Effect Of Temperature Rise Research Articles

Effect of temperature rise caused by fire on the physical and mechanical properties of concrete

In the past few years, several concrete constructions have suffered major fires, causing very significant damage to the structure. The fire resistance of concrete depends on some of its characteristics such as the nature of the components used for its formulation, permeability, water content and mechanical resistance. In the places most exposed to fire, all the coating can be expelled, which seriously threatens the bearing capacity of the construction. In addition, the financial loss due to repair over a long period can reach several million Euros. This paper presents the physical and chemical transformations caused by the increase in the temperature of concrete in the event of a fire. These transformations mainly have an effect on the microstructure, the mechanical properties and the thermal deformation of concrete. The two phenomena of flaking and spalling of concrete were also studied in order to know their origins and found the methods of preventive. Indeed, flaking can manifest itself explosively, and have significant consequences on the resistance of concrete. It thus reduces the cross-section of the structure and also decreases its bearing capacity, which leads to an increase in the risk of structural failure. The factors influencing the flaking phenomenon were also presented.

Study on the wear characteristics of cylindrical needle bearings on the crankshaft of RV decelerator

PurposeThe purpose of this study is to systematically analyze the wear of cylindrical needle bearings in rotary vector reducers under temperature rise and identify the influencing factors.Design/methodology/approachBased on the dynamic characteristics of the RV-20E reducer, the time-varying contact force of the cylindrical needle bearing and the entrainment speed of the inner and outer raceways were calculated. A mixed elastohydrodynamic lubrication model of the needle bearing, considering friction and temperature rise, was established using a dynamic rough tooth surface model. The model solved for the oil film thickness, contact stress and wear conditions of the bearing raceway contact area. The effects of the number of rolling needles, the diameter of rolling needles and surface strength on the wear characteristics were analyzed.FindingsThe results of this study show that the oil film thickness, oil film pressure and surface scratches of cylindrical needle bearings exhibit an uneven, patchy distribution under the combined effects of friction and temperature rise. When the radius of the rolling needle is less than 1.44 mm, inner ring wear is less than outer ring wear. Conversely, when the radius exceeds 1.44 mm, inner ring wear is greater. The optimal rolling needle radius is 1.6 mm. Increasing the number of rolling needles and enhancing the yield strength of the contact surface significantly extend bearing life.Originality/valueThis study provides valuable recommendations for optimizing bearing structural parameters and material characteristics in the design of rotary vector reducers.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2024-0242/

Effects of Non-Uniform Temperature Distribution on the Degradation of Liquid-Cooled Parallel-Connected Lithium-Ion Cells

Our previous work on an air-cooled stack of five pouch-format lithium-ion (Li-ion) cells showed that non-uniform temperature can cause accelerated degradation, especially of the middle cell. In this work, a stack of five similar cells was cycled at a higher C-rate and water-cooled to create a larger temperature gradient for comparison with the air-cooled stack. It was hypothesized that the larger temperature gradient in the water-cooled stack would exacerbate the degradation of the middle cell. However, the results showed that the middle cell degraded slightly slower than the side cells in the water-cooled stack. This trend is opposite to that in the air-cooled stack. This difference could be attributed to the combined effects of a smaller temperature rise and larger temperature gradient in the water-cooled stack than in the air-cooled stack. Post-mortem analysis of cycled cells and a fresh cell showed that the degradation mainly came from the anode. Increased lithium plating and decreased porosity in the side cells are possible mechanisms for the faster degradation compared with the middle cell. It was also found that all the cells in the water-cooled stack experienced a phenomenon of capacity drop and recovery after a low C-rate reference performance test and extended rest. This phenomenon can be attributed to lithium diffusion between the anode active area and the anode overhang area.

Multi-energy field simulation and experimental research on laser composite machining of micro-holes

Thin-walled micro-holes are frequently used in aerospace components to achieve specific functions, such as heat dissipation and filtration. However, traditional manufacturing technologies face difficulties in achieving precision machining of these holes due to deformation caused by cutting force or heat. Laser machining is a highly flexible and efficient advanced processing technology that aims to achieve precise machining of thin-walled holes. However, it is important to note that the thermal energy generated by the laser can cause deformation of the thin walls. To address these issues, this paper proposes a process that combines laser and backside electrochemical composite machining. The model for laser electrochemical composite processing after through-hole formation suggests that the laser's temperature rise effect on the electrolyte can significantly enhance the efficiency of electrochemical processing. Furthermore, the laser exerts a micro-zone stirring effect on the electrolyte in the processed micro-zone, which promotes the liquid-phase mass transfer process during the electrochemical reaction. Furthermore, a one-way experiment was conducted to investigate the effects of the main laser parameters on the processing results. The results indicated that higher laser power, as well as lower laser frequency and scanning speed, significantly reduced the edge damage and pore taper of the processed micro-holes. The language used is clear, concise, and objective, adhering to a formal register and avoiding biased or ornamental language. Technical terms are consistently used and explained when first introduced. The text is grammatically correct and free from spelling and punctuation errors. Furthermore, this process has significantly reduced the oxygen content and surface roughness of the sidewalls of the micro-holes.

Assessment of Thermal Osteonecrosis during Bone Drilling Using a Three-Dimensional Finite Element Model.

Bone drilling is a common procedure used to create pilot holes for inserting screws to secure implants for fracture fixation. However, this process can increase bone temperature and the excessive heat can lead to cell death and thermal osteonecrosis, potentially causing early fixation failure or complications. We applied a three-dimensional dynamic elastoplastic finite element model to evaluate the propagation and distribution of heat during bone drilling and assess the thermally affected zone (TAZ) that may lead to thermal necrosis. This model investigates the parameters influencing bone temperature during bone drilling, including drill diameter, rotational speed, feed force, and predrilled hole. The results indicate that our FE model is sufficiently accurate in predicting the temperature rise effect during bone drilling. The maximum temperature decreases exponentially with radial distance. When the feed forces are 40 and 60 N, the maximum temperature does not exceed 45 °C. However, with feed forces of 10 and 20 N, both the maximum temperatures exceed 45 °C within a radial distance of 0.2 mm, indicating a high-risk zone for potential thermal osteonecrosis. With the two-stage drilling procedure, where a 2.5 mm pilot hole is predrilled, the maximum temperature can be reduced by 14 °C. This suggests that higher feed force and rotational speed and/or using a two-stage drilling process could mitigate bone temperature elevation and reduce the risk of thermal osteonecrosis during bone drilling.

Buckling analysis of FGM shells of revolution in thermal environment

This work presents an analytical investigation for analyzing the mechanical buckling of shells of revolution made of functionally graded materials, subjected to external uniform pressure taking into account the effects of uniform temperature rise. The material compositions only vary smoothly along its thickness direction with the power law distribution. Using the adjacent equilibrium criterion and classical shell theory, the linearization stability equations have been established. The resulting equations which they are the system of three variable coefficient partial differential equations in terms of displacement components are investigated by Galerkin method. The closed-form expression for determining the critical buckling load is obtained. In numerical results, the effects of material properties, dimensional parameters, and temperature on the buckling of shells of revolution are discussed in details.

Considering Joule heating in coupled electroporation and electrodeformation modeling of glioblastoma cells

Cells exposed to a pulsed electric field undergo electroporation(EP) and electrodeformation(ED) under electric field stress, and a coupled model of EP and ED of glioblastoma(GBM) taking into account Joule heating is proposed. The model geometry is extracted from real cell boundaries, and the effects of Joule heating-induced temperature rise on the EP and ED processes are considered. The results show that the temperature rise will increase the cell's local conductivity, leading to a decrease in the transmembrane potential(TMP). The temperature rise also causes a decrease in the dynamic Young's modulus of the cell membrane, making the cell less resistant to deformation. In addition, GBM cells are more susceptible to EP in the middle portion of the cell and ED in the three tentacle portions under pulsed electric fields, and the cells undergo significant positional shifts. The ED of the nucleus is similar to spherical cells, but the degree of ED is smaller.

Thermal and electric field driven rf breakdown precursor formation on metal surfaces

The phenomenon of electric breakdown poses serious challenges to the design of devices that operate in high electric field environments. Experimental evidence points toward breakdown events that are accompanied by elevated temperatures and dark current spikes, which is attributed to high-asperity nanostructure formation that enhances the local electric field and triggers a runaway process. However, the exact mechanistic origin of such nanostructures under typical macroscopic operational conditions of electric field and magnetic-field-mediated heating remains poorly understood. In this work, we simulate the evolution of a copper surface under the combined action of the electric fields and elevated temperatures. Using a mesoscale curvature-driven surface evolution model, we show how a copper surface can undergo a type of dynamical instability that naturally leads to the formation of sharp asperities in realistic experimental conditions. Exploring the combined effect of fields and temperature rise, we identify the critical regimes that allow for the formation of breakdown precursors. The results show that thermoelastic stresses, while not essential, can significantly lower the critical electric field required for runaway surface instability, which is consistent with experimental observations that thermal effects can increase breakdown rates. Published by the American Physical Society 2024

How to quantify the regional effects of ocean temperature rise due to climate change: implications of Octopus maya ecophysiology on food security of the Yucatan shelf artisanal fishermen

The vital survival, maturation, and reproduction rates of Octopus maya were formulated according to the thermal preferences in each stage (juvenile and adult) and the bottom temperature of the Yucatan shelf projected from different shared socioeconomic pathways (SSPs): SSP1-5, to describe the species population growth in shallow waters. The dispersion of each individual in the population and the spread of the offshore population were incorporated with an integrodifference equation. For each SSP, the food security of the artisanal fishermen in the Western, Central, and Eastern Yucatan shelf region was analyzed based on the proposed availability, access, and utilization indices of Octopus maya as food. The analysis was complemented with an average monthly protein and income poverty indicators that this species’ shallow water fishery would have the capacity to supply by the year 2100. Although the proportion of the legally O. maya catchable population may be favored with the gradual increase in temperature in the coming years, this increase may not translate into greater food security for the artisanal fishermen who catch this species in shallow waters. Moreover, this fishery alone may not have the capacity to supply the average annual intake of 10.6 kg of protein per person recommended and maintain fishermen and their families above the income poverty line by 2100.

Numerical study on the effect of temperature rise of humeral bone nails in magnetic resonance imaging based on the finite-element method.

Humeral fracture is a common long bone fracture in orthopedic clinical diagnosis and treatment. To investigate the local temperature increase owing to changes in the specific absorption ratio (SAR) of the human body caused by humeral bone nails during magnetic resonance imaging (MRI). A refined geometric model of the upper body was constructed via data segmentation and post-processing using the digital human image dataset. Finally, the geometric model was imported into COMSOL, a 3-T magnetic resonance coil was built, and the operating frequency (128 MHz) was set to analyze the SAR of the bone-nail pair and temperature changes. The analysis of the changes after bone-nail implantation under different tissue conditions revealed that the SAR and temperature after implantation and fixation were three times higher than those before, and the areas with abrupt changes in SAR and temperature were primarily concentrated in the bone-nail area. In MRI, metal implants can cause local elevation of the SAR near the implant in the human body, resulting in a temperature increase around the implant. Consequently, long-term scanning can damage the human body.

Safe Operating Conditions of isoperiodic Homogeneous Semi-Batch Reaction Based on Parameter Uncertainties Analysis

Proper operating conditions have a significant impact on the process state of semi-batch reaction. However, various error and bias lead to the uncertainties of parameter, which affect process safety of the semi-batch reaction. In this work, the effect of dimensionless parameters dimensionless adiabatic temperature rise (), Westerterp number (Wt), , dimensionless activation energy (γ), volumetric heat capacity ratio (RH) and relative volume increase (ε) on the temperature of the isoperiodic homogeneous semi-batch reaction are investigated by local sensitivity analysis. The sensitivity of the dimensionless maximum temperature to global parameters is analyzed using the scatter plot method based on Monte-Carlo sampling. Parameter sensitivity results are further quantitatively calculated by the eFAST method. The results indicate that there is a strong linear relationship between the maximum reaction temperature and △τad,0, which exhibits the highest sensitivity index compared to the other parameters. The safety boundary diagram and adiabatic temperature diagram are constructed by considering parameter uncertainty and the effect of parameter uncertainty on the critical criteria is analyzed.

Decoupling the Effects of Strain Rate and Temperature Rise on Martensitic Transformation in a 316 Austenitic Stainless Steel

Decoupling the Effects of Strain Rate and Temperature Rise on Martensitic Transformation in a 316 Austenitic Stainless Steel

Effect of temperature rise on the mechanical behaviour of deep-sea clay surrounding oil and gas pipelines

The mechanical behaviour of deep-sea clay is crucial for oil and gas pipeline safety and is traditionally assessed through in situ penetration testing, which is usually conducted in a low-temperature environment (usually at temperatures lower than 4 °C). However, the temperature of deep-sea clay surrounding high-temperature pipelines can reach approximately 20 °C. To date, the influence of temperature variation on the mechanical properties of deep-sea clay, especially strain-softening behaviour, has been largely overlooked, posing a safety risk to practical engineering. Consequently, this study first establishes a temperature-controlled cyclic penetration testing platform. Then, an enhanced mini-spherical penetrometer is employed to investigate the undrained strength and strain-softening behaviour of undisturbed deep-sea clay samples at 4 °C, 10 °C and 20 °C. In particular, an improved framework is proposed to quantitatively characterize the mechanical behaviour. Finally, a strain-softening law considering temperature variations is established and rigorously validated through in situ tests. The findings underscore several significant observations: (a) deep-sea clay in its intact state exhibits a heightened sensitivity to temperature variations compared to that in its remoulded state; (b) temperature variations influence the strain-softening parameters of deep-sea clay, resulting in distinct behaviours; and (c) the proposed strain-softening law considering temperature variations is verified to be more logical.

Effect of negative bias voltage on microstructure and thermal stability of Cu/Nb nano-multilayers deposited by FCVA technique

he deposition energy is a crucial factor in the preparation of nano-metallic multilayers using the physical vapor deposition method. To study the effect of deposition energy on the microstructure and performance of coatings, Cu/Nb nano-multilayers were prepared by the FCVA technique with different negative bias voltages. The surface morphology, composition, and interface structure were investigated by SEM, XRD, and TEM. The results indicated that the increased negative bias voltage leads to compressive stress and the temperature rise effect, which promotes the formation of psedo-diffuse transition zones and the transformation of columnar to equiaxed crystals. In addition, the difference in hardness is used to characterize the structural integrity of the laminate structure of the material after heat treatment. Even after one hour of annealing at 600 °C, the sample retains a highly stable laminate structure when the negative bias voltage is set to -100 V, and its hardness reduces by just 22.3%. The mechanisms of the pseudo-diffuse transition zone and crystal structure on thermal stability were discussed.

A study on the effect of temperature rise on the effectiveness of detecting typical defects in rubber-impregnated paper sleeves

Epoxy rubber-impregnated paper casing has the advantages of stable electrical performance, explosion-proof function, small volume, lightweight, etc., and has been widely used in transformer casing and through-wall casing. However, its manufacturing process is complex, which makes it easy to produce defects in the production process, and it is difficult to detect certain defects in the test at room temperature. To study the partial discharge and dielectric loss characteristics of typical defects of rubber-impregnated paper bushings after temperature rise, we designed and prepared defective bushings with moisture, metal particles, and core cracks, and measured the partial discharge pattern and dielectric loss factor of the bushings after they were heated to a certain temperature. The results show that the core crack defective casing discharge increases more after heating, followed by moisture defective casing, and metal particles defective casing has the smallest impact, indicating that for the temperature rise test in the thermal state of the core crack, moisture defective casing detection effect is better. The results of the study can provide certain references and guidance for the factory inspection and troubleshooting of rubber-impregnated paper casing.

A long secondary linear traction motor analysis based on electromagnetic-thermal-fluid coupling

The temperature analysis of the motor is critical for its functioning and durability as it has a significant impact on enhancing its efficiency. The purpose of this paper is to design a rational water cooling system for the Double-sided Linear Flux Switching Permanent Magnet motor (DLFSPM), thereby reducing the adverse effects of temperature rise. This paper conducts electromagnetic fluid and thermal analyses of DLFSPM. It also designs a rational cooling structure to reduce the temperature rise while running thereby contributing to its operation reliability. The electromagnetic-thermal-fluid coupling model provides a feasible solution for reducing the temperature increase of the DLFSPM motor under rated operating conditions, thereby enhancing its overall performance.

Responses of financial stress and monetary policy to global warming: Evidence from China

We explore the marginal dynamic effect of abnormal temperature rise on China's financial stress and monetary policy using monthly data from January 2002 to December 2019. Our empirical results demonstrate that: (a) China's financial stress has a positive response to an increase in abnormal temperature change shock significantly, especially in the 4–7 months after the shock; (b) the introduction of monetary policy regulation into the economic system can effectively alleviate the financial instability caused by the rise in temperature; (c) from the perspective of the effectiveness of monetary policy transmission, price-based monetary policy is generally better than quantity-based monetary policy; (d) the adjustment of monetary policy can effectively expand the financing scale of the whole society with credit scale mattering most; (e) when financial stress is higher, the impact of a temperature shock on the financial market is stronger, as the stabilizing effect of expansionary monetary policy is more obvious. Our results are robust to wider checks and have important policy implications.

The study of numerical simulation and texture of soybean protein based on high moisture extrusion with different screw elements

Extrusion conditions and suitable screw configuration are key factors that affect protein reactivity and thus the properties of the blend. Fully revealing the whole extrusion process using numerical simulation is still a strong challenge due to the complexity of the flow field. In this paper, the flow behavior of protein under the action of kneading block and kneading block-reversing element was further revealed through the equivalent substitution, and the quality attribute of the extruded protein was also investigated. The results demonstrated the fluid pressure inside the barrel presented as a stepped and jagged increasing trend, and higher temperature and lower viscosity can be obtained at the screw root. The outlet pressure loss decreased when kneading block approached the outlet. Since the more complex fluid flow state at the location of the reversing element, more mechanical energy is transformed into internal energy, which amplifies the effect of temperature rise. Compared to the kneading block, the introduction of a reversing element can effectively improve the hardness and texturization of the extruded product, increase the brightness of color, and a better performance can be obtained at the backward reversing element. Overall, the consistency between the numerical simulation and the experimental results provided a research basis for the optimization of screw design combinations, and new theoretical support for the subsequent processing of meat analogs.

Study on the Influence of Product Thermal Effect on Thermal Vacuum Test

Due to different applications, the size, shape and surface state of the power supply on spacecraft vary greatly, but they all need to experience a harsh environment, such as extreme vacuum, cold and hot alternation. Therefore, it is necessary to undergo the thermal vacuum test on the ground. During the thermal vacuum test, the aerospace power supply products with different surface states have different internal temperature rise effects due to their own emissivity and absorption during testing. The higher the temperature rise effect, the lower the product reliability. Therefore, in order to reduce the temperature rise effect of products in the process of thermal vacuum test, the temperature rise effect of products with different surface states or the same surface state can be reduced by using different shading measures in the thermal vacuum test of products is analysed and verified by experiments. The test results show that the product with bright surface has lower temperature rise effect than the product with blackened surface, which can reduce the maximum temperature difference, enhance the uniformity of temperature field and enhance the reliability of the product. In addition, using measures such as covering the product with aluminized film or overhanging it can reduce the surface temperature difference, with the overhanging shade being more effective.

Investigation of RBF-SMC Control Strategy for Vertical Dynamics of Maglev Car Considering Temperature Rise Effects

Investigation of RBF-SMC Control Strategy for Vertical Dynamics of Maglev Car Considering Temperature Rise Effects