Mechanics of Solids最新文献

This paper focuses on the performance optimization of the control surfaces of aircraft. A two-scale optimization design method to enhance the mechanical properties of the control surfaces is proposed. Firstly, the topology optimization of the control surface structure is carried out to find the main load-bearing areas. Secondly, the periodic microstructure with the optimal stiffness is designed by joint optimization. After the above work is completed, the optimization results of the first step are reconstructed for the convenience of design and manufacturing. The periodic microstructures optimized in the second step are selectively filled according to the areas with concentrated material density, so as to obtain the configuration of the two-scale topology optimization design. By analyzing several structures, the obtained configuration is compared with the single-optimization configuration, the filled configuration and the traditional configuration respectively. The mechanical properties of the two-scale configuration are significantly improved under the premise of equivalent mass. Therefore, the numerical example results prove the effectiveness of the two-scale design combining macro and micro structure optimization.

A thermal shock problem in a hygrothermoelastic rod of length (l) is solved by the Laplace transformation technique. One end of the rod is subjected to a sudden heat source. The governing equations of the medium are transformed using Laplace transformation and the analytical expressions of displacement, moisture concentration, temperature distribution, and stresses are obtained. These transformed components are then inverted by the numerical inversion method and are presented graphically for different periods. The effect of moisture concentration is also shown through the graphical representations.

This study investigates the propagation pattern of barrel matrix cracks by analyzing the morphology and dimensions of radial cracks in barrels at different stages of life. A finite element numerical model was established for a chrome-plated barrel with an internal radial crack under thermal load, gas pressure load, and coupled load effects, capturing the stress response at the crack tip within the barrel bore under cracked conditions. Incorporating the results of crack morphology analysis, a relationship between the internal crack size and the number of projectiles fired was established, and an empirical model for crack propagation was developed. The critical crack size and the crack expansion life of the barrel at the dangerous cross-section were analyzed and compared. The results indicate that the most hazardous location of the barrel is at the rear part, which is subjected to high gas loads and has a thinner wall thickness. When the maximum chamber pressure exceeds 450 MPa, the theoretical safe service life of the barrel has decreased to a level comparable to the life required to maintain ballistic accuracy, at which point the safety of the barrel can no longer be assured.

In this research, a new type of external periodic supports is proposed and analyzed for vibration control in the main structure. These supports are connected beams with different lengths and boundary conditions periodically attached to the main structure. The Bloch theory combined with the generalized differential quadrature rule (GDQR) method is implemented to obtain the vibration band gaps. The impacts of the supports geometry on the first three bands are studied. Results indicate that the starting frequency of first band is zero for all supports geometries. Results also indicate that there are specific supports geometries in which the first and second bands or all three bands are attached to each other. Forced vibration responses obtained via ANSYS show that strong vibration attenuation occurs over the band gaps. All these results indicate that these new supports can be designed to strongly absorb the vibration waves in the main structure over a very wide frequency interval starting from zero frequency. The proposed periodic supports are suggested to be used for vibration control in the structures such as fluid-conveying pipes in practical applications. The forced responses implemented for verification of the GDQR indicates that vibration of the structures made of connected elements can be analyzed accurately and robustly using the GDQR.

In the present work, we study the influence of gravity, magnetic field and two-temperature on piezothermoelastic media considering the theory of Dual-phase-Lag “DPL.” The fundamental equations for the problem in the context of the phenomenon parameters and boundary conditions have been formulated. An analytic expressions for the displacement components, stress components, temperature, and the components of strain tensors are investigated using the technique of normal mode. The conditions for the Mechanical and Maxwell’s stresses and the temperature have been taken on the interface of the medium. The obtained results by applying the “DPL” theory are shown to be very close to each other except in determining one of the electric displacement components where the results differ and in general the effect of the presence of two-temperature, gravity, and magnetic field. The results obtained in the context of the new parameters and two theories are calculated analytically and displayed by graphs. A comparison has been made with the previous results obtained by others that show the impact of the new parameters. The theoretical and numerical computations are found to be in close agreement.

The article considers the motion of an inertial object with jet thrust in the absence of external forces while moving in a vertical plane. The problem is to transfer the object in a finite time to a chosen rectilinear horizontal trajectory with maximizing the terminal velocity, avoiding overshooting a given height. For the sufficiently large control times, the problem was solved by using the modified linear tangent law of the thrust direction control. Additionally, an asymptotic analysis was carried out. In particular, analytical results are obtained in the case of high thrust.

In this paper, a new approach is suggested to analyze the acoustic transmission of carbon nanotube (CNT)-reinforced doubly-curved multilayer composite shells by a three-dimensional (3D) theory, namely the State–Space Method coupled with the fourth-order Runge–Kutta algorithm (SSM-RK4). The properties of nanocomposite media are studied using the principle of mixing rules, which include a number of productivity parameters. Different CNT distributions have been considered, either homogeneous or functionally graded (FG) in the thickness direction. The state equation is firstly established in the sth layer of the considered structure by coupling the behavior law of structure, the equations of deformation and the movement equations according to the State–Space Methodology. The solution of the state equation in the sth layer is taken in the plane wave form, which has enabled us to transform the latter which a partial derivatives equation into a total derivatives equation. For the resolution, the fourth-order Runge–Kutta algorithm (RK4) is used to obtain the propagation matrix in the sth layer. The propagation of the solution in the structure yielded the overall transfer matrix for the structure. Acoustic boundary conditions were applied to obtain the Sound Transmission Loss (STL). Once the STL has been obtained, various representations are presented to check convergence. Not only the accuracy of this method is confirmed, but its importance is as well demonstrated by the reliability of the results obtained, particularly in the high-frequency range. Then, using this method, the effects of different volume fractions, of different CNT distributions, of ratio (radius/thickness), of incident angle and of geometry on the STL were briefly studied. Our results showed that these parameters have decisive and predominant effects on the acoustic insulation performance of CNT composite shells. Variations in these parameters shift the positions of the curvature and coincidence frequencies.

The general thermoelastic theory, based on Lord-Shulman (LS) theory with hyperbolic two temperatures, is used to analyze the magnetothermoelasticity problem in a semi-infinite material. The medium surface is caused by heat flux and is either taken to be traction-free or constrained as specified. Using Laplace transform techniques, the generalized magnetothermoelastic set of coupled basic equations is rewritten in the series of the matrix-vector differential equations and then solved by the eigenvalues method. The inversion of the transformation solutions is demonstrated in the space-time domains by the Riemann-sum approximation approach and graphically represented in two specific cases. It is demonstrated graphically how the conductive temperature (phi ), thermodynamically temperature T, displacement u, stress ({{sigma }_{{xx}}}), electric (E) and induced magnetic h fields were influenced by the hyperbolic two-temperatures parameter and magnetic field.

This paper addresses a novel approach to the construction of yield surfaces for the case of both proportional and non-proportional loadings, which are studied in the three-dimensional stress deviatoric space. For the mathematical apparatus, the Synthetic theory of irrecoverable deformation is utilized. The following three loading regimes are considered: uniaxial tension, uniaxial tension with subsequent torsion, and uniaxial tension with subsequent torsion in the opposite direction. The model results fit well with the 2024 T4 aluminum alloy experiments. Accounting for minimal computer time and requirements, the theory presented here is a promising method for predicting the deformation state of material subjected to various loading trajectories.