shear Stresses (CRSSs) necessary for activation of slip systems was applied to study the elastic-plastic properties of textured duplex steel. The methodology is based on in situ neutron diffraction measurements of lattice strains for groups of grains in the ferritic and austenitic phases during tensile test.</div><div>Using the stress tensors determined for selected grains, the evolution of the Resolved Shear Stress (RSS) was analysed. As a result, for the first time CRSS values for slip systems activated in both phases of duplex steels have been determined directly from experimental data. The important advantage of the used novel methodology is that the grain stress tensor and CRSSs were determined for representative volumes of polycrystalline grains, without the use of any elastic-plastic models. It was found that, due to the heat treatment of the material, the ferritic phase is significantly harder than the austenitic phase, leading to high yield stress value for the steel under study. For the first time, the evolution of the stress tensor and RSS for austenitic grains with different orientations was determined experimentally and the different mechanical behaviour of these grains was demonstrated.</div><div>Finally, the experimental data were compared with the multi-scale Elastic-Plastic Self-Consistent (EPSC) model, which used experimental CRSSs as input data. The agreement of the predicted grain stress and macroscopic stress-strain relationship with the experimental results obtained from the tensile test positively verified the Eshelby-type grain interaction used in the EPSC model. Determining representative CRSS values from the experiment for two-phase textured material, as done for the first time in this work, reduces the number of input parameters of mechanical multiscale models by increasing their unambiguity and allowing their verification.</div></div>","PeriodicalId":56287,"journal":{"name":"International Journal of Mechanical Sciences","volume":"283 ","pages":"Article 109745"},"PeriodicalIF":7.1,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2024-09-19DOI: 10.1016/j.ijmecsci.2024.109744
Chang-Chun Lee, Yen-Hung Lin, Dei-Pei Yang
The growth of the semiconductor industry is driven by the demand for electronic products and high transistor density. However, complex manufacturing processes generate residual stress and result in wafer warpage. Therefore, mastering wafer warpage has become a crucial challenge. This study proposes a process-oriented simulation methodology with simulation-based equivalent material method to overcome the difficulty of finite element modeling and the substantial amount of computation time. Three different methodologies, including volume percentage, representative volume element, and Timoshenko bi-material approach, are discussed due to the estimation of residual stress for equivalent material. In addition, each methodology is validated through process-oriented simulations and comparison with measurement data. The Timoshenko bi-material approach is efficient in predicting warpage in the back end of line (BEOL) interconnects and provides a comprehensive understanding of the warpage variation that occurs during different stages of BEOL.
{"title":"Stress-induced warpage estimation of advanced semiconductor copper interconnect processes","authors":"Chang-Chun Lee, Yen-Hung Lin, Dei-Pei Yang","doi":"10.1016/j.ijmecsci.2024.109744","DOIUrl":"10.1016/j.ijmecsci.2024.109744","url":null,"abstract":"<div><div>The growth of the semiconductor industry is driven by the demand for electronic products and high transistor density. However, complex manufacturing processes generate residual stress and result in wafer warpage. Therefore, mastering wafer warpage has become a crucial challenge. This study proposes a process-oriented simulation methodology with simulation-based equivalent material method to overcome the difficulty of finite element modeling and the substantial amount of computation time. Three different methodologies, including volume percentage, representative volume element, and Timoshenko bi-material approach, are discussed due to the estimation of residual stress for equivalent material. In addition, each methodology is validated through process-oriented simulations and comparison with measurement data. The Timoshenko bi-material approach is efficient in predicting warpage in the back end of line (BEOL) interconnects and provides a comprehensive understanding of the warpage variation that occurs during different stages of BEOL.</div></div>","PeriodicalId":56287,"journal":{"name":"International Journal of Mechanical Sciences","volume":"284 ","pages":"Article 109744"},"PeriodicalIF":7.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142318861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-19DOI: 10.1016/j.ijmecsci.2024.109740
Hang Li, Chuanli Yu, Zhaohe Dai
This work considers the adhesion of a thin, prestressed elastic plate to the bottom of a microcavity – a scenario that can be found frequently in thin-film devices from pressure sensors to microfluidics. This adhesion phenomenon is also referred to as stiction in the field of nano/microelectromechanical systems (N/MEMS); the geometry we consider is axisymmetric (thereby we term this problem axisymmetric stiction). Motivated by the extreme thinness of increasingly exploited nanofilms such as 2D materials in functional devices, various limiting regimes of the axisymmetric stiction problem that arise due to the interplay of the bending, stretching, and pretension effects are discussed. Specifically, key dimensionless physical parameters in this problem are discussed and the range of these parameters for the classification of different regimes is outlined. This classification allows for analytical/asymptotic solutions for the critical adhesion conditions and the adhesion length in different regimes, many of which are not yet available in the literature. These analytical results are verified numerically and also compared with experiments based on 3-500 nm thick 2D materials. As such, this work provides a complete overview of the physically relevant regimes associated with axisymmetric stiction, establishing a regime diagram that can be directed used for the evaluation of the structural reliability of rapidly emerging thin plate devices.
{"title":"Regimes in the axisymmetric stiction of thin elastic plates","authors":"Hang Li, Chuanli Yu, Zhaohe Dai","doi":"10.1016/j.ijmecsci.2024.109740","DOIUrl":"10.1016/j.ijmecsci.2024.109740","url":null,"abstract":"<div><div>This work considers the adhesion of a thin, prestressed elastic plate to the bottom of a microcavity – a scenario that can be found frequently in thin-film devices from pressure sensors to microfluidics. This adhesion phenomenon is also referred to as stiction in the field of nano/microelectromechanical systems (N/MEMS); the geometry we consider is axisymmetric (thereby we term this problem <em>axisymmetric stiction</em>). Motivated by the extreme thinness of increasingly exploited nanofilms such as 2D materials in functional devices, various limiting regimes of the axisymmetric stiction problem that arise due to the interplay of the bending, stretching, and pretension effects are discussed. Specifically, key dimensionless physical parameters in this problem are discussed and the range of these parameters for the classification of different regimes is outlined. This classification allows for analytical/asymptotic solutions for the critical adhesion conditions and the adhesion length in different regimes, many of which are not yet available in the literature. These analytical results are verified numerically and also compared with experiments based on 3-500 nm thick 2D materials. As such, this work provides a complete overview of the physically relevant regimes associated with axisymmetric stiction, establishing a regime diagram that can be directed used for the evaluation of the structural reliability of rapidly emerging thin plate devices.</div></div>","PeriodicalId":56287,"journal":{"name":"International Journal of Mechanical Sciences","volume":"284 ","pages":"Article 109740"},"PeriodicalIF":7.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-19DOI: 10.1016/j.ijmecsci.2024.109737
Niklas Bönisch, Jakob C. Schilling, Christian Mittelstedt
This paper presents a semi-analytical analysis approach for the determination of stress fields in the vicinity of skin-stringer junctions in stiffened composite panels. The situation considered in this paper is representative for a typical stiffened panel in a modern composite aircraft fuselage. The analysis method employs a two-tier approach employing a global model based on CLPT on the one hand, and a local approach on the other hand in the form of a layerwise displacement formulation. This allows for the detailed computation of the stress concentrations in the vicinity of the skin-stringer junction. The layerwise formulation utilizes a discretization of the laminate layers into mathematical layers. The principle of the minimum of the total elastic potential yields the governing equations of the given problem, and an exponential approach leads to a quadratic eigenvalue problem that can be solved numerically. The analysis method shows excellent accuracy of the stress results in comparison with comparative finite element computations at a fraction of the computational time and effort that is required for numerical analyses.
{"title":"Stress fields at skin-stringer junctions in composite aircraft fuselages","authors":"Niklas Bönisch, Jakob C. Schilling, Christian Mittelstedt","doi":"10.1016/j.ijmecsci.2024.109737","DOIUrl":"10.1016/j.ijmecsci.2024.109737","url":null,"abstract":"<div><div>This paper presents a semi-analytical analysis approach for the determination of stress fields in the vicinity of skin-stringer junctions in stiffened composite panels. The situation considered in this paper is representative for a typical stiffened panel in a modern composite aircraft fuselage. The analysis method employs a two-tier approach employing a global model based on CLPT on the one hand, and a local approach on the other hand in the form of a layerwise displacement formulation. This allows for the detailed computation of the stress concentrations in the vicinity of the skin-stringer junction. The layerwise formulation utilizes a discretization of the laminate layers into mathematical layers. The principle of the minimum of the total elastic potential yields the governing equations of the given problem, and an exponential approach leads to a quadratic eigenvalue problem that can be solved numerically. The analysis method shows excellent accuracy of the stress results in comparison with comparative finite element computations at a fraction of the computational time and effort that is required for numerical analyses.</div></div>","PeriodicalId":56287,"journal":{"name":"International Journal of Mechanical Sciences","volume":"284 ","pages":"Article 109737"},"PeriodicalIF":7.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0020740324007781/pdfft?md5=fb41720f3d68d147a12e8b0f425073cb&pid=1-s2.0-S0020740324007781-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142306457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2024-09-19DOI: 10.1016/j.ijmecsci.2024.109736
Byung Hun An, Jin Woo Lee
A deep-learning-based generative design method is proposed to improve the frequency-dependent characteristics of a reactive silencer, and it has been validated both numerically and experimentally. The noise attenuation performance of the reactive silencer is evaluated with its transmission loss (TL), which varies with frequency and strongly depends on the partition layout inside the reactive silencer. The artificial neural network model for the generative design of the reactive silencer consists of three subnetwork models: the generator, predictor, and converter. The generator model created numerous partition layouts, and their TL curves were estimated using the predictor model. A converter model was developed to identify the frequency-dependent characteristics of the TL curves in a low-dimensional latent space. The latent space was extensively investigated to successfully select the optimal partition layouts satisfying given design requirements, including the target shape of the TL curve and its averaged target TL value. The effectiveness of the proposed method was demonstrated by applying it to three reactive silencer design problems with different design requirements. Among the three optimal silencers, one was physically investigated, and its noise attenuation performance was validated with an acoustic experiment. Because the artificial neural network model of the proposed method was developed for a normalized silencer and requires no prior knowledge of acoustics, it can be easily applied to reduce duct noise in the industry.
{"title":"Deep-learning-based generative design for optimal reactive silencers","authors":"Byung Hun An, Jin Woo Lee","doi":"10.1016/j.ijmecsci.2024.109736","DOIUrl":"10.1016/j.ijmecsci.2024.109736","url":null,"abstract":"<div><div>A deep-learning-based generative design method is proposed to improve the frequency-dependent characteristics of a reactive silencer, and it has been validated both numerically and experimentally. The noise attenuation performance of the reactive silencer is evaluated with its transmission loss (TL), which varies with frequency and strongly depends on the partition layout inside the reactive silencer. The artificial neural network model for the generative design of the reactive silencer consists of three subnetwork models: the generator, predictor, and converter. The generator model created numerous partition layouts, and their TL curves were estimated using the predictor model. A converter model was developed to identify the frequency-dependent characteristics of the TL curves in a low-dimensional latent space. The latent space was extensively investigated to successfully select the optimal partition layouts satisfying given design requirements, including the target shape of the TL curve and its averaged target TL value. The effectiveness of the proposed method was demonstrated by applying it to three reactive silencer design problems with different design requirements. Among the three optimal silencers, one was physically investigated, and its noise attenuation performance was validated with an acoustic experiment. Because the artificial neural network model of the proposed method was developed for a normalized silencer and requires no prior knowledge of acoustics, it can be easily applied to reduce duct noise in the industry.</div></div>","PeriodicalId":56287,"journal":{"name":"International Journal of Mechanical Sciences","volume":"284 ","pages":"Article 109736"},"PeriodicalIF":7.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142318860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-19DOI: 10.1016/j.ijmecsci.2024.109735
Yang Liu , Yuuki Oda , Kazuki Sasahara
This paper introduces a novel method for shape and topology optimization based on a generalized approach for evaluating topological derivatives, which are essential for the integration of shape and topology optimization. Traditionally, evaluating these derivatives presents significant mathematical challenges due to the discontinuity introduced by the insertion of a hole within the domain of interest. To overcome this issue, the study employs Helmholtz-type partial differential equations (PDEs) to construct a filtered objective functional. This approach ensures differentiability across the material and void phases and continuity over the fixed design domain while maintaining the same evaluation value as the original objective functional. By considering differentiability, continuity conditions, and the relationship between shape and topological derivatives during asymptotic analysis, generalized topological derivatives are obtained through established mathematical procedures. These topological derivatives exhibit a direct correlation with the PDE solutions and demonstrate satisfactory smoothness, thereby facilitating refined shapes in optimization strategies. Furthermore, an effective shape update algorithm is proposed, which directly integrates topological derivatives into structural optimization problems, simplifying their implementation and improving efficiency. Finally, the efficacy of the proposed methodology is demonstrated through its application to various optimal design problems, including stiffness maximization, compliant mechanisms, and eigenfrequency maximization. Verification results further highlight its potential to enhance existing methods for addressing more practical and complex optimization challenges.
{"title":"Shape and topology optimization method with generalized topological derivatives","authors":"Yang Liu , Yuuki Oda , Kazuki Sasahara","doi":"10.1016/j.ijmecsci.2024.109735","DOIUrl":"10.1016/j.ijmecsci.2024.109735","url":null,"abstract":"<div><div>This paper introduces a novel method for shape and topology optimization based on a generalized approach for evaluating topological derivatives, which are essential for the integration of shape and topology optimization. Traditionally, evaluating these derivatives presents significant mathematical challenges due to the discontinuity introduced by the insertion of a hole within the domain of interest. To overcome this issue, the study employs Helmholtz-type partial differential equations (PDEs) to construct a filtered objective functional. This approach ensures differentiability across the material and void phases and continuity over the fixed design domain while maintaining the same evaluation value as the original objective functional. By considering differentiability, continuity conditions, and the relationship between shape and topological derivatives during asymptotic analysis, generalized topological derivatives are obtained through established mathematical procedures. These topological derivatives exhibit a direct correlation with the PDE solutions and demonstrate satisfactory smoothness, thereby facilitating refined shapes in optimization strategies. Furthermore, an effective shape update algorithm is proposed, which directly integrates topological derivatives into structural optimization problems, simplifying their implementation and improving efficiency. Finally, the efficacy of the proposed methodology is demonstrated through its application to various optimal design problems, including stiffness maximization, compliant mechanisms, and eigenfrequency maximization. Verification results further highlight its potential to enhance existing methods for addressing more practical and complex optimization challenges.</div></div>","PeriodicalId":56287,"journal":{"name":"International Journal of Mechanical Sciences","volume":"284 ","pages":"Article 109735"},"PeriodicalIF":7.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142318863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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