Thermal Response Of Structure Research Articles

Thermal–structural response and life prediction of lattice regenerative cooling thrust chambers in liquid rocket engines based on a simplified viscoplastic model

With advances in aerospace technology, the reusability of liquid rocket engines has become the focus of considerable research interest. Traditional channel-type regenerative cooling thrust chambers often experience plastic deformation and microcracks, which limit their lifespan. This study proposed a novel lattice regenerative cooling thrust chamber using a simplified viscoplastic model and ABAQUS finite element software to simulate thermal–structural responses under different pressure conditions. The lattice structure not only enhanced the cooling efficiency and reduced the structural weight but also mitigated the plastic deformation and high-temperature creep of the inner wall. At an inner-wall temperature of 820 K, creep damage was significant. Compared to that of traditional chambers, the lattice structure of the proposed chamber exhibited different mechanical behavior and failure modes, with a more uniform stress distribution and initial failure occurring at the lattice nodes. The proposed design avoided the “doghouse” effect evident in traditional chambers, achieving an inner-wall lifespan of up to 202 cycles, a 359 % improvement. The high design flexibility of the lattice structure in the cooling channels enabled enhanced thrust chamber longevity. The study results provide new insights and technical support for next-generation liquid rocket engine designs.

Structural characterization of a suspension bridge by mapping the temperature effects on strain response based on neural network models

AbstractMapping the structural responses based on main loads to characterize signature of complex structures with high-dimensional features is a determinant factor for structural health monitoring (SHM). Current technological advances contribute to the optimization of data analysis, aiming to make the process less demanding in terms of time and computational demand. Machine learning (ML) models became popular due to their capacity to estimate structural behaviour based on the measurements gathered by the SHM systems. This work proposes a methodology supported by Neural Networks (NN) for the characterization and prediction of the structural behaviour based on thermal loads and structural responses. By comparing the observed values and predicted outcomes from the NN, it is possible to identify measuring errors, new trends or pattern variations that need further assessment. A sensitivity analysis is also proposed to confirm the model robustness and to characterize the influence of the temperature on the structural responses. The case study is the 25 de Abril’s bridge, located in Lisbon, Portugal.

Development and Experimental Validation of a Heat Transfer Model for Spilled Molten Salt Pools

A spill of radionuclide-bearing molten salt is one of the major postulated events that needs to be analyzed for liquid fluorine salt–cooled high-temperature reactor (FHR) or molten salt reactor licensing purposes. In this postulated event, radioactive source term materials (RSTMs) in the molten salt are discharged from the reactor vessel to the reactor building. The release of RSTMs from the spilled salt pool to the gas space in the reactor building is expected to be controlled by the cooling behavior of the spilled salt, including the growth and shrinkage of the solid crust on the surface of the spilled salt pool. This paper presents a simulation model for spilled salt pool heat transfer and validation efforts. The validation data come from two molten salt spill tests that were performed recently: the PELE2 test by the Rapid Experimental Laboratory of Kairos Power LLC (KP) and the Argonne salt cooling test conducted by Argonne National Laboratory. The former was a large-scale test involving kilograms of molten spilled FLiNaK salt, and the latter was a relatively smaller-scale test targeting various processes associated with a salt spill event. Both tests generated valuable data sets that can be used to assess salt cooling and validate evaluation models. This paper provides a new one-dimensional model that can simulate the cooling process of a spilled salt pool as well as the thermal responses of heat structures, such as the stainless steel liner and the concrete below the salt. The model has been implemented as part of KP-SAM code, which is a branch of the systems code SAM specific to KP FHR. The simulation results of the model are compared with the data of the PELE2 and Argonne tests, and reasonable agreements are observed between the model and test data.

Superior thermal response of additive manufactured porous stainless steel with carbon nanotubes

The temperature rise in the battery cells during continuous operation leads to a thermal runaway that affects the life and performance of electric vehicles. For such reasons, heat sinks with high thermal conductivity will be of utmost importance in maintaining optimal operating temperatures. This paper presents the development of a 3D-printed SS 316L porous structure with carbon nanotubes coated on it through a chemical vapour deposition method to enhance thermal management. The carbon nanotubes (CNTs)-coated porous Stainless Steel (SS) structure showed enhanced thermal performance. It absorbed heat 7 % faster than the non-coated and dissipated heat 138 % more at a heat input of 36.5 W. For the fixed 120-second time, a temperature difference existed of 3.9 °C during heating and up to 4.4 °C during cooling. These results demonstrate that the CNT coating dramatically improves the thermal response of the porous SS structure. This original approach for integrating CNT coatings with 3D-printed porous SS structures opens up a potential avenue for the efficient design and manufacturing of a heat sink, thus increasing the reliability and durability of the battery systems in electric vehicles.

Temperature-based damage detection for the commissioning dataset of the MX3D Bridge

Environmental and operational variations (EOV) remain a major obstacle for the successful transfer of structural health monitoring (SHM) techniques from laboratory experiments, such as cracked beam experiments, to full-scale structures, such as long-span bridges. With evidence that timely interventions significantly increase the service-life and reduce the overall life-cycle cost of ageing infrastructure, carrying out SHM in the presence of EOV, such as temperature, is therefore of high priority within the civil engineering community. The temperature-based measurement-interpretation (TB-MI) approach was developed to monitor the thermal response of an instrumented structure and detect changes linked to damage by minimising the impact that temperature variations have on anomaly detection techniques. The iterative regression-based thermal response prediction (IRBTRP) methodology is utilised in the TB-MI approach, and is trained on the healthy condition of the bridge to predict its undamaged response to temperature fluctuations. Thermal response predictions are compared to the measured response and deviations between them are indicative of a variation in the thermal response, due to structural change such as damage. Small deviations can then be identified using anomaly detection techniques, which results in earlier damage detection than if thermal response predictions had not been used. The TB-MI approach and the IRBTRP methodology have been applied to detect damage on the MX3D Bridge, the world’s first structure produced through metal additive manufacturing (i.e. 3D printing). This study demonstrates that the use of the TB-MI approach enables earlier and more widespread damage detection amongst multiple sensor groups, compared to when no temperature effects are considered. The adoption of the TB-MI approach can therefore greatly increase the reliability of and our reliance on SHM techniques for critical infrastructure.

Microscale Thermal–Structural Modeling for Carbon Fibers Subjected to a Hypersonic Boundary Layer

With regard to the thermal protection system, the thermal–structural responses of modern ablative materials are of primary importance in many aspects, including material selection and sizing. Due to the intricate nature of their porous structure and complicated thermal conditions they are subjected to, ablative materials may exhibit unexpected behavior, which can potentially lead to material failure. In this study, two solvers—a direct simulation Monte Carlo solver and a finite-volume-based material response solver—are coupled together to predict the microscale thermal–structural performance of a thermal protection system material like phenolic impregnated carbon ablator. In this approach, individual fibers are modeled at the microscale, which provides valuable knowledge of porous media behavior. Nonuniform boundary conditions, including the heat flux and external force, are captured by the direct simulation Monte Carlo solver, and the detailed thermal and structural performance of the fiber is captured by the material response solver. The results show that individual fibers do not fail based on the temperature gradient and applied aerodynamic forces. However, it is shown that the attachment points of the fibers are the most vulnerable. This vulnerability can potentially lead to a breakdown of the binders, which would separate fibers and cause material failure.

Research on the mechanism of thermal-mechanical coupling effects of hypersonic aircraft rudder structure

Hypersonic aircraft have achieved rapid development in the past decade, with flight speeds exceeding 5 Ma, posing a very severe aerodynamic and thermal environment for rudder structure. Especially for metal rudder wings, the extremely high temperature and temperature gradient makes the structural thermal response problem very prominent and complex. This article focuses on the study of the thermo-mechanical coupling response of the metal rudder wings of hypersonic aircraft in flight thermal environments. By simplifying the aerodynamic load and aerodynamic thermal environment under flight time sequence, a finite element model based on thermo-mechanical sequence coupling is established. The temperature, thermal stress, and deformation response curves of key parts are extracted, and the thermo-mechanical coupling response law of the rudder structure is explored. Based on the mechanical properties of structural materials at different temperatures, the corresponding relationship between stress and residual strength of key parts during flight time is obtained, and the safety factor of key parts of the structure is given.

Active Green Constructions and Their Impact on Gray Infrastructure

Addressing climate change necessitates a conscious transition toward sustainable infrastructure solutions. Our vision involved transforming an experimental area into the University Experimental Center. This experimental building serves as a model for gray infrastructure implementation, taking into account its dimensions, layout, flooring, and material composition. Our study aims to compare the retention capacities of various types of vegetated roofs, as determined by different legislations. The findings indicate that the outcomes vary based on the regulations used. This variation subsequently influences the design of associated infrastructures, such as rainwater drainage systems, and the design of stressed structures. This is due to the impact of water quantity on the thermal response of a stressed structure. The water used to irrigate the vegetation layer, along with the water retained by the upper roof, has a positive impact on both the building and its surroundings. Initially, the system comprised two functional components: vegetated roofs and a reference roof. The integrated experimental roof shell, in conjunction with the frame, forms an autonomous system. This system serves as a segment for quantifying water retention, humidity, and temperature across diverse green infrastructure substrates. We analyzed the thermal response of experimental roof constructions and monitored the influence of water and precipitation. Our results indicate that the height of the substrate affects not only the retention capacity but also the thermal response of the vegetated roof.

Computer Aided Environment Design Technology Based on Simulation Data

Computer aided environment design technology, also known as Computer aided environment (CAE) technology, is a technology that utilizes computers for engineering design, analysis, and optimization. Simulation data refers to the data generated by simulating the real environment or system in a computer, with its core characteristics of simulation and predictability, used for performance evaluation. CAE technology simulates the state and behavior of buildings, facilities, or environments, evaluating the effectiveness of design solutions and predicting performance through simulation data. This article aims to conduct a technical analysis and practical case studies to evaluate the effectiveness, draw conclusions and suggestions from the technical analysis, in order to promote the development of computer-aided environmental design technology and improve the efficiency and quality of environmental design. Therefore, this article uses CAE technology to simulate the thermal performance, structural response, and fluid dynamics changes of buildings. This article simulates the temperature environment of rooms in buildings and the pedestrian density and traffic flow in traffic through experimental simulation and data comparison. It is found that the peak pedestrian density occurs at 16 and 17 minutes, and the lowest value is at 45 minutes. There is a certain similarity between the data results and the real data.

EUROPEAN GROUND MOTION SERVICE FOR BRIDGE MONITORING: TEMPORAL AND THERMAL DEFORMATION CROSS-CHECK USING COSMO-SKYMED INSAR

Abstract. This paper elaborates on the potential of the deformation time-series provided by European Ground Motion Service (EGMS) data points for bridge monitoring, in terms of the response of bridge structures to temporal and thermal deformations. For this purpose, high-resolution Cosmo-SkyMed (CSK) Synthetic Aperture Radar (SAR) images have been utilized through Persistent Scatterer SAR Interferometry (PS-InSAR) to derive spatially detailed deformation time-series of two bridges located at the north of Lombardy region, Italy. Then, the Annual Displacement Velocity and Thermal Expansion Coefficient of the data points in both datasets are extracted based on the corresponding deformation time-series. The response parameters are post-processed through projection and compensation steps to become comparable. Cross-checking the results by comparing the response parameters along the bridges showed that the global (for L3 products) and local (for L2b products) differential behaviour and the variation of the values of these parameters from one side to the other side of each bridge are consistent between CSK and EGMS datasets. However, the EGMS L3 information shows a slightly lower magnitude in both displacement velocity and thermal expansion coefficient responses. According to the revealed capability of EGMS information in this work, it can be concluded that the EGMS data points, if spatially cover a bridge, can present a reasonable and sufficient insight into the temporal evolution of displacement and thermal structural response, suitable for structural health monitoring and condition assessment of bridges under operational and environmental loads.

Fire Resistance Characteristics of Firewall Structure Associated with Impact Damage Induced by Explosion

When a fire accident accompanied by an explosion occurs, the surrounding firewalls are affected by impact and thermal loads. Damaged firewalls due to accidental loads may not fully perform their essential function. Therefore, this paper proposes an advanced methodology for evaluating the fire resistance performance of firewalls damaged by explosions. The fragments were assumed to be scattered, and fire occurred as a vehicle exploded in a large compartment of a roll-on/roll-off (RO-RO) vessel. The impact velocity of the fragments was calculated based on the TNT equivalent mass corresponding to the explosion pressure. Damage and thermal-structural response analyses of the firewall were performed using Ansys LS-DYNA code. The fire resistance reduction was analyzed in terms of the temperature difference between fire-exposed and unexposed surfaces, temperature increase rate, and reference temperature arrival time. The degree of damage and the fire resistance performance of the firewalls varied significantly depending on impact loads. When naval ships and RO-RO vessels that carry various explosive substances are designed, it is reasonable to predict that the fire resistance performance will be degraded according to the explosion characteristics of the cargo.

Weather-dependent passive thermography and thermal simulation of in-service wind turbine blades

To cope with the increase in the manufacturing and operation of wind turbines, wind farm operators need inspection tools that are able to provide reliable information while keeping the downtime low. Current inspection techniques require the wind turbine to be stopped. This work presents the current progress in the project EvalTherm, in which passive thermography is evaluated as a possible non-destructive inspection tool for operational wind turbine blades (WTBs). A methodology to obtain thermal images of rotating WTBs has been established in this project. However, the quality of the results is heavily dependent on various aspects such as weather conditions, information on the inspected WTB, damage history, etc. In this work, a section of a used WTB is simulated using finite-element modelling (FEM) as well as experimentally tested for evaluating the accuracy of the model. Such a model will provide insight into the potential thermal response of a certain structure (with specific material properties) in given weather (boundary) conditions. The model is able to provide satisfactory predictions of the temporal thermal response of the structure, as well as indicate what thermal contrast(s) transients result from artificial defects introduced in the structure.

Simulation of RC Beams during Fire Events Using a Nonlinear Numerical Fully Coupled Thermal-Stress Analysis

The collapse and deterioration of infrastructures due to fire events are documented annually. These fire incidents result in multiple deaths and property loss. In this paper, a reliable and practical numerical methodology was introduced to facilitate the whole process of fire simulations and increase the practicality of performing comprehensive parametric studies in the future. These parametric studies are crucial for understanding the factors that affect thermal–structural responses and avoiding the high cost of destructive tests. The proposed algorithm comprises a fully nonlinear coupled thermal-stress analysis involving thermal and structural material nonlinearity and the thermal–structural response during a fire. A detailed numerical modeling analysis was performed with ABAQUS to achieve the proposed algorithm. The results of the proposed numerical methodology were validated against published experimental work. The experimental work includes a full-scale RC beam loaded with working loads and standard heating conditions to simulate real-life scenarios. The tested beam failed during the fire, and its fire resistance was recorded. The results demonstrated a good correlation with the experimental results in thermal and structural responses. Moreover, this paper presents the direct coupling technique (DCT) and the advantages of using DCT over the traditional sequential coupling technique (SCT).

Review on Detection of Internal Defects in CFRP Strengthened Steel Structures Using Eddy Current Pulsed Thermography

Abstract: This study investigates the effectiveness of the current pulse thermal technique (ESRT) in detecting internal defects in СFRР reinforced metal structures. This study covers various internal defects of FRР reinforced steel structures, including cracks, small tracks in СFRР, metal cracks / inter-steel cracks. We theoretically analyze the effect of these problems on the magnetic and thermal response of structures. To confirm the results of the theater, statistical and diagnostic tests were performed on steel plates reinforced with СFRР with various defects. Numerical and diagnostic results show that EСРТ can estimate observed deformations and show low temperature regions in EСРТ thermograms. In addition to the thermal characteristics of the thermograms, the appearance of the temperature profile and changes in temperature are also examined for reanalysis of the thermal analysis. In addition, based on the test results, the effectiveness of EСRT to restore the size and scope of errors was demonstrated. Overall, theoretical, numerical and experimental results show that EСRT is effective in diagnosing internal defects in CFRP-reinforced steel structures

Soil-structure interaction of integral abutments

Integral abutment bridges (IABs) are pioneering structures that offer certain advantages over conventional bridges. The main difference is the ability of IABs to eliminate the necessity of utilizing bearings and expansion joints. This results in more economical construction and enhanced structural performance. However, the intricate soil-structure interactions of IABs under the influence of seasonal changes are not yet fully understood. This paper aims to improve the understanding of these innovative structures by utilizing comprehensive numerical models to investigate their geostructural performance under various conditions. The case study selected for this research was the Middlesex bridge in Vermont, USA. A full-scale monitoring program at this bridge measured and recorded the bridge acting pressures, deformations, and internal forces, making it possible to gain insight into the thermal response of such structures. For the numerical research, a comprehensive two-dimensional numerical model, developed by using the PLAXIS software, was verified against the available field measurements. Subsequently, parametric studies were conducted to investigate earth pressure and pile bending moment variations influenced by different model conditions. Key model parameters were varied, including the constitutive soil model, thermal loading, backfill stiffness, pile size and orientation, and span length. It was found that utilizing a linear constitutive soil model could lead to significant inaccuracies in the results. Increasing the backfill stiffness was seen to increase passive earth pressures and decrease pile bending moments. With smaller pile sections, oriented for weak-axis bending, pile bending moments decreased substantially and lateral earth pressures increased. Because dead load magnitudes were closely linked to span lengths, pile bending moments and backfill pressures increased when fewer and longer bridge spans were used.

Improvement of Temperature Performance of Singlemode-Multimode-Singlemode Fiber Structure.

A theoretical model for studying the temperature properties of singlemode-multimode-singlemode (SMS) fiber structure fabricated by absorptive multimode fiber (MMF) cladding is established. Moreover, an SMS-based temperature sensor is fabricated and experimentally demonstrated. Experimental results show that the dip wavelength of the transmission spectrum changes linearly with temperature, which is in good agreement with the simulated results obtained by using the model. Further, a comprehensive study of temperature characteristics affected by the thermo-optic effect, thermal expansion effect, and thermal effect of absorption characteristics is performed for SMS fiber optic structures with different refractive indexes, thermo-optic coefficients, and absorption properties of MMF cladding, MMF core diameters, and thermal expansion coefficients of packaging shell. According to the obtained rules, investigations are carried out into the thermal response of an SMS fiber structure resulting from combined thermal effects for temperature performance optimization. Excellent temperature stability with a temperature sensitivity of 0 pm/°C or good temperature sensitivity of -441.58 pm/°C is achieved accordingly.

Joule heated hot wall models in hypersonic wind tunnel facilities for energy deposition studies

Joule heating is a useful experimental technique for ground based hypersonic testing as it allows replication of the governing wall-to-freestream temperature ratio and thus better simulation of the aerothermodynamic environment of high-speed flight vehicles. This paper presents design considerations for using this hot-wall method for hypersonic wind tunnel models. A numerical analysis of material choice and thickness for creating rapid uniform high-temperature model conditions is presented. The influence of the method and location of energisation and structural requirements for the integration of joule heating in a hypersonic wind tunnel model is also examined numerically. Experimental results of a bench-top study incorporating the design elements for joule heating for studies analogues to thermal energy deposition are also presented. To replicate thermal energy deposition, graphite plates with a 1.0 or 2.5mm thickness were heated via joule heating to a base level of either 30W or 100W. After 120s of heating the plates were then exposed to a thermal pulse of either 550, 1200 or 1300W. The thermal-structural response of the plate was experimentally recorded with a measurement system incorporating infrared thermal cameras, single and two-colour pyrometers, a load cell and a 520 nm light Digital Image Correlation system suitable for use on hot wall models. Results from this bench-top study demonstrate a proof-of-concept for using joule heating for analogue thermal deposition studies. Temperature rises of ΔT on the order of 500 - 1000K were achieved on models with base temperatures of 450 - 600K achieved with this technique. Plate deflections as high as 3.2 - 4.1mm were recorded for 1.0mm plates with both stress and strain of the heated models resolved experimentally for base heating and pulsed energy conditions.

Heat up impact on thermal stresses in SOFC for mobile APU applications: Thermo-structural analysis

Because of its high efficiency, fuel flexibility, and high-quality waste heat for cogeneration requirements, the solid oxide fuel cell (SOFC) is a potential fuel cell type for power generation in a variety of applications. High working temperatures provide these benefits, but they also come with drawbacks, such as restrictions on the operating environment, problems with thermal management, long on/off times, and the issue of selecting appropriate materials to assure compatibility of the physical material properties of the fuel cell stack components. However, the elevated process temperatures of the SOFC system result in technical challenges. The heat-up stage is a critical issue for the SOFC stack, since the transient process conditions lead to thermal gradients which are combined with material gradients. The result is a mismatch in the thermal–mechanical material behavior inducing high thermal stresses, which in turn affect the functionality of the fuel cell stack. In the SOFC stack under consideration, a glass ceramic joint is used to ensure reliable sealing between cells. This region is identified to be at risk, due to high thermal stresses. In this study the computational modeling approach is applied to predict the thermal-structural response of the stack components to different heat-up strategies and investigate the system with respect to fuel cell temperature, thermal gradients, and induced stresses. Computational thermal and structural results for time dependent heat-up speeds are presented and compared. Essentially, running the process with a constant speed would not provide an optimized solution. Instead, the obtained results show that the heat-up speed should be adjusted to achieve the desired state of fuel cell temperature, reduced thermal gradients and stresses. This target can be met by applying mathematical modeling approach, since experimental analysis are time and cost consuming.

Evaluation of the Heat Transfer Performance of Stearic Acid PCM/ Porous Aluminium Thermal Composite Structures for Heat Storage Applications

Phase change material (PCM) thermal composites consisting of porous aluminium/stearic acid phase change material have been produced for heat storage applications. Porous aluminium/stearic acid composite structures were produced by infiltrating stearic acid PCM into open- cell porous aluminium materials prepared by using dissolvable spherical salt beads in combination with vacuum casting process. Scanning electron microscopic analysis has been used to characterize the empty porous aluminium materials and the results reveal a cellular structure consisting of spherical pores which are interconnected with smaller windows. The thermal response of empty porous aluminium structures and those infiltrated with stearic acid was measured using an infrared camera. The result showed that the heat transfer performance of the PCM thermal composites was significantly improved and largely dependent on the relative density of the porous structures.

Estimation of delamination thickness in a multi-layered thermally thin structure by step heating thermography

The performance of a multi-layered structure is dependent upon its structural integrity. The main challenge posed to the structural integrity of such structures is the vulnerability of the interface to the formation of defects (like delamination, crack, void). Hence it becomes compelling to study such structures and propose methodologies that could detect and characterize the defects. This paper presents an approach to estimate the delamination thickness formed at the interface of a two-layered structure (a simple case of a multi-layered structure). An analytical expression of delamination thickness is derived using the electrical analogy approach. The saturation value of absolute thermal contrast, which is a characteristic feature of the thermal response of material or structure with defect under step heating has been used to derive the analytical expression of delamination thickness. The proposed approach is fast, simple, noncontact and devoid of extensive data handling. Simulations and experiments have been done to verify the approach. This approach can provide guidance during the design phase of multi-layered structures and aid in defining their failure threshold depending on the application. Additionally, it can also be implemented in manufacturing units during quality checks or can also be used for in situ defect characterization.