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Development and application of electromagnetic loading expansion ring test technology
LIU Zongxing, ZHANG Chunyang, CAO Miao, CHEN Feiying, LIU Jun, LI Yulong
 doi: 10.6052/1000-0992-24-010
Abstract(257) HTML(122) PDF(57)
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 104 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 expansion ring test technology.
Digintel mechanics—Governing the digintel era
YANG Wei
 doi: 10.6052/1000-0992-24-042
Abstract(2386) HTML(59) PDF(759)
Abstract:
Digintel mechanics refers to the mechanics studies that would govern the scientific rules for the digintel era, with digintel abbreviates the combination of digital and intelligence. Digintel mechanics is defined herein as the exploration for the mechanisms concerning the interactions, both within and between, physical space, cyber space and cognition space, and as the revelation of causation or/and correlation laws. Eight basic scientific issues concerning digintel mechanics are listed. Attention is then focused on 7 routes of methodologies confined in the X-4 tetrahedron. Five research thrusts suitable for the preliminary development of digintel mechanics are enumerated, they are digintel mechanics formalism, mechanics of intelligent flexors, convergent digintel computation, cross-scale mechanics, and mechanics for embodied intelligence.
Progress, applications, and challenges of interface instability in solids
CHEN Han, GAN Yuanchao, PENG Jianxiang, YU Yuying, HU Jianbo
 doi: 10.6052/1000-0992-24-014
Abstract(131) HTML(32) PDF(64)
Abstract:
The growth of interface instability in solids is a critical phenomenon affecting various fields of engineering and science, including implosion physics, inertial confinement fusion ignition, and the dynamic behavior of materials. This instability can lead to complex phenomena such as the interpenetration of light and heavy media at solid surfaces, material micro-jetting, and turbulent mixing, highlighting the significance of understanding its underlying mechanisms. This paper reviews the current research status of Richtmyer−Meshkov (RM) and Rayleigh−Taylor (RT) instabilities at solid interfaces in Chapters 2 and 3. We summarize existing theoretical models of instability growth and discuss their limitations. Unlike the instability growth observed in pure fluid interfaces, solid materials possess inherent strength, which enables some of the energy from perturbation growth to be transformed into lattice thermal energy through dissipative mechanisms. This energy conversion reduces the rate of perturbation growth and may even suppress the development of instabilities. Consequently, understanding the effects of material strength under dynamic loading conditions is crucial for comprehending instability growth behavior. Moreover, the outcomes of solid interface instability are indicative of various material properties, including constitutive relationships and equations of state. Researchers have proposed that instability growth can be leveraged to determine the dynamic yield strength of materials, validate high-pressure constitutive models, and mitigate instability growth. Chapter 4 focuses on this aspect, emphasizing the need to establish a theoretical model that accurately describes the “correlation mechanism” between instability phenomena and material properties for effective applications. Building on these foundations, Chapter 5 explores future opportunities and challenges in this field.
Research progress on the stability mechanism and control of ventilated supercavitation
WANG Zhiying, WANG Jingzhu, HUANG Jian, WANG Zhan, WANG Yiwei
 doi: 10.6052/1000-0992-24-024
Abstract(129) HTML(22) PDF(40)
Abstract:
Ventilated supercavity drag reduction is a key technology to break through the traditional underwater speed limit and achieve high-speed operation of underwater vehicles, which has important engineering application value. The navigation stability of underwater vehicles is a bottleneck problem that restricts the development of supercavitating vehicles, which is closely related to the stability of ventilated supercavity. Therefore, accurate prediction and control of supercavity shape are one of the key factors in the overall design of supercavitating vehicles. This paper first introduces the research progress on the flow morphology characteristics of ventilated supercavities under different flow conditions, and further sorts out the key scientific issues that affect the flow morphology, including the characteristics and stability mechanism of the cavity interface, the closure mechanism of the supercavity, and the interaction between the jet and the supercavity. Finally, based on the understanding and recognition of the morphology of ventilated supercavities, a method for achieving flow control of ventilated supercavities is introduced.
Recent advances in research on large-deformation dynamics of slender pipes conveying fluid
CHEN Wei, CAO Runqing, HU Jiachun, DAI Huliang, WANG Lin
 doi: 10.6052/1000-0992-24-027
Abstract(535) HTML(76) PDF(133)
Abstract:
Slender pipes conveying fluid are an important structure in various engineering equipment systems such as engine hydraulic device, aviation tanker, nuclear heat exchanger and offshore drilling platform. When the flow velocity is sufficiently high, the slender pipe may be subjected to flow-induced instability including buckling and flutter, which may lead to safety accidents in serious cases. Flow-induced instability and nonlinear vibration of pipes conveying fluid are typical fluid-structure interaction behaviors, and have become a generic paradigm and fertile dynamics problem in nonlinear dynamics and fluid-structure interaction mechanics. After establishing governing equation, clarifying the stability mechanism and analyzing the nonlinear vibration mechanism of pipes conveying fluid, much attention has been payed to the large-deformation dynamics of this dynamical system in recent years. In this review, the research progress of nonlinear vibrations, especially the large-deformation bending dynamics of slender pipes are systematically introduced. Firstly, the nonlinear characteristics and classification of the fluid-conveying pipe system are summarized, and the applicability of some common assumptions is briefly analyzed. Secondly, the Taylor expansion approximation model, geometrically exact model, absolute node coordinate formulation model, data-driven model and other related modeling and solving methods are reviewed. Then, the nonlinear dynamics mechanism and evolution law of cantilevered and supported pipes are reviewed, and some recent research progress of cantilevered pipes from small-deformation hypothesis to large-deformation response is emphasized. On this basis, several typical methods of improving the stability of the pipe, suppressing the nonlinear vibrations of the pipe and utilizing the large-deformation response of the pipe are also introduced. Finally, the research status of large-deformation dynamics of slender pipe conveying fluid is summarized, and several basic scientific problems worthy of attention are pointed out.
Helicity: A key role in turbulence
YU Changping, HU Running, GAN Runyuan
 doi: 10.6052/1000-0992-24-018
Abstract(427) HTML(110) PDF(124)
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Helicity is closely related to the topology of flow. This paper first explains the specific connection between helicity and flow structures. Subsequently, this paper focuses on elaborating the role of helicity in turbulence, as well as its coupling with other physical effects. Based on the crucial influence of helicity on flow structures and turbulent dynamics, this paper then briefly introduces the current applications of helicity in turbulence theory and simulation modeling. Finally, this paper summarizes the current research progress, outlining the overall advancement of helicity and the main directions for future studies.
Mechanical behaviors of micro-nano systems associated with van der Waals interaction
QIN Wen, KOU Zepu, LIU Xiaofei, ZHANG Zhuhua
 doi: 10.6052/1000-0992-24-019
Abstract(240) HTML(68) PDF(52)
Abstract:
van der Waals (vdW) interactions originating from quantum and thermal fluctuations are ubiquitous in natural and artificial systems. Accurate descriptions and characterizations of vdW interactions are crucial to understanding the mechanical behavior and realizing the mechanical design of micro-/nano-systems. This review summarized recent research progresses on vdW-dependent mechanical behaviors of micro-/nano-systems. First, we introduced vdW theories for atomic and molecular systems, including pairwise approximation, nonlocal density functional theory, adiabatic-connection fluctuating-dissipation theorem and many-body dispersion theory, as well as theories for continuum systems, including analytic, semi-analytic and numerical Lifshitz theory. Then, we reviewed the effects of vdW interactions on typical mechanical behaviors of two-dimensional materials and nano- and micro-electromechanical systems. We also discussed fascinating effects emerged from vdW interaction, including repulsive vdW force, non-monotonic vdW trap, Casimir rotational torque, Casimir flipping torque and vdW screening. Finally, we analyzed limitations of current vdW theories and presented the outlook for future development.
AI for PDEs in solid mechanics: A review
WANG Yizheng, ZHUANG Xiaoying, TIMON Rabczuk, LIU Yinghua
 doi: 10.6052/1000-0992-24-016
Abstract(2852) HTML(475) PDF(1369)
Abstract:
In recent years, deep learning has become ubiquitous and is empowering various fields. In particular, the combination of artificial intelligence and traditional science (AI for science, AI4Science) 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 (physics-informed neural operator, PINO). 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.
Review
Wavelet-based numerical methods and their applications in computational mechanics
YANG Bing, WANG Jizeng, LIU Xiaojing, ZHOU Youhe, FENG Yonggu
2024, 54(3): 427-476.   doi: 10.6052/1000-0992-24-009
Abstract(730) HTML(156) PDF(289)
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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.
Modeling of joint structure interface friction mechanics: A review
SHEN Minmin, YANG Xiaodong
2024, 54(3): 477-521.   doi: 10.6052/1000-0992-24-008
Abstract(829) HTML(263) PDF(306)
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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 bottleneck that restricts the breakthrough in 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.
Research progress of biomimetic design and preparation of functional surfaces for droplet transport
LIU Ming, CHEN Shaohua
2024, 54(3): 522-562.   doi: 10.6052/1000-0992-24-015
Abstract(794) HTML(145) PDF(171)
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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.
Progress in assessing hazards of asteroid impact on earth
DANG Leining, BAI Zhiyong, SHI Yilei, HUANG Jie
2024, 54(3): 563-605.   doi: 10.6052/1000-0992-23-047
Abstract(712) HTML(300) PDF(139)
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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.
The multiscale digital core of shale and its application
JI Lili, LIN Mian, JIANG Wenbin, CAO Gaohui
2024, 54(3): 606-628.   doi: 10.6052/1000-0992-24-006
Abstract(345) HTML(57) PDF(76)
Abstract:
Reconstructing digital core that can fully characterize the multiscale pore (fracture) and matrix structure of the rock is one of the most advancing front issue in the field of unconventional oil and gas research, and is also an important foundation for shale oil and gas exploration and development. This article comprehensively analyzes the research progress in characterizing organic pore clusters, multiscale pore (fracture) structures, and representative element volumes (REV) of shale. Based on the analysis of the structural characteristics of marine shale in the Sichuan Basin, a new method for fully characterizing its multiscsal pore (fracture) structure has been proposed. On this basis, the digital cores are applied to the impact of multiscale pore (fracture) structures on acoustic properties and the gas content evaluation, and provides new technical methods for shale reservoir evaluation and sweet spots prediction.
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