Creep Rate Research Articles

СТІЙКІСТЬ ЗАЛІЗОБЕТОННИХ СТІЙОК ПРИ КОРОТКОЧАСНІЙ ТА ТРИВАЛІЙ ДІЇ НАВАНТАЖЕННЯ

The behavior of hinged support at the ends of the rack with initial bending under the action of load is considered. Spring rods are arranged symmetrically. The rack has an initial bend, compressed by forces constant in time. All real elements have one or another imperfections in the form of technological bends, therefore, they begin to bend from the very beginning of the load. The load, when it is exceeded even by an infinitesimally small amount, there is a loss of stability of this type of deformation, is called critical. In the calculation of stability under the long-term action of external forces, it is necessary to determine the load, at which the rate of movement in time monotonically decays. Solving the problem in such a setting is acceptable for systems, the development of movements of which in time leads to a change in the stress state. This condition for a compressed rack is fulfilled only in the presence of initial imperfections (initial bending, off-center application of compressive force, etc.). When solving the problems of the theory of stability, taking into account the creep of the material plays an important role. Creep can be limited in time or unlimited. When solving the problem of the stability of racks with initial imperfections, made of a material that has creep and reinforced with elastic rods, the following assumptions are made: 1) the hypothesis of flat sections is considered valid; 2) the deformations of the creeping material and the elastic rods at the points of contact are the same; 3) the modulus of deformations during stretching and compression are equal; 4) the creep material works in the stretched zone without the appearance of cracks. The relationship between deformations and elasticities in the material of the rack is established by a formula based on the linear relationship between deformations and elasticities. The creep rate of concrete is based on the hereditary theory of aging. In the work, an integro-differential equation was obtained - the equation of slow motion of the rod, expressions were obtained for the study of bends in any at what point in time, the formula for determining the critical force with long-term load action is derived.

Triaxial creep test and damage model study of layered red sandstone under freeze-thaw cycles

To examine the creep behavior and degradation of stratified rock in cold areas, triaxial creep experiments and microscopic analyses were performed on layered red sandstone specimens under freeze-thaw (F-T) cycles. This study revealed the deterioration characteristics and damage mechanisms of red sandstone's creep behavior under the influence of F-T cycles and bedding inclination. The test results showed that: (1) The steady-state creep rates with bedding angles β=30°after 0, 40, 80, and 120F-T cycles were 0.0168 × 10−2·h−1, 0.0224 × 10−2·h−1, 0.0289 × 10−2·h−1, and 0.0368 × 10−2·h−1 respectively. The instantaneous deformation, creep deformation, and steady-state creep rates increased gradually with the increase of F-T cycles, while the long-term strength exhibited a decreasing trend. (2) After 40F-T cycles, the long-term strengths with bedding angles of 0°, 30°, 45°, 60° and 90° were 121.17 MPa, 65.47 MPa, 46.28 MPa, 77.64 MPa and 124.78 MPa, respectively. The bedding angle of 45° has the greatest influence on the triaxial creep properties of red sandstone, followed by the bedding angles of 30° and 60°, and the bedding angles of 0° and 90° have the least influence. (3) As the F-T cycles increases, the longitudinal wave velocity gradually decreases, and the pores and cracks on the sample surface continue to expand, leading to increased damage. The failure mode evolves from a single oblique shear plane to an “X”-shaped tensile splitting. Additionally, the bedding angle has a significant effect on the longitudinal wave velocity. As the bedding angle increases, the longitudinal wave velocity exhibits a “V”-shaped distribution, initially decreasing and then increasing. Based on the test results, a creep damage model of layered rock considering the influence of F-T cycles was established, and the rationality of the model was verified by test data. The research results can provide a scientific basis and technical reference for the long-term stability of layered rock engineering in cold regions.

Dynamic creep of Al2O3 whisker-reinforced ZrO2 ceramic composite

Previous studies on the creep behavior of ceramic materials were primarily conducted under static loads. However, the majority of applications for ceramic materials are subject to dynamic loads, and there is a paucity of research conducted in this area. In this work, we report for the first time the creep behavior of Al2O3 whisker-reinforced ZrO2 composites under dynamic pressure. The results showed that the sample crept under dynamic pressure produced higher creep rate and lower activation energy compared to static pressure. By analyzing the creep data and microstructures, we showed that the dynamic pressure can enhance dislocation motion and transform the creep mechanism from diffusion-controlled grain-boundary sliding to dislocation-controlled grain-boundary sliding. This work provides a foundation for subsequent detailed studies of the creep behavior of ceramic materials under dynamic pressure.

An Advanced Sine-Hyperbolic Creep-Damage Model Incorporating Threshold Strength

Abstract This study aims at improving the classic Sine-Hyperbolic (Sinh) creep-damage model to predict minimum-creep-strain-rate (MCSR), rupture, damage, and creep deformation. The Sinh model employs a continuum-damage-mechanics-based framework to model secondary and tertiary creep regimes. In Sinh, the creep strain and damage rate equations exhibit an implicit threshold stress that arises during numerical optimization. Herein, the Sinh model is modified to include an explicit threshold strength as a material property and the tensile strength. Threshold strength is defined as the lower limit for creep activation at a given temperature. Stresses are applied below the threshold, resulting in infinite life. The advanced Sinh offers several advantages including a physical significance of stress ratios, a closed-form solution, and adaptability in finite element analysis. Experimental creep data of 304SS at multiple isotherms are gathered. The advanced Sinh is calibrated to the MCSR and SR data of 304SS. The calibration of threshold strength follows a standard procedure from literature and is observed to be realistic for stainless steel at elevated temperatures. The MCSR and SR predictions illustrate the Sigmoidal bend and demonstrate zero creep rate and infinite life at or below threshold strength. The creep deformation and damage predictions exhibit agreement with experimental data. The advanced Sinh is validated by employing finite element simulation to ensure the applicability of the model across a range of applications. The advanced Sinh improved creep response prediction and added physical realism to the model?s framework

Low-frequency EIS interpretation with the potential to predict the durability of protective coatings

Obtaining impedance response with predictive value for coating durability is central to meeting today's protective coatings end-user requirements. Here we present a novel approach to interpreting the low-frequency impedance of industrial coatings that takes into account the relevance of the coating properties that determine their barrier and adhesion durability. Modern, high adhesion, low VOC polymer coatings utilize cross-linking chemistry with polar or hydrogen bonding materials, leading to the apparent paradox that coatings exhibit corrosion creep values that are very low and inversely related to the barrier effect derived from the EIS response. In practice, once the corrosion creep rate is negligible, the ability of a coating to act as a long-term effective barrier, especially at edges and welds, becomes a major concern, and the improvement in durability relies on the improvement of the barrier. In the present study, we investigated the barrier effect of conventional partial and full offshore coating systems with epoxy and epoxy mastic layers applied without and with zinc-rich or zinc phosphate primers and polyurethane topcoats. The panels were aged for two years in an atmospheric offshore-like conditions and subsequently exhibited defects due to inadequate coating thickness, number of layers, surface preparation and inadequate application practice. EIS measurements were performed on the panels in the laboratory in dry and wet state. EIS provided a quantitative rating of the barrier effect that can serve as a basis for informed upgrading of coating solutions, application practices or workmanship quality, particularly in structures with limited access where high durability is an imperative.

Dynamic Deformation in Nuclear Graphite and Underlying Mechanisms.

Time-dependent deformation in nuclear graphite is influenced by the creation and migration of radiation-induced defects in the reactor environment. This study investigates the role of pre-existing defects such as point defect clusters and Mrozowski cracks in nuclear graphite IG-110. Separate specimens were irradiated with a 2.8 MeV Au2+ beam with a fluence of 4.38 × 1014 cm-2 and an 8 MeV C2+ beam with a fluence of 1.24 × 1016 cm-2. Microscopic specimens were either mechanically loaded inside a transmission electron microscope (TEM) or subjected to ex situ indentation-based creep loading. In situ TEM tests showed significant plasticity in regions highly localized around the Mrozowski cracks, resembling slip or ripplocation bands. Slip bands were also seen near regions without pre-existing defects but at very high stresses. Ex situ self-ion irradiation embrittled the specimens and decreased the creep displacement and rate, while heavy ion irradiation resulted in the opposite behavior. We hypothesize that the large-sized gold ions (compared to the carbon atoms) induced interplanar swelling as well as cross-plane channels for increased defect mobility. These findings illustrate the role of pre-existing defects in the dynamic relaxation of stresses during irradiation and the need for more studies into the radiation environment's impact on the mechanical response of nuclear graphite.

Synergy of γ′ phase, MC carbide and grain boundary phase on creep behavior for nickel-based superalloy K439B

The synergy of γ′ phase, MC carbide and grain boundary phase on 815 °C/379 MPa creep behavior for nickel-based superalloy K439B was investigated by adjusting the time and temperature of the first-stage aging treatment. Increasing aging time from 4 h to 6 h, the total creep life is reduced by 35.8% due to the increased bimodal γ′ phase size. The bimodal γ′ phase transforms into small unimodal γ′ phase when increasing aging temperature from 1000 °C to 1080 °C. In addition, the content of M23C6 carbide increases, and the total creep life is increased by about 1.3 times. Small-size γ′ phase with bimodal distribution redissolves into γ matrix during creep deformation. Dislocations pile up at the γ/γ′ interface, and partial dislocations enter into large-size γ′ phase, mainly forming isolated parallel stacking faults. By comparison, the crossed stacking faults within small unimodal γʹ phase form Lomer-Cottrell locks, APB coupled dislocation pairs shear into γʹ phase, and more granular M23C6 carbide precipitates at the grain boundary, which further decreases the minimum steady creep rate and improves the creep life. At the beginning of creep deformation, MC carbide prevents the movement of dislocations. MC carbide formed at grain boundaries can delay crack propagation to a certain extent. MC carbide debonds from γ matrix subsequently due to the dislocation accumulation and higher interface energy, which provides a pathway for crack initiation and propagation. Moreover, the fragmentation and degeneration inside MC carbide promote crack initiation.

Achieving high mechanical and corrosion properties of AA2050 Al-Li alloy: The creep aging under plastic loading

The influences of elastic/plastic loading (100–220 MPa) on the creep behavior, mechanical properties, and corrosion behavior of creep-aged AA2050 alloys were investigated. The results show that the creep rate increased from 0.35 % to 0.61 % with the increase of stress from 100 MPa to 220 MPa. The creep rate was increased rapidly under plastic loading (220 MPa) due to the increased dislocation density. Meanwhile, the plastic loading shortened the peak-aged time of creep-aged alloys and achieved outstanding strength (UTS=534 MPa, YS=496 MPa, peak aged), which increased by 33 MPa and 32 MPa compared with elastic loading, respectively. The strength enhancement was attributed to the increase in dislocation density, weak oriented precipitation effect, and dense precipitation of T1 phases. Additionally, compared with elastic loading, GBPs under plastic loading coarsened and distributed discretely, their elements content distributed evenly, and the Cu content increased. Therefore, the intergranular corrosion (IGC) depth and stress corrosion cracking (SCC) susceptibility index (ISSRT) decreased from 174 μm, and 8.7 % to 121 μm, and 5.9 %, respectively. These findings pave a way in breaking curvature limit of creep aging technology.

Stress and temperature dependence of irradiation creep in zircaloy-4 studied using proton irradiation

This paper describes a series of experiments conducted to investigate the in-situ irradiation creep behavior of Zircaloy-4 using proton irradiations as a surrogate to neutrons. The first series of experiments investigated the impact of the initial irradiation-induced defect evolution during the 0 – 0.1 dpa regime on the subsequent in-situ steady-state behavior derived from experimentation. These experiments were conducted at a constant applied load of 85 MPa, a constant damage rate of 1.58 × 10−6 dpa/s, and were repeated at both 250 °C and 350 °C. We also examined the use of a ‘conditioning-irradiation’ step prior to the creep tests on the results derived from subsequent in-situ proton irradiation creep experiments. By extension, we aimed to further develop and refine optimum testing procedures when using proton irradiations to investigate the in-situ creep behavior of nuclear materials. The second series of in-situ proton irradiation experiments were conducted on two Recrystallized (RX) Zircaloy-4 samples in order to investigate the temperature and stress dependence of irradiation creep. One sample was held at a constant load while the temperature was varied in the range of 275 – 350 °C, and the other was held at a constant temperature while stress was varied in the range of 65 – 105 MPa. The associated strains and creep rates were measured at each interval and used to determine an activation temperature of 5000 ± 1700 K and a stress sensitivity exponent of 4.3 ± 0.8 for RX Zr-4 over the given temperature and stress ranges. A discussion of potential deformation mechanisms based on competition between bulk diffusion through the lattice and point defect diffusion enabling dislocation climb and glide is given: the relatively high stress dependence suggested the latter is more likely however further investigations will be required to improve the mechanistic understanding. The results presented in this manuscript, including activation temperature, stress sensitivity, and associated creep rates, determined through proton irradiation investigations are closely comparable to those determined from neutron irradiation experiments found in the literature for similar zirconium alloys at similar temperatures and stresses. Coupled with the primary-secondary creep behavior investigations presented, this demonstrates the usefulness of this approach to estimate neutron-irradiation equivalent creep behavior using in-situ proton irradiation.

Biomechanical changes of tree shrew posterior sclera during experimental myopia, after retrobulbar vehicle injections, and crosslinking using genipin

Myopia is a common ocular condition characterized by biomechanical weakening revealed by increasing creep rate, cyclic softening scleral thinning, change of collagen fibril crimping, and excessive elongation of the posterior sclera resulting in blurred vision. Animal studies support scleral crosslinking as a potential treatment for myopia control by strengthening the weakened sclera and slowing scleral expansion. While multiple studies investigated aspects of the biomechanical weakening and strengthening effects in myopia and after scleral crosslinking, a comprehensive analysis of the underlying mechanical changes including the effect of vehicle injections is still missing. The purpose of this study was to provide a comprehensive analysis of biomechanical changes by scleral inflation testing in experimental myopia, after retrobulbar vehicle injections and scleral crosslinking using genipin in tree shrews. Our results suggest that biomechanical weakening in myopia involves an increased creep rate and higher strain levels at which collagen fibers uncrimp. Both weakening effects were reduced after scleral crosslinking using genipin at doses that were effective in slowing myopia progression. Vehicle injections increased mechanical hysteresis and had a small but significant effect on slowing myopia progression. Also, our results support scleral crosslinking as a potential treatment modality that can prevent or counteract scleral weakening effects in myopia. Furthermore, vehicle solutions may cause independent biomechanical effects, which should be considered when developing and evaluating scleral crosslinking procedures.

Rheological and Aging Properties of Nano-Clay/SBS Composite-Modified Asphalt.

Nano-organic montmorillonite (OMMT) not only inhibits the harmful asphalt fume generation during the production and construction processes of asphalt mixtures but also effectively improves the performance of asphalt pavements. In order to prepare asphalt materials with smoke suppression effects and good road performance, this study selects nano-OMMT and SBS-modified asphalt for composite modification of asphalt mixtures and systematically investigates its road performance. Through the temperature sweep test, the frequency sweep test, the multiple stress creep recovery (MSCR) test, the bending beam rheometer (BBR) test, and the atomic force microscope (AFM) test, the high-temperature rheological properties, low-temperature rheological properties, high-temperature properties and aging resistance of the modified asphalt are studied. The research findings indicate that OMMT can effectively reduce the sensitivity of modified asphalt to load stress and improve its high-temperature rheological properties. SBS-modified asphalt shows increased creep stiffness and a decreased creep rate after OMMT modification, resulting in reduced flexibility and decreased low-temperature crack resistance. After short-term and long-term aging, the complex modulus aging index of OMMT/SBS composite-modified asphalt is lower than that of SBS-modified asphalt, and the phase angle aging index is higher than that of SBS-modified asphalt, demonstrating that OMMT enhances the aging resistance of SBS-modified asphalt. OMMT inhibits oxidation reactions in the asphalt matrix, reducing the formation of C=O and S=O bonds, thereby slowing down the aging process of modified asphalt and improving its aging resistance.

Enhancement of sintering and mechanical properties of alumina-rich Al2O3-MgO-CaO refractory composite by doping La2O3

Ceramics or refractories prepared in the Al2O3-rich corner of the Al2O3-MgO-CaO system show excellent high-temperature mechanical properties and chemical stability because of the presence of spinel (MgAl2O4) and calcium hexaluminate (CaAl12O19). However, the densification of these two crystals usually requires high firing temperatures due to their poor sinterability. To address this issue, La2O3-doped MgAl2O4-CaAl4O7-CaAl12O19 refractory composites were designed, and the influence of the doping level on the densification, microstructure, and mechanical properties of the composite was investigated. It was found that the doped La3+ was predominantly dissolved in the CA6 grains by replacing Ca2+, forming uniform solid solutions regardless of doping concentration. This reaction significantly accelerates ion diffusion and CA2 grain growth. Besides, it reduces the aspect ratio of CA6 crystals, weakening the negative effect of the elongated grains on mass transfer and sintering. As a result, the relative density increases from 79.5 % to 95.1 % after sintering at 1600 °C with doping only 0.5 wt% La2O3 into the composite, producing a uniform and dense microstructure with regular angular grains. The above effects result in a significant improvement in flexural strength and fracture toughness (increasing by 61 % and 57 %, respectively). Moreover, the La2O3-doped refractory composite achieves a decline of the high-temperature creep rate by one order of magnitude at 1600 °C.

True triaxial shear creep behaviors of sandstone under constant normal load and constant normal stiffness conditions

The long-term stability of rocks is crucial for ensuring safety in deep engineering, where the prolonged influence of shear loading is a key factor in delayed engineering disasters. Despite its significance, research on time-dependent shear failures under true triaxial stress to reflect in situ stress conditions remains limited. This study presents laboratory shear creep measurements on intact sandstone samples under constant normal load (CNL) and constant normal stiffness (CNS) conditions, which are typical of shallow and deep engineering cases, respectively. Our investigation focuses on the effects of various lateral stresses and boundary conditions on the mechanical behaviors and failure modes of the rock samples. Results indicate that lateral stress significantly reduces shear creep deformation and decreases creep rates. Without lateral stress constraints, the samples are prone to lateral tensile fractures leading to macroscopic spalling, likely due to "shear-induced tensile" stress. This failure behavior is mitigated under lateral stress constraints. Additionally, compared to CNL condition, samples under CNS condition demonstrate enhanced long-term shear resistance, reduced shear creep rates, and rougher shear failure surfaces. These findings suggest the need to improve our understanding of rock mass stability and to develop effective disaster prevention and mitigation strategies in engineering applications.

Rapid assessment of the creep rupture life of metals: A model enabling experimental design

Prediction of the creep rupture life of engineering metals is critical for qualification and design of new materials. The use of long-term creep tests and the need to quantify the performance variability in a priori similar systems hinder the rapid creep assessment of a given material. Therefore, it is essential to develop methods that can extrapolate the long-term performance of alloys and the associated variability from short-term experiments. To this end, this study introduces a new model which enables the estimation of the rupture life of a material for a given stress and temperature. This model relies on two components. First, a new relation for the minimum creep rate (MCR) of materials is introduced. It includes a stress dependent stress exponent allowing the model to capture the variation of MCR across a wide range of temperatures and stresses. Second, employing the Monkman-Grant (MG) law, we establish a relation between stress, temperature and creep rupture life. Together, these two elements yield a new closed-form mathematical expression for the Larson Miller parameter as a function of stress and temperature. This expression captures the creep rupture time for many metals (Gr91, Copper, Gr122 and 347H) and compares favorably with alternate empirical approaches. The model is then used to assess the minimum duration of creep rates necessary to qualify the material up to 100000h. It is found that depending on the material system, creep tests as few as five limited to 5000 h for steels (Gr91, Gr122, 347H) and 100 h for copper are sufficient to model creep lifetimes. Finally, using a Bayesian inference-based approach to calibrate the model, we demonstrate that variability in rupture life can be captured via the quantification of the uncertainty in the model parameters and extrapolated from a limited number of short to moderately short creep tests; thereby paving the way for accelerated creep testing.

Fractional-order burgers model for coral concrete creep

With the rapid development of marine engineering construction, coral aggregate has been widely applied in practical engineering. Its creep characteristics must be emphasized, but only a few experimental studies have been conducted, and theoretical research has not yet been reported. In this study, based on the traditional Burgers rheological model and using the fractional order software components Able dashpot, constructs a fractional order creep model for coral concrete and provides a calculation method. Comparison shows that the traditional Burgers rheological model cannot adjust the creep rate and development degree in calculations, resulting in a large deviation between its predicted results and experimental values. However, the fractional order model established in this paper aligns with the creep development law of coral concrete, and its calculated values match well with experimental values, making it suitable for predicting the creep characteristics of coral concrete under different water-cement ratios. Sensitivity analysis of the fractional order can achieve effective control over the prediction of creep development in coral concrete in practical engineering. The fractional order creep model established in this paper can provide a basis for predicting and evaluating the long-term performance of coral concrete in practical engineering.

Creep condition-oriented design of molybdenum alloys with La2O3 addition assisted by microstructure-based crystal plasticity modeling

Molybdenum (Mo) alloys are essential for applications requiring outstanding mechanical properties at high temperatures across various industrial sectors. Understanding and predicting the creep properties of Mo alloys is crucial for service safety and the design of new materials. This study introduces a physics-based crystallographic creep model dedicated to the characteristic hierarchical microstructure of Mo–La2O3 alloys. By sourcing most parameters from existing literature and calibrating others within recommended ranges, the model efficiently predicts creep behavior beyond its initial calibration scope. Through the integration of microstructure descriptors, we systematically explored the impact of different microstructural features on the creep behavior and identified the underlying mechanisms. This analysis yielded two pivotal concepts: the minimum acceptable grain size and the necessary nanoparticle number density. These metrics, readily obtainable from the model, quantify the requisite grain size and nanoparticle content to achieve the target steady-state creep rates for operational demands, thus providing essential insights for the creep condition-oriented design of Mo–La2O3 alloys. The model is also expected to be adaptable for developing other Mo alloys reinforced by second phase particles, aimed at achieving desired creep properties under specified conditions, assuming that relevant parameters are accessible through literature or lower-scale simulations.

Increasing heat resistance of a Mg-Sm-Zn alloy via minor gadolinium addition

The addition of minor gadolinium (Gd) into Mg-4Sm-0.6Zn-0.4Zr alloy significantly enhances high-temperature strength and creep resistance, such as a decrease in the minimum creep rate by approximately five times and an increase in the yield strength by around 40 MPa at 200 °C. The presence of Gd results in the co-precipitation of both prismatic β-type and basal γ-type phases during creep, whereas only the basal γ-type phase is present in the Gd-free alloy. The prismatic β-type and basal γ-type phases are oriented perpendicular to each other in space, creating a closed configuration that effectively blocks dislocation motions compared to single basal γ-type precipitates. Therefore, the improved creep resistance in the Gd-enriched alloy is mainly attributed to the co-precipitation of prismatic β-type and γ-type precipitates during creep. Furthermore, rare earth (RE) atoms inherently provide stable solute hardening at high temperatures, which contributes to the increased high-temperature strength. The addition of Gd also enhances grain boundary stability by promoting the formation of more Mg3RE phases, thereby further enhancing the creep strength. These findings offer insights into the development of highly creep-resistant Mg alloys with low RE concentrations.

Shallow Creep on the Laohushan Segment of the Haiyuan Fault, Northeastern Tibetan Plateau, Detected With Dense Near‐Field GPS Measurements

AbstractWhile shallow creep along the Haiyuan fault is a key element in estimating earthquake potential, both the creep rate and spatial distribution inferred from InSAR and repeating earthquakes are still controversial. In this study, we resolve two potentially separated creeping patches along the Laohushan fault (LHSF) based on dense near‐field GPS measurements of 39 stations. The largest creeping patch, which extends ∼20 km along‐strike and ∼9 km down‐dip with a slip rate of 4.2 mm/yr, spatially correlates with seismicity, especially repeating earthquakes. The locked segment is capable of producing an earthquake of Mw 7.3 ± 0.1, with moment rate of (1.08 ± 0.39) × 1017 N⋅m/yr, possibly following the cycle since the 1092 M8 event. The lack of GPS measurements in the near‐field makes it unclear whether the 8 km section between these two patches is slowly creeping below detection threshold or has relocked due to change in environmental condition.

A novel method for investigating ice-substrate interfacial rheology and long-term adfreeze strength through loading-unloading creep test

Ice cementation and ice-substrate adfreeze force are the primary contributors to the high bearing capacity of pile foundations in cold regions and the stability of frozen walls in areas subjected to artificial freezing. Given the significant temperature sensitivity of ice’s shear rheology, engineering structures in ice or ice-rich soils continue to deform even under constant external loads. A thorough understanding of shear creep and the long-term adfreeze force at the ice-substrate interface is essential for predicting the continuous deformation of these structures. However, research into the shear creep behavior at frozen interfaces has historically been constrained by the precision of temperature control in experimental settings and the complexity of load paths in shear testing devices. In this study, a temperature- and stress-control device for interface shear creep is assembled firstly, and multilevel loading-unloading creep tests on steel pipes embedded in layered frozen ice were conducted. Through the decoupling of deformation progression, the viscoelastic and viscoplastic shear behaviors at the steel-ice interface under various temperatures and shear stresses were characterized, the principle of sustainable interfacial shear creep along with its underlying physical mechanism were proposed. Subsequently, with the aid of a modified nonlinear Burger model, various interfacial shear creep parameters were derived. Results reveal that the interfacial generalized shear modulus continuously improves but with a gradually weakening degree until a point of accelerating creep is reached. Additionally, the long-term adfreeze force is found to be less than half of the short-term strength, which significantly decreases as the temperature approaches the water phase transition zone. Interestingly, the stress exponent associated with the interfacial steady creep rate is considerably smaller than that predicted by Glen’s law. This research provides a theoretical basis instrumental in the engineering design in cold regions and those structures employing artificial freezing techniques.

Using rheology to study the synergistic effect of anti-aging modifier and rejuvenator on aged asphalt binder

A composite anti-aging rejuvenator for road asphalt was studied and prepared. Asphalt samples with different aging degrees and modifier dosages were prepared by RTFOT(rolling thin film oven) and PAV(pressure aging vessle)， and the viscoelastic, high temperature, low temperature and fatigue properties of the modified asphalt were comprehensively characterised based on their rheological properties. The test results showed that the composite anti-aging rejuvenator improved the fatigue performance and low temperature performance of aging asphalt. Among them, the creep rate m value at −18°C was recovered to 99.2 % of the unaged level, and the G-R(Glover-Rowe) parameter was reduced to more than 90 %. After long term aging of the composite anti-aging reclaimed mixtures were still able to maintain the water stability and low temperature performance higher than the level required by the specification. The paper found the better effect of adding same ratio of rejuvenator and anti-aging agent to aging asphalt. The reason was that the same ratio of rejuvenator and anti-aging agent could have synergistic effect and enhance each other. This paper verified the road value of the composite anti-aging rejuvenator from asphalt and asphalt mixtures, which provides technical support and reference for the promotion of old pavement reclamation and long-life pavement.