Forces in mechanics最新文献

This research paper presents a comprehensive investigation into the response of a 3D finite element model when subjected to 7.62 AP projectiles. The study utilises Hetherington's armour composite equation and incorporates the Johnson-Holmquist material model to analyse the strength and failure criteria of the ceramic and Kevlar/epoxy components, respectively. The results highlight the remarkable resilience of the composite armour, demonstrating its ability to withstand projectile velocities up to 1500 m/s. However, as the ballistic velocity limit increases, the armour experiences significant damage, including projectile erosion and panel delamination. Through numerical simulations and advanced modelling techniques, the paper thoroughly explores the failure modes and energy absorption characteristics of composite armour systems under projectile impact. It investigates key parameters such as velocity, acceleration, kinetic energy, internal energy, pressure distribution, displacement, and damage progression. The analysis reveals a progressive decrease in kinetic energy as the projectile interacts with the armour, underscoring the crucial role of energy absorption in preventing projectile penetration. Moreover, the impact velocity influences the distribution of internal energy within the composite armour, with higher velocities leading to greater energy absorption up to a threshold limit. The study also determines the ballistic limit velocity (V50) using the velocity history approach and validates the findings with existing literature. Overall, the research provides valuable insights into the limitations of composite armour and offers important recommendations for designing and improving materials to achieve superior ballistic protection. It emphasises the significance of reaching the maximum ballistic limit while maintaining a lightweight armour structure by optimising the total armour thickness. This study contributes to the advancement of armour technology and enhances our understanding of the behaviour of composite materials under high-velocity impacts. It offers valuable guidance for the development of more robust armour systems suitable for various defence and protection applications.

The aim of this work is to derive exact partial-wave series expressions for the radiation force of plane compressional progressive waves propagating inside an elastic medium and incident upon an embedded elastic sphere. The analytical modeling is needed to provide fundamental physical understanding of the underlying phenomenon of mode conversion and its contribution to the acousto-elastic radiation force, and in experimental design. In the context of linear elasticity theory, a rigorous derivation for the acousto-elastic radiation force, based on the integration of the time-averaged radial component of the elastodynamic Poynting vector (or power flow density), is presented and discussed. Initially, the elastic scattering problem is determined and subsequently used to derive the mathematical expression for the acousto-elastic radiation force of progressive compressional waves. The method is also verified using the extended optical theorem for elastic compressional plane waves. Extension to the case of elastic plane standing wave is also provided. Particular importance is made on the contributions of elastic mode preservation (P → P) and mode conversion (P → S) to the acousto-elastic radiation force. Numerical computations for the dimensionless radiation force efficiency and its components demonstrate the importance of compressional-to-shear mode conversion in the scattering by the sphere encased in a linearly-elastic medium. The analytical formalism presented here can be used to validate numerical methods, and the results of the simulations can be utilized as a priori knowledge in optimizing and designing acousto-elastic radiation force experiments involving elastic compressional progressive waves on a sphere in acoustically-engineered materials applications, elasticity imaging methods, activation of implantable devices, characterization of biological tissue, and non-destructive evaluation to name some examples.

In this article, to study the fluid behavior on various specific conditions to improve the heat transfer system and here, analysis on mathematical model of dynamic fluid consist of micropolar fluid has allowed micro rotational effect with laminar flow of Darcy forchheimer model which allow inertia effect has incorporated with heterogeneous and homogenous chemical reaction undergoes heat exchanger system with boundary layer problem has modeled. The mathematical model of fluid mechanic governing equations are in the form of partial differential equation (PDE) and similarity transformation into numerical methods (PC4-FDM) of predictor and corrector technique undergoes discretized mesh point and convergence with fourth order finite difference method and shooting method is also equipped to get better solution. The additions of significant heterogeneous parameter depicts that increasing behavior in fluid concentration and homogeneous parameter depicts that decreasing in fluid concentration by allowed micro rotations leads to collision and on increasing the Eckert number related to viscous dissipation has exhibited that increased fluid velocity and decreased fluid temperature. Micro rotation parameter exhibits that similar increased fluid velocity and slight decreased in temperature of the fluid. Darcy forchheimer parameter which related to inertial effect has depicts that decreased in velocity with increased temperature of the fluid in convection system. Due to Industrialization, the study of convection heat transfer system has enormous scope which has necessity to improving the heating and cooling system of industrial mass machineries like powerplant, waste heat recovery unit, pharmaceutical industries etc.

In view of the recent interest in modifying the surface functionality and esthetics of polymeric materials by sand blasting treatment, a numerical model was developed as a tool to predict the evolution of surface morphology as a function of blasting parameters. The wide range of shot size and shape variations, typical of blasting media, were parametrized based on microscopical observations. Thus, the developed numerical model accounts for the media inhomogeneity and also implements randomness in both the sequence and position of the multiple impacts. To make the model as realistic as possible, the velocity of individual shots was calculated based on their interaction with the airflow. Systematic experiments were performed using Polycarbonate (PC) as the substrate material and Alumina as the blasting media. A comparison of the experimental and numerical results demonstrated the ability of the developed model to successfully predict the surface roughness generated by sand blasting, as the shot arrangement and distribution were varied. This model establishes a potential basis for future studies regarding the performance of the sand blasted surfaces such as wettability using numerical approaches.

Recently, high aspect ratio materials like nanofibers with outstanding mechanical properties have been developed and used to improve the mechanical characteristics of construction materials. However, despite the excellent results obtained in asphalt binder modification, only a few types of polymeric nanofibers have been used for this purpose. In this sense, polyacrylonitrile has good thermal and mechanical characteristics to maintain the shape at the typical temperatures the asphalt is heated.

This study evaluates the effect of electrospun polyacrylonitrile (PAN) nanofibers on the rutting resistance and fatigue parameters of asphalt binders. For this, fibers with an average diameter of 1.3 µm were prepared and randomly dispersed into neat PG 64–22 asphalt binder. Subsequently, a dynamic shear rheometer (DSR) was used to determine G*/sin δ, J_nr, R_3.2, and N_f.

In the range studied, Jnr_3.2 showed a reduction of up to 35%, and the elastic recovery increased up to 4.5 times compared to the reference material. It was observed that the PAN nanofibers increased the fatigue resistance of asphalt binder at temperatures when the material is predominantly viscoelastic. These results show a promising new application of PAN nanofibers to improve the performance of asphalt pavements.

This paper investigates the flexural behavior of honeycomb sandwich panels with a toughened/untoughened interface using carbon fiber belt and short aramid fiber tissues. In the first part of the paper, bending response analysis of carbon fiber aluminum honeycomb sandwich plates with an untoughened interface is done using finite element-based first-order shear deformation theory. In the second part, experimental analysis is done to examine the effect of loading rates on the mechanical characteristics of plain and toughened sandwich panels using a three-point bending test. Four types of interface toughening are used as unidirectional and bi-directional stitches of carbon fiber belts, Kevlar short-fiber tissues, and carbon fiber belts combined with Kevlar short-fiber tissues. Experimental result shows that interface toughening improves the maximum load and energy absorbed by sandwich specimens for all loading rates. A scanning electron microscope is used to observe and analyze the failure mode and mechanism of strengthening the interface. It is observed that the stitch of the carbon fiber belt increases the adhesion contact between face sheets and core leading to prevent interfacial debonding. The peak load and energy absorptions of carbon fiber belts toughened interface sandwich are increased by 51 % and 42.5 %, respectively, compared with that of the plain sandwich by a small increment of weight (14%).

This work examines the influence of double diffusion on MHD Powell-Eyring fluid flow with free convection through a vertical surface. In addition, the impacts of chemical reaction, heat generation, local magnetic field, Grashof number and local modified Grashof number parameters are considered. The analysis of double diffusive in the occurrence of fluid flow under the convective surface conditions is studied. To translate the governing PDEs of velocity, energy and species (solutal) concentration equation, a couple of nonlinear ODEs we relate the suitable transformation of similarity. The set of nonlinear ODE's numerically and attained numerical consequences are connected by those gained through the assistance of MATLAB procedure bvp4c. The impact of prominent constraints of chemical reaction, Prandtl number, Schmidt number, heat source parameter, magneto hydrodynamic parameter, on dimension less velocity, energy and solutal (species) concentration dissemination has been considered. Impacts of different parameters such as skin friction coefficient, Nusselt number and Sherwood number are described through tables.

This work proposes a thermodynamically consistent phase-field model for anisotropic brittle material under the hypotheses of plane stress, small deformation and constant temperature. The model is derived from the principle of virtual power, the first and second laws of thermodynamics in the form of the Clausius-Duhem inequality. The degradation effect on the material behavior is given by a fourth-order degradation tensor introduced as an internal variable that evolves according to the current strain state rather than the conventional scalar degradation function of phase-field models. Therefore, local anisotropy can be induced, changing the material mechanical behavior differently in all directions organically. The proposed degradation tensor is defined in the global coordinate system and therefore is sensitive to any change in the principal directions of the strain and stress states. To demonstrate the model’s capability of representing damage in isotropic and transversely isotropic materials, some benchmark examples were carried out and the evolution of the damage components was analyzed.

Considering the significance of hybrid nanofluid over convectional fluid in terms of high rate of heat transfer, nanoscience and nanotechnology has been enhanced by dispersing nanoparticles in the base fluid to obtain new material with series of properties and applications. In this study, the analysis of chemically reactive squeezing flow conveying silica and titanium dioxide nanoparticles in water-based medium across two parallel plates with higher order velocity slip is carried out employing three different chemical kinetics for exothermic/endothermic reactions. The system of partial differential equations resulting from the fluid model assumed the ordinary differential form in alliance with appropriate similarity variables. The modified ordinary differential equations is simulated numerically in MATLAB software package using fourth order Runge–Kutta integration scheme in line with shooting techniques. The tested validity for limited case conform to preceding reports in the literature. The outcomes from the scrutiny uncovered in tables and graphs revealed that the velocity and temperature distributions of the hybrid nanofluid decrease steadily as first order slip factor varies from 0.2 to 1.0 but increase with second order slip factor at all levels of chemical kinetics. Moreover, for exothermic reaction, the rate of heat transfer decreases at the lower plate by $-221.923\%$ with increasing value of activation energy parameter when $m=-2,0,0.5$ but converse is the case in endothermic reaction as the rate of heat transfer increases by $106.382\%$.

Since the classical continuum theories are insufficient to account the small size effects of nanobeams, the nonlocal continuum theories such as Eringen's nonlocal elasticity theory, couple stress theory, strain gradient theory and surface elasticity theory have been proposed by researchers to predict the accurate structural response of isotropic and functionally graded composite nanobeams. This review focuses on research work concerned with analysis of size dependent nanoscale isotropic and functionally graded beams using classical and refined beam theories based on Eringen's nonlocal elasticity theory. The present review article also highlight the possible scope for the future research on nanobeams. In the present study, the authors have developed a new hyperbolic shear deformation theory for the analysis of isotropic and functionally graded nanobeams. The theory satisfy the traction free boundary conditions at the top and the bottom surfaces of the nanobeams. Analytical solutions for the bending, buckling and free vibration analysis of simply-supported nanobeams are obtained using the Navier method. To ensure that the present theory is accurate and valid, the results are compared to previous research.