力学进展

Digintel mechanics—Governing the digintel era

YANG Wei

2024, 54(4): 629-638. doi: 10.6052/1000-0992-24-042

Abstract(4181)

HTML (280)

PDF(1362)

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.

Development and application of electromagnetic loading expansion ring test technology

LIU Zongxing, ZHANG Chunyang, CAO Miao, CHEN Feiying, LIU Jun, LI Yulong

2024, 54(4): 639-668. doi: 10.6052/1000-0992-24-010

Abstract(899)

HTML (338)

PDF(140)

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.

Advances in vibration testing and model updating for nonlinear aerospace structures

WANG Xing

2024, 54(4): 669-699. doi: 10.6052/1000-0992-24-011

Abstract(1197)

HTML (262)

PDF(314)

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.

Helicity: A key role in turbulence

YU Changping, HU Running, GAN Runyuan

2024, 54(4): 700-738. doi: 10.6052/1000-0992-24-018

Abstract(1684)

HTML (461)

PDF(351)

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.

Mechanical behaviors of micro-nano systems associated with van der Waals interaction

QIN Wen, KOU Zepu, LIU Xiaofei, ZHANG Zhuhua

2024, 54(4): 739-770. doi: 10.6052/1000-0992-24-019

Abstract(1313)

HTML (440)

PDF(160)

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.

Progresses, applications, and challenges of interface instability in solids

CHEN Han, GAN Yuanchao, PENG Jianxiang, YU Yuying, HU Jianbo

2024, 54(4): 771-822. doi: 10.6052/1000-0992-24-014

Abstract(1006)

HTML (294)

PDF(200)

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.

Programmable multi-physical mechanics of mechanical metamaterials

Sinha P, Mukhopadhyay T

2024, 54(4): 823-871. doi: 10.6052/1000-0992-24-012

Abstract(2424)

HTML (518)

PDF(481)

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.

2024 Vol. 54, No. 4

NoticeMore >

Author CenterMore >

Related linksMore >