Material identification is critical for understanding the relationship between mechanical properties and the associated mechanical functions.However,material identification is a challenging task,especially when the ch...Material identification is critical for understanding the relationship between mechanical properties and the associated mechanical functions.However,material identification is a challenging task,especially when the characteristic of the material is highly nonlinear in nature,as is common in biological tissue.In this work,we identify unknown material properties in continuum solid mechanics via physics-informed neural networks(PINNs).To improve the accuracy and efficiency of PINNs,we develop efficient strategies to nonuniformly sample observational data.We also investigate different approaches to enforce Dirichlet-type boundary conditions(BCs)as soft or hard constraints.Finally,we apply the proposed methods to a diverse set of time-dependent and time-independent solid mechanic examples that span linear elastic and hyperelastic material space.The estimated material parameters achieve relative errors of less than 1%.As such,this work is relevant to diverse applications,including optimizing structural integrity and developing novel materials.展开更多
The manuscript reviews the history and quo of the theory of Timoshenko’s method in stability analysis of compressive levers first, taking an example to explain the m-simulation method and putting forward the 3rd-7th ...The manuscript reviews the history and quo of the theory of Timoshenko’s method in stability analysis of compressive levers first, taking an example to explain the m-simulation method and putting forward the 3rd-7th boundary conditions demonstrating their superiorities in improving the precision through examples, followed by proposing and applying the join conditions in the stability analysis of combined axial force compressive levers gaining success. Through a brief example showing the effect of some related theories in a simple structural stability analysis, its application prospect is discussed.展开更多
Spans occur when a pipeline is laid on a rough undulating seabed or when upheaval buckling occurs due to constrained thermal expansion. This not only results in static and dynamic loads on the flowline at span section...Spans occur when a pipeline is laid on a rough undulating seabed or when upheaval buckling occurs due to constrained thermal expansion. This not only results in static and dynamic loads on the flowline at span sections,but also generates vortex induced vibration (VIV),which can lead to fatigue issues. The phenomenon,if not predicted and controlled properly,will negatively affect pipeline integrity,leading to expensive remediation and intervention work. Span analysis can be complicated by:long span lengths,a large number of spans caused by a rough seabed,and multi-span interactions. In addition,the complexity can be more onerous and challenging when soil uncertainty,concrete degradation and unknown residual lay tension are considered in the analysis. This paper describes the latest developments and a'state-of-the-art' finite element analysis program that has been developed to simulate the span response of a flowline under complex boundary and loading conditions. Both VIV and direct wave loading are captured in the analysis and the results are sequentially used for the ultimate limit state (ULS) check and fatigue life calculation.展开更多
The simulation of rarefied gasflows through complex porous media is chal-lenging due to the tortuousflow pathways inherent to such structures.The Lattice Boltzmann method(LBM)has been identified as a promising avenue ...The simulation of rarefied gasflows through complex porous media is chal-lenging due to the tortuousflow pathways inherent to such structures.The Lattice Boltzmann method(LBM)has been identified as a promising avenue to solveflows through complex geometries due to the simplicity of its scheme and its high parallel computational efficiency.It has been proposed to model the stress-strain relationship with the extended Navier-Stokes equations rather than attempting to directly solve the Boltzmann equation.However,a regularization technique is required tofilter out non-resolved higher-order components with a low-order velocity scheme.Although slip boundary conditions(BCs)have been proposed for the non-regularized multiple relaxation time LBM(MRT-LBM)for planar geometries,previous slip BCs have never been verified extensively with the regularization technique.In this work,following an extensive literature review on the imposition of slip BCs for rarefiedflows with the LBM,it is proven that earlier values for kinetic parameters developed to impose slip BCs are inaccurate for the regularized MRT-LBM and differ between the D2Q9 and D3Q15 schemes.The error was eliminated for planarflows and good agreement be-tween analytical solutions for arrays of cylinders and spheres was found with a wide range of Knudsen numbers.展开更多
基金funded by the Cora Topolewski Cardiac Research Fund at the Children’s Hospital of Philadelphia(CHOP)the Pediatric Valve Center Frontier Program at CHOP+4 种基金the Additional Ventures Single Ventricle Research Fund Expansion Awardthe National Institutes of Health(USA)supported by the program(Nos.NHLBI T32 HL007915 and NIH R01 HL153166)supported by the program(No.NIH R01 HL153166)supported by the U.S.Department of Energy(No.DE-SC0022953)。
文摘Material identification is critical for understanding the relationship between mechanical properties and the associated mechanical functions.However,material identification is a challenging task,especially when the characteristic of the material is highly nonlinear in nature,as is common in biological tissue.In this work,we identify unknown material properties in continuum solid mechanics via physics-informed neural networks(PINNs).To improve the accuracy and efficiency of PINNs,we develop efficient strategies to nonuniformly sample observational data.We also investigate different approaches to enforce Dirichlet-type boundary conditions(BCs)as soft or hard constraints.Finally,we apply the proposed methods to a diverse set of time-dependent and time-independent solid mechanic examples that span linear elastic and hyperelastic material space.The estimated material parameters achieve relative errors of less than 1%.As such,this work is relevant to diverse applications,including optimizing structural integrity and developing novel materials.
文摘The manuscript reviews the history and quo of the theory of Timoshenko’s method in stability analysis of compressive levers first, taking an example to explain the m-simulation method and putting forward the 3rd-7th boundary conditions demonstrating their superiorities in improving the precision through examples, followed by proposing and applying the join conditions in the stability analysis of combined axial force compressive levers gaining success. Through a brief example showing the effect of some related theories in a simple structural stability analysis, its application prospect is discussed.
文摘Spans occur when a pipeline is laid on a rough undulating seabed or when upheaval buckling occurs due to constrained thermal expansion. This not only results in static and dynamic loads on the flowline at span sections,but also generates vortex induced vibration (VIV),which can lead to fatigue issues. The phenomenon,if not predicted and controlled properly,will negatively affect pipeline integrity,leading to expensive remediation and intervention work. Span analysis can be complicated by:long span lengths,a large number of spans caused by a rough seabed,and multi-span interactions. In addition,the complexity can be more onerous and challenging when soil uncertainty,concrete degradation and unknown residual lay tension are considered in the analysis. This paper describes the latest developments and a'state-of-the-art' finite element analysis program that has been developed to simulate the span response of a flowline under complex boundary and loading conditions. Both VIV and direct wave loading are captured in the analysis and the results are sequentially used for the ultimate limit state (ULS) check and fatigue life calculation.
基金Financial support from the Simulation-based Engineering Science(Genie Par la Simulation)program funded through the CREATE program from the Natural Sciences and Engineering Research Council of Canada is gratefully acknowledged.
文摘The simulation of rarefied gasflows through complex porous media is chal-lenging due to the tortuousflow pathways inherent to such structures.The Lattice Boltzmann method(LBM)has been identified as a promising avenue to solveflows through complex geometries due to the simplicity of its scheme and its high parallel computational efficiency.It has been proposed to model the stress-strain relationship with the extended Navier-Stokes equations rather than attempting to directly solve the Boltzmann equation.However,a regularization technique is required tofilter out non-resolved higher-order components with a low-order velocity scheme.Although slip boundary conditions(BCs)have been proposed for the non-regularized multiple relaxation time LBM(MRT-LBM)for planar geometries,previous slip BCs have never been verified extensively with the regularization technique.In this work,following an extensive literature review on the imposition of slip BCs for rarefiedflows with the LBM,it is proven that earlier values for kinetic parameters developed to impose slip BCs are inaccurate for the regularized MRT-LBM and differ between the D2Q9 and D3Q15 schemes.The error was eliminated for planarflows and good agreement be-tween analytical solutions for arrays of cylinders and spheres was found with a wide range of Knudsen numbers.
