Local Thermal Stress Research Articles

Comparison with the effect of the cyclic liquid nitrogen jet and liquid nitrogen immersion cooling on the deterioration of mechanical properties of high temperature rocks

In order to study the effect of liquid nitrogen jet cooling on the deterioration of mechanical properties of high temperature rocks, the cyclic liquid nitrogen jet (LNJ) cooling and liquid nitrogen immersion (LNI) cooling were carried out on 200 °C and 400 °C granite. The variations of ultrasonic velocity, tensile strength, acoustic emission and energy evolution were analyzed. The results showed that with the increase of rock temperature and cooling cycles, the deterioration of mechanical properties of high temperature rock was enhanced by cyclic LNJ and LNI cooling. Differently, the deterioration effect of LNI cooling on mechanical properties was weakened with the increase of cycles. On the contrary, the deterioration effect caused by LNJ cooling was significantly enhanced with the increase of cycles. For example, when the LNI cooling cycles exceeded 5 times for 200 °C sample and 3 times for 400 °C sample, the tensile strength and absorbed energy at failure decreased limitedly with the growth of cooling cycles. However, the deterioration degree of rock mechanical properties at 400 °C showed a linear decline trend with the increase of LNJ cooling cycles. The temperature and the number of cycles had significant effects on mechanical properties, with temperature having the greatest influence. The difference between LNJ and LNI cooling became more pronounced with increasing cycles. LNJ cooling, by creating localized high thermal stresses and non-uniform heat transfer, led to continuous deterioration of mechanical properties with each cycle. In contrast, LNI cooling's effect saturated after initial cycles. The multi-cycle LNJ cooling method could improve the fracture degree of high temperature rock under low load level, so as to improve the efficiency of high temperature hard rock formation drilling.

Unraveling the plastic deformation, recrystallization, and oxidation behavior of Waspaloy during thermal fatigue crack propagation

Thermal fatigue is one typical failure mode for engine components involving cyclic thermal stresses/strains. However, the microstructure evolution and its microscopic interaction with thermal fatigue cracking in Ni-based superalloys featuring intragranular γ′ and intergranular carbides have yet to be clarified. In this study, cyclic temperature variations ranging from 25 °C to 700 °C were conducted on Waspaloy to unravel the synergistic damage mechanisms including stress distribution, plastic deformation, recrystallization, oxidation, and crack propagation. The thermal fatigue cracks are found to predominantly propagate along grain boundaries with a gradually descending rate from 3.5 μm/cycle to 1.5 μm/cycle. Compared with the macroscopic thermal stress up to ∼800 MPa, the local thermal stress induced by different sizes of M23C6 carbides marginally affects the crack propagation. Intensive slip bands and sparse deformation twins in the deformed matrix are observed, indicating the plastic deformation is mainly achieved by dislocation slipping and supplemented by twinning. Trans-granular cracks parallel to {111} planes form occasionally when the propagation directions of intergranular cracks are almost parallel to the {111} slip bands. Besides, dislocations promote the oxidation damage of the crack surface through pipe diffusion of solutes, and the γ′-precipitate free zones (PFZs) and recrystallized areas are produced accordingly. The quantitation analysis of the PFZ thickness provides a reference for predicting crack initiation time during thermal fatigue.

In-situ thermal Raman mapping and stress analysis of CNT/CF/epoxy interfaces

A study of the interfacial behavior and internal thermal stress distribution in fiber-reinforced composites is essential to assess their performance and reliability. CNT/carbon fiber (CF) hybrid fibers were constructed using electrophoretic deposition. The interfacial properties of CF/epoxy and CNT/CF/epoxy composites were statistically investigated and compared using in-situ thermal Raman mapping by dispersing CNTs as a Raman sensing medium (CNTR) in a resin. The associated local thermal stress changes can be simulated by capturing the G‘ band position distribution of CNTR in the epoxy at different temperatures. It was found that the G‘ band shifted to lower positions with increasing temperature, reaching a maximum difference of 2.43 cm−1 at 100 °C. The interfacial bonding between CNT/CF and the matrix and the stress distribution and changes during heat treatment (20–100 °C) were investigated in detail. This work is important for studying thermal stress in fiber-reinforced composites by in-situ thermal Raman mapping technology.

A novel compact supercritical CO2 solar receiver based on impinging jet: Heat transfer performance and thermal stress analysis

The compact solar receiver can withstand high temperature and high pressure, which provides promising solutions for direct supercritical CO2 (S-CO2) solar receiver applications. However, it still suffers from local high temperature and large thermal stress due to the non-uniform heating boundary condition. The impinging jet method can significantly enhance the local heat transfer coefficient, holding significant potential in reducing the local high temperature of the compact S-CO2 receiver. Inspired by this, a novel design for a compact S-CO2 receiver using the impinging jet was proposed in this work. The heat transfer performance and stress behavior of the jet channel within the receiver were numerically investigated. The results showed that the jet channel has a significantly higher heat transfer performance than the rectangular channel, and the shorter flow path of the jet channel also effectively reduces the pressure loss. Meanwhile, the jet pattern significantly enhances the temperature uniformity, thereby reducing the thermal stress. In addition, increasing the channel aspect ratio improves the thermo-hydraulic performance, but increase the stress at the same time. The increase in the number of jet holes and the jet hole diameters not only enhance the thermo-hydraulic performance, but also reduce the stress of the jet channel.

Near-infrared spectroscopy to quantify overall thermal process intensity during high-moisture extrusion of soy protein concentrate

High-moisture extrusion (HME) is widely used to produce meat analogues. During HME the plant-based materials experience thermal and mechanical stresses. It is complicated to separate their effects on the final products because these effects are interrelated. In this study we hypothesize that the intensity of the thermal treatment can explain a large part of the physicochemical changes that occur during extrusion. For this reason, near–infrared (NIR) spectroscopy was used as a novel method to quantify the thermal process intensity during HME. High–temperature shear cell (HTSC) processing was used to create a partial least squares (PLS) regression curve for processing temperature under controlled processing conditions (root mean standard error of cross-validation (RMSECV) = 4.00 °C, coefficient of determination of cross-validation (R2CV) = 0.97). This PLS regression model was then applied to HME extrudates produced at different screw speeds (200–1200 rpm) and barrel temperatures (100–160 °C) with two different screw profiles to calculate the equivalent shear cell temperature as a measure for thermal process intensity. This equivalent shear cell temperature reflects the effects of changes in local temperature conditions, residence time and thermal stresses. Furthermore, it can be related to the degree of texturization of the extrudates. This information can be used to gain new insights into the effect of various process parameters during HME on the thermal process intensity and extrudate quality.

Nanostructure characterisation of welded polyethylene using small angle X-ray scattering

Polyethylene (PE), a common thermoplastic polymer, is gaining prominence in the construction and packaging industries due to its exceptional mechanical properties, chemical resistance, safety, and integrity. However, internal defects can occur during manufacturing and throughout its service life. Neglecting this problem results in the disposal of plastic and, consequently, the accumulation of plastic waste and environmental issues, which have caused much criticism. A common method to repair the thermoplastics is welding, which introduces seams and localized thermal residual stress fields resulting in areas where damage can nucleate, potentially leading to cracks and failure over time. These cracks often start at the nanoscale and propagate to larger length scales until failure occurs. The objective of this research paper is to develop welding processes, with improved integrity and lifespan for PE. Additionally, it aims to investigate and assess the impact of PE welding on parent materials at nano- and micron-scales, to understand limitations that are challenging to overcome in such welding processes. The study involves joining PE panels together under various pre-heating and post-cooling conditions, followed by evaluating the environmental stress cracking resistance of the welds and the durability of the repaired components. The crystallinity and morphology of the PE material in the weld area and its surrounding regions were analysed using Small Angle X-ray Scattering (SAXS), and the findings were compared with results obtained from optical microscopy and Differential Scanning Calorimetry. The study concludes that SAXS results offer exceptional information about the parent PE and weld material within the welding zone.

Thermal-mechanical coupling analysis of the ribbed channels in regenerative cooling

Regenerative cooling plays a critical role in the thermal management for scramjet combustors, and the design of cooling channels is of utmost importance. To comprehensively analyze the performance of cooling channels, a validated thermal-mechanical coupling model was utilized in this study. The thermal and mechanical performance of both smooth and ribbed channels in regenerative cooling was investigated using Finite Volume Method and Finite Element Method. The findings indicate that the ribbed wall has a notable effect on enhancing the overall thermal performance of the channel. Moreover, the presence of ribs weakens the influence of buoyancy in the flow field, which can be one of the contributing factors in inhibiting heat transfer deterioration. Additionally, the design of ribs significantly reduces the average thermal stress experienced by the channel. However, it should be noted that the non-uniform heat transfer in the axial direction leads to a significant increase in local thermal stress. The triangular ribbed channel proves to be an effective approach in reducing thermal stress. Compared to rectangular ribbed ribs, the utilization of triangular ribs can result in a reduction of thermal stress by up to 30%. This observation highlights the advantage of triangular ribs in enhancing system life and safety by minimizing thermal stress.

Experimental Study of Deformation Risk and Interpolation Analysis of Temperature for Water Walls under Flexible Low-Load Conditions

With the development of renewable energy in power generation, a large number of thermal power plants operate under flexible working conditions. To study water wall deformation risk under flexible low-load conditions, a lab-scale opposed firing boiler was built to measure and analyze the temperature and thermal stress of the water wall under low-load flexible operating conditions with several nontypical burner arrangements. The results showed that flame radiation and flue gas convection heat transfer induced a high-temperature zone. Thermal stress was mainly caused by thermal expansion of the metal and expansion or extrusion deformation of other areas. Also, local thermal stress fluctuations and excessive values appeared under variable conditions. In addition, the burners’ symmetrical arrangement in the center effectively reduced thermal stress fluctuations and overall thermal stress under flexible working conditions. Finally, based on the limited temperature measurement points in this experiment, the optimal power parameter α for the inverse distance weighted (IDW) method and the shape parameter ε for the radial basis function (RBF) method were found to make a reasonable interpolation prediction of the temperature distribution of the water wall. This study highlights the recommended burner arrangements under flexible low-load conditions and the optimal parameters of the IDW and the RBF methods for estimating temperature in guiding safe operation of the water wall.

Surface construction and optical performance analysis of compound parabolic concentrator with concentrating surface separated from absorber

For the S-CPC (Standard Compound Parabolic Concentrator, S-CPC) based on plane structure, the concentrating surface is connected to the absorber, and the temperature of the concentrating surface and the absorber is significant different during working. The local concentrated thermal stress can easily cause thermal deformation of the concentrating surface. The conventional solution is to form a gap between the concentrating surface and the absorber, which can effectively interdict the thermal stress. However, this would cause the light leakage from the gap, resulting the reduction of the optical efficiency of S-CPC. Therefore, the SCSA-CPC (Separation of Concentrator Surface and Absorber CPC, SCSA-CPC) without gap loss is studied in present research. The mathematical model of SCSA-CPC without gap loss is constructed by using non-imaging optical theory, the concentrating performance and working characteristics of SCSA-CPC are verified through experiments. The research also shows that the optical efficiency of SCSA-CPC is better than S-CPC, and the energy flux distribution on the absorber surface is more uniform. When the annual radiation collection amount of S-CPC is 2008.02 MJ/m2, the value of SCSA-CPC is 2009.00 MJ/m2. SCSA-CPC not only achieves the separation of the concentrating surface and absorber, but also slightly improves the collection capacity of solar radiation.

Numerical investigation on the thermal load heterogeneity of multi-assembly helical coil steam generator in high temperature gas-cooled reactor

The thermal load heterogeneity will lead to inhomogeneous local heat flux and thermal stress, extremely detrimental to the operational stability of heat exchangers with multi-assembly structure. In this paper, a full-scale analysis method for the helical coil steam generator in industry was developed and implemented. The validation was performed against flow boiling heat transfer experiment of helical tube. The simulation of single assembly and full-scale helical coil steam generator in high temperature gas-cooled reactor was performed, and the distributions of thermal-hydraulic parameters in heat exchange region were obtained. The results show that the nonuniform helium flow distribution with the inhomogeneous factor Dm value of 34.83% has a significant influence on the heat transfer characteristics. The peak heat transfer power of central assembly increases by 33.76% against design condition, introducing large thermal load heterogeneity with the inhomogeneous factor Dp value of 30.45%, even threating the structural integrity of helical tube in long-term operation circumstances. The structural elements design in the superior compartment should be optimized to increase the helium mass flow rate of the assemblies below the nozzle and behind the helium baffle, improving flow distribution uniformity and reducing the peak value of local heat flux and thermal stress.

Energy load of metal brake frictions elements

Problem. The mathematical description of the temperature field of the rim of the brake pulley can have both an independent value and be the goal of solving a problem (for example, when calculating the time of heating or forced cooling), and also be used as an auxiliary result for solving another, more complex problem (for example, calculating thermoelastic stresses in brake pulley rim). Goal. The purpose of the work is to assess the energy load of metal friction brake elements during the braking process. Methodology. Solving the tasks involved taking into account the fact that the surface-volume temperatures of the polished working surface of the pulley rim are local when assessing the energy load of the belt pulley rim; surface-volume temperatures are always higher than the "pure" volume temperatures of the pulley rim; polished and matte surfaces of the pulley rim are considered. Results. It is proposed that a new approach to the calculation of local thermal stresses, which is implemented for the first time in the theory of friction and wear. The reliability of the obtained results was confirmed experimentally. Originality. The need to find the non-stationary field in the investigated single- ("pad-pulley") and in multi-pair ("tape-pad" and "pad-pulley") friction nodes is proposed. In the last friction nodes, the friction pads act as insulation between the tape, which is freed from the pads, and the working surface of the brake pulley rim. Practical value. The proposed approach made it possible to establish that the magnitude of stresses on the surface of heat release is almost 5 times greater than in the volume of the pulley rim. At the same time, the nature of the influence of the intensity of heat exchange on the magnitude of stresses is the same as during heating, which leads to a decrease in the formation of cracks on the surface of the pulley rim.

Influence of fiber hollowness on the local thermo-electro-elastic field in a thermoelectric composite

The fiber geometry is one of the important parameters in the effective conversion performance and local strength of thermoelectric composites. In this study, the plane problem of a hollow fiber embedded within a non-linear thermoelectric medium in the presence of a uniform remote in-plane electric current and a uniform remote energy flux is investigated based on the complex variable method. Closed-form expressions for all the potential functions characterizing the thermoelectric field and the associated thermal stress field in both the matrix and fiber are obtained by solving the corresponding boundary value problem. Numerical examples are presented to illustrate the effect of hollowness ratio of the fiber on the local energy conversion efficiency and interfacial thermal stress concentration. It is found that a higher conversion efficiency and a lower amount of thermal stress concentration around a hollow fiber than that around a solid fiber could be achieved simultaneously by appropriate selection of the hollowness ratio of the fiber. The results can be directly used for performance optimization and reliability evaluation in design of thermoelectric composites in engineering.

Cascaded SiC JFET Topology for High-Voltage Solid-State Circuit Breaker Applications

With evolving landscape of direct current (DC) power transmission and distribution, a reliable and fast protection against faults is critical. High performance DC solid-state circuit breakers (SSCBs) can be designed using silicon carbide (SiC) junction field-effect transistors (JFETs), which utilize the device's intrinsic normally-ON characteristic and low ON-resistance. However, for SSCB that require high-voltage (HV) blocking capability, a proper number of JFETs need to be connected in series to achieve the desired voltage blocking rating. It has been conventional to add a controlling normally-OFF transistor, such a metal-oxide-semiconductor field-effect transistor (MOSFET), resulting in a circuit with normally-OFF behavior. However, disparities both in the voltage rating and in the ON-resistance between MOSFETs and JFETs tend to complicate the circuit design, and physically, they may lead to serious localized thermal stresses. A significant challenge remains with ensuring equal voltage balancing across the JFETs during the switching transitions as well as the blocking stage as it is crucial to prevent permanent damages from over-voltage stresses. Therefore, this article presents a new switch topology, in which a cascaded JFET configuration is operated without using a control MOSFET or other added control device. The dynamic voltage balancing network to synchronize both the JFETs' turn ON and OFF intervals is described analytically. Moreover, a novel static voltage balancing network is proposed to establish equal sharing of the total blocking voltage across the series connection of JFETs while maintaining low power loss.

Thermally Induced Microcracks in Granite and Their Effect on the Macroscale Mechanical Behavior

AbstractUnderstanding the thermal effects on rock is critical for the exploration of geothermal resources and the temperature‐driven evolution of Earth. The macroscale mechanical behavior of granite under thermal loading can be complicated due to microcracking and the heterogeneity of minerals. In this study, the thermally induced microcrack propagation of granite was first observed in real time by an ultrahigh‐temperature instrument on an optical microscope. The previous investigation believed that the α–β quartz transition at approximately 573°C leads to a sharp decrease in macroscale mechanical behavior. However, the present experimental results revealed that microcracks initiate at 300°C and coalesce between 400 and 600°C, which is the main reason for the sharp decrease in macroscale mechanical properties of granite. Additionally, an accurate grain‐based model based on the mineralogical morphology of granite samples adopted mechanical parameters of minerals obtained from microscale rock mechanical techniques. It is able to well reproduce the process of microcracking and the strength evolution of granite during heating. The numerical results show that the heterogeneity of thermal expansion and mechanical properties of minerals produce local thermal stress concentrations in granite. The uneven tensile‐compressive stress between feldspar and quartz and the shear stress around biotite result in the initiation and propagation of microcracks. The present work is potentially useful for understanding and predicting the mechanical behavior of granites under thermal loading with different mineral compositions and microstructures.

A novel flow field design with flow re-distribution for advanced thermal management in Solid oxide fuel cell

Solid oxide fuel cell (SOFC) is an alternative for future energy conversion systems with great potential. Long-term operation in SOFC mainly obstructs its further development. Stratification and fission can be occurred in Positive electrolyte negative (PEN) structure by severe thermal stress. By improving the temperature uniformity, localized hot spots and thermal stresses can be eliminated significantly. This study proposed a novel rotary l-type main flow field for SOFC and the thermal and flow characteristics are investigated. The temperature distribution (TD) is estimated by the temperature uniformity index. The results show that the temperature uniformity index increased at least by 40%. The largest TG of the rotary l-type flow field is 20% lower than that of co-flow and cross-flow arrangements. The average TG is 32.72% lower than the counter-flow arrangement. This flow field design provides an effective solution for the long-term operation of SOFC.

Connectivity patterns of Brazilian coral reefs associated with potential variation on thermal stress tolerance

The rising trend in sea surface temperature presents a threat to tropical coral reefs, causing increased mass bleaching and mortality events. Brazilian reefs have been characterized as less susceptible to thermal stress, where the assessment of bleaching events based on temperature anomalies often overpredicts its actual occurrences in comparison with other regions of the global ocean. With coral reefs acclimatized to local environmental conditions, larval connectivity presents a potential role in introducing organisms adapted to different temperature conditions. In the present study, we evaluated the connectivity patterns of Brazilian coral reefs, verifying its potential influence on the variation of thermal stress tolerance supported by these communities. Connectivity was estimated based on 27-year larval dispersion simulations, from 1993 to 2019, among 180 reef sites distributed in seven ecoregions on the Brazilian continental margin. Simulations were performed using a biophysical model coupling ocean currents data and life history traits of Mussismilia hispida, a widespread stony-coral type species and one of the major endemic reef builders in the South Atlantic. The potential influence of larval connectivity on thermal stress tolerance was evaluated considering the probability of connections between each reef site, their respective bleaching thresholds, and the accumulation of sea surface temperature anomalies over 12-week periods. The results indicated that connectivity-influenced bleaching estimations were significantly closer to observations reported in the literature when compared to estimations without connectivity (p-value < 0.05). These findings present an evidence that larval connectivity may display a relevant role in the adaptation of Brazilian corals to changes in seawater temperature, leading to a potential variation of ± 0.3°C in local thermal stress thresholds. Different connectivity patterns assessed during the occurrence of El Niño–Southern Oscillation events were also observed in association with the migrations of the South Equatorial Current bifurcation. These conditions led to the disruption of connections between the Eastern and Northeastern reef sites during El Niño, and between the Northeastern and Amazon reef sites during La Niña. Ultimately, it is expected that those findings may contribute to the management of Brazilian coral reefs regarding changes in dispersal pathways and thermal stress tolerance given future climate change scenarios.

Bioengineered Carboxymethylcellulose-Peptide Hybrid Nanozyme Cascade for Targeted Intracellular Biocatalytic-Magnetothermal Therapy of Brain Cancer Cells.

Glioblastoma remains the most lethal form of brain cancer, where hybrid nanomaterials biofunctionalized with polysaccharide peptides offer disruptive strategies relying on passive/active targeting and multimodal therapy for killing cancer cells. Thus, in this research, we report for the first time the rational design and synthesis of novel hybrid colloidal nanostructures composed of gold nanoparticles stabilized by trisodium citrate (AuNP@TSC) as the oxidase-like nanozyme, coupled with cobalt-doped superparamagnetic iron oxide nanoparticles stabilized by carboxymethylcellulose ligands (Co-MION@CMC) as the peroxidase-like nanozyme. They formed inorganic–inorganic dual-nanozyme systems functionalized by a carboxymethylcellulose biopolymer organic shell, which can trigger a biocatalytic cascade reaction in the cancer tumor microenvironment for the combination of magnetothermal–chemodynamic therapy. These nanoassemblies were produced through a green aqueous process under mild conditions and chemically biofunctionalized with integrin-targeting peptide (iRDG), creating bioengineered nanocarriers. The results demonstrated that the oxidase-like nanozyme (AuNP) was produced with a crystalline face-centered cubic nanostructure, spherical morphology (diameter = 16 ± 3 nm), zeta potential (ZP) of −50 ± 5 mV, and hydrodynamic diameter (DH) of 15 ± 1 nm. The peroxide-like nanostructure (POD, Co-MION@CMC) contained an inorganic crystalline core of magnetite and had a uniform spherical shape (2R = 7 ± 1 nm) which, summed to the contribution of the CMC shell, rendered a hydrodynamic diameter of 45 ± 4 nm and a negative surface charge (ZP = −41 ± 5 mV). Upon coupling both nanozymes, water-dispersible colloidal supramolecular vesicle-like organic–inorganic nanostructures were produced (AuNP//Co-MION@CMC, ZP = −45 ± 4 mV and DH = 28 ± 3 nm). They confirmed dual-nanozyme cascade biocatalytic activity targeted by polymer–peptide conjugates (AuNP//Co-MION@CMC_iRGD, ZP = −29 ± 3 mV and DH = 60 ± 4 nm) to kill brain cancer cells (i.e., bioenergy “starvation” by glucose deprivation and oxidative stress through reactive oxygen species generation), which was boosted by the magneto-hyperthermotherapy effect when submitted to the alternating magnetic field (i.e., induced local thermal stress by “nanoheaters”). This groundwork offers a wide avenue of opportunities to develop innovative theranostic nanoplatforms with multiple integrated functionalities for fighting cancer and reducing the harsh side effects of conventional chemotherapy.

The marsquake catalogue from InSight, sols 0–1011

The InSight mission (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) has been collecting high-quality seismic data from Mars since February 2019, shortly after its landing. The Marsquake Service (MQS) is the team responsible for the prompt review of all seismic data recorded by the InSight's seismometer (SEIS), marsquake event detection, and curating seismicity catalogues. Until sol 1011 (end of September 2021), MQS have identified 951 marsquakes that we interpret to occur at regional and teleseismic distances, and 1062 very short duration events that are most likely generated by local thermal stresses nearby the SEIS package. Here, we summarize the seismic data collected until sol 1011, version 9 of the InSight seismicity catalogue. We focus on the significant seismicity that occurred after sol 478, the end date of version 3, the last catalogue described in a dedicated paper. In this new period, almost a full Martian year of new data has been collected, allowing us to observe seasonal variations in seismicity that are largely driven by strong changes in atmospheric noise that couples into the seismic signal. Further, the largest, closest and most distant events have been identified, and the number of fully located events has increased from 3 to 7. In addition to the new seismicity, we document improvements in the catalogue that include the adoption of InSight-calibrated Martian models and magnitude scales, the inclusion of additional seismic body-wave phases, and first focal mechanism solutions for three of the regional marsquakes at distances ∼30°.

Modelling negative thermomechanical effects in reinforced road structures with thermoelastic incompatibility of coating and reinforcement materials

The phenomena of the formation of local defects and cracks in asphalt concrete pavements of roads and bridges are most often observed in climatic zones with large temperature differences during their seasonal and daily changes. To a large extent, this is due to the heterogeneity of the thermomechanical properties of the materials of the coating layers and the base. To prevent these phenomena, reinforcing rods and meshes are introduced into the coating structure. In this work, using the theory of thermoelasticity, it is shown by the method of mathematical modelling that in cases of incompatibility of the thermomechanical characteristics of asphalt concrete materials and reinforcement, additional localized thermal stresses arise in its small vicinity, which, even at moderate temperatures, can reach critical values and lead to local defects and cracks. Since these defects are latent, they cannot always be detected in practice. The presented results of analytic calculation validated these conclusions. They can be used in both road building and composite design.

Simulation and analysis of sintering stress and warpage displacement in anode supported planar solid oxide fuel cells

During the sintering process of solid oxide fuel cells (SOFCs), the mismatch in the thermophysical properties of materials can lead to excessive local thermal stress and warpage. By establishing a 3D multiphysics model, the stress distribution and displacement during sintering are studied. The results show that when the anode and electrolyte thicknesses are 0.2 mm and 0.02 mm, respectively, the maximum sintering stress is 38.8 MPa, which is 48% lower than the maximum value of all simulation results. In this study, when the anode thickness is 0.7 mm and the electrolyte thickness is 0.008 mm, the maximum warpage displacement is the smallest at 0.14 mm. A sintering preparation method for partially coated cells is proposed. These results can be used to optimize the sintering process of SOFCs and greatly reduce the sintering stress and warpage of SOFCs.