Temperature Dependence Of Mechanical Properties Research Articles

Annealing temperature-dependent microstructure, mechanical, and tribological properties of intercritically heat-treated dual-phase steel

Abstract This study investigates the role of intercritical annealing temperature on microstructural characteristics, mechanical performance, and wear resistance of DP1000 steel. As-received DP1000 steel samples in cold-rolled conditions were subjected to intercritical annealing between 730 and 880 °C with an interval of 30 °C, followed by water quenching. After heat treatment, the specimens were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), mechanical tests consisting of hardness, impact, and tensile tests, and dry sliding wear tests. The findings revealed that equiaxed ferrite grains replaced elongated ones, and the martensite ratio increased from 21% up to 64% with increasing annealing temperature. Due to the formation of equiaxed grains, the impact strength was at least doubled for each specimen by heat treatment, reaching a peak value (9.55 J cm−2) at 760 °C. The hardness (311 HB) and tensile strength (1007 MPa) of the as-received sample were higher than that of the annealed steels up to 820 °C. The mechanical strength of the samples improved at 850 and 880 °C by approximately 10%, and accordingly, the lowest wear rate was obtained at the specimen annealed at 850 °C. The increase in temperature up to 880 °C caused a decrease in wear resistance due to excessive brittleness.

Mechanical and shape-memory properties of TPMS with hybrid configurations and materials

ABSTRACT Triply periodic minimal surface (TPMS) structures with excellent properties of stable energy absorption, light weight, and high specific strength could potentially spark immense interest for novel and programmable functions by combining smart materials, e.g. shape memory polymers (SMPs). This work proposes TPMS lattices with hybrid configurations and materials that are composed of viscoelastic and shape-memory materials with the aim to bring temperature-dependent mechanical properties and additional dissipation mechanisms. Different configurations and diverse materials of polylactic acid (PLA), fiber-reinforced PLA, and polydimethylsiloxane (PDMS) are induced, generating five types of TPMS lattices, including (Schoen’s I-WP) IWP uniform lattice, IWP lattice with density gradient, hybrid configurations, hybrid materials, and filled PDMS, which are fabricated by 3D printing. The fracture morphologies and the distribution of carbon fibers are demonstrated via scanning electron microscopy with a focus on the influence of carbon fiber on shape-memory and mechanical properties. Shape recovery tests are conducted, which proves good shape memory properties and reusable capability of TPMS lattice. The combined methods of experiments and numerical simulation are adopted to evaluate mechanical properties, which presents multi-stage energy absorption ability and tunable vibration isolation performances associated with temperature and hybridization designs. This work can promote extensive research and provide substantial opportunities for TPMS lattices in the development of functional applications.

Progressive collapse resistance of self-resilient composite frames under fire conditions

Self-resilient composite frames exhibit robust resistance to progressive collapse and excellent seismic performance. However, their behavior under fire conditions is inadequately explored. This study investigates the collapse resistance mechanisms and response of self-resilient composite frame substructures (SRCFS) under fire-induced progressive collapse. A three-dimensional finite element model was developed, incorporating temperature-dependent thermal and mechanical properties of concrete and steel. Sequentially coupled thermal-mechanical analysis was conducted using the ABAQUS/Explicit solver in a quasi-static manner. Existing experimental data at both ambient and high temperatures were used to validate the proposed model. The study analyzed the contributions of steel beams and strands to vertical resistance, examining their impact on the collapse-resistance mechanism through a constant load-heating transient loading scheme. Structural responses under ambient and fire conditions were compared, focusing on different damage mechanisms. The effects of initial prestressing of strands, angle gauge length, angle thickness, and various heating curves on collapse resistance were evaluated. Findings suggest that the ISO-834 standard's failure criterion is overly conservative for SRCFS, as it neglects the enhanced load-carrying capacity provided by tensile catenary action. This mechanism offers additional escape time, enhancing personnel safety. The study identifies factors influencing the performance of SRCFS against progressive collapse under fire and proposes design recommendations.

Strain rate- and temperature-dependent mechanical properties of Ti-6Al-4V in dynamic compression: hardening and softening behaviour analysis using strain energy-based method

Strain rate- and temperature-dependent mechanical properties of Ti-6Al-4V in dynamic compression: hardening and softening behaviour analysis using strain energy-based method

Temperature-dependent mechanical properties and crystal plasticity parameters for additively manufactured Haynes-214 alloy: Experiments and numerical modeling

Our experimental mechanical testing data demonstrated that the additively manufactured (AM) laser powder bed fusion (L-PBF) Haynes-214 alloy exhibits non-linear mechanical properties as the temperature rises from ambient to 870 °C. Crystal plasticity (CP) simulations provide an effective approach to gaining deeper insights into microstructure-property linkages under thermomechanical loading. This method can reduce the need for costly high-temperature mechanical testing while accounting for the effects of crystallographic texture and grain morphology on the mechanical behavior of AM materials. However, calibrating a CP model is time-consuming because individual simulations are computationally expensive and hundreds (or more) of iterations over parameter sets may be required. To address this issue, we have designed a machine learning-differential evolution (ML-DE) CP framework that can accurately interpolate the tensile properties of AM L-PBF Haynes-214 alloy across a wide temperature range from ambient to 870 °C, with minimal reliance on experimental data. The framework uses electron backscatter diffraction (EBSD) measurements to generate statistically equivalent microstructural volume elements to serve as inputs to the CP modeling framework. Stress–strain curves were generated from 1000 CP simulations, which serve as the training data set for the three ML regression algorithms explored: linear, extra-trees, and multi-layer perceptron. These three regression models were independently evaluated to compare their efficiency and identify the most suitable algorithm for the given problem. Results revealed that the extra-trees ML regressor outperforms the other models in both qualitative and quantitative aspects with an R2 of 0.98. Subsequently, the differential evolution optimization approach is employed to calibrate the ML-based CP material parameters with experimental results obtained at various temperatures. Finally, temperature-dependent CP material parameters are formulated. The effectiveness and efficiency of the designed framework are validated through comparison with experimental results, demonstrating a high degree of agreement. These calibrated parametric constitutive equations enable further use of the CP model to study the deformation behavior of this alloy under a wide range of thermo-mechanical loading conditions.

Temperature-dependent ejection evolution arising from active and passive effects in DNA viruses

Recent experiments have demonstrated that the ejection velocity of different species of DNA viruses is temperature dependent, potentially influencing the cellular infection mechanisms of these viruses. However, due to the challenge in quantifying the multiscale characteristics of DNA virus systems, there is currently a lack of systematic theoretical research on the temperature-dependent evolution of ejection dynamics. This work presents a multiscale model to quantitatively explore the temperature-dependent mechanical properties during the virus ejection process, and unveil the underlying mechanisms. Two different assumptions of DNA structures, featuring two or single domains, are used for the early and later stages of ejection, respectively. Temperature is introduced as an influencing variable into the mesoscopic energy model by considering the temperature dependence of Debye length, DNA persistence length, molecular kinetic energy, and other parameters. The results indicate that temperature variations alter the energy landscape associated with DNA structure, leading to the changes in the energy minimum and corresponding DNA structure remaining in the capsid. These changes affect both the active ejection force and passive friction during the DNA ejection, ultimately leading to a significant increase in ejection velocity at higher temperatures. Furthermore, our model supports the previous hypothesis that temperature-induced changes in the size of viral portal pore could dramatically enhance DNA ejection velocity.

Unveiling the potential of high-temperature chemical vapour deposition growth of boron carbide: Investigating physicochemical, mechanical and electrical properties

Chemical vapour deposition (CVD) is a widely utilized technique in industry, particularly venerated for its precision and reliability in producing hard ceramic materials. In this study, a gas mixture comprising BCl3-CH4-H2 was employed to deposit boron carbide (B4C) onto a graphite substrate to investigate the substrate temperature-dependent physicochemical, mechanical, and electrical properties of the B4C. The phase compositional and vibrational characteristics of the B4C were thoroughly assessed using X-ray diffraction (XRD) and micro-Raman spectroscopy techniques, respectively. The field-emission scanning electron microscopy (FE-SEM) images reveal a morphological transition from murataite to triangular flakes, accompanied by noticeable grain expansion with growing substrate temperature. Additionally, energy-dispersive X-ray spectroscopy (EDS) indicates a consistent trend of increasing boron concentration and decreasing carbon concentration with rising substrate temperature. Consequently, variations in substrate temperature notably tune the deposition rate, mechanical and electrical properties of B4C. The deposition rate at 1200 °C was 1476 μm/h. Whereas, the material hardness and electrical conductivity of the CVD deposited B4C were found to be 3166 HV and 18.358 Ω-1cm-1, respectively. The present study highlights the importance of high-temperature CVD growth of the B4C for industrial applications.

Thermomechanical Response of Smart Magneto-Electro-Elastic FGM Nanosensor Beams with Intended Porosity

AbstractThis study investigates the behavior of free vibrations in a variety of porous functionally graded nanobeams composed of ferroelectric barium-titanate (BaTiO3) and magnetostrictive cobalt-ferrite (CoFe2O4). There are four different models of porous nanobeams: the uniform porosity model (UPM), the symmetric porosity model (SPM), the porosity concentrated in the bottom region model (BPM), and the porosity concentrated in the top region model (TPM). The nanobeam constitutive equation calculates strains based on various factors, including classical mechanical stress, thermal expansion, magnetostrictive and electroelastic properties, and nonlocal elasticity. The study investigated the effects of various factors on the free vibration of nanobeams, including thermal stress, thermo-magneto-electroelastic coupling, electric and magnetic field potential, nonlocal features, porosity models, and changes in porosity volume. The temperature-dependent mechanical properties of BaTiO3 and CoFe2O4 have been recently explored in the literature for the first time. The dynamics of nanosensor beams are greatly influenced by temperature-dependent characteristics. As the ratios of CoFe2O4 and BaTiO3 in the nanobeam decrease, the dimensionless frequencies decrease and increase, respectively, based on the material grading index. The dimensionless frequencies were influenced by the nonlocal parameter, external electric potential, and temperature, causing them to rise. On the other hand, the slenderness ratio and external magnetic potential caused the frequencies to drop. The porosity volume ratio has different effects on frequencies depending on the porosity model.

Molecular dynamics exploration of the temperature-dependent elastic, mechanical, and anisotropic properties of hcp ruthenium

Molecular dynamics calculations were performed for the hitherto unclarified temperature-dependent elastic, mechanical, and anisotropic properties of the hexagonal closed pack (hcp) ruthenium (Ru) between 0 and 1200 K. All elastic stiffness constants were found to decrease with increasing temperature. Under the examined temperature range, hcp Ru obeys Born stability conditions. Further, both Pugh ratio analyses and calculated Poisson ratio values mutually suggest the brittle character of hcp Ru between 0 and 1200 K. The intricate hardness behavior of hcp Ru was also obtained and discussed throughout the work. For the considered temperature range, hcp Ru exhibits apparent elastic anisotropy that exponentially increases with increasing temperature. Moreover, presently obtained ground state (T = 0 K and P = 0 GPa) theoretical data for hcp Ru agree well with the former experimental and theoretical data. The present findings on the temperature-dependent characteristics of this metal may further inspire future applied works.Graphical abstract

Temperature dependence of mechanical properties of equiatomic NiCoCr medium-entropy alloy printed by selective laser melting

The effects of process parameters on the densification, microstructures, and mechanical properties, as well as the temperature dependence of the mechanical properties, of a NiCoCr medium-entropy alloy fabricated with selective laser melting were studied. The results indicate that the microstructures and mechanical properties are not linearly related to the volume energy density (VED) but are affected by the scanning speed and laser power. The optimal process parameters are identified as a scanning speed of 800 mm/s and a laser power of 250 W, while the VED is only 57 J/mm3 lower than the highest value of 68 J/mm3. The yield strengths of the optimal sample are ∼819, ∼709 and ∼618 MPa at 77, 200, and 293 K, respectively. The temperature dependence of the mechanical properties is determined and verified by the experimental results.

Comprehensive Investigation of the Temperature-Dependent Electromechanical Behaviors of Carbon Nanotube/Polymer Composites.

The performances of flexible piezoresistive sensors based on polymer nanocomposites are significantly affected by the environmental temperature; therefore, comprehensively investigating the temperature-dependent electromechanical response behaviors of conductive polymer nanocomposites is crucial for developing high-precision flexible piezoresistive sensors in a wide-temperature range. Herein, carbon nanotube (CNT)/polydimethylsiloxane (PDMS) composites widely used for flexible piezoresistive sensors were prepared, and then the temperature-dependent electrical, mechanical, and electromechanical properties of the optimized CNT/PDMS composite in the temperature range from -150 to 150 °C were systematically investigated. At a low temperature of -150 °C, the CNT/PDMS composite becomes brittle with a compressive modulus of ∼1.2 MPa and loses its elasticity and reversible sensing capability. At a high temperature (above 90 °C), the CNT/PDMS composite softens, shows a fluid-like mechanical property, and loses its reversible sensing capability. In the temperature range from -60 to 90 °C, the CNT/PDMS composite exhibits good elasticity and reversible sensing behaviors and its modulus, resistivity, and sensing sensitivity decrease with an increasing temperature. At room temperature (30 °C), the CNT/PDMS composite exhibits better mechanical and piezoresistive stability than those at low and high temperatures. Given that environmental temperature changes have significant effects on the sensing performances of conductive polymer composites, the effect of ambient temperature changes must be considered when flexible piezoresistive sensors are designed and fabricated.

Hot deformation behavior and extrusion temperature-dependent microstructure, texture and mechanical properties of Mg–1Mn alloy

Mg–1Mn alloy, extruded at a low temperature in our published protocol, contributed to the intensified basal texture and extremely refined microstructure with spheroidal nanoscale precipitates dispersing throughout the matrix and along the grain boundaries, consequently resulting in the excellent mechanical properties where the alloy exhibited a tensile yield strength of 204.3 MPa and a ductility of 38.8% at room temperature. Therefore, Mg–1Mn alloy was recommended as one of the potential materials for structural applications. In the present investigation, hot deformation behavior through constitutive analysis and extrusion temperature-dependent microstructure, texture and mechanical properties of as-extruded Mg–1Mn alloy were investigated, aiming at revealing how extrusion temperature affected microstructure, texture, and mechanical properties of as-extruded Mg–1Mn alloy. X-ray diffraction patterns demonstrated that phase components of the experimental alloys consisted of the α-Mg matrix and Mn precipitates. Optical microscopy images indicated a significant increase in average grain size of the alloys as the extrusion temperature increasing from 250 °C to 400 °C. Scanning electron microscopy graphics revealed that coarsened particles identified as Mn precipitates by EDS were observed within the matrix when extrusion temperature reached 400 °C. Inverse pole figure maps of the experimental samples subjected to different extrusion temperatures in the present work exhibited the typical basal texture, suggesting that basal slip was activated hardly during the tensile stress applied along the extrusion direction. Consequently, extrusion temperature displayed the significant impact on microstructure, texture, and mechanical properties of as-extruded Mg–1Mn alloy. The alloy extruded at both 250 °C and 300 °C exhibited the strong basal texture and refined microstructure with spheroidal nanoscale precipitates dispersing within the matrix and along the grain boundaries, which contributed to their excellent comprehensive mechanical properties. The alloy extruded at 400 °C possessed the typical basal texture and coarsened microstructure, leading to the extremely poor mechanical properties. Simultaneously, the constitutive model of the Arrhenius equation based on Zener-Hollomon parameters was also established in the present investigation. Therefore, optimizing the extrusion temperature to regulate the microstructure, grain orientation distribution, and morphology of precipitates was considered as one of the effective approaches for achieving the excellent mechanical properties of Mg alloys.

Role of multi-variant deformation-induced HCP plates in cryogenic mechanical properties of an FCC high entropy alloy

We investigated the temperature-dependent mechanical properties and deformation mechanisms of the Fe49.5Mn30Co10Cr10C0.2Ti0.1V0.1Mo0.1 alloy from room temperature to cryogenic temperatures. As the deformation temperature decreased, both the strength and strain-hardening rate increased, while ductility tended to decrease. The higher strength of the material deformed at 123 K, compared to that deformed at 223 K, can be attributed to the larger number of multivariant HCP plates and higher hetero deformation induced (HDI) strengthening in the former. Multivariant deformation-induced HCP plates were the primary deformation mechanisms at all deformation temperatures, and cryogenic deformation activated intersecting shear, defined as the primary HCP plate being sheared by the secondary HCP plate. This mechanism contributed to stress relaxation and enhanced deformation accommodation. The reduced ductility observed in the material deformed at 123 K may be attributed to coarse edge and grain boundary cracks, which were more pronounced when the TRIP effect was enhanced.

Accuracy enhancement for airbag deployment simulations considering the strain rate and temperature-dependent mechanical properties of thermoplastic olefin and polypropylene

Airbags are essential automotive components that protect occupants from collisions. Airbag covers made of thermoplastic olefin (TPO) material should be deployed quickly without debris under various environments. To accurately predict airbag deployment during a collision, the mechanical properties of polymer materials at high strain rates according to temperature should be considered. In this study, a quasi-static test in the range of 0.0083, 0.0083 s−1 and a medium strain rate tensile test were performed at strain rates of 1, 10, and 100 s−1. Additionally, a split-Hopkinson Pressure bar test was performed to conduct a high strain rate tensile test at 1000, 1500, and 2000 s−1. Through this, tensile strength and failure strain were derived for each strain rate. As the polymer phase moves toward the high strain rate region, the β-transition becomes dominant, resulting in a non-linear increase in tensile strength in the Eyring plot. Based on the strain rate dependent mechanical behavior, an airbag module impact simulation was conducted to verify the effects of strain rate on airbag deployment using the LS-DYNA software. The airbag deployment analysis results showed deployment angle results similar to the actual experiment when strain rate dependent mechanical properties were applied. This is because higher strength was applied at high strain rates compared to low strain rates. Therefore, strain rate dependent mechanical properties are essential in high strain rate simulation such as collision analysis.

Cracking and thermal resistance in concrete: Coupled thermo-mechanics and phase-field modeling

Modeling damage and fracture in concrete accurately is crucial for a comprehensive analysis of structures under concurrent thermal and mechanical actions. This paper presents a novel coupled thermo-mechanical phase field model for concrete at high temperatures. Derived from principles of thermodynamics and unified phase field theory, the model integrates temperature-dependent thermal and mechanical properties, accounting for thermal expansion and transient creep. Mechanical damage, represented by the crack phase field, is augmented by a temperature-dependent thermal damage variable for heat-induced degradation. Addressing the impact of cracks on heat conduction and stress redistributions, the model introduces a novel approach to depict thermal resistance, seamlessly integrating mechanics, heat transfer, and crack propagation. Governing equations for damage evolution are derived, and the numerical implementation is detailed. Numerical illustrations showcase the model's ability to simulate diverse thermo-mechanical cracking patterns without explicit fracture path tracking or assumed criteria. Moreover, the model captures the influence of thermal actions on concrete cracking behavior and mechanical performance. This research is significant for predicting multi-field coupling damage in concrete and structures exposed to elevated temperatures.

Natural Frequency Response of FG-CNT Coupled Curved Beams in Thermal Conditions

This study investigates the sensitivity of dynamic properties in coupled curved beams reinforced with carbon nanotubes (CNTs) to thermal variations. Temperature-dependent (TD) mechanical properties are considered for poly methyl methacrylate (PMMA) to be strengthened with single-walled CNTs (SWCNTs), employing the basic rule of mixture to define the equivalent mechanical properties of nanocomposites. The governing equations of motion are derived using a first-order shear deformation theory (FSDT) and Hamilton’s principle, accounting for elastic interfaces modeled using elastic springs. A meshfree solution method based on a generalized differential quadrature (GDQ) approach is employed to discretize the eigenvalue problem and to obtain the frequency response of the structure. The proposed numerical procedure’s accuracy is verified against predictions in the literature for homogeneous structural cases under a fixed environmental temperature. The systematic investigation assesses the impact of various geometric and material properties, including curvature, boundary conditions, interfacial stiffness, and CNT distribution patterns, on the vibrational behavior.

High-temperature mechanical properties and fracture mechanism of A6B2O17 (A= Hf, Zr; B= Ta, Nb) high-entropy ceramics

A6B2O17 (A= Hf, Zr; B= Ta, Nb) high-entropy ceramics are prepared by a solid reaction method, and the temperature-dependent mechanical properties are in situ determined by a high-temperature three-point bending combined with the digital image correlation method. The results show that (Hf1/2Zr1/2)6(Ta2/3Nb1/3)2O17 (H1Z1T2N1) ceramics exhibit superior high-temperature mechanical properties. As the temperature increases from 25 °C to 1200 °C, the fracture toughness and fracture strength decrease from 3.19 MPa·m1/2 to 2.37 MPa·m1/2 and from 97.38 MPa to 72.48 MPa, respectively. The H1Z1T2N1 ceramics still maintain impressive mechanical properties at high temperatures due to the moderate grain size, low porosity and intergranular fracture. Furthermore, the higher entropy (9.61 R J/mol·K) of this ceramic leads to a significant high entropy effect, and the lattice distortion effects cause high-density dislocation regions, inducing a dislocation toughening mechanism.

Tough supramolecular hydrogels of poly(N,N-dimethylacrylamide)-grafted poly(methacrylic acid) with cooperative hydrogen bonds as physical crosslinks.

Incorporating associative interactions as the energy dissipation units has been recognized as an effective strategy to develop tough hydrogels. For hydrogen-bond associations, however, it is highly challenging to stabilize them under aqueous conditions. Although affording cooperativity can enhance and stabilize the hydrogen bonds, it usually requires stepwise polymerization to form these cooperative associations between different polymers and networks. Here, we report a series of tough supramolecular hydrogels with robust hydrogen-bond associations between grafted polymers that are synthesized by polymerization of a macromonomer of poly(N,N-dimethylacrylamide) (PDMAA) and a small monomer of methacrylic acid. The grafted chains of PDMAA form cooperative hydrogen bonds with the main chain of poly(methacrylic acid) (PMAAc), forming supramolecular hydrogels with high toughness and good stability. The tough and stiff hydrogels are in a glassy state, exhibit forced elastic deformation at room temperature, and remain stable over a wide pH range. In contrast, hydrogels prepared by the copolymerization of DMAA and MAAc are swollen and weak in water due to the lack of successive hydrogen donor/acceptor units and the absence of cooperative hydrogen bonds. In addition, these tough hydrogels exhibit good recyclability and shape memory properties, owing to the supramolecular nature of the network and the temperature-dependent mechanical properties. The influence of polymer structure on the associative interactions and macroscopic properties of the hydrogels should be informative for the design of tough soft materials with versatile applications.

Temperature-dependent mechanical properties of graphene nanoplatelet reinforced polymer nanocomposites: Micromechanical modeling and interfacial analysis

One of the challenges to be addressed in the reasonable prediction of the mechanical properties of nanocomposites at elevated temperatures is the quantitative characterization of the temperature-dependent interfacial behavior. In this study, the temperature-dependent mechanical properties for graphene nanoplatelets (GNPs) reinforced polymer-matrix nanocomposites are modeling based on the nonlinear interfacial shear stress transfer mechanism. Besides, the influence of interfacial debonding, polymer matrix plasticity, thermomechanical parameters of components, and their evolution with temperature, as well as the orientation, dimensions and volume fractions of GNPs is considered. The Young's modulus, yield/ultimate strength, and stress-strain relationships at elevated temperatures are predicted and are verified by the available experimental data. Compared to the extended room-temperature models previously established, the proposed model considering the microscopic structures achieves higher prediction accuracy with only basic material parameters input. Furthermore, the temperature-dependent interfacial mechanical behavior is analyzed. The initial strain of debonding and the maximum debonding ratio of the interface at elevated temperatures are calculated. The micromechanical modeling establishes the quantitative relationships between the temperature-dependent interfacial behavior and the mechanical properties of nanocomposites. This study deepens the understanding of the mechanical behavior of the interface and their evolution with temperature, which contributes to the prediction of the high-temperature mechanical performance and reliability analysis of nanocomposites.

Mechanical behavior and fracture characteristics of high-temperature sandstone under true triaxial loading conditions

To understand the stability of deep underground engineering rocks at high temperatures, it is necessary to conduct comprehensive tests on the mechanical properties of the rocks. In this study, a series of true triaxial tests (TTT) were conducted on sandstones using a self-developed true triaxial testing system combined with XRD, FE-SEM and CT analyses. The study systematically examined the microstructural characteristics, physical phase behavior, deformation properties and internal fracture development of the sandstone before and after heat treatment. The results of the study show that sandstone has temperature-dependent true triaxial mechanical properties after heat treatment. The stress-strain characteristic curves of the post-peak portion from room temperature to 800 °C show a significant stress-reducing segment, indicating the presence of brittle behavior. In addition, when the temperature exceeds 1000 °C, the sandstone exhibits brittle-ductile change characteristics, with a peak stress threshold observed at 800 °C. Notably, the peak stresses corresponding to 800 °C increased by 84.5 %, 63.1 %, 47 %, and 49.8 %, respectively, compared with the room temperature intermediate principal stresses(IPS) ranging from 20 MPa to 50 MPa, respectively. Importantly, the linear Mogi-Coulomb criterion remains valid for the peak strength of the high-temperature sandstone, while the internal fracture damage pattern of the specimens shows an inverted "Y" or inverted "W" configuration. The internal fracture network of rock samples above 800 °C is more complex. Intergranular crack is the main form of microcracking. This experimental study on the mechanical properties of sandstone under the combined effects of high temperature and real triaxial stresses provides valuable guidance for the selection of sandstone parameters and safety evaluation of coal underground gasification roofs.