力学进展

Development and Application of Electromagnetic Loading Expansion Ring Test Technology

, Available online

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Abstract:
Electromagnetic loading expansion ring test technology is an important means to achieve high strain rate tensile loading, capable of achieving strain rates on the order of 10^4 s^-1 for one-dimensional tensile loading. Electromagnetic Lorentz forces are uniformly applied to the expansion ring specimens as a body force, and the dynamic loading process does not involve stress wave propagation effects. Moreover, the characteristic structure of the ring specimens avoids the end grip effects seen with traditional dog-bone-shaped specimens. Therefore, electromagnetic loading expansion ring test technology is widely used in the study of the tensile mechanical behavior of materials at high strain rates. This paper first introduces the basic principles of dynamic loading expansion ring test technology, then discusses the disadvantages of explosion-driven expansion ring test technology and the advantages of electromagnetic-driven expansion ring test technology, and reviews the development history of electromagnetic loading expansion ring test technology. It then summarizes the cutting-edge research progress of electromagnetic loading expansion ring test technology in the dynamic mechanical properties of materials, dynamic fracture behavior, dynamic ductile behavior, and high-temperature adiabatic properties. Finally, it discusses the development prospects and directions of electromagnetic loading expansion ring test technology in the field of solid mechanics. This provides a relatively systematic reference for researchers engaged in the experimental technology field of dynamic mechanical behavior of materials and offers a comprehensive and systematic knowledge of the field for young researchers interested in electromagnetic loading

Research progress of biomimetic design and preparation of functional surfaces for droplet transport

LIU Ming, CHEN Shaohua

, Available online , doi: 10.6052/1000-0992-24-015

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Functional surfaces for droplet transport has important applications in green energy, medical technology, new materials and other fields, such as fog collection, drug targeted therapy, etc. The surfaces of natural creatures with specific functions of directional transport and fixed-point transfer of droplets provide excellent examples for design and preparation of functional surfaces for droplet transport, a large number of novel and flexible bionic research achievements have been arisen. Firstly, the typical surfaces of natural creatures with self-driven functions of droplet transport are summarized and the basic theories of wettability on solid surface are elaborated; then, the biomimetic research progress of functional surfaces for droplet transport based on different self-driven mechanism is reviewed, the mechanism and influencing factors of droplet transport on different functional surfaces are compared and analyzed; furthermore, the current research of the functional surface for directional transport or fixed-point transfer of droplet under the action of external field such as magnetic field, electric field, temperature field and etc. are elaborated and analyzed; finally, the applications and future directions of such biomimetic functional surfaces are summarized and prospected.

AI for PDEs in solid mechanics: A review

WANG Yizheng, ZHUANG Xiaoying, TIMON Rabczuk, LIU Yinghua

, Available online , doi: 10.6052/1000-0992-24-016

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In recent years, deep learning has become ubiquitous and is empowering various fields. In particular, the combination of artificial intelligence and traditional science (AI4Science: AI for Science) has attracted widespread attention. In the field of AI4Science, the use of artificial intelligence algorithms to solve partial differential equations (AI4PDEs) has become the focus of computational mechanics research. The core of AI4PDEs is to fuse data with equations and can solve almost any PDEs. Due to the advantages of AI4PDEs in data fusion, computational efficiency using AI4PDEs is usually increased by tens of thousands of times compared to traditional algorithms. Therefore, this article comprehensively reviews the research on AI4PDEs, summarizes the existing AI4PDEs algorithms and theories, discusses its application in solid mechanics, including forward and inverse problems, and outlines future research directions, especially the foundation model of computational mechanics. Existing algorithms of AI4PDEs include Physics-Informed Neural Networks (PINNs), Deep Energy Methods (DEM), Operator Learning, and PINO (Physics-Informed Neural Operator). AI4PDEs has numerous applications in scientific computing, and this paper focuses on application of AI4PDEs in the forward and inverse problems of solid mechanics. The forward problems include linear elasticity, elasto-plasticity, hyperelasticity, and fracture mechanics; while the inverse problems encompass the identification of material parameters, constitutive laws, defect recognition, and topology optimization. AI4PDEs represents a novel method of scientific simulation, which offers approximate solutions for specific problems by leveraging large datasets and then fine-tunes according to the specific physical equations, avoiding the need to start calculations from scratch as traditional algorithms do. Thus, AI4PDEs is a prototype for the foundation model of computational mechanics in the future, capable of significantly accelerating traditional numerical methods. We believe that utilizing artificial intelligence to empower scientific computing is not only a vital direction for the future of computation but also a dawn of humanity in scientific research, laying the foundation for mankind to reach new heights in scientific development.

Modeling of joint structure interface friction mechanics: A review

SHEN Minmin, YANG Xiaodong

, Available online , doi: 10.6052/1000-0992-24-008

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Joints, as fundamental components of industrial machinery, are pivotal for extensive research and optimization in the realm of equipment manufacturing. Currently, due to the nonlinearity, complexity, and uncertainty of joint interfaces, the behavior mechanism of cross-scale and multi-physical field complex mechanics is unclear, making it difficult to accurately predict the dynamic characteristics of joint structures and monitor their dynamic service performance. This has become a key and bottleneck that restricts precision structural dynamics analysis, high-fidelity simulation, design, optimization, and control. However, joint structures are widely used, and engineering and technical personnel have further demand for the mechanism and multifunctionality of joint structures. This article mainly reviews the analytical modeling, finite element modeling, and experimental systems of joint structure interface friction mechanics, and proposes the development trend of new joint structure design. Firstly, based on the requirements of the joint's working environment, engineering problems, and the lack of effective strength and stiffness prediction theory, this paper reviews the load types of bolted connection structures and the application of precise joint equivalent models. Secondly, several mainstream theoretical models of friction joint structures were summarized, including a constitutive model that analyzes the multi-scale physical behavior and laws of the joint interface at the micro/nano scale, a phenomenological model that derives macroscopic dynamic responses using system identification theory and methods, and a phenomenological constitutive friction model that integrates the microscopic contact mechanism of the constitutive model with the macroscopic perspective of system identification. Then, reviewing the simulation method based on the finite element and experimental methods of joint structures, which include direct finite element modeling, indirect equivalent finite element modeling, experimental benchmark systems, and anisotropic excitation joint structure experimental platforms. Finally, a new joint design concept addressing the multifunctional requirements of joint structures in the equipment field is proposed. This concept involves “transmitting static and suppressing dynamic” joint components as well as lightweight biomimetic joint components.

Progress in assessing hazards of asteroid impact on earth

DANG Leining, BAI Zhiyong, SHI Yilei, HUANG Jie

, Available online , doi: 10.6052/1000-0992-23-047

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Asteroid impact on earth poses a potential threat to humanity. Over the past 20 years, planetary defense has become a hot research area internationally, and it is also a crucial security requirement for our country. Assessing the hazards of asteroid impact on earth is a significant research topic within planetary defense. It is noted that asteroid impacts on earth exhibit characteristics of low probability, high hazard and randomness. These hazards include overpressure, thermal radiation, earthquake, tsunami, and global effects. Hazard assessment is applied in three scenarios: defense decision-making, defense implementation, and ground civil defense. The input and output of hazard assessment, the progress of numerical simulation and engineering computation in hazard assessment in terms of model, method and software, as well as the research status of the five types of hazards, are summarized. Furthermore the advancement of hypervelocity issues of earth impact by asteroid is presented. Finally, the current research limitations are identified, and prospects for future work are provided.

Wavelet-based numerical methods and their applications in computational mechanics

YANG Bing, WANG Jizeng, LIU Xiaojing, ZHOU Youhe, FENG Yonggu

, Available online , doi: 10.6052/1000-0992-24-009

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Mechanics research advances towards interdisciplinary research, cross-scale correlations, and extreme environmental impacts. Strong nonlinearity, strong discontinuity, significant multi-physics coupling, multiscale, and complex geometries have become common characteristics in solving various mechanics problems quantitatively. Long-term quantitative research indicates that one of the core ingredients for solving such problems effectively lies in constructing numerical methods that can accurately identify, locate, capture, and separate different scale characteristics especially small-scale local characteristics, under multiscale and nonlinearity circumstances. These numerical methods should also possess the capacity to isolate and decouple the large-scale lower-order approximation from the small-scale higher-order truncation error effectively. The intrinsic multiresolution analysis and time-frequency localization characteristics of wavelet theory, as well as the various selectivity of basis functions, align precisely with the demands of this mathematical feature. Therefore, they can provide fundamental theory and diverse approaches for developing efficient quantitative methods to address various complex mechanics problems. Based on this fact, this paper provides a comprehensive discussion of wavelet theory, focusing on the theoretical framework of biorthogonal multi-resolution analysis and the construction method of frequently used wavelet bases. Furthermore, wavelet approximation of the function defined on a finite domain is presented in detail. The fundamental principles, development, merits, and shortcomings of different wavelet-based numerical methods are systematically elucidated. Several novel wavelet-based methods with outstanding performance developed recently are elaborated especially, and their applications in solving typical mechanics problems are reviewed. Meanwhile, the present paper also points out challenges encountered by the existing wavelet-based numerical methods when addressing complex and strongly nonlinear mechanics problems. This may provide valuable references for the development of wavelet-based numerical methods and their applications in complex mechanics and engineering problems, and introduce new perspectives and methods for solving these problems efficiently, accurately, and universally.

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