iFEM(inverse finite element method)是目前进行结构应变场构建最有前景的方法之一,其目的是在结构离散应变采集过程中,以最少的实际测点获取满足精度要求的结构应变场。在一些局部区域应变数据不易采集时,可尝试采用虚实结合的方式进...iFEM(inverse finite element method)是目前进行结构应变场构建最有前景的方法之一,其目的是在结构离散应变采集过程中,以最少的实际测点获取满足精度要求的结构应变场。在一些局部区域应变数据不易采集时,可尝试采用虚实结合的方式进行离散应变数据的采集。本文以船舶典型结构加筋板为例,根据实测数据,结合仿真模型,依据Xgboost的测点回归方法,基于iFEM技术依次计算实测、仿真和虚实结合三种方法的应变场重构精度,分析误差原因。通过预测,当47个物理测点时平均误差最低,为1.92%,以虚实结合路径输入15个点和21个点时结果与验证点的误差均小于3%,验证了虚实结合快速补充缺失数据的应变场重构的方法操作性强、准确度高。展开更多
Structural shape monitoring plays a vital role in the structural health monitoring systems.The inverse finite element method(iFEM)has been demonstrated to be a practical method of deformation reconstruction owing to i...Structural shape monitoring plays a vital role in the structural health monitoring systems.The inverse finite element method(iFEM)has been demonstrated to be a practical method of deformation reconstruction owing to its unique advantages.Current iFEM formulations have been applied to small deformation of structures based on the small-displacement assumption of linear theory.However,this assumption may be inapplicable to some structures with large displacements in practical applications.Therefore,geometric nonlinearity needs to be considered.In this study,to expand the practical utility of iFEM for large displacement monitoring,we propose a nonlinear iFEM algorithm based on a four-node inverse quadrilateral shell element iQS4.Taking the advantage of an iterative iFEM algorithm,a nonlinear response is linearized to compute the geometrically nonlinear deformation reconstruction,like the basic concept of nonlinear FE analysis.Several examples are solved to verify the proposed approach.It is demonstrated that large displacements can be accurately estimated even if the in-situ sensor data includes different levels of randomly generated noise.It is proven that the nonlinear iFEM algorithm provides a more accurate displacement response as compared to the linear iFEM methodology for structures undergoing large displacement.Hence,the proposed approach can be utilized as a viable tool to effectively characterize geometrically nonlinear deformations of structures in real-time applications.展开更多
With the advantages of biosafety and efficiency,increasing attention has been paid to the devices for gene and macromolecular drug delivery based on mechanoporation.The transient pore formation on the cell membrane al...With the advantages of biosafety and efficiency,increasing attention has been paid to the devices for gene and macromolecular drug delivery based on mechanoporation.The transient pore formation on the cell membrane allows cargo transportation when the membrane areal strain is beyond the critical pore value and below the lysis tension threshold.Based on this principle,we propose a method to apply the proper fluid stress on cells moving in a microchannel under the action of zero-net-mass-flux(ZNMF)jets.In this study,an immersed finite element method(IFEM)is adopted to simulate the interaction between the cells and the fluid fields so as to investigate the cell movement and deformation in this mechanoporation system.To evaluate the efficiency of the cargo delivery,a pore integral is defined as the mean pore rate when the cell passes through the jet region.By analyzing the effects of the parameters,including the pressure gradient along the microchannel,the jet amplitude,and the jet frequency,on the pore integrals,a group of optimized parameters for cargo delivery efficiency are obtained.Additionally,the stability and safety of this system are analyzed in detail.These results are helpful in designing the mechanoporation devices and improving their efficiency of drug delivery.展开更多
Thin plate and shell structures are extensively used in aerospace,naval,and energy sectors due to their lightweight and efficient load-bearing properties.Structural Health Monitoring(SHM)implementations are becoming i...Thin plate and shell structures are extensively used in aerospace,naval,and energy sectors due to their lightweight and efficient load-bearing properties.Structural Health Monitoring(SHM)implementations are becoming increasingly important in these industries to reduce maintenance costs,improve reliability,and ensure safe operations.This study presents an efficient triangular inverse shell element for thin shell structures,developed using discrete Kirchhoff assumptions within the inverse finite element method(iFEM)framework.The proposed inverse formulation is efficient and requires fewer strain sensors to achieve accurate and reliable displacement field reconstruction than existing inverse elements based on the First Order Shear Deformation Theory(FSDT).These features are critical to iFEM-based SHM strategies for improving real-time efficiency while reducing project costs.The inverse element is rigorously validated using benchmark problems under in-plane,out-of-plane,and general loading conditions.Also,its performance is compared to an existing competitive inverse shell element based on FSDT.The inverse formulation is further evaluated for robust shape-sensing capability,considering a real-world structural configuration under a practicable sparse sensor arrangement.Additional investigation includes defect characterization and structural health assessment using damage index criteria.This research contributes toward developing more reliable and cost-effective monitoring solutions by highlighting the potential application of the proposed inverse element for SHM frameworks designed for thin shell structures.展开更多
This study investigates the application of the inverse finite element method(iFEM)in fracture mechanics by developing a novel two-dimensional six-node triangular inverse crack-tip element.With its simplified formulati...This study investigates the application of the inverse finite element method(iFEM)in fracture mechanics by developing a novel two-dimensional six-node triangular inverse crack-tip element.With its simplified formulation,the proposed inverse element is computationally efficient and ensures strain singularity at the crack tip by repositioning midside nodes.Its displacement-based stress intensity factor(SIF)computation methodology integrates seamlessly with the existing iFEM framework,making it highly suitable for real-time health assessment of structures with preexisting cracks.The inverse element has been rigorously validated for shape-sensing and mixed-mode SIF calculations by considering various crack geometries and mixed-mode loading conditions.The triangular inverse element demonstrates superior flexibility in handling structured and unstructured discretizations in mapping regular and complex geometries,particularly high-stress gradient areas like crack tips.The study also explores the variational least squares method for optimal sensor placement within the inverse element domain,ensuring accurate shape-sensing and SIF computations with fewer onboard strain sensors.The proposed inverse formulation,with its accurate shape-sensing capabilities and precise reconstruction of fracture parameters,represents a significant advancement in the real-time Structural Health Monitoring of engineering structures with pre-existing cracks.展开更多
文摘iFEM(inverse finite element method)是目前进行结构应变场构建最有前景的方法之一,其目的是在结构离散应变采集过程中,以最少的实际测点获取满足精度要求的结构应变场。在一些局部区域应变数据不易采集时,可尝试采用虚实结合的方式进行离散应变数据的采集。本文以船舶典型结构加筋板为例,根据实测数据,结合仿真模型,依据Xgboost的测点回归方法,基于iFEM技术依次计算实测、仿真和虚实结合三种方法的应变场重构精度,分析误差原因。通过预测,当47个物理测点时平均误差最低,为1.92%,以虚实结合路径输入15个点和21个点时结果与验证点的误差均小于3%,验证了虚实结合快速补充缺失数据的应变场重构的方法操作性强、准确度高。
基金supported by the NationalNatural Science Foundation of China(Grant No.11902253)the Fundamental Research Funds for the Central Universities of China.The authors are grateful for this support.
文摘Structural shape monitoring plays a vital role in the structural health monitoring systems.The inverse finite element method(iFEM)has been demonstrated to be a practical method of deformation reconstruction owing to its unique advantages.Current iFEM formulations have been applied to small deformation of structures based on the small-displacement assumption of linear theory.However,this assumption may be inapplicable to some structures with large displacements in practical applications.Therefore,geometric nonlinearity needs to be considered.In this study,to expand the practical utility of iFEM for large displacement monitoring,we propose a nonlinear iFEM algorithm based on a four-node inverse quadrilateral shell element iQS4.Taking the advantage of an iterative iFEM algorithm,a nonlinear response is linearized to compute the geometrically nonlinear deformation reconstruction,like the basic concept of nonlinear FE analysis.Several examples are solved to verify the proposed approach.It is demonstrated that large displacements can be accurately estimated even if the in-situ sensor data includes different levels of randomly generated noise.It is proven that the nonlinear iFEM algorithm provides a more accurate displacement response as compared to the linear iFEM methodology for structures undergoing large displacement.Hence,the proposed approach can be utilized as a viable tool to effectively characterize geometrically nonlinear deformations of structures in real-time applications.
基金supported by the National Natural Science Foundation of China(Nos.11832017 and 12172209)the Key Research Project of Zhejiang Laboratory of China(No.2021PE0AC02)。
文摘With the advantages of biosafety and efficiency,increasing attention has been paid to the devices for gene and macromolecular drug delivery based on mechanoporation.The transient pore formation on the cell membrane allows cargo transportation when the membrane areal strain is beyond the critical pore value and below the lysis tension threshold.Based on this principle,we propose a method to apply the proper fluid stress on cells moving in a microchannel under the action of zero-net-mass-flux(ZNMF)jets.In this study,an immersed finite element method(IFEM)is adopted to simulate the interaction between the cells and the fluid fields so as to investigate the cell movement and deformation in this mechanoporation system.To evaluate the efficiency of the cargo delivery,a pore integral is defined as the mean pore rate when the cell passes through the jet region.By analyzing the effects of the parameters,including the pressure gradient along the microchannel,the jet amplitude,and the jet frequency,on the pore integrals,a group of optimized parameters for cargo delivery efficiency are obtained.Additionally,the stability and safety of this system are analyzed in detail.These results are helpful in designing the mechanoporation devices and improving their efficiency of drug delivery.
文摘Thin plate and shell structures are extensively used in aerospace,naval,and energy sectors due to their lightweight and efficient load-bearing properties.Structural Health Monitoring(SHM)implementations are becoming increasingly important in these industries to reduce maintenance costs,improve reliability,and ensure safe operations.This study presents an efficient triangular inverse shell element for thin shell structures,developed using discrete Kirchhoff assumptions within the inverse finite element method(iFEM)framework.The proposed inverse formulation is efficient and requires fewer strain sensors to achieve accurate and reliable displacement field reconstruction than existing inverse elements based on the First Order Shear Deformation Theory(FSDT).These features are critical to iFEM-based SHM strategies for improving real-time efficiency while reducing project costs.The inverse element is rigorously validated using benchmark problems under in-plane,out-of-plane,and general loading conditions.Also,its performance is compared to an existing competitive inverse shell element based on FSDT.The inverse formulation is further evaluated for robust shape-sensing capability,considering a real-world structural configuration under a practicable sparse sensor arrangement.Additional investigation includes defect characterization and structural health assessment using damage index criteria.This research contributes toward developing more reliable and cost-effective monitoring solutions by highlighting the potential application of the proposed inverse element for SHM frameworks designed for thin shell structures.
文摘This study investigates the application of the inverse finite element method(iFEM)in fracture mechanics by developing a novel two-dimensional six-node triangular inverse crack-tip element.With its simplified formulation,the proposed inverse element is computationally efficient and ensures strain singularity at the crack tip by repositioning midside nodes.Its displacement-based stress intensity factor(SIF)computation methodology integrates seamlessly with the existing iFEM framework,making it highly suitable for real-time health assessment of structures with preexisting cracks.The inverse element has been rigorously validated for shape-sensing and mixed-mode SIF calculations by considering various crack geometries and mixed-mode loading conditions.The triangular inverse element demonstrates superior flexibility in handling structured and unstructured discretizations in mapping regular and complex geometries,particularly high-stress gradient areas like crack tips.The study also explores the variational least squares method for optimal sensor placement within the inverse element domain,ensuring accurate shape-sensing and SIF computations with fewer onboard strain sensors.The proposed inverse formulation,with its accurate shape-sensing capabilities and precise reconstruction of fracture parameters,represents a significant advancement in the real-time Structural Health Monitoring of engineering structures with pre-existing cracks.
