This paper introduces a computationally efficient global sensitivity analysis method for quantifying the influence of uncertain clamp support conditions on the natural frequencies of aero-engine pipe systems.The dynam...This paper introduces a computationally efficient global sensitivity analysis method for quantifying the influence of uncertain clamp support conditions on the natural frequencies of aero-engine pipe systems.The dynamic model is based on a three-dimensional Timoshenko beam finite element formulation,with clamps represented as distributed spring elements possessing anisotropic stiffness.To overcome the prohibitive cost of traditional Monte Carlo simulation,the multiplicative dimensional reduction method(M-DRM)is integrated with variance decomposition theory.This approach approximates the high-dimensional frequency response function as a product of univariate components,enabling rapid computation of Sobol’sensitivity indices with a computational cost reduced by three orders of magnitude.Numerical case studies on a planar Z-shaped pipe and a spatial series-parallel configuration reveal that clamp position parameters dominate the system’s natural frequency characteristics.For critical clamps,Sobol’indices exceed 0.8 across multiple vibration modes,whereas stiffness parameters exhibit negligible influence.The proposed methodology provides a rigorous and efficient tool for identifying dominant uncertainty sources,guiding tolerance allocation in manufacturing,and informing robust support design for vibration-sensitive piping systems.展开更多
The cubic stiffness force model(CSFM)and Bouc-Wen model(BWM)are introduced and compared innovatively.The unknown coefficients of the nonlinear models are identified by the genetic algorithm combined with experiments.B...The cubic stiffness force model(CSFM)and Bouc-Wen model(BWM)are introduced and compared innovatively.The unknown coefficients of the nonlinear models are identified by the genetic algorithm combined with experiments.By fitting the identified nonlinear coefficients under different excitation amplitudes,the nonlinear vibration responses of the system are predicted.The results show that the accuracy of the BWM is higher than that of the CSFM,especially in the non-resonant region.However,the optimization time of the BWM is longer than that of the CSFM.展开更多
Dielectric ceramics are essential components in communication systems that operate within the microwave frequency range.In high-density packages,dielectric substrates ceramics must possess high thermal conductivity to...Dielectric ceramics are essential components in communication systems that operate within the microwave frequency range.In high-density packages,dielectric substrates ceramics must possess high thermal conductivity to efficiently dissipate heat.However,achieving adequate thermal conductivity(k)in ceramics sintered at low temperatures is challenging.In this study,we employed the cold sintering process(CSP)to fabricate Li_(2)MoO_(4)-x%Al_(2)O_(3)(0≤x≤80,in volume)ceramics under 200 MPa pressure at 150℃.The Li_(2)MoO_(4)-40%Al_(2)O_(3)composite exhibited significantly enhanced k of 5.4 W·m^(-1)·K^(-1),an 80%increase compared to pure Li_(2)MoO_(4)ceramic with k of 3 W·m^(-1)·K^(-1).At 40%Al_(2)O_(3)content,the Li_(2)MoO_(4)eAl_(2)O_(3)ceramic demonstrated notable microwave properties(ε~6.67,Q×f~17,846 GHz,tf~^(-1)05×10^(-6)℃^(-1)).Additionally,simulation of a microstrip patch antenna for 5 GHz applications using Li_(2)MoO_(4)-20%Al_(2)O_(3)ceramic as dielectric substrate via Finite Element Simulation software showed excellent performance,with radiation efficiency exceeding 99%and low return loss(S_(11)<-30 dB)at both 4.9 GHz and 28.0 GHz center frequencies.These findings underscore the suitability of Li_(2)MoO_(4)eAl_(2)O_(3)ceramics for microwave dielectric substrate.展开更多
基金funded by the Major Projects of Aero-Engines and Gas Turbines grant number J2019-I-0008-0008.
文摘This paper introduces a computationally efficient global sensitivity analysis method for quantifying the influence of uncertain clamp support conditions on the natural frequencies of aero-engine pipe systems.The dynamic model is based on a three-dimensional Timoshenko beam finite element formulation,with clamps represented as distributed spring elements possessing anisotropic stiffness.To overcome the prohibitive cost of traditional Monte Carlo simulation,the multiplicative dimensional reduction method(M-DRM)is integrated with variance decomposition theory.This approach approximates the high-dimensional frequency response function as a product of univariate components,enabling rapid computation of Sobol’sensitivity indices with a computational cost reduced by three orders of magnitude.Numerical case studies on a planar Z-shaped pipe and a spatial series-parallel configuration reveal that clamp position parameters dominate the system’s natural frequency characteristics.For critical clamps,Sobol’indices exceed 0.8 across multiple vibration modes,whereas stiffness parameters exhibit negligible influence.The proposed methodology provides a rigorous and efficient tool for identifying dominant uncertainty sources,guiding tolerance allocation in manufacturing,and informing robust support design for vibration-sensitive piping systems.
文摘The cubic stiffness force model(CSFM)and Bouc-Wen model(BWM)are introduced and compared innovatively.The unknown coefficients of the nonlinear models are identified by the genetic algorithm combined with experiments.By fitting the identified nonlinear coefficients under different excitation amplitudes,the nonlinear vibration responses of the system are predicted.The results show that the accuracy of the BWM is higher than that of the CSFM,especially in the non-resonant region.However,the optimization time of the BWM is longer than that of the CSFM.
基金supported by National Natural Science Foundation of China(No.52361165625)Shenzhen Science and Technology Program,Guangdong Province,China(Nos.KQTD20180411143514543,JCYJ20220818100613029,and JSGGZD20220822095603006)We acknowledge the support of Project 2019CX01C079 of Guangdong Province。
文摘Dielectric ceramics are essential components in communication systems that operate within the microwave frequency range.In high-density packages,dielectric substrates ceramics must possess high thermal conductivity to efficiently dissipate heat.However,achieving adequate thermal conductivity(k)in ceramics sintered at low temperatures is challenging.In this study,we employed the cold sintering process(CSP)to fabricate Li_(2)MoO_(4)-x%Al_(2)O_(3)(0≤x≤80,in volume)ceramics under 200 MPa pressure at 150℃.The Li_(2)MoO_(4)-40%Al_(2)O_(3)composite exhibited significantly enhanced k of 5.4 W·m^(-1)·K^(-1),an 80%increase compared to pure Li_(2)MoO_(4)ceramic with k of 3 W·m^(-1)·K^(-1).At 40%Al_(2)O_(3)content,the Li_(2)MoO_(4)eAl_(2)O_(3)ceramic demonstrated notable microwave properties(ε~6.67,Q×f~17,846 GHz,tf~^(-1)05×10^(-6)℃^(-1)).Additionally,simulation of a microstrip patch antenna for 5 GHz applications using Li_(2)MoO_(4)-20%Al_(2)O_(3)ceramic as dielectric substrate via Finite Element Simulation software showed excellent performance,with radiation efficiency exceeding 99%and low return loss(S_(11)<-30 dB)at both 4.9 GHz and 28.0 GHz center frequencies.These findings underscore the suitability of Li_(2)MoO_(4)eAl_(2)O_(3)ceramics for microwave dielectric substrate.
