Temperature Loading Research Articles

3D novel zero Poisson’s ratio metamaterials with programmable thermal expansion and Young's modulus

The shape stability of the structure plays a very important role in deep space exploration engineering. This paper presents 3D novel zero Poisson’s ratio metamaterial (ZPRM) with programmable thermal expansion and Young's modulus through the combination of bi-material triangles and re-entrant hexagonal structures. The coefficient of thermal expansion (CTE) and Young's modulus of the ZPRM-1 are predicted by establishing theoretical analysis models based on the classical beam theory. The mechanical response behavior of the ZPRM −1 under small deformation is simulated by finite element analysis (FEA). 3D printing is adopted to design and prepare experimental specimens, and compression experiments are carried out to certify the accuracy of the theories and FEA of Young's modulus. The results of parameter analysis show that the ZPRM-1 can tune the CTE and Young's modulus in a wide range when the geometric parameters and material combination are changed. In addition, the mechanical properties of the ZPRM-1 under the combined field of temperature and mechanical loads are investigated to achieve the tunable Young's modulus from positive to negative. This study provides a feasible reference for temperature and mechanical sensitivity instruments.

3D nonlinear finite element investigation of laminated bamboo plate strengthened prestressed concrete slab

Due to environment and recycling concerns, interest in applying natural fiber reinforced polymer (NFRP) as an alternative for glass/carbon FRP to strengthen concrete structures has been increasing. This study developed a 3D nonlinear finite element (FE) model for laminated bamboo (LB) plate strengthened prestressed concrete slab. By involving temperature load on defined temperature sensitive material, the proposed model provided good simulation of prestressing process. The accuracy of the developed model was confirmed through comparisons with experimental data, representing peak load discrepancies of only 6.5% and 8.2% for un-strengthened and strengthened slabs, respectively. The parametric study examined the impact of LB plate dimensions and tensile strength, alongside the use of FRP wraps, on concrete slab performance. The results show that the 15 mm thick LB plate can enhance the slab’s peak load by 83.2%. Variations in LB plate tensile strength by up to 10% do not significantly affect the performance of the strengthened prestressed concrete. The increases of the peak load for strengthened cases with LB plate width of 150 mm, 300 mm and 460 mm were 29.4%, 41.9% and 50.2%, respectively. It also shows that FRP end wraps can increase the performance of thick LB plate strengthened prestressed concrete slab.

Coupled thermomechanical analysis using isoparametric curved shell elements

This study focuses on the coupled thermo-mechanical formulation in isoparametric shell elements and its implementation in curved laminar structures. The formulation is based on the direct isoparametric formulation, specifically designed for flat and curved shell elements, and relies on the theory of degenerated solids. The research provides a comprehensive description of the coupled thermo-mechanical analysis, including the mechanical equilibrium equations, the interrelations between stress, temperature, displacement, deformation, and the conservation of thermal energy. It adopts a simultaneous approach to addressing the impacts of temperature and mechanical loads. The paper elaborates on various numerical examples that substantiate the formulation. These examples include simulations that encompass linear scenarios, which are then compared to analytical solutions and results derived from other numerical software. The examples highlighted include one-dimensional temperature diffusion, radial diffusion, and the thermal behavior of a cylindrical cover and a pipe under a linear temperature gradient. These simulations demonstrate the formulation's capacity to accurately capture the interactions between temperature variations and structural displacements. They also confirm the alignment of the proposed model with existing analytical and numerical solutions. In conclusion, the research provides a good framework for coupled thermo-mechanical analysis. The flexibility of the formulation is evidenced across different configurations and scenarios, accommodating various types of boundary conditions such as constant and linear temperature fields, distributed loads, and constraints on displacements and rotations. It effectively manages temperature flows across one, two, and three dimensions, highlighting its extensive applicability in the realm of structural analysis. This versatility underscores its broad applicability in the field of structural analysis.

Experimental investigation on the thermal behavior of two typical stainless steel roof systems

SummaryUnder long‐term exposure to solar radiation and temperature difference, metal roof systems produce a noticeable thermal behavior. The thermal behavior experiment of two typical metal roof systems in engineering was studied. The temperature stress and displacement of the two typical metal roof systems under different influencing factors are compared and analyzed. The results show that the thermal behavior of the stainless steel roof system is significant. The peak stress accounts for about 69.9% of the stainless steel yield strength, and the peak displacement accounts for 3/3500 of the slab span. The loading rate and temperature difference greatly influence the thermal behavior of the two typical roof systems. The maximum influence of temperature difference and loading rate on the thermal behavior is 77.8% and 67.3%, respectively. The holding temperature time has a minor influence on the thermal behavior of the two typical roof systems, and the maximum influence range is less than 7%. The research conclusions provide a valuable reference for the thermal design of metal roof systems.

Influence of Few-Layer Graphene on Frictional Properties of Lithium Compound Grease

The frictional properties of lithium compound grease (LCG) with different percentage compositions of few-layer graphene (FLG) were investigated, and the mechanisms of temperature and loading effects on LCG containing FLG are also considered. The concluding effect shows that 1 wt% FLG is more appropriate for friction and wear modifiers for lithium compound grease at elevated temperatures and less suitable at ordinary temperatures. Thickener chemisorption film, FLG layering film, and tribo-reaction film consisting of FeO(OH), Fe2O3, Fe3O4, Li2O, and other oxides assist in the establishment of a lubricating boundary film on the friction interfaces lubricated with LCG containing FLG. The poor fluidity of lithium compound grease at low temperatures leads to poor dispersion of FLG, decreasing friction reduction capability. Under elevated temperature and low load condition, adding 1wt% FLG to LCG can only improve its wear-resistant property, the abrasion volume of steel plate reduced by 24.49%. Under elevated temperature and high load condition, adding 1wt% FLG to LCG can only enhance its anti-friction characteristics.. Conversely, FLG is unsuitable as an anti-friction and wear-resistant additive for LCG at low-temperature conditions.

Structural response analysis of a solid rocket motor charge under temperature and internal pressure loads

To study the structural integrity of a solid rocket motor under low temperature load, internal pressure load, and two combined loads, based on the linear viscoelastic model, the structural response of a solid rocket motor under low temperature load, internal pressure load and two combined loads were analyzed by ANSYS finite element software, and the temperature field and strain field of charge loading were obtained. The Von Mises strain distribution of the solid rocket motor along the axial characteristic line is obtained. The results are: Under the combined action of low temperature load, internal pressure load, and two kinds of loads, the maximum Von Mises strain appears at the transition position between the blade joint and the barrel section, which is the most dangerous position for charging.

Liquid hydrogen storage and transfer-control system for integrated zero emission aviation (IZEA)

The growth in the aviation sector has highlighted the need to decrease carbon emissions, a significant factor in climate change. Hydrogen is a potential alternative clean fuel due to its high energy density. As a collaborative effort in developing integrated zero emission aviation (IZEA, a NASA ULI), we present the design concept for a liquid hydrogen storage system for short-range aircraft with a gravimetric index greater than 0.6. Our design leverages the cryogenic cooling power of liquid hydrogen to support the temperature and heat loads of various power system components, such as the high-temperature superconducting (HTS) generator, HTS motor, DC power distribution cable network, and power electronic converters. By controlling the pressure in the storage tank, we demonstrate that it is feasible to deliver the desired mass flow rate of hydrogen while effectively cooling the power system components using practical heat exchangers. Also, since heat exchangers are an integral part of our hydrogen storage and flow system, their design also impacts the overall system storage density. The entire system is designed considering the space and weight factors of an aircraft. This work represents a significant advancement towards developing the complete IZEA thermal management system for a given airplane and flight profile.

Core-rim structured MXene@SiO2 composites as oil-based additives for enhanced tribological properties

Herein, we have prepared SiO2 particles uploaded MXene nanosheets via in-situ hydrolysis of tetraetholothosilicate. Due to the large number of groups at the edges of MXene, SiO2 grows at the edges first, forming MXene@SiO2 composites with a unique core-rim structure. The tribological properties of MXene@SiO2 as lubricating additive in 500 SN are evaluated by SRV-5. The results show that MXene@SiO2 can reduce the friction coefficient of 500 SN from 0.572 to 0.108, the wear volume is reduced by 73.7%, and the load capacity is increased to 800 N. The superior lubricity of MXene@SiO2 is attributed to the synergistic effect of MXene and SiO2. The rolling friction caused by SiO2 not only improves the bearing capacity but also increases the interlayer distance of MXene, avoiding accumulation and making it more prone to interlayer slip. MXene@SiO2 is adsorbed on the friction interface to form a physical adsorption film and isolate the friction pair. In addition, the high temperature and high load induce the tribochemical reaction and form a chemical protection film during in the friction process. Ultimately, the presence of these protective films results in MXene@SiO2 having good lubricating properties.

Numerical simulations of temperature loads on multilayer Laue lenses

We present numerical simulations of the heat loads on novel diffractive X-ray optics, known as multilayer Laue lenses, exposed to high-intensity X-ray beams produced by an X-ray free electron laser (XFEL). These lenses can be used to focus XFEL beams to nanometer spots. The temperature distribution within the lens and temperature evolution as a function of incident pulse frequencies were calculated for two different lens geometries and several material pairs and material ratios of the MLLs. Simulations considered the special pulse structure of European XFEL with X-rays being delivered in pulse trains. After defining the geometric model, computational grid, material properties, and boundary conditions, a grid sensitivity study was carried out. We solved the transient heat energy transport equation in solids for mixed boundary conditions. The results of these simulations will help select materials and lens geometry for future XFEL experiments.

FINITE ELEMENT SIMULATION ANALYSIS OF CURVILINEAR CONTINUOUS BEAM BRIDGE JACKING AND TRANSLATION CONSTRUCTION

This paper investigates the issue of beam misalignment in curved continuous beam bridges. Taking the D0 to D6 spans of the Gongbin Road viaduct as the basis, the main influencing factors causing misalignment in curved beam bridges are analyzed and the causes of transverse and longitudinal misalignment in curved beam bridges are calculated and analyzed using Midas/Civil finite element simulation software. The results indicate that the main influencing factor causing misalignment in the operation of curved continuous beam bridges is the system temperature, with the displacement caused by it being larger than the cumulative displacement caused by self-weight, construction phase, gradient load, vehicle load, and bearing settlement. During operation, the failure of expansion joints changes the boundary conditions of the beam, preventing the bridge from freely expanding and contracting longitudinally under temperature load. As a result, the transverse displacement increases to 2-3 times the normal working state of the expansion joint, leading to beam misalignment.

Phonon energy dissipation in friction between black phosphorus layers.

Herein, we employ molecular dynamics simulations to decode the friction properties and phonon energy dissipation between black phosphorus layers. The observations reveal the influence of three factors, temperature, velocity, and normal load, on the friction force of monolayer/bilayer black phosphorus. Specifically, friction is negatively correlated with layer thickness and temperature, and positively correlated with velocity and normal load. The change in friction force is further explained in terms of frictional energy dissipation, and supplemented by the height of potential barriers as well as the number of excited phonons. From the phonon spectrum analysis, the phonon number at the contact interface is found to be higher than that at the non-contact interface. This is due to the larger distance of the contact interface atoms deviate from their equilibrium positions, resulting in higher total energy generated by more intense oscillations, and therefore contributes greater to friction.

Synergistic Effects of Layered Double Hydroxide and MoS2 on the Performance of Lubricants

In this study, layered double hydroxide (LDH) and molybdenum disulfide (MoS2) were used as additives to prepare lubricants. The morphology and particle distribution of the LDH and MoS2 were characterized using a scanning electron microscope and a laser particle size analyzer, respectively. Thermogravimetric analysis was used to compare the performance of the lubricants at high temperature. The extreme pressure and wear resistance performance of the lubricants were tested using a four-ball machine and a fretting-wear machine. Then, the lubricants were applied in a bolt fastener. The loosening torque and surface wear condition at high temperature were compared. By adding LDH and MoS2 to the lubricants, the extreme pressure and wear resistance performance and anti-seize performance at high temperature were improved significantly. The LDH showed better anti-seize performance than the MoS2 because of its strong and stable structure at high temperature. The MoS2 showed better anti-wear performance under a high load because of its soft layered structure. The MoS2 with a larger particle size showed better extreme pressure performance under a high load. The LDH and MoS2 played a synergistic effect under the conditions of high temperature and high load.

Mechanical behaviors of ballastless track under temperature and vehicle loads in high geo-temperature tunnel

To explore the temperature field, temperature effect and mechanical behaviors of the track structure under combined load in high geo-temperature tunnel, the temperature field test platform is built to simulate the conditions under which the track bottom is heated in high geo-temperature tunnel, and the temperature distribution of the track bed slab in the transverse, longitudinal, and vertical directions is investigated. Then, the numerical model is built to examine the displacement and stress of the track structure under temperature load and combined load consisting of temperature and static vehicle load. The results show that when the temperature load on the track bottom is 30 ℃, the vertical temperature gradient inside the slab is negative, with a maximum of 20 ℃/m, and the maximum temperature differences in the vertical, transverse, and longitudinal directions are 5 ℃, 3.25 ℃ and 2 ℃, respectively. The temperature deformation of the track bed slab is manifested as sinking in the middle and warping at the edge, with the maximum tensile stress occurring in the upper-middle region and the maximum compressive stress in the lower-middle region. Under the combined load, the most unfavorable position of the vehicle load is where the front wheel is in the center of the slab, and for every 5 tons increase in axle load, the maximum tensile stress of the slab increases by about 4%, and the maximum compressive stress increases by about 2%. The findings provide reference for the optimization design of track in high geo-temperature tunnel.

Thermal fatigue behaviors of thin-walled structures with holes: Experiments and phase field fracture modeling

The assessment of thermal fatigue behaviors of thin-walled structures with holes is a challenging task. A novel experimental approach was designed to test the thermal fatigue behaviors of thin-walled structures with holes. The experiments were conducted under three test conditions (300–850/950/1000 ℃) to investigate the behaviors of crack initiation and early propagation. The cyclic temperature loading exhibits high-transient and wide-ranging characteristics, enabling the construction of a non-uniform transient temperature field in the heating step. A thermal fatigue phase field model was developed for elastoplastic solids, and thermal fatigue fracture modeling and life prediction were performed. The phase field effectively reproduces crack morphology, and the experimental results closely match the simulation results when fatigue parameters are properly selected. Raising the upper limit of temperature will significantly diminish thermal fatigue life, accelerate crack growth, and induce a broader range of material damage. The temperature gradient in the heating step enhances the cyclic plastic behavior at the edge of the hole, significantly amplifying the detrimental impact of thermal fatigue.

Enhancing fermentable sugar production from sugarcane bagasse through surfactant-assisted ethylene glycol pretreatment and enzymatic hydrolysis: Reduced temperature and enzyme loading

In this study, an efficient coupling surfactant to ethylene glycol pretreatment (EG) and enzymatic hydrolysis of sugarcane bagasse (SCB) was proposed to enhance fermentable sugar production with lower pretreatment energy consumption and reduced enzyme loading. Under optimized conditions, 5 % Tween 80-assisted EG pretreatment of SCB achieved 80.5 % delignification while retaining cellulose (91.6 %) and hemicellulose (81.6 %) content. This led to an enhanced glucose yield of 81.3 %, compared to 65.1 % without Tween 80. The addition of Tween 80 to pretreatment modified residual lignin through etherification, reduced phenolic hydroxyl groups and enhanced hydrophilicity by 23.7 % and 9.4 %, respectively, compared to the lignin sample without Tween 80. Consequently, this modification alleviated non-productive adsorption between lignin and enzymes, improving substrate hydrolyzability. Moreover, when 4.5 % Triton-X 100 was introduced during the hydrolysis of Tween 80-assisted EG-pretreated substrates, a maximum glucose yield of 91.8 % and xylose yield of 92.6 % were achieved. Energy and enzyme cost analyses revealed a reduction of 35 % in pretreatment energy consumption and a 58.8 % decrease in enzyme costs, thanks to the synergistic action of surfactants in EG pretreatment and enzymatic hydrolysis. Overall, integrating surfactants into pretreatment and enzymatic hydrolysis holds promise for highly efficient conversion of SCB into fermentable sugars in enzyme-mediated lignocellulosic biorefineries.

Cellulosic rich biomass production with optimized process parameters by using glycerol pretreatment for biofuels applications

In this work, we conduct acidified aqueous glycerol pre-treatment (AAG) on rice husks (RH) and utilize the response surface methodology (RSM) to assess the impact of pre-treatment parameters. The primary objective of this research is to optimize the parameters to maximize the cellulose content within RH. The parameters under consideration encompassed temperature (ranging from 80 to 110 °C), retention time (spanning 15 to 45 min), and biomass loading (varying from 5 to 10 wt. %). To achieve this optimization, we perform the Box-Behnken Design (BBD) within the framework of RSM. Additionally, we scrutinize the interactive effects of these parameters on cellulose content. Our findings unveiled a remarkable increase in cellulose content, escalating from 40 % in untreated RH to an impressive 75 % in pre-treated RH under the optimized conditions of 110 °C for 45 min with a 5.0 wt. % biomass loading. To further evaluate the effectiveness of the pre-treatment process, we conduct scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses, shedding light on alterations in surface morphology and crystallinity of RH. This investigation yields valuable insights, presenting novel opportunities for the efficient conversion of readily available rice husks into high-value products, such as biofuels and composites.

Effects of load rate, heating rate, and creep on the ultimate strength and rupture of A416 7-wire strand at elevated temperature

Tensile testing was performed on ASTM A416 cold-drawn 7-wire strands under varying combinations of applied loading and high temperature in three phases: “steady-state” tests, for which increasing load is applied to a specimen at steady-state temperature; “transient” tests, for which the ambient specimen is initially loaded to a constant target tension value and the temperature is then increased until the specimen fractures; and “creep” tests, for which the specimen is subjected to a constant target combination of temperature and tensile loading for a prolonged period of time, during which it accumulates creep strains until fracturing. Temperature-induced decreases in ultimate strength and proportional limit are relatively consistent compared to the existing literature for a wide range of cold-drawn strands fabricated under different governing standards. Steady-state tests produced slightly more thermally induced strength loss compared to transient tests, which suggests that design-basis predictions that are founded on steady-state test results can be used to conservatively predict the thermally induced strength loss in strands that are increasingly heated during fire exposure. Strands loaded to a stress utilization ratio beyond 70 % of their thermally dependent ultimate strength can experience a significant increase in creep strain under prolonged thermal exposure.

Joint identification method for thermal–mechanical coupling loads

The crucial role in evaluating structural fatigue life, implementing health monitoring, and optimizing lightweight and reliable design is played by load identification technology. With the development of the aviation industry towards high-speed aircraft, the challenges under high temperature and high load conditions have been intensified. Unfortunately, in environments characterized by the coexistence of force and heat, difficulties are faced by existing load identification methods in achieving key decoupling and accurate identification of force and temperature fields. To address this gap, the Joint Identification Method (JIM), a new method that integrates force and thermal strain patterns, is introduced in this article. This method has been developed through in-depth research on “joint physical fields” and “joint basis functions.” Multiple physical fields for load identification are systematically decomposed by our method, each field is theoretically deduced, and they are seamlessly reassembled using the same structural spatial field. Through the method, mechanical strain and thermal strain are separated in high-precision temperature field reconstruction, and a basis function method for identifying the full field load distribution under a few measurement points is obtained. To verify the accuracy of our proposed Joint Identification Method (JIM), five experiments were designed, and the results consistently demonstrated the superiority of our method in accuracy (with an error always below 5%), efficiency (avoiding a large number of redundant calculations in traditional Duhamel methods), and reliability in static and dynamic load static heat identification. In the end, accurate, efficient, and reliable identification of the structural strain field, structural load field, and temperature field were achieved by our method.

Predicting Rutting Development Using Machine Learning Methods Based on RIOCHTrack Data

As the main cause of asphalt pavement distress, rutting severely affects pavement safety. Establishing an accurate rutting prediction model is crucial for asphalt pavement maintenance, pavement structure design, and pavement repair. This study explores five machine learning methods, namely Support Vector Regression (SVR), Artificial Neural Network (ANN), Gradient Boosting Decision Tree (GBDT), Random Forest (RF), and Extra Trees, to predict the development of rutting depth using data from RIOHTRack. The model’s performance is measured by comparing the performance evaluation indicators of different models, such as the coefficient of determination, root mean square error, mean absolute error, and mean absolute percentage error. The results demonstrate that integrated learning techniques such as RF, GBDT, and Extra Trees works best with R2 = 0.9761, 0.9833, and 0.9747. Moreover, the GBFT model can capture the trend of the measured rutting progression curve better than the mechanistic-empirical (M-E) model. The analysis of feature importance reveals that, in addition to external factors such as temperature and axle load, the aggregate of the asphalt concrete layer and air void crucially affect rutting. The higher the base strength, the smaller the rutting depth. The proposed model is highly straightforward and serves as an accessible analysis tool for engineers in practice.

Study on Fatigue Life of PC Composite Box Girder Bridge with Corrugated Steel Webs under the Combined Action of Temperature and Static Wind Loads

The large-span bridge is highly sensitive to temperature and wind loads. Therefore, it is essential to study the bridge’s fatigue life under the combined effects of temperature and static wind loads. This study focuses on the main bridge of Qiao Jia-fan 2# on the Yinkun Expressway (G85), with a span of 250 m and a configuration of a PC composite box girder bridge with corrugated steel webs. Firstly, on-site temperature and wind direction measurements with wind speed were conducted at the bridge site. Origin 2022 software is used to make mathematical statistics on the data, the representative values of atmospheric temperature difference between day and night and the basic wind speeds are calculated. Secondly, based on the basic wind speed in the most unfavorable wind direction, the static three-component force coefficients of bridge at different angles of attack are calculated by FLUENT 2022 R1 software. By comparison, the most unfavorable wind angle of attack, wind direction and wind load value of Qiao Jia-fan 2# Bridge are obtained. Finally, the finite element software MIDAS/FEA NX 2022 is used to analyze the fatigue life of the main bridge of the Qiao Jia-fan 2# Bridge. The analysis results show that the representative value of the temperature difference between day and night in the area where PC composite box girder bridge with corrugated steel webs is located is 22 °C, the most unfavorable wind direction is NNE wind direction, and the most unfavorable wind attack angle is 3° wind attack angle. It is found that the maximum stress of concrete and corrugated steel webs appears near the 0# block, and the life of corrugated steel webs is far greater than that of concrete.