Transient Thermal Stress Research Articles

9% 니켈강 후판 용접부의 강도 및 잔류응력

In this paper, the transient thermal and residual stress analysis of the welding of 9% Ni steel plates using the FEA software ABAQUS are presented. The 9% Ni steel plates are welded manually with welding consumables of 70% Ni based Inconel type super-alloys (YAWATA WELD B (M)), producing a multi-pass/multi-layer butt weld. For these materials, temperature dependant mechanical and thermal material properties are used in the analysis. The back gouging is considered in welding process simulation. The FE thermal results are validated by comparing the real fusion profile and heat affected zone (HAZ). In addition, the continuous indentation test was conducted to measure the strength of base metal, HAZ and weld metal.

Transient Thermoelastic Analysis of a Solid Cylinder Containing a Circumferential Crack Using the C–V Heat Conduction Model

This article presents the transient thermoelastic analysis in a long solid cylinder with a circumferential crack using the C–V heat conduction theory. The outer surface of the cylinder is subjected to a sudden temperature change. The Laplace transform technique is adopted to solve the one-dimensional hyperbolic heat conduction equation, and the axial thermal stress is obtained for the un-cracked cylinder in the Laplace domain. Then this axial thermal stress with a minus sign is applied to the crack surface to form a mixed boundary value problem in the cylindrical coordinate system. A singular integral equation is derived by applying the Fourier and Hankel transforms to solve the mode I crack problem. The transient thermal stress intensity factors are obtained by solving the singular integral equation numerically. The influences of thermal relaxation time, crack geometry, and Biot's number upon transient temperature distributions, axial stress fields, and stress intensity factors are analyzed.

Nonlinear Transient Thermal Stress Analysis of Temperature-Dependent Hollow Cylinders Using a Finite Element Model

In this paper, the nonlinear transient thermal stress analysis is conducted for temperature-dependent hollow cylinders subjected to a decaying-with-time thermal field. By the finite element method, the highly nonlinear governing equations are solved. The time histories of temperature, displacement, and stress due to the decaying-with-time thermal load are computed. A sensitivity analysis includes the effects of exponent of the decayed heat flux and temperature-dependency of density and material properties is carried out. Numerical results show some interesting characteristics of the thermoelastic behaviors of the hollow cylinders studied. In particular, the effect of temperature-dependency of the material properties on the thermoelastic parameters was demonstrated to be significant.

Prediction of post fire load deflection response of RC flexural members using simplistic numerical approach

A simplistic approach towards evaluation of complete load deflection response of Reinforced Concrete (RC) flexural members under post fire (residual) scenario is presented in this paper. The cross-section of the RC flexural member is divided into a number of sectors. Thermal analysis is performed to determine the temperature distribution across the section, for given fire duration. Temperature-dependent stress-strain curves for concrete and steel are then utilized to perform a moment-curvature analysis. The moment-curvature relationships are obtained for beams exposed to different fire durations. These are then utilized to obtain the load-deflection plots following pushover analysis. Moreover one of the important issues of modeling the initial stiffness giving due consideration to stiffness degradation due to material degradation and thermal cracking has also been addressed in a rational manner. The approach is straightforward and can be easily programmed in spreadsheets. The presented approach has been validated against the experiments, available in literature, on RC beam subjected to different fire durations viz. 1hr, 1.5hrs and 2hrs. Complete load-deflection curves have been obtained and compared with experimentally reported counterparts. The results also show a good match with the results obtained using more complicated approaches such as those involving Finite element (FE) modeling and conducting a transient thermal stress analysis. Further evaluation of the beams during fire (at elevated temperatures) was performed and a comparison of the mechanical behavior of RC beams under post fire and during fire scenarios is made. Detailed formulations, assumptions and step by step approach are reported in the paper. Due to the simplicity and ease of implementation, this approach can be used for evaluation of global performance of fire affected structures.

The Welding Process as a Local Issue with Global Consequences

The welding process causes transient thermal stresses and non-continuous plastic strains around the weld due to the induced high temperatures. Uneven heating and cooling during the welding process cause a residual stresses in the welded member. The paper deals with the local influence of welding process and its global consequences at the creation and final redistribution of welding stresses. The paper also presents a verification of Modified empirical formulae, developed by the author, using experimental results of research program oriented to the effects of welding stresses and beams local stability [1, 2 and 3].

Thermal Stress Distribution Simulation Analysis for Disc Brake of Heavy Vehicles

Aiming at the phenomenon that a large amount of friction heat produced during braking process has important influence on the contact surface of heavy vehicle, according to the actual size of the friction plate and the static slice, a three-dimensional transient thermal stress field calculation model has established, using multi-physics coupled method of ANSYS in Workbench, after the numerical simulation of disk brake, the transient thermal stress field distribution has revealed in the process of braking friction piece, the results showed that the stress field and temperature field has a significant influence on each other, indicated that between them there is a clear relationship between the couple.

Parameter Analysis of Fluid-Solid Coupling for Wet Brake Disc

Due to the poor conditions of wet brake cooling and the high temperature of the working characteristics, this paper intended to introduce the oil film vadose between the brake linings, considered the variation of volume of grooves on the friction plate, and then proposes the three-dimensional transient dynamic response of fluid-solid coupling mathematical model. By parameter analysis of the disc transient thermal stress field distribution on the friction plate, and according to the real dimension of the brake disc, the distribution of the temperature and the stress of the wet brake disc during the braking are analyzed, the variation of temperature field and stress field in friction plate are obtained. The data curves shown the temperature and the stress are coupled. Finally, the results shows that the mathematical model is effective and feasible.

Parameter Analysis of Fluid-Solid Coupling for Wet Brake Disc

Due to the poor conditions of wet brake cooling and the high temperature of the working characteristics, this paper intended to introduce the oil film vadose between the brake linings, considered the variation of volume of grooves on the friction plate, and then proposes the three-dimensional transient dynamic response of fluid-solid coupling mathematical model. By parameter analysis of the disc transient thermal stress field distribution on the friction plate, and according to the real dimension of the brake disc, the distribution of the temperature and the stress of the wet brake disc during the braking are analyzed, the variation of temperature field and stress field in friction plate are obtained. The data curves shown the temperature and the stress are coupled. Finally, the results shows that the mathematical model is effective and feasible.

Nonlinear transient thermal stress analysis of thick-walled FGM cylinder with temperature-dependent material properties

In this paper, the problem of generalized thermoelasticity in a thick-walled FGM cylinder with one relaxation time is presented. The material properties are taking as function of temperature and graded in the radial. Due to the nonlinearity of the governing equations, finite element method is adopted to solve such problem. Both the inner and outer curved surfaces of the cylinder are stress free while the inner surface is subjected to thermal shock, while the outer surface is thermally isolated. The effects of temperature-dependent properties, volume fraction parameter and the thermal relaxation time on the physical quantities behavior are evaluated. Results confirm the efficiency of the present algorithm and reveal the significant effects of the temperature-dependent of the material properties.

Transient Thermoelastic Analysis of Pressurized Rotating Disks Subjected to Arbitrary Boundary and Initial Conditions

This paper focuses on exact analytical solution of transient thermoelastic behaviors of rotating pressurized disks subjected to arbitrary boundary and initial conditions. The pressure, inner radius, and outer radius are considered constant. The basic thermoelasticity theory under generalized assumptions is used to solve the thermoelastic problem. Using the method of the separation of variables, the relations of temperature and transient thermal stresses in the radial direction are obtained. In the case study, the disk is considered under heat flux. Some useful discussions and numerical examples are presented. The analytical results were compared with those of the finite element method and good agreement was found. The relations obtained in this paper can be applied to any arbitrary boundary and initial conditions.

Transient thermal stresses in functionally graded thick truncated cones by graded finite element method

In this paper, an axisymmetric thick truncated cone made of functionally graded materials under transient thermal loads based on classical theory of linear thermoelasticity is considered. The cone is made of a combined ceramic–metal material, and its material is graded through the thickness direction according to a power law distribution. Graded finite element method based on Rayleigh–Ritz energy formulation and Crank–Nicolson algorithm is used to solve the problem in time and space domain. Distributions of temperature, displacements and stresses for different power law exponent and semi-vertex angle of the cone are investigated. Results denote that the distributions of radial displacement are qualitatively similar for the cones and cylinders but the stresses are not and due to increasing the semi-vertex angle, the nature of radial, axial and tangential stresses near the small or large bases of the cone changes. The proposed method is verified by an example which is extracted from published literature and it shows very good agreement.

Investigation Methods for Thermal Shock Crack Problems of Functionally Graded Materials–Part I: Analytical Method

In most published papers, in order to obtain the analytical solution of the crack problems in functionally graded materials (FGMs), the thermomechanical properties of FGMs are usually assumed to be very particular functions and, hence, may not be physically realizable for many actual material combinations. Very few analytical methods can be used to solve the thermal shock crack problem of an FGM cylindrical shell or plate with general thermomechanical properties. In this article, a set of analytical methods is proposed for the thermal shock crack problem of an FGM plate or cylindrical shell with general thermomechanical properties. The crack problem of a cylindrical shell is modeled by a plate on an elastic foundation. Greatly different from previous studies, a set of analytical methods using both the perturbation method and a piecewise model are developed to obtain the transient temperature field and thermal stress intensity factor (TSIF). The perturbation method is applied to deal with the general thermal properties and the piecewise model is used to deal with the general mechanical properties. In the analytical procedure, integral transform, the residue theorem, and the theory of singular integral equation are used. Several representative examples are considered to check the capability of the present method. The transient thermal shock behavior of a ZrO2/Ti-6Al-4 V FGM plate with a surface crack and a Rene 41-Zirconia FGM cylindrical shell with a circumferential crack are analyzed.

Investigation Methods for Thermal Shock Crack Problems of Functionally Graded Materials–Part II: Combined Analytical-Numerical Method

Fractures phenomena can be often found in functionally graded materials (FGMs) subjected to thermal shock loadings. This paper aims to develop a set of analytical-numerical methods for analyzing the mixed-mode thermal shock crack problems of a functionally graded plate (FGP). First, a domain-independent interaction energy integral method is developed for obtaining the mixed-mode transient thermal stress intensity factors (TSIFs). A perturbation method is adopted to obtain the transient temperature field. Then an analytical-numerical method combining the interaction energy integral method, a perturbation method, and the finite element method is developed to solve the present crack problem. Particularly, the influences of the materials parameters, crack length, and crack angle on the TSIFs and the crack growth angle are investigated. The results show that the present analytical-numerical method can be used to solve the thermal shock crack problem with high efficiency. The present work will be significant for the fracture mechanics analysis and design of FGM structures.

Working Thermal Stresses in AlGaAs/GaAs High-Power Laser Diode Bars Using Infrared Thermography

An interesting approach is proposed for investigating the thermal stress of AlGaAs/GaAs laser diode bars using infrared thermography. We obtained horizontal and perpendicular profiles of the working thermal stress through the active region in one emitter (emitter 5) at operating currents 0.5 and 1.0 A. The thermal stress at the center of emitter 5 is found to quickly rise to values 2.1 and 3.4 MPa under the operating currents 0.5 and 1.0 A. The thermal stress gradient in the epitaxial layer is also larger than that in the substrate. In addition, if emitter 5 operates individually, a thermal stress spike at a current of about 0.2 A appears, with a sharper rise in slope between 0.1 and 0.2 A than between 0.2 and 1.0 A. Furthermore, with regard to the properties of transient working thermal stress, the profile of the thermal crosstalk between emitters was obtained at different operating currents.

Fracture analysis of a nonhomogeneous coating/substrate system with an interface under thermal shock

The work is devoted to establish a model for the interface problem of a nonhomogeneous coating/substrate system. In the model, according to the distribution of material properties, three types of interface problems are considered: (i) The material properties and their derivatives are continuous on the interface; (ii) the material properties are continuous, but their derivatives are discontinuous on the interface; and (iii) the material properties as well as their derivatives are discontinuous on the interface. In order to solve the complex interface problems, a transient interaction energy integral method (IEIM) is developed in this paper. The transient thermal stress intensity factors are evaluated using the IEIM combined with the finite element method and the finite difference method. The influences of the interface discontinuity and the geometric parameters on the transient TSIFs are investigated. Particularly, the crack growth behavior with different interface discontinuities is discussed.

Numerical analysis of the thermal and mechanical effects of laser windows of a high-power all-solid-state 2-μm laser system

The output window of a high-power laser system is vulnerable to damage, and this is the main limiting factor on the power scaling and structure integrity of the laser system. In endeavoring to obtain higher output powers from the laser system, the impact of the thermal and mechanical effects and the damage mechanism of the output window must be considered. In order to study these issues, a thermal model of the laser window is established based on the heat transfer and thermoelastic theories, and the expressions for the transient thermal and mechanical stress distributions of the output window are deduced in terms of the integral-transform method. Taking the infrared quartz window material as an example, the temperature and mechanical field distributions of a high-power all-solid-state 2-μm laser system window are simulated, and the laser-induced damage mechanism is deeply analyzed. The calculation results show that the laser window-induced damage is mainly caused by melting damage when the temperature exceeds the melting point of the material. The presented theoretical analysis and numerical simulation results are significant for the design and optimization of high-power laser windows. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this

Numerical Simulation on Stress Field in Inside-Beam Laser Cladding

In the process of deposition, the moving high energy heat source effect on the metal entity, and form the molten pool and the temperature field of directional conduction. Powder is accumulated in the substrate point by point, molten powder instantly solidify into a solid which is combined with substrate (or sediment) to reach metallurgical combination, from the perspective of the thermodynamic, the temperature field produced by coupling ring of heat source is regarded as a moving load to the base plate and the sedimentary section, and transient thermal stress field is generated, the load and boundary conditions (temperature field) of thermal stress field change over time, at the same time, the solution domain of thermal stress field change over time as a result. Therefore, through the life and death unit technology (ANSYS finite element analysis software of advanced analysis techniques) combined with the circulation order, the simulation of point to add deposition process is realized.

Description of the Thermo-mechanical Fatigue of Thick-walled Pressure Vessels

The paper discusses the issue of the modelling of strains and stresses resulting from heating and cooling processes of the components in power plants. The main purpose of this work is to determine the mechanical behaviour of power plant components operating under mechanical and thermal loading. The heat-transfer coefficients as time-dependent variables have been introduced. Computer FEM modelling of the temperature strain and stress fields with temperature measurements have been used as the methods of research. It is readily apparent from the stress versus time graphs that under unsteady operating conditions, components analysed in the paper, especially in the case of boiler restarts, may operate with transient thermal stresses which sometimes reach values higher than a yield point. Consequently, a thermo-mechanical fatigue process takes place in the materials of the components in question. The stress-strain diagrams for the selected points of the plant components have been determined. The paper will be a contribution to the justification of the necessity of the application of design methods of highly reliable pressure vessels, which take into consideration an influence of TMF processes on these vessels durability.

Effect of Michell function on the thickness of circular plate with internal heat generation

The present paper deals with the determination of displacement and thermal transient stresses in a thick ( ) circular plate with internal heat generation. External arbitrary heat supply is applied at the upper surface of a thick ( ) circular plate, whereas the lower surface of a thick ( ) circular plate is insulated and the heat is dissipated due to convection in surrounding through lateral surface. Here we compute the effect of Michell function on the thickness of circular plate with internal heat generation. The governing heat conduction equation has been solved by using integral transform method and the results are obtained in series form in terms of Bessel's functions and the results for temp erature change and stresses have been computed numerically and illustrated graphically. Keywords:Thick plate ( ) Thin plate ( ) , internal heat generation, thermal stresses.

210 太陽集光を受ける組合せ円板の非定常平面軸対称熱応力解析

210 太陽集光を受ける組合せ円板の非定常平面軸対称熱応力解析