Because of the developed surface of the Triply PeriodicMinimumSurface(TPMS)structures,polylactide(PLA)products with a TPMS structure are thought to be promising bio soluble implants with the potential for targeted dru...Because of the developed surface of the Triply PeriodicMinimumSurface(TPMS)structures,polylactide(PLA)products with a TPMS structure are thought to be promising bio soluble implants with the potential for targeted drug delivery.For implants,mechanical properties are key performance characteristics,so understanding the deformation and failure mechanisms is essential for selecting the appropriate implant structure.The deformation and fracture processes in PLA samples with different interior architectures have been studied through computer simulation and experimental research.Two TPMS topologies,the Schwarz Diamond and Gyroid architectures,were used for the sample construction by 3D printing.ANSYS software was utilized to simulate compressive deformation.It was found that under the same load,the vonMises stresses in the Gyroid structure are higher than those in the Schwartz Diamond structure,which was associated with the different orientations of the cells in the studied structures in relation to the direction of the loading axis.The deformation process occurs in the local regions of the studied TPMS structures.Maximum von Mises stresses were observed in the vertical parts of the structures oriented along the load direction.It was found that,unlike the Gyroid,the Schwartz Diamond structure contains a frame that forms unique stiffening ribs,which ensures the redistribution of the load under the vertical loading direction.An analysis of the mechanical characteristics of PLA samples with the Schwartz Diamond and Gyroid structures produced by the Fused Deposition Modeling(FDM)method was correlated with computer simulation.The Schwarz Diamond-type structure was shown to have a higher absorption energy than the Gyroid one.A study of the fracture in PLA samples with various cell sizes revealed a particular feature related to the samples’periodic surface topology and the 3D printing process.Scanning electron microscopic(SEM)studies of the samples deformed by compression showed thatwith an increase in the density of the samples,the failure mechanism changes from ductile to quasi-brittle due to the complex participation of both cell deformation and fiber deformation.展开更多
This study comprehensively uses various methods such as production dynamic analysis,fluid inclusion thermometry and carbon-oxygen isotopic compositions testing,based on outcrop,core,well-logging,3D seismic,geochemistr...This study comprehensively uses various methods such as production dynamic analysis,fluid inclusion thermometry and carbon-oxygen isotopic compositions testing,based on outcrop,core,well-logging,3D seismic,geochemistry experiment and production test data,to systematically explore the control mechanisms of structure and fluid on the scale,quality,effectiveness and connectivity of ultra-deep fault-controlled carbonate fractured-vuggy reservoirs in the Tarim Basin.The results show that reservoir scale is influenced by strike-slip fault scale,structural position,and mechanical stratigraphy.Larger faults tend to correspond to larger reservoir scales.The reservoir scale of contractional overlaps is larger than that of extensional overlaps,while pure strike-slip segments are small.The reservoir scale is enhanced at fault intersection,bend,and tip segments.Vertically,the heterogeneity of reservoir development is controlled by mechanical stratigraphy,with strata of higher brittleness indices being more conducive to the development of fractured-vuggy reservoirs.Multiple phases of strike-slip fault activity and fluid alterations contribute to fractured-vuggy reservoir effectiveness evolution and heterogeneity.Meteoric water activity during the Late Caledonian to Early Hercynian period was the primary phase of fractured-vuggy reservoir formation.Hydrothermal activity in the Late Hercynian period further intensified the heterogeneity of effective reservoir space distribution.The study also reveals that fractured-vuggy reservoir connectivity is influenced by strike-slip fault structural position and present in-situ stress field.The reservoir connectivity of extensional overlaps is larger than that of pure strike-slip segments,while contractional overlaps show worse reservoir connectivity.Additionally,fractured-vuggy reservoirs controlled by strike-slip faults that are nearly parallel to the present in-situ stress direction exhibit excellent connectivity.Overall,high-quality reservoirs are distributed at the fault intersection of extensional overlaps,the central zones of contractional overlaps,pinnate fault zones at intersection,bend,and tip segments of pure strike-slip segments.Vertically,they are concentrated in mechanical stratigraphy with high brittleness indices.展开更多
This paper prepared a novel as-cast W-Zr-Ti metallic ESM using high-frequency vacuum induction melting technique.The above ESM performs a typical elastic-brittle material feature and strain rate strengthening behavior...This paper prepared a novel as-cast W-Zr-Ti metallic ESM using high-frequency vacuum induction melting technique.The above ESM performs a typical elastic-brittle material feature and strain rate strengthening behavior.The specimens exhibit violent chemical reaction during the fracture process under the impact loading,and the size distribution of their residual debris follows Rosin-Rammler model.The dynamic fracture toughness is obtained by the fitting of debris length scale,approximately 1.87 MPa·m~(1/2).Microstructure observation on residual debris indicates that the failure process is determined by primary crack propagation under quasi-static compression,while it is affected by multiple cracks propagation in both particle and matrix in the case of dynamic impact.Impact test demonstrates that the novel energetic fragment performs brilliant penetration and combustion effect behind the front target,leading to the effective ignition of fuel tank.For the brittleness of as-cast W-ZrTi ESM,further study conducted bond-based peridynamic(BB-PD)C++computational code to simulate its fracture behavior during penetration.The BB-PD method successfully captured the fracture process and debris cloud formation of the energetic fragment.This paper explores a novel as-cast metallic ESM,and provides an available numerical avenue to the simulation of brittle energetic fragment.展开更多
Accurate prediction of coal reservoir permeability is crucial for engineering applications,including coal mining,coalbed methane(CBM)extraction,and carbon storage in deep unmineable coal seams.Owing to the inherent he...Accurate prediction of coal reservoir permeability is crucial for engineering applications,including coal mining,coalbed methane(CBM)extraction,and carbon storage in deep unmineable coal seams.Owing to the inherent heterogeneity and complex internal structure of coal,a well-established method for predicting permeability based on microscopic fracture structures remains elusive.This paper presents a novel integrated approach that leverages the intrinsic relationship between microscopic fracture structure and permeability to construct a predictive model for coal permeability.The proposed framework encompasses data generation through the integration of three-dimensional(3D)digital core analysis and numerical simulations,followed by data-driven modeling via machine learning(ML)techniques.Key data-driven strategies,including feature selection and hyperparameter tuning,are employed to improve model performance.We propose and evaluate twelve data-driven models,including multilayer perceptron(MLP),random forest(RF),and hybrid methods.The results demonstrate that the ML model based on the RF algorithm achieves the highest accuracy and best generalization capability in predicting permeability.This method enables rapid estimation of coal permeability by inputting two-dimensional(2D)computed tomography images or parameters of the microscopic fracture structure,thereby providing an accurate and efficient means of permeability prediction.展开更多
Faults and fractures of multiple scales are frequently induced and generated in compressional structural system. Comprehensive identification of these potential faults and fractures that cannot be distinguished direct...Faults and fractures of multiple scales are frequently induced and generated in compressional structural system. Comprehensive identification of these potential faults and fractures that cannot be distinguished directly from seismic profile of the complex structures is still an unanswered problem. Based on the compressional structural geometry and kinematics theories as well as the structural interpretation from seismic data, a set of techniques is established for the identification of potential faults and fractures in compressional structures. Firstly, three-dimensional(3D) patterns and characteristics of the faults directly interpreted from seismic profile were illustrated by 3D structural model. Then, the unfolding index maps, the principal structural curvature maps, and tectonic stress field maps were obtained from structural restoration. Moreover, potential faults and fractures in compressional structures were quantitatively identified relying on comprehensive analysis of these three maps. Successful identification of the potential faults and fractures in Mishrif limestone formation and in Asmari dolomite formation of Buzurgan anticline in Iraq demonstrates the applicability and reliability of these techniques.展开更多
Eigenstructure-based coherence attributes are efficient and mature techniques for large-scale fracture detection. However, in horizontally bedded and continuous strata, buried fractures in high grayscale value zones a...Eigenstructure-based coherence attributes are efficient and mature techniques for large-scale fracture detection. However, in horizontally bedded and continuous strata, buried fractures in high grayscale value zones are difficult to detect. Furthermore, middleand small-scale fractures in fractured zones where migration image energies are usually not concentrated perfectly are also hard to detect because of the fuzzy, clouded shadows owing to low grayscale values. A new fracture enhancement method combined with histogram equalization is proposed to solve these problems. With this method, the contrast between discontinuities and background in coherence images is increased, linear structures are highlighted by stepwise adjustment of the threshold of the coherence image, and fractures are detected at different scales. Application of the method shows that it can also improve fracture cognition and accuracy.展开更多
Effect of network structure on plasticity and fracture mode of Zr？Al？Ni？Cu bulk metallic glasses （BMGs） was investigated. The microstructures of transversal and longitudinal sections were exposed by chemical etch...Effect of network structure on plasticity and fracture mode of Zr？Al？Ni？Cu bulk metallic glasses （BMGs） was investigated. The microstructures of transversal and longitudinal sections were exposed by chemical etching and observed by scanning electron microscopy （SEM）. The mechanical properties were examined by room-temperature uniaxial compression test. The results show that both plasticity and fracture mode are significantly affected by the network structure and the alteration occurs when the size of the network structure reaches up to a critical value. When the cell size （dc） of the network structure is ~3μm, Zr-based BMGs characterize in plasticity that decreases with increasingdc. The fracture mode gradually transforms from single 45° shear fracture to double 45° shear fracture and then cleavage fracture with increasingdc. In addition, the mechanisms of the transition of the plasticity and the fracture mode for these Zr-based BMGs are also discussed.展开更多
The Urumqi foreland thrust tectonic belt exhibits complex geological structures and strong seismicity.Imaging its shallow crustal structure is of great significance for understanding its tectonic mechanism and seismog...The Urumqi foreland thrust tectonic belt exhibits complex geological structures and strong seismicity.Imaging its shallow crustal structure is of great significance for understanding its tectonic mechanism and seismogenic environment.We obtained a high-resolution S-wave velocity model of the shallow crust at depths of 0–8 km using ambient noise tomography applied to data from a dense seismic array.Sediments are generally thinner in the southeast and thicker in the northwest,with a maximum thickness of more than 8 km.Variations in the velocity structure near the Xishan,Wanyaogou,and Yamalike faults indicate that their formation was related to differences in the physical properties on either side of the fault.In addition,the faults exhibit thrusting of the low-velocity sides towards the high-velocity sides.In the study area,earthquakes rarely occur at depths of less than 3 km and are mostly concentrated in the high-velocity zone in the southern part.Below 3 km depth,more earthquakes were observed,mainly distributed near faults or in relatively high-velocity areas in the southern part.This suggests that high-velocity structures are more prone to stress accumulation,resulting in earthquakes.At 6–8 km depth,the densely distributed earthquakes in the northwestern part of the Bogda mountains are well-aligned with the northwest-oriented low-velocity zone observed in this study,suggesting that this weak zone likely controls seismicity in this area.展开更多
The strike-slip fault system in the central Tarim Craton controls a complex petroleum system with estimated reserves exceeding 1×10^(9)t,the fault-related fractures are important for hydrocarbon accumulation.In t...The strike-slip fault system in the central Tarim Craton controls a complex petroleum system with estimated reserves exceeding 1×10^(9)t,the fault-related fractures are important for hydrocarbon accumulation.In this paper,the basic parameters such as density and width of fractures are counted and classified,and the effects of fractures on reservoirs are analyzed.The results show that:(1)Structural fractures and stylolite were widely developed in Halahatang area and experienced at least three stages of activity based on the infilling materials and crosscutting relationship.(2)Fracture density,width,aperture,and dip angle vary in different wells,but the relationship between the above parameters and the distance to the fault core indicates the fracture differences in the fault damage zone and further provides a method to divide the inner units in the fault damage zone.In addition,oil and gas wells with high production mainly concentrate in the inner unit.(3)The infilling materials and degree of fractures vary.Fractures formed in the early stage are more filled and less open,while the fractures formed in the late stage are relatively less filled and more open.(4)Fractures improve porosity to a certain extent but greatly increase permeability,especially in the inner zone of fault damage zone with large quantity,multiple inclinations,less filling and large width.These features contribute to the formation of a higher-quality reservoir,further improving oil and gas production.This paper provides a quantitative characterization method for the study of strike-slip fault-related fracture-caved reservoirs,and points out that fault damage zone,especially the inner zone of the fault damage zone,is the potential goal for oil and gas exploration.展开更多
Natural fractures controlled by faults in ultradeep carbonate strata play substantial roles as both fluid migration channels and storage spaces.However,characterizing the heterogeneous distribution of underground frac...Natural fractures controlled by faults in ultradeep carbonate strata play substantial roles as both fluid migration channels and storage spaces.However,characterizing the heterogeneous distribution of underground fractures within the complex three-dimensional geometry of strike-slip fault zones remains challenging.This study investigates the characteristics of natural fractures controlled by strike-slip faults in the fractured Middle and Lower Ordovician reservoirs of the central and northern Tarim Basin,China.Seismics,cores,and image logs were integrated to quantitatively analyze the intensity and dip angle of natural fractures and findings were verified using published sandbox simulations.The carbonate reservoir contains three main types of natural fractures:tectonic fractures,abnormal high-pressure-related fractures,and stylolites.Strike-slip faults control the distribution and characteristics of tectonic fractures across various scales.Generally,both fracture intensity and porosity exhibit a decreasing trend as the distance from the main fault surface increases.Compared with those in non-stepover zones along a strike-slip fault,natural fractures and faults in stepover zones are more developed along the fault strike,with significantly greater development intensity in central stepover regions than that at its two ends.Furthermore,strike-slip faults influence the dip angles of both natural fractures and secondary faults.The proportion of medium-to-low-dip angle fractures and faults in the stepover zone is greater than that in the non-stepover zone.Additionally,the proportion of medium-to low-dip angle fractures and faults in the middle of the stepover is greater than that at both ends.Therefore,strike-slip fault structures control the dip angle of natural fracture and the heterogeneity of secondary fault and fracture intensity.The linking damage zone in the stepover contains a larger volume of fractured rocks,making it a promising petroleum exploration target.The development of stepovers and the orientation of present-day in-situ stress substantially influence the productivity of fractured reservoirs controlled by strike-slip faults.The analysis in this study reveals that reservoir productivity increases as the angle between the strike-slip fault segment and the maximum horizontal principal stress decreases.This study provides valuable insights for quantitatively evaluating fracture heterogeneity in fractured reservoirs and establishing optimized selection criteria for favorable targets in fault-related fractured reservoirs.展开更多
Through investigating and comparing the mechanical behavior of an as-rolled Mg-3%Al-1%Zn(wt%)alloy before and after annealing treatments,it was revealed that the formation of annealing-tailored bimodal grain structure...Through investigating and comparing the mechanical behavior of an as-rolled Mg-3%Al-1%Zn(wt%)alloy before and after annealing treatments,it was revealed that the formation of annealing-tailored bimodal grain structure ensured the 330℃/4 h samples having a good combination of tensile strength and plasticity.Failure analysis demonstrated that for the as-rolled and 330℃/1 h samples with fine grain structure,their plastic deformation was mainly attributed to basal slips,whereas the deformation mechanism in the bimodal grain-structured samples was dominated by basal slips in fine grains and twinning in coarse grains.For the 330℃/8 h samples with coarse grain structure,high densities of twins were activated.Meanwhile,basal slips occurred in the twinned and un-twinned areas of coarse grains and could pass through twin boundaries.For differently treated samples,cracking preferentially occurred along slip bands,resulting in their transgranular fractures.展开更多
Secondary/minor structures occurring along the main fault surfaces are important indicators for judging the kinematic characteristics of faults.However,many factors can lead to the formation of these structures,which ...Secondary/minor structures occurring along the main fault surfaces are important indicators for judging the kinematic characteristics of faults.However,many factors can lead to the formation of these structures,which results in the difficulty for rapid judgment and application in the fields.A series of secondary faults/fractures developed due to the movement of main faults are the most important and widespread phenomena in the scope of brittle deformation.The morphology of the main fault surfaces is various,and former researchers mainly discussed the structures on the main even fault surfaces. However,the fluctuation of fault surfaces is the intrinsic character of the faults,and the intersection between the main fault and secondary faults/fractures can produce a series of kinematic indicators on the main fault surfaces.Based on previous studies and our observations,i.e.the structural traces of the P,R,R',T and X shears/faults along the main faults,some indicators which are rarely reported previously,are described in the paper.Furthermore,their reliabilities are also discussed,and more practical and reliable criteria are brought forward.We suggest that the simple application of congruous and incongruous steps without knowing their exact origins should be abandoned in the fields,and several types of indicators along one fault surface should be checked with each other as much as possible.Meanwhile,the origins of some other arcuate indicators on the fault surfaces are also discussed,and new models are brought forward.展开更多
The complex Red River fault zone(RRFZ),which is situated in the southwestern region of China and separates the Indochina plate and South China blocks,has diverse seismic activities in different segments.To reveal the ...The complex Red River fault zone(RRFZ),which is situated in the southwestern region of China and separates the Indochina plate and South China blocks,has diverse seismic activities in different segments.To reveal the detailed geometric characteristics of the RRFZ at different sections and to better understand the seismogenic environment,in 2022 and 2023 we deployed 7 seismic dense linear arrays,consisting of 574 nodal stations,across the RRFZ in the northern and southern segments near the towns Midu,Gasa,Zhega,Dazhai,Xinzhai,and Taoyuan.The linear arrays,which extend from 2.4 to 12.5 km in length with station intervals ranging between 40 and140 m,recorded seismic ambient noise for approximately one month.Using the extended range phase shift method,we extract the phase velocity dispersion curves of the Rayleigh waves between 0.9 and 10 Hz,which are then used to invert for the high resolution shearwave velocity structures across the RRFZ beneath the linear arrays.The key findings are:(1)the 7 imaged sections of the RRFZ exhibit quite similar structures,with higher velocities on the SW side and lower velocities on the NE side;the velocity variation is consistent with the surface geological structures along the RRFZ;(2)the shear-wave velocities on the SW side of the RRFZ at the northern Midu section and southern Gasa-Dazhai sections are generally higher than their counterparts in the southern Xinzhai-Taoyuan sections,which reflects lithological variations from the marble-dominated Paleoproterozoic Along basement to the gneiss dominated Paleoproterozoic Qingshuihe basement;(3)from the northern Midu section to the southern region where the RRFZ intersects with the Xiaojiang Fault,the major faults of the RRFZ exhibit a consistent high-angle,NE-dipping structure;(4)the low shear-wave velocities immediately to the NE of the velocity boundary may indicate a faulted zone due to long-term shearing,where excessive amplifications of ground motions could occur.This study provides new insights into the characteristics of the shallow structures of the RRFZ.展开更多
To address the issue of extensive deformation in the Tabaiyi Tunnel caused by the fault zone,nuclear magnetic resonance(NMR)technology was employed to analyze the physical and mechanical properties of waterabsorbing m...To address the issue of extensive deformation in the Tabaiyi Tunnel caused by the fault zone,nuclear magnetic resonance(NMR)technology was employed to analyze the physical and mechanical properties of waterabsorbing mudstone.This analysis aimed to understand the mechanism behind the significant deformations.Drawing from the principle of excavation stress compensation,a support scheme featuring NPR anchorcables and an asymmetric truss support system was devised.To validate the scheme,numerical analysis using a combination of the Discrete Element Method(DEM)-Finite Element Method(FEM)was conducted.Additionally,similar material model tests and engineering measurements were carried out.Field experiments were also performed to evaluate the NPR anchor-cable and truss support system,focusing on anchor cable forces,pressures between the truss and surrounding rock,pressures between the initial support and secondary lining,as well as the magnitude of settlement and convergence deformation in the surrounding rock.The results indicate that the waterinduced expansion of clay minerals,resulting from damage caused by fissure water,accelerated the softening of the mudstone's internal structure,leading to significant deformations in the Tabaiyi Tunnel under high tectonic stress.The original support design fell short as the length of the anchor rods was smaller than the expansion depth of the plastic zone.As a result,the initial support structure bore the entire load from the surrounding rock,and a non-coupled deformation contact was observed between the double-arch truss and the surrounding rock.The adoption of NPR asymmetric anchor-cable support effectively restrained the expansion and asymmetric distribution characteristics of the plastic zone.Considering the mechanical degradation caused by water absorption in mudstone,the rigid constraint provided by the truss proved crucial for controlling the stability of the surrounding rock.These research findings hold significant implications for managing large deformations in soft rock tunnels situated within fractured zones under high tectonic stress conditions.展开更多
Long-bone fractures are common complaints in orthopedic surgery.In recent years,significant progress has been made in robot-assisted fracture-reduction techniques.As a key medical device for diverse fracture morpholog...Long-bone fractures are common complaints in orthopedic surgery.In recent years,significant progress has been made in robot-assisted fracture-reduction techniques.As a key medical device for diverse fracture morphologies and sites,the design of the reduction robot has a profound impact on the reduction outcomes.However,existing reduction robots have practical limitations and cannot simultaneously satisfy clinical requirements in terms of workspace,force/torque,and structural stiffness.To overcome these problems,we first analyze the potential placement areas and performance requirements of reduction robots according to clinical application scenarios.Subsequently,a 3UPS/S-3P hybrid configuration with decoupled rotational and translational degrees of freedom(DOFs)is proposed,and a kinematic model is derived to achieve the motion characteristics of the remote center of motion(RCM).Furthermore,the structural design of a hybrid reduction robot with an integrated distal clamp and proximal fixator was completed,and a mechanical prototype was constructed.The results of the performance evaluations and static analysis demonstrate that the proposed reduction robot has acceptable workspace,force,and torque performance and excellent structural stiffness.Two clinical case simulations further demonstrated the clinical feasibility of the robot.Finally,preliminary experiments on bone models demonstrated the potential effectiveness of the proposed reduction robot in lower-limb fracture reduction.展开更多
No earthquake of magnitude six or greater has been recorded historically in the southern segment of the Red River Fault(RRF).This absence constitutes a significant seismic gap, suggesting a risk of future strong earth...No earthquake of magnitude six or greater has been recorded historically in the southern segment of the Red River Fault(RRF).This absence constitutes a significant seismic gap, suggesting a risk of future strong earthquakes. The China Earthquake Science Experimental Site intends to conduct drilling exploration in this area, which necessitates improved knowledge of the fault zone's geometric distribution characteristics and deep structure. We obtained and analyzed audio and broadband magnetotelluric(MT) data collected at one of the alternative drilling stations(in the Dazhai Village of Honghe County). We have used these data to obtain a highresolution 3-D electrical model of this study area's subsurface to a depth of 5 km. We report that the electrical structure from the surface to 0.5 km is relatively complex, characterized by alternating high and low resistivity;below 0.5 km, the electrical structure becomes more simplified. The RRF extends northwest-southeast orientation along the high and low resistivity boundary, dipping northeastward. The electrical structure of the Red River Valley, which the fault zone traverses, reveals low resistivity characteristics with a lateral width of up to2 km. This study offers critical electromagnetic constraints that enhance our understanding of the tectonic characteristics of the RRF. The findings will inform and aid in the design of drilling plans for the southern segment of the RRF region.展开更多
Based on the evolution of fatigue cracks in welded structures,the fatigue life of welded structures was defined as the sum of the crack initiation life Ni and the crack propagation life Np.Correspondingly,a fatigue-li...Based on the evolution of fatigue cracks in welded structures,the fatigue life of welded structures was defined as the sum of the crack initiation life Ni and the crack propagation life Np.Correspondingly,a fatigue-life analysis method combining S-N curves and fracture mechanics theory was proposed.The equivalent structural stress method and the lower 99%boundary of the master S-N curve were used to evaluate Ni,and cracks at the end of the initiation stage were considered as semi-elliptical surface cracks.Moreover,Paris equation and the stress intensity factor range of the cracks were used to evaluate Np.Furthermore,the fatigue test results obtained from the running girder of cranes were used as a reference for comparison and verification of the results.The results revealed that the equivalent structural stress is a good indicator for the crack initiation behavior of complex welded structures.In addition,the predicted fatigue life corresponded closely to the testing life.展开更多
The transient fracture behavior of a functionally graded layered structure subjected to an in-plane impact load is investigated. The studied structure is composed of two homogeneous layers and a functionally gradedint...The transient fracture behavior of a functionally graded layered structure subjected to an in-plane impact load is investigated. The studied structure is composed of two homogeneous layers and a functionally gradedinterlayer with a crack perpendicular to the boundaries. The impact load is applied on the face of the crack. Fourier transform and Laplace transform methods are used to formulate the present problem in terms of a singular integral equation in Laplace transform domain. Considering variations of parameters such as the nonhomogeneity constant, the thickness ratio and the crack length, the dynamic stress intensity factors （DSIFs） in time domain are studied and some meaningful conclusions are obtained.展开更多
Heterogeneous-structured Cu samples composed of coarse-grained(CG) and ultrafine-grained(UFG) domains with a transitional interface were fabricated by friction stir processing, in order to investigate the effect of in...Heterogeneous-structured Cu samples composed of coarse-grained(CG) and ultrafine-grained(UFG) domains with a transitional interface were fabricated by friction stir processing, in order to investigate the effect of interface constraint on the yielding and fracture behaviors. Tensile test revealed that the synergetic strengthening induced by elastic/plastic interaction between incompatible domains increases with increasing the area of constraint interface. The strain distribution near interface and the fracture morphology were characterized using digital image correlation technique and scanning electron microscopy, respectively. Fracture dimples preferentially formed at the interface, possibly due to extremely high triaxial stress and strain accumulation near the interface. Surprisingly, the CG domain was fractured by pure shear instead of the expected voids growth caused by tensile stress.展开更多
We produced a 316 L stainless steel with heterogeneous nanometer-thick lamellar structures by severe cold-rolling at room temperature,and conducted micro-scale tensile tests in different orientations to evaluate both ...We produced a 316 L stainless steel with heterogeneous nanometer-thick lamellar structures by severe cold-rolling at room temperature,and conducted micro-scale tensile tests in different orientations to evaluate both the inplane(parallel to the nano-lamellae)and out-of-plane(normal and 45inclined to the nano-lamellae)mechanical anisotropy.The parallel orientation demonstrates the greatest tensile strength while the inclined orientation exhibits the least strength.The tensile tests in normal and inclined directions also indicate significant transient elastic-plastic response due to the strain path change.Fractographic examination demonstrates that the specimen fails in the normal direction by premature micro-void nucleation and growth,which restricts its tensile strength;however,we identified zig-zag cracking associated with lamellar shear cracking in the inclined direction.展开更多
文摘Because of the developed surface of the Triply PeriodicMinimumSurface(TPMS)structures,polylactide(PLA)products with a TPMS structure are thought to be promising bio soluble implants with the potential for targeted drug delivery.For implants,mechanical properties are key performance characteristics,so understanding the deformation and failure mechanisms is essential for selecting the appropriate implant structure.The deformation and fracture processes in PLA samples with different interior architectures have been studied through computer simulation and experimental research.Two TPMS topologies,the Schwarz Diamond and Gyroid architectures,were used for the sample construction by 3D printing.ANSYS software was utilized to simulate compressive deformation.It was found that under the same load,the vonMises stresses in the Gyroid structure are higher than those in the Schwartz Diamond structure,which was associated with the different orientations of the cells in the studied structures in relation to the direction of the loading axis.The deformation process occurs in the local regions of the studied TPMS structures.Maximum von Mises stresses were observed in the vertical parts of the structures oriented along the load direction.It was found that,unlike the Gyroid,the Schwartz Diamond structure contains a frame that forms unique stiffening ribs,which ensures the redistribution of the load under the vertical loading direction.An analysis of the mechanical characteristics of PLA samples with the Schwartz Diamond and Gyroid structures produced by the Fused Deposition Modeling(FDM)method was correlated with computer simulation.The Schwarz Diamond-type structure was shown to have a higher absorption energy than the Gyroid one.A study of the fracture in PLA samples with various cell sizes revealed a particular feature related to the samples’periodic surface topology and the 3D printing process.Scanning electron microscopic(SEM)studies of the samples deformed by compression showed thatwith an increase in the density of the samples,the failure mechanism changes from ductile to quasi-brittle due to the complex participation of both cell deformation and fiber deformation.
基金Supported by the National Natural Science Foundation of China(U21B2062).
文摘This study comprehensively uses various methods such as production dynamic analysis,fluid inclusion thermometry and carbon-oxygen isotopic compositions testing,based on outcrop,core,well-logging,3D seismic,geochemistry experiment and production test data,to systematically explore the control mechanisms of structure and fluid on the scale,quality,effectiveness and connectivity of ultra-deep fault-controlled carbonate fractured-vuggy reservoirs in the Tarim Basin.The results show that reservoir scale is influenced by strike-slip fault scale,structural position,and mechanical stratigraphy.Larger faults tend to correspond to larger reservoir scales.The reservoir scale of contractional overlaps is larger than that of extensional overlaps,while pure strike-slip segments are small.The reservoir scale is enhanced at fault intersection,bend,and tip segments.Vertically,the heterogeneity of reservoir development is controlled by mechanical stratigraphy,with strata of higher brittleness indices being more conducive to the development of fractured-vuggy reservoirs.Multiple phases of strike-slip fault activity and fluid alterations contribute to fractured-vuggy reservoir effectiveness evolution and heterogeneity.Meteoric water activity during the Late Caledonian to Early Hercynian period was the primary phase of fractured-vuggy reservoir formation.Hydrothermal activity in the Late Hercynian period further intensified the heterogeneity of effective reservoir space distribution.The study also reveals that fractured-vuggy reservoir connectivity is influenced by strike-slip fault structural position and present in-situ stress field.The reservoir connectivity of extensional overlaps is larger than that of pure strike-slip segments,while contractional overlaps show worse reservoir connectivity.Additionally,fractured-vuggy reservoirs controlled by strike-slip faults that are nearly parallel to the present in-situ stress direction exhibit excellent connectivity.Overall,high-quality reservoirs are distributed at the fault intersection of extensional overlaps,the central zones of contractional overlaps,pinnate fault zones at intersection,bend,and tip segments of pure strike-slip segments.Vertically,they are concentrated in mechanical stratigraphy with high brittleness indices.
文摘This paper prepared a novel as-cast W-Zr-Ti metallic ESM using high-frequency vacuum induction melting technique.The above ESM performs a typical elastic-brittle material feature and strain rate strengthening behavior.The specimens exhibit violent chemical reaction during the fracture process under the impact loading,and the size distribution of their residual debris follows Rosin-Rammler model.The dynamic fracture toughness is obtained by the fitting of debris length scale,approximately 1.87 MPa·m~(1/2).Microstructure observation on residual debris indicates that the failure process is determined by primary crack propagation under quasi-static compression,while it is affected by multiple cracks propagation in both particle and matrix in the case of dynamic impact.Impact test demonstrates that the novel energetic fragment performs brilliant penetration and combustion effect behind the front target,leading to the effective ignition of fuel tank.For the brittleness of as-cast W-ZrTi ESM,further study conducted bond-based peridynamic(BB-PD)C++computational code to simulate its fracture behavior during penetration.The BB-PD method successfully captured the fracture process and debris cloud formation of the energetic fragment.This paper explores a novel as-cast metallic ESM,and provides an available numerical avenue to the simulation of brittle energetic fragment.
基金supported by the Zhejiang Provincial Natural Science Foundation of China(Grant No.LY23E040001)Fundamental Research Funding Project of Zhejiang Province,China(Project Category A,Grant No.2022YW06)National Key R&D Program of China(Grant No.2023YFF0614902).
文摘Accurate prediction of coal reservoir permeability is crucial for engineering applications,including coal mining,coalbed methane(CBM)extraction,and carbon storage in deep unmineable coal seams.Owing to the inherent heterogeneity and complex internal structure of coal,a well-established method for predicting permeability based on microscopic fracture structures remains elusive.This paper presents a novel integrated approach that leverages the intrinsic relationship between microscopic fracture structure and permeability to construct a predictive model for coal permeability.The proposed framework encompasses data generation through the integration of three-dimensional(3D)digital core analysis and numerical simulations,followed by data-driven modeling via machine learning(ML)techniques.Key data-driven strategies,including feature selection and hyperparameter tuning,are employed to improve model performance.We propose and evaluate twelve data-driven models,including multilayer perceptron(MLP),random forest(RF),and hybrid methods.The results demonstrate that the ML model based on the RF algorithm achieves the highest accuracy and best generalization capability in predicting permeability.This method enables rapid estimation of coal permeability by inputting two-dimensional(2D)computed tomography images or parameters of the microscopic fracture structure,thereby providing an accurate and efficient means of permeability prediction.
基金Project(2014CB239205)supported by the National Basic Research Program of ChinaProject(20011ZX05030-005-003)supported by the National Science and Technology Major Project of China
文摘Faults and fractures of multiple scales are frequently induced and generated in compressional structural system. Comprehensive identification of these potential faults and fractures that cannot be distinguished directly from seismic profile of the complex structures is still an unanswered problem. Based on the compressional structural geometry and kinematics theories as well as the structural interpretation from seismic data, a set of techniques is established for the identification of potential faults and fractures in compressional structures. Firstly, three-dimensional(3D) patterns and characteristics of the faults directly interpreted from seismic profile were illustrated by 3D structural model. Then, the unfolding index maps, the principal structural curvature maps, and tectonic stress field maps were obtained from structural restoration. Moreover, potential faults and fractures in compressional structures were quantitatively identified relying on comprehensive analysis of these three maps. Successful identification of the potential faults and fractures in Mishrif limestone formation and in Asmari dolomite formation of Buzurgan anticline in Iraq demonstrates the applicability and reliability of these techniques.
基金sponsored by the National Science&Technology Major Special Project(Grant No.2011ZX05025-001-04)
文摘Eigenstructure-based coherence attributes are efficient and mature techniques for large-scale fracture detection. However, in horizontally bedded and continuous strata, buried fractures in high grayscale value zones are difficult to detect. Furthermore, middleand small-scale fractures in fractured zones where migration image energies are usually not concentrated perfectly are also hard to detect because of the fuzzy, clouded shadows owing to low grayscale values. A new fracture enhancement method combined with histogram equalization is proposed to solve these problems. With this method, the contrast between discontinuities and background in coherence images is increased, linear structures are highlighted by stepwise adjustment of the threshold of the coherence image, and fractures are detected at different scales. Application of the method shows that it can also improve fracture cognition and accuracy.
基金Projects(50874045,51301194)supported by the National Natural Science Foundation of ChinaProject(2144057)supported by the Natural Science Foundation of Beijing Municipality,China
文摘Effect of network structure on plasticity and fracture mode of Zr？Al？Ni？Cu bulk metallic glasses （BMGs） was investigated. The microstructures of transversal and longitudinal sections were exposed by chemical etching and observed by scanning electron microscopy （SEM）. The mechanical properties were examined by room-temperature uniaxial compression test. The results show that both plasticity and fracture mode are significantly affected by the network structure and the alteration occurs when the size of the network structure reaches up to a critical value. When the cell size （dc） of the network structure is ~3μm, Zr-based BMGs characterize in plasticity that decreases with increasingdc. The fracture mode gradually transforms from single 45° shear fracture to double 45° shear fracture and then cleavage fracture with increasingdc. In addition, the mechanisms of the transition of the plasticity and the fracture mode for these Zr-based BMGs are also discussed.
基金supported by the Key Research and Development Program of the Xinjiang Uygur Autonomous Region(No.2020B03006-1)the National Natural Science Foundation of China(Nos.42304069,and 42102275).
文摘The Urumqi foreland thrust tectonic belt exhibits complex geological structures and strong seismicity.Imaging its shallow crustal structure is of great significance for understanding its tectonic mechanism and seismogenic environment.We obtained a high-resolution S-wave velocity model of the shallow crust at depths of 0–8 km using ambient noise tomography applied to data from a dense seismic array.Sediments are generally thinner in the southeast and thicker in the northwest,with a maximum thickness of more than 8 km.Variations in the velocity structure near the Xishan,Wanyaogou,and Yamalike faults indicate that their formation was related to differences in the physical properties on either side of the fault.In addition,the faults exhibit thrusting of the low-velocity sides towards the high-velocity sides.In the study area,earthquakes rarely occur at depths of less than 3 km and are mostly concentrated in the high-velocity zone in the southern part.Below 3 km depth,more earthquakes were observed,mainly distributed near faults or in relatively high-velocity areas in the southern part.This suggests that high-velocity structures are more prone to stress accumulation,resulting in earthquakes.At 6–8 km depth,the densely distributed earthquakes in the northwestern part of the Bogda mountains are well-aligned with the northwest-oriented low-velocity zone observed in this study,suggesting that this weak zone likely controls seismicity in this area.
基金supported by the Natural Science Foundation of China-Youth Foundation(42402163)Natural Science Foundation of Sichuan Province of China(2024NSFSC0814)Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(2020CX010101).
文摘The strike-slip fault system in the central Tarim Craton controls a complex petroleum system with estimated reserves exceeding 1×10^(9)t,the fault-related fractures are important for hydrocarbon accumulation.In this paper,the basic parameters such as density and width of fractures are counted and classified,and the effects of fractures on reservoirs are analyzed.The results show that:(1)Structural fractures and stylolite were widely developed in Halahatang area and experienced at least three stages of activity based on the infilling materials and crosscutting relationship.(2)Fracture density,width,aperture,and dip angle vary in different wells,but the relationship between the above parameters and the distance to the fault core indicates the fracture differences in the fault damage zone and further provides a method to divide the inner units in the fault damage zone.In addition,oil and gas wells with high production mainly concentrate in the inner unit.(3)The infilling materials and degree of fractures vary.Fractures formed in the early stage are more filled and less open,while the fractures formed in the late stage are relatively less filled and more open.(4)Fractures improve porosity to a certain extent but greatly increase permeability,especially in the inner zone of fault damage zone with large quantity,multiple inclinations,less filling and large width.These features contribute to the formation of a higher-quality reservoir,further improving oil and gas production.This paper provides a quantitative characterization method for the study of strike-slip fault-related fracture-caved reservoirs,and points out that fault damage zone,especially the inner zone of the fault damage zone,is the potential goal for oil and gas exploration.
基金supported by the National Natural Science Foundation of China(No.U21B2062)funding from the Chinese Scholarship Council(CSC)and the American Association of Petroleum Geologists Foundation Grantsin-Aid Program.
文摘Natural fractures controlled by faults in ultradeep carbonate strata play substantial roles as both fluid migration channels and storage spaces.However,characterizing the heterogeneous distribution of underground fractures within the complex three-dimensional geometry of strike-slip fault zones remains challenging.This study investigates the characteristics of natural fractures controlled by strike-slip faults in the fractured Middle and Lower Ordovician reservoirs of the central and northern Tarim Basin,China.Seismics,cores,and image logs were integrated to quantitatively analyze the intensity and dip angle of natural fractures and findings were verified using published sandbox simulations.The carbonate reservoir contains three main types of natural fractures:tectonic fractures,abnormal high-pressure-related fractures,and stylolites.Strike-slip faults control the distribution and characteristics of tectonic fractures across various scales.Generally,both fracture intensity and porosity exhibit a decreasing trend as the distance from the main fault surface increases.Compared with those in non-stepover zones along a strike-slip fault,natural fractures and faults in stepover zones are more developed along the fault strike,with significantly greater development intensity in central stepover regions than that at its two ends.Furthermore,strike-slip faults influence the dip angles of both natural fractures and secondary faults.The proportion of medium-to-low-dip angle fractures and faults in the stepover zone is greater than that in the non-stepover zone.Additionally,the proportion of medium-to low-dip angle fractures and faults in the middle of the stepover is greater than that at both ends.Therefore,strike-slip fault structures control the dip angle of natural fracture and the heterogeneity of secondary fault and fracture intensity.The linking damage zone in the stepover contains a larger volume of fractured rocks,making it a promising petroleum exploration target.The development of stepovers and the orientation of present-day in-situ stress substantially influence the productivity of fractured reservoirs controlled by strike-slip faults.The analysis in this study reveals that reservoir productivity increases as the angle between the strike-slip fault segment and the maximum horizontal principal stress decreases.This study provides valuable insights for quantitatively evaluating fracture heterogeneity in fractured reservoirs and establishing optimized selection criteria for favorable targets in fault-related fractured reservoirs.
基金supported financially by the Project from the Strategic New Industry Development Special Foundation of Shenzhen (No.JCYJ20170306141749970)National Natural Science Foundation of China Projects under Grant [Nos.51871211 and 51701129]+2 种基金the funds of International Joint Laboratory for Light Alloys,the National Key Research and Development Program of China under Grant [No.2017YFB0702001]Liaoning BaiQianWan Talents Programthe Innovation Fund of Institute of Metal Research (IMR),Chinese Academy of Sciences (CAS)
文摘Through investigating and comparing the mechanical behavior of an as-rolled Mg-3%Al-1%Zn(wt%)alloy before and after annealing treatments,it was revealed that the formation of annealing-tailored bimodal grain structure ensured the 330℃/4 h samples having a good combination of tensile strength and plasticity.Failure analysis demonstrated that for the as-rolled and 330℃/1 h samples with fine grain structure,their plastic deformation was mainly attributed to basal slips,whereas the deformation mechanism in the bimodal grain-structured samples was dominated by basal slips in fine grains and twinning in coarse grains.For the 330℃/8 h samples with coarse grain structure,high densities of twins were activated.Meanwhile,basal slips occurred in the twinned and un-twinned areas of coarse grains and could pass through twin boundaries.For differently treated samples,cracking preferentially occurred along slip bands,resulting in their transgranular fractures.
基金funded by the National Basic Research Progam of China(Nos. 2007CB411306 and 2001CB409810)China Geological Survey(No.1212010611806)the National Natural Science Foundation of China(No.40702032)
文摘Secondary/minor structures occurring along the main fault surfaces are important indicators for judging the kinematic characteristics of faults.However,many factors can lead to the formation of these structures,which results in the difficulty for rapid judgment and application in the fields.A series of secondary faults/fractures developed due to the movement of main faults are the most important and widespread phenomena in the scope of brittle deformation.The morphology of the main fault surfaces is various,and former researchers mainly discussed the structures on the main even fault surfaces. However,the fluctuation of fault surfaces is the intrinsic character of the faults,and the intersection between the main fault and secondary faults/fractures can produce a series of kinematic indicators on the main fault surfaces.Based on previous studies and our observations,i.e.the structural traces of the P,R,R',T and X shears/faults along the main faults,some indicators which are rarely reported previously,are described in the paper.Furthermore,their reliabilities are also discussed,and more practical and reliable criteria are brought forward.We suggest that the simple application of congruous and incongruous steps without knowing their exact origins should be abandoned in the fields,and several types of indicators along one fault surface should be checked with each other as much as possible.Meanwhile,the origins of some other arcuate indicators on the fault surfaces are also discussed,and new models are brought forward.
基金funded by the National Key Research and Development Project of China(Grant No.2021YFC3000600)the China Earthquake Science Experiment Field-Cross-fault Observation Array-Red River Fault Scientific Drilling Project Geophysical Prospecting Site Selection Project+2 种基金Anhui Province Science and Technology Breakthrough Plan Project(Key Project,202423l10050030)the Earthquake Science and Technology Spark Program of the China Earthquake Administration(XH23020YA)the Anhui Mengcheng National Geophysical Observatory Joint Open Fund(MENGO-202307)。
文摘The complex Red River fault zone(RRFZ),which is situated in the southwestern region of China and separates the Indochina plate and South China blocks,has diverse seismic activities in different segments.To reveal the detailed geometric characteristics of the RRFZ at different sections and to better understand the seismogenic environment,in 2022 and 2023 we deployed 7 seismic dense linear arrays,consisting of 574 nodal stations,across the RRFZ in the northern and southern segments near the towns Midu,Gasa,Zhega,Dazhai,Xinzhai,and Taoyuan.The linear arrays,which extend from 2.4 to 12.5 km in length with station intervals ranging between 40 and140 m,recorded seismic ambient noise for approximately one month.Using the extended range phase shift method,we extract the phase velocity dispersion curves of the Rayleigh waves between 0.9 and 10 Hz,which are then used to invert for the high resolution shearwave velocity structures across the RRFZ beneath the linear arrays.The key findings are:(1)the 7 imaged sections of the RRFZ exhibit quite similar structures,with higher velocities on the SW side and lower velocities on the NE side;the velocity variation is consistent with the surface geological structures along the RRFZ;(2)the shear-wave velocities on the SW side of the RRFZ at the northern Midu section and southern Gasa-Dazhai sections are generally higher than their counterparts in the southern Xinzhai-Taoyuan sections,which reflects lithological variations from the marble-dominated Paleoproterozoic Along basement to the gneiss dominated Paleoproterozoic Qingshuihe basement;(3)from the northern Midu section to the southern region where the RRFZ intersects with the Xiaojiang Fault,the major faults of the RRFZ exhibit a consistent high-angle,NE-dipping structure;(4)the low shear-wave velocities immediately to the NE of the velocity boundary may indicate a faulted zone due to long-term shearing,where excessive amplifications of ground motions could occur.This study provides new insights into the characteristics of the shallow structures of the RRFZ.
基金financially supported by the Innovation Fund Research Project of State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK202201)。
文摘To address the issue of extensive deformation in the Tabaiyi Tunnel caused by the fault zone,nuclear magnetic resonance(NMR)technology was employed to analyze the physical and mechanical properties of waterabsorbing mudstone.This analysis aimed to understand the mechanism behind the significant deformations.Drawing from the principle of excavation stress compensation,a support scheme featuring NPR anchorcables and an asymmetric truss support system was devised.To validate the scheme,numerical analysis using a combination of the Discrete Element Method(DEM)-Finite Element Method(FEM)was conducted.Additionally,similar material model tests and engineering measurements were carried out.Field experiments were also performed to evaluate the NPR anchor-cable and truss support system,focusing on anchor cable forces,pressures between the truss and surrounding rock,pressures between the initial support and secondary lining,as well as the magnitude of settlement and convergence deformation in the surrounding rock.The results indicate that the waterinduced expansion of clay minerals,resulting from damage caused by fissure water,accelerated the softening of the mudstone's internal structure,leading to significant deformations in the Tabaiyi Tunnel under high tectonic stress.The original support design fell short as the length of the anchor rods was smaller than the expansion depth of the plastic zone.As a result,the initial support structure bore the entire load from the surrounding rock,and a non-coupled deformation contact was observed between the double-arch truss and the surrounding rock.The adoption of NPR asymmetric anchor-cable support effectively restrained the expansion and asymmetric distribution characteristics of the plastic zone.Considering the mechanical degradation caused by water absorption in mudstone,the rigid constraint provided by the truss proved crucial for controlling the stability of the surrounding rock.These research findings hold significant implications for managing large deformations in soft rock tunnels situated within fractured zones under high tectonic stress conditions.
基金Supported by National Natural Science Foundation of China(Grant Nos.52405001,52175001,62373010,82472537)China Postdoctoral Science Foundation(Grant No.2024M760166)+2 种基金Postdoctoral Fellowship Program of CPSF(Grant No.GZC20230186)Shenzhen Municipal Science,Technology,and Innovation Commission(Grant No.SGDX20220530111005036)Beijing Natural Science Foundation(Grant Nos.3222002,3232004,L222061).
文摘Long-bone fractures are common complaints in orthopedic surgery.In recent years,significant progress has been made in robot-assisted fracture-reduction techniques.As a key medical device for diverse fracture morphologies and sites,the design of the reduction robot has a profound impact on the reduction outcomes.However,existing reduction robots have practical limitations and cannot simultaneously satisfy clinical requirements in terms of workspace,force/torque,and structural stiffness.To overcome these problems,we first analyze the potential placement areas and performance requirements of reduction robots according to clinical application scenarios.Subsequently,a 3UPS/S-3P hybrid configuration with decoupled rotational and translational degrees of freedom(DOFs)is proposed,and a kinematic model is derived to achieve the motion characteristics of the remote center of motion(RCM).Furthermore,the structural design of a hybrid reduction robot with an integrated distal clamp and proximal fixator was completed,and a mechanical prototype was constructed.The results of the performance evaluations and static analysis demonstrate that the proposed reduction robot has acceptable workspace,force,and torque performance and excellent structural stiffness.Two clinical case simulations further demonstrated the clinical feasibility of the robot.Finally,preliminary experiments on bone models demonstrated the potential effectiveness of the proposed reduction robot in lower-limb fracture reduction.
基金supported by research grants from the National Institute of Natural Hazards, MEMC (ZDJ2020-13)the Innovation Team Project from National Institute of Natural Hazards, MEMC (2023-JBKY-59)the National Natural Science Foundation of China (42174093)。
文摘No earthquake of magnitude six or greater has been recorded historically in the southern segment of the Red River Fault(RRF).This absence constitutes a significant seismic gap, suggesting a risk of future strong earthquakes. The China Earthquake Science Experimental Site intends to conduct drilling exploration in this area, which necessitates improved knowledge of the fault zone's geometric distribution characteristics and deep structure. We obtained and analyzed audio and broadband magnetotelluric(MT) data collected at one of the alternative drilling stations(in the Dazhai Village of Honghe County). We have used these data to obtain a highresolution 3-D electrical model of this study area's subsurface to a depth of 5 km. We report that the electrical structure from the surface to 0.5 km is relatively complex, characterized by alternating high and low resistivity;below 0.5 km, the electrical structure becomes more simplified. The RRF extends northwest-southeast orientation along the high and low resistivity boundary, dipping northeastward. The electrical structure of the Red River Valley, which the fault zone traverses, reveals low resistivity characteristics with a lateral width of up to2 km. This study offers critical electromagnetic constraints that enhance our understanding of the tectonic characteristics of the RRF. The findings will inform and aid in the design of drilling plans for the southern segment of the RRF region.
基金Project was supported by the National Nature Science Foundation of China(51575408).
文摘Based on the evolution of fatigue cracks in welded structures,the fatigue life of welded structures was defined as the sum of the crack initiation life Ni and the crack propagation life Np.Correspondingly,a fatigue-life analysis method combining S-N curves and fracture mechanics theory was proposed.The equivalent structural stress method and the lower 99%boundary of the master S-N curve were used to evaluate Ni,and cracks at the end of the initiation stage were considered as semi-elliptical surface cracks.Moreover,Paris equation and the stress intensity factor range of the cracks were used to evaluate Np.Furthermore,the fatigue test results obtained from the running girder of cranes were used as a reference for comparison and verification of the results.The results revealed that the equivalent structural stress is a good indicator for the crack initiation behavior of complex welded structures.In addition,the predicted fatigue life corresponded closely to the testing life.
基金the National Science Foundation for Excellent Young Investigators(10325208)the National Natural Science Foundation of China(10432030)the China Postdoctoral Science Foundation(2004036018)
文摘The transient fracture behavior of a functionally graded layered structure subjected to an in-plane impact load is investigated. The studied structure is composed of two homogeneous layers and a functionally gradedinterlayer with a crack perpendicular to the boundaries. The impact load is applied on the face of the crack. Fourier transform and Laplace transform methods are used to formulate the present problem in terms of a singular integral equation in Laplace transform domain. Considering variations of parameters such as the nonhomogeneity constant, the thickness ratio and the crack length, the dynamic stress intensity factors （DSIFs） in time domain are studied and some meaningful conclusions are obtained.
基金Projects(11672195,51301092) supported by the National Natural Science Foundation of ChinaProject(2016JQ0047) supported by Sichuan Youth Science and Technology Foundation,China
文摘Heterogeneous-structured Cu samples composed of coarse-grained(CG) and ultrafine-grained(UFG) domains with a transitional interface were fabricated by friction stir processing, in order to investigate the effect of interface constraint on the yielding and fracture behaviors. Tensile test revealed that the synergetic strengthening induced by elastic/plastic interaction between incompatible domains increases with increasing the area of constraint interface. The strain distribution near interface and the fracture morphology were characterized using digital image correlation technique and scanning electron microscopy, respectively. Fracture dimples preferentially formed at the interface, possibly due to extremely high triaxial stress and strain accumulation near the interface. Surprisingly, the CG domain was fractured by pure shear instead of the expected voids growth caused by tensile stress.
基金financial support from the National Key R&D Program of China(Grant No.2017YFA0204403)financial support by the National Natural Science Foundation of China(Grant No.51931010,51601196 and U1608257)+2 种基金the Liaoning Revitalization Talents Program(Grant No.XLYC1802026)the Key Research Program of Frontier Science,Chinese Academy of Sciencesthe financial support of the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX180408).
文摘We produced a 316 L stainless steel with heterogeneous nanometer-thick lamellar structures by severe cold-rolling at room temperature,and conducted micro-scale tensile tests in different orientations to evaluate both the inplane(parallel to the nano-lamellae)and out-of-plane(normal and 45inclined to the nano-lamellae)mechanical anisotropy.The parallel orientation demonstrates the greatest tensile strength while the inclined orientation exhibits the least strength.The tensile tests in normal and inclined directions also indicate significant transient elastic-plastic response due to the strain path change.Fractographic examination demonstrates that the specimen fails in the normal direction by premature micro-void nucleation and growth,which restricts its tensile strength;however,we identified zig-zag cracking associated with lamellar shear cracking in the inclined direction.
