Temperature Deformation Characteristics Research Articles

Heat transfer deformation test and model of coal during LN2 cyclic freezing and thawing process

Exploring the temperature response and deformation characteristics of coal during the freeze–thaw process is crucial for maintaining coal seam stability under liquid nitrogen (LN2) treatment and enhancing gas extraction efficiency. This study investigates the temperature diffusion and deformation characteristics of coal during LN2 cyclic freeze–thaw processes, using saturated and dry anthracite samples. Real-time monitoring of the freeze–thaw characteristics of the anthracite samples was conducted using temperature and strain detectors to quantitatively analyze the evolution of coal temperature and strain. Additionally, a nuclear magnetic resonance (NMR) testing system was used to monitor the pore evolution characteristics of the coal before and after LN2 treatment. The results indicate: After LN2 cyclic freeze–thaw, the internal pores of the saturated samples were highly developed, and fracture connectivity was enhanced, whereas the pores in the dry samples significantly decreased, leading to a sharp reduction in overall connectivity. The cooling and heating rates of the saturated samples were higher than those of the dry samples, both exhibiting exponential trends. This variation is primarily due to the phase change of pore water and the formation and expansion of the internal fracture network within the coal. The deformation magnitude of both sample types showed an overall exponential decline, with the saturated samples exhibiting higher deformation magnitudes than the dry samples. The presence of fracture water not only accelerates coal deterioration during the freeze–thaw process but also enhances coal cementation, maintaining deformation stability. Furthermore, this paper derives a temperature-strain coupling model for coal subjected to LN2 F-T cycles, aiming to provide a reference for understanding the freeze–thaw damage mechanism of coal and the practical application of LN2 fracturing.

Study on post-fire resistance of ceramsite foamed concrete sandwich composite slabs

The ceramsite foamed concrete sandwich composite slab has the characteristics of light weight and good heat insulation performance. At present, there are few research on the fire resistance of ceramsite foamed concrete sandwich composite slab at home and abroad, and the damage mechanism of ceramsite foamed concrete sandwich composite slab under fire is not clear. To fill this gap, constant load-temperature rise fire test and static loading test on five slab specimens are conducted by varying the parameters such as sandwich layer thickness, reinforcement pattern, shear span ratio and construction method. Based on the test, the results are studied, including the temperature distribution and deformation characteristics under fire, load–displacement curves, crack pattern and damage mode, residual bearing capacity of the slab after fire. The results show that ceramsite foamed concrete sandwich composite slab has good thermal insulation performance, the overall working performance, flexural bearing capacity and deformation ability of the slab is mainly affected by the slip at the composite surface. The integrity of the slab and the residual bearing capacity and ductility after fire could be significantly improved by the configuration of truss rebar. It is suggested to decrease the time difference of concrete placement at the composite surface or set shear keys and truss rebar to improve the cooperative working ability between the surface layer and the sandwich layer. Moreover, Finite Element analysis is carried out by ABAQUS software and the results show good agreement with experiment results. A new compositeness degree analysis (CDA) method for calculating the residual bearing capacity of ceramsite foamed concrete sandwich composite slab after fire considering different compositeness degree is proposed, which could be used for the practical engineering design.

Numerical Analysis of Temperature Deformation Characteristics for Super-High Arch Dams considering Solar Radiation Effects

Considering that the effect of solar radiation on the super-high arch dam temperature field remains poorly studied, the calculation accuracy of dam temperature deformation is unable to be guaranteed accordingly. To address the issue, the solar radiation effect is adequately taken into consideration by proposing a practical calculation method based on the ray-tracing algorithm, the precomputation algorithm, and the ASHRAE clear sky model in this paper. With the aid of the ASHRAE clear sky model, the solar radiation received by the super-high arch dam and reservoir water is calculated. The shading effects are calculated by means of the ray-tracing algorithm, and the precomputation technology is introduced to further enhance the computational efficiency. Finally, to guarantee the authenticity of the calculation results, the dam thermodynamic parameters are inversed by employing the hybrid genetic algorithm. Based on the application in a real-life case, we concluded that around one third of the entire dam radial temperature deformation was attributable to solar radiation during continuous sunny days. The analysis results signify a critical role for taking account of the solar radiation in dam deformation calculation. Furthermore, the practicability and utilization prospect of the proposed method was verified.

Influence of Reflective Coating on Temperature Field and Temperature Effect of CRTS III Slab Ballastless Tracks on Bridges.

To minimize the adverse effects of high temperatures on the service performance of track structures, research on the application of reflective coatings on track structures is urgently needed. Based on meteorological data and the characteristics of the multi-layer structure of the ballastless track, refined finite element models (FEMs) for the temperature field and temperature effect analysis of the CRTS III slab ballastless track structure on bridges were established. The temperature deformation characteristics and temperature stress distribution of the CRTS III slab ballastless track under natural environmental conditions were investigated. Similarly, the influence of a reflective coating on the structural temperature field and temperature effect was studied. The results showed that the temperature and vertical temperature gradient of the track slab were significantly reduced after the application of the reflective coating. Meanwhile, the thermal deformation and thermal stresses of the track slab and the self-compacting concrete (SCC) layer were minimized. Under high-temperature conditions in summer, the maximum temperature of the track slab decreased from 47.0 °C to 39.6 °C after the application of the reflective coating, and the maximum vertical temperature gradient of the track slab decreased from 61.5 °C/m to 39.1 °C/m after the application of the reflective coating. Under the maximum positive temperature gradient, the peak displacement of the upper arch in the middle of the slab and the peak displacement of the sinking in the slab corner decreased from 0.814 mm and 1.240 mm to 0.441 mm and 0.511 mm, respectively, and the maximum transverse tensile stresses of the track slab reduced from 2.7 MPa to 1.5 MPa as well. In addition, the reflective coating could also inhibit the failure of the interlayer interface effectively. The results of this study can provide a theoretical basis and reference for the application of reflective coatings on ballastless tracks on bridges.

Experimental Study on the Structural Performance of Reinforced Truss Concrete Composite Slabs during and after Fire

Standard fire resistance tests and post-fire tests on residual mechanical properties were carried out on two four-edge simply supported reinforced truss concrete two-way composite slabs with wide seam splicing (“integral seam”) and close seam splicing (“separated seam”), and the effects of the different splicing forms on the mechanical properties of the reinforced truss concrete composite slabs during and after exposure to high temperatures were explored. The results indicate that there are significant differences in terms of crack developments, moisture loss times on the slab surface, spalling characteristics of the bottom of the slab and cross-section temperature gradients of concrete and steel reinforcement along the thickness direction between the wide seam spliced reinforced truss concrete composite two-way slab (referred to as “S1 composite slab”) and the close seam spliced reinforced truss concrete composite two-way slab (referred to as “S2 composite slab”) in the fire test. This is mainly due to differences in the splicing forms and structural measures of the prefabricated base slabs at joints, which led to changes in the heat transfer path at the joints. As the temperature at the close seam can be released quickly, the stiffness recovery of the S2 composite slab is significantly greater than the stiffness weakening due to the thermal hysteresis of the concrete, so the deflection of the S2 composite slab recovers immediately after the fire stops. Overall, both the S1 and S2 composite slabs exhibit two-way high temperature deformation characteristics. The post-fire residual static load tests show that the static load-carrying capacity of the S1 composite slab is 12.08% higher than that of the S2 composite slab and the ultimate displacement is 8.74% lower than that of the S2 composite slab. It is appropriate to calculate the residual load capacities of the S1 and S2 composite slabs after the fire as a one-way slab.

Genesis Analysis of Special Deformation Characteristics for Super-High Arch Dams in the Alpine and Gorge Regions of Southwest China

During the operational period, unexpected upstream deformation has been observed in several super-high arch dams located in the alpine and gorge regions. In addition, the phenomenon of the downstream dam deformation monitoring values being apparently smaller than the numerical simulation results appears in some super-high arch dams. This paper focuses on the genetic mechanism of a super-high arch dam’s special deformation characteristics. The finite element method (FEM) was used to analyze the effects of solar radiation, valley contraction, and overhanging on super-high arch dam’s deformation behavior. First, the influences of solar radiation on the temperature field and deformation characteristics of the super-high arch dam under the shading effects of the mountain and the dam body were investigated. Second, the impacts of valley contraction on the deformation characteristics of the super-high arch dam during the storage period were studied. Subsequently, the impact of the overhanging effect on the super-high arch dam’s deformation was explored. Finally, a case study was conducted on the basis of the Jinping I super-high arch dam to evaluate the effectiveness of the proposed analytical method. It is indicated that the dam’s special deformation can be explained reasonably. Above all, in order to accurately analyze and predict the deformation characteristics of super high-arch dams in the alpine and gorge regions of Southwest China, solar radiation, valley contraction, and the dam-overhanging effect need to be considered as influencing factors of dam deformation.

High-temperature deformation characteristics of 3D printing of nano-ceramic materials

In order to improve the application effect of three-dimensional printing of nano ceramic materials, the high-temperature deformation characteristics of three-dimensional printing of nano ceramic materials were studied. First, the main raw materials and experimental instruments for preparing nano ceramic materials were selected. Then, high-temperature nano ceramic materials were prepared by using 8%, 12%, and 15% polyester modified silicone resins respectively; And put it into the storage box of the direct writing 3D printer to print the 3D ceramic sample with the 3D printer. At last, the high temperature deformation characteristics under different high temperature environments are analysed. The results show that the adhesive force and salt spray resistance of 12% polyester modified silicone resin 3D ceramic specimens are good, and the bending strength of 12% polyester modified silicone resin 3D ceramic specimen is high, its structural stability is good, and the deformation value is small under the same high temperature environment.

Analysis of the Temperature Field and Deformation Characteristics of Foam Glass Thermal Insulating Decorative Integrated Board System

Recently, foam glass thermal insulating decorative integrated board has been proposed as advanced external wall insulation. In the present study, the temperature and strain monitoring program is designed to investigate the synergistic of the integrated board and the base wall after installation on the building exterior wall. Moreover, variations of the temperature and strain fields of the system in different aging stages are studied. The obtained results show that the foam glass integrated board has an excellent performance in heat and cold preservation. It is found that the temperature difference between the concrete base layer and the finishing layer reaches 40°C. The temperature fluctuation range of the base layer is only 4°C and 9°C in hot-rain cycles and the heat-cold cycles, respectively. Moreover, it is found that the strain fluctuations of the finishing layer are relatively severe, and the deformation range of −1000με～+2500με and the plastic deformation of +1500με may occur in the hot-rain cycle, and the range of −2000με～+1500με and the plastic deformation of −600με may occur in the heat-cold cycle. Finally, the concept of thermal insulation degradation degree (D T ) is proposed. The obtained results reveal that D T rises from 0 to 0.23 in the hot-rain cycle and from 0 to 0.36 in the heat-cold cycle. Through the analysis of the strain changes, the synergistic mechanism of the integrated board and the base wall in the aging process is studied. The present article is expected to provide a theoretical guideline to design foam glass integrated boards.

Analysis of the Temperature Field and Deformation Characteristics of Foam Glass Thermal Insulating Decorative Integrated Board System

Analysis of the Temperature Field and Deformation Characteristics of Foam Glass Thermal Insulating Decorative Integrated Board System

Analysis of temperature-induced deformation and stress distribution of long-span concrete truss combination arch bridge based on bridge health monitoring data and finite element simulation

Through decades of operation, deformation fluctuation becomes a central problem affecting the normal operating of concrete truss combination arch bridge. In order to clarify the mechanism of temperature-induced deformation and its impact on structural stress distribution, this article reports on the temperature distribution and its effect on the deformation of concrete truss combination arch bridge based on bridge health monitoring on a proto bridge with 138 m main span. The temperature distribution and deformation characteristics of the bridge structure in deep valley area are studied. Both of the daily and yearly temperature variation and structural deformation are studied based on bridge health monitoring. Using the outcome of monitoring data, three-dimensional solid finite element models are established to analyze the mechanism of temperature-induced deformation of the whole bridge under different temperature fields. The influence of temperature-induced effect is discussed on local damage based on the damage observation of the background bridge. The outcome of comparisons with field observation validates the analysis results. The relevant monitoring and simulation result can be referenced for the design and evaluation of similar bridges.

High temperature deformation and dynamic recrystallization behavior of AlCrCuFeNi high entropy alloy

The high temperature deformation and dynamic recrystallization characteristics of multicomponent AlCrCuFeNi high entropy alloy, composed of simple FCC and BCC phases were studied in detail in the temperature range of 900–1050 °C and in the strain rate range of 0.001–1 s−1 by generating contour maps of multiple models using a high temperature thermomechanical simulator test. The processing maps consisting of dissipation and instability maps show that the suitable areas for TMP are at 900–920 °C/10−1.5–10−3s−1 and 1000–1050 °C/10−2.5–10−3s−1. In contrast, two instability zones at (900–920 °C/10−0.75~1s−1 and 1000–1050 °C/10−0.5~1s−1) should be avoided during hot processing. EBSD analysis indicates that the volume fraction of dynamic recrystallization decreases with increasing deformation rate after hot compressive deformation at 1050 °C for different strain rates.

Prediction of high temperature deformation characteristics of an Fe-based shape memory alloy using constitutive and artificial neural network modelling

The high temperature deformation characteristics of an Fe-28Ni-17Co-11.5Al-2.5Ta-0.05B (at.%) shape memory alloy (SMA) were studied by high temperature compression testing under large temperature (1323–1473 K) and strain rate (0.01–10 s−1) ranges. These were predicted by applying the Arrhenius-type and strain-compensated Arrhenius-type constitutive models, and the artificial neural network (ANN) model to the results obtained from the experiments. The capability of the models for prediction was assessed as a function of the correlation coefficient (R) and the relative percentage error. The results reveal that the true stress prediction by the strain-compensated Arrhenius-type constitutive model is more precise at a lower strain rate (0.01 s−1) than at a higher strain rate (10 s−1). Moreover, it yields better results in comparison with those obtained from Arrhenius-type model. They further reveal ANN model shows higher efficiency and preciseness in forecasting the high temperature flow characteristics of the SMA as compared to the strain-compensated Arrhenius-type and Arrhenius-type models.

High Temperature Deformation Characteristics of an Alumina‐Forming Stainless Steel

This investigation study deformation characteristics of an innovative stainless steel, alumina‐forming austenitic (AFA) Fe–20Cr–30Ni–0.6Nb–2Al–Mo steel, at elevated temperature, and those isothermal hot compression tests are performed with various temperatures and strain rates. The results show that as the temperature decreases (or as strain rate rised), the stress level increases. On the other hand, in order to better predict the flow stress behavior, a modified constitutive relationship model is established based on the strain‐compensated Arrhenius‐type equation, and the accuracy of this modified model is examined statistically. Furthermore, by comparing with the experimental results, this modified constitutive model is proved to be able to precisely predict the high temperature flow behaviors of the AFA alloy. In addition, processing maps of this alloy are also constructed, and expanded instability regions are found with higher strain rate values (above 0.18 s−1). Moreover, from the microstructure characterization, the features of both adiabatic shear bands and flow localization are formed in those samples of instability regions. Eventually, the optimum high temperature deformation parameters can be determined as 1050–1120 0.01–0.1 s−1 and 1120–1150 °C/10−0.5–10−1.5 s−1 for this AFA alloy.

High Temperature Deformation Characteristics of Al-Zn-Mg Alloy Modified with CaO-Added Mg.

Hot torsion tests were performed on an Al-Zn-Mg alloy modified with CaO-added Mg to investigate the effects of the Mg additive on the high temperature deformation characteristics. Effective stress- strain curves and processing maps were established from the experimental results under a range of deformation conditions. The fracture strain of the CaO-added Al-Zn-Mg alloy was higher than that of the Al-Zn-Mg alloy. The CaO-added Al-Zn-Mg alloy did not show an instability region in the processing map but the commercial Al-Zn-Mg alloy exhibited adiabatic shear bands at low temperatures and at a high strain rate. The results shown in this study were attributed to the reduction of the second phase by the addition of CaO-added Mg.

Thermal Deformation Behavior and Formability of High Temperature with Corrosion Resistance Alloy

The aim of present wor is, therfore, to investigated the effect of the damage value prediction equation on the formability of compression specimen and find the optimize forming condition.Although Inconel 625 alloys are excellent materials, Ni-base alloy cannot be formed at room temperature owing to limitation of formability. To improve the formability of Inconel 625, it is necessary to investigate the formability at a high temperature range.A high temperature compression test is performed with a Gleeble 3500 testing machine at various temperatures (approximately 900 1200°C) and strain rates (10/s and 30/s) to obtain high temperature deformation characteristics of Inconel 625. Furthermore, high temperature tensile tests results are used to measure elongations and reductions in the area of Inconel 625.A rigid-plastic finite element simulation is applied to the high temperature compression process to obtain the damage valueThe results of the hot deformation experiment and analysis are presented for various conditions of temperatures and strain rates, and it is expected that damage value will be used in hot forming processes such as hot extrusion and rolling process.

Elevated Temperature Deformation Characteristics of 15Mn7 Steels

Isothermal compression deformation tests of medium-Mn (0.15C-7Mn in wt%) steels (15Mn7) at elevated temperatures were carried out on a Gleeble-3500 thermal mechanical simulator. Hot deformation behavior of the steels was examined with a constant strain rates of 0.001, 0.01, 0.1 or 1 1/s between 1150 ºC and 900 ºC. The effects of deformation strain rate (0.001~1 1/s) and temperature on compression behavior of the steels was studied. It shows that the deformation conditions have significant influence on stress-strain curves of the steel. The curve shows obvious dynamic recrystallization style at high temperature, and low strain rate or dynamic recovery or work-hardening style at low temperature and high strain rate. The deformation resistance decreases with deformation temperature increasing and strain rate decreasing, and the peak stress and peak strain both decrease, which demonstrates that dynamic recrystallization is more easily to occur at high deformation temperature and low strain rate. The austenite hot deformation equation was established as following. And the corresponding hot deformation activation energy Qdef for the steel is 320.984 KJ/mol.Z0.15c−7Mn = ε˙exp(320984/RT) = A[sinh(ασ)]n = 1.15 × 1010[sinh(0.0156σp)]4.01

Modeling high temperature deformation characteristics of AA7020 aluminum alloy using substructure-based constitutive equations and mesh-free approximation method

This research was aimed to assess the potential of a radial basis function (RBF) approximation method against the dislocation substructure-based constitutive model in predicting high-temperature deformation behavior of the AA7020 aluminum alloy. Hot compression tests were performed over a range of strain rate of 0.1–100 s−1 and a range of temperature of 350–500 °C up to a strain of 0.6. The hot deformation behavior of the alloy was first described by a substructure kinetic-based constitutive equation, with the effects of strain, strain rate and temperature together with dynamic recovery parameters taken into consideration. A RBF approximation method was then developed to model the flow behavior of the material. The RBF model, as a kind of novel mesh-free function estimation approach, was trained and tested with the obtained datasets from the hot compression tests. The performance of the developed analytical and neural computational models was evaluated using statistical criteria. The results showed that the RBF model was more proficient and accurate in predicting the hot deformation behavior of this aluminum alloy than the substructure-based constitutive model.

State parameter-based constitutive modelling of stress strain curves in Al-Mg solid solutions

A novel and comprehensive approach addressing the stress strain response of binary Al-Mg alloys under uniaxial loading over a wide range of temperatures (78 K–650 K), strain rates (10−4–10 s−1) and solute contents (0 wt.%–5 wt.%) is developed and introduced. The model is based on the mechanical threshold Ansatz in combination with a Labusch type solid solution hardening approach and a model for dynamic strain ageing to describe the temperature and strain rate dependence of the yield stress in a thermal activation framework. Strain hardening is modelled on basis of the Kocks-Mecking evolution equations for the average dislocation density and discussed in terms of the temperature-dependence of the initial strain hardening rate and the saturation stress for stage-III hardening. Both, static and dynamic recovery, are fully taken into account. The model predictions are validated on experimental stress-strain curves reported in literature. The results demonstrate that the model successfully reproduces the complex temperature and strain rate dependent plastic deformation characteristics of Al-Mg alloys with a minimum of calibration input parameters.

Hot deformation characteristics and microstructure evolution of Hastelloy C-276

High temperature deformation characteristics of Hastelloy C-276 was investigated using compression tests at elevated temperature ranging from 900°C to 1200°C and strain rates covering quasi-static to quasi-dynamic regions (0.001s−1-10s−1) to a final true strain 0.69 (50% Engineering strain). The flow curves at all strain rates and high temperatures (1100°C, 1200°C) exhibit a peak stress, confirming the dynamic recrystallization (DRX) phenomena. To predict and establish the safe hot workability window, processing maps were evaluated based on the dynamic material model and plotted for strain of 0.65. Based on the detailed microstructure analysis and the identification of the active softening mechanisms, the optimal hot workability window was found to be 1200°C and 0.001s−1. Bulk texture analysis revealed presence of fiber textures <011> and <001> parallel to deformation axis (ND), which were prevalent at high temperature and low strain rate conditions. Using Arrhenius model, the apparent hot working activation energy (QHW) was determined as 474kJ/mol. Zener-Holloman parameter was calculated to gauge the deformation resistance and found to have a linear relationship with peak flow stress at given deformation conditions.

Characteristics of Transformation and Low-temperature Deformation of Ti-51.1Ni Shape Memory Alloy

Abstract Effects of annealing temperature on the phase transformation and the low temperature deformation characteristics in the deformed Ti-51.1Ni (at%) shape memory alloy (SMA) were investigated by differential scanning calorimetry (DSC), optical microscope (OM) and tensile test. The results show that the transformation types of Ti-51.1Ni alloy are changing from A→R/M→R→A to A→R→M/M→R→A to A→R→M/M→A (A-parent phase B2, R-R phase, M-martensite phase) upon cooling/heating along with increasing annealing temperature. The R transformation temperatures and martensite temperature hysteresis decrease, while the M transformation temperature increases and the R temperature hysteresis nearly keeps at about 6.5 °C. When deformation happen at 10 °C, the 400∼550 °C annealed Ti-51.1Ni SMA exhibits as the shape memory effect (SME) + superelasticity (SE), the 600∼700 °C annealed SMA shows SE, and the characteristics of alloy change from SME + SE to SE. In addition, the annealing recrystallization temperature of Ti-51.1Ni SMA is 590 °C, and the 590∼650 °C annealed alloy could obtain excellent capability of plastic deformation and 50.83 % values of fracture strain, so the forming processing temperature could be in the range of 590∼650 °C. When the Ti-51.1Ni alloy are used for energy consumption of damper and damping device, the suitable annealing temperature could be higher than 550 °C, and for making superelastic device, the suitable annealing temperature could be below 400 °C or above 600 °C.