Temperature-dependent Material Characteristics Research Articles

Thermoelastic free vibration of rotating tapered porous functionally graded conical shell based on non-polynomial higher-order shear deformation theory

This study uses a non-polynomial higher-order shear deformation theory to calculate the fundamental frequency of a rotating cantilevered porous functionally graded (FG) conical shell with variable thickness. Eight noded isoparametric shell elements having seven degrees of freedom per node are used to discretize the shell. Utilizing a simple power law, the temperature-dependent material characteristics of the FG conical shell are determined. The one-dimensional Fourier heat conduction equation is used to obtain the nonlinear temperature distribution. Lagrange’s equation is used to derive the dynamic equation of motion. Finally, a parametric study is presented.

Optimization of functionally graded plates under Thermo-elastic free vibration using nature-based algorithms

This article presents the parametric optimization of the free vibration characteristics of a functionally graded material (FGM) plate exposed to nonlinear thermal loading using the finite element method and nature-based algorithms. The one-dimensional (1D) Fourier heat conduction equation is used to calculate temperature distributions over the thickness of the plate. Using Lagrange’s equation, we get the dynamic equation of motion for the plate. An eight-noded iso-parametric plate element with five degrees of freedom per node is used in the finite element formulation based on first-order shear deformation theory. Rectangular plates have temperature-dependent material characteristics; the thickness of the plates is scaled using a straightforward power law distribution. Here, the investigation of the FGM plate is conducted with two different boundary conditions, such as simple support and fully clamped. Additionally, new hybrid optimization approaches, namely RSM-Composite Desirability Optimization (RSM-CDO), Whale Optimization Algorithm (WOA), Corrected Moth Search Optimization (CMSO), Lichtenberg Algorithm Optimization (LAO), Sunflower Optimization Algorithm (SFO), and Forensic-Based Investigation Algorithm (FBI), are utilised to determine the best optimal solution, and the obtained findings are validated using confirmatory tests.

Mechanical ANSYS Parametric Design Language Friction Stir Welding Simulation of AZ31B-H24 alloy

This paper presents a numerical simulation of temperature distribution in magnesium alloy AZ31B-H24 plates due to Friction Stir Welding. For this aim, a model based on finite elements, using Lagrangian formulation is implemented in Ansys Parametric Design Language. Temperature-dependent material characteristics and a temperature-dependent coefficient of friction are implied by the model, using theoretical mathematical formulae. In addition to this, heat generation is also considered. This model is validated with the experiment and showed a good agreement. The maximum temperature results obtained are at the rotational speeds of 1500 and 1600 rpm with feed rates varying as 80,100,120 mm/min. The deviation between experimental maximum temperature and theoretical was observed as an average value of 4 per cent. The maximum temperatures are lesser than the melting point temperature of AZ31B alloy.

Finite element investigation on pretreatment temperature-dependent orthogonal cutting of unidirectional CFRP

Mechanical properties and related machinability of carbon fiber reinforced polymer (CFRP) composites have a significant temperature dependence. In the present work, we elucidate the thermal-mechanical coupled material removal mechanisms of unidirectional CFRP composites with thermal and cryogenic pretreatments in orthogonal cutting by means of macro-scale finite element (FE) simulations. A thermal-mechanical FE model constituted with temperature-dependent constitutive law for CFRP as an equivalent homogeneous material is established. Furthermore, the failure behaviors of fiber reinforcement and polymer matrix is jointly characterized by Hashin and Puck fracture criteria, and a fracture energy-based damage propagation algorithm is proposed to account for the post-damage degradation behavior. The microscopic deformation mechanisms of 90°-oriented CFRP under orthogonal cutting, as well as their correlations with macroscopic cutting results in terms of cutting temperature evolution, machining force evolution, chip formation, subsurface damage and machined surface integrity, are firstly investigated by FE simulation and corresponding experiment performed at room temperature. Subsequent FE simulation results demonstrate significant temperature-dependent material characteristics of CFRP, i.e., cryogenic embrittlement and thermal softening, which have strong impacts on subsequent cutting processes. Furthermore, the coupling effect between fiber orientation and pretreatment temperature on the CFRP cutting is also addressed. Current findings provide guidelines for the rational design of temperature pretreatment strategy for enhancing machinability of CFRP composites.

Methodology of determining material parameters based on optimization techniques

A methodology for finding unknown or unavailable parts of temperature-dependent material characteristics is presented. Knowledge of these parts is of great importance for solving problems connected with processing of metals at high temperatures where phase changes take place, such as welding or cladding. The paper presents a technique of calibration of these characteristics based on evaluation of experimentally obtained heat-affected zones and allows discovering not only the basic features of the characteristics, but also eventual breaks and other anomalies. The results obtained are illustrated with two examples taking into account the keyhole effects: laser welding and laser cladding. The functionality and efficiency of particular algorithms is also evaluated.

Thermal stresses of flexible pavement with consideration of temperature-dependent material characteristics using stiffness matrix method

The asphalt pavement is regarded as a multilayered elastic half space axisymmetrical body. By introducing the relationship between material characteristics and temperature into the fundamental equations of thermoelasticity and using mathematic methods of Laplace and Hankel integral transformation, the stiffness matrix for a layer is derived firstly. Then the global stiffness matrix is established for multilayered elastic half space using the finite element concepts in which layers are completely contacted. Therefore, explicit solution for thermal stresses of the asphalt pavement is obtained from the solution of the algebra equation formed by global stiffness matrix and the inverse Hankel and Laplace integral transformation. Because the elements of matrix do not include positive exponential function, the calculation is not overflowed and the shortages of transfer matrix method are overcome. This approach serves as a better model for real pavement structure as it takes into account the relationships between the material characteristics and temperature in the pavement system.

Thermal stresses of asphalt pavement under dependence of material characteristics on reference temperature

This thesis presents an analytical study of thermal stresses of asphalt pavement under dependence of material characteristics on reference temperature. In the analysis, flexible pavement is regarded as a multi-layered elastic half-space axisymmetrical system. Firstly, thermo-elastic theory is used to describe thermal stresses of a multi-layered system, while the temperature-dependent material characteristics are considered. Then Laplace transformation and Hankel transformation with respect to time and radial, respectively, are utilized for thermo-elastic equations of equilibrium. In addition, the transfer matrix method is applied to derive general solutions for the multi-layered problem. Finally, the resulting formulation is applied to calculate thermal stresses in the low temperature cracking problem of asphalt pavement. Thermal stress is calculated and compared with the case that material characteristics are supposed to be constant to show the remarkable impact of temperature-dependent material characteristics on thermal stresses of asphalt pavement.

Experimental Study on Aerothermal Heating Caused by Jet-Hypersonic Crossflow Interaction

The present paper reports on the results of an experimental study on aerothermodynamic effects associated with the injection of a laterial jet into a hypersonic cross-flow around a generic missile model. This study intends to close the gap of missing reliable information on measured combined surface pressure and heat flux distribution on a missile configuration with laterial jet. The model consisting of a cone, cylindrical main body and a flare includes a single side jet hole. The model is made of a material with low thermal conductivity, in order to visualize the surface temperature distribution, i.e. heat fluxes. The surface temperature development on the model has been measured by IR thermography. Using this data the heat flux rate has been determined taking into account temperature-dependent material characteristics, assuming a semi infinite wall and the exchange of radiative cooling to the environment. Flow topology was analyzed using oil flow and Schlieren images and wall pressure distribution measurements. The experimental data show that the jet pressure ratio has a significant effect on the side jet flow topology and its interaction with the cross-flow. The influence of the angle of attack and the yaw angle on the pressure and heat flux distribution has also been measured clearly. Finally the effect of various side jet gas media on the flow interaction has been demonstrated with tests using argon and helium as a jet gas complementary to air.

Analysis of Bending Effects on Performance Degradation of ITER-Relevant $\hbox{Nb}_{3}\hbox{Sn}$ Strand Using the THELMA Code

The modeling of the effects of bending on single strand DC performance (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> , n index) is presented for a bronze-route strand subjected to the same loading conditions as in an experiment performed at JAEA Naka, Japan [Y. Nunoya, , IEEE TAS 14 (2004) 1468-1472]. The strand is discretized in strand elements (SE) representing groups of twisted filaments in the bronze matrix, and in portions of the outer Cu annulus, electro-magnetically coupled in the THELMA code. The 3-D strain map in the filament region is computed with a newly developed, detailed thermo-mechanical model accounting for non-linear, temperature dependent material characteristics. With respect to our previous analysis [P.L.Ribani, , IEEE TAS 16 (2006) 860-863] several new updated ingredients, besides the new thermo-mechanical model, are used here, including more accurate thermal and mechanical properties for the materials, a jacket-like model for the outer Cu layer, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> and n index (interpolative) scaling from Durham University. The simulation results show an improved agreement with the experiments, in the degradation of the single-strand performance due to bending.

THELMA Code Analysis of Bronze Route&lt;tex&gt;$rm Nb_3rm Sn$&lt;/tex&gt;Strand Bending Effect on&lt;tex&gt;$rm I_rm c$&lt;/tex&gt;

The THELMA (Thermal-Hydraulic-ELectro-MAgnetic) code has been developed with the aim of simulating the main aspects of superconductors to be used in the coils of the International Thermonuclear Experimental Reactor (ITER). An application of the code is presented here, where THELMA is used to simulate a single strand by considering, as cable elements, groups of superconducting (SC) filaments and the corresponding portion of the resistive matrix. This approach is used to reproduce the voltage-current characteristic of a Nb3Sn bronze route strand when subject to a bending mechanical load. Attention is focused particularly on the effect of the applied mechanical load on the critical current, which is considered a relevant item in the explanation of the degradation of the coil performance observed in several ITER Model and Insert Coil experiments. The longitudinal strain of the SC filaments is calculated by means of a composite beam model of the strand, taking into account the nonlinear, temperature-dependent material characteristics of the components. The whole load history is simulated, computing first the thermal strain due to cool-down, and then the mechanical strain due to the bending at 4.2 K