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This study focuses on the rheological behavior of a cellulose nanocrystal gel. This system [5 wt. % cellulose nanocrystal (CNC) + 20 mM NaCl] is proved to be thixotropic, and the detected shear force tightly depends on the growth and break-up of the aggregates of CNC rods. From strain-controlled experiments, a nonmonotonic steady-state flow curve with a minimum stress value of ≈33 Pa is found, and the negative slope of stress versus shear rate suggests the existence of shear bands. From stress-controlled experiments (creep), the "static yield stress" is determined to be 67.5 ± 2.5 Pa. This difference proves that the local minimum stress of the flow curve does not coincide with the "static yield stress" determined by creep tests. However, this minimum stress can maintain flow provided that the material is already in a yielded state. At nominal shear rates below about 100 s−1, shearing is suggested to be localized in a shear band rather than over the whole material. The "dynamic yield stress" is found as "the minimum stress to maintain flow," or the onset of shear banding. Moreover, wall slip also occurs at low nominal shear rates which is related to the interaction between the dynamic microstructure of the CNC gel and the wall: it is hypothesized that the low shear rates allow the CNC aggregates to extensively grow and, thus, the oversized CNC aggregates detach from the asperities of the wall. Our finding of the robust connection between yielding, thixotropy, wall slip, and shear banding shall shed new light on the nature of the nonmonotonic flow curves of yield stress and thixotropic materials. [ABSTRACT FROM AUTHOR]

This review paper provides an exploration of various facets of creep behaviour in adhesives and adhesive joints, encompassing experimental procedures, prediction models, influential parameters and strategies to enhance resistance. The discussion extends to the interplay between fatigue and creep, emphasising recent advances over the last two decades. While avoiding redundancy with prior work on temperature and moisture degradation, the paper articulates connections between topics for a better understanding. A critical examination of load levels reveals that small variations significantly impact the creep life of adhesive joints, particularly prominent with epoxy adhesives. The adhesive type, joint geometry and substrate material are scrutinised, revealing distinct impacts on creep behaviour. The study underscores the critical role of adhesive thickness and overlap length, emphasising their relevance in determining the time to failure in bonded joints under creep conditions. Notably, the substrate material's role is highlighted. As the review delves into unexplored dimensions, it calls for further research to bridge existing gaps and refine our understanding of tertiary creep and time until failure. [ABSTRACT FROM AUTHOR]

To investigate the time-dependent characteristics of jointed rock masses, a series of single-step true triaxial creep tests were conducted on natural jointed granite samples under different dip angles conditions. The results showed that the time-dependent failure of jointed granite behave as two different forms, namely, stress-controlled and stress-structure-controlled failure. When the dip angle of joint is less than 70° or greater than 77°, stress-controlled failure was the predominate mode. Otherwise, stress-structure-controlled failure occurred. There are similarities and differences in the evolution mechanisms of these two types of time-dependent failure. Similarly, the acoustic emission (AE) count rate demonstrated multiple peaks in both types of time-dependent failure processes. Differently, for stress-controlled failure, tensile microcracks and large-scale shear cracks develop alternately until the ultimate failure is reached, but for stress-structure-controlled failure, tensile cracks are dominant in the early stage and followed by plenty of shear cracks in the later stage. [ABSTRACT FROM AUTHOR]

Characterizing layered rock's anisotropic creep is crucial for assessing the potential effect of anisotropic creep on the long-term stability of engineering structures. This study establishes a new anisotropic viscoelastic-plastic model involving the nonlinear creep characteristics of the rock matrix and the bedding plane, which can describe the three-stage anisotropic creep characteristics of layered rock. In the anisotropic creep model, the nonlinear Burgers model describes the creep features of the bedding planes, and the nonlinear Nishihara model describes the rock matrix's creep features are coupled in series. To verify the rationality and accuracy of the newly proposed creep model, a series of uniaxial compression creep tests of chlorite schist with different inclination angles are conducted. On the one hand, the experimental results show that there is a geometrical similarity of the creep curves for the samples with inclination angles of 0°, 50°, and 90°, exhibiting apparent instantaneous strain, attenuation creep, stability creep, and accelerated creep, which shows the bedding planes with different inclination angles do not affect the creep curves' shape, mainly affecting the magnitude of instantaneous strain and creep strain. The long-term strengths of three different types of inclined rock specimens are 0.67–0.88 times the corresponding uniaxial compressive strengths. On the other hand, the new creep model can agree well with the experimental results, which proves that it can describe the anisotropic creep characteristics of layered rock mass well. Further, the sensitivity analysis results of mechanical parameters in the creep model show that the failure modes of layered rock masses are controlled by inclination angle within the range of β 1 ∼ β 2 . Moreover, the accelerated creep time of rock specimens with different inclination angles increases with the increment of deviatoric stress, n1, n3, and creep rate, contrary to the law of confining pressure and parameters n2, n4. Highlights: A three-dimensional anisotropic creep model is established considering the nonlinear creep characteristics of the rock matrix and bedding planes. The creep test results show that the bedding planes with different inclination angles do not affect the creep curves' shape, mainly affecting the magnitude of instantaneous strain and creep strain. [ABSTRACT FROM AUTHOR]

In subterranean potash mines utilizing the room-and-pillar mining method, maintaining the long-term stability of carnallite pillars is imperative for the safety and ongoing viability of operations. This study undertakes uniaxial compression creep tests on carnallite samples sourced from the Dongtai Potash and Magnesium Salt Mine in Laos. The durability of carnallite pillars is evaluated using an advanced Burgers creep model combined with Flac3D numerical simulations. Results indicate that the creep strength of carnallite is approximately 60%–70% of its immediate strength, demonstrating significant creep behavior. The refined Burgers model provides an accurate representation of the carnallite’s creep characteristics. Post-excavation, the internal compressive stress within the pillars progressively increases, registering an approximate rise of 1 MPa, and stabilizes under pressure after one year. After three years of continuous observation through creep tests and Flac3D simulations, the maximum deformations detected in the roof and floor of the mining house, as well as the adjacent rock masses, were 60mm and 20mm, respectively, indicating minimal overall deformation. The width of the plastic zone within the pillars exhibits time-dependent growth, with rapid expansion occurring in the internal plastic zone and a significant deformation rate within the first six months post-excavation. To ensure the long-term stability of the mining pillars and voids, it is recommended that backfilling operations be conducted within six months following the excavation.

The paper presents uniaxial creep tests conducted on Inconel 718 superalloy, reporting and describing the results obtained. The creep strain curves have been examined in different scenarios: by varying the initial applied stress, by varying the initial test temperature, and by considering the orientation of the specimens with respect to the direction of the material processing. Finally, ductility and deformation accumulation rate have been evaluated to highlight the effect of the precipitation anisotropy on the creep behaviour. Given the complexity of the creep phenomenon, each phase of the creep strain curves of Inconel 718 has been analysed independently, using constitutive models taken from the literature that allow to describe the phenomenon in pure metals and in some alloys. [ABSTRACT FROM AUTHOR]

An understanding of the creep behavior of clayey rocks is considered fundamental for further development in the fields of nuclear waste underground disposal, underground mine design, strata control, and many other geological phenomena occurring in the earth's crust. In this research, we performed a series of long-term triaxial compressive tests on a typical clayey rock, which confirmed its high creep potential beyond the creep threshold. Further analysis of the creep mechanism of this clayey rock indicated that two effects—strengthening and damage—are accompanied by the creep process. Additionally, based on the overstress theory and Drucker–Prager cap model, we developed a novel constitutive model considering two creep reference surfaces—cohesion and consolidation. Meanwhile, laws to reflect the strength and damage effect during creep were established and applied to the above constitutive model. Finally, the above theoretical studies were implemented in the finite element method software ABAQUS FEA using the subroutines CREEP and USDFLD. Some theory parameters were verified through back analysis. A comparison between the experimental results and numerical simulations confirmed the superiority of the established theoretical model. Highlights: Clayey rock exhibits high creep potential beyond the creep threshold. Two effects—strengthening and damage—are accompanied by the creep process. A novel creep constitutive model was established. Strengthening and damage laws during creep were developed. Model numerical implementation and parameters determination. [ABSTRACT FROM AUTHOR]

Reinforcing the materials used in 3D printing with different fillers like short and continuous fibers or micro and nanoparticles is a common way of increasing their mechanical properties. In real applications, parts manufactured from reinforced polymers may be exposed to loadings of various rates. However, there is relatively little data on the rate-depended behavior of 3D printed materials and components available in the literature. The present study aims to provide some basic information about the mechanical behavior of PA12 polyamide and its composites manufactured by filament deposition technology. 3D printed specimens were tested under the monotonic tensile loading of various strain rates and subjected to creep and creep recovery tests. The results showed an important strain rate effect in the case of all tested materials. Reinforced materials exhibited improved mechanical properties. The highest tensile strength and creep resistance were achieved for the carbon fiber reinforced material, in the case of which the damage mechanism consisted of carbon fibers breaking before pulling out from the polymer matrix.

This paper summarizes preliminary results of an experimental investigation on the creep behavior of transverse welded lap joints at elevated temperatures. The aim of this study is to quantify the time-to-failure for transverse welded lap joints exposed to high temperatures. In this study, two series of experiments were conducted. In the first series, the specimens were heated to target temperatures and then loaded to failure to estimate the peak load P that the specimens could sustain at each target temperature. In the second series, after the specimens were heated to the test temperatures, fractions of the peak load P were applied rapidly and kept constant throughout the test. Through the combination of these two series of experiments, the effect of load and temperature on the time-dependent or creep behavior of transverse welded lap joints was studied. The experimental results show that, for temperatures greater than 450°C, transverse welded lap joints undergo excessive deformation due to creep, and that creep effect becomes more significant as load and temperature increase. [ABSTRACT FROM AUTHOR]

Creep and shrinkage prediction models for concrete In autumn 2020, the revision of EN 1992‐1‐1:2004 (Eurocode 2) was completed, resulting in the current draft prEN 1992‐1‐1:2021. It provides practice with numerous improved and new design concepts. This also applies to the models for shrinkage and creep of structural concrete, some of which have undergone significant changes. This three‐part paper (Part 1 Shrinkage, Part 2a and 2b Creep) presents the new models for predicting the deformation behaviour of concrete. It also highlights the background that led to the development of the improved approaches. The Parts 1 and 2a have already been published (Beton‐ und Stahlbetonbau 116 (2021), issues 1 and 9). The article at hand (Part 2b) continues and concludes the previous treatment of concrete creep. First of all, the functions for describing the time development of creep and the implications associated with them are presented. Then, various aspects of linear and non‐linear creep are examined. The focus of the article is on the new prediction model of prEN 1992‐1‐1:2021, which is presented and justified. Statistical considerations on the reliability of the new model and the presentation of a concept for the inclusion of laboratory test data to improve the prediction of the model conclude this article and the entire paper. [ABSTRACT FROM AUTHOR]

Creep and shrinkage prediction models for concrete In autumn 2020, the revision of EN 1992‐1‐1:2004 (Eurocode 2) was completed, resulting in the draft prEN 1992‐1‐1:2020. It provides practice with numerous improved and new design concepts. This also applies to the models for shrinkage and creep of structural concrete, some of which have undergone significant changes. This three‐part paper (Part 1 Shrinkage, Part 2a and 2b Creep) presents the new models for predicting the deformation behaviour of concrete. It also highlights the background that led to the development of the improved approaches. Part 1 has already been published (Beton‐ und Stahlbetonbau 116 (2021), issue 1). The article at hand (Part 2a) deals with the creep of concrete. In an overview, the components of creep, their characteristics and influencing parameters as well as the corresponding constitutive relationships are first presented. They are crucial for understanding the creep models. Then, the normative developments that have led to the creep model in DIN EN 1992‐1‐1:2011 valid today in the year 2021 are shown. The focus is on the analysis of the reliability and accuracy of this model. It revealed certain deficiencies, which were the reason for corrections and further developments being included in prEN 1992‐1‐1:2020. The new prediction model is presented and justified in Part 2b of this paper. Statistical considerations on the reliability of the new model and the presentation of a concept for the inclusion of laboratory test data to improve the prediction of the model conclude the entire paper. [ABSTRACT FROM AUTHOR]

• The effect of loading angle ω on the time-dependent deformation of natural jointed granite subjected to true triaxial stresses was investigated. • The unfavorable combination relationship between joint orientations and true triaxial stresses was investigated. • The stress-structure-controlled time-dependent failure enters the stage dominated by shear cracks earlier than stress-controlled. • Joint orientations most likely to induce the time-dependent disaster in deep tunnel were predicted according to the true triaxial tests of jointed granite. Joints are an important part of rock masses and the spatial relationship between joint orientation and in situ stress (or tunnel axis) has a significant impact on the deformation, strength, and failure behavior of the surrounding rock. To study the influence of joint orientation on creep characteristics of deep hard rock, the true triaxial creep tests were performed in the laboratory on natural jointed granite under different loading angles ω (defined as the angle between the strike of the joint plane and σ 2 -direction) conditions. The test results show that ω has a significant effect on the time-dependent deformation and failure characteristics of the jointed rock. As ω increases, there is a decrease in creep deformation, steady creep rate in the σ 3 -direction, and value of the DI index (used to evaluate the difference in the time-dependent deformation in the σ 2 - and σ 3 -directions). Stress-structure-controlled failure (sliding along the joint plane) occurs when ω ≤ 30°. However, when ω > 30°, the failure of the jointed granite is not affected by joint and stress-controlled failure occurs. The stress-structure-controlled time-dependent failure evolution enters a stage that is dominated by shear cracks earlier than stress-controlled failure according to AE results. In addition, the time-dependent failure went through stages of microcracks initiation and interaction, stable crack growth and unstable crack propagation. And when the time-dependent failure evolution enters the unstable crack propagation stage, the nature of the cracks changed from tensile-dominated to shear-dominated. [ABSTRACT FROM AUTHOR]

To optimize the properties of asphalt mixtures and make full use of waste rubber tires, diatomite and crumb rubber particles were applied to reinforce the asphalt mixtures in this study. The rutting tests, the three-point bending tests, the freeze-thaw splitting tests, and the uniaxial compression creep tests were performed to analyze the effects of asphalt types and aggregate gradation on the pavement properties of diatomite and crumb rubber particles reinforced asphalt mixtures (DRPAM). Subsequently, the creep and relaxation characteristics of DRPAM were analyzed by the Burgers model, the modified Burgers model, the second-order extensive Maxwell model, and the Scott–Blair model. The results show that rubber particles and diatomite can reinforce the high temperature, low temperature, and viscoelastic properties of asphalt mixtures, although the improvement effect is weaker than styrene-butadiene-styrene (SBS). Consequently, it is concluded that rubber particle and diatomite compound modified asphalt mixture with suspension dense gradation and SBS binder will have better performance. [ABSTRACT FROM AUTHOR]

Novel proof of serviceability of asphalt inner seals in dams For embankment dams, proofs of safety must be provided according to the current standard DIN 19700‐11. This also includes the serviceability check for asphalt inner seals (AIS). Thereafter, only limited deformations may occur, so that there may be no cracking in the asphaltic material. For this type of seal there is currently no generally binding and widely practiced calculation method. Based on the material behaviour of the asphaltic concrete, a sufficient main criterion is the adherence to defined limiting main stress conditions, which must not be undercut. As an additional criterion, defined limit deformations of the volume change must be observed. Using a simplified material model for the asphaltic concrete the novel proof of serviceability is based on an adequate finite‐element‐model for a dam with AIS considering relevant load cases. [ABSTRACT FROM AUTHOR]

• The ratio of long-term strength to uniaxial compressive strength of rock is in stable. • The rock masses exhibit more shear failures under creep. • A unified creep model can be used for the pre-flawed rock masses and intact rock. • The creep model of fractured rock masses can be derived from the intact rock. A number of pre-flawed specimens made of sandstone-like material with four different numbers and five different angles were prepared and tested in three various loading paths to investigate the time-dependent mechanical behaviors. It was determined that the deformations and strengths increase and decrease with increasing flaw number and decreasing flaw angle, respectively. The ratio of the long-term strength to the uniaxial compressive strength of specimens with the same pre-existing flaws varies within a small range (0.637–0.729). The specimens in the creep tests exhibited more shear failures than those in the uniaxial compression tests. A modified Burgers model was then developed. By using different parameter values, it can well describe the entire creep phases of all the pre-flawed and intact specimens, which is in accordance with the principles of damage mechanics. In view of this, pre-existing flaws were regarded as a type of damage to the intact material, and a damage creep model was developed that can derive the creep curves of fractured materials from those of the intact material. This idea provides a reference for the study of the damage creep model of fractured rock masses. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer bars, as an alternative for steel bars, are widely used to overcome the corrosion problem especially under severe environmental conditions. In the present research, the soil nail system was physically modeled in the laboratory. Since bond stress and creep displacements of the GFRP nails are not well understood yet, the nail–grout and grout–soil interfaces were experimentally investigated simultaneously in a soil box. In the first step, the bond stress of the GFRP soil nails was studied through pullout tests. Subsequently, experimental creep tests were carried out under sustained loads which were equal to a fraction of ultimate pullout load. Furthermore, the effect of soil density and surcharge pressure on bond stress of both interfaces was evaluated. In addition, the ultimate bond strength of the nail–grout interface was measured by physical tests, and the grout could not move. Finally, the dependency of creep displacements on different load ratios and variable surcharge pressures was explored. The results clearly showed that the ultimate pullout load of the steel nail–grout interface with no surrounding soil was more than that of GFRP. The grout–soil bond stress was affected by the variation of soil density more than nail–grout and an almost linear relationship between soil unit weight and bond stress was observed at both the interfaces. Nevertheless, the increment rate of bond stress decreased with the growth in surcharge pressure at both interfaces. Moreover, creep tests displayed an interdependency of creep displacements at the interfaces and rate of reduction of creep displacements with the decrease in the surcharge pressure increment. [ABSTRACT FROM AUTHOR]

Soft and hard interbedded rocks show obvious time-dependent deformation after deep tunnel excavations, and it is therefore necessary to research the mechanical behavior of the layered rock. However, it is hard to obtain ideal transversely isotropic rocks in fields, so rock-like specimens were poured by using artificial materials. Cyclic loading–unloading creep experiments were performed on the artificial layered cemented specimens with various layer angles (0°, 30°, 60° and 90°) at a 20 MPa confinement. Time-independent deformations and time-dependent deformations of the rock-like specimens were distinguished to investigate the visco-elasto-plastic deformation characteristics. Instantaneous elastic strain and instantaneous plastic strain had linear correlations with stress ratio, whereas creep strain, including visco-elastic strain and visco-plastic strain, increased nonlinearly with an increasing stress ratio. The specimens with a small layer angle had more noticeable time-independent and time-dependent deformations and larger steady-state creep rates than those of the specimens with a large layer angle. Attenuation creep and secondary creep could be observed at relative low stress levels, whereas accelerating creep until failure occurred at the creep failure stress level. The time for creep failure can be predicated according to the axial steady-state creep rate or volumetric creep curve. Damage in the rock-like specimens showed linear correlation with the stress ratio. Dip angle has a significant effect on the creep failure mode under cyclic loading–unloading conditions. [ABSTRACT FROM AUTHOR]

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In this paper, uniaxial material properties, creep resistance and impact energy of the austenitic heat-resistant steel (1.4841) are experimentally determined and analysed. Engineering stress–strain diagrams and uniaxial short-time creep curves are examined with computer-controlled testing machine. Impact energy has been determined and fracture toughness assessed. Investigated data are shown in the form of curves related to ultimate tensile strength, yield strength, modulus of elasticity and creep resistance. All of these experimentally obtained results are analysed and may be used in the design process of the structure where considered material is intended to be applied. Based on these results, considered material may be classified as material of high tensile strength (688 MPa/293 K; 326 MPa/923 K) and high yield strength (498 MPa/293 K; 283 MPa/923 K) as well as satisfactory creep resistance (temperature/stress →$ \to $strain (%) at 1,200 min: 823 K/167 MPa →$ \to $0.25 %; 923 K/85 MPa →$ \to $0.2 %).

To optimize the properties of asphalt mixtures and make full use of waste rubber tires, diatomite and crumb rubber particles were applied to reinforce the asphalt mixtures in this study. The rutting tests, the three-point bending tests, the freeze-thaw splitting tests, and the uniaxial compression creep tests were performed to analyze the effects of asphalt types and aggregate gradation on the pavement properties of diatomite and crumb rubber particles reinforced asphalt mixtures (DRPAM). Subsequently, the creep and relaxation characteristics of DRPAM were analyzed by the Burgers model, the modified Burgers model, the second-order extensive Maxwell model, and the Scott–Blair model. The results show that rubber particles and diatomite can reinforce the high temperature, low temperature, and viscoelastic properties of asphalt mixtures, although the improvement effect is weaker than styrene-butadiene-styrene (SBS). Consequently, it is concluded that rubber particle and diatomite compound modified asphalt mixture with suspension dense gradation and SBS binder will have better performance.

Highlights • Investigation of environmental and mechanical impact on notched beam used in building. • We propose a methodology for the following of deflection, crack and climatic parameters. • A mathematical expression of the Module of Elasticity with the shear effects is proposed. • Investigation of Thermo-hydro-mechanical behavior of Pseudotsuga menziesi and Abies alba Mil. Abstract The impact of variations of relative humidity, temperature and moisture content on the creep of notched beams of Douglas fir and white fir are investigated. Indoor static 4-points bending tests are followed by outdoor creep tests of notched beams designed to trigger the breakage mode associated with the use of notched ends. The dimensions of wood specimens follow Eurocode requirements. The maximum load applied to outdoor creep tests is derived from the failure load obtained during indoor instantaneous tests. The results show that the variations of the relative humidity and temperature, coupled with the loading, play a key role in the lifetime of timber, as they accelerate its aging. In addition, the link between the changes of climatic parameters and the damage of the beams and the limit of their lifetime as structure is shown. [ABSTRACT FROM AUTHOR]

Abstract Tensile creep is investigated in a La 60 Al 25 Ni 15 (at%) bulk metallic glass. Temperature and stress are chosen in a large range and tests are performed during long times (up to 105 s). The compliance of the samples, i.e. the ratio between the induced strain and the applied stress, is deduced from the resulting strain. A transition from a linear regime to a non-linear regime is progressively observed when either temperature or stress level is increased. This transition indicates a modification of the physical mechanism involved in the deformation. The physical model initially proposed by Perez et al is used to describe this transition. When a stress is applied shear micro-domains (SMDs) are progressively formed in appropriate shear planes and when the stress or temperature is high enough a coalescence of these SMDs occurs progressively. The phenomenon becomes irreversible and then the viscoplasticity takes place. The transition is therefore linked to the onset of viscoplasticity. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the influence of the adulteration agents (glucose, fructose, inverted sugar, hydrolysed inulin syrup and malt wort) on the rheological properties of an authentic honeydew honey. For this reason the honeydew honey and adulterated samples were analysed using steady state (η, thixotropic area), dynamic state (G′ and G″) and creep tests (J(max)). The addition of fructose decreased the dynamic viscosity, the malt wort and inverted sugar increased very little the dynamic viscosity while the glucose and hydrolysed inulin syrup increased significantly the dynamic viscosity, respectively. In order to classify the authentic honeydew honey and the adulterated honey samples it was used the Principal component analysis based on sugar composition (glucose, fructose, sucrose, maltose and melezitose) and all the rheological parameters analysed ( η, G′, G″ , thixotropic area and J max ). The results obtained proved that the steady state (η, thixotropic area), dynamic state (G′ and G″) and creep tests (J(max)) are a useful tool for detecting the honey adulteration with glucose, fructose, inverted sugar, hydrolysed inulin syrup and malt wort. [ABSTRACT FROM AUTHOR]

• Thermal creep behavior of CLF-1 steel is studied based on application of CN HCCB TBM. • Microstructure of CLF-1 steel reflects that the size and type of precipitates between as-received and crept samples are not changed. • CLF-1 steel reflects clear creep stage from the curve, the Larson-miller parameter shows CLF-1 steel is similar to Eurofer97 and even better than F82H. A series of thermal creep experiments are conducted on Chinese low-activation ferritic/martensitic steel (CLF-1 steel) at a temperature of 550, 575, and 600 °C with various normal stress (from 150 to 300 MPa), respectively. The results are analyzed by creep curves, microstructure, and creep properties. Finished samples display adequate fracture surface in short creep rupture tests (within 3000 h). The comparative creep curve shows no difference related to the thickness of CLF-1 steel plate (10 and 30 mm). Microstructure images before and after creep reflect a tempered lath martensite structure and carbides decorating both in prior austenitic grain boundaries and lath boundaries. Comparison is discussed between 30 mm plate and 10 mm plate. All current results reflect that all CLF-1 steel samples shows good creep behavior and proves that a series excellent progress of CLF-1 steel R&D work has been successfully achieved. Besides, collected data will contribute a lot to the design and R&D work of the Chinese Helium Cooled Ceramic Breeding Test Blanket Module (CN HCCB-TBM). [ABSTRACT FROM AUTHOR]

This work is focused on testing and evaluation of creep properties of P92 base material (BM) and welded joints (WJ) as well. Up to date results of creep rupture test of P92 base metal and welds are presented in this article. Creep rupture strength (CRS) of WJ initially reaches values close to the BM, with longer times to fracture and especially at higher temperatures, creep strength of WJ decreases and the data is closer to the lower 40 % tolerance band.

A waste-based particle polymer composite (WPPCs) made of foam glass and polypropylene was developed as a low-cost construction material. Thermomechanical properties of the composite, including creep properties of WPPC and polypropylene binder, were examined. By adding a relatively small amount of polypropylene to foam glass (about 2:8 in volume parts), the maximum bearing capacity at room temperature of the composite increased from 1.9 (pure foam glass) to 15 MPa. A significant creep strain accumulated during compressive loading of WPPC (5 MPa) in the first 2000 s at elevated temperatures (40, 60 °C). In the study, Kafka's mesomechanical model was used to simulate creep strain changes in time for various temperatures. The applicability of Kafka's mesomechanical model for simulating creep properties of the studied composite material was demonstrated. [ABSTRACT FROM AUTHOR]

By exploiting the Clausius–Planck local energy dissipation inequality, a large strain, three-dimensional constitutive model has been developed for the monotonic and cyclic response prediction of various asphaltic materials. The model consists of a Zener non-linear, visco-elastic component acting in series with a stress dependent viscous component. A novel computational scheme has been developed for solution of the coupled system of equations expressing the interdependent response of these two in series components. An explicit, mechanistic, parameter determination procedure is presented for the laboratory determination of all necessary model parameters. Examples of model parameter determination and utilisation for prediction of the response of a recycled asphalt mix and a stone mastic asphalt mix are presented. [ABSTRACT FROM PUBLISHER]

Material properties description and understanding are essential aspects when computational solid mechanics is applied to product development. In order to promote injected fiber reinforced thermoplastic materials for structural applications, it is very relevant to develop material characterization procedures, considering mechanical properties variation in terms of fiber orientation and loading time. Therefore, a methodology considering sample manufacturing, mechanical tests and data treatment is described in this study. The mathematical representation of the material properties was solved by a linear viscoelastic constitutive model described by Prony series, which was properly adapted to orthotropic materials. Due to the large number of proposed constitutive model coefficients, a parameter identification method was employed to define mathematical functions. This procedure promoted good correlation among experimental tests, and analytical and numerical creep models. Such results encourage the use of numerical simulations for the development of structural components with the proposed linear viscoelastic orthotropic constitutive model. A case study was presented to illustrate an industrial application of proposed methodology. [ABSTRACT FROM AUTHOR]

The effect of microstructural parameters on the microstructure, tensile properties from room temperature to 800 °C and creep properties at 650 °C has been investigated in a 14%Cr oxide dispersion strengthened (ODS) steel. Combining a control of oxide addition, consolidation route and thermo-mechanical processing, the different parameters of the microstructure have been varied systematically, namely the size and volume fraction of oxide nano-precipitates, the grain size and the dislocation density. The volume fraction of nano-precipitates is shown to influence the tensile strength throughout the temperature range, whereas a change in precipitate size influences only the low temperature behavior. The effect of grain size is shown to be similar to that of precipitation strengthening. A recrystallized microstructure is shown to improve the ductility of the ODS steel while not degrading the strength or creep resistance. The material processed by hot extrusion presents improved strength and reduced creep rate as compared to that consolidated by hot isostatic pressing. This difference is attributed to the long-range internal stress resulting from the high dislocation density, stabilized by the oxide nano-precipitates. A strength model is presented, and validated on every material using the quantitative microstructural parameters obtained by combination of electron back-scattered diffraction, transmission electron microscopy and small-angle X-ray scattering. [ABSTRACT FROM AUTHOR]

Natural gas hydrate, a promising new energy, has been widely concerned from the past decades. Significant experimental efforts have been made to explore the mechanical characteristics of hydrate-bearing clayey sediment under stable conditions, however, few studies focus on the creep characteristics of it during the dissociation process, which is closer to the actual condition of the reservoir. This study shows the triaxial creep test results of methane hydrate-bearing clayey sediment with the depressurization dissociation method, and the methane hydrate-bearing sandy sediments are added for comparison. The results show that in the creep process: (1) the depressurization has little effect on axial strain but causes the increase of the volumetric strain and the reduction of equivalent Poisson's ratio; (2) the number of depressurization times has no obvious effect on the total settlement and gas production rate during the depressurization process, the gas production rate is mainly determined by the pore pressure; (3) the gas production rate of hydrate-bearing clayey sediments decreases during the depressurization process, while the hydrate-bearing sandy sediments show an opposite trend; (4) higher stress level causes a great increase of the axial strain, volumetric strain and equivalent Poisson's ratio, while it causes a slight increase of the gas production rate. • The increasing effective confining pressure has little effect on axial strain. • The number of depressurization times has no effect on the total settlement. • The gas production rate is mainly determined by the pore pressure. [ABSTRACT FROM AUTHOR]

• For strands, the bond resistance is higher than the reference. • The incorporation of wood does not enhance the creep. • The concrete without wood cracked for lower loads than those with wood. • The wood concrete with sawdust resisted the fatigue tests without cracking. • Reference concrete presented higher bending stiffness than the wood-concrete. The present work intends to encourage a more widespread application of concrete mixes containing wood waste by investigating the steel–concrete bond of ordinary steel reinforcement bars and prestressed strands to assess the feasibility of using these composites in structural applications. After a set of preliminary tests, two mixes were selected in which aggregate was partially replaced by wood chip and sawdust. The effect of the steel–concrete bond length and reinforcement diameter on the shear strength was evaluated for steel bars and two-wire strands. The incorporation of wood appears to create a better mechanical interaction by increasing the component of friction as a resistance mechanism. In the case of the strands, the bond resistance is significantly higher (above 2.3 MPa) than the reference (0.9 MPa), regardless of the wood-concrete composites and the bond length. Additional tests have been performed to evaluate a possible creep effect. The specimens were subjected for 120 h to a constant tensile load corresponding to 50% of the mean results of the pull-out test. Results show that incorporating wood does not enhance the creep for this load level. Full-scale structural elements were also constructed to assess the feasibility of using these composites in structural applications. Bending and bending plus fatigue tests were performed to determine the behaviour under static and dynamic loads. It was concluded that the reference concrete without wood incorporation cracked for lower loads (26.0 kN) than the composites with wood (above 38.8 kN) and presented much higher bending stiffness (27835 kN.m2) than the wood-concrete composites (below 8544 kN.m2). The wood concrete with sawdust resisted fatigue tests without cracking. [ABSTRACT FROM AUTHOR]

Creep behaviors of methane hydrate-bearing frozen specimens are important to predict the long-term stability of the hydrate-bearing layers in Arctic and permafrost regions. In this study, a series of creep tests were conducted, and the results indicated that: (1) higher deviator stress (external load) results in larger initial strain, axial strain, and strain rate at a specific elapsed time. Under low deviator stress levels, the axial strain is not large and does not get into the tertiary creep stage in comparison with that under high deviator stress, which can be even up to 35% and can cause failure; (2) both axial strain and strain rate of methane hydrate-bearing frozen specimens increase with the enhancement of deviator stress, the decrease of confining pressure, and the decrease of temperature; (3) the specimens will be damaged rather than in stable creep stage during creeping when the deviator stress exceeds the quasi-static strength of the specimens.

Warm mix asphalt (WMA) is a new research topic in the field of road pavement materials. This technology allows lower energy consumption and greenhouse gas (GHG) emissions by reducing compaction and placement temperatures of the asphalt mixtures. However, this technology is still under study, and the influence of the WMA additives has yet to be investigated thoroughly and clearly identified, especially in the case of crumb rubber modified (CRM) binders. In order to study the effect that different types and quantities of organic waxes have on the high and intermediate temperature properties of 15 % and 20 % CRM binders, a dynamic shear rheometer (DSR) was used. Using Black diagrams, the rheological behaviour of the binders for the defined range of test temperature and frequency are summarised in a single diagram. In this way, a preliminary evaluation of the rheological behaviour in the extended domain of time and temperature can be attained as well as the effectiveness of the time-temperature superposition principle (TTSP) on the materials under study. Creep tests were also performed in order to evaluate the differences regarding mechanical response due to the addition of rubber and WMA additives, and particularly the ability to recover the strain at high temperatures. The results of this study reveal that these binders do not conform to the Time Temperature Superposition Principle (TTSP) and their rheological behaviour is strongly affected by the interaction of waxes and bituminous matrix and thus generally exhibited a higher elasticity compared to the corresponding control binder. The creep test results carried out proved the enhancement of elasticity and the resistance to permanent deformation produced by the addition of waxes. The WMA additives significantly lower the maximum deformation when compared to the control binders and slightly increased their elastic recovery. [ABSTRACT FROM AUTHOR]

A series of creep tests were carried out in order to clarify the creep behaviors of methane hydrate coexisting with ice, which may exist in the ice-bearing permafrost. Measurements on synthetic methane hydrate-ice specimens indicate that (1) higher external load will increase the initial strain and the axial strain during the whole creep test. And the creep strain rate will increase with the increase of external load; (2) the initial strain, axial strains and creep strain rate of the specimens under certain external load increase with the decrease of confining pressure; (3) temperature drop leads to the decrease of initial strain and axial strains of the specimens under certain external load. And the creep strain rate firstly increases and then decreases with the increase of temperature, due to the refreezing of dissociated water from methane hydrate; (4) the specimens run to the secondary creep stage earlier when they endure lower external load, higher confining pressure and lower temperature; (5) the specimens under higher confining pressure and lower temperature show higher failure strength. [ABSTRACT FROM AUTHOR]

In the presented paper, the creep of steel spiral strands with a construction of 1 × 7 and 1 × 19 round wires subjected to constant axial loads is studied numerically. The principal aim of this contribution is to define and describe a novel design computational tool for the numerical simulation and prediction of creep strains in spiral strands. For this purpose, finite element models are developed using ANSYS software. Wires of the strands are modelled using 3D geometrically nonlinear beam elements. An approach is based on the Timoshenko beam theory and Saint Venant torsion theory. The wire material is both linearly elastic and isotropic. Creep strain of strands is caused by the creep strain of wires due to the tensile load acting on them and by extension due to the construction of the strand when the strand is tightened. The constitutive creep equations of wires and selected initial clearances between wire layers are incorporated into the finite element models. The models are set up and calibrated on the basis of data obtained by the creep tests. In principle, the required functionality and performance have been implemented in the software and a good agreement with test results has been obtained. [ABSTRACT FROM AUTHOR]

Creep deformations that occur at high temperature can significantly influence the fire response of steel structures. There is limited data on the effect of temperature on creep deformations in structural steel used in construction applications. This paper presents an investigation into temperature induced creep in high-strength low-alloy ASTM A572 steel commonly used in structural members. A set of creep tests is carried out at various stress levels in 400-800 °C range which is commonly encountered temperature range in structures subjected to fires. Results from these creep tests indicate that temperature has significant influence on the level of creep deformations in ASTM A572 steel, especially when the temperature exceeds 500 °C. The extent of creep deformation at a given temperature increases with stress level and the effect can be substantial at 550 °C when the stress level exceeds 50 % of room temperature yield stress. But creep deformations can rapidly rise beyond 800 °C even for low stress levels of about 10-15 % of room temperature yield stress. [ABSTRACT FROM AUTHOR]

The paper presents the geotechnical, geophysical investigations and the numerical static and seismic analysis of selected underground monuments in Alexandria, Egypt i.e. the underground tombs in Mustafa Kamil Necropolis. The analysis of the static stability and the behavior of complex monuments of this kind under seismic loading, are the key factors for the efficient restoration and retrofitting of these underground monumental structures. In the present paper, we present in a first phase a comprehensible geotechnical survey undertaken in this site, comprising geophysical ambient noise measurements (microtremors), as well as field and short -- long-term laboratory experiments and tests, in order to define the physical, mechanical and dynamic properties of the soils and soft rock materials. In the second stage, we present the main results of the detailed static and seismic numerical analysis of these underground monumental structures (Catacombs) using the code, PLAXIS b.v with different seismic scenarios corresponding to the seismotectonic features of Alexandria. Advanced soil-rock elastoplastic modeling has been used through out the different phases of the numerical finite element analysis. The aim of the analysis is twofold: (a) to investigate the safety margins of the existing monuments, under their present conditions, against environmental (i.e. weathering) and extreme seismic loads and (b) to investigate the potential improvement of their global behavior applying specific retrofitting techniques. [ABSTRACT FROM AUTHOR]

In order to determine the behavior of the X10CrAlSi25 steel at room and elevated temperatures, a number of uniaxial tests were performed using a modern computer controlled material testing machine. Based on these tests, two types of their responses were considered. The first type of responses refers to the material properties presented in the form of engineering stress-strain diagrams. From these diagrams it is possible to derive and consequently to determine tensile strength, yield strength and a Modulus of elasticity. The second type of responses refers to creep behavior presented in the form of creep curves. Based on these curves, creep resistance of the considered material can be derived. Besides, the Charpy impact tests were performed with a Charpy impact machine to define Charpy impact energy as the basis for calculating fracture toughness. Considering tensile strength (584 MPa/20 °C) and yield strength (487 MPa/20 °C), it is visible that both of them are decreased when temperature is increased and fairly low strength levels at high temperature (tensile strength: 29 MPa/800 °C; yield strength: 26 MPa/800 °C) are measured. According to performed creep tests it is visible that this material does not belong to the materials resistant to creep. [ABSTRACT FROM AUTHOR]

This work is focused on testing and evaluation of creep properties of P92 base material (BM) and welded joints (WJ) as well. Up t o date results of creep rupture test of P92 base metal and welds are presented in this article. Creep rupture strength (CRS) of WJ initially reaches values close to the BM, with longer times to fracture and especially at higher temperatures, creep strength of WJ decreases and the data is closer to the lower 40% tolerance band. [ABSTRACT FROM AUTHOR]

A series of triaxial compression tests, triaxial extension tests, and triaxial compression creep tests were conducted to evaluate the strength, deformability, and permeability of rock salt from the Jintan location. Based on a previous analysis, the measured data can be physically modeled very well as shown by the constitutive model Hou/Lux and indicate that China's representative bedded rock salt from the Jintan location is characterized by good ductility and deformation properties, similar to the European high-purity rock salt. Based on a comparison of compression as well as extension failure strength determined at rock salt from Jintan location, a similarity of compression and extension failure strength could be demonstrated. Permeation flow seems to be an anisotropic process because the permeability measured at samples prior to failure by compression tests differs to those measured at samples prior to failure by extension tests. The anisotropy of damage and destruction of rock salt has a significant influence on permeability. In case of triaxial compression tests, the measured permeability increases two to six orders of magnitude because of consistent direction of injection and cracks. In case of triaxial extension tests, however, the permeability increases less with a maximum of two orders in magnitude. The test results are significant for understanding the load-bearing behavior of rock salt from Jintan location and investigations with reference to the stability and tightness of underground caverns. [ABSTRACT FROM AUTHOR]

High Density Polyethylene (HDPE) is widely used for the distribution of drinking water and are exposed to an internal pressure due to water flow. Furthermore, when they are in contact with disinfectants, oxidation of HDPE occurs at the immediate surface of the inner wall. This leads to a decrease in the HDPE molar mass and consequently, to a hardening as well as an embrittlement of the material. The oxidised layer thickness seems to stabilize at 200 μ m whatever the initial pipe thickness due to the diffusion of reactive species in the inner wall. Inspections with a scanning electron microscope (SEM) of the inner wall of pipes collected on site, after several years of service, showed a network of cracks. The most noxious (deepest) longitudinal crack propagates under the steady internal pressure until the complete failure of the pipe. The experimental investigations consisted of creep crack growth tests, carried out on an original geometry for this type of test using NOL ring. These specimens were cut from the pipes and an internal longitudinal crack implanted. Creep crack growth tests were performed at various net stresses and at various crack depth ratios. At the end of each test, the time to failure was recorded. Before applying the theory of fracture mechanics of creeping solids, 3D finite element simulations were carried out to assess the suitability of assuming plane strain conditions. To this end, a porous viscoplastic model was implemented into an in-house finite element code. A fracture criterion based on critical porosity allowed for the simulation of creep crack growth. The localization of the maximum damage at mid-thickness and the thickness reduction were well captured. In these conditions, the crack front curvature is located near the surface so that a 2D calculation with plane strain conditions can then be justified to determine the C* load parameter. The residual lifetime of a real pipe containing a longitudinal defect, under in-service loading was estimated by using the correlation between the time to failure and the C*-integral. [ABSTRACT FROM AUTHOR]

Extrudierter Polystyrol-Hartschaum (XPS) hat aufgrund seiner ausgezeichneten Eigenschaften als lastabtragende Wärmedämmung in letzter Zeit große Aufmerksamkeit erregt. Diese Art der Wärmedämmung wird häufig unter Plattengründungen eingesetzt, bei denen hohe Druck- und teilweise auch Schubspannungen auftreten. Damit die Dämmplatten sicher in diesem Bereich angewendet werden können, sollte ihr Kriechverhalten untersucht und bewertet werden, um mögliche unverträgliche Setzungen zu vermeiden. Das Hauptziel der vorliegenden Untersuchungen ist es, das Kriechverhalten von lastabtragenden XPS-Wärmedämmstoffplatten unter reinen Schubspannungs- und kombinierten Druck-Schubspannungszuständen zu prüfen und eine potentielle Auswirkung, welche die Druckbelastungen auf das Schub-Kriechdehnungsverhalten unter kombinierten Belastungszuständen haben könnte, zu untersuchen. Mit einem speziell dafür entwickelten Prüfstand wurden Versuche zum Kriechverhalten von XPS-Hartschaumplatten unter Schub- und kombinierten Druck-Schubspannungszuständen durchgeführt. Versuchsergebnisse zeigten einen leichten Anstieg des Kriechdehnungsverhaltens aufgrund der Einwirkung von Druckbelastungen in kombinierten Lastzuständen. Die Ergebnisse der Versuche zum Kriechverhalten wurden verwendet, um möglichst genaue Annäherungen zu erhalten, die das Kriechverhalten unter den genannten Belastungen darstellen. Eine Übersicht, wie das Kriechverhalten anhand der Finite-Elemente-Methode mithilfe von mikrostrukturbasierten FE-Modellen simuliert werden kann, wurde vorgestellt. Die Mikrostruktur wurde mithilfe von Röntgenstrahlung festgehalten und sichtbar gemacht. Die entwickelten mikrostrukturbasierten FE-Modelle wurden dann verwendet, um eine Parameterstudie zur Optimierung des Kriechverhaltens von XPS Hartschaumplatten unter Schub- und Druckbelastungen durchzuführen. Experimental and finite element analysis of creep behavior of extruded polystyrene rigid foam. Extruded polystyrene (XPS) rigid foams have recently attracted a great attention as a superior load-bearing thermal insulation material. This type of thermal insulation material is commonly used under raft foundations, where high levels of compression loads and sometimes shear loads take place. To apply these boards safely in such application areas, their creep behavior should be intensively evaluated and analyzed to avoid any hazardous potential settlement. The principle objective of the current research is to investigate the creep behavior of XPS load-bearing thermal insulation boards under pure shear and combined shear-compression stress states and to explore any potential effect the compression stresses could have on the shear creep strains under the combined loading state. Creep tests were performed on XPS rigid foam boards under shear and combined shear-compression stress states using a specially developed test set-up. Experimental results showed a slight increase in the creep shear strains due to the application of compression stresses in the combined loading conditions. Creep test results have been used to investigate the most accurate approach able to model and extrapolate the creep behavior under these types of stresses. An overview of simulating the creep behavior through finite element method using microstructure-based FE models was introduced. The microstructure was captured by the x-ray computer tomography imaging technique. The developed microstructure-based FE models were then used to carry out a parametric study aiming to optimize the creep response of XPS boards under shear and compression loads. [ABSTRACT FROM AUTHOR]

Currently, ASTM A335 P92 is the best available material for manufacturing major steam lines and manifolds for modern Ultra Super Critical thermoelectric power stations, in that it combines high resistance to a viscous creep, high microstructural stability, and good resistance to steam corrosion and oxidation. These characteristics allow it to be used at up to 620°C and at pressures of up to 320 bar. Welding this material, characterized by a high alloy content, requires particular attention with regard to the control of the operating conditions. In this paper, Tenaris and the Italian Welding Institute present a joint study investigating the weldability of Grade 92, in which the effect of varying significant parameters such as preheating, interpass, and post-welding treatments on joint mechanical and microstructural properties has been examined. [ABSTRACT FROM PUBLISHER]