Archive of Applied Mechanics最新文献

The thermomechanical buckling of imperfect sandwich plates made of functionally graded material (FGM) is addressed analytically in this study. A novel hyperbolic four-variable integral shear deformation theory is used to arrive at the solution. Sandwich plates come in two varieties: the first with homogeneous core and FG face sheets and the second with the opposite. The displacement field is constructed using undetermined integrals in order to reduce the number of unknown variables which consequently reduces the calculation time unlike other similar theories. The proposed model does not require a shear correction factor and ensures the free-stress at the upper and lower surfaces of structure. The materials properties of the structure are computed via power-law function with considering the porosity effect which may appear during manufacturing due to the difference in solidification temperature of the constituents (ceramic/metal). Four types of geometric imperfection are examined with even, uneven, logarithmic uneven and linear uneven distributions. On the basis of the minimal total potential energy concept, the governing equations are developed. The Navier’s method is used to solve these equations for simply supported plates. The results of simply supported FGM sandwich plates' critical buckling load and temperature increment are contrasted with the available solutions in the literature. Even, uneven, linear uneven and logarithmic uneven models of distribution are taken into consideration and studied in order to incorporate porosity in the FG face sheet and core. Investigation is conducted into the effects of layer thickness, porosity models, porosity coefficients and geometrical parameters on the thermomechanical buckling response of imperfect FG sandwich plates.

This paper investigates the behavior of a medical guidewire within a vessel with a specific focus on its buckling, commonly known as tip load. The guidewire is simulated as a variable section microshaft embedded in an elastic environment, and a comprehensive buckling analysis is carried out based on the modified couple stress theory (MCST). The fundamental frequency is determined by applying Hamilton’s principle and Rayleigh’s method. A formula for calculating the buckling force is subsequently introduced. Numerical simulations were conducted to analyze the impact of the material properties, tapered tip length, core thickness, slenderness ratio, and material length scale parameter on the tip load and penetration force. Furthermore, a comparative study was carried out to validate the proposed formulation. The findings derived from this research can provide valuable insights for the optimization and exploration of various parameters related to medical guidewires. The findings indicate that coronary guidewires with lengths exceeding 10 cm exhibit minimal variations in tip load, whereas those with lengths below this threshold experience a substantial decrease of 65–75% in both tip load and penetration force when the length is doubled. In addition, nitinol guidewires demonstrate greater flexibility, with their tip load being nearly 75% lower than that of stainless steel guidewires of equivalent dimensions. Moreover, there is a notable increase in penetration force with an expanding radius, with tapered tips resulting in an approximate 20–30% increase in penetration force.

Modified Green–Lindsay generalized thermoelasticity theory was established by Yu et al. (Meccanica 53(10):2543–2554, 2018). On the basis of this theory, transient motions remove discontinuities in displacement fields. The goal of this article is to address a dynamical problem involving finite linear mode-I cracks in an isotropic and homogeneous elastic medium in a two-dimensional infinite space using the innovative framework of modified Green–Lindsay generalized thermoelasticity theory. There is a specified temperature and stress distribution on the crack’s boundary. The integral transform techniques are used to obtain the numerical values of temperature, stress, displacement and stress intensity factor for copper material. These non-dimensional physical fields are explained graphically. Specifically, the present undertaking demonstrates its utility in addressing challenges related to fracture mechanics, geophysics and mining particularly in the context of coupling thermal and mechanical fields. This concerted effort proves valuable in exploring and resolving issues within these fields.

The predictive capability of an anisotropic yield function highly relies upon the number of the model parameters and its calibration type. Conventional calibration of a plane stress anisotropic yield function considers material behavior in uniaxial and equi-biaxial stress states, whereas it violates shear and plane strain loading conditions. In this study, the direction of the plastic flow in both loading regions was corrected by including shear and plane strain constraint terms to the conventional calibration of the Yld2000 function, and its effect on the sheet metal forming simulations, namely cup drawing and hole expansion tests, was investigated. Two highly anisotropic sheet materials (AA2090-T3 and low-carbon steel) were selected for the investigation, and the anisotropy coefficients were determined. Stress anisotropy was accurately predicted by the conventional method, whereas any decrease in the prediction of the deformation anisotropy could not occur by the applying of the constrained methods. Significant increases in the predicted cup height and differences in the number of the ears were observed by shear constraint identification in the cup drawing. The maximum thinning location in the hole expansion test could be accurately predicted by plane strain constraint identification.

This work is dedicated to the modeling and solution of eigenvalue problems within shear deformation theory (SDT) of laminated cylindrical shells containing nanocomposite plies subjected to axial compressive load in thermal environments. In this study, the shear deformation theory for homogeneous laminated shells is extended to laminated shells consisting of functionally graded (FG) nanocomposite layers. The nanocomposite plies of laminated cylindrical shells (LCSs) are arranged in a piecewise FG distribution along the thickness direction. Temperature-dependent material properties of FG-nanocomposite plies are estimated through a micromechanical model, and CNT efficiency parameters are calibrated based on polymer material properties obtained from molecular dynamics simulations. After mathematical modeling, second-order time-dependent and fourth-order coordinate-dependent partial differential equations are derived within SDT, and a closed-form solution for the dimensionless frequency parameter and critical axial load is obtained for first time. After the accuracy of the applied methodology is confirmed by numerical comparisons, the unique influences of ply models, the number and sequence of plies and the temperature on the critical axial load and vibration frequency parameter within SDT and Kirchhoff–Love theory (KLT) are presented with numerical examples.

In this work, the sound transmission loss (STL) of a simply supported doubly curved shallow aluminum shell covered by two layers of piezoelectric material, PZT-5H is presented. The study takes into account the presence of uncertain ambient temperature which is shown to significantly affect piezoelectric control of sound transmission. To derive the equations of motion, the assumed mode method combined with the first-order shear deformation theory and Hamilton's principles are employed. The modeling process incorporates the ambient temperature and thoroughly investigates its effects on STL, vibrational displacement, and piezoelectric voltage in terms of thermal strain, piezoelectric constants, and the pyroelectric coefficient uncertainties. Results show that uncertainty in environmental temperature significantly affects STL uncertainty up to 10% and vibrational displacement of the shell to the 15 times of its lowest value. The piezoelectric voltage also fluctuates with the variation in the temperature in a maximum range of 0.12–5.2 Volt. Further, the piezoelectric sensing voltage which accounts for the piezoelectric sensor thickness is observed to be highly sensitive to the temperature uncertainty with a maximum range of 0.65–7.6 Volt, causing depolarization and hysteresis nonlinearity. Thus, environmental temperature variation is considered as one of the main uncertain aspects for robust sound transmission controller. The proposed study provides an insightful investigation for robust piezoelectric control of STL in the presence of thermal uncertainty.

This study investigates vibrations of the laminated composite beam (LCB) subjected to axial load and settled on Winkler–Pasternak elastic foundation. The beam model is of Euler–Bernoulli type with cubic order nonlinear elastic load. Two different boundary conditions are considered: (i) Simply Supported (S–S) and (ii) Clamped–Clamped (C–C) ones. Mathematical model of the asymmetric LCB is a partial differential equation. Applying Galerkin procedure, the model is converted into a strong nonlinear ordinary equation. In the paper, the new analytical method, dubbed as the Max–Min Approach (MMA), is adopted to provide more accurate nonlinear analysis of beams. The analytical solution is inferred to investigate the effects of axial force and essential elasticity parameters of foundation on the nonlinear response of the beams. Analytical results are compared with numerical solutions and show good agreement. In addition, the results are compared with previously published ones. It is concluded that MMA used in LCB gives more accurate results than the previously used analytic methods and is practical applicable. The method can be easily extended to high nonlinear vibration problems in LCB under different boundary conditions.

The industrial standard in the design and development process of NVH (Noise Vibration Harshness) characteristic of brakes is the application of Finite Element (FE) models with a high number of degrees of freedom in the range of one or several millions. Nevertheless, parallel experimental investigations are still indispensable. On the other hand, minimal models with, due to the inclusion of the self-excitation process, at least two degrees of freedom are well known to be capable to explain qualitatively phenomena as instability of the desired non-vibrating solution or limit cycle oscillation but are in general very inaccurate in predicting the dynamics of a specific real brake. This is because the underlying physical assumptions are already too restrictive and model parameters (especially those referring to nonlinearities) are widely unknown. To overcome this problem, the data-driven modeling approach SINDy (Sparse Identification of Nonlinear Dynamics) is applied to identify appropriate nonlinear functions for a brake squeal minimal model. A problem thereby is the limited database. It turns out that the naive implementation of the method yielding the lowest possible residuum does not necessarily provide physically meaningful models and results, respectively. Instead, a constrained model that incorporates physical knowledge is used to robustly identify parameters and reproduce realistic dynamic behavior. Thereby, several appropriate models with coexisting limit cycles and stationary equilibrium are identified. In particular, it was found that the angular position of the brake drum has a significant influence on the model parameters and therefore must be taken into account in a model with long-term validity.

Peridynamics describes the material in a non-local form and is very suited for the simulation of dynamic fracture. However, one significant effect regarding dynamic fracture is the correct handling of elastic deformation, like the pressure and tension waves inside a body, due to dynamic boundary conditions like an impact or impulse. Many peridynamic material formulations have been developed with differences in this regard. This study investigates the elastic wave propagation characteristics of bond-based, ordinary state-based, continuum kinematics-inspired peridynamics and a local continuum consistent correspondence formulation. Multiple parameters of a longitudinal pressure wave inside an elastic bar are studied. While all formulations demonstrate adequate wave propagation handling, all except the correspondence formulation are sensitive to incomplete horizons. The local continuum consistent formulation does not suffer from the surface effect and models the wave propagation with perfect accuracy.

In this study, we propose a structural health monitoring and diagnostic method for layered (multi-story) structures using a convolutional neural network (CNN). The proposed method is a primary diagnostic one, and its purpose is to allow quick identification of the location of an abnormality after detecting it. An abnormality is defined as a decrease in the stiffness characteristics (spring constant) of the outer wall of a multi-story structure when it deteriorates or is damaged. The proposed method has the following features. A modal circle is generated by multiplying the frequency response functions (FRFs) simulated by a mathematical model and the FRFs from the actual structure, in frequency space, and then a CNN learns the features of the abnormality from the modal circle and diagnoses it in the actual multi-story structure. We first verified the validity of the proposed method by considering a three-story structure as a numerical example. When the method was applied to three types of abnormal conditions, it was shown that the abnormal diagnosis could be performed correctly. Next, we constructed an experimental model of a three-story structure, and realized three types of abnormal conditions similar to those in the numerical model. We verified the applicability of the proposed method and showed that correct diagnosis of an abnormality was possible. Both the validity and applicability of the proposed method were thus confirmed.