Mechanics of Solids最新文献

The current theories on pile driving vibration are based on localized theories. Therefore, the objective of this paper is to consider the gradient variation of porosity along the depth in relation to the depth of pile driven into the soil layer in the framework of non-local theory. The ramming energy parameter is introduced to improve the model of gradient variation of porosity along depth. The coupled analytical solution is proposed of surface vibration induced by steel pipe pile driven into nonuniform saturated soil layer by the porosity is coupled with density, shear modulus, Lamé constant and permeability coefficient, and coupling the tamping energy parameter into Eringen’s nonlocal theory and Biot’s theory of saturated porous elastic medium, and combining the mass conservation equation, momentum balance equation, and effective stress principle. Analysis the change rule of impact energy attenuation degradation and the influence of surface vibration deformation during the process of PHC pile driving into non-uniform saturated soil layer. The results of the study show that the influence of soil uneven gradient parameter on soil parameters is greater than that of energy parameter. Pile driven into the non-uniform soil layer at any depth location, uneven gradient parameters and energy parameters under the increase, the horizontal amplitude of surface vibration, vertical amplitude decreases. However, the horizontal amplitude and vertical amplitude of surface vibration increased with the increase of soil skeleton geometry parameter. The analysis shows that the energy parameter has the greatest influence on the horizontal and vertical amplitudes, the soil skeleton geometry parameter has the second greatest influence on the horizontal and vertical amplitudes, and the non-uniform gradient parameter has the least influence on the horizontal and vertical amplitudes. The results of the study can assess the problem of surface vibration response induced by pile driving construction, but the theory is a result of the study carried out in the framework of nonlocal elasticity theory, which still needs further improvement.

The influence of cohesive films toughened with modified nano-ZnO particles on the mechanical properties of thermoset-epoxy-based composite was investigated. Nano-ZnO is first modified by coupling agent to obtain modified nano-ZnO, which was added into epoxy resin as nanofiller. By blending modified nano-ZnO particles at different mass ratios from 0 to 4% in the presence of a curing agent, some cohesive films with different interlaminar properties were formed between the two interfacial surfaces in a composite specimen, which have been applied in end-notched flexure (ENF) tests and double cantilever beam (DCB) tests. A series of finite element (FE) models, together with the predetermined model parameters, were built to assess the influence of modified nano-ZnO and curing agent. The results show that, for the toughened beam (with 4 wt % modified nano-ZnO and 2 wt % GEL2-B2), the critical loads of ENF tests and DCB tests increases by 30.25 and 68.40%, respectively.

In order to investigate the differences between the dynamic response problems of quasi-saturated and saturated foundations. Based on the theory of quasi-saturated porous media, the dynamic response problem of a semi-infinite quasi-saturated soil foundation is investigated. Using the Fourier integral transform, the computational lexicon of the dynamic response of a quasi-saturated soil foundation under bar simple harmonic loading on the ground surface is established according to the Helmholtz vector decomposition principle. The effects of saturation degree and loading frequency on soil displacement, stress, and pore water pressure in the quasi-saturated foundation were analyzed. The results show that the loading frequency and the degree of saturation greatly influence the dynamic response of the quasi-saturated soil. With the increase of saturation, the surface displacement magnitude and positive stress magnitude increase, especially when S_r = 1, the surface displacement magnitude and positive stress magnitude change significantly, but the value of shear stress is not sensitive to the change of saturation. Pore water pressure increases with saturation and is most significantly affected by saturation relative to stress and displacement.

This paper examines the effects of several parameters such as phase velocity, wavenumber, heterogeneity, and triangular irregularity on the propagation of shear waves in a transversely anisotropic fluid-saturated porous layer situated over a heterogeneous elastic half-space. The triangular irregularity has been taken at the interface of half space and the layer. The dispersion equation for the considered model has been derived by applying Biot’s theory of elasticity, perturbation method and Fourier transformation techniques. The obtained dispersion equation for shear waves has been plotted graphically with the help of MATLAB software for various parameters. The dimensionless phase velocity has been plotted against the dimensionless wave number for different parameters such as anisotropic factor, ratio of the irregularity’s depth with the layer’s height, and inhomogeneity parameter. It has been concluded that the phase velocity of shear waves is strongly influenced by different value of inhomogeneity parameter, anisotropy factor and the ratio of the depth of the irregularity with the height of the layer. From numerical calculations, it is observed that when the wavenumber increases, the phase velocity decreases for some instant, then increases sharply and after that it decreases constantly. The findings of this study are valuable for the researchers who are working in the field of seismology, solid mechanics, geophysics and special in context of propagation of waves.

This paper conducts a study on the blunt force effect of 7.62 mm sniper bullet on protected targets. The experimental setup involved testing 7.62 mm sniper bullet infiltrating gelatin targets protected by body armor plate at varying distances. The study obtained the dimensions of the blunt force indentation caused by the bullet on ballistic gelatin at distances of 400 m and 800 m, and subsequently developed a numerical model for simulation. This numerical model was employed, in conjunction with a self-developed human body susceptibility assessment software, to determine the severity of damage that may be caused by the sniper bullet hitting the chest of a protected human body at 400 m and 800 m. The study’s findings revealed that the sniper bullet at 400 m produced a depression diameter of about 123.9 mm and a depth of around 60.8 mm on the gelatin target, while the bullet at 800 m resulted in a depression diameter of about 80.7 mm and a depth of about 32.6 mm. Additionally, it was observed that after the bullet penetrated the body armor, the gelatin absorbed significantly less energy than the body armor due to the absorption of a large amount of kinetic energy by the body armor. Moreover, when the projectile failed to penetrate the body armor, the peak stress in the gelatine was approximately several megapascals under the blunt impact of the body armor. Utilizing the Human vulnerability assessment software (HVAS), the study determined the maximum abbreviated injury scale (MAIS) damage scores for hits to the upper right of the human chest at 400 and 800 m as 5 (critical) and 4 (severe), respectively. The corresponding new injury severity score (NISS) were 75 and 41, indicating a gradual decline in the probability of fatality from 96.8 to 41.1% with the increase in hit distance.

Available experimental data on the additional external factors that influence the sandstone dynamic fracture are analyzed using the incubation time approach. Compressive strength dependences on loading rate are obtained for hydrostatically compressed and preheated sandstone samples. It is shown that with increasing loading rate, the strength characteristics of sandstone increase for all treatment temperature and hydrostatic pressure values. With increasing hydrostatic pressure, an increase in dynamic compressive strength is observed. A linear increasing relationship is established between the incubation time and the external hydrostatic pressure. The effect of pre-heat treatment on the sandstone dynamic compressive strength is assessed. It was found that heat-pretreated samples have lower compressive strength than samples not exposed to heat for all loading rates. The incubation time values are calculated for each pre-treatment temperature. The compressive strength inversion effect is discussed demonstrating that when comparing two sandstone samples treated at different temperatures one sandstone sample has higher compressive strength under quasi-static loads but is more easily damaged under high-velocity loads compared to the second sample. It is shown that to describe the dynamic fracture considering the influence of additional external factors, such as hydrostatic pressure and heat-treatment, two material constants (incubation time and static compressive strength) are sufficient.

Polydimethylsiloxane (PDMS) has attracted more attention due to its excellent elasticity and biomedical compatibility, can be applied in the design and manufacture of actuators, sensors and medical devices. In order to better simulate the tensile and compressive process of PDMS and obtain more accurate simulation results, multiple hyperelastic constitutive models based on PDMS materials were investigated. Firstly, according to the strain energy density function in the hyperelastic theory, engineering stress expressions for uniaxial deformation were derived in terms of Mooney–Rivlin with five parameters model and Yeoh model, as well as Mooney–Rivlin with two parameters model, Neo-Hookean model and Ogden model were all organized. PDMS samples were prepared with mixing ratio of 10:1 of base polymer and curing agent, dried at 60°C, and then we acquired the deformation values varying with tensile force and pressure. Afterwards, various material models were modelled with COMSOL Multiphysics, and the optimal material parameters of hyperelastic models for tensile, compressive, both tensile and compressive experimental data were analyzed, respectively. The results reveal that Mooney–Rivlin with five parameters models exhibit excellent fitting effect, with different material parameters for these three cases, as well as the determination coefficients of goodness of fit all greater than 0.99. Certainly, other hyperelastic models also have their own characteristics, Mooney–Rivlin with five parameters model especially has prominent advantage in simulating the stress-strain process of PDMS. In summary, the developed research findings provide valuable references into the accurate modeling of PDMS behavior, with practical significance for engineering application.

A unique three-dimensional model of generalized thermoelasticity, incorporating a single relaxation time and relying on stress gradient nonlocal elasticity, is presented in this study. The fundamental coupled equations governing the model are applied to a semi-infinite spatial medium with a rigidly fixed bounding surface, which is exposed to a time-dependent thermal shock. The general solution for the field variables is obtained in a closed form through the utilization of normal mode analysis and the eigenvalue approach technique. Numerical results, specific to a substance resembling copper, are provided for the field variables. Parametric studies are conducted to assess the impact of elastic nonlocality on various physical quantities. The graphical representation reveals a noteworthy influence of the nonlocal parameter on the field variables. The study further discusses and compares predictions from the new model with the Lord and Shulman theory of generalized thermoelasticity. Ultimately, the article concludes with a summary of key remarks.

Current study provides comprehensive insights into the estimation of blast wave parameters within three distinct anisotropic media, namely transversely isotropic (Cadmium Sulphide CdS), monoclinic (Lithium Tantalate LiTaO₃), and orthotropic (Ammonium Dihydrogen Phosphate ADP). Within the domain of blast modeling, there remains a significant gap in understanding the impact of surrounding media anisotropy—a crucial aspect often disregarded by numerous researchers. Acknowledging anisotropy holds paramount importance in studying the blast characteristics, the present work explores the velocity profiles of seismic quasi waves within the aforementioned anisotropic media, laying the groundwork for subsequent analyses estimating Scaled Peak Particle Displacement (SPPD) and Peak Pressure (PP). These parameters are evaluated using the Smith and Hetherington’s model, and relying on experimental Peak Particle Velocity (PPV). Furthermore, the study investigates the influence of various sand types, ranging from very dense to loosen, on PP and SPPD within the context of the aforementioned anisotropic media. Additionally, the research entails the estimation and numerical simulation of underground blast parameters, along with the Reflection and Transmission (RT) coefficients relevant to scattering at the interface between two dissimilar media. The findings bear significant relevance in the field of geotechnical engineering, ground shock estimation, mining, particularly in predicting how various sand types respond under diverse loading conditions and external stresses.

The present work investigates SH-wave regulation phenomena into a magneto-elastic transversely isotropic (MTI) strip clamped between a coated Newtonian viscous liquid layer and a heterogeneous elastic half-space. The classical dynamical coupled theory has been employed to examine the problem. Whittaker special function and variable separable technique have been employed to determine the exact solution of the governing equations. A closed-form dispersion equation for the SH-wave has been developed for this boundary conditions-based problem. The validity of our model has been examined in terms of special cases and compared with the classical Love wave equation. Numerical and graphical analyses have been executed for six numerical examples of the MTI layer namely; beryl, magnesium, cadmium, zinc, cobalt and isotropic. Therefore, a comparative study has been developed to examine the velocity profile of the wave for these different MTI examples through several graphs. The results show that the presence of magnetic field, viscosity, initial stress and gravitational field in the structure have major effects on the wave velocity. This model has huge potential to deal with many commercial and industrial applications in acoustic engineering, geotechnical engineering, ultrasonic, earthquake engineering, geophysics, etc.