The reliability of the coated industry components demands ideal fatigue properties of the coating,and it is mainly determined by the performance of the interfaces.In this study,pulsed magnetic treatment(PMT)was applie...The reliability of the coated industry components demands ideal fatigue properties of the coating,and it is mainly determined by the performance of the interfaces.In this study,pulsed magnetic treatment(PMT)was applied to the thermal sprayed WC-10Co4Cr coating,and the fatigue lifetime of the coated bolt increased by 219.82%under an imitation of the operating mode condition.Scratch tests further proved that both the adhesion and cohesion strength were improved after PMT,and they benefit from the interface strengthening effects.The formation of coherent WC/Co interfaces was characterized by in-situ transmission electron microscopy(TEM),and the molecular dynamic simulations indicate that the work of separation of these interfaces is much higher than the original disordered ones.Residual stress was relaxed and distributed more homogeneously after PMT,and it mainly contributes to the coating/substrate strengthening.This work provides a new post-treatment method focusing on the interfaces in the WC-based coating and gives insight into its mechanism so that it is hopeful to be applied to other kinds of coatings.展开更多
Determining reasonable fracturing stage spacing is the key to horizontal well fracturing.Different from traditional stage spacing optimization methods based on the principle of maximum stimulated reservoir volume,in t...Determining reasonable fracturing stage spacing is the key to horizontal well fracturing.Different from traditional stage spacing optimization methods based on the principle of maximum stimulated reservoir volume,in this paper,by considering the integrity of the wellbore interface,a fracture propagation model was established based on displacement discontinuity method and the competition mechanism of multifracture joint expansion,leading to the proposal of an unequal stage spacing optimization model.The results show that in the first stage,the interfacial fractures spread symmetrically along the axis of the central point during that stage,while in the second and subsequent stages,the interfacial fractures of each cluster extend asymmetrically along the left and right sides.There are two kinds of interface connectivity behaviour:in one,the existing fractures first extend and connect within the stage,and in the other,the fractures first extend in the direction close to the previous stage,with the specific behaviour depending on the combined effect of stress shadow and flow competition during hydraulic fracture expansion.The stage spacing is positively correlated with the number of fractures and Young’s modulus of the cement and formation and is negatively correlated with the cluster spacing and horizontal principal stress difference.The sensitivity is the strongest when the Young’s modulus of the cement sheath is 10-20 GPa,and the sensitivity of the horizontal principal stress difference is the weakest.展开更多
A new ultra-fine tungsten carbide(WC)cemented carbide was fabricated by spark plasma sintering(SPS),in which the CoCrNiCuFe high entropy alloy(HEA)was used as the binder and was mixed with WC carbide through the mecha...A new ultra-fine tungsten carbide(WC)cemented carbide was fabricated by spark plasma sintering(SPS),in which the CoCrNiCuFe high entropy alloy(HEA)was used as the binder and was mixed with WC carbide through the mechanical ball milling method.The microstructure of WC-10 wt%HEA compos-ites was investigated through scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD),and differential scanning calorimetry-thermogravimetric analysis(DSC-TG).The results show that the interface characteristics of the WC/HEA system include the FCC(111)//HCP(101^(-)1)interface with stable ionic bonds and the interface that reacts due to the formation of the(Fe,Co)_(3)W_(3)C phase.The mechanical properties of WC-10 wt%HEA composites were investigated through the Vickers hardness test,friction and wear tests,and compression test.The WC-10 wt%HEA composites exhibit good fracture toughness and hardness of 10.98 MPa m^(1/2)and 1988.60 HV30,respec-tively.The compressive strength at room temperature and 800℃is up to 3307 and 1747 MPa,respec-tively.The composites exhibited excellent properties attributed to the good wettability of HEA on WC grains and the consequent strengthening effect on the WC/WC interfaces.展开更多
Cement bond model wells （1：10 scaled-down） were made with a gradually degrading cement annulus for cement bond evaluation of the first interface （between the casing and the cement annulus） and the second interfa...Cement bond model wells （1：10 scaled-down） were made with a gradually degrading cement annulus for cement bond evaluation of the first interface （between the casing and the cement annulus） and the second interface （between the cement annulus and the formation）. Experimental simulation on cement bond logging was carried out with these model wells. The correlation of acoustic waveforms, casing wave energy and flee casing area before and after cement bonding of the second interface was established. The experimental results showed that the arrival of the casing waves had no relationship with the cement bonding of the second interface, but the amplitude of the casing head wave decreased obviously after the second interface was bonded. So, cement bonding of the second interface had little effect on the evaluation of the cement bond quality of the first interface by using casing head wave arrivals. Strong cement annulus waves with early arrivals were observed before the second interface was bonded, while obvious ＂formation waves＂ instead of cement annulus waves were observed after the second interface was bonded.展开更多
The texture of interfacial zone between cement paste and quartz in the cement-based composites containing polyvinyl alcohol (PVA), methylcellulose (MC) and their potyblend in an amount of 10 wt % with respect to cemen...The texture of interfacial zone between cement paste and quartz in the cement-based composites containing polyvinyl alcohol (PVA), methylcellulose (MC) and their potyblend in an amount of 10 wt % with respect to cement, as well as the texture of dehydrated bodies of PVA, MC, and the potyblend solutions, were investigated with SEM. The network texture of the dehydrated polyblend is confirmed by comparing the texture of dehydrated bodies of PVA and MC. The network texture has restrained the movement of polyblend molecules in the cement mortar but is helpful to forming a coherent interface between cement paste and quartz. The key factor of forming the coherent interface is not the neutralization reaction between H + from hydrolysis of quarts: and OH- from hydration of cement, but the electrostatic attraction and the chemical reaction between polar groups on the polyblend molecule and cations and onions from hydrolysis of quartz and hydration of cement, respectively. The model of the coherent interface formation is that excessive [HSiO3]- and [SiO3]2- onions are bonded with the hydrated cations such as Ca2+ and Al3+ , which is confirmed by the gel containing Ca and Si on the quartz surface.展开更多
The surface of carbon fibre is studied which has been treated with heated sodium hydrate solution (NaOH) . It is found that the surface of carbon fibre is not corroded during the treatment. But at the same time, it is...The surface of carbon fibre is studied which has been treated with heated sodium hydrate solution (NaOH) . It is found that the surface of carbon fibre is not corroded during the treatment. But at the same time, it is also found that after this treatment, a certain number of carbonyl groups (C O) and (-COOH or ?COONa) are produced on the treated surface of carbon fibre. When carbon fiber is mixed with cement paste, the above reactive groups will link with Ca+2 in the paste, which will result in an early stage hydration of cement in inter facial areas. In addition, the experiments show that the rheological properties of cement paste reinforced with alkali-treated carbon fibre differ greatly from that of untreated carbon fibre reinforced cement paste.展开更多
This paper presents quantitatively the results of an experimental investigation on influence of mineral admixtures and superplasticizers on Vickers micro hardness(HV) of aggregate-paste interface in cement concrete. T...This paper presents quantitatively the results of an experimental investigation on influence of mineral admixtures and superplasticizers on Vickers micro hardness(HV) of aggregate-paste interface in cement concrete. The HV was measured by Vickers hardness testing equipment.The results indicate that addition of fly ash decreases HV of the concrete.Although it decreases with the increase of ground granulated blast furnace slag (GGBS) replacement,the HV is higher than that of concrete containing fly ash at all replacements.The flying ash and GGBS composition increases HV in later curing ages,but does not improve it in early curing ages.Aminosulfonic acid based superplasticizer and aliphatic hydroxy sulphonate condensate superplasticizer can enhance HV in early curing ages.The HV of concrete with polycarboxylic acid superplasticizer is higher in later curing ages.展开更多
The mud film thickness on the outer surface of casing and its distribution laws are important factors affecting the cementation quality at casing-cement interfaces.So far,however,the distribution laws of mud film thic...The mud film thickness on the outer surface of casing and its distribution laws are important factors affecting the cementation quality at casing-cement interfaces.So far,however,the distribution laws of mud film thickness on the outer surface of casing at different inclinations and its effect on the interfacial cementing strength have never been reported in literatures.In this paper,the mud film thickness at different parts on the outer surface of simulated casing(steel pipe)was measured at the inclination of 0°,30°,60°and 86°,respectively,using the independently designed experimental device.Then,the distribution law of mud film thickness on the outer surface of casing and its effect on the interfacial cementing strength were summarized.And the following research results were obtained.First,when the inclination increases from 0°to 86°,the mud film thickness changes from uniform distribution to thin-and-thick distribution,and the area proportions of thinner and thicker mud films both increase.And especially at the inclination of 86°,the mud film thickness on the upper surface is very large,and there are large exposed areas on the left and right surfaces of the steel pipe.Second,the cementing strength at the casing-cement interface of the exposed casing is much higher than that at the interface with mud film.And with the increase of inclination,the interfacial cementing strength with mud film tends to increase.Third,with the increase of inclination,the interfacial cementing strength increases successively,which is closely related to the area proportion of the exposed steel pipe to the solid mud film on the outer surface.In conclusion,the exposed area of the simulated casing on the outer surface is a key factor affecting its interfacial cementing strength.展开更多
Application of cemented rockfilling to underground mining could not be separated from the corresponding backfill’s shear strength properties. The shear of cemented rockfill(CRF)-rock wall and the shear interaction oc...Application of cemented rockfilling to underground mining could not be separated from the corresponding backfill’s shear strength properties. The shear of cemented rockfill(CRF)-rock wall and the shear interaction occurring within CRFs both have some disadvantageous failure chances. In this study,we tried to investigate the complete shear properties of CRFs using direct shear and triaxial tests of cemented granite rockfill. Large-scale triaxial testing was held to accommodate the large CRF sample.Direct shear testing on the prepared flat and smooth surfaces was assessed with brief conversions and their corrections were used to approximate the shear strength envelopes of CRF joint interfaces. Two types of CRFs with the same aggregate size and distribution but different unconfined compressive strengths(UCSs) due to different mixture designs indicated insignificant differences between their basic friction angles, and also their asperity inclination angles. Nevertheless, investigation between direct shear test and triaxial test showed that the specimen with higher UCS tended to have a slightly lower friction angle but a higher cohesion than the other one.展开更多
Ultrasonic leaky Lamb waves are sensitive to defects and debonding in multilayer media. In this study, we use the finite-difference method to simulate the response of flexural waves in the presence of defects owing to...Ultrasonic leaky Lamb waves are sensitive to defects and debonding in multilayer media. In this study, we use the finite-difference method to simulate the response of flexural waves in the presence of defects owing to casing corrosion and rough fluctuations at the cement-formation interface. The ultrasonic obliquely incidence could effectively stimulate the flexural waves. The defects owing to casing corrosion change the amplitude of the early- arrival flexural wave, which gradually decrease with increasing defect thickness on the exterior walls and is the lowest when the defect length and wavelength were comparable. The scattering at the defects decreases the energy of flexural waves in the casing that leaks directly to fluids. For rough cement-formation interface, the early-arrival flexural waves do not change, whereas the late-arrival flexural waves have reduced amplitude owing to the scattering at rough interface.展开更多
A trial test method is introduced to form and magnify regular interface. Through researching on the carbonation of the magnifying interfacial transition zone （ITZ）, the practical carbonation of the concrete can be s...A trial test method is introduced to form and magnify regular interface. Through researching on the carbonation of the magnifying interfacial transition zone （ITZ）, the practical carbonation of the concrete can be simulated. Because the diffusion rate of CO2 in the ITZ is several times greater than that in the bulk paste, the diffusion rate and direction of CO2 will change and form a new carbonation front line. An interfacial effect zone caused by the ITZ will change the distribution of the complete carbonation zone and the partial carbonation zone. One of the important reasons for the formation of the partial carbonation zone was the existence of the interfacial effect zone. Consequently, the method mentioned in this paper provides a new way for researching on the microstructure of the cement based materials during the carbonation process.展开更多
基金This study was financially supported by National Key R&D Program of China(No.2020YFA0714900)National Natural Science Foundation of China(No.52031003)the Defense Industrial Technology Development Program(No.JCKY2020110B007).
文摘The reliability of the coated industry components demands ideal fatigue properties of the coating,and it is mainly determined by the performance of the interfaces.In this study,pulsed magnetic treatment(PMT)was applied to the thermal sprayed WC-10Co4Cr coating,and the fatigue lifetime of the coated bolt increased by 219.82%under an imitation of the operating mode condition.Scratch tests further proved that both the adhesion and cohesion strength were improved after PMT,and they benefit from the interface strengthening effects.The formation of coherent WC/Co interfaces was characterized by in-situ transmission electron microscopy(TEM),and the molecular dynamic simulations indicate that the work of separation of these interfaces is much higher than the original disordered ones.Residual stress was relaxed and distributed more homogeneously after PMT,and it mainly contributes to the coating/substrate strengthening.This work provides a new post-treatment method focusing on the interfaces in the WC-based coating and gives insight into its mechanism so that it is hopeful to be applied to other kinds of coatings.
基金This work was supported by the Natural Science Foundation of Heilongjiang Province of China(YQ2021E005)the National Natural Science Foundation of China(No.51774094)+2 种基金the Youth Fund Project of National Natural Science Foundation of China(52004065)the Heilongjiang Natural Science Foundation Project(excellent youth project)(YQ2021E006)"Reveal the top"Science and Technology Project of Heilongjiang Province(2021ZZ10-04).
文摘Determining reasonable fracturing stage spacing is the key to horizontal well fracturing.Different from traditional stage spacing optimization methods based on the principle of maximum stimulated reservoir volume,in this paper,by considering the integrity of the wellbore interface,a fracture propagation model was established based on displacement discontinuity method and the competition mechanism of multifracture joint expansion,leading to the proposal of an unequal stage spacing optimization model.The results show that in the first stage,the interfacial fractures spread symmetrically along the axis of the central point during that stage,while in the second and subsequent stages,the interfacial fractures of each cluster extend asymmetrically along the left and right sides.There are two kinds of interface connectivity behaviour:in one,the existing fractures first extend and connect within the stage,and in the other,the fractures first extend in the direction close to the previous stage,with the specific behaviour depending on the combined effect of stress shadow and flow competition during hydraulic fracture expansion.The stage spacing is positively correlated with the number of fractures and Young’s modulus of the cement and formation and is negatively correlated with the cluster spacing and horizontal principal stress difference.The sensitivity is the strongest when the Young’s modulus of the cement sheath is 10-20 GPa,and the sensitivity of the horizontal principal stress difference is the weakest.
基金supported by the Key Program of Scientific Research of Higher Education of Hebei Province(No.ZD2021099)Qinhuangdao Science and Technology Research and Development Plan Project(No.202302B005)+2 种基金National Natural Science Foundation of China(No.52104384)China Postdoctoral Science Foundation(No.2020M683675XB)NSF of Shaanxi Provincial Department of Education(No.21JK0761).
文摘A new ultra-fine tungsten carbide(WC)cemented carbide was fabricated by spark plasma sintering(SPS),in which the CoCrNiCuFe high entropy alloy(HEA)was used as the binder and was mixed with WC carbide through the mechanical ball milling method.The microstructure of WC-10 wt%HEA compos-ites was investigated through scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD),and differential scanning calorimetry-thermogravimetric analysis(DSC-TG).The results show that the interface characteristics of the WC/HEA system include the FCC(111)//HCP(101^(-)1)interface with stable ionic bonds and the interface that reacts due to the formation of the(Fe,Co)_(3)W_(3)C phase.The mechanical properties of WC-10 wt%HEA composites were investigated through the Vickers hardness test,friction and wear tests,and compression test.The WC-10 wt%HEA composites exhibit good fracture toughness and hardness of 10.98 MPa m^(1/2)and 1988.60 HV30,respec-tively.The compressive strength at room temperature and 800℃is up to 3307 and 1747 MPa,respec-tively.The composites exhibited excellent properties attributed to the good wettability of HEA on WC grains and the consequent strengthening effect on the WC/WC interfaces.
基金supported by the National Natural Science Foundation of China(Grant No.10534040 and No.40574049)key laboratory of well logging of China National Petroleum Corporation(CNPC).
文摘Cement bond model wells （1：10 scaled-down） were made with a gradually degrading cement annulus for cement bond evaluation of the first interface （between the casing and the cement annulus） and the second interface （between the cement annulus and the formation）. Experimental simulation on cement bond logging was carried out with these model wells. The correlation of acoustic waveforms, casing wave energy and flee casing area before and after cement bonding of the second interface was established. The experimental results showed that the arrival of the casing waves had no relationship with the cement bonding of the second interface, but the amplitude of the casing head wave decreased obviously after the second interface was bonded. So, cement bonding of the second interface had little effect on the evaluation of the cement bond quality of the first interface by using casing head wave arrivals. Strong cement annulus waves with early arrivals were observed before the second interface was bonded, while obvious ＂formation waves＂ instead of cement annulus waves were observed after the second interface was bonded.
基金Funded by Natural Science Foundation of China (No. 49802004)
文摘The texture of interfacial zone between cement paste and quartz in the cement-based composites containing polyvinyl alcohol (PVA), methylcellulose (MC) and their potyblend in an amount of 10 wt % with respect to cement, as well as the texture of dehydrated bodies of PVA, MC, and the potyblend solutions, were investigated with SEM. The network texture of the dehydrated polyblend is confirmed by comparing the texture of dehydrated bodies of PVA and MC. The network texture has restrained the movement of polyblend molecules in the cement mortar but is helpful to forming a coherent interface between cement paste and quartz. The key factor of forming the coherent interface is not the neutralization reaction between H + from hydrolysis of quarts: and OH- from hydration of cement, but the electrostatic attraction and the chemical reaction between polar groups on the polyblend molecule and cations and onions from hydrolysis of quartz and hydration of cement, respectively. The model of the coherent interface formation is that excessive [HSiO3]- and [SiO3]2- onions are bonded with the hydrated cations such as Ca2+ and Al3+ , which is confirmed by the gel containing Ca and Si on the quartz surface.
文摘The surface of carbon fibre is studied which has been treated with heated sodium hydrate solution (NaOH) . It is found that the surface of carbon fibre is not corroded during the treatment. But at the same time, it is also found that after this treatment, a certain number of carbonyl groups (C O) and (-COOH or ?COONa) are produced on the treated surface of carbon fibre. When carbon fiber is mixed with cement paste, the above reactive groups will link with Ca+2 in the paste, which will result in an early stage hydration of cement in inter facial areas. In addition, the experiments show that the rheological properties of cement paste reinforced with alkali-treated carbon fibre differ greatly from that of untreated carbon fibre reinforced cement paste.
基金the Special Foundation for Basic Scientific Research of Central Colleges of China (No:CHD2011ZD011)the Special Foundation of Basic Research for Chang'an University
文摘This paper presents quantitatively the results of an experimental investigation on influence of mineral admixtures and superplasticizers on Vickers micro hardness(HV) of aggregate-paste interface in cement concrete. The HV was measured by Vickers hardness testing equipment.The results indicate that addition of fly ash decreases HV of the concrete.Although it decreases with the increase of ground granulated blast furnace slag (GGBS) replacement,the HV is higher than that of concrete containing fly ash at all replacements.The flying ash and GGBS composition increases HV in later curing ages,but does not improve it in early curing ages.Aminosulfonic acid based superplasticizer and aliphatic hydroxy sulphonate condensate superplasticizer can enhance HV in early curing ages.The HV of concrete with polycarboxylic acid superplasticizer is higher in later curing ages.
基金Project supported by the Sub-project of National Major Science and Technology Project(No.:2017ZX05009003-003)the National Natural Science Foundation of China(No.:51774258,41572142).
文摘The mud film thickness on the outer surface of casing and its distribution laws are important factors affecting the cementation quality at casing-cement interfaces.So far,however,the distribution laws of mud film thickness on the outer surface of casing at different inclinations and its effect on the interfacial cementing strength have never been reported in literatures.In this paper,the mud film thickness at different parts on the outer surface of simulated casing(steel pipe)was measured at the inclination of 0°,30°,60°and 86°,respectively,using the independently designed experimental device.Then,the distribution law of mud film thickness on the outer surface of casing and its effect on the interfacial cementing strength were summarized.And the following research results were obtained.First,when the inclination increases from 0°to 86°,the mud film thickness changes from uniform distribution to thin-and-thick distribution,and the area proportions of thinner and thicker mud films both increase.And especially at the inclination of 86°,the mud film thickness on the upper surface is very large,and there are large exposed areas on the left and right surfaces of the steel pipe.Second,the cementing strength at the casing-cement interface of the exposed casing is much higher than that at the interface with mud film.And with the increase of inclination,the interfacial cementing strength with mud film tends to increase.Third,with the increase of inclination,the interfacial cementing strength increases successively,which is closely related to the area proportion of the exposed steel pipe to the solid mud film on the outer surface.In conclusion,the exposed area of the simulated casing on the outer surface is a key factor affecting its interfacial cementing strength.
基金the University of Alberta Mining Department teams for their support and guidancethe Indonesia Endowment Fund for Education scholarship (Grant No. 20151112014754/LPDP/2015) for the authors’ financial assistance
文摘Application of cemented rockfilling to underground mining could not be separated from the corresponding backfill’s shear strength properties. The shear of cemented rockfill(CRF)-rock wall and the shear interaction occurring within CRFs both have some disadvantageous failure chances. In this study,we tried to investigate the complete shear properties of CRFs using direct shear and triaxial tests of cemented granite rockfill. Large-scale triaxial testing was held to accommodate the large CRF sample.Direct shear testing on the prepared flat and smooth surfaces was assessed with brief conversions and their corrections were used to approximate the shear strength envelopes of CRF joint interfaces. Two types of CRFs with the same aggregate size and distribution but different unconfined compressive strengths(UCSs) due to different mixture designs indicated insignificant differences between their basic friction angles, and also their asperity inclination angles. Nevertheless, investigation between direct shear test and triaxial test showed that the specimen with higher UCS tended to have a slightly lower friction angle but a higher cohesion than the other one.
基金supported by the Research and Development of Key Instruments and Technologies for Deep Resources Prospecting(No.ZDYZ2012-1-07)the National Natural Science Foundation of China(Nos.41204099,11134011,and 11274341)
文摘Ultrasonic leaky Lamb waves are sensitive to defects and debonding in multilayer media. In this study, we use the finite-difference method to simulate the response of flexural waves in the presence of defects owing to casing corrosion and rough fluctuations at the cement-formation interface. The ultrasonic obliquely incidence could effectively stimulate the flexural waves. The defects owing to casing corrosion change the amplitude of the early- arrival flexural wave, which gradually decrease with increasing defect thickness on the exterior walls and is the lowest when the defect length and wavelength were comparable. The scattering at the defects decreases the energy of flexural waves in the casing that leaks directly to fluids. For rough cement-formation interface, the early-arrival flexural waves do not change, whereas the late-arrival flexural waves have reduced amplitude owing to the scattering at rough interface.
基金Funded by the National Natural Science Foundation of China(No.51178103)
文摘A trial test method is introduced to form and magnify regular interface. Through researching on the carbonation of the magnifying interfacial transition zone （ITZ）, the practical carbonation of the concrete can be simulated. Because the diffusion rate of CO2 in the ITZ is several times greater than that in the bulk paste, the diffusion rate and direction of CO2 will change and form a new carbonation front line. An interfacial effect zone caused by the ITZ will change the distribution of the complete carbonation zone and the partial carbonation zone. One of the important reasons for the formation of the partial carbonation zone was the existence of the interfacial effect zone. Consequently, the method mentioned in this paper provides a new way for researching on the microstructure of the cement based materials during the carbonation process.
