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Thermoelastic topology optimization for structures with temperature-dependent material properties

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Science China(Technological Sciences) 2023年第12期66卷 3488-3503页

作者： ZHENG Jing RONG XuanPei jiang chao State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body School of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China

A thermoelastic topology optimization is proposed for structures with temperature-dependent material *** from the common assumption of constant material properties in traditional thermoelastic topology optimization,the temperaturedependent material properties related to mechanical and thermal fields are taken into *** non-uniform temperature distribution of the structure is a design dependent field that may vary during the optimization,and the nonlinear heat transfer analysis is considered according to the large temperature *** on these,a thermoelastic topology optimization model considering temperature-dependent material properties is *** sensitivities with respect to the design variables are derived and the Method of Moving Asymptotes(MMA)algorithm is used to update the topological design variables.A cooperation platform based on MATLAB and ABAQUS is developed for the proposed thermoelastic topology optimization method to deal with problems with arbitrary domains for the design of complex engineering *** typical numerical examples are given to illustrate the effectiveness of the proposed method and show the important influence of the temperaturedependent material properties.

关键词： thermoelastic topology optimization nonlinear heat transfer temperature-dependent material properties

Anisotropy reduction and mechanical property improvement of additively manufactured stainless steel based on cyclic phase transformation

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Journal of Materials Science & Technology 2024年第17期184卷 1-14页

作者： Bochuan Li Kang Xu chao jiang State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China Automotive Engineering Research Institute Byd Auto Industry Company LimitedShenzhen 518000China

Owing to the special layer-by-layer deposition process of directed energy deposition(DED),columnar coarse grains,produced by cyclic reheating with intrinsic directional heat flow along the building direc-tion,are difficult to *** grains result in strong anisotropic characteristics with poor mechanical properties,which restrict the application of DED *** work proposes a novel fabrication strat-egy based on the cyclic-phase-transformation behavior,which can reduce the anisotropy and improve the mechanical properties of DED-printed stainless *** this fabrication strategy,316 L powder(austenitic stainless steel)and 17-4PH powder(martensitic stainless steel)were mixed in different mass ratios to fabricate five types of DED-printed stainless *** the five samples,P70(mixture of 70 wt%17-4PH powder and 30 wt%316 L powder)showed the weakest anisotropy and the best mechanical properties,which can be attributed to the cyclic phase transformation under cyclic reheating treatment and the transformation-induced plasticity(TRIP)effect over a wide range of strains,***-pared with the pure 316 L printed material,the tensile test results of P70 showed that the yield strength(YS)and ultimate tensile strength(UTS)increased by 35.4%and 34.5%,respectively,whereas the uniform elongation(UE)and total elongation(TE)were improved by 63.9%and 31.4%,*** addition,the strength-ductility balance(UTS×UE)increased by as much as 120.4%.The proposed fabrication strategy is expected to reduce the anisotropy in other materials that undergo cyclic-phase-transformation phe-nomena during additive manufacturing.

关键词： Directed energy deposition Anisotropy reduction Cyclic phase transformation Mechanical properties

Spectrum analysis of interval process model and its application in uncertain vibration analysis

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Science China(Technological Sciences) 2024年第8期67卷 2549-2564页

作者： LI JinWu jiang chao NI BingYu State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China

In recent years, the authors have extended the traditional interval method into the time dimension to develop a new mathematical tool called the “interval process model” for quantifying time-varying or dynamic uncertainties. This model employs upper and lower bounds instead of precise probability distributions to quantify uncertainty in a parameter at any given time point. It is anticipated to complement the conventional stochastic process model in the coming years owing to its relatively low dependence on experimental samples and ease of understanding for engineers. Building on our previous work, this paper proposes a spectrum analysis method to describe the frequency domain characteristics of an interval process, further strengthening the theoretical foundation of the interval process model and enhancing its applicability for complex engineering problems. In this approach, we first define the zero midpoint function interval process and its auto/cross-power spectral density(PSD) functions. We also deduce the relationship between the auto-PSD function and the auto-covariance function of the stationary zero midpoint function interval process. Next, the auto/cross-PSD function matrices of a general interval process are defined, followed by the introduction of the concepts of PSD function matrix and cross-PSD function matrix for interval process vectors. The spectrum analysis method is then applied to random vibration problems, leading to the creation of a spectrum-analysis-based interval vibration analysis method that determines the PSD function for the system displacement response under stationary interval process excitations. Finally, the effectiveness of the formulated spectrum-analysis-based interval vibration analysis approach is verified through two numerical examples.

关键词： interval process spectrum analysis power spectral density(PSD) time-varying uncertainty uncertain vibration analysis

Analytical long-term evolution and perturbation compensation models for BeiDou MEO satellites

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Chinese Journal of Aeronautics 2018年第2期31卷 330-338页

作者： Li FAN Min HU chao jiang School of Aerospace Engineering Tsinghua University Beijing 100084 China Space Engineering University Beijing 101416 China College of Aerospace Science and Engineering National University of Defense Technology Changsha 410073 China

The current paper establishes the analytical models of the long-term evolution and perturbation compensation strategy for Medium Earth Orbits（MEO）shallow-resonant navigation constellation,with application to the Chinese Bei Dou Navigation Satellite System（BDS）.The long-term perturbation model for the relative motion is developed based on the Hamiltonian model,and the long-term evolution law is *** relationship between the control boundary of the constellation and the offset of the orbital elements is analyzed,and a general analytical method for calculating the offset of the orbit elements is *** analytical model is further improved when the luni-solar perturbations are *** long-term evolutions of the BDS MEO constellation within 10 years are illustrated,and the effectiveness of the proposed analytical perturbation compensation calculation approach is compared with the traditional numerical *** found the fundamental reason for the nonlinear variations of the relative longitude of ascending node and the mean argument of latitude is the long-periodic variations of the orbital inclination due to the luni-solar *** proposed analytical approach can avoid the numerical iterations,and reveal the essential relationship between the orbital element offsets and the secular drifts of the constellation ***,there is no need for maintaining the BDS MEO constellation within 10 years while using the perturbation compensation method.

关键词： BeiDou Navigation Satellite System (BDS) Long-term evolution Luni-solar perturbations Medium Earth Orbits(MEO) Perturbation compensation

An efficient technique for recovering responses of parameterized structural dynamic problems

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Acta Mechanica Sinica 2011年第5期27卷 757-766页

作者： Zheng Zhang Xu Han chao jiang State Key Laboratory of Advanced Designand Manufacturing for Vehicle Body College of Mechanical and Vehicle EngineeringHunan University 410082 Changsha China

In this article,an effective technique is developed to efficiently obtain the output responses of parameterized structural dynamic *** technique is based on the conception of reduced basis method and the usage of linear interpolation *** original problem is projected onto the reduced basis space by linear interpolation projection,and subsequently an associated interpolation matrix is *** ensure the largest nonsingularity,the interpolation matrix needs to go through a timenode choosing process,which is developed by applying the angle of vector *** a part of this technique,error estimation is recommended for achieving the computational error *** ensure the successful performance of this technique,the offline-online computational procedures are conducted in practical *** numerical examples demonstrate the accuracy and efficiency of the presented method.

关键词： Reduced basis method · Structural dynamic response · Real-time computation · Linear interpolation · Fast Fourier transform

The Linear Unicyclic Hypergraph with the Second or Third Largest Spectral Radius

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Acta Mathematica Sinica,English Series 2020年第10期36卷 1140-1150页

作者： chao DING Yi Zheng FAN jiang chao WAN School of Mathematics and Physics Anqing Normal UniversityAnqing 246133P.R.China School of Mathematical Sciences Anhui UniversityHefei 230601P.R.China

The spectral radius of a uniform hypergraph is defined to be that of the adjacency tensor of the *** is known that the unique unicyclic hypergraph with the largest spectral radius is a nonlinear hypergraph,and the unique linear unicyclic hypergraph with the largest spectral radius is a power *** this paper we determine the unique linear unicyclic hypergraph with the second or third largest spectral radius,where the former hypergraph is a power hypergraph and the latter hypergraph is a non-power hypergraph.

关键词： Linear unicyclic hypergraph adjacency tensor spectral radius weighted incident matrix

Spatially diff erentiated changes in regional climate and underlying drivers in southwestern China

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Journal of Forestry Research 2022年第3期33卷 755-765页

作者： Meng Wang chao jiang Osbert Jianxin Sun School of Ecology and Nature Conservation Beijing Forestry UniversityBeijing100083People’s Republic of China Institute of Forestry and Climate Change Research Beijing Forestry UniversityBeijing100083People’s Republic of China

The climate in Southwest China are predominantly under the influences of three contrasting climate systems, namely the East Asian monsoon, the South Asian monsoon, and the westerlies. However, it is unclear if the diversified climate systems, in combination with the complex terrain and varying vegetation types, would result in contrasting patterns of changes in climate across the region. Based on the CRU TS data for the period 1901−2017, we examined the spatiotemporal characteristics of the regional climate, and identified types of climate change patterns and drivers. Overall, the region experienced significant increases in annual mean temperature during 1901−2017, with occurrence of a significant turning point in 1954 for a more pronounced warming (0.16 ℃/10 a). The annual precipitation fluctuated greatly over the study period without apparent trend, albeit the occurrence of a significant turning point in 1928 for a slight increase in the later period (1.19 mm/10 a). Spatially the multi-year averages of selective climate variables during 1901–2017 displayed a trend of decreases from southeast to northwest, but with increasing variability. We identified five major climate change types across the study region, including warmer (T^(+)), drier (P^(−)), warmer-drier (T^(+)P^(−)), warmer-wetter (T^(+)P^(+)), and no significant changes (NSC). The type T^(+)P^(+) mainly occurred in the western parts over the plateau sub-frigid semiarid ecozone (77.0%) and the plateau sub-frigid semihumid ecozone (19.9%). The central parts of the region are characterized by the type T^(+), corresponding to six ecozones, including the mid-subtropical humid ecozone (33.1%), the plateau temperate humid-semihumid ecozone (28.8%), the plateau sub-rigid semihumid ecozone (9.5%), the southern subtropical humid ecozone (8.1%), the plateau sub-frigid arid ecozone (7.3%), and the plateau temperate semiarid ecozone (6.6%). No significant change in climate was detected for the eastern parts over the mi

关键词： Climate change Ecozone Regional climate Topography Vegetation

Solving the time-dependent Schrödinger equation by combining smooth exterior complex scaling and Arnoldi propagator

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Chinese Physics B 2022年第1期31卷 227-234页

作者： Shun Wang Wei-chao jiang College of Physics and Optoelectronic Engineering Shenzhen UniversityShenzhen 518060China

Abstract We develop a highly efficient scheme for numerically solving the three-dimensional time-dependent Schrödinger equation of the single-active-electron atom in the field of laser pulses by combining smooth exterior complex scaling(SECS)absorbing method and Arnoldi propagation *** combination has not been reported in the *** proposed scheme is particularly useful in the applications involving long-time wave *** SECS is a wonderful absorber,but its application results in a non-Hermitian Hamiltonian,invalidating propagators utilizing the Hermitian symmetry of the *** demonstrate that the routine Arnoldi propagator can be modified to treat the non-Hermitian *** efficiency of the proposed scheme is checked by tracking the time-dependent electron wave packet in the case of both weak extreme ultraviolet(XUV)and strong infrared(IR)laser *** perfect absorption and stable propagation are observed.

关键词： time-dependent Schrödinger equation(TDSE) smooth exterior complex scaling(SECS)absorb-ing method Arnoldi propagator

Cu/photoredox-catalyzed decarboxylative radical C(sp^(3))–C(sp^(3))cross-coupling reactions

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Science China Chemistry 2023年第10期66卷 2858-2862页

作者： chao jiang Pinhong Chen Guosheng Liu State Key Laboratory of Organometallic Chemistry and Shanghai Hongkong Joint Laboratory in Chemical Synthesis Center for Excellence in Molecular SynthesisShanghai Institute of Organic ChemistryUniversity of Chinese Academy of SciencesChinese Academy of SciencesShanghai 200032China

A radical decarboxylative C(sp^(3))–C(sp^(3))cross-coupling of NHPI esters and cyclopropanols was developed by combining photocatalysis and copper catalysis,which presents the efficient access toβ-benzyl ketones in excellent ***-4′-one used as the ligand is vital for the reaction,which could facilitate the capture of benzylic radicals by alkyl-copper species generated from copper-catalyzed ring-opening of *** reaction exhibited broad substrate scope and wide functional group compatibility,providing an alternative approach for C(sp^(3))–C(sp^(3))bond formation.

关键词： copper catalysis C(sp^(3))-C(sp^(3))cross-coupling photoredox NHPI ester cyclopropanol