Transient Stress Analysis Research Articles

Inverse analysis method of molten shape by deep learning

Most structural damage occurs in welds, and transient stress analysis corresponding to the welding procedure is performed to investigate the cause. To accurately reproduce the stress generated in the welds, it is necessary to accurately reproduce the transient heat input in the welding procedure. Thus, traditionally, inverse analysis on the transient heat input is conducted by focusing on the molten shape of the actual components; i.e., try and error work performing transient temperature distribution analysis assuming heat input until the molten shape is reproduced. Goldak's double-ellipsoidal heat source model was used by most of the researchers. In this case, heat source parameters from experience are assumed, and transient temperature distribution analysis is repeated by changing the parameters until the obtained region above the melting point matches the target molten shape. Recently, machine learning methods have been become effective to improve inverse analysis in structural integrity issues to straight-forward analysis. In this work, a model using the deep learning has been developed that can directly determine the parameters of the heat source model from the welding records and the molten shape, which can omit the inverse analysis of the heat source parameters, which has been a bottleneck in the past. This deep learning model can reduce the time required determining parameters used in FEA for failure analysis of welded components.

Transient Thermomechanical Stress Analysis of Hot Surface Ignition Device Using Sequentially Coupled Computational Fluid Dynamics–Finite Element Analysis Approach

Abstract Energy addition using a hot surface ignition device is required for reliable ignition of aircraft compression ignition engines running on fuel variations and at altitude conditions. Thus, durability of the hot surface ignition device is crucial for application in these engines. Thermomechanical stress is one of the key parameters that determine durability, which requires an accurate prediction of the transient temperature field based on well-defined boundary conditions representing the dynamic and complex fluid flow inside engines. To meet this requirement, the present study focuses on transient thermomechanical stress analysis using a sequentially coupled computational fluid dynamics (CFD)–finite element analysis (FEA) approach to understand transient thermomechanical responses of the hot surface ignition device. A three-dimensional transient reacting flow simulation was conducted first using converge software, the results of which were exported to map thermal and pressure boundary conditions onto a structural finite element mesh. Transient thermomechanical stress analysis was performed sequentially using abaqus software utilizing the mapped boundary conditions. The results such as transient temperature history, resultant thermomechanical stress, displacement, potential failure modes, etc., were critically reviewed, which can provide helpful information for further design improvement.

Thermal transient stress analysis in RCC dam construction

The major influence on the structure during the building of concrete dams from rolled compacted concrete is temperature. Substantial temperature variations and cracks may arise as a result of heat generated during cement hydration and the effect of several other causes. The 56-meter-height Tannur RCC Dam has been selected for coupled thermal-structural analysis using the ANSYS software. The dam is initially designed for a 3 m lift thickness, resulting in 19 layers. It takes 10 days to finish each layer. During the dam's construction, thermal analysis is carried out at several lifts. Thermal stress analysis of the dam uses the temperature distribution derived from the thermal study as input. As a result, the maximum tensile stress derived from thermal stress analysis is also utilized to obtain the possibility of a dam fracture. The study is expanded to include a dam with lift thicknesses of 3.5 and 4 m, leading to 16 and 14 layers, respectively. Maximum tensile stresses from thermal stress analysis compute the crack index for lift thicknesses of 3, 3.5, and 4 m. The maximum temperatures have been calculated based on estimations of the completed dam's temperature regime. Along with an investigation of potential cracking, a prediction of the structure's thermal stress condition is performed.

Thermal shock analysis of functionally graded sandwich curved beams using a new layerwise theory

AbstractThis work for the first time presents a simple, accurate and straightforward finite element formulation that requires a C0 continuity of transverse displacement for the transient stress analysis of curved beams under thermal shock using a new layerwise theory. The FGM sandwich curved beam is considered to be made of three layers in which the top, middle and the bottom layer is considered to be made of pure ceramic, functionally graded material (FGM) core and pure metal constituents, respectively. The proposed new layerwise theory assumes a higher‐order displacement field for FGM core and first‐order displacement field for both top and bottom layers. The material properties are assumed to be temperature‐dependent. The governing differential equation for the present investigation is formulated using Hamilton's principle. A wide range of comparison studies are presented to establish the accuracy of the present layerwise finite element formulation. A parametric study is conducted to show the simplicity and wider applicability of the proposed formulation. It is shown here that by selecting an appropriate value of volume fraction index, core to facesheet thickness ratio, magnitude of thermal shock, curvature and thickness ratio, the transient thermal stresses induced in FGM sandwich curved beams can be reduced substantially.

Study of the Stress Distribution Due to the Effect of Transient Analysis on a Vertical Pressure Vessel and Validation using the Mesh Independence Study

The importance of Pressure Vessel (PV) to industries is one of the reasons why the design and structural integrity should be fully understood and considered when deploring it in under different conditions. The design of such vessels need to be broadened with a detailed thermal stress due to its time-dependent different behaviours experienced under load. Therefore, this study aimed at investigation of transient analysis of PV when subjected to different operating condition. The PV used for this simulation was designed based on American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) 2019 and subjected to transient-stress analysis (transient thermal and structural) using ANSYS software. A complete evaluation of temperature, heat flux and resulting stress distribution across the vessel was estimated at four different locations within the designed PV and the obtained result was compared with analytically obtained results from appropriate standards. The accuracy of the result obtained from PV was validated using analysis of Mesh Independent Study (MIS), Grid Convergence Index (GCI) and fractional error obtained between the fine grid used. The results showed that there were different temperature and heat flux distribution at the considered locations, these varied distributions or change are according to various transients which are as a result of the load applied to the PV. The simulated maximum principal stress value was close to the analytically computed stress with a percentage error of 2.65% with respect to the analytically obtained result. The analysed maximum stress (W analysed) value 3400 MPa, obtained from MIS study was close to 3210 MPa obtained for maximum stress using numerical approach (WN). The GCI value obtained was 0.073 and fractional error of -0.003 which show that the result presented are grid independent solution.

Transient analysis of layered beams subjected to steady heat supply and mechanical load

In this study, an analytical model is developed for the analysis of transient temperature, displacements, and stresses in simply supported layered beams. The beam is suddenly heated from the top and bottom surfaces by external steady heat sources and is subjected to a mechanical load. The temperature in each layer is variable along the thickness and follows the one-dimensional (1-D) transient heat transfer equation. The Laplace transform approach is used to obtain the transient temperature field in the beam. The thermoelastic constants of the beam are temperature-dependent. Dividing every layer into a series of thin slices, the temperature and the thermoelastic constants for each slice can be considered uniform. The two-dimensional (2-D) thermoelasticity theory is adopted to derive the governing equations of displacements and stresses in each slice. The transfer matrix method is applied to obtain the displacement and stress solutions for the beam. As an example, the distributions of transient temperature, displacements, and stresses in a three-layer beam are studied. The effects of the temperature dependent thermoelastic constants on the mechanical behavior of the beam are discussed in detail.

Transient stress and deformation analysis of a shear deformable FG rotating cylindrical shell made of AL-SIC subjected to thermo-mechanical loading.

ABSTRACT Transient stress and deformation analysis of a functionally graded rotating cylinder made of Al-Sic with short length under thermal and mechanical loads is studied in this paper. It is assumed that the cylinder is located on a friction bed and is subjected to an external torque. The material property is assumed to be variable along the radial direction based on volume fraction distribution. Thermal conductivity equation with time parameter is solved to obtain temperature distribution by Finite Difference Method. First-order shear deformation theory is used to derive kinematic relations. The governing equations are derived using minimum total potential energy and Euler relations. These governing equations are solved using the method of Eigenvalue and Eigenvector. The physical and loading boundary conditions are applied to obtain unknown coefficients. As the main result of this paper, it is concluded that the radial displacement is uniform at the middle of a cylindrical shell and is decreased to zero with an increase of axial coordinate.

MICROSTRUCTURAL AND TRANSIENT THERMAL ANALYSIS OF TIG WELDED JOINT SAE 2205 WITH AISI 304 WITH AISI 308 FILLER METAL

In the present work SAE 2205 is welded with AISI 304 using AISI 308 filler wire. TIG welding current was maintained at 110, 120 and 130 Amp and the voltage was set at 40 Volt. A constant welding speed of 0.5 mm/s was maintained for all the experiments. The optical microscopic examination of the welded samples revealed the presence of recrystalized zone, mushy zone at the weld metal SAE 2205 side and columnar grains adjacent to the heat affected zone. The maximum hardness value of Rc 29 was observed in the welded region. The increase in hardness value was attributed to absorption of oxygen in the weld metal during welding and solidification of the weld metal. A maximum yield strength of 354 MPa and an ultimate tensile strength value of 549 MPa were obtained for the samples processed at 130 Amp. Combined transient thermal and stress analysis was performed for the dissimilar stainless steel joints made between SAE 2206 and AISI 304L. A maximum Von Mises stress of 85 MPa was obtained for the weld joints made between stainless steel AISI 304 and stainless steel SAE 2205.

Vector Sum Analysis Method of Loess Slope Stability under Rising Groundwater Level Conditions

The stability analysis of loess slopes with a rising groundwater level is a problem that integrates unsaturated and transient seepage, stress analysis, and stability prediction. For this purpose, a sequentially coupled method of seepage‐softening‐stability was used. First, seepage analysis of a loess slope with a rising groundwater level was conducted according to unsaturated and transient seepage analysis theory. Second, the spatial distribution of the deformation and strength parameters of the soil, both of which were based on the calculated results of the seepage analysis, were adjusted according to the water‐induced structural deterioration equation. Third, the vector sum analysis method of loess slope stability, which was based on the temporal‐spatial distribution laws of effective unit weight, elastic modulus, Poisson’s ratio, cohesion, internal friction angle, and seepage force, was performed by the body force method. To verify the proposed method, the limit equilibrium method of loess slope stability was conducted by the surface force method. Finally, the progressive failure process of a loess slope with a rising groundwater level on the White Deer Plain was presented as an example. A comparison analysis of the calculated results of the two methods revealed that the proposed method was reasonable and reliable.

Transient stress analysis of sandwich plate and shell panels with functionally graded material core under thermal shock

ABSTRACTA finite element formulation for stress analysis of functionally graded material (FGM) sandwich plates and shell panels under thermal shock is presented in this work. A higher-order layerwise theory in conjunction with Sanders’ approximation for shells is used to develop the finite element formulation for transient stress analysis of FGM sandwich panels. The top and the bottom surfaces of FGM sandwich panels are made of pure ceramic and metal, respectively, and core of the sandwich is assumed to be made of FGM. The temperature profile in the thickness direction of the panels is considered to be varying as per the Fourier’s law of heat conduction equation for unsteady state. The heat conduction equations are solved using the central difference method in conjunction with the Crank–Nicolson approach. Transient thermal displacements of the sandwich panels are obtained using Newmark average acceleration method and the transient thermal stresses are obtained using stress–strain relations, subsequently. Results obtained from the present layerwise finite element formulations are first validated with available solutions in literature. Parametric studies are taken up to study the effects of volume fraction index, temperature dependency of material properties, core thickness, panel configuration, geometric and thermal boundary conditions on transient thermal stresses of FGM sandwich plates and shells.

Topology optimization considering the fatigue constraint of variable amplitude load based on the equivalent static load approach

In this research, a new layout optimization method is developed to consider high cycle fatigue constraints which occur due to variable amplitude mechanical loading. Although fatigue is a very important property in terms of safety when designing mechanical components, it has rarely been considered in topology optimization with the lack of concept and the difficulty of sensitivity analysis for fatigue constraints calculated from multiaxial cycle counting. For the topology optimization for fatigue constraint, we use transient stress analysis to extract effective stress cycles and Miner's cumulative damage rule to calculate total damage at every spatial element. Because the calculation of the exact sensitivities of a transient system is complex and time consuming for the topology optimization application, this research proposes to use the pseudo-sensitivities of fatigue constraints calculated by applying equivalent static load approach. In addition, as an aggregated fatigue constraint is very sensitive to the changes in stress value which causes some unstable convergences in optimization process, a new scaling approach of the aggregated fatigue damage constraint is developed. To validate the usefulness of the developed approaches, we solved some benchmark topology optimization problems and found that the present method provides physically appropriate layouts with stable optimization convergence.

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Thermo-mechanically coupled thermal and stress analysis of interior ballistics problem

This study covers the interior ballistic solution of a 7.62 mm gun barrel based on shooting tests conducted using a test barrel and G3 rifle. The 3-D transient heat transfer and stress (thermal/mechanical) analysis were done using a thermo-mechanically coupled theory. The maximum pressure and muzzle velocity data of the test barrel were obtained via piezo-electric sensors and light screens, respectively. Using these data, Vallier–Heydenreich method was employed to determine the pressure, projectile velocity and position along the barrel. Pressure information was used with Noble–Abel equation to determine the temperature of burnt gases along the barrel. The convection heat transfer coefficient was determined using Vielle's burning equation. The commercial software program ANSYS was employed to get the temperature distribution in radial and axial directions of the barrel. The radial temperature distribution through the barrel wall thickness was validated by the temperature readings taken at the outer barrel surface using a FLIR thermal imager as a new and high precision method compared to the most generally used measuring methods with thermocouples. Pressure and temperature data along the barrel were employed in stress analysis to get the radial, circumferential and axial stresses. The results of the finite element (ANSYS) and analytical solutions were closely conforming to each other.

Random Vibration Analysis for Impellers of Centrifugal Compressors Through the Pseudo-Excitation Method

Impellers of centrifugal compressors are generally loaded by fluctuating aerodynamic pressure in operations. Excessive vibration of the impellers can be induced by unsteady airflows and lead to severe fatigue failures. Traditional transient stress analyses implemented in time domain generally require multiple load-step, very time-consuming computations using input of temporal pneumatic force previously obtained from Computational fluid dynamics (CFD) analyses. For quick evaluation of structural integrity of impellers, it is necessary to develop random vibration models and solution approaches defined in frequency domain. In this paper, the Pseudo-Excitation Method (PEM) is used to obtain power spectral density of three-dimensional, dynamic displacement and stress of impellers. A finite element model of an unshrouded impeller of a centrifugal compressor is generated based on the result of unsteady CFD analysis. Compared with the direct transient stress analyses in time domain, the pseudo-excitation method provides accurate and fast estimation of dynamic response of the impeller, making it an applicable and efficient method for analyzing random vibration of impellers.

Structural Integrity Role in Plant Life Extension - A Case Study

The steam generators at Advanced Gas-Cooled Reactor (AGR) nuclear power stations in the UK are potentially life-limiting components. Enhancing the capability to monitor the steam generators has been identified as having the potential to provide key evidence in justifying the extension of the generating lifetime of the stations. It has been proposed to install new temperature measuring instrumentation to monitor reactor gas temperature and to provide additional data regarding steam generator operating conditions. The modification will be to introduce thermocouples to the bore of an intact steam generator tube to facilitate temperature measurement at or near to the locations of interest. The modified steam generator tube will be sealed at the feed header upstand. Between the upper surface of the superheater header tubeplate and the wall of the superheater header, the thermocouple bundle and sheath will be contained within a rigid stainless steel guide tube. The guide tube will be attached at both ends by welds, each forming a pressure boundary. At the tubeplate a weld will separate the bore of the sealed guide tube from the steam space within the superheater header; a weld between the guide tube and the superheater header will separate the steam space within the superheater header from atmosphere outside the header. In order to obtain a better design, three 3-dimentional finite element models have been created using ABAQUS. A series of cyclic pressure, and start-up and shutdown thermal transient stress analyses have been carried out to provide stress values for structural integrity assessments to be conducted using ASME III, Subsection NH and R5.

Explicit formulae for the internal stress in spherical particles of active material within lithium ion battery cathodes during charging and discharging

Abstract The fundamental process underlying the operation of lithium ion batteries is the diffusion of charge-carrying ions through the electrolyte that separates the anode from the cathode, and the reversible insertion of lithium ions into the host material’s crystal structure (intercalation and de-intercalation). Alongside the principal electrochemical consequences of this process, mechanical phenomena that accompany (de)intercalation are of fundamental significance for deformation and fragmentation of the active materials, since it is these phenomena that ultimately determine the battery structural integrity and durability. This article presents a sequentially coupled analytical treatment of the transient diffusion and stress analysis (eigenstrain) problem related to the lithiation and de-lithiation processes at the level of an individual spherical secondary particle of active material. Explicit closed form approximate solutions are derived for the stresses that arise within the particles during fast charging. They provide a firm basis for the assessment of the charging conditions influence on the internal stress states and the effects on battery damage, mechanical integrity and durability.

English

The disc brake is a device used for slowing or stopping the rotation of the vehicle. Number of times using the brake for vehicle leads to heat generation during braking event, such that disc brake undergoes breakage due to high stress. The transient stress and structural analysis is preferred to choose the low stress material for better performance. Disc brake model is done by CATIA and analysis is done by using ANSYS workbench. The main purpose of this project is to study the analysis of the stress for the Aluminium, Grey Cast Iron, HSS M42, and HSS M2. The stress and structural analysis is performed for four materials and the stress is established in the disc for different materials. A comparison between the four materials for the stress values and material properties obtained from the stress analysis and structural analysis low stress material is preferred. Hence best suitable design, low stress material Aluminium is preferred for the Disc Brakes for better performance.

Finite element modeling and validation of a four-bar linkage prosthetic knee under static and cyclic strength tests

This work presents a procedure to simulate the static and cyclic strength tests implemented to ensure the structural integrity of a four-bar linkage prosthetic knee. The test protocols used in this work follow a standard defined by the International Organization for Standardization (ISO). This standard is titled ‘Prosthetics—Structural Testing of Lower-Limb Prostheses—Requirements and Test Methods’ or shortly called ISO 10328:2006. The purpose of this standard is to guarantee that a prosthesis is able to survive a random severe load and has a sufficient fatigue life. Finite element method, which is a numerical technique used to model a physical system, is employed as a primary computational tool to simulate the prosthesis under the tests. The method of explicit nonlinear transient stress analysis is applied to determine the strength of prosthesis. Consequently, the finite element model reveals the stress distributions induced on the prosthesis and predicts its fatigue life. Besides, to examine the accuracy of the model, the simulation results, particularly structural strains, are validated with those obtained from experiments. In each testing condition, five repetitions are performed to ensure the result consistency. The validation results confirm the fidelity of the proposed finite element model. The average of absolute percentage errors between the simulation and experimental results in all testing scenarios is estimated to be 22%.

Material requirements of the high performance light water reactor

This paper summarizes results of various stress and deformation analyses which were performed for the design concept of the High Performance Light Water Reactor. These are in particular predictions of fuel cladding temperatures, deformations and stresses, assuming that fuel rods are wrapped with a wire as grid spacer enhancing coolant mixing. Moreover, the fuel assembly box with its honeycomb sandwich panels, which were optimized for minimum neutron absorption, has been analyzed with respect to temperatures, deformations and stresses, as well as the mixing plenums above and underneath the reactor core. Finally, transient stress analyses and radiation exposure will be shown exemplarily for the thick walled pressure vessel. The results shall give material research programmes a better understanding of required material properties for supercritical water cooled reactors.

Nonlinear transient stress and wave propagation analyses of the FGM thick cylinders, employing a unified generalized thermoelasticity theory

In the present paper, nonlinear generalized (with second sound effects) and classical thermoelasticity analyses are performed for functionally graded thick cylinders with temperature-dependent material properties subjected to various thermomechanical shocks at their inner and outer surfaces, employing Hermitian elements. The unified generalized thermoelasticity approach is composed of three distinct theories and employed to study the thermoelastic wave propagation and reflection phenomena. In contrast to the available rare researches proposed so far based on the generalized theories, the continuity condition of the stress components at the mutual boundaries of the elements and the temperature-dependency of the material properties are taken into account. Furthermore, Mori–Tanaka homogenization model of variations of the material properties is employed instead of the simple rule of mixture. Transfinite element approach is employed to determine the transient responses. Besides, the formulation considers effects of both mechanical and thermal shocks. Influences of the lags between the thermal and elastic waves are among the interesting observations of the present paper.