A green pregelatinized glutinous rice flour biological admixture was developed in this paper.The cement hydration process,hydration products,pore structure,and strength of mortar with different quantities of glutinous...A green pregelatinized glutinous rice flour biological admixture was developed in this paper.The cement hydration process,hydration products,pore structure,and strength of mortar with different quantities of glutinous rice flour(GRF),and the macroscopic changes in concrete cracking resistance testing were investigated.Simultaneously,a fast cracking resistance evaluation method based on graphic recognition was proposed.The results indicated that pregelatinized glutinous rice flour(T-GRF)delayed the dissolution rate of anhydrous cement during the induction period,shifting the main exothermic peak of hydration backward.The compressive strength developed slowly in 7-28 d age and returned to normal in 28-56 d.The compressive strength of T-GRF-0.6% modified mortar at 56 d age is less than 10% different from that of control group.The 3.0%T-GRF decreased the total porosity by 3%,and the average pore size decreased from 31.2 to 21.3 nm measured by MIP,indicating that T-GRF could inhibit harmful pores and densify concrete.The crack resistance coefficient of T-GRF modified concrete was obtained by image recognition method,and the GRF could decrease the length,width,and damaged area of cracks in the early age of concrete.展开更多
Soil desiccation cracking is a common phenomenon on the earth surface.Numerical modeling is an effective approach to study the desiccation cracking mechanism of soil.This work develops a novel 3D moisture diffusion di...Soil desiccation cracking is a common phenomenon on the earth surface.Numerical modeling is an effective approach to study the desiccation cracking mechanism of soil.This work develops a novel 3D moisture diffusion discrete model that is capable of dynamically assessing the effect of cracking on moisture diffusion and allowing moisture to be discontinuous on both sides of the cracks.Then,the parametric analysis of the moisture exchange coefficient in the 3D moisture diffusion discrete model is carried out for moisture diffusion in continuous media,and the selection criterion of the moisture exchange coefficient for the unbroken cohesive element is given.Subsequently,an example of moisture migration in a medium with one crack is provided to illustrate the crack hindering effect on moisture migration.Finally,combining the 3D moisture diffusion discrete model with the finite-discrete element method(FDEM),the moisture diffusion-fracture coupling model is built to study the desiccation cracking in a strip soil and the crack pattern of a rectangular soil.The evolution of crack area and volume with moisture content is quantitatively analyzed.The modeling number and average width of cracks in the strip soil show a good consistency with the experimental results,and the crack pattern of the rectangular soil matches well with the existing numerical results,validating the coupled moisture diffusion-fracture model.Additionally,the parametric study of soil desiccation cracking is performed.The developed model offers a powerful tool for exploring soil desiccation cracking.展开更多
Additive manufacturing (AM) of high-strength metallic alloys frequently encounters detrimental distortion and cracking, attributed to the accumulation of thermal stresses. These issues significantly impede the practic...Additive manufacturing (AM) of high-strength metallic alloys frequently encounters detrimental distortion and cracking, attributed to the accumulation of thermal stresses. These issues significantly impede the practical application of as-printed components. This study examines the Mg-15Gd-1Zn-0.4Zr (GZ151K, wt.%) alloy, a prototypical high-strength casting Mg-RE alloy, fabricated through laser powder bed fusion (LPBF). Despite achieving ultra-high strength, the GZ151K alloy concurrently exhibits a pronounced cold-cracking susceptibility. The as-printed GZ151K alloy consists of almost fully fine equiaxed grains with an average grain size of merely 2.87 µm. Subsequent direct aging (T5) heat treatment induces the formation of dense prismatic β' precipitates. Consequently, the LPBF-T5 GZ151K alloy manifests an ultra-high yield strength of 405 MPa, surpassing all previously reported yield strengths for Mg alloys fabricated via LPBF and even exceeding that of its extrusion-T5 counterpart. Interestingly, as-printed GZ151K samples with a build height of 2 mm exhibit no cracking, whereas samples with build heights ranging from 4 to 18 mm demonstrate severe cold cracking. Thermal stress simulation also suggests that the cold cracking susceptibility increases significantly with increasing build height. The combination of high thermal stress and low ductility in the as-printed GZ151K alloy culminates in a high cold cracking susceptibility. This study offers novel insights into the intricate issue of cold cracking in the LPBF process of high-strength Mg alloys, highlighting the critical balance between achieving high strength and mitigating cold cracking susceptibility.展开更多
High cracking susceptibility of Al-Li alloys with Ti/Ce B6addition is thoroughly suppressed in laser powder bed fusion(LPBF)processing of Ti/Ce co-modified 2195 alloys at relatively high scan speeds,while the cracking...High cracking susceptibility of Al-Li alloys with Ti/Ce B6addition is thoroughly suppressed in laser powder bed fusion(LPBF)processing of Ti/Ce co-modified 2195 alloys at relatively high scan speeds,while the cracking suppression mechanism and phase formation in these composites are not clarified.In this work,microstructure evolution and mechanical performance of the LPBF-fabricated Ti/Ce co-modified 2195 are investigated to reveal their cracking suppression and strengthening mechanisms.The results show that apparent grain refinement of the composites is ascribed to high supercooling from rapid formation of constitutional supercooling zone in front of solid–liquid interfaces by high-Q-value Ti solute,and heterogeneous nucleation of in situ formed Al3Ti and Al11Ce3precipitates.Their synergistic interactions promote formation of fine equiaxed grains and thus inhibit crack initiation.The composites exhibit high microhardness of 100±5HV0.2,nano-hardness of 1.6±0.1 GPa and elastic modulus of 97±3 GPa,where the elastic modulus increases by 27%and 31%compared to those of LPBF-processed and conventionally manufactured 2195 alloys,respectively.A tensile strength of 336 MPa and an elongation of 3%are obtained from in-situ synchrotron X-ray diffraction measurement.The improved properties are derived from grain refinement and Orowan strengthening.Based on the optimal processing parameter and composition,a bracket component filled with lattice structures is designed and manufactured with good manufacturing quality and processing accuracy.展开更多
Mg-Li alloys hold significant potential for applications in aerospace,automotive manufacturing,military weaponry,and biomedical implants,due to their excellent recyclability,high specific strength,biocompatibility,and...Mg-Li alloys hold significant potential for applications in aerospace,automotive manufacturing,military weaponry,and biomedical implants,due to their excellent recyclability,high specific strength,biocompatibility,and superior electromagnetic shielding properties.However,their poor corrosion resistance and high susceptibility to environmentally assisted cracking(EAC)significantly limit broader application.In recent years,growing attention has been directed toward understanding the corrosion and EAC behavior of Mg-Li alloys,as localized corrosion areas and hydrogen generated during the corrosion process can serve as crack initiation points and promote crack propagation.A comprehensive understanding of these mechanisms is essential for enhancing the reliability and performance of Mg-Li alloys in practical environments.This paper presents a detailed review of corrosion and EAC in Mg-Li alloys,focusing on corrosion behavior,crack initiation and propagation mechanisms,and the key factors influencing these processes.It summarizes recent advances in alloying,heat treatment,mechanical processing,microstructural control,environmental influences,mechanical loading,and surface treatments.In addition,the paper explores future research directions,highlights emerging trends,and proposes strategies to improve the durability and service performance of Mg-Li alloys.展开更多
Solidification cracking(SC)of 2024 high-strength aluminium alloy during fusion welding or additive manufacturing has been a long-term issue.In this work,crack-free weld could be obtained using a Zr-core-Alshell wire(Z...Solidification cracking(SC)of 2024 high-strength aluminium alloy during fusion welding or additive manufacturing has been a long-term issue.In this work,crack-free weld could be obtained using a Zr-core-Alshell wire(ZCASW filler material,a novel filler)coupled with an oscillating laser-arc hybrid welding process,and we investigated the solidification cracking susceptibility(SCS)and cracking behavior of AA2024 weld fabricated with different filler materials.The cracking inhibition mechanism of the weld fabricated with ZCASW filler material was elucidated by combined experiments and phase-field simulation.The results show that the effectiveness of filler materials in reducing the SC gradually improves in the order of ER2319 filler material<ER4043 filler material<ZCASW filler material.The main cracking(when using the ER2319 filler material)branches and the micro cracking branches interact with each other to produce cracking coalescence,which aggravates the cracking propagation.The formation of the Al_(3) Zr phase(when using the ZCASW filler material)promotes heterogeneous nucleation of α-Al,thereby resulting in finer and equiaxed non-dendrite structures,which shortens the liquid phase channels and decreases cracking susceptibility index|d T/d(f_(s))^(1/2)|(T is temperature and f_(s) is solidification fraction)at final solidification.A higher proportion(7.65%area fraction)of inter-dendrite phase with spherical distribution state,a shorter(8.6 mm liquid channel length)inter-dendrite phase coupled with round non-dendrite structure(6μm dendrite size)effectively inhibit the SC.The present study can be a useful database for welding and additive manufacturing of AA2024.展开更多
Coralline soils,specialized materials found extensively in the South China Sea,are playing an increasingly vital role in engineering projects.However,like most terrigenous soils,fine-grained coral soil is prone to shr...Coralline soils,specialized materials found extensively in the South China Sea,are playing an increasingly vital role in engineering projects.However,like most terrigenous soils,fine-grained coral soil is prone to shrinkage and cracking,which can significantly affect its engineering properties and ultimately jeopardize engineering safety.This paper presents a desiccation cracking test of fine-grained coral soil,with a particular focus on the thickness effect.The study involved measuring the water content and recording the evolution of desiccation cracking.Advanced image processing technology is employed to analyze the variations in crack parameters,clod parameters,fractal dimensions,frequency distributions,and desiccation cracking propagation velocities of fine-grained coral soil.Furthermore,the dynamic evolution of desiccation cracking under the influence of layer thickness is analyzed.A comprehensive crack evolution model is proposed,encompassing both top-down and bottom-up crack propagation,as well as internal tensile cracking.This work introduces novel metrics for the propagation velocity of the total crack area,the characteristic propagation velocities of desiccation cracks,and the acceleration of crack propagation.Through data fitting,theoretical formulas for soil water evaporation,propagation velocities of desiccation cracks,and crack propagation acceleration are derived,laying a foundation for future soil cracking theories.展开更多
Soil desiccation cracking is ubiquitous in nature and has significantpotential impacts on the engineering geological properties of soils.Previous studies have extensively examined various factors affecting soil cracki...Soil desiccation cracking is ubiquitous in nature and has significantpotential impacts on the engineering geological properties of soils.Previous studies have extensively examined various factors affecting soil cracking behavior through a numerous small-sample experiments.However,experimental studies alone cannot accurately describe soil cracking behavior.In this study,we firstly propose a modeling framework for predicting the surface crack ratio of soil desiccation cracking based on machine learning and interpretable analysis.The framework utilizes 1040 sets of soil cracking experimental data and employs random forest(RF),extreme gradient boosting(XGBoost),and artificialneural network(ANN)models to predict the surface crack ratio of soil desiccation cracking.To clarify the influenceof input features on soil cracking behavior,feature importance and Shapley additive explanations(SHAP)are applied for interpretability analysis.The results reveal that ensemble methods(RF and XGBoost)provide better predictive performance than the deep learning model(ANN).The feature importance analysis shows that soil desiccation cracking is primarily influencedby initial water content,plasticity index,finalwater content,liquid limit,sand content,clay content and thickness.Moreover,SHAP-based interpretability analysis further explores how soil cracking responds to various input variables.This study provides new insight into the evolution of soil cracking behavior,enhancing the understanding of its physical mechanisms and facilitating the assessment of potential regional development of soil desiccation cracking.展开更多
Peridynamics(PD)is an effective method for simulating the spontaneous initiation and propagation of tensile cracks in materials.However,it faces great challenges in simulating compression-shear cracking of geomaterial...Peridynamics(PD)is an effective method for simulating the spontaneous initiation and propagation of tensile cracks in materials.However,it faces great challenges in simulating compression-shear cracking of geomaterials due to the lack of efficient contact-friction models.This paper introduces an original contact-friction model that leverages twin mesh and potential function principles within PD to model rock cracking under tensile and compressive stresses.The contact detection algorithm,based on space segmentation axis-aligned bounding box(AABB)tree data structure,is used to address the significant challenge of highly efficient contact detection in compression and shear problems.In this method,the twin mesh and potential function are utilized to quantify contact detection and contact degree,as well as friction behavior.This is in contrast to the distance and circular contact area model,which lacks physical significance in the classical PD method.As demonstrated by the tests on specimens containing cracks,the proposed model can capture 8 types of secondary fractures,reduce the contact detection error by about 29%e56%,and increase the contact retrieval efficiency by over 1600 times compared to the classic PD models.This significantly enhances the capability of PD to simulate the initiation,expansion,and coalescence of intricate compression-shear cracks.展开更多
Cracking affected by wetting-drying cycles is a major cause of shallow failure of soft rock slopes.Knowledge of rock tensile properties and cracking behaviors helps better assess the stability of soft rock slopes.This...Cracking affected by wetting-drying cycles is a major cause of shallow failure of soft rock slopes.Knowledge of rock tensile properties and cracking behaviors helps better assess the stability of soft rock slopes.This study aims to examine the cracking behaviors and tensile strength of silty mudstone under wetting-drying cycles.The wetting-drying cycle and Brazilian splitting tests were performed on silty mudstone considering various cycle number and amplitude.The cracking behaviors of wetting-drying cycles were analyzed by digital image correlation,three-dimensional(3D)scanning technology,and scanning electron microscopy.The results reveal a spiral-like pattern of crack ratio escalation in silty mudstone,with a higher crack ratio observed during drying than wetting.Tensile strength and fracture energy correlate negatively with cycle number or amplitude,with cycle number exerting a more pronounced effect.The variance of the maximum principal strain reflects stages of initial deformation,linear deformation,strain localization,and stable deformation.The formation of strain localization zones reveals the physical process of crack propagation.Crack tip opening displacement progresses through stages of slow growth,exponential growth,and linear growth,delineating the process from crack initiation to stable extension.Failure modes of silty mudstone primarily involve tensile and tensile-shear failure,influenced by the geometric parameters of cracks induced by wetting-drying cycles.Fracture surface roughness and fractal dimension increase with cycle number due to mineral dissolution,physical erosion,and nondirectional crack propagation.Hydration-swelling and dehydration-shrinkage of clay minerals,along with absorption-drying cracking,initiate and merge cracks,leading to degradation of the rock mechanical properties.The findings could provide insights for mitigating shallow cracking of soft rock slopes under wetting-drying cycles.展开更多
There remains debate on whether Mn is beneficial or detrimental to hydrogen embrittlement in stainless steel.In this work,a series of stainless steels were designed to study the change of hydrogen embrittlement sensit...There remains debate on whether Mn is beneficial or detrimental to hydrogen embrittlement in stainless steel.In this work,a series of stainless steels were designed to study the change of hydrogen embrittlement sensitivity,crack propagation,and hydrogen trapping behaviors upon Mn addition.The results suggest that adding 4 wt.% Mn increased hydrogen embrittlement susceptibility,whereas adding 8 wt.% Mn decreased hydrogen embrittlement sensitivity.Forming banded α’-martensite through austenitic grain is the main reason for the increased hydrogen embrittlement sensitivity when adding 4 wt.%Mn,by adsorbing hydrogen,promoting crack initiation,and accelerating crack propagation.展开更多
A comparative study of products of thermal and thermocatalytic cracking of polypropylene(PP) in the presence of potassium polytitanate(PPT) synthesized by treatment of TiO_(2)(rutile) powder with molten mixture of KOH...A comparative study of products of thermal and thermocatalytic cracking of polypropylene(PP) in the presence of potassium polytitanate(PPT) synthesized by treatment of TiO_(2)(rutile) powder with molten mixture of KOH and KNO_(3) taken in a weight ratio of 30∶30∶40 has been carried out.It was shown that the studied type of PPT powder exhibits catalytic properties in the reaction of thermal decomposition of PP,compared to the effect of commercial zeolite catalyst CBV-780 traditionally used for this purpose.Based on the analysis performed,the differences in the mechanism of catalytic action of PPT and the zeolite were considered.The reasons for the observed differences in the composition of PP cracking products and in the rate of coke formation on the surface of studied catalysts were analyzed.Considering the obtained results,it has been proposed that the CBV-780 catalyst promoted more intensive production of the gaseous hydrocarbons compared to PPT,due to higher specific surface area(internal surface) accessible for relatively light and small-sized hydrocarbon products of cracking.However,intensive coke formation on the outer surface of the microporous zeolite contributes to the blocking of transport channels and the rapid loss of catalytic action.At the same time,PPT,which initially has a smaller specific surface area,retains its catalytic activity significantly longer due to slit-shaped flat pores and higher transport accessibility of the inner surface.展开更多
By using fatigue crack propagation testing and microstructural characterization,the crack fracture and propagation mechanisms of K4169 superalloy under various loads were investigated.The results demonstrate that the ...By using fatigue crack propagation testing and microstructural characterization,the crack fracture and propagation mechanisms of K4169 superalloy under various loads were investigated.The results demonstrate that the grain sizes of K4169 superalloy significantly increase,and the precipitation of the needle-likeδphase and the Laves phase is observed.Voids and microcracks form at location of Laves phase enrichment,creating conditions for crack propagation.By the a−N(a is the crack length,and N is the number of cycles)relationship curve,the change in the fatigue crack growth rate with the increasing number of cycles progresses through three separate stages.The fracture process of K4169 superalloy under low-stress cyclic loading(3 kN)exhibits the ductile fracture.Subsequently,the fracture process starts to change from the ductile fracture to the brittle fracture as the stress increases to 4.5 kN.In the microstructures of fractures in both stress states,intergranular propagation is the mechanism responsible for crack propagation.Moreover,the Laves phase exists near the fracture crack,which is in line with the post-service structural phenomenon.展开更多
The edge crack behavior of copper foil in asymmetrical micro-rolling was studied.The effects of the speed ratio between rolls,grain size and stress state in the deformation zone on edge cracks of the rolled piece in a...The edge crack behavior of copper foil in asymmetrical micro-rolling was studied.The effects of the speed ratio between rolls,grain size and stress state in the deformation zone on edge cracks of the rolled piece in asymmetrical rolling were analyzed.Low plasticity,uneven deformation and longitudinal secondary tensile stress generated in the edge area of the rolled piece during the rolling process are the main causes of edge cracks.The larger the grain size of the rolled piece,the smaller the number of edge cracks and the deeper the expansion depth,and the larger the spacing between cracks under the same rolling reduction.Asymmetrical rolling can effectively increase the rolling reduction at when the copper foil fist shows edge cracks compared to symmetrical rolling.This enhancement is attributed to the shearing stress induced by asymmetrical rolling,which reduces the rolling force and longitudinal secondary tensile stress,and increases the residual compressive stress on the surface of the rolled piece.The edge crack defects of copper foil can be effectively reduced by increasing the speed ratio between the rolls in asymmetrical rolling.展开更多
This study leverages machine learning to perform high-throughput computational screening of n-hexane cracking initiators.Artificial neural networks are applied to predict the chemical performance of initiators,using s...This study leverages machine learning to perform high-throughput computational screening of n-hexane cracking initiators.Artificial neural networks are applied to predict the chemical performance of initiators,using simulated pyrolysis data as the training dataset.Various feature extraction methods are utilized,and five neural network architectures are developed to predict the co-cracking product distribution based on molecular structures.High-throughput screening of 12946 molecules outside the training dataset identifies the top 10 initiators for each target product—ethylene,propylene,and butadiene.The relative error between predicted and simulated values is less than 7%.Additionally,reaction pathway analysis elucidates the mechanisms by which initiators influence the distribution of cracking products.The proposed framework provides a practical and efficient approach for the rapid identification and evaluation of high-performance cracking initiators.展开更多
The 7075 aluminum alloy was subjected to power-modulated laser welding using a full-domain power modulation(FDPM)laser oscillating welding system.Three different power modes were utilized:constant power(CP),gradient p...The 7075 aluminum alloy was subjected to power-modulated laser welding using a full-domain power modulation(FDPM)laser oscillating welding system.Three different power modes were utilized:constant power(CP),gradient power(GP),and alternating power(AP)modes.The impact of different power modes on joint crack sensitivity,microstructure,and residual stress was assessed.The results demonstrate that joint welded with the AP mode exhibits the lowest sensitivity to solidification cracking(with mean crack sensitivity of 18.3%),and the smallest average grain size in the fusion zone of the weld seam(80μm).Additionally,it shows the highest microhardness(HV 113)and the narrowest softening region(3.5 cm).Furthermore,the joint displays the lowest residual stress and cooling rate,which is the reason for its minimal crack sensitivity.展开更多
This study investigates the stress corrosion cracking(SCC)behavior of a Mg-8Gd-3Y-0.5Zr alloy in a 3.5 wt.%NaCl solution using slow strain rate tensile(SSRT)testing.The results reveal that SCC suscepti-bility increase...This study investigates the stress corrosion cracking(SCC)behavior of a Mg-8Gd-3Y-0.5Zr alloy in a 3.5 wt.%NaCl solution using slow strain rate tensile(SSRT)testing.The results reveal that SCC suscepti-bility increases as the strain rate decreases,with hydrogen embrittlement(HE)becoming more dominant at lower strain rates,leading to brittle fracture.Anodic dissolution(AD)plays a more significant role at higher strain rates,resulting in mixed fracture modes.Additionally,the mechanical properties and SCC resistance are strongly influenced by the sample orientation.TD-oriented samples show higher SCC susceptibility than RD-oriented ones due to the alignment of Gd-and Y-rich precipitates and grain boundaries,which act as initiation sites for SCC.These precipitates form micro-galvanic couples with the Mg matrix,accelerating localized corrosion and HE.The findings provide insights into the SCC mechanisms of VW83 alloy and highlight the importance of optimizing microstructure and processing conditions to improve its corrosion resistance.展开更多
In recent years,(0001)twist grain boundaries(BTGBs)located in primary α grain clusters were identified as fatigue crack nucleation sites in different Ti alloys.In the present study,crack initiation was investigated i...In recent years,(0001)twist grain boundaries(BTGBs)located in primary α grain clusters were identified as fatigue crack nucleation sites in different Ti alloys.In the present study,crack initiation was investigated in a bimodal Ti-5Al-4 V alloy subjected to low-cycle fatigue and dwell-fatigue loadings at room temperature.The low fraction of primary α grains was not associated with a lack of sensitivity to BTGB cracking.Transmission electron microscopy and electron back-scattered diffraction were used to characterize BTGBs in the initial microstructure.The fatigue mechanisms were then analyzed with a focus on dislocation activity.α_(p) grains adjacent to cracked BTGBs contained a high dislocation density.It was primarily composed of planar slip bands of dislocations.In addition,<c+a>dislocations were noticed in the vicinity of cracked BTGBs.They supposedly pertain to crack tip plasticity during growth,and no evidence of a role of an incoming slip event in crack nucleation was obtained.Also,basal slip bands extending across adjacent grains were found to emerge from BTGBs.This feature provides an easier path for crack extension when growth along the grain boundary becomes difficult owing to a deviation from the basal plane.Atom probe tomography analyses evidenced V and Fe segregation at a grain boundary with a significant deviation from the BTGB configuration.This suggests a possible contribution of local solute segregation to the high cracking resistance of general α_(p)/α_(p) grain boundaries.This work provides new insights into the mechanisms involved in cracking of BTGB in Ti alloys subjected to cyclic loadings.展开更多
A mathematical model coupling flow,solidification,strain-stress,and interface failure was developed.Following identification of crack source type through thermal tensile experiment and validation by strain-stress comp...A mathematical model coupling flow,solidification,strain-stress,and interface failure was developed.Following identification of crack source type through thermal tensile experiment and validation by strain-stress comparison,the model was used to investigate slab cracking tendency near precipitated phases,considering various locations,sizes and shapes of them.The results show that the jet from submerged entry nozzle creates a“double roll”flow pattern during continuous casting,resulting in more uniform temperature distributions at slab corner and wide surface center compared with narrow surface center.Consequently,precipitated phases,particularly those located on the narrow surface,readily induce stress concentration and thus increase cracking tendency.A smaller precipitated phase size can reduce the stress concentration zone,while a more spherical shape can distribute surrounding stress along its surface and lower the internal stress within it,thereby decreasing the risk of slab cracking during continuous casting.The optimal precipitated phase exhibits a spherical or ellipsoidal shape with a major axis of less than 5µm,minimizing its potential to initiate cracks.展开更多
In subtropical regions,soil desiccation cracking often exerts a significant impact on the interactions between soil water and the atmosphere,making it a subject of great interest in the fields of geotechnical and geoe...In subtropical regions,soil desiccation cracking often exerts a significant impact on the interactions between soil water and the atmosphere,making it a subject of great interest in the fields of geotechnical and geoenvironmental engineering.Despite the growing utilization of biochar as a sustainable soil amendment,there remains a lack of in-depth understanding of biocharewateresoil interactions,as well as its impact on soil desiccation cracking behavior.To address this gap,this study investigated the influence and mechanism of woody biochar dosages and particle sizes on the cracking behavior of three typical clayey soils in subtropical regions in China,namely Pukou expansive soil(PKE),Xiashu soil(XS),and Zhongshan lateritic soil(ZSL).The quantitative analysis of crack images revealed that the use of biochar was not consistently effective in preventing soil cracking.The application of biochar reduced the crack ratio in PKE and XS by up to 24.03%and 53.89%,respectively.In contrast,ZSL exhibited a 74.57%increase in crack ratio with the addition of 10%biochar.This influence can be further enhanced by increasing the dosage and reducing the particle size of biochar.The microstructural analysis demonstrated that biochar exerts an inhibitory effect on PKE and XS primarily through direct replacement,direct barrier,and indirect physical mechanisms.Moreover,an indirect chemical effect between biochar and clay particles was proposed to explain the exacerbated cracking observed in biochar-amended ZSL.To effectively utilize biochar for soil cracking mitigation in subtropical regions,it is essential to evaluate the initial mineral composition and cation type of the soil.展开更多
基金Funded by Hainan Provincial Natural Science Foundation(No.522QN279)State Key Laboratory of High Performance Civil Engineering Materials(No.2023CEM004)。
文摘A green pregelatinized glutinous rice flour biological admixture was developed in this paper.The cement hydration process,hydration products,pore structure,and strength of mortar with different quantities of glutinous rice flour(GRF),and the macroscopic changes in concrete cracking resistance testing were investigated.Simultaneously,a fast cracking resistance evaluation method based on graphic recognition was proposed.The results indicated that pregelatinized glutinous rice flour(T-GRF)delayed the dissolution rate of anhydrous cement during the induction period,shifting the main exothermic peak of hydration backward.The compressive strength developed slowly in 7-28 d age and returned to normal in 28-56 d.The compressive strength of T-GRF-0.6% modified mortar at 56 d age is less than 10% different from that of control group.The 3.0%T-GRF decreased the total porosity by 3%,and the average pore size decreased from 31.2 to 21.3 nm measured by MIP,indicating that T-GRF could inhibit harmful pores and densify concrete.The crack resistance coefficient of T-GRF modified concrete was obtained by image recognition method,and the GRF could decrease the length,width,and damaged area of cracks in the early age of concrete.
基金supported by the State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering(Grant No.SKLGDUEK2206)National Natural Science Foundation of China(Grant No.11872340).
文摘Soil desiccation cracking is a common phenomenon on the earth surface.Numerical modeling is an effective approach to study the desiccation cracking mechanism of soil.This work develops a novel 3D moisture diffusion discrete model that is capable of dynamically assessing the effect of cracking on moisture diffusion and allowing moisture to be discontinuous on both sides of the cracks.Then,the parametric analysis of the moisture exchange coefficient in the 3D moisture diffusion discrete model is carried out for moisture diffusion in continuous media,and the selection criterion of the moisture exchange coefficient for the unbroken cohesive element is given.Subsequently,an example of moisture migration in a medium with one crack is provided to illustrate the crack hindering effect on moisture migration.Finally,combining the 3D moisture diffusion discrete model with the finite-discrete element method(FDEM),the moisture diffusion-fracture coupling model is built to study the desiccation cracking in a strip soil and the crack pattern of a rectangular soil.The evolution of crack area and volume with moisture content is quantitatively analyzed.The modeling number and average width of cracks in the strip soil show a good consistency with the experimental results,and the crack pattern of the rectangular soil matches well with the existing numerical results,validating the coupled moisture diffusion-fracture model.Additionally,the parametric study of soil desiccation cracking is performed.The developed model offers a powerful tool for exploring soil desiccation cracking.
基金supported by the National Key Research and Development Program of China(No.2021YFB3701000)the National Natural Science Foundation of China(Nos.51971130,52201129,U21A2047,51821001,U2037601)+2 种基金support by the China Postdoctoral Science Foun-dation(2023M742219)the Postdoctoral Fellowship Program of CPSF under Grant Number GZB20240419support by the Ministry of Education,Singapore,under its Academic Research Fund Tier 2(MOE-T2EP50221-0013).
文摘Additive manufacturing (AM) of high-strength metallic alloys frequently encounters detrimental distortion and cracking, attributed to the accumulation of thermal stresses. These issues significantly impede the practical application of as-printed components. This study examines the Mg-15Gd-1Zn-0.4Zr (GZ151K, wt.%) alloy, a prototypical high-strength casting Mg-RE alloy, fabricated through laser powder bed fusion (LPBF). Despite achieving ultra-high strength, the GZ151K alloy concurrently exhibits a pronounced cold-cracking susceptibility. The as-printed GZ151K alloy consists of almost fully fine equiaxed grains with an average grain size of merely 2.87 µm. Subsequent direct aging (T5) heat treatment induces the formation of dense prismatic β' precipitates. Consequently, the LPBF-T5 GZ151K alloy manifests an ultra-high yield strength of 405 MPa, surpassing all previously reported yield strengths for Mg alloys fabricated via LPBF and even exceeding that of its extrusion-T5 counterpart. Interestingly, as-printed GZ151K samples with a build height of 2 mm exhibit no cracking, whereas samples with build heights ranging from 4 to 18 mm demonstrate severe cold cracking. Thermal stress simulation also suggests that the cold cracking susceptibility increases significantly with increasing build height. The combination of high thermal stress and low ductility in the as-printed GZ151K alloy culminates in a high cold cracking susceptibility. This study offers novel insights into the intricate issue of cold cracking in the LPBF process of high-strength Mg alloys, highlighting the critical balance between achieving high strength and mitigating cold cracking susceptibility.
基金supported by the National Natural Science Foundation of China(Nos.52205382,52225503)National Key Research and Development Program(No.2023YFB4603300)+3 种基金Key Research and Development Program of Jiangsu Province(Nos.BE2022069,BZ2024019)National Natural Science Foundation of China for Creative Research Groups(No.51921003)International Joint Laboratory of Sustainable Manufacturing,Ministry of Education and the Fundamental Research Funds for the Central Universities(NG2024014)Postgraduate Research&Practice Innovation Program of NUAA(xcxjh20230616)。
文摘High cracking susceptibility of Al-Li alloys with Ti/Ce B6addition is thoroughly suppressed in laser powder bed fusion(LPBF)processing of Ti/Ce co-modified 2195 alloys at relatively high scan speeds,while the cracking suppression mechanism and phase formation in these composites are not clarified.In this work,microstructure evolution and mechanical performance of the LPBF-fabricated Ti/Ce co-modified 2195 are investigated to reveal their cracking suppression and strengthening mechanisms.The results show that apparent grain refinement of the composites is ascribed to high supercooling from rapid formation of constitutional supercooling zone in front of solid–liquid interfaces by high-Q-value Ti solute,and heterogeneous nucleation of in situ formed Al3Ti and Al11Ce3precipitates.Their synergistic interactions promote formation of fine equiaxed grains and thus inhibit crack initiation.The composites exhibit high microhardness of 100±5HV0.2,nano-hardness of 1.6±0.1 GPa and elastic modulus of 97±3 GPa,where the elastic modulus increases by 27%and 31%compared to those of LPBF-processed and conventionally manufactured 2195 alloys,respectively.A tensile strength of 336 MPa and an elongation of 3%are obtained from in-situ synchrotron X-ray diffraction measurement.The improved properties are derived from grain refinement and Orowan strengthening.Based on the optimal processing parameter and composition,a bracket component filled with lattice structures is designed and manufactured with good manufacturing quality and processing accuracy.
基金supported by the National Natural Science Foundation of China Projects under Grant(nos.52301112,52331004,U21A2049,and 51871211)Guangdong Basic and Applied Basic Research Foundation(Grant no.2024A1515030065)+4 种基金Basic and Applied Basic Research Project of Guangzhou(Grant no.2024A04J6299)LiaoNing Revitalization Talents Program(XLYC1907062,and XLYC2403026)Shenyang Young and Middle-aged Science and Technology Innovation Talent Support Program(RC231178)the Fundamental Research Funds for the Central Universities(N25GFY002)the Innovation Fund of Institute of Metal Research(IMR),Chinese Academy of Sciences(CAS).
文摘Mg-Li alloys hold significant potential for applications in aerospace,automotive manufacturing,military weaponry,and biomedical implants,due to their excellent recyclability,high specific strength,biocompatibility,and superior electromagnetic shielding properties.However,their poor corrosion resistance and high susceptibility to environmentally assisted cracking(EAC)significantly limit broader application.In recent years,growing attention has been directed toward understanding the corrosion and EAC behavior of Mg-Li alloys,as localized corrosion areas and hydrogen generated during the corrosion process can serve as crack initiation points and promote crack propagation.A comprehensive understanding of these mechanisms is essential for enhancing the reliability and performance of Mg-Li alloys in practical environments.This paper presents a detailed review of corrosion and EAC in Mg-Li alloys,focusing on corrosion behavior,crack initiation and propagation mechanisms,and the key factors influencing these processes.It summarizes recent advances in alloying,heat treatment,mechanical processing,microstructural control,environmental influences,mechanical loading,and surface treatments.In addition,the paper explores future research directions,highlights emerging trends,and proposes strategies to improve the durability and service performance of Mg-Li alloys.
基金financially supported by the National Natural Science Foundation of China under Grant Nos.52305467,52188102,U22A20196,and 52075201the Guangdong Basic and Applied Basic Research Foundation Nos.2023A1515010081 and 2022B1212020003the Fundamental Research Funds for the Central Universities under Grant No.YCJJ20230360.
文摘Solidification cracking(SC)of 2024 high-strength aluminium alloy during fusion welding or additive manufacturing has been a long-term issue.In this work,crack-free weld could be obtained using a Zr-core-Alshell wire(ZCASW filler material,a novel filler)coupled with an oscillating laser-arc hybrid welding process,and we investigated the solidification cracking susceptibility(SCS)and cracking behavior of AA2024 weld fabricated with different filler materials.The cracking inhibition mechanism of the weld fabricated with ZCASW filler material was elucidated by combined experiments and phase-field simulation.The results show that the effectiveness of filler materials in reducing the SC gradually improves in the order of ER2319 filler material<ER4043 filler material<ZCASW filler material.The main cracking(when using the ER2319 filler material)branches and the micro cracking branches interact with each other to produce cracking coalescence,which aggravates the cracking propagation.The formation of the Al_(3) Zr phase(when using the ZCASW filler material)promotes heterogeneous nucleation of α-Al,thereby resulting in finer and equiaxed non-dendrite structures,which shortens the liquid phase channels and decreases cracking susceptibility index|d T/d(f_(s))^(1/2)|(T is temperature and f_(s) is solidification fraction)at final solidification.A higher proportion(7.65%area fraction)of inter-dendrite phase with spherical distribution state,a shorter(8.6 mm liquid channel length)inter-dendrite phase coupled with round non-dendrite structure(6μm dendrite size)effectively inhibit the SC.The present study can be a useful database for welding and additive manufacturing of AA2024.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.2022CDJQY-012)the Innovation Group Science Foundation of the Natural Science Foundation of Chongqing,China(Grant No.cstc2020jcyj-cxttX0003).
文摘Coralline soils,specialized materials found extensively in the South China Sea,are playing an increasingly vital role in engineering projects.However,like most terrigenous soils,fine-grained coral soil is prone to shrinkage and cracking,which can significantly affect its engineering properties and ultimately jeopardize engineering safety.This paper presents a desiccation cracking test of fine-grained coral soil,with a particular focus on the thickness effect.The study involved measuring the water content and recording the evolution of desiccation cracking.Advanced image processing technology is employed to analyze the variations in crack parameters,clod parameters,fractal dimensions,frequency distributions,and desiccation cracking propagation velocities of fine-grained coral soil.Furthermore,the dynamic evolution of desiccation cracking under the influence of layer thickness is analyzed.A comprehensive crack evolution model is proposed,encompassing both top-down and bottom-up crack propagation,as well as internal tensile cracking.This work introduces novel metrics for the propagation velocity of the total crack area,the characteristic propagation velocities of desiccation cracks,and the acceleration of crack propagation.Through data fitting,theoretical formulas for soil water evaporation,propagation velocities of desiccation cracks,and crack propagation acceleration are derived,laying a foundation for future soil cracking theories.
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFC3707900 and 2024YFC3012700)the National Natural Science Foundation of China(Grant No.42230710).
文摘Soil desiccation cracking is ubiquitous in nature and has significantpotential impacts on the engineering geological properties of soils.Previous studies have extensively examined various factors affecting soil cracking behavior through a numerous small-sample experiments.However,experimental studies alone cannot accurately describe soil cracking behavior.In this study,we firstly propose a modeling framework for predicting the surface crack ratio of soil desiccation cracking based on machine learning and interpretable analysis.The framework utilizes 1040 sets of soil cracking experimental data and employs random forest(RF),extreme gradient boosting(XGBoost),and artificialneural network(ANN)models to predict the surface crack ratio of soil desiccation cracking.To clarify the influenceof input features on soil cracking behavior,feature importance and Shapley additive explanations(SHAP)are applied for interpretability analysis.The results reveal that ensemble methods(RF and XGBoost)provide better predictive performance than the deep learning model(ANN).The feature importance analysis shows that soil desiccation cracking is primarily influencedby initial water content,plasticity index,finalwater content,liquid limit,sand content,clay content and thickness.Moreover,SHAP-based interpretability analysis further explores how soil cracking responds to various input variables.This study provides new insight into the evolution of soil cracking behavior,enhancing the understanding of its physical mechanisms and facilitating the assessment of potential regional development of soil desiccation cracking.
基金supported by the National Natural Science Foundation of China(Grant No.52278333)the China Scholarship Council(CSC)and the Science and Technology Department of Liaoning Province(Grant No.2024JH2/102500069).
文摘Peridynamics(PD)is an effective method for simulating the spontaneous initiation and propagation of tensile cracks in materials.However,it faces great challenges in simulating compression-shear cracking of geomaterials due to the lack of efficient contact-friction models.This paper introduces an original contact-friction model that leverages twin mesh and potential function principles within PD to model rock cracking under tensile and compressive stresses.The contact detection algorithm,based on space segmentation axis-aligned bounding box(AABB)tree data structure,is used to address the significant challenge of highly efficient contact detection in compression and shear problems.In this method,the twin mesh and potential function are utilized to quantify contact detection and contact degree,as well as friction behavior.This is in contrast to the distance and circular contact area model,which lacks physical significance in the classical PD method.As demonstrated by the tests on specimens containing cracks,the proposed model can capture 8 types of secondary fractures,reduce the contact detection error by about 29%e56%,and increase the contact retrieval efficiency by over 1600 times compared to the classic PD models.This significantly enhances the capability of PD to simulate the initiation,expansion,and coalescence of intricate compression-shear cracks.
基金the financial support by the National Natural Science Foundation of China(Grant No.52108397)“Xiaohe”Science and Technology Talent Special Project(Grant No.2024 TJ-X06)Water Resources Science and Technology Project of Hunan Province(Grant No.XSKJ2023059-41).
文摘Cracking affected by wetting-drying cycles is a major cause of shallow failure of soft rock slopes.Knowledge of rock tensile properties and cracking behaviors helps better assess the stability of soft rock slopes.This study aims to examine the cracking behaviors and tensile strength of silty mudstone under wetting-drying cycles.The wetting-drying cycle and Brazilian splitting tests were performed on silty mudstone considering various cycle number and amplitude.The cracking behaviors of wetting-drying cycles were analyzed by digital image correlation,three-dimensional(3D)scanning technology,and scanning electron microscopy.The results reveal a spiral-like pattern of crack ratio escalation in silty mudstone,with a higher crack ratio observed during drying than wetting.Tensile strength and fracture energy correlate negatively with cycle number or amplitude,with cycle number exerting a more pronounced effect.The variance of the maximum principal strain reflects stages of initial deformation,linear deformation,strain localization,and stable deformation.The formation of strain localization zones reveals the physical process of crack propagation.Crack tip opening displacement progresses through stages of slow growth,exponential growth,and linear growth,delineating the process from crack initiation to stable extension.Failure modes of silty mudstone primarily involve tensile and tensile-shear failure,influenced by the geometric parameters of cracks induced by wetting-drying cycles.Fracture surface roughness and fractal dimension increase with cycle number due to mineral dissolution,physical erosion,and nondirectional crack propagation.Hydration-swelling and dehydration-shrinkage of clay minerals,along with absorption-drying cracking,initiate and merge cracks,leading to degradation of the rock mechanical properties.The findings could provide insights for mitigating shallow cracking of soft rock slopes under wetting-drying cycles.
基金supported by the National Science and Technology Resources Investigation Program of China(Grant No.2021FY100604).
文摘There remains debate on whether Mn is beneficial or detrimental to hydrogen embrittlement in stainless steel.In this work,a series of stainless steels were designed to study the change of hydrogen embrittlement sensitivity,crack propagation,and hydrogen trapping behaviors upon Mn addition.The results suggest that adding 4 wt.% Mn increased hydrogen embrittlement susceptibility,whereas adding 8 wt.% Mn decreased hydrogen embrittlement sensitivity.Forming banded α’-martensite through austenitic grain is the main reason for the increased hydrogen embrittlement sensitivity when adding 4 wt.%Mn,by adsorbing hydrogen,promoting crack initiation,and accelerating crack propagation.
文摘A comparative study of products of thermal and thermocatalytic cracking of polypropylene(PP) in the presence of potassium polytitanate(PPT) synthesized by treatment of TiO_(2)(rutile) powder with molten mixture of KOH and KNO_(3) taken in a weight ratio of 30∶30∶40 has been carried out.It was shown that the studied type of PPT powder exhibits catalytic properties in the reaction of thermal decomposition of PP,compared to the effect of commercial zeolite catalyst CBV-780 traditionally used for this purpose.Based on the analysis performed,the differences in the mechanism of catalytic action of PPT and the zeolite were considered.The reasons for the observed differences in the composition of PP cracking products and in the rate of coke formation on the surface of studied catalysts were analyzed.Considering the obtained results,it has been proposed that the CBV-780 catalyst promoted more intensive production of the gaseous hydrocarbons compared to PPT,due to higher specific surface area(internal surface) accessible for relatively light and small-sized hydrocarbon products of cracking.However,intensive coke formation on the outer surface of the microporous zeolite contributes to the blocking of transport channels and the rapid loss of catalytic action.At the same time,PPT,which initially has a smaller specific surface area,retains its catalytic activity significantly longer due to slit-shaped flat pores and higher transport accessibility of the inner surface.
基金National Natural Science Foundation of China (No. 51975200)Hunan Provincial Innovation Foundation for Postgraduate,China (No. QL20220201)。
文摘By using fatigue crack propagation testing and microstructural characterization,the crack fracture and propagation mechanisms of K4169 superalloy under various loads were investigated.The results demonstrate that the grain sizes of K4169 superalloy significantly increase,and the precipitation of the needle-likeδphase and the Laves phase is observed.Voids and microcracks form at location of Laves phase enrichment,creating conditions for crack propagation.By the a−N(a is the crack length,and N is the number of cycles)relationship curve,the change in the fatigue crack growth rate with the increasing number of cycles progresses through three separate stages.The fracture process of K4169 superalloy under low-stress cyclic loading(3 kN)exhibits the ductile fracture.Subsequently,the fracture process starts to change from the ductile fracture to the brittle fracture as the stress increases to 4.5 kN.In the microstructures of fractures in both stress states,intergranular propagation is the mechanism responsible for crack propagation.Moreover,the Laves phase exists near the fracture crack,which is in line with the post-service structural phenomenon.
基金supported by the National Natural Science Foundation of China(Nos.52204401,52005432)Hebei Natural Science Foundation of China(No.E2021203179),Excellent Young Talents Program of University of Anhui Province,China(No.gxyq2022093)Excellent Youth Research Projects in Universities of Anhui Province,China(No.2022AH030153).
文摘The edge crack behavior of copper foil in asymmetrical micro-rolling was studied.The effects of the speed ratio between rolls,grain size and stress state in the deformation zone on edge cracks of the rolled piece in asymmetrical rolling were analyzed.Low plasticity,uneven deformation and longitudinal secondary tensile stress generated in the edge area of the rolled piece during the rolling process are the main causes of edge cracks.The larger the grain size of the rolled piece,the smaller the number of edge cracks and the deeper the expansion depth,and the larger the spacing between cracks under the same rolling reduction.Asymmetrical rolling can effectively increase the rolling reduction at when the copper foil fist shows edge cracks compared to symmetrical rolling.This enhancement is attributed to the shearing stress induced by asymmetrical rolling,which reduces the rolling force and longitudinal secondary tensile stress,and increases the residual compressive stress on the surface of the rolled piece.The edge crack defects of copper foil can be effectively reduced by increasing the speed ratio between the rolls in asymmetrical rolling.
基金The financial support provided by the Project of the National Natural Science Foundation of China (22308314,U22A20415)the Natural Science Foundation of Zhejiang Province (LQ24B060001)+1 种基金the "Pioneer" and "Leading Goose" Research & Development Program of Zhejiang (2022C01SA442617)the SINOPEC Technology Development Project (224244)
文摘This study leverages machine learning to perform high-throughput computational screening of n-hexane cracking initiators.Artificial neural networks are applied to predict the chemical performance of initiators,using simulated pyrolysis data as the training dataset.Various feature extraction methods are utilized,and five neural network architectures are developed to predict the co-cracking product distribution based on molecular structures.High-throughput screening of 12946 molecules outside the training dataset identifies the top 10 initiators for each target product—ethylene,propylene,and butadiene.The relative error between predicted and simulated values is less than 7%.Additionally,reaction pathway analysis elucidates the mechanisms by which initiators influence the distribution of cracking products.The proposed framework provides a practical and efficient approach for the rapid identification and evaluation of high-performance cracking initiators.
基金supported by the National Natural Science Foundation of China(No.52075235)the Major Science and Technology Project of Gansu Province,China(No.22ZD6GA008)+2 种基金the Key Research and Development Program of Gansu Province,China(No.20YF3WA017)the Natural Science Foundation of Gansu Province,China(No.21JR7RA233)the Scientific and Technological Projects of Jiayuguan,China(No.22-16)。
文摘The 7075 aluminum alloy was subjected to power-modulated laser welding using a full-domain power modulation(FDPM)laser oscillating welding system.Three different power modes were utilized:constant power(CP),gradient power(GP),and alternating power(AP)modes.The impact of different power modes on joint crack sensitivity,microstructure,and residual stress was assessed.The results demonstrate that joint welded with the AP mode exhibits the lowest sensitivity to solidification cracking(with mean crack sensitivity of 18.3%),and the smallest average grain size in the fusion zone of the weld seam(80μm).Additionally,it shows the highest microhardness(HV 113)and the narrowest softening region(3.5 cm).Furthermore,the joint displays the lowest residual stress and cooling rate,which is the reason for its minimal crack sensitivity.
基金the National Natural Science Foundation of China(Nos.52471012,52471043).
文摘This study investigates the stress corrosion cracking(SCC)behavior of a Mg-8Gd-3Y-0.5Zr alloy in a 3.5 wt.%NaCl solution using slow strain rate tensile(SSRT)testing.The results reveal that SCC suscepti-bility increases as the strain rate decreases,with hydrogen embrittlement(HE)becoming more dominant at lower strain rates,leading to brittle fracture.Anodic dissolution(AD)plays a more significant role at higher strain rates,resulting in mixed fracture modes.Additionally,the mechanical properties and SCC resistance are strongly influenced by the sample orientation.TD-oriented samples show higher SCC susceptibility than RD-oriented ones due to the alignment of Gd-and Y-rich precipitates and grain boundaries,which act as initiation sites for SCC.These precipitates form micro-galvanic couples with the Mg matrix,accelerating localized corrosion and HE.The findings provide insights into the SCC mechanisms of VW83 alloy and highlight the importance of optimizing microstructure and processing conditions to improve its corrosion resistance.
基金financially supported by the National Natural Science Foundation of China(No.U21A2050)support of the Chinese Scholarship Council(No.202006290165).
文摘In recent years,(0001)twist grain boundaries(BTGBs)located in primary α grain clusters were identified as fatigue crack nucleation sites in different Ti alloys.In the present study,crack initiation was investigated in a bimodal Ti-5Al-4 V alloy subjected to low-cycle fatigue and dwell-fatigue loadings at room temperature.The low fraction of primary α grains was not associated with a lack of sensitivity to BTGB cracking.Transmission electron microscopy and electron back-scattered diffraction were used to characterize BTGBs in the initial microstructure.The fatigue mechanisms were then analyzed with a focus on dislocation activity.α_(p) grains adjacent to cracked BTGBs contained a high dislocation density.It was primarily composed of planar slip bands of dislocations.In addition,<c+a>dislocations were noticed in the vicinity of cracked BTGBs.They supposedly pertain to crack tip plasticity during growth,and no evidence of a role of an incoming slip event in crack nucleation was obtained.Also,basal slip bands extending across adjacent grains were found to emerge from BTGBs.This feature provides an easier path for crack extension when growth along the grain boundary becomes difficult owing to a deviation from the basal plane.Atom probe tomography analyses evidenced V and Fe segregation at a grain boundary with a significant deviation from the BTGB configuration.This suggests a possible contribution of local solute segregation to the high cracking resistance of general α_(p)/α_(p) grain boundaries.This work provides new insights into the mechanisms involved in cracking of BTGB in Ti alloys subjected to cyclic loadings.
基金supported by National Natural Science Foundation of China(Nos.52325406 and 52374330)Fundamental Research Funds for the Central Universities(No.N2225046).
文摘A mathematical model coupling flow,solidification,strain-stress,and interface failure was developed.Following identification of crack source type through thermal tensile experiment and validation by strain-stress comparison,the model was used to investigate slab cracking tendency near precipitated phases,considering various locations,sizes and shapes of them.The results show that the jet from submerged entry nozzle creates a“double roll”flow pattern during continuous casting,resulting in more uniform temperature distributions at slab corner and wide surface center compared with narrow surface center.Consequently,precipitated phases,particularly those located on the narrow surface,readily induce stress concentration and thus increase cracking tendency.A smaller precipitated phase size can reduce the stress concentration zone,while a more spherical shape can distribute surrounding stress along its surface and lower the internal stress within it,thereby decreasing the risk of slab cracking during continuous casting.The optimal precipitated phase exhibits a spherical or ellipsoidal shape with a major axis of less than 5µm,minimizing its potential to initiate cracks.
基金supported by the National Natural Science Foundation of China(Grant No.42277124)the National Key Research&Development Program of China(Grant No.2020YFC1808004)the Jiangsu Province 333 Talents Youth Talent Support Project.
文摘In subtropical regions,soil desiccation cracking often exerts a significant impact on the interactions between soil water and the atmosphere,making it a subject of great interest in the fields of geotechnical and geoenvironmental engineering.Despite the growing utilization of biochar as a sustainable soil amendment,there remains a lack of in-depth understanding of biocharewateresoil interactions,as well as its impact on soil desiccation cracking behavior.To address this gap,this study investigated the influence and mechanism of woody biochar dosages and particle sizes on the cracking behavior of three typical clayey soils in subtropical regions in China,namely Pukou expansive soil(PKE),Xiashu soil(XS),and Zhongshan lateritic soil(ZSL).The quantitative analysis of crack images revealed that the use of biochar was not consistently effective in preventing soil cracking.The application of biochar reduced the crack ratio in PKE and XS by up to 24.03%and 53.89%,respectively.In contrast,ZSL exhibited a 74.57%increase in crack ratio with the addition of 10%biochar.This influence can be further enhanced by increasing the dosage and reducing the particle size of biochar.The microstructural analysis demonstrated that biochar exerts an inhibitory effect on PKE and XS primarily through direct replacement,direct barrier,and indirect physical mechanisms.Moreover,an indirect chemical effect between biochar and clay particles was proposed to explain the exacerbated cracking observed in biochar-amended ZSL.To effectively utilize biochar for soil cracking mitigation in subtropical regions,it is essential to evaluate the initial mineral composition and cation type of the soil.
