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.
Chen H, Gan Y C, Peng J X, Yu Y Y, Hu J B. Progress, Applications, and Challenges of Interface Instability in Solids. AdvancesinMechanics, in press. doi: 10.6052/1000-0992-24-014.
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.
Wang Z Y, Wang J Z, Huang J, Wang Z, Wang Y W. Research progress on the stability mechanism and control of ventilated supercavitation. AdvancesinMechanics, in press. doi: 10.6052/1000-0992-24-024.
Abstract: Mechanical metamaterials are engineered materials with unconventional mechanical behavior that originates from artificially programmed microstructures along with intrinsic material properties. With tremendous advancement in computational and manufacturing capabilities to realize complex microstructures over the last decade, the field of mechanical metamaterials has been attracting wide attention due to immense possibilities of achieving unprecedented multi-physical properties which are not attainable in naturally-occurring materials. One of the rapidly emerging trends in this field is to couple the mechanics of material behavior and the unit cell architecture with different other multi-physical aspects such as electrical or magnetic fields, and stimuli like temperature, light or chemical reactions to expand the scope of actively programming on-demand mechanical responses. In this article, we aim to abridge outcomes of the relevant literature concerning mechanical and multi-physical property modulation of metamaterials focusing on the emerging trend of bi-level design, and subsequently highlight the broad-spectrum potential of mechanical metamaterials in their critical engineering applications. The evolving trends, challenges and future roadmaps have been critically analyzed here involving the notions of real-time reconfigurability and functionality programming, 4D printing, nano-scale metamaterials, artificial intelligence and machine learning, multi-physical origami/kirigami, living matter, soft and conformal metamaterials, manufacturing complex microstructures, service-life effects and scalability.
Sinha P, Mukhopadhyay T. Programmable multi-physical mechanics of mechanical metamaterials. AdvancesinMechanics, in press. doi: 10.6052/1000-0992-24-012.
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.
Qin W, Kou Z P, Liu X F, Zhang Z H. Mechanical behaviors of micro-nano systems associated with van der Waals interaction. AdvancesinMechanics, in press. doi: 10.6052/1000-0992-24-019.
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.
Liu Z X, Zhang C Y, Cao M, Chen F Y, Liu J, Li Y L. Development and application of electromagnetic loading expansion ring test technology. AdvancesinMechanics, 2024, 54(4): 1-30. doi: 10.6052/1000-0992-24-010.
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.
Wang Y Z, Zhuang X Y, Timon R, Liu Y H. AI for PDEs in solid mechanics: A review. AdvancesinMechanics, 2024, 54(4): 1-57. doi: 10.6052/1000-0992-24-016.
Abstract: For lighter, stronger and more flexible aerospace structures, the nonlinear phenomena observed during ground vibration tests and in-service operations are first sorted out. Two types of typical nonlinear structures-localised and distributed nonlinear structures—are then highlighted, the basic concepts of which are explained. Secondly, the vibration testing techniques developed for these nonlinear structures are compared, and the research progress is summarised from the perspective of frequency response test, pure modal test, free decay test and others. Finally, model updating procedures of the two types of nonlinear structures are analysed, with identification methods discussed. Future perspectives are pointed out and research suggestions are also highlighted. It is expected to provide a useful reference for the future development of vibration testing techniques and accurate modelling methods of nonlinear aerospace structures.
Wang X. Advances in vibration testing and model updating for nonlinear aerospace structures. AdvancesinMechanics, in press. doi: 10.6052/1000-0992-24-011.
Abstract: 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.
Yu C P, Hu R N, Gan R Y. Helicity: A key role in turbulence. AdvancesinMechanics, in press. doi: 10.6052/1000-0992-24-018.
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 were 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.
Chen W, Cao R Q, Hu J C, Dai H L, Wang L. Recent advances in research on large-defomation dynamics of slender pipes conveying fluid. AdvancesinMechanics, in press. doi: 10.6052/1000-0992-24-027.
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