Bending Failure Mode and Prediction Method of the Compressive Strain Capacity of A Submarine Pipeline with Dent Defects

A dent is a common type of defects for submarine pipeline.For submarine pipelines,high hydrostatic pressure and internal pressure are the main loads.Once pipelines bend due to complex subsea conditions,the compression strain capacity may be exceeded.Research into the local buckling failure and accurate prediction of the compressive strain capacity are important.A finite element model of a pipeline with a dent is established.Local buckling failure under a bending moment is investigated,and the compressive strain capacity is calculated.The effects of different parameters on pipeline local buckling are analyzed.The results show that the dent depth,external pressure and internal pressure lead to different local buckling failure modes of the pipeline.A higher internal pressure indicates a larger compressive strain capacity,and the opposite is true for external pressure.When the ratio of external pressure to collapse pressure of intact pipeline is greater than 0.1,the deeper the dent,the greater the compressive strain capacity of the pipeline.And as the ratio is less than 0.1,the opposite is true.On the basis of these results,a regression equation for predicting the compressive strain capacity of a dented submarine pipeline is proposed,which can be referred to during the integrity assessment of a submarine pipeline.

Acetic acid-assisted mild dealloying of fine CuPd nanoalloys achieving compressive strain toward high-efficiency oxygen reduction and ethanol oxidation electrocatalysis

Dealloying by which the transition metal is partially or completely leached from an alloy precursor is an effective way to optimize the fundamental effects for further enhancing the electrocatalysis of a catalyst.Herein,to address the deficiencies associated with the commonly used dealloying methods,for example,electrochemical and sulfuric acid/nitric acid treatment,we report an acetic acid-assisted mild strategy to dealloy Cu atoms from the outer surface layers of CuPd alloy nanoparticles to achieve high-efficiency electrocatalysis for oxygen reduction and ethanol oxidation in an alkaline electrolyte.The leaching of Cu atoms by acetic acid exerts an additional compressive strain effect on the surface layers and exposes more active Pd atoms,which is beneficial for boosting the catalytic performance of a dealloyed catalyst for the oxygen reduction reaction(ORR)and the ethanol oxidation reaction(EOR).In particular,for ORR,the CuPd nanoparticles with a Pd/Cu molar ratio of 2:1 after acetic dealloying show a half-wave potential of 0.912 V(vs.RHE)and a mass activity of 0.213 AmgPd^(-1) at 0.9 V,respectively,while for EOR,the same dealloyed sample has a mass activity and a specific activity of 8.4 Amg^(-1) and 8.23 mA cm^(-2),respectively,much better than their dealloyed counterparts at other temperatures and commercial Pd/C as well as a Pt/C catalyst.

Influence of compressive strain on the incorporation of indium in InGaN and InAlN ternary alloys

In order to investigate the influence of compressive strain on indium incorporation in In Al N and In Ga N ternary nitrides, In Al N/Ga N heterostructures and In Ga N films were grown by metal–organic chemical vapor deposition. For the heterostructures, different compressive strains are produced by Ga N buffer layers grown on unpatterned and patterned sapphire substrates thanks to the distinct growth mode; while for the In Ga N films, compressive strains are changed by employing Al Ga N templates with different aluminum compositions. By various characterization methods, we find that the compressive strain will hamper the indium incorporation in both In Al N and In Ga N. Furthermore, compressive strain is conducive to suppress the non-uniform distribution of indium in In Ga N ternary alloys.

Towards efficient strain engineering of 2D materials:A four-points bending approach for compressive strain

Strain engineering,as a powerful strategy to tune the optical and electrical properties of two-dimensional(2D)materials by deforming their crystal lattice,has attracted significant interest in recent years.2D materials can sustain ultra-high strains,even up to 10%,due to the lack of dangling bonds on their surface,making them ideal brittle solids.This remarkable mechanical resilience,together with a strong strain-tunable band structure,endows 2D materials with a broad optical and electrical response upon strain.However,strain engineering based on 2D materials is restricted by their nanoscale and strain quantification troubles.In this study,we have modified a homebuilt three-points bending apparatus to transform it into a four-points bending apparatus that allows for the application of both compressive and tensile strains on 2D materials.This approach allows for the efficient and reproducible construction of a strain system and minimizes the buckling effect caused by the van der Waals interaction by adamantane encapsulation strategy.Our results demonstrate the feasibility of introducing compressive strain on 2D materials and the potential for tuning their optical and physical properties through this approach.

Sub-2 nm IrO_(2)/Ir nanoclusters with compressive strain and metal vacancies boost water oxidation in acid

IrO_(2)exhibits good stability but limited electrocatalytic activity for oxygen evolution reaction in acid.Defect engineering is an effective strategy to improve the intrinsic ability of electrocatalysts by tailoring their electronic structure.Herein,we have successfully synthesized IrO_(2)/Ir heterophase with compressive strain and metal vacancies via a simple substitution-etching method.In virtue of the solubility of Cr in strong alkali,metal vacancies could be formed at surface after etching Cr-doped IrO_(2)/Ir in alkali,which leaded to modulated electronic structure.Meanwhile,the substitution of Cr with smaller atom radius would induce the formation of compressive strain and the relocated atoms made the d-band center shifted.With the regulated electronic structure and tuned d-band center,the obtained electrocatalyst only needed 285 mV to reach 10 mA·cm^(−2)in 0.1 M HClO4.Reaction kinetic has been rapidly accelerated as indicated by the smaller Tafel slope and charge transfer resistance.Theoretical calculations revealed that the d-band center and charge density distribution have been regulated with the introduction of defects in IrO_(2)/Ir,which significantly decreased the free energy barrier of rate determining step.This work provides a valuable reference to design effective and defects-rich electrocatalysts.

The role of strain in oxygen evolution reaction

The oxygen evolution reaction(OER)is a crucial step in metal-air batteries and water splitting technologies,playing a significant role in the efficiency and achievable heights of these two technologies.However,the OER is a four-step,four-electron reaction,and its slow kinetics result in high overpotentials,posing a challenge.To address this issue,numerous strategies involving modified catalysts have been proposed and proven to be highly efficient.In these strategies,the introduction of strain has been widely reported because it is generally believed to effectively regulate the electronic structure of metal sites and alter the adsorption energy of catalyst surfaces with reaction intermediates.However,strain has many other effects that are not well known,making it an important yet unexplored area.Based on this,this review provides a detailed introduction to the various roles of strain in OER.To better explain these roles,the review also presents the definition of strain and elucidates the potential mechanisms of strain in OER based on the d-band center theory and adsorption volcano plot.Additionally,the review showcases various ways of introducing strain in OER through examples reported in the latest literature,aiming to provide a comprehensive perspective for the development of strain engineering.Finally,the review analyzes the appropriate proportion of strain introduction,compares compressive and tensile strain,and examines the impact of strain on stability.And the review offers prospects for future research directions in this emerging field.

Compressively Strained InGaAs/InGaAsP Quantum Well Distributed Feedback Laser at 1.74μm

The compressively strained InGaAs/InGaAsP quantum well distributed feedback laser with ridge-wave- guide is fabricated at 1.74μm. It is grown by low-pressure metal organic chemical vapor deposition（MOCVD）. A strain buffer layer is used to avoid indium segregation. The threshold current of the device uncoated with length of 300μm is 11.5mA. The maximum output power is 14mW at 100mA. A side mode suppression ratio of 35.5dB is obtained.

Effects of vertical electric field and compressive strain on electronic properties of bilayer ZrS2

Using first-principles calculations,including Grimme D2 method for van der Waals interactions,we investigate the tuning electronic properties of bilayer zirconium disulfides（ZrS_2/ subjected to vertical electric field and normal compressive strain.The band gap of ZrS_2 bilayer can be flexibly tuned by vertical external electric field.Due to the Stark effect,at critical electric fields about 1.4 V/？,semiconducting-metallic transition presents.In addition,our results also demonstrated that the compressive strain has an important impact on the electronic properties of ZrS_2 bilayer sheet.The widely tunable band gaps confirm possibilities for its applications in electronics and optoelectronics.

Effect of strain rate and water-to-cement ratio on compressive mechanical behavior of cement mortar

Effects of strain rate and water-to-cement ratio on the dynamic compressive mechanical behavior of cement mortar are investigated by split Hopkinson pressure bar(SHPB) tests. 124 specimens are subjected to dynamic uniaxial compressive loadings.Strain rate sensitivity of the materials is measured in terms of failure modes, stress-strain curves, compressive strength, dynamic increase factor(DIF) and critical strain at peak stress. A significant change in the stress-strain response of the materials with each order of magnitude increase in strain rate is clearly seen from test results. The slope of the stress-strain curve after peak value for low water-to-cement ratio is steeper than that of high water-to-cement ratio mortar. The compressive strength increases with increasing strain rate. With increase in strain rate, the dynamic increase factor(DIF) increases. However, this increase in DIF with increase in strain rate does not appear to be a function of the water-to-cement ratio. The critical compressive strain increases with the strain rate.

Flow behavior and microstructure of ZK60 magnesium alloy compressed at high strain rate

Flow behavior and microstructure of a homogenized ZK60 magnesium alloy were investigated during compression in the temperature range of 250-400 ℃ and the strain rate range of 0.1-50 s^-1. The results showed that dynamic recrystallization （DRX） developed mainly at grain boundaries at lower strain rate （0.1-1 s^-1）, while in the case of higher strain rate （10-50 s^-1）, DRX occurred extensively both at twins and grain boundaries at all temperature range, especially at temperature lower than 350 ℃, which resulted in a more homogeneous microstructure than that under other deformation conditions. The DRX extent determines the hot workability of the workpiece, therefore, hot deformation at the strain rate of 10-50 s^-1 and in the temperature range of 250-350 ℃ was desirable for ZK60 alloy. Twin induced DRX during high strain rate compression included three steps. Firstly, twins with high dislocation subdivided the initial grain, then dislocation arrays subdivided the twins into subgrains, and after that DRX took place with a further increase of strain.

High temperature deformation and recrystallization behavior of magnesium bicrystals with 90°<1010>and 90°<1120>tilt grain boundaries

The deformation mechanisms and dynamic recrystallization(DRX)behavior of specifically grown bicrystals with a symmetric 90°<1010>and 90°<1120>tilt grain boundary,respectively,were investigated under deformation in plane strain compression at 200℃and 400℃.The microstructures were analyzed by panoramic optical microscopy and large-area electron backscatter diffraction(EBSD)orientation mapping.The analysis employed a meticulous approach utilizing hundreds of individual,small EBSD maps with a small step size that were stitched together to provide comprehensive access to orientation and misorientation data on a macroscopic scale.Basal slip primarily governed the early stages of deformation at the two temperatures,and the resulting shear induced lattice rotation around the transverse direction(TD)of the sample.The existence of the grain boundary gave rise to dislocation pile-up in its vicinity,leading to much larger TD-lattice rotations within the boundary region compared to the bulk.With increasing temperature,the deformation was generally more uniform towards the bulk due to enhanced dislocation mobility and more uniform stress distribution.Dynamic recrystallization at 200℃was initiated in{1011}-compression twins at strains of 40%and higher.At 400℃,DRX consumed the entire grain boundary region and gradually replaced the deformed microstructure with progressing deformation.The recrystallized grains displayed characteristic orientations,such that their c-axes were perpendicular to the TD and additionally scattered between 0°and 60°from the loading axis.These recrystallized grains displayed mutual rotations of up to 30°around the c-axes of the initial grains,forming a discernible basal fiber texture component,prominently visible in the{1120}pole figure.It is noteworthy that the deformation and DRX behaviors of the two analyzed bicrystals exhibited marginal variations in response to strain and deformation temperature.

RECRYSTALLIZATION BEHAVIOR AND PRIOR AUSTENITE GRAIN BOUNDARY CORROSION IN THE PLANE STRAIN COMPRESSION CONDITION FOR A LOW CARBON X70 PIPELINE STEEL

Recrystallization behavior of a low carbon X70 pipeline steel was studied in the plane strain compression condition. It was found that the dynamic recovery but no dynamic recrystal- lization occurred in the current experimental condition. A method for examining the prior austenite grain boundary corrosion was supposed.

Moisture effect on compressive behavior of concrete under dynamic loading

The effect of moisture content upon compressive mechanical behavior of concrete under impact loading was studied. The axial rapid compressive loading tests of over 50 specimens with five different saturations were executed. The technique "split Hopkinson pressure bar"(SHPB) was used. The impact velocity was 10 m/s with corresponding strain rate of 50 s-1. The compressive behavior of materials was measured in terms of stress-strain curves, dynamic compressive strength, dynamic increase factor(DIF) and critical strain at a maximum stress. The data obtained from test indicate that both ascending and descending portions of stress-stain curves are affected by moisture content. However, the effect is noted to be more significant in ascending portion of the stress-strain curves. Dynamic compressive strength is higher at lower moisture content and weaker at higher moisture content.Furthermore, under nearly saturated condition, an increase in compressive strength can be found. The effect of moisture content on the average DIF of concrete is not significant. The critical compressive strain of concrete does not change with moisture content.

Deformation behaviour of magnesium bicrystals with symmetrical 90°<1120>tilt grain boundaries analysed by large area EBSD mapping

Grain boundaries play a significant role in the deformation of polycrystals.Their response to deformation is however not completely understood,particularly with respect to how they accommodate lattice rotation of adjoining crystallites by changing their structure and geometry.The current study thus investigates the deformation behaviour of Mg bicrystals with 90°<1120>symmetric tilt boundary strained in plane-strain compression up to different final strains.Due to the initial soft orientation of the two crystals,activation of basal slip in each crystal gave rise to lattice rotation around the transverse direction towards the compression direction of the channel-die.Hundreds of single EBSD maps with a small step size were obtained from the GB region and stitched together to produce large panoramic maps of a macroscopic scale.Although very time-consuming,this technique has proven useful in clarifying the origin of the non-uniform deformation zones in the vicinity of the grain boundary and explains the mechanisms,by which the grain boundary was able to cope with the imposed strain before fracture.Interestingly,several variants of extension twins were observed as an additional deformation mechanism despite having negative Schmid factors.Systematic investigation of their resulting combined shear components with respect to the sample coordinate system revealed an alignment along the longitudinal direction of the channel-die,therefore justifying their nucleation.

Local buckling failure analysis of high-strength pipelines

Pipelines in geological disaster regions typically suffer the risk of local buckling failure because of slender structure and complex load. This paper is meant to reveal the local buckling behavior of buried pipelines with a large diameter and high strength, which are under different conditions, including pure bending and bending combined with internal pressure. Finite element analysis was built according to previous data to study local buckling behavior of pressurized and unpressurized pipes under bending conditions and their differences in local buckling failure modes. In parametric analysis, a series of parameters,including pipe geometrical dimension, pipe material properties and internal pressure, were selected to study their influences on the critical bending moment, critical compressive stress and critical compressive strain of pipes.Especially the hardening exponent of pipe material was introduced to the parameter analysis by using the Ramberg–Osgood constitutive model. Results showed that geometrical dimensions, material and internal pressure can exert similar effects on the critical bending moment and critical compressive stress, which have different, even reverse effects on the critical compressive strain. Based on these analyses, more accurate design models of critical bending moment and critical compressive stress have been proposed for high-strength pipelines under bendingconditions, which provide theoretical methods for highstrength pipeline engineering.

Research on China's high-grade highway design index of asphalt pavement with granular base

Based on the 2006 Chinese asphalt pavement deflection value design index, we used KENLAYER Pavement Analysis and Design software and lstOpt statistical analysis software to can-y on the nonlinear regression, this paper establish high-grade highway design equations for the compressive slrain of soil sub-base top （CSSBT） and the radial compressive stress of semi-rigid base top （RCSRBT）. The correlation coefficients inspection standard to get precise proof, which means that our granular base design equations have high credibility and can be used in the Chinese design index of asphalt pavement with granular base （APGB）.

Compressively-strained GaSb nanowires with core-shell heterostructures

GaSb-based nanowires in a gate-all-around geometry are good candidates for binary p-type transistors,however they require the introduction of compressive strain to enhance the transport properties.Here,we for the first time demonstrate epitaxial GaSb-GaASxSb1-x core-shell nanowires with a compressively strained core.Both axial and hydrostatic strain in GaSb core have been measured by X-ray diffraction(XRD)and Raman scattering,respectively.The optimal sample,almost without plastic relaxation,has an axial strain of-0.88%and a hydrostatic strain of-1.46%,leading to a noticeable effect where the light hole band is calculated to be 33.4 meV above the heavy hole band at the T-point.This valence band feature offers more light holes to contribute the transport process,and thus may provide enhanced hole mobility by reducing both the interband scattering and the hole effective mass.Our results show that lattice-mismatched epitaxial core-shell heterostructures of high quality can also be realized in the promising yet demanding GaSb-based system.

Grain boundary effect on structural, optical, and electrical properties of sol-gel synthesized Fe-doped SnO_(2) nanoparticles

Tin oxide(SnO_(2)) and iron-doped tin oxide(Sn_(1-x)Fe_(x)O_(2),x=0.05 wt%,0.10 wt%) nanoparticles are synthesized by the simple sol-gel method.The structural characterization using x-ray diffraction(XRD) confirms tetragonal rutile phases of the nanoparticles.The variations in lattice parameters and relative intensity with Fe-doping concentration validate the incorporation of iron into the lattice.The compressive strain present in the lattice estimated by using peak profile analysis through using Williamson-Hall plot also exhibits the influence of grain boundary formation in the lattice.The radiative recombination and quenching observed in optical characterization by using photoluminescence spectrum(PL) and the shift in the band gap estimated from UV-visible diffused reflectance spectrum corroborate the grain boundary influence.Raman spectrum and the morphological analysis by using a field emission scanning electron microscope(FESEM) also indicate the formation of grain boundaries.The compositional analysis by using energy dispersive x-ray spectrum(EDAX) confirms Fe in the SnO_(2) lattice.The conductivity studies exhibit that the impendence increases with doping concentration increasing and the loss factor decreases at high frequencies with doping concentration increasing,which makes the Sn_(1-x)Fe_(x)O_(2) a potential candidate for device applications.

Numerical study on deformation and failure of reinforced sand

In order to investigate the deformation and failure of reinforced sand, and the reinforcing mechanism of flexible and rigid reinforcement, a set of plane strain compression tests of dense Toyoura reinforced sand with planar reinforcement of a wide range of stiffness were analysed by a nonlinear finite element method. The analysis was incorporated into an energy-based elasto-plastic constitutive model for sand to develop a stress path-independent work-hardening parameter based on the modified plastic strain energy concept. Numerical results indicate that the global stress-strain relations of sand specimens are reinforced by using relatively flexible and rigid reinforcement, and an unreinforced sand specimen can be reasonably simulated by the current finite element method. It is also found that the reinforcing mechanism and progressive failure with a development of shear bands in reinforced sand can be reasonably examined by the finite element method.

Sheet metal hardening curve determined by laminated sample and its adaptability to sheet forming processes

The hardening curve for sheet metal can be determined from the load-displacement curve of tensile specimen with rectangular cross-section. Therefore,uniaxial compression test on cylinder specimen made from laminated sample is put forward. Considering the influence of anisotropy on hardening properties and the stress state in popular forming process,plane strain compression test on cubic specimen made from laminated sample was advanced. Results show that the deformation range of hardening curves obtained from the presented methods is wide,which meets the need for the application in sheet metal forming processes. In view of the characteristics of methods presented in the paper and the stress strain state of various forming processes,the adaptability of the two methods presented in this paper is given.