Pub Date : 2024-10-21DOI: 10.1016/j.tws.2024.112604
Damir Akchurin , Shahabeddin Torabian , Benjamin W. Schafer
This paper presents a summary of experimental findings from axial compression tests on columns featuring a cold-formed lipped channel section with intermediate stiffeners and return lips, roll-formed from high-strength low-allow steel with a nominal yield strength of 690 MPa (100 ksi). Additionally, the paper provides an analysis of the elastic stability of the studied section, a complete description of the initial geometric imperfections of the tested columns, results of tensile coupon tests, and comparison of the observed strengths of the columns with design predictions. The results provide important additional benchmarks for the wider adoption of high-strength cold-formed steel sections and indicate conditions where existing design methods may be reliably extended.
{"title":"High-strength cold-formed steel stiffened channel section: Axial compressive strength and initial geometric imperfections","authors":"Damir Akchurin , Shahabeddin Torabian , Benjamin W. Schafer","doi":"10.1016/j.tws.2024.112604","DOIUrl":"10.1016/j.tws.2024.112604","url":null,"abstract":"<div><div>This paper presents a summary of experimental findings from axial compression tests on columns featuring a cold-formed lipped channel section with intermediate stiffeners and return lips, roll-formed from high-strength low-allow steel with a nominal yield strength of 690 MPa (100 ksi). Additionally, the paper provides an analysis of the elastic stability of the studied section, a complete description of the initial geometric imperfections of the tested columns, results of tensile coupon tests, and comparison of the observed strengths of the columns with design predictions. The results provide important additional benchmarks for the wider adoption of high-strength cold-formed steel sections and indicate conditions where existing design methods may be reliably extended.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"206 ","pages":"Article 112604"},"PeriodicalIF":5.7,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661812","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 : 2024-10-21DOI: 10.1016/j.tws.2024.112603
Sajal, Pranesh Roy
This paper presents a finite deformation beam model based on Simo-Reissner theory in peridynamics (PD) framework to deal with torsion induced warping deformation. Seven degrees of freedom, viz. three translational, three rotational, and one warping amplitude are considered at each material point. The governing equations of the beam are obtained by employing global balance of linear and angular momenta in conjunction with Simo's assumption on the deformation field. The relation between PD resultant force, moment, bi-moment, and bi-shear states with their classical counterparts is established using the constitutive correspondence method. Numerical implementation strategy is furnished for both quasi-static and dynamic cases. The solution for quasi-static load is obtained through the Newton-Raphson method. The proposed model is validated against finite element solutions considering cantilever beam and lattice structures. Quasi-static deformation responses of 3 3 3 octet and single unit compression-torsion lattice structures are presented further to demonstrate the effectiveness of proposed beam model. A new bond breaking criterion is proposed based on critical stretch, critical relative rotation, and critical relative warping amplitude and failure of the compression-torsion lattice structures under compressive load is simulated. The Newmark-beta method is utilized to solve the governing equations for dynamic loading. Numerical simulations include dynamic analysis of octet and compression-torsion lattice structures.
{"title":"Peridynamics model of torsion-warping: Application to lattice beam structures","authors":"Sajal, Pranesh Roy","doi":"10.1016/j.tws.2024.112603","DOIUrl":"10.1016/j.tws.2024.112603","url":null,"abstract":"<div><div>This paper presents a finite deformation beam model based on Simo-Reissner theory in peridynamics (PD) framework to deal with torsion induced warping deformation. Seven degrees of freedom, viz. three translational, three rotational, and one warping amplitude are considered at each material point. The governing equations of the beam are obtained by employing global balance of linear and angular momenta in conjunction with Simo's assumption on the deformation field. The relation between PD resultant force, moment, bi-moment, and bi-shear states with their classical counterparts is established using the constitutive correspondence method. Numerical implementation strategy is furnished for both quasi-static and dynamic cases. The solution for quasi-static load is obtained through the Newton-Raphson method. The proposed model is validated against finite element solutions considering cantilever beam and lattice structures. Quasi-static deformation responses of 3 <span><math><mo>×</mo></math></span> 3 <span><math><mo>×</mo></math></span> 3 octet and single unit compression-torsion lattice structures are presented further to demonstrate the effectiveness of proposed beam model. A new bond breaking criterion is proposed based on critical stretch, critical relative rotation, and critical relative warping amplitude and failure of the compression-torsion lattice structures under compressive load is simulated. The Newmark-beta method is utilized to solve the governing equations for dynamic loading. Numerical simulations include dynamic analysis of octet and compression-torsion lattice structures.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"206 ","pages":"Article 112603"},"PeriodicalIF":5.7,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142663991","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 : 2024-10-21DOI: 10.1016/j.tws.2024.112609
Xueli Zhou , Hongpei Liu , Jifeng Zhang , Lei Ren , Lu Zhang , Qingping Liu , Bingqian Li , Chao Xu , Luquan Ren
Conventional vibration isolators are designed and assembled so that their structure and vibration isolation performance cannot be adjusted and have a single function when facing complex working conditions. Inspired by a cat's adaptive adjustment of its limb structure to land safely when leaping from a height, we designed a bio-inspired polygonal metamaterial and 3D-molded it based on 4D printing of shape memory polymers (SMP). Based on the shape memory effect of the SMP, the BPM can obtain arbitrary temporary shapes under the combined effect of temperature and force. According to the analysis of the energy absorption test, by change the compressive strain of the BPM temporary shape, it is possible to adjust the shape of the single-cell structure while decreasing its specific energy absorption by up to 80 %. The locally controllable compressive deformation and programmable mechanical properties of the BPM structure are achieved through rational structural parameter design. In addition, thermally tunable vibration-absorbing behavior is achieved by combining the tunable stiffness properties of the printed material. This study provides new possibilities for intelligent tuning of cushion vibration isolators under complex and variable operating conditions.
{"title":"4D printed bio-inspired polygonal metamaterials with tunable mechanical properties","authors":"Xueli Zhou , Hongpei Liu , Jifeng Zhang , Lei Ren , Lu Zhang , Qingping Liu , Bingqian Li , Chao Xu , Luquan Ren","doi":"10.1016/j.tws.2024.112609","DOIUrl":"10.1016/j.tws.2024.112609","url":null,"abstract":"<div><div>Conventional vibration isolators are designed and assembled so that their structure and vibration isolation performance cannot be adjusted and have a single function when facing complex working conditions. Inspired by a cat's adaptive adjustment of its limb structure to land safely when leaping from a height, we designed a bio-inspired polygonal metamaterial and 3D-molded it based on 4D printing of shape memory polymers (SMP). Based on the shape memory effect of the SMP, the BPM can obtain arbitrary temporary shapes under the combined effect of temperature and force. According to the analysis of the energy absorption test, by change the compressive strain of the BPM temporary shape, it is possible to adjust the shape of the single-cell structure while decreasing its specific energy absorption by up to 80 %. The locally controllable compressive deformation and programmable mechanical properties of the BPM structure are achieved through rational structural parameter design. In addition, thermally tunable vibration-absorbing behavior is achieved by combining the tunable stiffness properties of the printed material. This study provides new possibilities for intelligent tuning of cushion vibration isolators under complex and variable operating conditions.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112609"},"PeriodicalIF":5.7,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539526","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 : 2024-10-21DOI: 10.1016/j.tws.2024.112610
Yehui Cui , Zhilang Zhang
Performing concurrent simulations of macroscopic behaviors and microscopic structures using the crystal plasticity finite element method (CPFEM) presents a substantial difficulty with existing numerical techniques. To address this issue, a novel multi-scale method is proposed that couples CPFEM with a multiscale FEM, specifically Direct FE2. This facilitates the implementation of Direct CP-FE2 in this work. The micro representative volume elements (RVEs) equipped with a crystal plasticity constitutive model and the macro mesh are integrated into a monolithic solution scheme within the Direct FE2 framework. The proposed method integrates the multiscale simulation capability of Direct FE2 with the crystal plasticity model of CPFEM. Alpha titanium (α-Ti), which exhibits two distinct plastic mechanisms of slip and twinning, is chosen as the subject of investigation for conducting numerical experiments. The accuracy and efficiency of the Direct CP-FE2 model are evaluated through multiple plate tension and beam bending tests. The effective validation against the FEM model demonstrated the capability of Direct CP-FE2 to forecast macroscopic deformation behaviors. Meanwhile, the Direct CP-FE2 model can reveal the activation of slip/twinning systems and the evolution of crystal texture at a microscopic level. The influence of the grain orientation-dependent effect can be well considered into the macroscopic analysis with the help of Direct CP-FE2. Based on the testing examples, we demonstrate that the yield state of the macrostructure is enhanced when the crystal orientation is closer to the (0001) direction. Consequently, there exist very little crystal rotation behavior, hindering the evolution of the crystal texture.
使用晶体塑性有限元法（CPFEM）同时模拟宏观行为和微观结构是现有数值技术的一大难题。为了解决这个问题，我们提出了一种新颖的多尺度方法，将 CPFEM 与多尺度有限元方法（特别是 Direct FE2）结合起来。这为本研究中直接 CP-FE2 的实施提供了便利。在 Direct FE2 框架内，配备晶体塑性构成模型的微观代表体积元素（RVE）和宏观网格被集成到一个整体求解方案中。所提出的方法集成了 Direct FE2 的多尺度模拟能力和 CPFEM 的晶体塑性模型。α-钛（α-Ti）具有滑移和孪晶两种不同的塑性机制，因此被选为进行数值实验的研究对象。通过多次板拉伸和梁弯曲试验，评估了直接 CP-FE2 模型的准确性和效率。与有限元模型的有效验证证明了直接 CP-FE2 预测宏观变形行为的能力。同时，Direct CP-FE2 模型还能在微观层面揭示滑移/孪晶系统的激活和晶体纹理的演变。在直接 CP-FE2 的帮助下，宏观分析可以很好地考虑晶粒取向相关效应的影响。基于测试实例，我们证明了当晶体取向更接近（0001）方向时，宏观结构的屈服状态会增强。因此，几乎不存在晶体旋转行为，从而阻碍了晶体纹理的演化。
{"title":"A novel concurrent multiscale method based on the coupling of Direct FE2 and CPFEM","authors":"Yehui Cui , Zhilang Zhang","doi":"10.1016/j.tws.2024.112610","DOIUrl":"10.1016/j.tws.2024.112610","url":null,"abstract":"<div><div>Performing concurrent simulations of macroscopic behaviors and microscopic structures using the crystal plasticity finite element method (CPFEM) presents a substantial difficulty with existing numerical techniques. To address this issue, a novel multi-scale method is proposed that couples CPFEM with a multiscale FEM, specifically Direct FE<sup>2</sup>. This facilitates the implementation of Direct CP-FE<sup>2</sup> in this work. The micro representative volume elements (RVEs) equipped with a crystal plasticity constitutive model and the macro mesh are integrated into a monolithic solution scheme within the Direct FE<sup>2</sup> framework. The proposed method integrates the multiscale simulation capability of Direct FE<sup>2</sup> with the crystal plasticity model of CPFEM. Alpha titanium (α-Ti), which exhibits two distinct plastic mechanisms of slip and twinning, is chosen as the subject of investigation for conducting numerical experiments. The accuracy and efficiency of the Direct CP-FE<sup>2</sup> model are evaluated through multiple plate tension and beam bending tests. The effective validation against the FEM model demonstrated the capability of Direct CP-FE<sup>2</sup> to forecast macroscopic deformation behaviors. Meanwhile, the Direct CP-FE<sup>2</sup> model can reveal the activation of slip/twinning systems and the evolution of crystal texture at a microscopic level. The influence of the grain orientation-dependent effect can be well considered into the macroscopic analysis with the help of Direct CP-FE<sup>2</sup>. Based on the testing examples, we demonstrate that the yield state of the macrostructure is enhanced when the crystal orientation is closer to the (0001) direction. Consequently, there exist very little crystal rotation behavior, hindering the evolution of the crystal texture.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"206 ","pages":"Article 112610"},"PeriodicalIF":5.7,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554943","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 : 2024-10-19DOI: 10.1016/j.tws.2024.112602
Weiqiang Wang , Zhilong Xiong , Yang Yu , Da Chen , Chengqing Wu
Ultra-high performance concrete (UHPC)-filled double-skin steel tubular (DST) column has great potential to be used in the protective structures. Although its lateral impact behaviour has been well understood, the residual behaviour after lateral impact remains unexplored. As a result, this study extensively investigated the residual behaviour and damage assessment of UHPC-filled DST columns after lateral impact. Firstly, a set of six DST columns were designed and tested under lateral impact, followed by static axial compression. In addition, two intact columns were subjected to static axial compression for comparative analysis. Secondly, the refined finite element models were developed and validated using the current test data, and the impact resistant mechanism of UHPC-filled DST columns with different impact locations was analysed. Thirdly, the suitability of different damage indexes for the damage assessment of impacted UHPC-filled DST columns was evaluated. Two damage indexes, the ratio of mid-height deflection to column height (), and the ratio of local deflection to the column diameter (), were proposed for the DST columns. Finally, two types of machine learning-based models were developed to predict the impact damage of UHPC-filled DST columns. The prediction models were interpreted locally and globally using the additive feature attribution method Shapley Additive Explanation (SHAP). The machine learning-based prediction models can rapidly evaluate the damage extent of impacted UHPC-filled DST column, which hold great significance for the selection of strengthening and retrofitting schemes.
{"title":"Residual behaviour and damage assessment of UHPC-filled double-skin steel tubular columns after lateral impact","authors":"Weiqiang Wang , Zhilong Xiong , Yang Yu , Da Chen , Chengqing Wu","doi":"10.1016/j.tws.2024.112602","DOIUrl":"10.1016/j.tws.2024.112602","url":null,"abstract":"<div><div>Ultra-high performance concrete (UHPC)-filled double-skin steel tubular (DST) column has great potential to be used in the protective structures. Although its lateral impact behaviour has been well understood, the residual behaviour after lateral impact remains unexplored. As a result, this study extensively investigated the residual behaviour and damage assessment of UHPC-filled DST columns after lateral impact. Firstly, a set of six DST columns were designed and tested under lateral impact, followed by static axial compression. In addition, two intact columns were subjected to static axial compression for comparative analysis. Secondly, the refined finite element models were developed and validated using the current test data, and the impact resistant mechanism of UHPC-filled DST columns with different impact locations was analysed. Thirdly, the suitability of different damage indexes for the damage assessment of impacted UHPC-filled DST columns was evaluated. Two damage indexes, the ratio of mid-height deflection to column height (<span><math><msub><mi>R</mi><mn>1</mn></msub></math></span>), and the ratio of local deflection to the column diameter (<span><math><msub><mi>R</mi><mn>2</mn></msub></math></span>), were proposed for the DST columns. Finally, two types of machine learning-based models were developed to predict the impact damage of UHPC-filled DST columns. The prediction models were interpreted locally and globally using the additive feature attribution method Shapley Additive Explanation (SHAP). The machine learning-based prediction models can rapidly evaluate the damage extent of impacted UHPC-filled DST column, which hold great significance for the selection of strengthening and retrofitting schemes.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112602"},"PeriodicalIF":5.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539523","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 : 2024-10-19DOI: 10.1016/j.tws.2024.112590
D.P.M. da Costa , M.M. Kasaei , R.J.C. Carbas , E.A.S. Marques , L.F.M. da Silva
In this paper, a joining by forming technique is suggested to join aluminium and copper sheets, aimed at potential hybrid busbar manufacturing. The technique, called hole hemming, is performed through the deformation of the aluminium sheet to create a mechanical interlock with the copper sheet, requiring neither heat, welding, nor additional elements/materials. Initially, the feasibility of this joining process is assessed using an analytical model to determine the parameters required for achieving a mechanical interlock while avoiding fractures. The accuracy of the process windows developed by this model is validated through comparisons with experimental results and numerical simulations. In these simulations, the Modified Mohr-Coulomb criterion is employed to predict ductile damage. Furthermore, a new design incorporating branches in the aluminium sheet holes is introduced. This innovation allows for fracture-free joint manufacturing beyond the safe limits predicted by the analytical model, thereby expanding the range of feasible process parameters. Subsequently, the mechanical performance of joints with and without branches is evaluated through destructive shear and cross-tension tests at both room temperature and an elevated temperature of 120 °C, simulating the maximum service conditions for busbars. The results demonstrate that hole hemming effectively joins AA6082-T4 and Cu-ETP R240 sheets, validating the proposed designs. Specifically, the hybrid aluminium and copper joints exhibit a maximum shear strength of 4.35 kN and a displacement of 12.11 mm at room temperature. In cross-tension tests, the joints achieve a maximum strength of 1.73 kN and a displacement of 9.86 mm. Although performance slightly diminishes at elevated temperatures, it remains excellent for both destructive test configurations.
{"title":"A novel joining technology for hybrid busbars in electric vehicle batteries","authors":"D.P.M. da Costa , M.M. Kasaei , R.J.C. Carbas , E.A.S. Marques , L.F.M. da Silva","doi":"10.1016/j.tws.2024.112590","DOIUrl":"10.1016/j.tws.2024.112590","url":null,"abstract":"<div><div>In this paper, a joining by forming technique is suggested to join aluminium and copper sheets, aimed at potential hybrid busbar manufacturing. The technique, called hole hemming, is performed through the deformation of the aluminium sheet to create a mechanical interlock with the copper sheet, requiring neither heat, welding, nor additional elements/materials. Initially, the feasibility of this joining process is assessed using an analytical model to determine the parameters required for achieving a mechanical interlock while avoiding fractures. The accuracy of the process windows developed by this model is validated through comparisons with experimental results and numerical simulations. In these simulations, the Modified Mohr-Coulomb criterion is employed to predict ductile damage. Furthermore, a new design incorporating branches in the aluminium sheet holes is introduced. This innovation allows for fracture-free joint manufacturing beyond the safe limits predicted by the analytical model, thereby expanding the range of feasible process parameters. Subsequently, the mechanical performance of joints with and without branches is evaluated through destructive shear and cross-tension tests at both room temperature and an elevated temperature of 120 °C, simulating the maximum service conditions for busbars. The results demonstrate that hole hemming effectively joins AA6082-T4 and Cu-ETP R240 sheets, validating the proposed designs. Specifically, the hybrid aluminium and copper joints exhibit a maximum shear strength of 4.35 kN and a displacement of 12.11 mm at room temperature. In cross-tension tests, the joints achieve a maximum strength of 1.73 kN and a displacement of 9.86 mm. Although performance slightly diminishes at elevated temperatures, it remains excellent for both destructive test configurations.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112590"},"PeriodicalIF":5.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539473","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 : 2024-10-19DOI: 10.1016/j.tws.2024.112599
Xi Fang, Hui-Shen Shen, Hai Wang
Building on a deep generative model (DGM), this paper introduces an innovative sandwich plate structure featuring an inverse-designed auxetic 3D lattice core and conducts a detailed investigation of its nonlinear vibration characteristics and effective Poisson's ratios under various parameter settings. By incorporating a conditional estimator and quality loss evaluation functions, the enhanced conditional generative adversarial networks are capable of designing 3D truss auxetic topologies that achieve customized negative Poisson's ratios without reliance on subjective experience. Additionally, lattice specimens are created using 3D metal printing, and the mechanical properties of these DGM-based 3D auxetic structures are validated through vibration experiments and finite element models. These structures exhibit significantly superior natural frequencies compared to those obtained through conventional topology optimization methods reported in existing literature. The study also explores the impact of different functionally graded configurations, temperature variations, boundary conditions, and dimensional parameters on the natural frequency, nonlinear vibration response, and effective Poisson's ratio of the inverse designed auxetic sandwich plates.
{"title":"Nonlinear vibration analysis of sandwich plates with inverse-designed 3D auxetic core by deep generative model","authors":"Xi Fang, Hui-Shen Shen, Hai Wang","doi":"10.1016/j.tws.2024.112599","DOIUrl":"10.1016/j.tws.2024.112599","url":null,"abstract":"<div><div>Building on a deep generative model (DGM), this paper introduces an innovative sandwich plate structure featuring an inverse-designed auxetic 3D lattice core and conducts a detailed investigation of its nonlinear vibration characteristics and effective Poisson's ratios under various parameter settings. By incorporating a conditional estimator and quality loss evaluation functions, the enhanced conditional generative adversarial networks are capable of designing 3D truss auxetic topologies that achieve customized negative Poisson's ratios without reliance on subjective experience. Additionally, lattice specimens are created using 3D metal printing, and the mechanical properties of these DGM-based 3D auxetic structures are validated through vibration experiments and finite element models. These structures exhibit significantly superior natural frequencies compared to those obtained through conventional topology optimization methods reported in existing literature. The study also explores the impact of different functionally graded configurations, temperature variations, boundary conditions, and dimensional parameters on the natural frequency, nonlinear vibration response, and effective Poisson's ratio of the inverse designed auxetic sandwich plates.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"206 ","pages":"Article 112599"},"PeriodicalIF":5.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572867","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 : 2024-10-18DOI: 10.1016/j.tws.2024.112580
Jinwen Xia , Youjiang Cui , Baolin Wang , Kaifa Wang
Anti-tetrachiral structures (AS) are typical metamaterials known for their negative Poisson's ratio, and have great potential application in reducting the damage of the ship caused by collisions. The existing analysis of the mechanical properties of AS is conducted by applying the energy method to a unit cell with periodic boundary conditions (PBC). In available works, the shear force at the structure's boundaries is neglected. But is it permissible to disregard the impact of shear forces at the boundaries on the structure's equivalent mechanical properties? By examining the deformation relationship between the ribs and the nodal rings, we developed a uniaxial compression model for AS under both free and constrained boundary conditions, which accurately predicts the mechanical properties of the AS structure. This model was validated through numerical simulations and experiments. The findings reveal that the equivalent mechanical properties of AS exhibit a size dependence related to the cell size. For example, for AS with equivalent density and identical overall dimensions, the equivalent Young's modulus of an AS with 2×2 cells will be twice that of an AS with 4×4 cells. Furthermore, the size effect of the structure can be neglected when the number of cells larger than 8×8. Moreover, it is found that the present model considering boundary conditions exhibits an equivalent Young's modulus 25 % higher than the model neglecting boundary conditions. The study's findings indicate that the presence of boundary conditions can disrupt PBC, leading to significant discrepancies between theoretical derivations and practical applications.
反四螺旋结构（AS）是一种典型的超材料，因其负泊松比而闻名，在减少船舶碰撞造成的损坏方面具有巨大的应用潜力。现有的 AS 机械特性分析是通过将能量法应用于具有周期性边界条件（PBC）的单元格来进行的。在现有研究中，结构边界的剪切力被忽略。但是否可以忽略边界剪力对结构等效力学性能的影响呢？通过研究肋骨和节点环之间的变形关系，我们建立了自由和约束边界条件下的 AS 单轴压缩模型，该模型能准确预测 AS 结构的力学性能。我们通过数值模拟和实验对该模型进行了验证。研究结果表明，AS 的等效力学性能与细胞大小有关。例如，对于具有相同密度和相同整体尺寸的 AS，2×2 单元 AS 的等效杨氏模量是 4×4 单元 AS 的两倍。此外，当单元数大于 8×8 时，结构的尺寸效应可以忽略。此外，研究还发现，考虑到边界条件的本模型的等效杨氏模量比忽略边界条件的模型高 25%。研究结果表明，边界条件的存在会破坏 PBC，从而导致理论推导与实际应用之间存在显著差异。
{"title":"Uniaxial compression performance of anti-tetrachiral structures considering the effects of cell size and boundary conditions","authors":"Jinwen Xia , Youjiang Cui , Baolin Wang , Kaifa Wang","doi":"10.1016/j.tws.2024.112580","DOIUrl":"10.1016/j.tws.2024.112580","url":null,"abstract":"<div><div>Anti-tetrachiral structures (AS) are typical metamaterials known for their negative Poisson's ratio, and have great potential application in reducting the damage of the ship caused by collisions. The existing analysis of the mechanical properties of AS is conducted by applying the energy method to a unit cell with periodic boundary conditions (PBC). In available works, the shear force at the structure's boundaries is neglected. But is it permissible to disregard the impact of shear forces at the boundaries on the structure's equivalent mechanical properties? By examining the deformation relationship between the ribs and the nodal rings, we developed a uniaxial compression model for AS under both free and constrained boundary conditions, which accurately predicts the mechanical properties of the AS structure. This model was validated through numerical simulations and experiments. The findings reveal that the equivalent mechanical properties of AS exhibit a size dependence related to the cell size. For example, for AS with equivalent density and identical overall dimensions, the equivalent Young's modulus of an AS with 2×2 cells will be twice that of an AS with 4×4 cells. Furthermore, the size effect of the structure can be neglected when the number of cells larger than 8×8. Moreover, it is found that the present model considering boundary conditions exhibits an equivalent Young's modulus 25 % higher than the model neglecting boundary conditions. The study's findings indicate that the presence of boundary conditions can disrupt PBC, leading to significant discrepancies between theoretical derivations and practical applications.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112580"},"PeriodicalIF":5.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539524","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 : 2024-10-18DOI: 10.1016/j.tws.2024.112587
L. Simwanda , P. Gatheeshgar , F.M. Ilunga , B.D. Ikotun , S.M. Mojtabaei , E.K. Onyari
This study develops explainable machine learning (ML) models to predict the ultimate bending capacity of cold-formed steel (CFS) beams with staggered slotted perforations, focusing on distortional buckling behavior. Utilizing a dataset from 432 non-linear finite element analysis simulations of CFS Lipped channels, ten ML algorithms, including four basic and six ensemble models, were evaluated. Ensemble models, specifically CatBoost and XGBoost, demonstrated superior accuracy, with test-set performances reaching a coefficient of determination () of 99.9%, outperforming traditional analytical methods such as the Direct Strength Method (DSM). SHapley Additive Explanations (SHAP) were applied to highlight how features like plate thickness and root radius critically influence predictions. The findings underscore the enhanced predictive capabilities of ML models for structural performance, suggesting a significant potential to refine traditional design methodologies and optimize CFS beam designs.
{"title":"Explainable machine learning models for predicting the ultimate bending capacity of slotted perforated cold-formed steel beams under distortional buckling","authors":"L. Simwanda , P. Gatheeshgar , F.M. Ilunga , B.D. Ikotun , S.M. Mojtabaei , E.K. Onyari","doi":"10.1016/j.tws.2024.112587","DOIUrl":"10.1016/j.tws.2024.112587","url":null,"abstract":"<div><div>This study develops explainable machine learning (ML) models to predict the ultimate bending capacity of cold-formed steel (CFS) beams with staggered slotted perforations, focusing on distortional buckling behavior. Utilizing a dataset from 432 non-linear finite element analysis simulations of CFS Lipped channels, ten ML algorithms, including four basic and six ensemble models, were evaluated. Ensemble models, specifically CatBoost and XGBoost, demonstrated superior accuracy, with test-set performances reaching a coefficient of determination (<span><math><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>) of 99.9%, outperforming traditional analytical methods such as the Direct Strength Method (DSM). SHapley Additive Explanations (SHAP) were applied to highlight how features like plate thickness and root radius critically influence predictions. The findings underscore the enhanced predictive capabilities of ML models for structural performance, suggesting a significant potential to refine traditional design methodologies and optimize CFS beam designs.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"205 ","pages":"Article 112587"},"PeriodicalIF":5.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539525","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 : 2024-10-18DOI: 10.1016/j.tws.2024.112577
H.N.R. Wagner , C. Hühne
Wind turbine towers pose major challenges for design engineers due to their complex geometry, nonlinear material behavior and imperfection sensitivity. In service, these thin-walled shells are burdened by a combination of complex load cases and prone to buckling. In fact, one of the main design drivers of wind turbine towers is stability failure for which often the design recommendation of the EN-1993–1–6 are used.
Recently an international shell buckling exercise was caried out by the team behind the EN-1993–1–6 design standard. Within this exercise 29 teams from academia and industry were asked to perform a series of linear and non-linear finite element simulations of an 8-MW multi-strake steel wind turbine support tower segment. In general, the linear and nonlinear analyzes posed no challenge for the shell buckling experts from around the world. However, the imperfection sensitivity analysis results scattered significantly among the participants. In addition, there was little consensus as to whether the given tower design is actually safe.
The authors, whose background is aerospace engineering, participated in this exercise and show in this article how they overcome the challenges of this typical civil engineering problem. Among linear and non-linear analyzes the authors show the results of state-of-the-art shell buckling concepts which were developed for aerospace shells like interstage tanks and adapters but are also applicable to wind turbine towers.
{"title":"On the imperfection sensitivity and design of buckling critical wind turbine towers","authors":"H.N.R. Wagner , C. Hühne","doi":"10.1016/j.tws.2024.112577","DOIUrl":"10.1016/j.tws.2024.112577","url":null,"abstract":"<div><div>Wind turbine towers pose major challenges for design engineers due to their complex geometry, nonlinear material behavior and imperfection sensitivity. In service, these thin-walled shells are burdened by a combination of complex load cases and prone to buckling. In fact, one of the main design drivers of wind turbine towers is stability failure for which often the design recommendation of the EN-1993–1–6 are used.</div><div>Recently an international shell buckling exercise was caried out by the team behind the EN-1993–1–6 design standard. Within this exercise 29 teams from academia and industry were asked to perform a series of linear and non-linear finite element simulations of an 8-MW multi-strake steel wind turbine support tower segment. In general, the linear and nonlinear analyzes posed no challenge for the shell buckling experts from around the world. However, the imperfection sensitivity analysis results scattered significantly among the participants. In addition, there was little consensus as to whether the given tower design is actually safe.</div><div>The authors, whose background is aerospace engineering, participated in this exercise and show in this article how they overcome the challenges of this typical civil engineering problem. Among linear and non-linear analyzes the authors show the results of state-of-the-art shell buckling concepts which were developed for aerospace shells like interstage tanks and adapters but are also applicable to wind turbine towers.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"206 ","pages":"Article 112577"},"PeriodicalIF":5.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572873","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}
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