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To ensure long-term safety and performance, geological nuclear waste repositories require low-permeability barriers such as bentonite buffers and/or shale host rock. Shale is not only known for its low permeability but also for its trend to undergo time-dependent deformation (i.e., creep), which could heal damage, but the effects of shale creep on the long-term performance of nuclear waste repositories have not been clearly understood. In particular, the anisotropic nature of shale (i.e., bedding) could have a significant effect on its creep behavior, and consequently, on the long-term performance of nuclear waste repositories. In this research, numerical simulations were carried out with the objective of showing the effects of anisotropic shale creep on the stress and permeability evolution of a generic geological nuclear waste repository in shale. The TOUGH-FLAC simulator, a thermo-hydromechanically (THM) coupled numerical code, was used for the simulations. To achieve the objective, comparisons were performed between the results of anisotropic shale creep simulations and those of different simulation cases, namely, no creep (i.e., elastic), isotropic creep, and long-term creep shale cases. Results of the comparisons show that the elastic and isotropic creep shale cases respectively led to the overestimation and underestimation of stress and permeability in the repository, whereas the long-term creep shale case, which accumulated greater creep in later periods than in earlier periods, helped to keep large shear and tensile stresses from developing while maintaining compressive spherical stress, resulting in consistently low permeability levels. These results indicate that performance assessments with elastic and isotropic creep formation models will provide the upper and lower bound estimates of stress and permeability, while more reasonable estimates will be given by an anisotropic creep formation model, and that shale with long-term creep characteristics will be beneficial in many aspects of the safety and performance of nuclear waste repositories.

The Caney shale is an emerging hydrocarbon play located in southwest Oklahoma, USA. Within the Caney shale exist facies which were initially dubbed “reservoir” and “ductile” based on evaluation of well logging data. While past work has shown the distinction of “brittle” and “ductile” is not mechanically justifiable according to formal definitions, the current work shows some important differences between nominally ductile and reservoir zones. First, the “ductile” zones are more clay rich and have textural differences which can be expected to lead to differences in mechanical properties. One important impact of these differences is observed in triaxial creep experiments showing the “ductile” zones are more prone to creep deformation. Numerical simulations predict the “reservoir” zones will experience very little proppant embedment due to creep deformation of hydraulic fractures around proppant particles. On the other hand, “ductile” zones can be expected to undergo creep-driven proppant embedment leading to loss of fracture aperture ranging up to 100% loss, depending upon the spatial density of the proppant distribution. Hence, this research shows the identification of nominally “ductile” zones from well logs, while a misnomer, can be useful in finding clay-rich, creep-prone zones which will be the most prone to proppant embedment and hence vulnerable to greater production decline over time.

The creep behavior of an additively manufactured (AM) yttrium oxide dispersion strengthened (ODS) CrCoNi multi-principal element alloy (MPEA) is investigated in this study. Tests were conducted over a constant tensile stress range of 40–200 MPa and a temperature range of 973–1173 K. A stress exponent of 6.5 ± 0.1 and activation energies in the range of 335–367 kJ/mol were measured. Compared to its non-ODS counterpart and its parent alloy (CrMnFeCoNi), AM ODS CrCoNi has superior creep resistance at all tested stresses and temperatures. The mechanism contributing to the excellent creep resistance of AM ODS CrCoNi is attributed to the interaction of mixed character dislocations with oxide particles. The creep ductility of AM ODS CrCoNi is higher than its non-ODS counterpart due to a large percentage of low angle grain boundaries associated with its columnar grain structure. It was also found that creep ductility is significantly greater at the highest applied stress of 200 MPa compared to lower stresses. The steady state dislocation structure of AM ODS CrCoNi consists of long arrays of dislocations, which is different from that observed in non-ODS CrCoNi which consists of individual curved dislocations.

Fundamental mechanical and creep behavior of minerals at elevated temperatures is relevant to many subsurface exploration and resource recovery processes, yet remains largely elusive. This study uses instrumented indentation to measure microscale deformation and nanoscale creep of biotite, albite, and quartz, which are the major mineral phases of granitic rocks, at temperatures up to 400 °C. The results show that the elastic modulus of biotite is not only the lowest at room temperature but also decays the most at elevated temperature (i.e., by 25% reduction at 400 °C) compared to that of albite and quartz. The creep deformation within 20 s doubles when the temperature increases from 20 °C to 400 °C for albite, quartz, and biotite, and biotite showed at least three times the overall creep deformation compared to quartz and albite under the same temperature. The indentation creep deformation can be well characterized using a logarithmic time model, showing both transient and constant-rate creep deformation. The secondary creep rate for biotite is about three times that of albite and quartz at the same temperature, and as the temperature increases from 20 °C to 400 °C, the rate of secondary creep becomes approximately 10 times faster for the three tested minerals. Both transient creep deformation and the rate of secondary creep can be empirically correlated to the elastic moduli, which allows quick estimates of the temperature-dependent creep behavior of granitic minerals using their elastic properties, especially when those creep constants are not readily available at elevated temperatures. These results enhance the understanding of temperature-dependent creep deformation at small scales and provide insight into mineral-level damage in granitic rocks due to temperature and long-term deformation.

Introduction: Salt formations are complex and pose significant risks during oil and gas drilling. Creep behavior in salt formations under geostress can jeopardize drilling safety. Methods: This study analyzes the shrinkage behavior of boreholes drilled through salt formations in West Africa's Block B, with emphasis on the differential creep rates in two horizontal principal stress directions and the evolution of wellbore shape over time. The impact of drilling fluid density on shrinkage rates is also investigated. Results: After drilling through salt formations, the creep rates differ between the two horizontal principal stress directions. Shrinkage is faster in the direction of minimum horizontal principal stress and slower in the direction of maximum horizontal principal stress. Over time, shrinkage rates converge, resulting in a transition from elliptical to circular wellbore shape. Higher drilling fluid density leads to reduced shrinkage rates. Discussion: These findings contribute to the theoretical guidance for drilling fluid density selection in salt formations. [ABSTRACT FROM AUTHOR]

Applications of Bayesian updating commonly treat soil parameters as random variables. A significant issue with this is that soil parameters are highly subjective. Therefore, using traditional parameter-based models, Bayesian analysis starts from a subjective prior and it is unclear how this may influence the overall results of a study. In this paper, Bayesian updating is combined with a data-driven method, known as CRACA (i.e., CReep And Consolidation Analysis), for predicting the settlement of embankments on soft soil. Importantly, the method directly ingests measured oedometer data and, therefore, avoids the subjectivity involved in parameter selection. Because parameters are not used, scaling factors are introduced that account uncertainty associated with the laboratory measurements and the automated interpretation process. These factors have an initial value of unity (returning the prior) and are updated in a Bayesian framework as settlement monitoring data are revealed over time to improve future forecasts. The model was applied to an embankment case history and was shown to result in a rapid improvement in the accuracy and a narrowing of the 95% confidence interval as settlement monitoring data are revealed to the model. [ABSTRACT FROM AUTHOR]

Viscous behaviour is a significant characteristic of soil, and to accurately capture this behaviour, a piecewise-linear model called ACLC has been developed specifically for modelling one-dimensional large-strain consolidation of soft clay. ACLC takes into account both the long-term deformation and anisotropy of the soil. Furthermore, it incorporates various factors such as soil heterogeneity, self-weight, time-dependent loading, vertical flows, and seepage force. In ACLC, the settlement of the soil layer is a result of both the net outflow of fluid from the soil element and the development of soil creep. To describe the creep behaviour of the soil, ACLC employs two yield surfaces: the Current State Surface (CSS) and the Normal Consolidation Surface (NCS). The creep rates are calculated based on the associated flow rule. To ensure the accuracy of ACLC, it is validated using the enhanced CS2 model, oedometer tests conducted on Xiaoshan soft clay, and observed data from the Murro test embankment. Finally, the influence of ACLC parameters on the consolidation behaviour of clay is thoroughly investigated. This analysis helps to understand the role of these parameters and their impact on the overall consolidation process. [ABSTRACT FROM AUTHOR]

This paper examines the consolidation and settlement behaviour of soft clay deposits treated with granular columns (single and in groups). Two Rowe cell loading chambers were used to conduct the investigations on samples of kaolin and a local Belfast natural estuarine alluvium called 'sleech'. Tests were carried out on unreinforced samples and then reinforced samples with single and multiple column configurations. The test duration for each test was between 3 and 4 months, depending on the test material and the granular column configuration. The settlement reduction factors based on primary and secondary consolidation were examined. The study suggests that the effectiveness of granular columns at mitigating primary and/or secondary settlement is directly related to the loading intensity, the stress history and the creep characteristics of the subsoil. It was also found that the stress concentration ratio reduced with the stress level. Secondary consolidation also has some effects on the stress concentration ratio. [ABSTRACT FROM AUTHOR]

Relaxation dynamics, essential for the structural evolution of non-equilibrium systems like glassy materials, remain enigmatic. Here, we explore relaxation dynamics and viscoelastic properties in three types of metallic glasses with distinct β relaxation behavior. In systems with significant β relaxation, stress relaxation and creep experiments reveal a transition from two-step to one-step relaxation with rising temperature. However, such a phenomenon is absent in systems with weaker β relaxation. We model the two-step relaxation process using a double Kohlrausch-Williams-Watts equation, and the obtained relaxation times elegantly adhere to the Arrhenius relationship. By combining fitted activation energies with theoretical analysis, we conclusively attribute these relaxation processes to β relaxation and α relaxation, respectively. Finally, we analyze the relaxation time spectra of two processes and establish a comprehensive picture linking dynamic relaxation with viscoelasticity. Our study provides new strategies for probing the complex relaxation behaviors of glasses from the perspective of viscoelasticity. [ABSTRACT FROM AUTHOR]

The formulation of the problem and the basis of the method for solving two-dimensional creep problems for the case of finite strains are presented. The method is based on the Arbitrary Lagrange-Euler (ALE) approach in numerical modeling using FEM. The method is implemented in the form of additional units to the creep calculation software. The plane stress state is considered. The results of an experimental study of the creep of AlMg6 alloy specimens under static and cyclic loading are described. The obtained creep curves were used to verify the calculation method. It is shown that for a material with viscous creep properties, calculations using finite strains quite satisfactorily describe the tertiary, accelerated section of the creep curve. The creep of square plates in tension by static and cyclically varying traction was considered, data on their shape change and stress redistribution were obtained. A significant intensification of creep due to the addition of a cyclic component to the static loading was established. [ABSTRACT FROM AUTHOR]

The construction of large-span and variable-section foundation pits in silty soil is challenging. Soil creep often leads to engineering problems such as excessive settlement, uneven settlement, and slope instability. This study proposes a new construction method, which is suitable for the inconsistent bottom elevation of a foundation pit by taking the long-span and variable-section foundation pit in Nanjing as an example. The construction process parameters were determined based on ABAQUS, and the accuracy of the numerical model and safety of the construction method were verified by field monitoring. The results show that foundation pit deformation increases with the distance between the supporting erection and the step length. Basal uplift decreased with an increase in excavation distance in the shallow area. The influence of the steel support erection time within 12 h on the foundation pit deformation was the most evident. The proportion of creep deformation in the foundation pit deformation on the early excavation side was approximately 21.6%, which was higher than that on the late excavation side. The location of the soft soil layer has an evident influence on the deformation of the foundation pit, and the creep deformation can reach 11% of the total displacement when it is located at half of the excavation depth. [ABSTRACT FROM AUTHOR]

Summary: The mechanical characteristics of the setback super‐tall structure are complex, and the design is difficult. In the actual analysis and design process, the relevant influencing factors should be fully considered. In this paper, the fine construction simulation analysis of the super‐tall structure is carried out. Based on the shrinkage test of concrete members, the CEB‐FIP 90 shrinkage model is modified in terms of the parameters of cross‐section shape and size. The modified model is used to calculate the shrinkage strain of concrete, and the influence of uneven settlement of foundation and seasonal temperature on the structure is considered in the construction simulation analysis. The influence proportion of each non‐load effect on the horizontal displacement, vertical displacement, and internal force of key components is obtained. The refined construction analysis results are compared with the field monitoring data, and the data are in good agreement. [ABSTRACT FROM AUTHOR]

Maintaining the geometrical stability of hot filament is a challenge in chemical vapor deposition (CVD) over a larger area since deformation varies the distance between the filament and the substrate and, consequently, destroys the uniformity of diamond deposition. Herein, Ta filament is straightened with a tensile stress ranging from 4.40 to 11 MPa to suppress deformation, and the stability during the CVD process of diamond film is evaluated. Scanning electron microscopy and energy dispersive X‐ray are further utilized to investigate the morphological and structural evolutions of Ta filament. Results show that straightened Ta filament maintains geometrical stability without any visible deformation or breakage and uniform deposition of diamond film is obtained through Ta filament undergone a transformation from Ta to Ta2C and then to TaC. At high deposition pressure (7 kPa) or a low concentration of methane (1%), the straightened Ta filament goes through a moderate transformation, which implies the cracks caused by rough transformation can be avoided, thus prolonging the lifetime of straightened Ta filament. These works provide significant guidelines for the large‐scale manufacture of diamond deposition. [ABSTRACT FROM AUTHOR]

High-performance composites are subjected to different mechanical forces and stresses during their lifetime. Hence, knowledge of the time-dependent deformation at different temperatures is crucial for engineering applications. In this context, a polyetherimide/carbon fiber composite was analyzed via creep behavior from the glassy to the elastomeric state (30–250 °C). Creep tests were carried out under low-stress loads. An artificial neural network (ANN) was used to fit the curves for all tested temperatures. The ANN allowed excellent fit for all conditions independently of the curve shape, mainly for the glassy region, in which most of the analytical models did not fit well. This study is a growing and promising field in the materials science field due to the fact that it uses ANN as an alternative to fit creep behavior not fitted by usual analytical equations, which utilize closed-form solutions. Furthermore, it is expected that this study will allow the formulation of new equations and methods to determine the creep behavior at high stresses, for example. [ABSTRACT FROM AUTHOR]

This study examines the influence of weathering aging on the mechanical properties and durability of flax fiber‐reinforced polymer composites (FFRP) intended for outdoor applications. Employing an accelerated weathering environment replicating natural outdoor conditions, encompassing UV radiation, condensation, and water spray, the FFRP samples with 2 and 4 mm thicknesses underwent exposure durations of 0, 500, 1000, and 1500 h. Mechanical tests characterized tensile, flexural, and inner‐plane shear properties, while a custom‐made apparatus measured the long‐term tensile creep behavior. Additionally, scanning electron microscopy allowed for the observation of microscopic changes in fiber and matrix. The findings illustrate a consistent decline in tensile and flexural properties with increased weathering exposure, resulting in reductions of 17% and 38% in the tensile strength and modulus, and 24% and 52% in the flexural strength and modulus after 1500 h. Intriguingly, inner‐plane shear strength exhibited a slight increase after 500 h before a subsequent decrease. Furthermore, samples with the same thickness demonstrated an increased creep development with longer weathering durations. Despite this, the mechanical degradation rate induced by weathering was comparatively slower for thicker samples. Overall, the diminished mechanical properties of FFRP post‐weathering can be attributed not only to the polymer but also to the substantial role played by flax fibers in this process. Highlights: UV weathering degrades the mechanical properties of flax/polyester composites.Both the instantaneous elastic properties and the long‐term creep behavior are affected by weathering.Thickness influences the mechanical degradation of the composites caused by UV weathering.SEM confirmed UV‐water weathering resulted in the degradation of both natural fiber and polymer matrices. [ABSTRACT FROM AUTHOR]

This study delves into the convergence of operators and the viscoelastic properties of fractal ladder and tree structures. It proves the convergence of fractal stiffness operators through operator algebra, revealing a fundamental connection between operator sequence limits and fractal operator algebraic equations. Our findings demonstrate that, as the hierarchical levels of these structures increase, their viscoelastic responses increasingly align with the fractional viscoelastic behavior observed in infinite-level fractal structures. We explore the similarity in creep and relaxation behaviors between fractal ladders and trees, emphasizing the emergence of ultra-long characteristic times in steady-state creep and pronounced tailing effects in relaxation curves. This research provides novel insights into the design of fractional-order viscoelastic structures, presenting significant implications for materials science and mechanical engineering. [ABSTRACT FROM AUTHOR]

In many settlement prediction methods, the creep settlement of shallow foundations on sand is either disregarded or accounted for using time correction factors that lack a reliable basis. These existing settlement correction factors for creep have mainly been derived from a restricted number of long-term settlement measurements and do not consider the influence of factors such as the load level, rate of load application and properties of the soil below the foundation. In this study, a newly proposed one-dimensional elasto-viscoplastic macro-element was used to investigate the factors influencing the time-dependent behaviour of shallow foundations on sand. The safety factor of the foundation, the creep characteristics of the soils and the duration of load application were found to have important effects on the post-construction settlement development. The simulation results were used to develop an enhanced settlement correction factor for creep, which takes into account the identified factors. The improved settlement correction factor was found to be comparable to existing ones when the safety factor of the foundation is 3. The effectiveness of the proposed settlement correction factor is demonstrated using creep settlement measurements from one field footing test and two case histories. [ABSTRACT FROM AUTHOR]

Understanding viscoelastic behavior of dielectric elastomers for artificial muscle application is important to regulate actuation performance, response time, energy density, sensitivity, duty cycle, etc. The performance of elastomers is widely recognized as being influenced by various fillers, including functional particles and poly-reagents. However, the impact of fillers on the viscoelastic properties of VHB 4910 remains to be fully understood. In this work, a new range of particulate-polymer filled VHB elastomers are studied for the effects of barium titanate and Ketjenblack particles dispersed trimethylolpropane trimethylacrylate on viscoelastic properties. This followed characterization of stress-relaxation and creep behavior to realize the time-dependent mechanical performance. Also, the stress-softening and energy dissipation behavior are examined to find the number of cycles required to reach the equilibrium energy state. Viscoelastic properties of elastomer including elastic modulus, toughness, are found to significantly reduced as a result of modified poroelastic effects due to incorporated fillers. The mechanical properties of composites are evidenced to depend on the size of the particulates and the amount of polymer reagent within elastomer. Theoretical analysis comparing deformation, relaxation, and creep mechanisms in biomedical materials validates the potential of modified elastomers for use in soft actuation devices, particularly in the field of artificial muscles. This work may help in recognizing the strategies to tune viscoelastic behavior of microporous elastomers for potential applications in flexible electronics. [ABSTRACT FROM AUTHOR]

Single- and multi-stage isotropic creep tests including bender element and acoustic emission measurements are carried out to investigate the relationship between ageing and creep in dense silica sand. In the considered pressure range, the experimental results show an inversely proportional relationship between ageing and creep: the small-strain shear modulus increases with decreasing isotropic pressure,, while the axial creep strain and the acoustic emissions show the opposite pressure dependence. In the multi-stage creep test, the small-strain shear modulus increases monotonically, while the rates of axial strain, number of acoustic emissions and small-strain shear modulus decrease with time according to a power law. In the single-stage creep tests, the ageing and creep indicators initially evolve as in the multi-stage creep test, but then the small-strain shear modulus reaches a peak value and decreases with time thereafter. At the same time, the rates of axial strain, number of acoustic emissions and small-strain shear modulus deviate from the power law. A conceptual model assuming a time-dependent behaviour of the normal and shear forces at the particle contacts in order to explain the experimental observations qualitatively is proposed. Accordingly, an increase in small-strain shear modulus results from homogenisation of the force chains, while a decrease in small-strain shear modulus results from a temporary formation followed by a time-delayed collapse of strong force chains. [ABSTRACT FROM AUTHOR]

Traditional concrete creep testing and prediction methods are cumbersome and time-consuming. In this study, the creep behavior of concrete modified with various supplementary cementitious materials (sludge and fly ash, 10–30 wt.%) was investigated and analyzed using the indentation tests and multiscale homogenization analysis. The study revealed that incorporating 10% water treatment sludge ash (WTSA) effectively enhanced concrete’s axial compressive strength and elastic modulus, while reducing its creep strain. This was mainly because adding 10% WTSA improved the compactness of concrete and increased the ratio of high density (HD) C–S–H in C–S–H gel and reduced the width of interfacial transition zone (ITZ). However, a higher content of WTSA admixture was observed to negatively impact the concrete properties. Furthermore, the creep behavior of concrete was predicted through multiscale homogenization calculations. Utilizing the nanoindentation technique, accurate predictions in the multiscale creep model can be obtained by differentiating and quantifying the volume fraction of the physical phase based on the characteristic indentation modulus. In contrast, the quantitative results of the physical phase obtained from the inverse convolution need to be corrected by thermogravimetric analysis and backscattered electrons to obtain a higher level of accuracy in creep prediction. [ABSTRACT FROM AUTHOR]

This article presents a study carried out on a 2 kN·m torque transducer at the Central Office of Measures (GUM) and the Physikalisch-Technische Bundesanstalt (PTB). The weighted least squares method was used to generate the linear regression equations for this torque transducer. The Monte Carlo method and the law of uncertainty propagation were used to calculate the expanded uncertainty. In addition, a creep study was carried out at eight measurement points ranging from 200 N·m to 2000 N·m. The investigations showed that the highest readings of the torque transducer, expressed in electrical units as mV/V, occur within the initial few seconds of the test after the removal of the maximum reference torque. [ABSTRACT FROM AUTHOR]

After the gas drainage borehole is formed in the coal seam, its stress deformation process is a creep process without the influence of mining. By arranging boreholes on coal samples and carrying out creep loading test of porous coal through rock mechanics testing machine, the creep process of boreholes in actual coal seams is simulated. The results show that the creep loading test results of drilled coal are quite different from those of conventional loading. Creep loading produces large deformation due to rheological and aging characteristics. Compared with non-porous coal, the yield of drilled coal occurs earlier and the yield platform is wider during creep loading. Also, the larger the borehole diameter, the deeper the borehole depth, and the lower the peak stress. The up dip angle is easier to destroy than the down dip angle. Compared with hard coal, soft coal produces greater deformation under smaller peak stress. The research results have guiding significance for drilling gas drainage in the soft coal seam. [ABSTRACT FROM AUTHOR]

The influence of grain size, in the range of 10 to 180 μm, on creep properties of 304HCu stainless steel (SS) was evaluated at 180 MPa and 923 K. A 30 μm grain size showed a peak in creep life and minimum in steady-state creep rate with low damage potential. Detailed microstructural investigations revealed an increase in the tendency to intergranular fracture at grain sizes above 30 μm, whereas 'transgranular fracture coupled with isolated intergranular cracks/cavities' have been observed with decreasing grain size from 30 to 10 μm. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of temperature variations on the creep and stress relaxation behavior of clay samples from London Bank Station. The independent and coupled effects of strain rate and temperature on one-dimensional (1D) stress–strain and stress relaxation responses were investigated based on a series of temperature-controlled constant rate of strain (CRS) compression–relaxation tests carried out at fast, intermediate, and slow displacement rates and over 20°C–55°C. The temperature effect on the creep index (Cα) was investigated based on a series of temperature-controlled multistage loading (MSL) oedometer tests. The results of the CRS compression–relaxation tests showed that with the increase in temperature, the coefficient of stress relaxation (Rα) decreases for samples that were loaded at fast and intermediate prerelaxation displacement rates (υ˙); however, it increases for samples loaded at the slow prerelaxation displacement rate. A decrease in υ˙ by a factor of 10 (i.e., from 0.010 to 0.001 mm/min) causes the Rα values to reduce by 55%–11% with the temperature increase. The increase in temperature caused an increase in Cα that were obtained from the MSL tests. The maximum value of Cα increased by 18% from 35°C to 45°C and by 37% from 45°C to 55°C. The temperature effects on other conventional parameters that included the preconsolidation pressure, and the compression and swelling indexes (Cc and Cs) were comparable with the findings reported in the literature. Comparing Cα that were obtained from the MSL tests and Rα that were obtained from the CRS tests supports the validity of Rα=Cα/Cc correlation for thermally influenced saturated reconstituted clays and that the time-dependent soil parameters could be obtained from relatively fast CRS compression–relaxation tests as an alternative to conventional time-consuming oedometer tests. [ABSTRACT FROM AUTHOR]

The thermal-mechanical response of the anode-supported planar solid oxide fuel cell (SOFC) during sintering is important for its manufacturing and in-service operation. The integrated micro/nano-indentation and finite element (FE) modeling method was used to characterize the Young's modulus, yield stress and creeping for the NiO-3YSZ anode and 8YSZ electrolyte at room temperature. Based on the real-time full-field deformation of the half-cell SOFC which was measured using the 3D digital image correlation (DIC), the FE simulation was used to estimate the stress response in a manner of sensitivity study. It shows that the half-cell SOFC warps towards the anode substrate during heating and points in the opposite direction during cooling. The warping deformation of FE simulation matches well with the DIC measurement. In addition, the maximum tensile stress in the electrolyte coat of the half-cell SOFC plate is about 207 MPa if assuming temperature-independence of creeping for the SOFC materials. • Real-time full-field displacement of the half-cell SOFC during sintering is measured. • The mechanical properties of the NiO-YSZ and 8YSZ materials are characterized. • The relation of creeping with the stress state of the FE analysis is validated experimentally. • The difference of creeping at 1200 °C for NiO-YSZ and 8YSZ is characterized. • The stress response during sintering and cooling is estimated, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Computational Mechanics / Jisuan Lixue Xuebao is the property of Chinese Journal of Computational Mechanics Editorial Office, Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effects of oxygen content on the microstructure and creep properties of the FGH96 superalloy were investigated. When oxygen content increased from 135 ppm to 341 ppm, the prior particle boundary (PPB) rose from degree 2 to degree 3, the size of the γ′ phase on PPB enlarged from 1.07 μm to 1.27 μm, and the MC carbide size grew from 77.4 nm to 104.0 nm. Meanwhile, the steady creep rate accelerated from 4.34 × 10−3 h−1 to 1.87 × 10−2 h−1, and the creep rupture life shortened from 176 h to 94 h, the creep rupture mode transferred from intergranular and transgranular mixed fracture to along PPB fracture. During creep, the micro-twin formation and gliding will be restrained by ∑3 boundaries. FGH96 superalloy with higher oxygen content contains less ∑3 boundaries, and its micro-twins cross-slipped instead of single-direction slip in lower oxygen content superalloy. Consequently, samples with a higher oxygen content crept faster and ruptured earlier. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

During the 2021 La Palma strombolian and fissure eruption, two faults were identified that controlled the spatial distribution of earthquake hypocenters and effusive eruptive vents. One of these faults has a NW-SE trend (Tazacorte Fault: TZF) and the other one shows an ENE-WSW trend (Mazo Fault: MZF). Previous works on fault structural analysis in La Palma indicated that the eruption zone was compatible with an extensional tectonic strain ellipsoid which activated normal-strike-slip directional faults at the confluence of TZF and MZF. These fractures were activated during the 2021 Tajogaite eruption, determining the NW-SE and WSW-ENE spatial distribution of vents. Both faults were mapped in real time during the volcanic eruption from fieldwork and remote sensing imagery (aerial drone images). We have collected more than 300 fracture data associated with the effusive vents and post-eruption seismic creep. Since the affected area was densely inhabited, most of these fractures affect houses and infrastructures. Some of the houses affected by the TZF were damaged 9 months after the eruption, although they were not damaged during the eruption. Surprisingly, these houses already had repairs made to the same fractures since 1980, giving information of previous fault creep movement. During the 2021 Tajogaite eruption, shallow seismicity was spatially related to both faults, suggesting a seismic behavior instead of the precedent creep movement. However, the lack of seismicity after the eruption indicates that the faults went back to creep aseismic behavior, similarly to 1980. The mapping and monitoring of these faults (TZF and MZF) is relevant bearing in mind that they have been active since 1980 and the post-eruptive phase of the 2021 volcanic eruption, which has to be included in the land use planning in areas affected by the volcanic eruption and creep movement. Furthermore, both faults could act as seismogenic sources triggering volcanic earthquakes with potential high macroseismic intensities and mass movements. The data presented here show the importance of having this type of study before the onset of the eruption, thus allowing a better interpretation of seismic data during volcanic unrest. [ABSTRACT FROM AUTHOR]

Modifying the microstructure of the IN738 superalloy increases the working efficiency of gas turbine blades. In this study, the microstructure of IN738 superalloy processed by selective laser melting was improved by applying a magnetic field and adding TiC nanoparticles. The results show that the application of a magnetic field by crushing the solidifying grains and the addition of TiC by creating places for the heterogeneous nucleation of the melt causes a remarkable expansion of the equiaxed grains. However, the simultaneous application of a magnetic field and TiC nanoparticles significantly reduces the grain size, grain aspect, and, consequently, the crack density and porosity. Also, the results showed that with the reduction of grain ratio, high-angle grain boundary and grain boundary length density increase dramatically, which results in a decrease in the concentration of elements and phases sensitive to cracking in grain boundaries. The increase in the volume fraction and the reduction in the γ' size were other effects of adding TiC and the external field, which significantly improved the creep and wear behavior. So, with the expansion of the equiaxed region, the hardness increased, and the wear resistance increased through the delay in the transition from the elastic area to the plastic area during the wear test. [ABSTRACT FROM AUTHOR]

The authors propose a mathematical model of shell structures taking into account the linear theory of hereditary material creep. This model is based on the total potential strain energy functional. Shells are reinforced with stiffeners, and the contact between the stiffener and the shell skin along a strip is taken into account. The Ritz method is applied to the functional, and a system of algebraic or integro-algebraic equations is found. The resulting system is first solved as a linear system (without account for the terms reflecting material creep), and the state of the structure under the specified load is determined. Then the iterative method is used to solve the creep problem for a given value of time. The paper presents the results of studying stiffened shallow shells of double curvature made of reinforced concrete under uniformly distributed load. The buckling of shells occurs over time as a result of the development of creep strains. Values of the buckling load as a result of material creep are found. It is shown that stresses are redistributed over the shell field over time and the maximum stress is observed near the contour of the structure. [ABSTRACT FROM AUTHOR]

Structural adhesives characterized a turning point in the post-connection of structural elements due to their excellent performances and ability to transfer stress without losing their integrity. These materials are typically particle-reinforced composites made by a thermoset polymer matrix and fillers. During the in-situ application of this material, the thermal activation of the polymer is typically not possible, leading to an undefined degree of cure and therefore to a variation of the mechanical performance over time. This altering means that after applying a sustained load on a bonded anchor system installed at regular temperature, the adhesive changes material properties. Ample studies convince that the progressive increase of the degree of cure of the thermosetting polymer leads to higher strength and stiffness. However, limited studies have been dedicated to the post-curing effects on the long-term behavior. The main goal of this work is to investigate the tensile and shear creep behavior of two commercially available structural adhesives and the influence of curing conditions on their long-term performances. An extensive experimental campaign comprising short and long-term characterizations has been carried out on specimens subjected to three different curing and post-curing protocols, with the scope of imitating relevant in-situ conditions. The results demonstrate that structural adhesives cured at higher temperatures are less subjected to creep deformations. As a material equation, the generalized Kelvin model is utilized to fit the tensile and shear creep data, and two continuous creep spectra have been selected to represent the creep behavior and facilitate extrapolations to the long-term behavior. [ABSTRACT FROM AUTHOR]

Vitrimer materials have attained great interest owing to their sustainable functions and distinctive physical properties. Compared with conventional cross‐linked materials, the thermoplastic‐like nature, such as the stress relaxation and creep at high temperatures, is outstanding, which is owing to the activation of the bond exchange in the cross‐linked network. The activation temperature of the bond exchange, so‐called topology freezing temperature (Tv), are treated as the important material parameters, and non‐isothermal (i.e., temperature‐ramp) creep test is one of the method to determine the Tv. This study investigates effects of network defects, that is, the breaking point of network connectivity, on the creep and Tv. The transesterification vitrimer samples with varying fraction of the network defects are designed using thiol‐epoxy click reaction, where the overall fraction of the bond exchange units, that is, the ester bond and hydroxyl group, is kept constant. Non‐isothermal creep tests are conducted with varying temperature‐ramp rate and applied stress levels, and the difference of Tv and creep behaviors at T > Tv are discussed in terms of network strand diffusion during bond exchange and chain elongation under stress. [ABSTRACT FROM AUTHOR]

In recent years, the depth of oil drilling has exceeded 9000 m, and the testing and evaluation of mechanical properties of ultra-deep rocks face great challenges. Obtaining complete core samples has lots of serious problems through ultra-deep drilling, so it is difficult to process standard rock samples for general tests to obtain the mechanical properties. In order to study the creep behaviour of deep rocks, we conducted continuous step holding nanoindentation creep experiments on carbonate rocks from the Tarim Oilfield in Xinjiang, China. We first investigated the effects of load and holding time on the creep behaviour; Furthermore, by calculating the stress exponent, the deformation mechanism is revealed; At last, four traditional creep models and fractional order Maxwell model were used for regression to explore the applicability of models in describing the creep behaviour. The results show the creep displacement is positively correlated with the load and holding time. Creep curves with different shapes were obtained in nanoindentation (named A1 and A2 respectively). The Burgers and the two-dashpot Kelvin model are in good agreement with experimental data under long holding time. The stress exponents of A2 are greater than 3, indicating that the creep mechanism of A2 is dislocation creep. [ABSTRACT FROM AUTHOR]

This article addresses the often overlooked but critical long-term factors of creep, shrinkage, ageing and corrosion in civil engineering structures. The paper emphasizes their substantial impact on structural mechanical resistance and safety, drawing attention to key examples like the Civic Tower in Pavia, the Koror-Babeldaob Bridge and dams in the USA. By exploring the challenges faced in modern engineering, the article sheds light on the need to consider these effects. Various models for predicting creep and shrinkage in concrete structures are introduced as potential solutions. In conclusion, the paper highlights the necessity for engineers to navigate the intricacies of material behaviour for successful construction amidst evolving challenges. [ABSTRACT FROM AUTHOR]

In this research work, the creep of thick-walled cylindrical vessels made of FGM with autofrettaged-treated was investigated using the analytical method. At different plastic depths and a variety of internal pressures for elastic modulus and yield stress constants (n 1 and n 4), changes in residual creep strain rate (radial and circumferential) and final creep strain rate are investigated. The obtained results show that the circumferential stresses in the autofrettage have different values depending on the depth of the plastic. In the equivalent stress diagram, the resulting stress at the plastic points of the vessel reaches the yield stress of the FGM, and the stress decreases along the radius. If p ¯ is increased from 1 to 1.8, the maximum creep strain rate decreases (for several n 4, the dimensionless plastic depth is equal to 1.8). The results show that up to a dimensionless plastic depth of 1.5, the change in residual strain rate is negligible. The slope of the graphs for the dimensionless depths above 1.6 increases sharply. A comparison of the maximum circumferential stress as a function of plastic depth for the present work and the study by Darijani shows very good agreement between the two studies. [ABSTRACT FROM AUTHOR]

The benefits of using glued laminated bamboo (GLB) as a structural material are numerous, such as its low weight, high specific strength, and low carbon footprint. However, as a viscoelastic material, GLB materials exhibit creep, which is a significant characteristic that needs to be considered. To ensure the safety and serviceability of structures that utilize GLB, it is essential to accurately estimate the long-term performance of GLB composites under external forces. This paper reports on an experimental investigation into the creep characteristics of GLB under tensile and compressive loads. The experiments were conducted at various load levels for a period of 500 h under a controlled environmental condition. The Burgers model and the five-parameter model were used to characterize creep behavior and predict the long-term deformation by extrapolating beyond the experimental period. The long-term deformation of the GLB may be overestimated by the Burgers model due to its constant creep rate for the viscous component. In contrast, the five-parameter model introduces a modification factor that results in a nonlinear viscous component, allowing a more accurate fit and a reasonable deformation estimate. Highlights • Creep characteristics of GLB were studied under tensile and compressive loads. • Burgers and five-parameter models were used to describe the creep behavior. • Extrapolation of Burgers model overestimates the creep deformation of GLB. • Five-parameter model provides reasonable deformation estimate for GLB. [ABSTRACT FROM AUTHOR]