Dependence Of Strength Research Articles

Size effect and plastic deformation mechanisms of AlON micro/nanopillars with different crystallographic orientations

In this work, the plastic deformation of micro/nanoscale AlON ceramic pillars with different crystallographic orientations was investigated by in situ compression on scanning electron microscopy (SEM) system. The experimental results demonstrated a "smaller is stronger" size dependence of the yield strength of <100>-, <110>- and <111>-oriented AlON micro/nanopillars with scaling exponents of −0.19, −0.24 and −0.33, respectively. Transmission electron microscopy (TEM) illustrated that the Lomer-Cottrell dislocation reaction dominated the plastic deformation of <111>-oriented pillars. The plastic deformation of <110>-oriented AlON pillars was driven by rotation of the slip region, whereas the stress of <001>-oriented pillars were released through microcracks and plastic deformation.

Hydration, strength, and microstructure evolution of Portland cement-calcium sulphoaluminate cement-CSH seeds ultra-early strength cementitious system

Improving the very early age strength of precast concrete components at ambient temperature and ensuring the development of later strength is of significant engineering importance. This objective was successfully achieved by incorporating a specific percentage of 0–3% CSH seeds (CSHs) and 5%-20% calcium sulphoaluminate cement (CSA) into Portland cement (PC). The hydration, strength and microstructure evolution of Portland cement-calcium sulphoaluminate cement-CSH seeds cementitious system were investigated. Hydration heat tests reveal that CSHs effectively accelerated the early hydration of the slurry within the first 12 h without affecting its later hydration. CSHs and CSA acted synergistically to enhance hydration kinetics. However, it is crucial to control the proportion of CSA within the range of 5%-10%; exceeding this ratio can severely inhibit the hydration of silicates. Strength tests indicate that the addition of CSHs and CSA can increase the compressive and flexural strengths of mortar within the first 12 h by 282% and 208%, respectively, without impacting the development of its later-age strength. Together, they synergistically provide favorable support for the strength and toughness of matrix. Based on linear regression analysis and nitrogen adsorption and desorption tests, it was concluded that CSHs enhance the hydration dependence of matrix strength, while CSA diminishes this characteristic. This is because CSHs refine the pore size distribution of the paste, increasing the proportion of micropores, whereas CSA promotes the formation of more mesopores and macropores, leading to coarser pores; however, 5% CSA is beneficial for further refining the pore structure. The microcosmic phase evolution of the early-strength cementitious system was analyzed through X-ray diffraction and scanning electron microscope-energy dispersive spectrometer experiments. Results demonstrate that low proportions of CSA and CSHs promote the co-growth of ettringite and C-S-H gel, ensuring a more rapid formation of a dense hydration network in the early stages, thereby accelerating strength development. These findings provide a reference for the design and preparation of precast concrete.

Study on irradiation effect of insulating materials for fusion superconducting magnets: temperature dependence of mechanical strength

Insulating materials used in the superconducting magnets of fusion reactors are exposed to cryogenic temperatures, intense radiations, and strong electromagnetic forces. In the experimental fusion reactor ITER, resin mixed with epoxy resin (EP) and cyanate ester (CE) (CE content: 40 wt.%) is used as a matrix of glass reinforced plastics (GFRP) as an insulating material to maintains mechanical strength and insulating performance in such environments. This composition ratio is basically determined by strength tests at room temperature or liquid nitrogen temperature, so the study at liquid helium temperature is required. In this study, the effects of the resin composition of GFRP on interlaminar shear stress (ILSS) at room temperature, liquid nitrogen temperature, and liquid helium temperature before and after γ-ray irradiation were evaluated. The ILSS after γ-ray irradiation of EP showed a maximum value at liquid helium temperature, while the addition of CE caused the ILSS after irradiation to show a maximum value at liquid nitrogen temperature. It was also shown that the temperature dependence of the ILSS decreased with increasing CE content. The results showed that the addition of CE to EP contributes to the improvement of radiation resistance, but excessive addition of CE promotes embrittlement at LHeT.

Dynamic shear behaviours of granite under coupled static and high-rate loadings

Understanding dynamic shear behaviours of rock under quasi-static confinement and dynamic loads is not only of great importance in underground engineering structures, but also beneficial to reveal earthquake mechanics regarding pre-stressed rocks fracturing from initial intact to rapid shear sliding. Here we propose a dynamic shear test setup and present full-field observations of stressed rock failure at high shear rate (up to γ˙ = 220 s−1) and sliding at high slip velocity over 10 m/s in the order of coseismic slip, with the integration of a novel triaxial Hopkinson bar (Tri-HB) and high-speed three-dimensional Digital Image Correlation (3D-DIC) techniques. Dynamic shear strength and friction coefficient are determined during the dynamic shear test under confinement, with different shear strain rates and pre-stresses. The dynamic shearing process can be divided into three stages, i.e. shear deformation, fracture degradation and dynamic frictional sliding. The high energy density of shear fracture band is observed, the rate and stress state dependences of rock shear strength and dynamic frictional coefficient are revealed. The dynamic shear strength of granite follows the Mohr-Coulomb criteria under varying pre-stresses and strain rates. The gouge materials with size of 1∼10 μm are generated within the high-rate shearing zone, and this appears to control the frictional resistance. The results could help determination of rock shear strength and post-shear failure, as well as explain the shear rupture and the resistance to slip mechanism of rock faults and strong near-surface earthquake events.

Crystal Plasticity Finite Element Analyses on the Formability of AA6061 Aluminum Alloy with Different Ageing Treatments

Different ageing treatments have been developed to achieve targeted properties in aluminum alloys through altering microstructures. However, there is a lack of understanding regarding the effect of ageing treatments on the formability of these alloys. In this study, we employed crystal plasticity finite element (CPFE) modeling, in conjunction with the Marciniak-Kuczynski (M-K) approach, to investigate the effects of ageing treatments on the mechanical properties and formability of AA6061 aluminum alloy. The as-received sheet was in the T6 heat treatment state, which was subjected to artificial ageing and pre-ageing, respectively, to achieve two age-hardened alloys with modified precipitation states. The microstructures and crystallographic textures of the three alloys were measured using the electron backscattering diffraction (EBSD) technique, and uniaxial tensile tests were performed along the rolling direction (RD), transverse direction (TD), and diagonal direction (DD, 45° to the RD) for each alloy. The forming limit curve (FLC) of the as-received alloy was determined using the Nakazima test. The dependence of mechanical strength, tensile ductility, and work-hardening behavior on the ageing treatments was clarified. Then, the tensile test results were utilized to calibrate the modeling parameters used in the CPFE model, whereas the FLC predictability of the developed model was validated with the experimental one. In the formability analysis, the effects of the ageing treatment on the FLC exhibit a notable dependency on loading paths, and the pre-aged alloy exhibits better formability than the other two at the plane strain tension state, thanks to its high work-hardening levels. In addition, the deformed textures along the different loading paths and the effects of the initial texture on the FLC are also discussed.

Effect of padeye offset ratio on keying behaviours and capacity of square plate anchors in clay

This paper reports the effect of padeye offset ratio on the keying behaviours and capacity of square plate anchors in clay. The investigation is conducted through three-dimensional large deformation finite element analyses using the Remeshing and Interpolation Technique with Small Strain in ABAQUS. Strain rate dependency of the undrained shear strength and soil remoulding are accounted for adopting an extended Tresca model. The results from LDFE analyses are compared with existing analytical solutions, centrifuge test data, and numerical results; with reasonable agreement obtained. Parametric analyses are then carried out varying several critical factors including initial embedment depth, load eccentricity, padeye offset ratio, soil sensitivity, and soil strength heterogeneity. It is seen that the padeye offset has significant influence on the ultimate loss of embedment and capacity under vertical loading. To assess the keying behaviour of square plate anchors in clay, an equivalent soil strength incorporating strain rate dependency and remoulding is adopted. A combined factor defined as a function of the initial embedment depth and equivalent soil strength is used to estimate the ultimate loss of embedment. An equivalent ultimate bearing capacity factor is shown to be a function of the initial embedment depth, padeye offset ratio, and load eccentricity.

Thermal conditions in the marine coastal waters as a factor favorable for formation of extra-strong year-classes of Karaginsky pink salmon

Variability of the timing for downstream migration of juvenile pink salmon from the Hailulya River to the adjacent coastal waters of Karaginsky Bay is considered and influence of the coastal water temperature on strength of the year-classes for two generative lines of pink salmon spawning in the Karaginsky Bay is analyzed for 1978–2020. The optimal conditions for the downstream migration in the period after 2002 are determined as the mean weighted per migration intensity water temperature &gt; 5.6 o C (up to 7.8 о С on average with the maximum 9.9 о С in some years) and a stable increasing of the temperature during migration. The factor of food availability for juveniles became less important for formation of the Karaginsky pink salmon year-classes since the late 2000s, in comparison with the temperature. Statistical model is proposed for the year-class strength dependence on the temperature of coastal waters in late June and the parents number (R2 = 0.791). The modeled hindcasts of the pink salmon returns in 2021–2023 were rather satisfactory. Given these new results, the limits of pink salmon escapement to spawning grounds could be reconsidered and fishery management models should be adjusted to modern conditions of unrestricted juvenile feeding to get and rationally exploit super-strong year-classes of this species.

Analytical 3D failure envelopes for RC pile groups under combined loading: A generalised design approach

The paper presents a generalised design approach for pile groups subjected to combined (VHM) loading. The Limit Equilibrium method is extended to pile groups under general planar loading, considering the axial load dependency of bending stiffness and strength of reinforced concrete (RC) piles. 3D failure envelopes are analytically derived for different layouts. The key simplifying assumptions are critically discussed, and the failure envelopes are verified against finite element (FE) analysis results. Key features of pile group response, such as plunging vs. non-plunging axial pile response and the role of transverse reinforcement, are identified and quantified. A key novelty of the proposed method lies on the consideration of coupling between the lateral–bending resistance of the piles. The method further incorporates well-recognised features of pile group response regarding the axial load dependency of bending moment capacity and stiffness of the RC piles. The latter results in redistribution of bending moments and shear forces along the piles of the group. These features allow the reproduction of key aspects observed in demanding FE simulations and centrifuge tests, regarding the ultimate resistance under VHM and in addition the load path dependent failure modes. The proposed method offers a practical engineering tool for preliminary design and optimisation.

Nanoscale hydrate adhesion on organic surfaces

The future of addressing persistent gas hydrate blockages in oil and gas pipelines lies in the realm of surface material design, aimed at reducing environmental harm and energy inefficiencies associated with traditional chemical additives or heat-based approaches. A comprehensive understanding of hydrate-surface interactions is crucial for effective material-based solutions. Our study examined gas hydrate adhesion on diverse organic monolayer surfaces, utilizing Molecular Dynamics (MD) simulations to explore the impact of surface flexibility, gas concentration, and crack locations on hydrate adhesion strength. Results highlight the dependence of adhesion strength on surface functional groups. Hydrophobic interfaces are susceptible to weakening through a “gas coating”, while hydrophilic groups, like hydroxyl, strengthen adhesion through hydrogen bonding, altering the fracture behavior from adhesive failure to cohesive failure. Unexpectedly, the flexibility of monolayers has minimal influence, especially on hydrophobic surfaces. Tensile testing identified six distinct fracture interfaces, with the ice-hydrate interface displaying the highest adhesion strength, highlighting the detrimental impact of hydrogen bonding on interface weakening. These findings significantly deepen the understanding of soft surface properties influencing gas hydrate adhesion, offering a valuable guide for designing and fabricating highly efficient flexible anti-hydrate surfaces.

Effect of environment temperature on fatigue properties of laminated leather

In this study the influence of environment temperature on the mechanical properties (tensile strength and elasticity modulus at break) of laminated leather and its layers (split leather and microporous polyurethane (PU) Permair film) under fatigue flexing have been investigated. The testing was carried out by changing the temperature from 20 ± 2°C to −20 ± 2°C (number of cycles NC = 105). The experimental results showed that the character of the dependences of tensile strength and elasticity modulus at break on temperature of fatigue environment of both leathers is similar and significantly differ from characters of analogous dependences of microporous PU film. The defects on the surface of laminated leather become clearly visible when the temperature falls to ≤ -10°C.

A new method for predicting the fatigue strength at various stress ratios based on damage of metallic materials

AbstractThe prediction of fatigue strength for metallic materials in a wide range of stress ratios is a crucial engineering challenge. To pursue a more accurate method, the dependence of fatigue strength on stress ratio for 35CrMo steel and other materials was investigated in detail. It was found that as the stress ratio increases, the damage mechanism changes, and the errors of the conventional models in predicting the fatigue strength increase. The reason is that those models fail to describe the fatigue damage evolution of metallic materials under some special conditions. Based on the variational fatigue damage, a new prediction method was proposed by introducing the damage parameter. Through the validation with fatigue strength covering a variety of metallic materials and loading conditions, the method exhibits higher universality. And then the corresponding parameter of the formula is further analyzed to elucidate the influences of various loading conditions on fatigue damage of materials.

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ ПРОЧНОСТНЫХ СВОЙСТВ ЛЁССОВ МЕТОДОМ КОРРЕЛЯЦИОННО-РЕГРЕССИОННОГО АНАЛИЗА

The strength properties of subsiding loess soils are considered in the mathematical modeling of their compaction by deep explosions. Soil compaction is carried out in order to eliminate their subsidence properties. Correlation and regression analyzes of the dependences of strength on the physical characteristics of loess were carried out, using the soils of the North Caucasus as an example. The correlation dependence of the specific cohesion and the angle of internal friction on the physical characteristics of the subsidence soil is established. Correlation coefficients were obtained for various indices of moisture content and loess density. The studies were carried out before and after soil compaction in this way. Both positive and negative correlations between the studied characteristics of subsiding loess soil were recorded. With an increase in moisture, a high correlation was observed with the strength characteristics of the soil before and after its compaction by deep explosions. The equations of regression of specific cohesion and the angle of internal friction on soil moisture and density are constructed. The reliability coefficients of approximation of theoretical regression equations and experimental data demonstrate high values. The regression equations of specific adhesion and the angle of internal friction on soil moisture showed that the values of strength characteristics increase with decreasing values of soil moisture. The regression dependence of the specific cohesion and the angle of internal friction on the density of subsidence loess has been studied. It has been established that an increase in the values of strength characteristics was recorded with an increase in the density of loess soil before and after its compaction by deep explosions. The constructed regression equations make it possible to predict the strength characteristics of loess at the stage of designing the bases and foundations of construction objects.

Frequency-dependent ferroelectric and electrocaloric properties in barium titanate-based ceramics based on Maxwell relations

In this work, the frequency dependence of ferroelectric and electrocaloric properties in barium titanate-based ceramics was studied based on Maxwell relations. It is found that the maximum and remnant polarization will decrease while the coercive field increases a lot with rising frequency from 0.1 to 10[Formula: see text]Hz, indicating that polarization rotation and domain switching become difficult at high frequencies. The electrocaloric properties show the different frequency dependence at different phase structures. Isothermal entropy change ([Formula: see text]) and adiabatic temperature change ([Formula: see text]) are similar around/above Curie temperature ([Formula: see text], showing tiny frequency dependence. However, [Formula: see text] and [Formula: see text] display the obvious frequency dependence below [Formula: see text], especially in the orthorhombic–tetragonal phase-transition region with a stable ferroelectric phase, and this frequency dependence becomes more obvious under a low-electric field. It is also found that increasing the frequency can weaken the electric field dependence of electrocaloric strength. This work gives a general profile of frequency dependence for electrocaloric properties in ferroelectric ceramics.

Effect of strain rate on the in-plane orthotropic constitutive response and failure behaviour of a unidirectional non-crimp fabric composite

A comprehensive experimental campaign was performed to characterize the strain rate-dependent orthotropic constitutive response and failure behavior of a unidirectional non-crimp fabric (UD-NCF) carbon fiber/snap-cure epoxy composite. Shear and transverse compression strengths increased by 60% and 50%, respectively, over the range of strain rates considered, which is consistent with previously reported trends for unidirectional tape composites (UDTCs). The transverse tension strength increased by 18% with increasing strain rate, which is different from UDTCs. Owing to the distinct microstructure of UD-NCF composites, local damage mechanisms such as pullout of transverse supporting glass fibers and stitching were observed and are deemed to contribute to the rate dependency of transverse tension strength. The longitudinal compression strength increased by 35% with increasing strain rate. Observation of failed specimens revealed widespread inter-tow axial splitting and localized tow kinking, distinct from UDTCs. This important finding will aid in the development of failure criteria for UD-NCF composites.

Experimental Study on the Accelerating Creep of Rock Under Dry and Wet Conditions Based on a New Test Method

Creep tests under constant stress are among the most important tests for investigating the time-dependent behavior of rock. In previous studies, creep tests were conducted under various loading and environmental conditions; however, it was very difficult to demonstrate accelerating creep at failure at stresses less than 50% of strength in conventional creep tests. In this study, a new test method is proposed that combines an alternating loading-rate test and a creep test in the post-failure region. The accelerating creep as well as the loading-rate dependence of strength were successfully obtained simultaneously from a single specimen. This test method was applied to three rock types under dry and wet conditions. The results of Sanjome andesite under both dry and wet conditions, Kimachi sandstone under dry conditions, and Tage tuff under dry conditions showed a similar relationship between creep strain, creep strain rate, and residual time (i.e., creep lifetime minus elapsed time), from high to low creep stress levels, and a close relationship between accelerating creep and the loading-rate dependence of strength. Further, the mechanism responsible for the time dependence was found not to change significantly from high to low stress levels. In contrast, different results were obtained when high and low creep stress levels were compared in Kimachi sandstone and Tage tuff under wet conditions. The larger increase in creep strain with increasing creep strain rate at lower creep stress levels was related to the shape of the stress–strain curve in the post-failure region.

Probing the magnetic field strength dependence of the chiral magnetic effect

The article presents a study aimed at probing the dependence of the Chiral Magnetic Effect (CME) on the magnetic field strength using the Anomalous Viscous Fluid Dynamics (AVFD) model in Pb–Pb at LHC energies. The results demonstrate the quadratic dependence of the correlators used for the study of the CME in heavy ion collisions on the number of spectators, a proxy of the magnitude of the magnetic field. The article also presents the extension of this approach to a two dimensional space, formed by both the aforementioned proxy of the magnetic field strength but also a proxy of the final state ellipticity, a key ingredient of the background in these measurements, for each centrality interval. This provides an exciting possibility to experiments to isolate the background contributions from the potential CME signal.

Annealing-temperature dependence of adhesion strength of hydroxyapatite layers coated on zirconia substrates by droplet elimination pulsed-laser deposition scheme

High-purity, high-crystallinity hydroxyapatite coatings on zirconia substrates were successfully fabricated at annealing temperatures >360 °C. The coatings did not dissolve in vivo within a short period and enhanced the formation of new bone. If the coating layer physically adheres to the zirconia substrate, strong bonding is expected on the coating layer. The adhesion strength of the coating layer was measured using an oscillation-type micro-scratch test. The adhesion strength was found to increase with increasing substrate surface temperature during deposition, irrespective of whether an in situ annealing process or a post-annealing process was used. These results indicated that the proposed coating layer will survive for a prolonged period in vivo and enable strong bone bonding with medical implants.

Terahertz sum-frequency excitation of coherent optical phonons in the two-dimensional semiconductor WSe2

Driving fundamental excitations via strong light fields is one of the most important issues in solid state physics, which opens up new avenues to control material properties. Two-dimensional materials are fruitful platforms for future semiconductor applications, including opto-electronic and phononic devices, yet the phonon dynamics and nonlinear phonon–phonon coupling remain under-explored. Here, we demonstrate coherent phonon excitation in thin films of the layered two-dimensional semiconductor WSe2 induced by intense and broadband ultrafast terahertz (THz) pulses. We performed THz Kerr effect spectroscopy and observed coherent phonon oscillations assigned to the E2g optical phonon mode. The phonon amplitude displays a quadratic THz field strength dependence, indicating a sum-frequency THz excitation process. Furthermore, pump–probe polarization and crystal orientation relationships, supported by symmetry analysis of the nonlinear susceptibility and Raman tensors, provide helpful insight into nonlinear phonon–phonon interactions and potential coherent control schemes for the manipulation of phonon polarization and material properties in WSe2.

Effects of grain magnetic properties and grain growth on synthetic dust polarization of MHD simulations of low-mass Class 0/I YSOs

ABSTRACT Thermal dust polarization is a powerful tool to probe magnetic fields ($\boldsymbol{B}$) and grain properties. However, a systematic study of the dependence of dust polarization on grain properties in protostellar environments is not yet available. In this paper, we post-process a non-ideal MHD simulation of a collapsing protostellar core with our updated POLARIS code to study in detail the effects of iron inclusions and grain growth on thermal dust polarization. We found that superparamagnetic (SPM) grains can produce high polarization degree of $p \sim 10\!-\!40~{{\ \rm per\ cent}}$ beyond ∼500 au from the protostar because of their efficient alignment by magnetically enhanced radiative torque mechanism. The magnetic field turbulence in the envelope causes the decrease in p with increasing emission intensity I as p ∝ Iα with the slope α ∼ −0.3. But within 500 au, SPM grains tend to have inefficient internal alignment and be aligned with $\boldsymbol{B}$ by RATs only, producing lower $p \sim 1~{{\ \rm per\ cent}}$ and a steeper slope of α ∼ −0.6. For paramagnetic (PM) grains, the alignment loss of grains above $1\, {\mu \rm {m}}$ in the inner ∼200 au produces $p \lt \lt 1~{{\ \rm per\ cent}}$ and the polarization hole with α ∼ −0.9. Grain growth can increase p in the envelope for SPM grains, but cause stronger depolarization for SPM grains in the inner ∼500 au and for PM grains in the entire protostellar core. Finally, we found the increase of polarization angle dispersion function S with iron inclusions and grain growth, implying the dependence of B-field strength measured using the David–Chandrasekhar–Fermi technique on grain alignment and grain properties.

Anomalous strain rate dependence of ultra-low temperature strength and ductility of an electron beam additively manufactured near alpha titanium alloy

The strain rate (ε˙) dependence of ultra-low temperature strength and ductility was investigated systematically on a cryogenic near alpha titanium alloy Ti-3Al-3Mo-3Zr-0.2Y additively manufactured by electron beam selective melting (EBSM). As ε˙ increases under quasi-static tension at 77 and 20 K, ductility monotonically decreases when yield strength (YS) keeps ascending. As ε˙ increases from 5.6 × 10–4 s−1 once by one order of magnitude, elongation-to-fracture declines from 20.0 % to 16.5 % and 15.7 % at 20 K. However, unlike the regular monotone increase at 298 and 77 K, ultimate tensile strength (UTS) at 20 K rises to 1460 MPa first then drops to 1320 MPa. This study further examined how strain rate affects slipping, twinning and strain hardening behavior. The monotone increase in YS is primarily attributed to the increased CRSS for slips and the enhanced tendency of pyramidal 〈a〉 and 〈c + a〉 slipping and <101¯0 > 34° twinning at 20 K. On the other hand, the monotone decrease of ductility is essentially ascribed to the intensified deformation localization characterized by micro shear bands, multiple necking and single necking. More importantly, the mechanisms of abnormal UTS variation and disappearance of serration flow at 20 K are discussed in terms of strain hardening levels, degree of shear deformation localization and the interaction of slips and twins. This study provides deep insights into strain rate effect on cryogenic mechanical behavior of EBSM-built titanium alloy.