Large Deflection Analysis of Bimodular Functionally Graded Truncated Thin Conical Shells Under Mechanical and Thermal Loads.

A physics-based model of residual stress in minimum quantity lubrication (MQL) machining is presented. The stresses resulting from thermal and mechanical loading in the MQL machining process are coupled into an incremental thermal-elastic-plastic model for predicting the final resultant residual stress in the machined workpiece. Comparative analysis is made between the stresses produced by the thermal load and mechanical load in the machining process. Results manifest that for the surface of the machined workpiece, the stress produced by thermal load is on par with the contact stress produced by mechanical load in the magnitude. With the increase of depth into the workpiece, the stress produced by mechanical load is dominant of the total stresses. The rationale demonstrates that thermal load is prone to generate the tensile residual stress at the surface of the machined workpiece, while the mechanical load is prone to generate the compressive residual stress at the surface of the machined workpiece. Finally, the residual stress prediction model is verified by orthogonal cutting of AISI 4130 alloy steel.

The present paper addresses the thermo piezo magneto elastic behavior of a functionally graded piezomagnetic cylinder under thermal, magnetic and mechanical loads. All mechanical, thermal and magnetic properties are graded in the radial direction. The cylinder is subjected to inner pressure, thermal and magnetic loads. Temperature distribution can be obtained using solution of the heat transfer equation with general boundary conditions. Employing the equilibrium relations for both mechanical and magnetic components presents two basic equations for derivation of unknown functions. After solution of the problem, the distribution of the mechanical and the magnetic components can be presented for different values of non homogenous index. The effect of non homogenous index on the mechanical and magnetic distribution presents best optimization for intelligent manufacturing and design of the materials. Used material in this paper can be considered as a sensor for determination of the physical components and as an actuator in the micro positioning. Uniform distribution of the mechanical or the magnetic components can be obtained for special value of non homogeneity. These uniform distributions have many advantageous conditions for designer and manufactures. Key words: piezomagnetic, non homogenous index, solution, root.

Subinterfacial cracks in bimaterial systems subjected to mechanical and thermal loading

The geometrically nonlinear response of a circular sandwich plate that consists of two face sheets and a compliant (“soft”) core with mechanical properties that may be either independent or dependent of temperature and subjected to both mechanical loads and thermal induced deformations, but remain elastic linear throughout the loading process, is presented. The mathematical formulation follows the principles of the high-order sandwich panel theory (HSAPT) and includes the vertical flexibility of the core in addition to the temperature dependency of the mechanical properties of the core material. The mathematical formulation outlines the set of governing partial differential equations as well the appropriate boundary conditions for a general sandwich layout. The particular case of an axisymmetric circular sandwich plate subjected to axisymmetric mechanical and thermal loads, and with axisymmetric boundary conditions is studied analytically and numerically. The numerical study includes an interaction of mechanical and thermal loads which is presented through results within the plate for various load levels of various structural quantities as well as equilibrium curves of temperatures versus these structural quantities. The results reveal that the combination of mechanical and thermal loads along with a compliant core material with mechanical properties that degrade with increasing temperatures shifts the behavior from a linear and stable (strength controlled) response into a strongly nonlinear response with limit point behavior and associated loss of stability, when large displacements and large rotations (geometrical nonlinearity) are included in the modeling.

This article focuses on parametric instability of rotating functionally graded (FG) truncated conical shells reinforced by graphene platelets (GPLs) and subjected to both mechanical and thermal loading conditions. The GPL nanofillers are uniformly dispersed in each concentric conical layer but its weight fraction varies continuously along thickness direction, which induces the position-dependent effective material properties. Based on Love’s thin shell theory and Galerkin approach, the equations of motion for the conical shells are derived with the effects of the periodic axial loads, thermal expansion deformation, rotation-induced initial hoop tension, gyroscopic and centrifugal forces taken into account. Then, the parametric instability under combination parametric resonance for the conical shells is performed by the method of multiple scales, and the analytical solutions of both instability boundaries are obtained. A comprehensive parametric study is conducted which focuses on instability regions and vibration characteristics of the conical shell. Of particular interest in this process is the combined effect of the rotation, dynamic loads and thermal effects on dynamic stability of FG-GPL reinforced truncated conical shells.

Influence of inclusion on the stress intensity factors under thermomechanical loads in a PM superalloy

This study deals with the effect of coupled thermal and cyclic mechanical loadings on the viscoelastic response of carbon black filled nitrile rubber. For this purpose, cyclic loading tests were performed at different temperatures by means of Dynamic Mechanical and Thermal Analysis (DMTA). The type and level of the thermomechanical loadings applied were chosen in order to determine the relative contribution of each of the mechanical and thermal loadings (and their coupling) to the viscoelastic response during the cyclic tests. X-ray Photoelectron Spectroscopy (XPS) and Fourier Transformed Infrared spectroscopy (FTIR) analyses were also carried out to track the change in the chemical structure corresponding to the evolution in the viscoelastic response. First, results obtained show that due to the crosslink increase, the storage modulus increases with the number of cycles. It is also observed that temperature amplifies this phenomenon. Second, the cyclic mechanical loading is found to significantly amplify the effect of temperature.

The numerical assessment of elastic-plastic sheets under variable mechanical and thermal loads using a simplified two-surface yield condition

This paper addresses load order effects on elastic-plastic J estimation under combined mechanical and thermal loads for circumferentially cracked pipes. The load order effects, for various thermal gradient types and mechanical loading, are evaluated for a range of magnitudes of the loadings, crack sizes and material hardening. Variations of elastic-plastic J obtained by finite element analysis are compared with existing and proposed methods for use with the R6 defect assessment procedure. The load order effects are presented on the R6 failure assessment diagram (FAD) by calculating the two parameters Kr and Lr from the finite element results. It is shown that there are significant load order effects at large secondary stress cases but these are successfully treated by simplified methods proposed for use with R6.

Nonlinear dynamic analysis of Sigmoid functionally graded circular cylindrical shells on elastic foundations using the third order shear deformation theory in thermal environments

For aerospace vehicles, such as rockets and satellites that are subjected to high mechanical and thermal loading, it is necessary to better understand how the structure is influenced by these loads. Because reducing the mass of the structure while maintaining strength is a very important requirement, field-tested components will be subject to different SFs (safety factors) than those that are only subjected to FEA (Finite Element Analysis). Also to further reduce the magnitude of the load factors in the MOS (Margin of Safety) calculation, mechanical loads are considered to have a different safety factor than the thermal loads. This paper proposes a solution, a tool developed to calculate MOS for structural parts for different safety factors on mechanical and thermal loads, based on data obtained from FEA. The tool takes as input the results from the NASTRAN result files and creates one excel file with MOS for each component requested by the user and different types of summary.

ABSTRACTIn this study, a locking-free six-node triangular shell element is proposed to nonlinear analysis of shell structures under the effects of both thermal and mechanical loads. Total Lagrangian formulation is used to consider large deflections and rotations. Besides, mixed interpolation of tensorial components is applied in the relations to deviate shear and membrane locking. The effects of temperature on the nonlinear deflections of shells are studied in several numerical examples. Moreover, analytical solution will be proposed for large deflection analysis of cantilever and simply supported beam under the thermal loads. To validate the proposed formulation, the finite element analysis results are compared by analytical solutions. Based on the obtained results of linear and nonlinear problems, it will be depicted that the authors’ scheme is capable for thermomechanical analysis of shell structures accurately.

Investigations on structural intensity in nanoplates with thermal load

This paper presents an analytical solution for the thermomechanical buckling of functionally graded material (FGM) sandwich plates. The solution is obtained using a four-variable equivalent-single-layer (ESL) plate theory. Two types of sandwich plates are included: one with FGM facesheets and homogeneous core, and vice versa for the other. The governing equations are derived based on the principle of minimum total potential energy. For simply supported boundary conditions, these equations are solved via the Navier method. The results on critical buckling load and temperature increment of simply supported FGM sandwich plates are compared with the available solutions in the literature. Several results are presented considering various material and geometrical parameters as well as their effect on the thermomechanical buckling response of FGM sandwich plates. The relationship between the mechanical load and the temperature increment for uniform/linear temperature rise of FGM sandwich plates under combined mechanical and thermal loads is studied.

The paper is discussing a method of increasing the reliability of on-board electronic equipment at the early stages of its design. Authors offer to evaluate and provide deterministic reserves for thermal, mechanical and electrical loads to electronic components using special simulation software. Determinacy of reserves loads on the electronic components is achieved by a result of complex modeling as additional indicators of reliability. The main methods of reliability indicators calculation conducted in enterprises are probabilistic, which are averaged and do not lend themselves to practical verification during testing. Complex modeling of destabilizing effects on the printing circuit board of designed on-board equipment allows to achieve the required reserves on the electrical, thermal and mechanical loads with respect to the maximum permissible temperatures, vibration and shock acceleration in the electronic components, which leads to the guaranteed provision of high levels of reliability.