Search

Interference fit is a classic issue in mechanical engineering. In this paper, under the axial/spherical symmetrical assumption, the analytical solutions for the interference fit problem of the internal and external functionally graded materials (FGMs) hollow cylinder/spherical shell are obtained. Herein, the unified form of the FGMs hollow cylinder/spherical shell basic equation is given by introducing a geometric parameter. The degradations of the analytical solutions in this paper are consistent with the corresponding results in the existing work. The effects of interference value, structural material parameters, and geometric dimensions on the displacement and stress distribution of FGMs structures are analyzed numerically. [ABSTRACT FROM AUTHOR]

• The magneto-elastoplastic behavior is investigated for functionally graded cylinder. • Critical pressures between different elastoplastic deformation states are given analytically. • Exact solutions of stress and displacement are obtained for different deformation states. • The residual stress caused by unloading internal pressure is solved analytically. With the development of composite material technology, the multi-field coupling analysis of functionally graded (FG) structures has attracted extensive attention. For FG cylindrical pressure vessels, due to the non-uniform distribution of stresses filed in the structure, plastic deformation occurs irreversibly under external load, and Lorentz's force under static magnetic field is also one of the key factors affecting the elastoplastic state. Assuming that the elastic modulus of FG cylinder changes as a power function along the thickness and Poisson's ratio is constant, the hollow cylinder under the combined action of applied magnetic field and internal pressure may have four deformation states containing pure elastic deformation, partial plastic deformation yielding from the inner surface, partial plastic deformation yielding from the outer surface, and full plasticity. In this paper, analytical solutions of stress and displacement fields of the FG cylinder under these four different elastoplastic states are given, and the critical load conditions corresponding to the transition between these four different states are proposed. The correctness of the present analytical solution in this paper is verified by comparing it with the existing results of related simplified problems. In addition, the analytical solution of residual stress distribution caused by unloading internal pressure is discussed for self-reinforcing processing. Based on the analytical solution in this paper, the influence of FG parameter, applied magnetic field and internal pressure on the elastoplastic state, plastic zone size, stresses and displacements distribution of FG cylinder is analyzed in detail. This study shows that for this magneto-elastoplastic problem of FG cylinder, plastic deformation may appear from the inner surface or outer surfaces. With the increase of FG parameter, the first yielding position of FG cylinder changes from the inner surface to the outer surface. In addition, the existence of an applied magnetic field reduces the critical internal pressure required for FG cylinders to yield, making the FG hollow cylinder more prone to plastic deformation. [ABSTRACT FROM AUTHOR]

The magnetic memory non-destructive testing method can evaluate the early damage such as stress concentration based on the magneto-mechanical effect. Some magneto-mechanical models have been proposed and applied to the mechanism explanation and theoretical analysis of this non-destructive testing method. The present work constitutes a continuing study in questing for a new magneto-mechanical model that is very concise, accurate, and easy to calculate. By introducing a new magnetostrictive expression with a concise and clear physical meaning, a new magneto-mechanical model is proposed under a constant weak magnetic field based on the thermodynamic framework and approach law. Particularly, compared with existing models, an analytical expression of anhysteresis magnetization is obtained for the first time under a constant weak magnetic field, which greatly facilitates the understanding and application of the magneto-mechanical effect. In comparison with the classic Jiles's model, the prediction accuracy is improved greatly based on the present model, particularly for the compression case. A detailed study has also been performed to reveal the effect of cyclic loading on the magneto-mechanical behavior. The present theoretical model established in this paper is hopeful to improve quantitative understanding of magneto-mechanical effects for the magnetic memory method. [ABSTRACT FROM AUTHOR]

The analytical solutions of the thermal distribution, mechanical distribution of displacement and stress for a rotating functionally graded material (FGM) thick-walled spherical pressure vessel are obtained under a uniform constant magnetic field. Here, the vessel is subjected to spherically symmetrical thermal and mechanical loads, and the FGM properties change as the power function along with the thickness of the pressure vessel in this paper. On the basis of the dynamic equation with the Lorentz force effect, the analytical solutions of various physical fields are obtained, where the finite difference method (FDM) is also given for this problem. The four simplified problems are solved as the special cases of our present analytical expressions. The present theory is verified by the comparison with the solutions in the existing works or the numerical results from FDM. In addition, the effects of different physical fields such as the mechanical, magnetic, and thermal fields on the coupling response of FGM spherical vessels are studied in detail. There are significant coupling effects on the distributions of displacement and stresses. The FGM thick-walled spherical vessel designed with suitable FGM parameters can realize the optimal regulation of displacement and stresses distribution. [ABSTRACT FROM AUTHOR]

• Developed an analytical MBN model considering surface modification layers. • The analytical model can quantitatively analyze experimental results. • The MBN intensity is positively correlated with the magnitude of the internal stress. • The MBN increases as the thickness of the surface modification layer increases. Surface treatment is a critical technology in engineering that enhances the mechanical properties of materials, in which the stress state within the material and the thickness of the surface modification layer are essential for optimizing performance. Magnetic Barkhausen Noise (MBN) serves as an effective nondestructive evaluation technique for ferromagnetic structures. In this work, we develop an analytical model that incorporates the attenuation mechanism of the MBN signal strength, and the strength of the stress-induced magnetic Barkhausen excitation (MBE) as determined by the magneto-mechanical constitutive law of the material. The proposed theoretical model can accurately characterize the MBN signal influenced by internal stresses and surface modification layers, as confirmed by comparison with existing experimental results. The theoretical analysis shows the influence of internal stress fields, layer dimensions, and electromagnetic properties on the MBN signal, revealing a positive relationship between signal intensity and the thickness of surface modification layer and the magnitude of internal stresses. This research provides a valuable reference for interpreting MBN signals and evaluating internal stress distributions for surface-modified ferromagnetic plates. [ABSTRACT FROM AUTHOR]

For the exact solution of the stress in the functionally graded (FG) cylindrical/spherical pressure vessel, this paper presents a unified form of the basic equations of the FG hollow cylinder/spherical shell by introducing parameter, and then, the axial/spherical symmetry mechanical problems of FG hollow shells are studied under three different boundary conditions, respectively. Assume that the Young's modulus of the material changes with thickness distribution of cylinder/shell in the form of power functions and the value of Poisson's ratio is constant, the analytical solutions of the displacement and stress of the FG hollow cylindrical/spherical pressure vessel are derived under different boundary conditions. By comparing the analytical solutions of the FG hollow cylinder/spherical shell obtained in this paper with the existing classical theoretical solutions and numerical solutions, the correctness of the analytical solution given in this paper is verified. In the numerical discussion, the distributions of displacement, radial stress and circumferential stress of the FG hollow cylinder/spherical shell under different gradient parameters and different size conditions are given, respectively. Finally, based on the difference numerical method, the stress distribution of FG hollow cylinder/spherical shell with the Young's modulus and Poisson's ratio along thickness distribution in the form of power functions is analyzed numerically. The results show that gradient parameter and geometric size have a great influence on the mechanical response of FG structure under different boundary conditions. [ABSTRACT FROM AUTHOR]

• The present comment corrects some analytical solutions in the classical papers. • The joint solution of FGM cylindrical and spherical pressure vessels is realized. • New analytical solutions of stresses distribution are obtained. • The correctness of the proposed analytical solutions is proved. In 2001, Naki Tutuncu and Murat Ozturk obtained analytical solutions for stress distribution of functionally graded material (FGM) cylindrical and spherical pressure vessels [COMPOS. PART. B-ENG, 32(8):683–686 (2001)]. The previous paper belongs to the classical study of elastic mechanics analysis of FGM, but their analytical expressions for the circumferential stress have some errors. The present letter corrects some analytical solutions in the classic problems of exact solutions for stresses in functionally graded pressure vessels. We prove correctness of the proposed analytical solutions by comparing with classical theory and finite element results. [ABSTRACT FROM AUTHOR]

Healing nanogap of metal nanowire is essential for the manufacturing and maintaining of nanoelectronic devices. Recent experimental study has demonstrated the feasibility of nanohealing in silver nanowire by using plasmonic heating. Here we report for the first time the effect of atomic lattice structures on the healing behavior and mechanism of silver nanowires due to plasmon, by using molecular dynamics simulation with a self-limited strategy. Three fundamental steps of the repair process are identified based on atomic behaviors, i.e. melting, recrystallizing, and healing. The five-fold twinned nanowires (FFTNW) is easier to get perfect healing than the single crystal ones. The near-perfect healing natures of FFTNW are mainly attributed to the non-linear stress distribution of cross section and the inherent five-fold twinned boundaries, which limit dislocation nucleating and provide self-healing nature. Our results provide a new microscopic perspective and understanding for the plasmonic nanohealing technology. [ABSTRACT FROM AUTHOR]

Functionally graded material (FGM) can optimize the mechanical properties of composites by designing the spatial variation of material properties. In this paper, the stress distribution of functionally graded panel with a central elliptical hole under uniaxial tensile load is analyzed. Based on the inhomogeneity variation and three different gradient directions, the effects of the inhomogeneity on the stress concentration factor and damage factor are discussed. The study results show that when Young's modulus increases with the distance from the hole, the stress concentration factor decreases compared with that of homogeneous material, and the optimal design of r-FGM is better than that of x-FGM and y-FGM when the tensile load. In addition, when the associated variation of ultimate stress is considered, the choice of scheme to reduce the failure index is related to the strength-modulus exponent ratio. When the strength-modulus exponent ratio is small, the failure index changes with the index of power-law, which means there is an optimal FGM design. But when the strength-modulus exponent ratio is large, the optimal design modulus design is to select a uniform material that maximizes the modulus at each point. These research results have a certain reference value for further in-depth understanding of the inhomogeneous design for FGM. [ABSTRACT FROM AUTHOR]

Magnetic memory method (MMM) is a newly developed passive nondestructive testing method, mainly used to detect the ferromagnetic materials. Because of the faster testing speed and the more convenient testing equipment, MMM has attracted many scholars' attention. This paper designed wide plate tensile specimens without and with a defect to study the influence of stress distributions on magnetic - flux - leakage (MFL) signals. The three - dimensional (3D) MFL signals on the specimen surface along the directions parallel (x- axis) and vertical (y- axis) to the loading direction were measured. Finite element method (FEM) simulation and digital image correlation (DIC) testing were performed as comparison. Then a theoretical model was applied in finite element method (FEM) software to calculate the MFL signals. The experimental results are essentially in agreement with the calculated results. It is shown that the MFL signals on the measuring lines both parallel and vertical to the loading direction are capable of describing the load magnitude and stress inhomogeneity. Besides, the MFL gradient is in agreement with the equivalent stress distribution along the loading direction. The magnitude of MFL gradient vector developed in this paper shows a good correlation with the equivalent stress distribution vertical to the loading direction. Finally, five characterization parameters were extracted to evaluate the stress inhomogeneity. Image 109 • Biaxial 3D Magnetic Flux Leakage Signals are used to evaluate the homogeneous and inhomogeneous stress distributions. • Two evaluation parameters can characterize the stress distributions parallel and perpendicular to the loading direction. • Five characterization parameters show good correlation with the degree of the stress inhomogeneity. [ABSTRACT FROM AUTHOR]