Wave Deformation Research Articles

Ground deformation and blast wave propagation in dry sand subjected to buried explosion: A centrifuge modelling study

A series of centrifuge model tests of buried explosions in dry sand were designed and performed to investigate the blast effects in diverse underground explosion (UE) scenarios. The typical ground deformation pattern and blast wave propagation in different types of UE events were modelled. The excavated cratering was observed in shallow-buried excavation explosion tests. Surface collapse and subsidence craters were formed in the partially contained explosion tests, in which the initial ground motion direction turned from upward to downward with the increase of burial depth. The scaling law for centrifuge modelling of blast wave propagation was derived and examined. The critical burial depth for complete coupling of ground shock energy is within the range of 0.4 m/kg1/3 and 0.8 m/kg1/3, and the gravity effect on blast wave propagation can be disregarded under centrifugal accelerations of 62 g and 106 g (g is the Earth's gravity). The elastic blast wave velocity in dry sand was determined in the model test, and it increased with the burial depth. The attenuation laws for peak pressure and peak scaled acceleration in dry sand were calibrated, and the scaling coefficient for peak pressure estimation increased with the medium's acoustic impedance, while the attenuation coefficient showed a contrasting trend.

Nonlinear charge and energy transport in anharmonic quasi-two-dimensional systems.

We study the localized states of an extra electron in an anisotropic quasi-two-dimensional system in which the electron-lattice interaction and the anharmonicity of the lattice vibrations are dominant in one direction. This model describes layers of polydiacetylene or other polymer chains, beta sheets of polypeptides, multilevel microstructures of conjugated polymers, and other low-dimensional systems. It is shown that for appropriate parameter values of the system an extra electron can excite a soliton-like mobile wave of the lattice deformation, within which it can get self-trapped. Such a bound state of an electron and the lattice deformation form a nonlinear two-component polaron-like entity, which can propagate with minimum of the energy dissipation. Our findings are based on the variational approach and the full numerical solution of the coupled system of nonlinear equations. These results suggest that the experimentally measured charge and energy transport over macroscopic distances in the above-mentioned systems can be provided by the soliton mechanism and thus have a potential impact on the theoretical background of the numerous applications of low-dimensional materials in nanoelectronics.

Controllable transformed waves of a (3 + 1)-dimensional variable-coefficient Kadomtsev–Petviashvili equation in fluids or plasma

In this paper, we study the modulations of nonlinear transformed waves for a (3 + 1)-dimensional variable-coefficient Kadomtsev–Petviashvili equation in fluids or plasma. By virtue of the phase shift analysis, the shape-changed and unchanged transformed waves are investigated, which shows the inhomogeneity can restrain the time-varying property. The deformation of waves is determined by the phase difference between two wave components. In addition, the evolutions of parabolic transformed waves are illustrated via characteristic lines analysis. The interactions are further explored, which involve the long- and short-lived collisions. In particular, we discuss the dynamics of unidirectional and reciprocating molecular waves based on the velocity resonance condition, including the shape-changed and unchanged atoms. Different from previous results, certain new types of transformed molecular waves with shape-unchanged atoms are discovered. Our results indicate that the inhomogeneity can produce novel transformed waves and further facilitate the modulation of phase transition mechanism.

The experimental and numerical analysis of elastic rock mechanical properties in tight conglomerate rock samples: a case study in Junggar Basin

Tight conglomerate rocks consist of gravels and rock matrices. The existence of these stiff gravels leads to heterogeneity in conglomerates and makes it difficult to characterize rock mechanical properties, which then affects drilling and hydraulic fracturing operations in tight conglomerate hydrocarbon-bearing reservoirs. This case study introduces a series of experimental and numerical analyses for the better understanding of rock deformation and elastic wave propagation patterns in a tight conglomerate reservoir in Junggar Basin, China. Tri-axial compression tests, acoustic test, and finite element modeling of rock deformation and elastic wave propagation in conglomerate rocks are presented. Experimentally tested samples exhibit good brittleness and shearing failure patterns, while well correlated static-dynamic elastic moduli and P-S wave velocities are captured. Numerical results show that the existence of stiff gravels leads to strong direction-dependent stress and strain anisotropies. Stress concentrations are also induced by gravels radially and axially. In the elastic wave domain, stiff gravels facilitate the propagation of elastic waves. The gravel close to the wave source also induces stronger compressive/tensile states in the wave domain, indicating that the existence of gravels in conglomerates can alter waveforms. This integrated approach improves the quantitative understanding of stress, strain, and elastic wave responses in heterogeneous tight conglomerates. This case study also serves as a reference for the brittleness evaluation and geomechanical evaluation in the study area. The contribution of this work is primarily about the integrated experimental study, solid deformation modeling, and elastic wave modeling of tight conglomerate rocks.

Rectangular Plate Rebound Vibration Suppression using Double Collision Phenomena

The rectangular plate is a model of the internal mirror of an SLR camera. The internal mirror model is a rectangular metal plate that rotates on its own axis around one side of a rectangle. When the mirror hits to the stopper, a rebound vibration occurs. The double collision method is introduced to reduce the rebound vibration. The timing of the double collision varies the amount of rebound vibration. 3-D Particle Image Velocimetry (3-D PIV) and 3-D motion analysis are used to investigate the rebound phenomena. 3-D PIV measures the rebound vibration velocity of the mirror model surface at the moment of collision. 3-D motion analysis is used to measures the rebound vibration displacement at the moment of collision. When the rebound vibration is small, the low-velocity region on the surface of the mirror model moves in the longitudinal direction. This indicates that the mirror model is undergoing wave deformation after the moment of collision. When the timing of the second collision is optimized, the deformation of the mirror model at the moment of collision is increased and the rebound amount is suppressed.

Mathematical Methods of Observation of Wave Processes During Deformation of 3D Technology Products

The purpose of this work is to develop and apply mathematical methods (Fourier interpolation) to fix the presence and evaluation of the mechanisms of wave processes developing in products made of powder stainless and heat-resistant alloys of additive technologies (SLM) during their deformation.Methods. To fix the presence of wave processes of plastic deformation in loaded 3d technology products, samples of powder stainless steel 03X18H12M2 (analog AISI 316L) and powder heat-resistant alloy 08ХN53BMTU (analog Inconel 718), manufactured using SLM technology on a 3d printer SLM280 2.0HL, were used. The samples were subjected to uniaxial stretching (GOST 1497-84) with a constant rate of capture in air at room temperature. The lengths of the marked sections were measured using digital video recording of the loading process of the marked surface of the samples. Graphs of the dependences of local relative deformation along the length of the sample and at selected test moments were constructed. The mathematical substantiation of the existence of the wave character of the fixed functions as periodic was carried out by decomposing them into a Fourier series with subsequent interpolation.Results. It has been experimentally established that in the volume of the studied samples of powder stainless steel type 316L and heat-resistant alloy type Inconel 718, obtained by SLM technology, when they are stretched, there is a multistage character of wave deformation reflecting the development and movement of local micro-volumes of increased plasticity (foci of localized deformation). The Fourier interpolation procedure of a complex of experimentally obtained piecewise linear functions of the dimensions of the marking grid and their local deformations confirmed their apparent periodicity, i.e. the presence of a wave character.Conclusion. The developed technique of fixing and mathematical processing of wave deformation spectra can be used to analyze the changing parameters of the surface marking (rolling grid) of 3d products both along their length and at fixed loading times, as well as when constructing multidimensional dependencies of the marking parameters on the geometry of samples and test time.

Prediction of elastic deformation and elastic wave velocity of perovskite MgSiO3 with cubic structure at high pressure up to 140 GPa and high temperature up to 4000K from statistical moment method

Based on the structural and thermodynamic theory of cubic perovskite built on the SMM published in previous works, we construct the theory of elastic deformation and elastic wave velocity of cubic perovskite. We apply the obtained theory to numerical calculations for MgSiO3 at extreme conditions of temperature up to 4000K and pressure up to 140 GPa. The SMM calculation results for MgSiO3 are consistent with the current calculation and experimental results for CaSiO3. Our results are predictive of the thermodynamic properties of MgSiO3 in the context of scarce data on this material.

THE EXACT TRAVELING WAVE SOLUTIONS OF LOCAL FRACTIONAL GENERALIZED HIROTA–SATSUMA COUPLED KORTEWEG–DE VRIES EQUATIONS ARISING IN INTERACTION OF LONG WAVES

Wave–wave interaction occurs in the propagation deformation of nonlinear long waves in shallow-water. In order to further study the propagation mechanism of shallow-water long waves interaction, the exact traveling wave solutions of the local fractional generalized Hirota–Satsuma coupled Korteweg–de Vries (HS-KdV) equations defined by the Cantor sets are obtained. The non-differentiable solutions with fixed fractal dimension and different propagation velocity are discussed. The results indicate that the exact solutions of the local fractional generalized HS-KdV equations characterize the interaction of fractal long waves with different dispersion relations on shallow-water surfaces.

Solitary deformation waves in two coaxial shells made of material with combined nonlinearity and forming the walls of annular and circular cross-section channels filled with viscous fluid

The aim of the paper is to obtain a system of nonlinear evolution equations for two coaxial cylindrical shells containing viscous fluid between them and in the inner shell, as well as numerical modeling of the propagation processes for nonlinear solitary longitudinal strain waves in these shells. The case when the stress-strain coupling law for the shell material has a hardening combined nonlinearity in the form of a function with fractional exponent and a quadratic function is considered. Methods. To formulate the problem of shell hydroelasticity, the Lagrangian–Eulerian approach for recording the equations of dynamics and boundary conditions is used. The multiscale perturbation method is applied to analyze the formulated problem. As a result of asymptotic analysis, a system of two evolution equations, which are generalized Schamel– Korteweg– de Vries equations, is obtained, and it is shown that, in general, the system requires numerical investigation. The new difference scheme obtained using the Grobner basis technique is proposed to discretize the system of evolution equations. Results. The exact solution of the system of evolution equations for the special case of no fluid in the inner shell is found. Numerical modeling has shown that in the absence of fluid in the inner shell, the solitary deformation waves have supersonic velocity. In addition, for the above case, it was found that the strain waves in the shells retain their velocity and amplitude after interaction, i.e., they are solitons. On the other hand, calculations have shown that in the presence of a viscous fluid in the inner shell, attenuation of strain solitons is observed, and their propagation velocity becomes subsonic.

About one method for studying monitoring data for modeling potential seismic sources

Modeling a lumpy geological media using the theory of block structures and studying the conditions for the occurrence of resonance phenomena in the areas where blocks meet will make it possible to determine the locations of potential rearrangements associated with the development of natural disasters. In this paper we present a description of experimental data on the study of the Earth’s crust block structure used to construct a model for the propagation of slow deformation waves in the lithospheric structures of the region. Since the appearance of anomalies in the velocities of longitudinal waves indicates the emergence of geological rearrangements in the zone of a developing seismic event, a comprehensive method of active vibroseismic monitoring using a signal with linear frequency modulation and a harmonic signal is proposed to identify dilatant-type structures.

Physically Admissible and Inadmissible Exact Localized Solutions in Problems of Nonlinear Wave Dynamics of Cylindrical Shells

It is shown that, when studying nonlinear longitudinal deformation waves in cylindrical shells, it is possible to obtain physically admissible solitary wave solutions using refined shell models. In the article, a physically admissible exact localized solution based on the Flügge – Lurie – Byrne model is constructed. An analysis of the influence of the external nonlinear elastic medium on the exact solutions obtained is carried out. It is established that the use of quadratic and cubic nonlinear deformation laws leads to nonintegrable equations with exact soliton-like solutions. However, the amplitudes of the exact solutions exceed the values of permissible displacements corresponding to the maximum points on the curves of the deformation laws of the external medium, which leads to the physical inadmissibility of these solutions.

A noninvasive measurement technique for the initial bending stiffness of an arterial wall

Vascular disease poses a significant threat to human health. Effective detection methods for quantifying noninvasive arterial wall stiffness enable the early identification of populations exhibiting arteriosclerosis tendencies, providing substantial value for vascular disease prevention and treatment. However, current methods for evaluating arterial stiffness rely on simple tangent stiffness, which is affected by blood pressure fluctuations. This study utilizes a collapse model to investigate arterial deformation and pulse wave propagation under transmural pressure with different arterial wall thicknesses and material properties. Based on the pressure–area relationship of collapsed blood vessels, the relationship between pulse wave velocity and initial bending stiffness at the collapsed state is derived. A method is, then, proposed to evaluate the arterial wall bending stiffness incorporating cuff and photoplethysmography technology for assessing arteriosclerosis. This method is verified through a collapse experiment with a rubber tube and employed in measuring the initial bending stiffness of a human radial artery in vivo. The implementation of this measurement method facilitates vascular stiffness measurements beyond the restriction of tangent modulus and blood pressure changes, offering a quantitative evaluation of arterial wall stiffness. The technique can, therefore, amplify the precision and dependability of preliminary arteriosclerosis lesion diagnostic procedures.

Pulsating Active Matter.

We reveal that the mechanical pulsation of locally synchronized particles is a generic route to propagate deformation waves. We consider a model of dense repulsive particles whose activity drives periodic change in size of each individual. The dynamics is inspired by biological tissues where cells consume fuel to sustain active deformation. We show that the competition between repulsion and synchronization triggers an instability which promotes a wealth of dynamical patterns, ranging from spiral waves to defect turbulence. We identify the mechanisms underlying the emergence of patterns, and characterize the corresponding transitions. By coarse-graining the dynamics, we propose a hydrodynamic description of an assembly of pulsating particles, and discuss an analogy with reaction-diffusion systems.

Non-dimensional analysis on blast wave propagation in foam concrete: Minimum thickness to avoid stress enhancement

Foam concrete is a prospective material in defense engineering to protect structures due to its high energy absorption capability resulted from the long plateau stage. However, stress enhancement rather than stress mitigation may happen when foam concrete is used as sacrificial claddings placed in the path of an incoming blast load. To investigate this interesting phenomenon, a one-dimensional difference model for blast wave propagation in foam concrete is firstly proposed and numerically solved by improving the second-order Godunov method. The difference model and numerical algorithm are validated against experimental results including both the stress mitigation and the stress enhancement. The difference model is then used to numerically analyze the blast wave propagation and deformation of material in which the effects of blast loads, stress–strain relation and length of foam concrete are considered. In particular, the concept of minimum thickness of foam concrete to avoid stress enhancement is proposed. Finally, non-dimensional analysis on the minimum thickness is conducted and an empirical formula is proposed by curve-fitting the numerical data, which can provide a reference for the application of foam concrete in defense engineering.

Numerical Simulation and Measurement of Deformation Wave Parameters by Sensors of Various Types.

The results of applications of various methods for measuring the parameters of high-speed loading using a strain gauge, a fiber Bragg grating located on a metal measuring rod and an interferometer monitoring the movement of the free boundary of the end of the rod are presented. Numerical simulation confirmed the adequacy of the description of the shock-wave process according to experimental data and showed that, with the thickness of the adhesive layer fixing the fiber Bragg grating and the strain gauge on a dimensional rod up to 100 µm, the deformation parameters of the sensors correspond to the parameters of the stress-strain state of the rod. Experimentally, a good correspondence of the results of measuring the magnitude of the relative deformation at a pulse duration of 10-100 µs using sensors of various types is shown, and an estimate of the limit values of the measured values of the deformation wave parameters is given.

Multi-phase simulation for understanding morphodynamics of gravel beaches

This paper presents the use of an Eulerian–Eulerian multi-phase model to examine sediment transport over a gravel beach under regular waves. A previously published full-scale experiment is reproduced numerically; the simulated wave deformation, flow velocity, pore pressure, and morphological evolution are consistent with measurements. The multi-phase model can produce berm formation for smaller waves and beach erosion for larger waves as observation in previous field studies. The sensitivity analysis suggests that the nonlinear component of drag has significant effect on the berm formation through infiltration and exfiltration. The two simulated forces applied on the sediment (drag and buoyancy) are examined. The drag is the main force directly for sediment transport; therefore the sediment transport rate has high correlation with depth-averaged flow velocity. The buoyancy that is caused by plunging flow impacting beach face can push the sediment landward in the bore front, where the flow acceleration has its peak. The flow acceleration is considered in some previous sediment transport models empirically for simulating morphological evolution of gravel beach under waves. The buoyancy links the flow acceleration and sediment transport rate in the bore front.

Computer information technology-based green excavation of tunnels in complex strata and technical decision of deformation control

Abstract Currently, information processing of tunnel engineering has mainly adopted conventional mathematical statistics-based methods. Moreover, some nonlinear processing methods are implemented to derive more insights, even though the degree of research is not deep enough. In the research, the rock mechanics test is carried out by drilling a method and taking samples in situ according to the construction technology of tunnels in complex geological conditions and implementing computer information-based methods. Also, rock mechanics tests are carried out in the excavation test area of the flat tunnel. Based on the tests using physical properties, such as deformation, tensile, uniaxial compression, triaxial compression, and longitudinal wave velocity, the physical and mechanical characteristics of the surrounding rock in the tunnel area are comprehensively evaluated, and the stability of the tunnel rock mass is assessed to devise convenient conditions for the subsequent research of the complex geological tunnels based on green excavation. The particle density of sandy mudstone, the bulk density, the porosity, and the natural water content are represented by 2.67 ± 0.61 g/cm3, 2.56 ± 1.42 g/cm3, 7.45%, and 2.86%, respectively, in terms of physical characteristics. These indicate that the sandy mudstone structure is relatively loose, with relatively large pores, micro-fractures, and a high degree of natural water content. The representative deformation test curve of the rock block shows that the ratio of deformation modulus to the compressive strength of the rock block is 650 on average, and Poisson’s ratio ranges from 0.21 to 0.38. These show that sandy mudstone has deformation properties after compression. The tensile strength of sandy mudstone, the shear strength, and c are represented by 1.25 ± 0.23 MPa, f = 1.32, and = 2.35 MPa, respectively. The stated test results can provide a scientific basis for selecting engineering design and its construction parameters in similar areas. In addition, the measurement results show that the surrounding rock will gradually increase, and the tunnel space will gradually become shorter with the increase of buried depth when the gravity stress field occurs. The linear elastic displacement of soft rock is smaller than that of elastic–plastic analysis, and the deeper the tunnel is buried, the larger the displacement difference would be. Therefore, establishing a stable and orderly monitoring and detection system could fully understand the intrinsic law between surrounding rock stress release and surrounding rock pressure and obtain accurate monitoring and measured data to evaluate the grading management standard of a tunnel at the ultimate displacement. In a word, this research provides a feasible idea to study the decision process of green excavation and deformation control technology of tunnels in complex strata.

A mechanism-based theory of cellular and tissue plasticity.

Plastic deformation in cells and tissues has been found to play crucial roles in collective cell migration, cancer metastasis, and morphogenesis. However, the fundamental question of how plasticity is initiated in individual cells and then propagates within the tissue remains elusive. Here, we develop a mechanism-based theory of cellular and tissue plasticity that accounts for all key processes involved, including the activation and development of active contraction at different scales as well as the formation of endocytic vesicles on cell junctions and show that this theory achieves quantitative agreement with all existing experiments. Specifically, it reveals that, in response to optical or mechanical stimuli, the myosin contraction and thermal fluctuation-assisted formation and pinching of endocytic vesicles could lead to permanent shortening of cell junctions and that such plastic constriction can stretch neighboring cells and trigger their active contraction through mechanochemical feedbacks and eventually their plastic deformations as well. Our theory predicts that endocytic vesicles with a size around 1 to 2 µm will most likely be formed and a higher irreversible shortening of cell junctions could be achieved if a long stimulation is split into multiple short ones, all in quantitative agreement with experiments. Our analysis also shows that constriction of cells in tissue can undergo elastic/unratcheted to plastic/ratcheted transition as the magnitude and duration of active contraction increases, ultimately resulting in the propagation of plastic deformation waves within the monolayer with a constant speed which again is consistent with experimental observations.

Influence of low plasticity burnishing on the formation of strain induced martensite in the surface layer

In this research, AISI 304 austenitic stainless steel was used as work material and the influence of low plasticity burnishing (LPB) parameters (speed, number of passes and pressure) was investigated in terms of equivalent strain, LPB force, strain induced α′-martensite formation, deformation wave morphology and microhardness. Additionally, a correlation between the formation of α′-martensite and surface topography was investigated. The results showed that increasing the number of passes and pressure intensifies strain, while higher speed reduces friction and results in lower and more evenly distributed strain. The formation of LPB-induced α′-martensite was analyzed in a surface layer from 0.255 μm to a maximum depth of 2 μm. The highest content of α′-martensite was identified near the surface and decreased with depth. Mössbauer analysis (depth of ≈0.1 μm) supported this result. This behavior deviates from predictive models. Increasing the LPB speed reduces the α′-martensite content due to the generated adiabatic heat and, in some cases, its formation is nearly inhibited (< 5 %). The increase in the number of passes elevates the strain and, consequently, the α′-martensite content, with a maximum value approximately 90 %. Furthermore, the number of LPB passes was the only parameter to produces a refined grain layer. The increase in pressure elevates the strain, raising the content of α′-martensite. The trend of increasing α′-martensite content with higher numbers of passes and pressure was also observed in the context of waviness, i.e., the increase in deformation that is responsible for the higher α′-martensite content also increases the surface waviness.

MODELING OF WIND-WAVE GROWTH IN STRONG WIND CONDITIONS BASED ON PHASE-RESOLVING WAVE MODEL

Recently, coastal disaste have occurred by typhoons passing through bays, such as Typhoon Jebi in 2018 and Typhoon Hagibis in 2019 (Mori et al.(2019), Shimozono et al.(2020)). The current wave model cannot simultaneously account for the development of wind waves due to strong winds and wave deformation due to topography. This study aims to develop a phase-resolving wave model that considers the development of wind waves in shallow water under strong wind conditions. A wave development term that considers the local wave deformation is introduced into the phase-resolving wave model. XBeach (Roelvink et al., 2009) a numerical model based on the nonlinear long wave equation with nonhydrostatic pressure term, is used to calculate the waves in coastal areas. The wave development term is introduced, and the wave development process is optimized based on sensitivity experiments.