Quasi-periodic solutions with multiple base frequencies exhibit the feature of 2π-periodicity with respect to each of the hyper-time variables.However,it remains a challenge work,due to the lack of effective solution...Quasi-periodic solutions with multiple base frequencies exhibit the feature of 2π-periodicity with respect to each of the hyper-time variables.However,it remains a challenge work,due to the lack of effective solution methods,to solve and track the quasi-periodic solutions with multiple base frequencies until now.In this work,a multi-steps variable-coefficient formulation is proposed,which provides a unified framework to enable either harmonic balance method or collocation method or finite difference method to solve quasi-periodic solutions with multiple base frequencies.For this purpose,a method of alternating U and S domain is also developed to efficiently evaluate the nonlinear force terms.Furthermore,a new robust phase condition is presented for all of the three methods to make them track the quasi-periodic solutions with prior unknown multiple base frequencies,while the stability of the quasi-periodic solutions is assessed by mean of Lyapunov exponents.The feasibility of the constructed methods under the above framework is verified by application to three nonlinear systems.展开更多
The dissolution of iron from the cathode and electrode/electrolyte interface(EEI)during long cycles significantly accelerates the aging process of LiFePO_(4)(LFP)/graphite batteries;there is a lack of systematic under...The dissolution of iron from the cathode and electrode/electrolyte interface(EEI)during long cycles significantly accelerates the aging process of LiFePO_(4)(LFP)/graphite batteries;there is a lack of systematic understanding of the spatial distribution of the EEI interface layer and the dissolve of Fe ions,especially in terms of the mechanism of the cathode-electrolyte interphase(CEI),solid electrolyte interphase(SEI),and iron dissolution.In this study,aged cells were subjected to continuous activation with constant current and multi-step segmented indirect activation(IA)and analyzed for capacity fade,impedance growth,and active Li^(+)mass loss at the EEI and nanoscale levels.The interaction between dissolved Fe^(2+)and the EEI in LFP/graphite pouch batteries was proposed and verified.The findings indicate that during IA process,the electric field facilitates the migration of solvated ions toward the electrodes,while simultaneously inhibiting the formation of organic species such as ROCO_(2)Li.The SEI primarily consists of a mixture of organic and inorganic small molecules,forming a continuous and uniform film on the electrode surface.This study demonstrates that IA favors the formation of a uniform EEI and offers constructive insights for advancing accelerated lifetime prediction strategies in lithium-ion batteries.展开更多
The accurate mechanical analysis of thick-walled pressure vessel structures composed of advanced materials,such as hyperelastic and functionally graded materials(FGMs),is critical for ensuring their safety and optimiz...The accurate mechanical analysis of thick-walled pressure vessel structures composed of advanced materials,such as hyperelastic and functionally graded materials(FGMs),is critical for ensuring their safety and optimizing their design.However,conventional numerical methods can face challenges with the non-linearities inherent in hyperelasticity and the complex spatial variations in FGMs.This paper presents a novel hybrid numerical approach combining Physics-Informed Neural Networks(PINNs)with Finite Element Method(FEM)derived data for the robust analysis of thick-walled,axisymmetric,heterogeneous,hyperelastic pressure vessels with elliptical geometries.A PINN framework incorporating neo-Hookean constitutive relations is developed in MATLAB.To enhance training efficiency and accuracy,the PINN’s loss function is augmented with displacement data obtained from high-fidelity FEM simulations performed in ANSYS.The methodology is rigorously validated by comparing PINN-predicted displacement and von Mises stress fields against ANSYS benchmarks for various scenarios of FGMconfigurations(with material properties varying according to a power law)subjected to internal and external pressurization.The results demonstrate excellent agreement between the proposed hybrid PINN-FEMapproach and conventional FEMsolutions across all test cases,accurately capturing complex deformation patterns and stress concentrations.This study highlights the potential of data-augmented PINNs as an effective and accurate computational tool for tackling complex solid mechanics problems involving non-linearmaterials and significant heterogeneity,offering a promising avenue for future research in engineering design and analysis.展开更多
The dynamic evolution of fracture permeability presents a critical scientific challenge in rock masses.Understanding the mechanisms of rock mass permeability evolution is vital for engineering project design and opera...The dynamic evolution of fracture permeability presents a critical scientific challenge in rock masses.Understanding the mechanisms of rock mass permeability evolution is vital for engineering project design and operations.By integrating the discrete element method(DEM)with the finite element method(FEM),a numerical simulation framework for shear seepage in rough fractured shale has been developed to investigate the dynamic mechanisms of permeability evolution under varying confining pressures and during the shearing process.Numerical simulations were conducted on rough fractured samples under effective confining pressures ranging from 5 MPa to 20 MPa to monitor the aperture and permeability evolution of the fracture.The results of the numerical simulation are consistent with the experimental observations,indicating that both the shearing process and confining pressure significantly influence permeability.Moreover,the magnitude of the confining pressure is a crucial factor influencing the trend in permeability changes.Under a confining pressure of 5 MPa,fracture permeability initially increases significantly but decreases post-shearing.In contrast,a continuous decrease in fracture permeability is observed when the confining pressure exceeds 10 MPa.The results of the shear numerical simulation indicate that the confining pressure restricts fracture dilation during shearing,promotes the generation of rock debris,and decreases both the permeability and transmissivity of the fracture.The wear results obtained from numerical simulations are consistent with the experimental patterns and correlate with the joint roughness coefficient(JRC).This study proposed an effective numerical simulation method to reveal the evolution mechanism of fracture flow capacity,taking into account the wear of the fracture surface in shear simulations and the initial stress state of the rock in seepage simulations.This research explains the permeability evolution mechanism of fractured shale from a microscopic perspective,and the proposed numerical simulation method for shear seepage provides a powerful means to uncover the dynamic evolution mechanisms governing fracture permeability.展开更多
坝体抗震设计和评估需要准确计算无限水库动力响应.基于比例边界有限元法(scaled boundary finite element method,SBFEM)力学推导技术,推导了顺河向地震激励下等横截面无限水域频域响应计算公式,利用Fourier逆变换建立了时域响应控制方...坝体抗震设计和评估需要准确计算无限水库动力响应.基于比例边界有限元法(scaled boundary finite element method,SBFEM)力学推导技术,推导了顺河向地震激励下等横截面无限水域频域响应计算公式,利用Fourier逆变换建立了时域响应控制方程,通过线性叠加推导了顺河、横河、竖直三向组合地震激励下的无限水域频域和时域响应的SBFEM计算公式.结合有限元法,建立了无限水库频域和时域响应的FEM-SBFEM耦合方程.分析了地震激励下的二维、三维等横截面无限水库频域、时域响应,数值验证了所建立计算公式的正确性.所发展的FEM-SBFEM公式体系可推广应用于库底库岸具有吸收性的、横截面有任意几何形状的无限水库谐响应及瞬态响应分析.展开更多
为了模拟喷丸强化过程,实现喷丸强化效果快速预测,基于Abaqus软件采用离散元法-有限元法(Discrete Element Method-Finite Element Method,DEM-FEM)耦合建立随机多丸粒喷丸强化模型,并以TC4钛合金为研究对象,通过喷丸强化试验来验证耦...为了模拟喷丸强化过程,实现喷丸强化效果快速预测,基于Abaqus软件采用离散元法-有限元法(Discrete Element Method-Finite Element Method,DEM-FEM)耦合建立随机多丸粒喷丸强化模型,并以TC4钛合金为研究对象,通过喷丸强化试验来验证耦合模型的准确性。采用Box-Behnken设计(Box-Behnken Design,BBD)法,针对弹丸大小、喷丸速度和喷丸覆盖率3个工艺参数设计了三因素三水平的喷丸仿真试验方案,采用仿真分析获得表面残余应力值及表面粗糙度值,并通过Design-Expert软件进行数值拟合,最终得到喷丸工艺参数与表面残余应力和表面粗糙度之间的函数模型,采用响应面法分析弹丸大小、喷丸速度、喷丸覆盖率三因素之间的交互作用以及对喷丸强化效果的影响规律。结果表明,响应面预测模型结果与仿真计算结果误差低于5%,所建立的响应面预测模型具有较高的近似精度和可靠性,利用此模型可实现喷丸强化效果的有效预测。展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12172267 and 12302014).
文摘Quasi-periodic solutions with multiple base frequencies exhibit the feature of 2π-periodicity with respect to each of the hyper-time variables.However,it remains a challenge work,due to the lack of effective solution methods,to solve and track the quasi-periodic solutions with multiple base frequencies until now.In this work,a multi-steps variable-coefficient formulation is proposed,which provides a unified framework to enable either harmonic balance method or collocation method or finite difference method to solve quasi-periodic solutions with multiple base frequencies.For this purpose,a method of alternating U and S domain is also developed to efficiently evaluate the nonlinear force terms.Furthermore,a new robust phase condition is presented for all of the three methods to make them track the quasi-periodic solutions with prior unknown multiple base frequencies,while the stability of the quasi-periodic solutions is assessed by mean of Lyapunov exponents.The feasibility of the constructed methods under the above framework is verified by application to three nonlinear systems.
基金supported by the National Key R&D Program of China(2021YFB2401800)the support from Beijing Nova Program(20230484241)+2 种基金the support from the China Postdoctoral Science Foundation(2024M754084)the Postdoctoral Fellowship Program of CPSF(GZB20230931)the support from Initial Energy Science&Technology Co.,Ltd(IEST)。
文摘The dissolution of iron from the cathode and electrode/electrolyte interface(EEI)during long cycles significantly accelerates the aging process of LiFePO_(4)(LFP)/graphite batteries;there is a lack of systematic understanding of the spatial distribution of the EEI interface layer and the dissolve of Fe ions,especially in terms of the mechanism of the cathode-electrolyte interphase(CEI),solid electrolyte interphase(SEI),and iron dissolution.In this study,aged cells were subjected to continuous activation with constant current and multi-step segmented indirect activation(IA)and analyzed for capacity fade,impedance growth,and active Li^(+)mass loss at the EEI and nanoscale levels.The interaction between dissolved Fe^(2+)and the EEI in LFP/graphite pouch batteries was proposed and verified.The findings indicate that during IA process,the electric field facilitates the migration of solvated ions toward the electrodes,while simultaneously inhibiting the formation of organic species such as ROCO_(2)Li.The SEI primarily consists of a mixture of organic and inorganic small molecules,forming a continuous and uniform film on the electrode surface.This study demonstrates that IA favors the formation of a uniform EEI and offers constructive insights for advancing accelerated lifetime prediction strategies in lithium-ion batteries.
文摘The accurate mechanical analysis of thick-walled pressure vessel structures composed of advanced materials,such as hyperelastic and functionally graded materials(FGMs),is critical for ensuring their safety and optimizing their design.However,conventional numerical methods can face challenges with the non-linearities inherent in hyperelasticity and the complex spatial variations in FGMs.This paper presents a novel hybrid numerical approach combining Physics-Informed Neural Networks(PINNs)with Finite Element Method(FEM)derived data for the robust analysis of thick-walled,axisymmetric,heterogeneous,hyperelastic pressure vessels with elliptical geometries.A PINN framework incorporating neo-Hookean constitutive relations is developed in MATLAB.To enhance training efficiency and accuracy,the PINN’s loss function is augmented with displacement data obtained from high-fidelity FEM simulations performed in ANSYS.The methodology is rigorously validated by comparing PINN-predicted displacement and von Mises stress fields against ANSYS benchmarks for various scenarios of FGMconfigurations(with material properties varying according to a power law)subjected to internal and external pressurization.The results demonstrate excellent agreement between the proposed hybrid PINN-FEMapproach and conventional FEMsolutions across all test cases,accurately capturing complex deformation patterns and stress concentrations.This study highlights the potential of data-augmented PINNs as an effective and accurate computational tool for tackling complex solid mechanics problems involving non-linearmaterials and significant heterogeneity,offering a promising avenue for future research in engineering design and analysis.
基金funded by the Joint Funds of the National Natural Science Foundation of China(Grant No.U23A20671)the Major Project of Inner Mongolia Science and Technology(Grant No.2021ZD0034)the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engi-neering(Grant No.Z021003).
文摘The dynamic evolution of fracture permeability presents a critical scientific challenge in rock masses.Understanding the mechanisms of rock mass permeability evolution is vital for engineering project design and operations.By integrating the discrete element method(DEM)with the finite element method(FEM),a numerical simulation framework for shear seepage in rough fractured shale has been developed to investigate the dynamic mechanisms of permeability evolution under varying confining pressures and during the shearing process.Numerical simulations were conducted on rough fractured samples under effective confining pressures ranging from 5 MPa to 20 MPa to monitor the aperture and permeability evolution of the fracture.The results of the numerical simulation are consistent with the experimental observations,indicating that both the shearing process and confining pressure significantly influence permeability.Moreover,the magnitude of the confining pressure is a crucial factor influencing the trend in permeability changes.Under a confining pressure of 5 MPa,fracture permeability initially increases significantly but decreases post-shearing.In contrast,a continuous decrease in fracture permeability is observed when the confining pressure exceeds 10 MPa.The results of the shear numerical simulation indicate that the confining pressure restricts fracture dilation during shearing,promotes the generation of rock debris,and decreases both the permeability and transmissivity of the fracture.The wear results obtained from numerical simulations are consistent with the experimental patterns and correlate with the joint roughness coefficient(JRC).This study proposed an effective numerical simulation method to reveal the evolution mechanism of fracture flow capacity,taking into account the wear of the fracture surface in shear simulations and the initial stress state of the rock in seepage simulations.This research explains the permeability evolution mechanism of fractured shale from a microscopic perspective,and the proposed numerical simulation method for shear seepage provides a powerful means to uncover the dynamic evolution mechanisms governing fracture permeability.
文摘泥石流作为高破坏性混合流体,其携带的块石对框架结构的冲击机制尚未得到充分研究。为揭示含块石泥石流冲击框架结构的动力响应与损伤机制,基于光滑粒子流体动力学-离散元法-有限元法(smoothed particle hydrodynamics-discrete element method-finite element method,SPH-DEM-FEM)耦合数值方法,构建流体-块石-结构的多耦合数值模型,模拟不同冲击速度和角度下框架结构的损伤过程,并结合两相溃坝试验来验证模型有效性。研究表明:泥石流冲击导致结构损伤经历“接触-扩散-反弹-堆积/冲击”四个阶段,当冲击速度超过6.00 m/s时,结构产生不可恢复损伤,且块石阻隔作用使流体上部冲击力大于下部,引发结构中部最先发生集中损伤;此外,冲击力峰值随速度和角度增大呈非线性增长,10.00 m/s与90°工况下框架柱底冲击力达497.17 kN,超过结构抗冲击承载力;最后,数值模拟与经验公式所得冲击力结果误差在13.95%~29.00%,数量级一致,验证了模型可靠性。研究结果可为泥石流高发区框架结构的抗冲击设计提供参考。
文摘坝体抗震设计和评估需要准确计算无限水库动力响应.基于比例边界有限元法(scaled boundary finite element method,SBFEM)力学推导技术,推导了顺河向地震激励下等横截面无限水域频域响应计算公式,利用Fourier逆变换建立了时域响应控制方程,通过线性叠加推导了顺河、横河、竖直三向组合地震激励下的无限水域频域和时域响应的SBFEM计算公式.结合有限元法,建立了无限水库频域和时域响应的FEM-SBFEM耦合方程.分析了地震激励下的二维、三维等横截面无限水库频域、时域响应,数值验证了所建立计算公式的正确性.所发展的FEM-SBFEM公式体系可推广应用于库底库岸具有吸收性的、横截面有任意几何形状的无限水库谐响应及瞬态响应分析.
文摘为了模拟喷丸强化过程,实现喷丸强化效果快速预测,基于Abaqus软件采用离散元法-有限元法(Discrete Element Method-Finite Element Method,DEM-FEM)耦合建立随机多丸粒喷丸强化模型,并以TC4钛合金为研究对象,通过喷丸强化试验来验证耦合模型的准确性。采用Box-Behnken设计(Box-Behnken Design,BBD)法,针对弹丸大小、喷丸速度和喷丸覆盖率3个工艺参数设计了三因素三水平的喷丸仿真试验方案,采用仿真分析获得表面残余应力值及表面粗糙度值,并通过Design-Expert软件进行数值拟合,最终得到喷丸工艺参数与表面残余应力和表面粗糙度之间的函数模型,采用响应面法分析弹丸大小、喷丸速度、喷丸覆盖率三因素之间的交互作用以及对喷丸强化效果的影响规律。结果表明,响应面预测模型结果与仿真计算结果误差低于5%,所建立的响应面预测模型具有较高的近似精度和可靠性,利用此模型可实现喷丸强化效果的有效预测。
