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Application of artificial intelligence in composite materials
ZHANG Junming, YANG Weidong, LI Yan
 doi: 10.6052/1000-0992-21-019
Abstract(529) HTML(147) PDF(206)
Composite materials have become the major materials of light-weight structure due to their light weight, high strength, high modulus, and strong designability. However, as the component, structure and requirements of capability become increasingly complex, traditional research methods based on experiment, theoretical modeling and numerical simulation meet lots of new problems in the properties prediction, design optimization, manufacturing and processing of composite materials. Insufficient experimental observation, lacking theoretical model, constrained numerical simulation and difficult conclusion validation have seriously restricted the development of advanced composite materials in the future-oriented engineering. Instead of the mathematical models used by mechanics, data-driven models are used in the Artificial Intelligence. It directly establishes the complex relationship between variables from high-dimensional and high-throughput data, then captures the laws that are difficult to be discovered by traditional mechanical method, shows natural advantages in simulation, prediction, optimization in complex systems. It has become the development trend in the field of composite materials to find new solutions to the problems faced by traditional methods through Artificial Intelligence. In this paper, the status of properties prediction, design optimization, manufacturing and health monitoring is introduced. The future development direction of this field is discussed.
Substructuring multi-resolution topology optimization with template
HUANG Mengcheng, HUO Wendong, LIU Chang, YANG Dongsheng, HUANG Jia, DU Zongliang, GUO Xu
 doi: 10.6052/1000-0992-21-030
Abstract(188) HTML(88) PDF(58)
In the multi-resolution topology optimization (MTOP) method, by decoupling the finite element mesh and discretization of density field, the finite element analysis is carried out with a coarser mesh (i.e., super-elements), and the computational cost is thus greatly reduced in the process of topology optimization. However, the elemental stiffness matrix is calculated each iteration using the average density of super-elements, and this treatment is actually not only inaccurate but also leads to the checkerboard phenomenon and QR patterns when the filter radius is relatively small. In order to alleviate such issues, the super-element is treated as a substructure and the corresponding elemental stiffness matrix is obtained using static condensation. Furthermore, a template library is developed for the substructure based on its density distribution during the topology optimization process. By this means, the elemental stiffness matrix is not required to be calculated repeatedly, the accuracy of the MTOP method is improved significantly and the checkerboard patterns are effectively inhibited as well.
The fatigue failure behaviors of ferroelectric materials
CHEN Yu, ZHOU Huajiang, XIE Shaoxiong, XU Qian, ZHU Jianguo, WANG Qingyuan
 doi: 10.6052/1000-0992-20-030
Abstract(443) HTML(77) PDF(122)
In the fields of some major equipment technology such as aerospace and nuclear power generation, as the sensitive elements of high-temperature transforming/actuating/energy harvesting devices, the fatigue failure of bismuth layered ferroelectric (BLSF) ceramics seriously restrict the improvement in the life and reliability of devices. This paper is set in the urgent demand of BLSF ceramics, sticking to the fatigue crack growth, domain polarization switching, and interaction mechanisms. It reviewed the progress in the fatigue failure behaviors of ferroelectric materials subjected to three kinds of loadings, including heat, stress, electricity, and their coupled effects. This paper also discusses the research directions of ferroelectric materials in the future according to their new developments and applications. This work aims at providing references for the design of ferroelectric/piezoelectric devices with long life and high performance.
Review of the measurement methods for elastic moduli and internal frictions of solids
XIE Mingyu, LI Faxin
 doi: 10.6052/1000-0992-21-013
Abstract(216) HTML(111) PDF(78)
Elastic moduli and internal frictions are fundamental properties of solid materials and their measurement accuracy and convenience are of great significance to industrial production and scientific research. This paper reviews the measurement methods of elastic moduli and internal frictions of solid materials in the past 100 years, which can be divided into four types: quasi-static method, low frequency method, resonance method and wave propagation method. Firstly, the measurement principle of each type method is introduced and evaluated. Then the resonance methods, including free-free beam method, impulse excitation technique, resonant ultrasound spectrum and piezoelectric ultrasonic composite oscillator technique (PUCOT) are presented and discussed in detail. After that, a new method called modified piezoelectric ultrasonic composite oscillator technique (M-PUCOT), proposed by the current authors, are introduced. This new method is based on the principle of electromechanical impedance, and can measure the Young’s modulus/shear modulus and the related internal frictions simultaneously, accurately and quickly. Finally, the significance and prospective of this new method are discussed.
Mechanical problems of the large thrust liquid rocket engine
LI Bin, YAN Song, YANG Baofeng
 doi: 10.6052/1000-0992-21-003
Abstract(230) HTML(99) PDF(65)
According to the extreme mechanical and thermal environment of high-thrust rocket engines, the mechanical characteristics of high thrust liquid rocket engines, such as strong vibration, large static load, multi-source excitation, and complex load transfer path, are analyzed. In statics, the whole engine structural load analysis and the components static analysis method are introduced. In dynamics, the low-frequency structural dynamic model of the entire engine, the refined model updating technique and multi-source load equivalent method are introduced. For the typical engine components, the mechanical challenges faced in the development of high thrust engine are summarized, including high-temperature and high-pressure gas swing device, rotor dynamics, dynamic and static interference fluid excitation, cavitation oscillation in inducer, large range axial force balance, supersonic turbine aeroelastic, thrust chamber thermal fatigue, nozzle lateral force load, assembly pipeline fatigue fracture, etc. The mechanical requirements and future research directions are pointed out. Finally, the status of probabilistic failure analysis of the engine is briefly introduced, which provides mechanical support for the development of high-thrust liquid rocket engines.
Short-range order in multicomponent alloys
BU Yeqiang, WANG Hongtao
 doi: 10.6052/1000-0992-21-027
Abstract(138) HTML(51) PDF(32)
Numerous studies indicates that multicomponent alloys extensively possess short-range order, which place a significant impact on their performance improvement. Employing advanced transmission electron microscopy, the size, composition and structure of short-range order in multicomponent alloys can be analyzed at atomic resolution.
Progress in the analysis of debris cloud evolution: Fully based on probabilistic methods
SHU Peng, YANG Zhen, LUO Yazhong
 doi: 10.6052/1000-0992-21-002
Abstract(232) HTML(36) PDF(25)
In view of the intrinsic uncertainty of the debris cloud, a fully probabilistic framework of debris evolution is constructed. The breakup, evolution and collision of the debris cloud could be analyzed analytically, avoiding the low computational efficiency and poor robustness of numerical methods.
A review of the study on coherent structures in turbulence by the clustering method
DONG Siwei, CHENG Chen, CHEN Jianqiang, YUAN Xianxu, LI Weipeng
 doi: 10.6052/1000-0992-20-032
Abstract(308) HTML(122) PDF(8)
The intrinsic randomness of turbulence requires that the study of coherent structures has to be from the statistical point of view. The data-based clustering method is a powerful tool to realize the deep integration of coherent structures and statistics. It makes each continuous region, i.e., an individual structure, as a statistical sample. In addition, the spatial-temporal tracking method based on the spatial overlap of individual structure between consecutive snapshots makes the evolution of individual structure during its lifetime also as a statistical sample. Thus, both the kinematics and dynamics of coherent structures can be statistically described. We reviewed the history of this method and introduced the progress on Reynolds stress structures, velocity streaks, and cascades with emphasis. These results suggest that the clustering method extraordinarily extended our understanding of turbulence compared with the traditional point-wise statistics. Further prospects are also provided for future research.
Editorial Note
Special Issue for 50th Anniversary