Thermo-structural Analysis Research Articles

Thermo-structural Comparative Analysis of Internal Combustion Engine Piston by Finite Element Methods

Thermo-structural Comparative Analysis of Internal Combustion Engine Piston by Finite Element Methods

Prediction of automotive body-in-white distortion in paint baking process

Thermal-induced distortion prediction of thin shell structures is a challenging task. It often involves highly nonlinear buckling behaviour, where the critical buckling temperature and post-buckling deformations are very sensitive not only to structural stiffness and boundary conditions but also minute geometric imperfections (a.k.a., “surface quality”) of the incoming parts. In the present work, novel Computer Aided Engineering (CAE) methods were developed to predict the thermal-induced distortion of automotive Body-in-White (BIW) panels during paint shop oven-baking processes. The CAE methodology consist of a set of three Finite Element Analysis (FEA) procedures, i.e., thermal-buckling mode analysis, thermo-structural analysis, and imperfection analysis. Two vehicle level case studies showed that simulations successfully predicted the thermal-induced distortion for panels such as the Body Side Outer (BSO) header. It was concluded that the distortion depends primarily on the temperature difference between the BSO and the rest of the BIW during the oven-baking process, rather than the temperatures themselves. Body panel forming quality (e.g., residual stresses and thickness thinning) and assembly dimensional quality were also found to impact the distortions.

Thermo-structural analysis of a dump nozzle for conducting hot liquid sodium

Liquid sodium is found to be an essential element in nuclear reactors for transferring enormous amount of heat between source and sink. Conducting hot liquid sodium through metal pipes is witnessed to be challenging owing to the huge thermomechanical stress involved during the process. The present research work aims at designing a dump nozzle for the safe transfer of hot liquid sodium (at 923 K) to a storage tank through SS316LN pipe. Numerically simulated results showed the development of huge thermal stress at the weld junction formed between pipes and storage tank, which is primarily due to the sudden increase in temperature. The newly proposed dump nozzle with reducer/baffle (connecting pipe with storage tank) is witnessed in reducing the sudden increase in temperature and henceforth, minimized the stress intensity of the weldment by 70 %. The fatigue-creep interaction diagrams are plotted for the weld and the reducer; the results showed that the induced stress values for the parts are well below the safety envelops for the given boundary conditions of liquid sodium flow velocity and temperature. The proposed dump nozzle design is hence validated for the safe handling of transferring liquid sodium to storage tank.

Optimization and validation of a finite element methodology for thermo-structural analysis of polyhuretane wheels for roller coaster application

Polymeric materials are widely used in several engineering sectors. Among these, a particularly critical sector for this type of material is that of roller coasters. The wheels are indeed made with an aluminum hub and a compact polyurethane coating, which, being in contact with the track, is subject to high speeds dynamic loads. Due to the viscoelastic behavior typical of these materials, such loads induce overheating of the coating and therefore a rapid degradation of the wheel. This results in machine downtime and, consequently, significant waste of time and money. In this context, the authors have developed a methodology for finite element thermo-structural analysis capable of quickly evaluating the temperature reached during work cycles and proving very useful in selecting the type of wheels to use. In this work, this methodology was firstly computationally developed and then validated by comparing the analysis results with data obtained from experimental tests conducted by the manifacturer. The comparison demonstrated the effectiveness of the proposed method, highlighting, however, a constant error in terms of maximum temperature reached attributable to a non-exact material characterization.

Thermoelastic analysis of disk with FEM for FGM variable parameters

Functionally graded materials (FGMs) using the finite element method (FEM) with C 0 elements, focusing on the examination of material variable parameters. The research advances the understanding of FGMs through a thermo-structural analysis of an FGM disk, assessing its response under thermal and mechanical loads. Thermal and thermo-mechanica analysis demonstrates the precision of the proposed approach in delineating the complex behavior of FGMs under diverse conditions. The research contributes to enrich the comprehension of FGM behavior using simple FEM models.

Thermo-structural analysis and design for multi-functional membrane roofs of airport terminals

The utilization of large-span membrane structures in airport terminals has attracted considerable attention due to their excellent building aesthetics, reasonable structural behavior and multi-functional applications. Integrating structure and function is useful to improve thermal performance of such buildings. This study focuses on a scaled two-layer membrane roof in accordance with a newly-built aerogel-membrane airport roof and investigates the dynamic building thermal performance. The two-layer membrane roof is composed of an outer membrane layer as structural element, an air gap for ventilation and an inner membrane layer integrating aerogel mats. The effects of aerogel thickness, ventilation velocity and gap height are analyzed with multi-physics numerical tools. The structural behavior of the aerogel-membrane roof structure is examined in agreement with the building standards. The comparison between numerical and experimental results on solar irradiance is performed to demonstrate the reliability of numerical results under the typical environmental conditions. The thickness of the aerogel layer and the ventilation velocity are shown to have a significant effect while the air-gap height plays a minor role. A maximum temperature reduction of 4.7 °C demonstrates that using the proposed approach can improve building thermal performance. Moreover, temperature curves with small fluctuations indicate an efficient control of the indoor temperature. Therefore, the thermo-structural analysis method of the multi-functional membrane roofs can guarantee structural safety and facilitate building thermal performance control.

Thermostructural analysis on airfoil fin printed circuit heat exchanger using supercritical CO2

Thermostructural analysis on airfoil fin printed circuit heat exchanger using supercritical CO2

Comparative study of thermo-structural analysis of nano-fluid flow in a baffle-corrugation rectangular channel for adoptable sustainable multifunctional application

Recent years have seen a rise in interest in and usage of thermo-hydraulic research of nano-fluid flow phenomena in a variety of engineering applications. Under uniform heat flux, thermo-physical characteristics of nano-fluid flow in baffle-corrugation rectangular channels have been observed from a numerical standpoint for various Reynolds numbers and different values of the aspect ratio of baffles. Employing the finite volume method, the governing equations have been solved and to visualize the simulation results, fluent software has been employed. Four various types of baffle-corrugation shapes (plane, trapezoidal, isosceles, and triangular) with their interchanged positions have been examined in the present analysis. Different types of base fluids viz., water, glycerin, and ethylene glycol, four distinct forms of nanoparticles, Al2O3, CuO, SiO2, and ZnO are assumed to be transmitted for varying values of volume fractions (D%) and diameter of nanoparticles. From the present study, it is found that in the presence of plane baffle-isosceles corrugation provides the highest average Nusselt number ([Formula: see text]) than the rest of the baffles. It is revealed that SiO2 nano-fluid provides the highest [Formula: see text] in comparison to other nano-fluids. Further, it is concluded that [Formula: see text] enhances with the enhancement of D%, Reynolds number (Re), height, and pitch of the baffles and is found to decrease as the diameter of nanoparticles increases. This study also indicates that glycerin-SiO2 provides the highest [Formula: see text] than the rest of the base fluids.

Highly efficient conversion of plastic waste into fuel via thermal cracking: Thermo-structural analysis of the pyrolysis reactor and characterization of the final product

This study aimed to convert plastic waste into Low-Density Polyethylene (LDPE) through pyrolytic fuel, using a discontinuous reactor at the laboratory scale. To achieve this, a thermomechanical analysis was conducted using ANSYS software to assess thermal stresses and deformations, testing the material resistance of the pyrolysis unit against temperature variations. Thermal degradation occurred within a temperature range of 350–550 °C. Pyrolysis conditions were adjusted to maximize the production of liquid pyrolytic oil, achieving a yield of 70.2 % at a temperature of 450 °C and a heating speed of 10 °C/min maintained for a duration of 150 min. FT-IR analysis of the pyrolytic oil identified the presence of aliphatic compounds, confirmed by gas chromatography (GC), revealing a complex composition including alkanes, cycloalkanes, and aromatic compounds. These results highlight the similarity of pyrolytic oil to traditional fuels such as gasoline and diesel.

Production and thermo-structural analysis of a hybridized natural fibre-based ceiling board for building applications

Canewood and palm kernel fibre (PKF) have successfully been used as filler material for producing ceiling boards, with recycled low-density polyethylene (LDPE) as the binder. This work covered three aspects which are the optimization of process and production parameters, chemical, and thermal analysis of the utilized filler material. The production parameters considered are the percentage composition of both the binder and filler material while the process parameters studied are the press temperature, pressure and time. These parameters were optimized over both physical and thermal properties of the developed ceiling board which are thermal resistivity, water absorption and thickness swell. Thermal results for both the cane wood and PKF proved to be thermally stable up to temperatures as high as 325 and 310°C, respectively. The optimized ceiling board showed a thermal resistivity, water absorption and thickness swell of 16.192 W/M.K, 4.669 and 6.594% respectively, for a production and process parameters of 15% cane wood, 10% PKF, 75% LDPE, 6 min press time, 7 bar pressure and 198°C press temperature. The produced ceiling board showed a specific heat capacity, thermal energy and heat flux of 769.23 Jkg−1K−1, 60 W and 23.07 kWm−1 respectively. The findings imply that the LDPE filler materials are appropriate for use in ceiling board applications.

Coupled Thermo-Structural analysis of absorber tube for direct steam generation in parabolic trough solar collector

The absorber tube is a key component of a parabolic trough solar collector, and the bending of the absorber has an important role in receiver failures. The detailed survey of existing commercial solar power plants reveals that 55 % of failures happened due to the rupture of glass envelope and 29 % due to the loss in annulus vacuum. In this study, coupled thermal–hydraulic and structural stability analyses have been performed to understand the thermo-structural performance of absorber tubes under realistic operating conditions of direct steam generation processes. The fluid flow and heat transfer equations have been solved using the FVM scheme, and structural equations have been solved using the FEM scheme. The impacts of absorber material selection have been studied using steel absorbers and copper-steel bimetallic absorbers. The study has been performed for operating pressure of 60 bar and 100 bar, mass flow rates of 0.4 kg/s and 0.6 kg/s, and DNI of 750 W/m2. The temperature gradient, deflection, strain, and stress in the absorber wall have been analyzed. It has been observed that the temperature gradient in the absorber could be reduced by 51 % and deflection by 40 % using a copper-steel bimetallic absorber instead of the steel absorber. The maximum thermal strain observed under the subjected boundary condition in the steel absorber is 6.27 mm/m, and in the bimetallic absorber is 6.06 mm/m. Further, the maximum equivalent stress of 31.1 MPa in the steel absorber and 39.8 MPa in the bimetallic absorber has been observed. The present work is useful for understanding the absorber's thermo-structural functionality in the preheating, evaporation, and superheating stages of direct steam generation in solar collectors.

Thermo-Structural Response Prediction of UHTCC Control Surface for Hypersonic Cruise Vehicle

One of the most complex issues that govern the design of a hypersonic vehicle is aerodynamic heating which is much more severe for an air-breathing vehicle as it operates within the atmosphere for longer durations. Due to the detrimental impact of aerodynamic heating on the vehicle structure, it is imperative to develop a robust thermal protection system that can protect the vehicle from high temperatures. However, the development of sophisticated TPS for slender components is impractical and, therefore, requires a hot structure system that can operate at substantial aerothermal loads. The aim of this study is to predict the impact of aero-heating on a UHTCC-based hot structure system of a hypersonic cruise vehicle through uncoupled thermo-structural analysis of the control surface. Validation of numerical methods implemented is done through literature comparison and grid independency tests.

Thermo Structural Integrity of a Closure Assembly for The Base Region of a Re-Entry Module

Base heating is an important phenomenon in the design of re-entry capsules. The nature of reverse flow in the base region is largely decided by the conditions prevailing at the end of the fore body. For configuration like the re-entry module, the reverse flow is found to be supersonic near the base. It is therefore necessary to protect the base region as well as the internal components from base heating.
 Suitable Thermal Protection System (TPS) of minimum mass that will protect the base thermally is to be designed for the base heating levels during re-entry. Low density ablative is selected as the TPS material.
 The base region of the re-entry module consists of a closure assembly made up of structural elements which are thermally protected. The structural elements and TPS have different thermo-physical properties. It is necessary to qualify the closure assembly for re-entry loads. However, qualification of closure assembly is a challenging job as there is no facility in the world which can simulate all the time varying flight parameters simultaneously. Hence to study the integrity of the closure assembly during re-entry, detailed temperature mapping of closure assembly was carried out.
 Thermal mapping of the closure assembly was carried out considering both axisymmetric and three-dimensional model using finite element package and the results are compared. Maximum temperatures attained at different locations of the assembly are discussed. Temperature distribution of the closure assembly at critical instants of flight was estimated. Thermo-structural analysis carried out showed the adequacy of the design, which was subsequently demonstrated by a successful re-entry flight.

Effect of Flexible Operation on Residual Life of High-Temperature Components of Power Plants

Electricity generation from renewable energy sources is emerging as a result of global carbon emission reduction policies. However, most renewable energy sources are non-dispatchable and cannot be adjusted to meet the fluctuating electricity demands of society. A flexible operation process has been proposed as an effective solution to compensate for the unstable nature of renewable energy sources. Thermal load fluctuations during flexible operation may cause creep–fatigue damage to the high-temperature components of thermal power plants, as they are designed with a focus on creep damage under a constant power level. This study investigated the residual life of high-temperature components, such as a superheater tube and a reheater header, to failure under flexible operation conditions using finite element analysis and empirical models. First, we determined an analytical solution for the straightened superheater tube under thermal conditions and compared it with the numerical solution to verify the numerical models. Through the verified finite element model, the creep–fatigue life of the reheater header was estimated by considering flexible operation factors and employing the Coffin–Manson and Larson–Miller models. Although fatigue damage increases with decreasing minimum load and ramp rate, we confirmed that creep damage significantly affects the residual life during flexible operation. In addition, a surrogate model was proposed to evaluate the residual life of the reheater as a function of the flexible operation factors using the machine learning methodology, based on the results of finite element methods. It can be used to predict its residual life without performing complex thermo-structural analysis and relying on empirical models for fatigue and creep life. We expect our findings to contribute to the efficient operation of thermal power plants by optimizing the flexible operation factors.

Evaluation of the TRF of reinforced concrete beams through thermal and thermostructural analysis

PurposeIn the analysis of structures in a fire situation by simplified and analytical methods, one assumption is that the fire resistance time is greater than or equal to the required fire resistance time. Among the methodologies involving the fire resistance time, the most used is the tabular method, which associates fire resistance time values to structural elements based on minimum dimensions of the cross section. The tabular method is widely accepted by the technical-scientific community due to the fact that it is safe and practical. However, its main criticism is that it results in lower fire resistance times than advanced thermal and thermostructural analysis methods. The objective of this study was to evaluate the fire resistance time of reinforced concrete beams and compare it with the required fire resistance time recommended by the tabular method of NBR 15200 (ABNT, 2012).Design/methodology/approachThe fire resistance time and required fire resistance time of reinforced concrete beams were evaluated using, respectively, numerical models developed based on the finite element method and the tabular method of NBR 15200 (ABNT, 2012). The influence of the following parameters was investigated: longitudinal reinforcement cover, characteristic compressive strength of concrete, beam height, longitudinal reinforcement area and arrangement of steel bars.FindingsAmong the evaluated parameters, the covering of the longitudinal reinforcement proved to be more relevant for the fire resistance time, justifying that the tabular method of NBR 15200 (ABNT, 2012) being strongly and directly influenced by this parameter. In turn, more resistant concretes, higher beams and higher steel grades have lower fire resistance time values. This is because beams in these conditions have greater resistance capacity at room temperature and, consequently, are subject to external stresses of greater magnitude. In some cases, the fire resistance time was even lower than the required fire resistance time prescribed by NBR 15200 (ABNT, 2012). Both the fire resistance time and the required fire resistance time were not influenced by the arrangement of the longitudinal reinforcements.Originality/valueThe present paper innovates by demonstrating the influence of other important design variables on the required fire resistance time of the NBR 15200 (ABNT, 2012). Among several conclusions, it was found that the load level to which the structural elements are subjected considerably affects their fire resistance time. For this reason, it was recommended that the methods for calculating the required fire resistance time consider the load level. In addition, the article quantifies the security degree of the tabular method and exposes some situations for which the tabular method proved to be unsafe. Moreover, in all the models analyzed, the relationship between the span and the vertical deflection associated with the failure of the beams in a fire situation was determined. With this, a span over average deflection relationship was presented in which beams in fire situations fail.

Strength and tightness evaluation method for pipe flange connections considering thermal effects

The pipe flange connection is widely applied in chemical, power plants, petrochemical, offshore oil and gas industries, and its strength and tightness are significant for the safe operation. However, there are still no practical and applicable strength and tightness evaluation methods for pipe flange connections working in dramatically varying temperatures. This paper proposed an approach to evaluate the pipeline's strength and sealing performance considering thermal effects in actual operating conditions by combining the experimental measurement and thermostructural analysis. The critical thermodynamic parameters are identified through measured temperature data in operating conditions, and then these parameters are used in the thermostructural analysis to obtain the actual temperature and stress fields. Then, the strength and tightness in complex temperature cases can be evaluated accurately. The pipe flange connection of a liquefied natural gas (LNG) fueling station is analyzed to verify the presented method's effectiveness. This method applies to evaluating the pipeline's strength and tightness and can predict the pipeline's performances under extreme temperatures using the tested data within the measurement range and the corresponding thermostructural analysis. Furthermore, the work in this paper also provides a reference for the design and analysis of pipe flange connections working in complex temperature conditions.

Finite Element Analysis of Damage of Cylindrical Roller Bearing of Main Shaft of Shot Blasting Machine

The main shaft of shot blasting machine mainly uses cylindrical roller bearing as the supporting part. The influence of stress, strain and temperature on bearing damage was studied by thermal structural coupling analysis of the bearing through finite element simulation. The causes and main damage forms of bearing surface were verified by super depth of field observation and finite element analysis. It is found that there exists pyramidal strain in the contact area between inner and outer raceway and roller, and its distribution form is continuous point distribution. The stress concentration is mainly distributed in the contact area between the roller face and the retaining edge, and the roller temperature is more concentrated in the area near the end face. The maximum length and depth of spalling pit on racetrack surface were 572.2μm and 14.15μm respectively. The maximum width and depth of the scratches on the roller surface are 386.7μm and 10.7μm, and the damage degree of the roller surface is not uniform. The thermo-structural coupling analysis is used to simulate the running state of bearings, which is of guiding significance to analyze the failure forms of bearings and improve the service life of bearings.

Design and development of LN2 cooled cryopump for application in high heat flux test facility

• A liquid nitrogen cooled sorption cryopump is developed for the High Heat Flux Test Facility at IPR. • Design details, fabrication details, operational concept and thermo-structural analysis results are described. • The pump geometrical concept is novel because it provides ease of assembly, integration and trouble free operation in horizontal and vertical direction mounting. • The pump has 250 mm opening and offers pumping speed of ∼5106.6 l/s for water vapour and ∼1197 l/s for nitrogen using liquid nitrogen as coolant. • The pump integration and operation with High Heat Flux Test Facility is discussed. High Heat Flux Test Facility (HHFTF) at Institute for Plasma Research is established for testing thermal performance of Plasma Facing Components (PFC) and Plasma Facing Materials (PFM) that are expected to withstand steady-state and transient heat flux of the order of 10 MW/m 2 and 20 MW/m 2 , respectively, expected in plasma fusion devices. During high heat flux testing of PFCs and PFMs, water vapour and other trapped gases are released. For the pumping need, a cryocooler based commercial cryopump and a turbo-pump is used. In addition to that, an indigenously developed liquid nitrogen cooled cryopump is mounted to the High Heat Flux (HHF) test facility. The developed cryopump has 250CF inlet flange and mounted vertically downward to an angle port (50°) to the D-shaped vacuum chamber of the HHF facility. The pump has integrated liquid nitrogen bath to provide stable cooling to the cryopanels and radiation shield. Cryopanels are made of copper and coated with micro-porous activated charcoal. The pump's geometrical concept is novel because it provides ease of assembly, integration and trouble free operation in horizontal and vertical direction mounting. The pump offers pumping speed of ∼5106.6 l/s for water vapour and ∼1197 l/s for nitrogen using liquid nitrogen as coolant. The pump geometry, thermal and structural analysis, fabrication and experimental details are discussed in this paper. After integrating the cryopump to the HHF test facility, performance studies were carried out and initial test results are also discussed.

Nonlinear Thermo-Structural Analysis of Lightweight Concrete and Steel Decking Composite Slabs under Fire Conditions: Numerical and Experimental Comparison

Composite slabs with steel decking profiles are widely used in building construction. However, the literature on the fire resistance of lightweight concrete (LWC) composite slabs with steel decking is limited. In this work, the thermo-structural performance of LWC composite slabs with trapezoidal steel decking was studied under fire conditions. A total of 12 experimental fire tests were carried out using specimens of 160 mm thickness, 1120 mm width and 2030 mm length, in which nine composite slabs were made of LWC and the remaining three slabs were made of normal concrete (NC) to serve as a benchmark for comparison. All the samples were tested in a furnace following EN 13381-5, applying the standardized time–temperature curve and constant load. During the experimental tests, phenomena such as the vaporization of the free water inside LWC, debonding between steel decking and concrete and changes in material properties affected the thermo-structural performance of composite slabs. The test results show that the load-bearing capacity of lighter slabs does not assure the minimum structural behavior of R30. However, the lighter the concrete is, the lower the thermal transmittance, improving the slabs’ thermal performance under fire conditions. Advanced nonlinear numerical models were developed to predict the thermal and structural performance of the studied LWC composite slabs in terms of temperature and time-displacement. The influences of key factors such as vaporization, thermal strains and debonding were included using material properties and a thermal contact conductance interlayer. Finally, the nonlinear models and the experimental results were compared. The difference between the experimental and numerical values was less than 15%, showing that the numerical results were in good agreement with the experimental results. The results of this study also compared the performance of LWC composite slabs with the NC composite slabs, giving rise to interesting conclusions from a practical point of view.

Thermostructural Numerical Analysis of the Thrust Chamber of a Liquid Propellant Rocket Engine.

The numerical simulation of rocket engine thrust chambers is very challenging as several damaging phenomena, such as plasticity, low-cycle-fatigue (LCF) and creep occur during its service life. The possibility of simulating the thermostructural behavior of the engine, by means of non-linear finite element analyses, allows the engineers to guarantee the structural safety of the structure. This document reports the numerical simulations developed with the aim of predicting the thermostructural behaviour and the service life of the thrust chamber of a liquid-propellant rocket engine. The work represents a step ahead of previous researches by the authors, with particular reference to the addition of the Smith-Watson-Topper (SWT) fatigue criterion, and to the implementation of a sub-modelling technique, for a more accurate assessment of the most critical section of the component. It was found that the equivalent plastic strains in the most critical nodes obtained through the sub-modelling technique were about 20% lower than those calculated without sub-modelling. Consistently with experimental tests from literature conducted on similar geometries, the most critical areas resulted to be on the internal surface of the chamber. The analyses demonstrated that the LCF damaging contribution was significant, with a life prediction for the thrust chamber of about 3400 cycles.