Qingdao Jiaozhou Bay subsea tunnel is the second self-built tunnel in China with the designed service life over 100 years.The durability of lining concrete are one of an important factors to determinate the service li...Qingdao Jiaozhou Bay subsea tunnel is the second self-built tunnel in China with the designed service life over 100 years.The durability of lining concrete are one of an important factors to determinate the service life of tunnel.Considering the main environmental loads and mechanical loads of subsea tunnel,the durability properties of lining concrete under combined action of compressive load and carbonation has been studied through the critical compressive load test,accelerated carbonation test,natural carbonation test and capillary suction test.The tests results show that critical compressive load apparently accelerates the carbonation and deteriorates the anti-permeability of concrete.Under the combined action of critical compressive load and carbonation,the durability of lining concrete decreases.Based on the carbonization life criteria and research results,for the high-performance concrete with proposed mix ratio,the predicted service life of lining concrete for Jiaozhou bay subsea tunnel is about 80 years which fails to reach the required service life.It is necessary to adopt other measurements simultaneously to improve the durability of lining concrete.展开更多
In this study,through experimental research and an investigation on large datasets of the durability parameters in ocean engineering,the values,ranges,and types of distribution of the durability parameters employed fo...In this study,through experimental research and an investigation on large datasets of the durability parameters in ocean engineering,the values,ranges,and types of distribution of the durability parameters employed for the durability design in ocean engineering in northern China were confirmed.Based on a modified theoretical model of chloride diffusion and the reliability theory,the service lives of concrete structures exposed to the splash,tidal,and underwater zones were calculated.Mixed concrete proportions meeting the requirement of a service life of 100 or 120 years were designed,and a cover thickness requirement was proposed.In addition,the effects of the different time-varying relationships of the boundary condition(Cs)and diffusion coefficient(Df)on the service life were compared;the results showed that the time-varying relationships used in this study(i.e.,Cscontinuously increased and then remained stable,and Dfcontinuously decreased and then remained stable)were beneficial for the durability design of concrete structures in marine environment.展开更多
Effects of operation conditions such as ladle temperature, remining time of molten steel, slag basicity, slag oxidation, slag viscosity , vacuum treatment, ultra-high temperature, gas blowing and stirring, intermitten...Effects of operation conditions such as ladle temperature, remining time of molten steel, slag basicity, slag oxidation, slag viscosity , vacuum treatment, ultra-high temperature, gas blowing and stirring, intermittent operation, and different refining equipment on service life of ladle lining refractories were researched. The following conclusions are drawn : (1) molten steel temperature rising, remaiaing time prolonging, slag oxidation ability enhancing, slag viscosity and basicity decreasing can aecelerate the corrosion of ladle lining ; (2) ultra-high temperature and vacuum treatment of ladle not only acceler- ate the fusion corrasion of ladle lining, but also make the carbon containing refractories react forming gases leading to more corrosion, so carbon containing refractories are not stdtable.for the smelting conditions of long term vacuum treatment and ultra-high temperature, especially carbon containing refractories added with conventional additives such as A1 and Si powders ; ( 3 ) argon blowing does not accelerate the corrosion of ladle lining obvioasly, but oxygen blowing does; (4) the corrosion degree of refractories varies with the refining equipment, and the service life of ladle lining decreases according to a certain proportion with the refining ratio increasing.展开更多
The microstructures and mechanical properties of H13 mandrels made by Baosteel and foreign companies were investigated in this study. Based on the comparison research, the processes were optimized, such as steelmaking...The microstructures and mechanical properties of H13 mandrels made by Baosteel and foreign companies were investigated in this study. Based on the comparison research, the processes were optimized, such as steelmaking, heat treatment and multiple forging processes. The quality of Baosteel mandrels was greatly improved by increasing the homogenizing of an annealing temperature and refining processes. The results of the pilot trial showed that the average number of piercing steel tubes for Baosteel mandrels was over 3000 ,which reached the level of imported mandrels.展开更多
To solve the durability of island and reef concrete engineering in the harsh environment of high temperature,high salt,high humidity and windy,the strength grade of concrete and the type of corrosion inhibitor were us...To solve the durability of island and reef concrete engineering in the harsh environment of high temperature,high salt,high humidity and windy,the strength grade of concrete and the type of corrosion inhibitor were used as the influence factors,while the relative dynamic elastic modulus was used as the evaluation index.In addition,the law and time variability of the deterioration of concrete,the size effect,environmental similarity and the service life model were studied.The results showed that improving the strength grade of concrete could improve the durability of concrete,and corrosion inhibitor could slightly improve the durability of concrete.Time-varying law of the deterioration of concrete conformed to the univariate quadratic polynomial.Combined with the concrete damage equivalent theory,a size effect model based on the relative dynamic elastic modulus was proposed and verified,and the size effect coefficient was also given.An environmental similarity model between simulated and practical island and reef environment was proposed.Combined with the reliability theory and the first order second moment method,a new service life model of concrete structure was proposed.The authors were convinced that the research will be advantageous to researchers.展开更多
With the wide application of the magnesia-graphite refractory having a high-thermal-conductivity in BOF vessels for extending the furnace campaign, furnace shell deformation has become increasingly serious. It shorten...With the wide application of the magnesia-graphite refractory having a high-thermal-conductivity in BOF vessels for extending the furnace campaign, furnace shell deformation has become increasingly serious. It shortened the furnace campaign and reduced the production. The paper presents the work on increasing the life-span of the furnace shell at Baosteel, which includes the shell renovation, the study on the creep deformation resisting shell plates and the application of the air cooling method to the BOF shell. The results and limitations of these technologies are discussed.展开更多
A novel high-strength straight-hole recycled pervious concrete(HSRPC)for the secondary highway pavement was prepared in this paper.This study aimed to investigate the effect of porosity(0.126%,0.502%,and 1.13%),vehicl...A novel high-strength straight-hole recycled pervious concrete(HSRPC)for the secondary highway pavement was prepared in this paper.This study aimed to investigate the effect of porosity(0.126%,0.502%,and 1.13%),vehicle loading stress level(0.5 and 0.8)and service life on the resistance to rainstormbased waterlogging of HSRPC under fatigue loading.The mechanical properties of HSRPC in terms of flexural strength and dynamic elastic modulus were studied.The waterlogging resistance of HSRPC was described by surface water depth and drainage time.The microstructure of HSRPC were observed with scanning electron microscopy(SEM).Results showed that although the dynamic elastic modulus and flexural strength of HSRPC decreased with the increasing number of fatigue loading,the flexural strength of HSRPC was still greater than5 MPa after design service life of 20 years.After 2.5×10^(5)times of fatigue loading,the permeability coefficient of HSRPC with a porosity of 0.502%and 1.13%increased by 18.4%and 22.9%,respectively;while the permeability coefficient of HSRPC with 0.126%porosity dropped to 0.35 mm/s.The maximum surface water depth of HSRPC with a porosity of 0.126%,0.502%,and 1.13%were 8,5 and 4 mm,respectively.SEM results showed that fatigue loading expanded the number and width of cracks around the tiny pores in HSRPC.展开更多
In this paper the use of lime stabilized subgrade for low volume roads in two regions with high mountains and different frost penetration conditions in Türkiye was investigated in terms of design,performance,and ...In this paper the use of lime stabilized subgrade for low volume roads in two regions with high mountains and different frost penetration conditions in Türkiye was investigated in terms of design,performance,and cost.Pavements on unstabilized and stabilized subgrade were designed for two regions(Izmir and Van),covering all climate variations.The resilient modulus of the lime stabilized subgrade with different soil pulverization levels for non-freezing and freezing conditions were taken from a previous laboratory study.Frost effects were considered in pavement design using two different approaches,including limited subgrade frost penetration method and reduced subgrade strength method.Detailed application and evaluation were performed for all steps.Lime stabilized subgrades significantly reduced the thickness of base courses,and the benefit of lime stabilization was highly dependent on soil pulverization level.A detailed cost analysis on the unstabilized and stabilized cases found that the use of lime stabilization in the subgrade provided significant initial cost savings.Comparative analysis by using the AASHTO(1993)method and KENPAVE software,and quantity effect of soil pulverization level on the performance of low volume roads from a service life perspective,show that subgrade resilient modulus can be estimated.It is also possible to make correct performance estimation in the field.The results of the study show that lime stabilization is a good solution for low volume roads in the mountainous regions of Türkiye.展开更多
The single crystal blade is one of the key technologies for improving the performance, durability and reliability of aero-engines and ground gas-turbine engines. However, the anisotropic mechanical properties of the s...The single crystal blade is one of the key technologies for improving the performance, durability and reliability of aero-engines and ground gas-turbine engines. However, the anisotropic mechanical properties of the single crystal material makes a great deal of difficulties on the development and the application of the single crystal blade, which is a challenge for the engineering application of the single crystal superalloy and the theoretic bases of the application. Some researches on the strength analysis and the life prediction of the anisotropic single crystal blade were carried out by the authors' research team. They are as follows. The crystallographic constitutive models for the plastic and the creep behaviors and the method of the rupture life prediction were established and verified. The tensile or the creep experiments for DD3 single crystal alloy with different orientations under different temperatures and different tensile rates or under different temperatures and different stress levels were carried out. The experimental data and the anisotropic properties at intermediate and high temperatures revealed by the experiments are significant for the application of the single crystal alloy. In addition, the experimental research for a kind of single crystal blade was also made. As the application of the researches the strength analysis and the life prediction were carried out for the single crystal blade of a certain aero-engine. In this part, the constitutive models and their applications are described, and the experimental research work will be described in part II.展开更多
According to the chloride corrosion environment,service life prediction model of concrete structure of sea-crossing bridge was built using modified Fick's second law and the whole probability calculation method,wh...According to the chloride corrosion environment,service life prediction model of concrete structure of sea-crossing bridge was built using modified Fick's second law and the whole probability calculation method,which was suitable for China. Furthermore,a visual service life prediction program of concrete structure was developed by optimized Monte Carlo method. Meanwhile,Life 365 program was compared,indicating reliability of the prediction program. Finally,the validity of prediction model was verified in JinTang Bridge of Zhoushan Island Mainland Linkage Project.展开更多
Potassium-ion hybrid capacitors(PIHCs)tactfully combining capacitor-type cathode with battery-type anode have recently attracted increasing attentions due to their advantages of decent energy density,high power densit...Potassium-ion hybrid capacitors(PIHCs)tactfully combining capacitor-type cathode with battery-type anode have recently attracted increasing attentions due to their advantages of decent energy density,high power density,and low cost;the mismatches of capacity and kinetics between capacitor-type cathode and battery-type anode in PIHCs yet hinder their overall performance output.Herein,based on prediction of density functional theory calculations,we find Se/N co-doped porous carbon is a promising candidate for K+storage and thus develop a simple and universal self-sacrifice template method to fabricate Se and N co-doped three-dimensional(3D)macroporous carbon(Se/N-3DMpC),which features favorable properties of connective hier-archical pores,expanded interlayer structure,and rich activity site for boosting pseudocapacitive activity and kinetics toward K^(+)storage anode and enhancing capacitance performance for the reversible anion adsorption/desorption cath-ode.As expected,the as-assembled PIHCs full cell with a working voltage as high as 4.0 V delivers a high energy density of 186 Wh kg^(−1) and a power output of 8100 W kg^(−1) as well as excellent long service life.The proof-of-concept PIHCs with excellent performance open a new avenue for the development and application of high-performance hybrid capacitors.展开更多
Carbonation is one of the most aggressive phenomena affecting reinforced concrete structures and causing their degradation over time.Once reinforcement is altered by carbonation,the structure will no longer fulfill se...Carbonation is one of the most aggressive phenomena affecting reinforced concrete structures and causing their degradation over time.Once reinforcement is altered by carbonation,the structure will no longer fulfill service requirements.For this purpose,the present work estimates the lifetime of fly ash concrete by developing a carbonation depth prediction model that uses an artificial neural network technique.A collection of 300 data points was made from experimental results available in the published literature.Backpropagation training of a three-layer perceptron was selected for the calculation of weights and biases of the network to reach the desired performance.Six parameters affecting carbonation were used as input neurons:binder content,fly ash substitution rate,water/binder ratio,CO_(2)concentration,relative humidity,and concrete age.Moreover,experimental validation carried out for the developed model shows that the artificial neural network has strong potential as a feasible tool to accurately predict the carbonation depth of fly ash concrete.Finally,a mathematical formula is proposed that can be used to successfully estimate the service life of fly ash concrete.展开更多
Slippery lubricant-infused surfaces exhibit excellent fog-harvesting capacities compared with superhydrophobic and superhydrophilic surfaces.However,lubricant depletion is typically unavoidable under dynamic condition...Slippery lubricant-infused surfaces exhibit excellent fog-harvesting capacities compared with superhydrophobic and superhydrophilic surfaces.However,lubricant depletion is typically unavoidable under dynamic conditions,and reinfused oil is generally needed to recover the fog-harvesting capacity.Herein,an effective strategy for delaying the depletion of lubricant to prolong the service life of fog harvesting is proposed.An ultrathin transparent lubricant self-replenishing slippery surface was fabricated via facile one-step solvent evaporation polymerization.The gel film of the lubricant self-replenishing slippery surface,which was embedded with oil microdroplets,was attached to glass slides via the phase separation and evaporation of tetrahydrofuran.The gel film GFs-150(with oil content 150 wt%of aminopropyl-terminated polydimethyl siloxane(PDMS–NH2))exhibited superior slippery and fog-harvesting performance to other gel films.Furthermore,the slippery surfaces with the trait of oil secretion triggered by mechanical stress exhibited better fog-harvesting capabilities and longer service life than surfaces without the function of lubricant self-replenishment.The lubricant self-replenishing,ultrathin,and transparent slippery surfaces reported herein have considerable potential for applications involving narrow spaces,visualization,long service life,etc.展开更多
The low cell voltage during electrolytic Mn from the MnCl_(2) system can effectively reduce the power consumption.In this work,the Ti/Sn−Ru−Co−Zr modified anodes were obtained by using thermal decomposition oxidation....The low cell voltage during electrolytic Mn from the MnCl_(2) system can effectively reduce the power consumption.In this work,the Ti/Sn−Ru−Co−Zr modified anodes were obtained by using thermal decomposition oxidation.The physical parameters of coatings were observed by SEM(scanning electron microscope).Based on the electrochemical performance and SEM/XRD(X-ray diffraction)of the coatings,the influence of Zr on electrode performance was studied and analyzed.When the mole ratio of Sn−Ru−Co−Zr is 6:1:0.8:0.3,the cracks on the surface of coatings were the smallest,and the compactness was the best due to the excellent filling effect of ZrO_(2)nanoparticles.Moreover,the electrode prepared under this condition had the lowest mass transfer resistance and high chloride evolution activity in the 1mol%NH_(4)Cl and 1.5mol%HCl system.The service life of 3102 h was achieved according to the empirical formula of accelerated-life-test of the new type anode.展开更多
Time-to-cracking of the concrete cover induced by the steel corrosion is one of the critical problems faced by engineers, operators and asset managers in making strategies for the maintenance and repairs of reinforced...Time-to-cracking of the concrete cover induced by the steel corrosion is one of the critical problems faced by engineers, operators and asset managers in making strategies for the maintenance and repairs of reinforced concrete (RC) structures affected by corrosion. In this paper, a theoretical model for predicting the time-to-cracking is derived by assuming the bond between the steel bar and the concrete as a linear combination of perfectly smooth and bonded. The model takes into account the characteristics of existing exiguous flaws and initial cracks in the concrete before the load acting on RC structures. The validity of the proposed model is prehminarily verified by comparing the obtained results with the available experimental results. A remarkable advantage of the proposed method is its apphcation to the prediction of the service life of RC structures, made of the deformed steel bars as well as the round bars. By determining an experimental constant a, which is related to the interface bond state between the steel bar and the concrete, the service life of RC structures can be predicted using the proposed scheme. Analysis of major factors affecting the time-to-cracking demonstrates that the length of the initial crack affects the service life of RC structures significantly. Moreover, the larger cover thickness and the smaller diameter of the steel bar within a certain range are beneficial to prolonging the time-to-cracking.展开更多
In this paper, the bolt- and cable-supported structures mainly refer to anchored cables, anchored bolts, soil nails and other commonly used reinforcing and supporting structures in geotechnical engineering, as well as...In this paper, the bolt- and cable-supported structures mainly refer to anchored cables, anchored bolts, soil nails and other commonly used reinforcing and supporting structures in geotechnical engineering, as well as reinforced soil structures in permanent works. They are often used in combination, or formed into composite bolt-and cable-supported structures, with other traditional construction methods and relevant measures. Distinct characteristics of such structures are that they are most often invisible, exposed to more severe underground corrosive environments and with strict durability requirements. A number of serious durability problems of underground structures are discussed and major achievements and advances in China and abroad in terms of durability and reinforcement measures for underground structures are reviewed, followed by comprehensive analyses. Some suggestions for those problems are put forward.展开更多
Durability problem of reinforced concrete for underground structures is a hot issue in the field of structural engineering. For underground structures, the prediction of structural service life and methodology for dur...Durability problem of reinforced concrete for underground structures is a hot issue in the field of structural engineering. For underground structures, the prediction of structural service life and methodology for durability design are needed to estimate structural durability. Taking the case of Xiamen Xiang'an subsea tunnel as background, which is designed to meet the requirement of lO0-year service life, the influential factors on tunnel lining durability are analyzed. Under the criteria of crack controlling and bearing capacity of linin~ structures, the theoretical service life of Xiamen Xiang'an subsea tunnel lining is studied. The regulations, which are needed for the diffusion capability of chloride ions in concrete by the relevant diffusion tests, are proposed. After a quick corrosion test, the bearing capacity test on eccentric short columns is implemented to investigate the variation rules in the bearing capacity of models with time. Influence of the corrosion degree of steel bars on the bearing capacity of models is also investigated. Based on the results of model tests, the acceleration ratio between the quick corrosion in laboratory test and the natural corrosion environments is established. Thus, the natural service life of subsea tunnel lining structures can be obtained by means of laboratory tests. Then, the proposed method using this modified model is employed to predict the service life of tunnel lining structures. Finally, the design and construction measures for improving the durability of lining structures of subsea tunnel are introduced. The proposed method in the present study based on a real engineering project is superior to those with only theoretical assumptions, and would be more suitable for similar projects.展开更多
The paper provides a comprehensive scheme for assessment of the residual service life and extension of operating life of steam turbine rotors with expired fleet service life.The residual service life of high temperatu...The paper provides a comprehensive scheme for assessment of the residual service life and extension of operating life of steam turbine rotors with expired fleet service life.The residual service life of high temperature rotors for high&intermediate pressure cylinders of K-200-130-3 steam turbine without heat grooves calculated and it was showed that the residual service life of high&intermediate pressure rotors without grooves has been extended as compared to the K-200-130-1 turbine rotors with grooves.Also residual life management by supplying hot steam to the HPC and 1PC seals was investigated and it was noted their significant impact on the residual service life.展开更多
Physical properties of composite propellants used in solid rocket motors change significantly with age. To predict the margin of safety and to reevaluate the remaining service life, the structural integrity analysis o...Physical properties of composite propellants used in solid rocket motors change significantly with age. To predict the margin of safety and to reevaluate the remaining service life, the structural integrity analysis of solid propellant grains of aged rocket motors is performed at various stages of their life span. To have the reliable results from these analyses, it is mandatory to use the current physical properties of the propellant at the time of analysis. Change in physical properties due to aging is more significant at exposed surfaces. Traditional methods of assessing current physical properties may not truly rep resent the properties of the batch. The paper presents a novel technique to measure the stress strain response at the exposed surface of propellant grain using a miniature-testing device. This specially designed device is able to measure the stress response while the propellant surface is compressed at a constant rate. This measured stress strain behavior is then co-related with the physical properties measured by routine tensile tests of the similar type of propellant which is aged artificially. It is observed that there exists an excellent correlation between the measured stress values by the sensor and physical properties measured by uni-axial tensile test. This nondestructive technique provides properties of propellant grains of all the motors in the batch comprehensively. The technique is safe as well as economical as compared to the traditional methods.展开更多
The design and manufacture of spiral tap yet are in r esearch stage at present. This paper mainly introduces how to calculate its geom etric parameters and scientific selection of them with vector method. In additio n...The design and manufacture of spiral tap yet are in r esearch stage at present. This paper mainly introduces how to calculate its geom etric parameters and scientific selection of them with vector method. In additio n, an empiric formula of the tool life of spiral tap with large diameter is esta blished by method of correlation. The practice of design, manufacture and applying proves the advantage of spiral tap by the comparison between the spiral tap and common tap with same size. In the application of spiral tap has got better economic effect. The cutting fea ture and economic effect are obvious, that mean spiral tap greatly better than c ommon tap. The bright and wide prospect are going to come. No greatly increasing the ω can be effective to improve the cutting condition. Scientific selection of cutting speed V can increase the tool life of tapping and life of tapping too l.展开更多
基金Funded by the National Key Basic Research and Development Plans-973 Plans(2009CB623203)the Key Project of National Natural Science Foundation of China (50739001)+2 种基金the National Natural Science Foundation of China (50878109)the National Key Technology R & D Program (2007BAB27B03)the Education Ministry Doctor Foundation of China (20070429001)
文摘Qingdao Jiaozhou Bay subsea tunnel is the second self-built tunnel in China with the designed service life over 100 years.The durability of lining concrete are one of an important factors to determinate the service life of tunnel.Considering the main environmental loads and mechanical loads of subsea tunnel,the durability properties of lining concrete under combined action of compressive load and carbonation has been studied through the critical compressive load test,accelerated carbonation test,natural carbonation test and capillary suction test.The tests results show that critical compressive load apparently accelerates the carbonation and deteriorates the anti-permeability of concrete.Under the combined action of critical compressive load and carbonation,the durability of lining concrete decreases.Based on the carbonization life criteria and research results,for the high-performance concrete with proposed mix ratio,the predicted service life of lining concrete for Jiaozhou bay subsea tunnel is about 80 years which fails to reach the required service life.It is necessary to adopt other measurements simultaneously to improve the durability of lining concrete.
基金financial support provided by the National Natural Science Foundation of China(51508272,11832013,51878350,and 51678304)。
文摘In this study,through experimental research and an investigation on large datasets of the durability parameters in ocean engineering,the values,ranges,and types of distribution of the durability parameters employed for the durability design in ocean engineering in northern China were confirmed.Based on a modified theoretical model of chloride diffusion and the reliability theory,the service lives of concrete structures exposed to the splash,tidal,and underwater zones were calculated.Mixed concrete proportions meeting the requirement of a service life of 100 or 120 years were designed,and a cover thickness requirement was proposed.In addition,the effects of the different time-varying relationships of the boundary condition(Cs)and diffusion coefficient(Df)on the service life were compared;the results showed that the time-varying relationships used in this study(i.e.,Cscontinuously increased and then remained stable,and Dfcontinuously decreased and then remained stable)were beneficial for the durability design of concrete structures in marine environment.
文摘Effects of operation conditions such as ladle temperature, remining time of molten steel, slag basicity, slag oxidation, slag viscosity , vacuum treatment, ultra-high temperature, gas blowing and stirring, intermittent operation, and different refining equipment on service life of ladle lining refractories were researched. The following conclusions are drawn : (1) molten steel temperature rising, remaiaing time prolonging, slag oxidation ability enhancing, slag viscosity and basicity decreasing can aecelerate the corrosion of ladle lining ; (2) ultra-high temperature and vacuum treatment of ladle not only acceler- ate the fusion corrasion of ladle lining, but also make the carbon containing refractories react forming gases leading to more corrosion, so carbon containing refractories are not stdtable.for the smelting conditions of long term vacuum treatment and ultra-high temperature, especially carbon containing refractories added with conventional additives such as A1 and Si powders ; ( 3 ) argon blowing does not accelerate the corrosion of ladle lining obvioasly, but oxygen blowing does; (4) the corrosion degree of refractories varies with the refining equipment, and the service life of ladle lining decreases according to a certain proportion with the refining ratio increasing.
文摘The microstructures and mechanical properties of H13 mandrels made by Baosteel and foreign companies were investigated in this study. Based on the comparison research, the processes were optimized, such as steelmaking, heat treatment and multiple forging processes. The quality of Baosteel mandrels was greatly improved by increasing the homogenizing of an annealing temperature and refining processes. The results of the pilot trial showed that the average number of piercing steel tubes for Baosteel mandrels was over 3000 ,which reached the level of imported mandrels.
基金supported by the National Natural Science Foundation of China(Grant Nos.51878350 and 11832013).
文摘To solve the durability of island and reef concrete engineering in the harsh environment of high temperature,high salt,high humidity and windy,the strength grade of concrete and the type of corrosion inhibitor were used as the influence factors,while the relative dynamic elastic modulus was used as the evaluation index.In addition,the law and time variability of the deterioration of concrete,the size effect,environmental similarity and the service life model were studied.The results showed that improving the strength grade of concrete could improve the durability of concrete,and corrosion inhibitor could slightly improve the durability of concrete.Time-varying law of the deterioration of concrete conformed to the univariate quadratic polynomial.Combined with the concrete damage equivalent theory,a size effect model based on the relative dynamic elastic modulus was proposed and verified,and the size effect coefficient was also given.An environmental similarity model between simulated and practical island and reef environment was proposed.Combined with the reliability theory and the first order second moment method,a new service life model of concrete structure was proposed.The authors were convinced that the research will be advantageous to researchers.
文摘With the wide application of the magnesia-graphite refractory having a high-thermal-conductivity in BOF vessels for extending the furnace campaign, furnace shell deformation has become increasingly serious. It shortened the furnace campaign and reduced the production. The paper presents the work on increasing the life-span of the furnace shell at Baosteel, which includes the shell renovation, the study on the creep deformation resisting shell plates and the application of the air cooling method to the BOF shell. The results and limitations of these technologies are discussed.
基金Funded by the National Natural Science Foundation of China(No.51878081)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX21_1262)。
文摘A novel high-strength straight-hole recycled pervious concrete(HSRPC)for the secondary highway pavement was prepared in this paper.This study aimed to investigate the effect of porosity(0.126%,0.502%,and 1.13%),vehicle loading stress level(0.5 and 0.8)and service life on the resistance to rainstormbased waterlogging of HSRPC under fatigue loading.The mechanical properties of HSRPC in terms of flexural strength and dynamic elastic modulus were studied.The waterlogging resistance of HSRPC was described by surface water depth and drainage time.The microstructure of HSRPC were observed with scanning electron microscopy(SEM).Results showed that although the dynamic elastic modulus and flexural strength of HSRPC decreased with the increasing number of fatigue loading,the flexural strength of HSRPC was still greater than5 MPa after design service life of 20 years.After 2.5×10^(5)times of fatigue loading,the permeability coefficient of HSRPC with a porosity of 0.502%and 1.13%increased by 18.4%and 22.9%,respectively;while the permeability coefficient of HSRPC with 0.126%porosity dropped to 0.35 mm/s.The maximum surface water depth of HSRPC with a porosity of 0.126%,0.502%,and 1.13%were 8,5 and 4 mm,respectively.SEM results showed that fatigue loading expanded the number and width of cracks around the tiny pores in HSRPC.
基金a joint venture project between Istanbul University and the Turkish General Directorate of Highways by project number KGM-ARGE/2012-25funded by Istanbul University-Cerrahpasa Scientific Research Projects under Project No:ACIP 54739。
文摘In this paper the use of lime stabilized subgrade for low volume roads in two regions with high mountains and different frost penetration conditions in Türkiye was investigated in terms of design,performance,and cost.Pavements on unstabilized and stabilized subgrade were designed for two regions(Izmir and Van),covering all climate variations.The resilient modulus of the lime stabilized subgrade with different soil pulverization levels for non-freezing and freezing conditions were taken from a previous laboratory study.Frost effects were considered in pavement design using two different approaches,including limited subgrade frost penetration method and reduced subgrade strength method.Detailed application and evaluation were performed for all steps.Lime stabilized subgrades significantly reduced the thickness of base courses,and the benefit of lime stabilization was highly dependent on soil pulverization level.A detailed cost analysis on the unstabilized and stabilized cases found that the use of lime stabilization in the subgrade provided significant initial cost savings.Comparative analysis by using the AASHTO(1993)method and KENPAVE software,and quantity effect of soil pulverization level on the performance of low volume roads from a service life perspective,show that subgrade resilient modulus can be estimated.It is also possible to make correct performance estimation in the field.The results of the study show that lime stabilization is a good solution for low volume roads in the mountainous regions of Türkiye.
文摘The single crystal blade is one of the key technologies for improving the performance, durability and reliability of aero-engines and ground gas-turbine engines. However, the anisotropic mechanical properties of the single crystal material makes a great deal of difficulties on the development and the application of the single crystal blade, which is a challenge for the engineering application of the single crystal superalloy and the theoretic bases of the application. Some researches on the strength analysis and the life prediction of the anisotropic single crystal blade were carried out by the authors' research team. They are as follows. The crystallographic constitutive models for the plastic and the creep behaviors and the method of the rupture life prediction were established and verified. The tensile or the creep experiments for DD3 single crystal alloy with different orientations under different temperatures and different tensile rates or under different temperatures and different stress levels were carried out. The experimental data and the anisotropic properties at intermediate and high temperatures revealed by the experiments are significant for the application of the single crystal alloy. In addition, the experimental research for a kind of single crystal blade was also made. As the application of the researches the strength analysis and the life prediction were carried out for the single crystal blade of a certain aero-engine. In this part, the constitutive models and their applications are described, and the experimental research work will be described in part II.
文摘According to the chloride corrosion environment,service life prediction model of concrete structure of sea-crossing bridge was built using modified Fick's second law and the whole probability calculation method,which was suitable for China. Furthermore,a visual service life prediction program of concrete structure was developed by optimized Monte Carlo method. Meanwhile,Life 365 program was compared,indicating reliability of the prediction program. Finally,the validity of prediction model was verified in JinTang Bridge of Zhoushan Island Mainland Linkage Project.
基金This work was supported by the National Natural Science Foundation of China(Project No.21875253)CAS-Commonwealth Scientific and Industrial Research Organization(CSIRO)Joint Research Projects(121835KYSB20200039)Scientific Research and Equipment Development Project of CAS(YJKYYQ20190007).
文摘Potassium-ion hybrid capacitors(PIHCs)tactfully combining capacitor-type cathode with battery-type anode have recently attracted increasing attentions due to their advantages of decent energy density,high power density,and low cost;the mismatches of capacity and kinetics between capacitor-type cathode and battery-type anode in PIHCs yet hinder their overall performance output.Herein,based on prediction of density functional theory calculations,we find Se/N co-doped porous carbon is a promising candidate for K+storage and thus develop a simple and universal self-sacrifice template method to fabricate Se and N co-doped three-dimensional(3D)macroporous carbon(Se/N-3DMpC),which features favorable properties of connective hier-archical pores,expanded interlayer structure,and rich activity site for boosting pseudocapacitive activity and kinetics toward K^(+)storage anode and enhancing capacitance performance for the reversible anion adsorption/desorption cath-ode.As expected,the as-assembled PIHCs full cell with a working voltage as high as 4.0 V delivers a high energy density of 186 Wh kg^(−1) and a power output of 8100 W kg^(−1) as well as excellent long service life.The proof-of-concept PIHCs with excellent performance open a new avenue for the development and application of high-performance hybrid capacitors.
基金This research was sponsored by the General Directorate for Scientific Research and Technological Development(DGRSDT)of the Algerian Minister of Higher Education and Scientific Research.
文摘Carbonation is one of the most aggressive phenomena affecting reinforced concrete structures and causing their degradation over time.Once reinforcement is altered by carbonation,the structure will no longer fulfill service requirements.For this purpose,the present work estimates the lifetime of fly ash concrete by developing a carbonation depth prediction model that uses an artificial neural network technique.A collection of 300 data points was made from experimental results available in the published literature.Backpropagation training of a three-layer perceptron was selected for the calculation of weights and biases of the network to reach the desired performance.Six parameters affecting carbonation were used as input neurons:binder content,fly ash substitution rate,water/binder ratio,CO_(2)concentration,relative humidity,and concrete age.Moreover,experimental validation carried out for the developed model shows that the artificial neural network has strong potential as a feasible tool to accurately predict the carbonation depth of fly ash concrete.Finally,a mathematical formula is proposed that can be used to successfully estimate the service life of fly ash concrete.
基金This work was financially supported by the National Natural Science Foundation of China(No.51735013).
文摘Slippery lubricant-infused surfaces exhibit excellent fog-harvesting capacities compared with superhydrophobic and superhydrophilic surfaces.However,lubricant depletion is typically unavoidable under dynamic conditions,and reinfused oil is generally needed to recover the fog-harvesting capacity.Herein,an effective strategy for delaying the depletion of lubricant to prolong the service life of fog harvesting is proposed.An ultrathin transparent lubricant self-replenishing slippery surface was fabricated via facile one-step solvent evaporation polymerization.The gel film of the lubricant self-replenishing slippery surface,which was embedded with oil microdroplets,was attached to glass slides via the phase separation and evaporation of tetrahydrofuran.The gel film GFs-150(with oil content 150 wt%of aminopropyl-terminated polydimethyl siloxane(PDMS–NH2))exhibited superior slippery and fog-harvesting performance to other gel films.Furthermore,the slippery surfaces with the trait of oil secretion triggered by mechanical stress exhibited better fog-harvesting capabilities and longer service life than surfaces without the function of lubricant self-replenishment.The lubricant self-replenishing,ultrathin,and transparent slippery surfaces reported herein have considerable potential for applications involving narrow spaces,visualization,long service life,etc.
基金financially supported by the National Natural Science Foundation of China (Nos. 51564029, 51504111, 52064028, and 22002054)the China Postdoctoral Science Foundation (No. 2018M633418)+1 种基金the Technology Innovation Talents Project of Yunnan Province (No. 2019HB111)Analysis and Testing Foundation of Kunming University of Science and Technology (Nos. 2019 M20182202013, 2020M20192202035, and 2020M2019 2202099)
文摘The low cell voltage during electrolytic Mn from the MnCl_(2) system can effectively reduce the power consumption.In this work,the Ti/Sn−Ru−Co−Zr modified anodes were obtained by using thermal decomposition oxidation.The physical parameters of coatings were observed by SEM(scanning electron microscope).Based on the electrochemical performance and SEM/XRD(X-ray diffraction)of the coatings,the influence of Zr on electrode performance was studied and analyzed.When the mole ratio of Sn−Ru−Co−Zr is 6:1:0.8:0.3,the cracks on the surface of coatings were the smallest,and the compactness was the best due to the excellent filling effect of ZrO_(2)nanoparticles.Moreover,the electrode prepared under this condition had the lowest mass transfer resistance and high chloride evolution activity in the 1mol%NH_(4)Cl and 1.5mol%HCl system.The service life of 3102 h was achieved according to the empirical formula of accelerated-life-test of the new type anode.
基金supported by the National Natural Science Foundation of China (Grant No.50178003)
文摘Time-to-cracking of the concrete cover induced by the steel corrosion is one of the critical problems faced by engineers, operators and asset managers in making strategies for the maintenance and repairs of reinforced concrete (RC) structures affected by corrosion. In this paper, a theoretical model for predicting the time-to-cracking is derived by assuming the bond between the steel bar and the concrete as a linear combination of perfectly smooth and bonded. The model takes into account the characteristics of existing exiguous flaws and initial cracks in the concrete before the load acting on RC structures. The validity of the proposed model is prehminarily verified by comparing the obtained results with the available experimental results. A remarkable advantage of the proposed method is its apphcation to the prediction of the service life of RC structures, made of the deformed steel bars as well as the round bars. By determining an experimental constant a, which is related to the interface bond state between the steel bar and the concrete, the service life of RC structures can be predicted using the proposed scheme. Analysis of major factors affecting the time-to-cracking demonstrates that the length of the initial crack affects the service life of RC structures significantly. Moreover, the larger cover thickness and the smaller diameter of the steel bar within a certain range are beneficial to prolonging the time-to-cracking.
基金Supported by the National Natural Science Foundation of China (50279054 and 10772199)
文摘In this paper, the bolt- and cable-supported structures mainly refer to anchored cables, anchored bolts, soil nails and other commonly used reinforcing and supporting structures in geotechnical engineering, as well as reinforced soil structures in permanent works. They are often used in combination, or formed into composite bolt-and cable-supported structures, with other traditional construction methods and relevant measures. Distinct characteristics of such structures are that they are most often invisible, exposed to more severe underground corrosive environments and with strict durability requirements. A number of serious durability problems of underground structures are discussed and major achievements and advances in China and abroad in terms of durability and reinforcement measures for underground structures are reviewed, followed by comprehensive analyses. Some suggestions for those problems are put forward.
文摘Durability problem of reinforced concrete for underground structures is a hot issue in the field of structural engineering. For underground structures, the prediction of structural service life and methodology for durability design are needed to estimate structural durability. Taking the case of Xiamen Xiang'an subsea tunnel as background, which is designed to meet the requirement of lO0-year service life, the influential factors on tunnel lining durability are analyzed. Under the criteria of crack controlling and bearing capacity of linin~ structures, the theoretical service life of Xiamen Xiang'an subsea tunnel lining is studied. The regulations, which are needed for the diffusion capability of chloride ions in concrete by the relevant diffusion tests, are proposed. After a quick corrosion test, the bearing capacity test on eccentric short columns is implemented to investigate the variation rules in the bearing capacity of models with time. Influence of the corrosion degree of steel bars on the bearing capacity of models is also investigated. Based on the results of model tests, the acceleration ratio between the quick corrosion in laboratory test and the natural corrosion environments is established. Thus, the natural service life of subsea tunnel lining structures can be obtained by means of laboratory tests. Then, the proposed method using this modified model is employed to predict the service life of tunnel lining structures. Finally, the design and construction measures for improving the durability of lining structures of subsea tunnel are introduced. The proposed method in the present study based on a real engineering project is superior to those with only theoretical assumptions, and would be more suitable for similar projects.
文摘The paper provides a comprehensive scheme for assessment of the residual service life and extension of operating life of steam turbine rotors with expired fleet service life.The residual service life of high temperature rotors for high&intermediate pressure cylinders of K-200-130-3 steam turbine without heat grooves calculated and it was showed that the residual service life of high&intermediate pressure rotors without grooves has been extended as compared to the K-200-130-1 turbine rotors with grooves.Also residual life management by supplying hot steam to the HPC and 1PC seals was investigated and it was noted their significant impact on the residual service life.
文摘Physical properties of composite propellants used in solid rocket motors change significantly with age. To predict the margin of safety and to reevaluate the remaining service life, the structural integrity analysis of solid propellant grains of aged rocket motors is performed at various stages of their life span. To have the reliable results from these analyses, it is mandatory to use the current physical properties of the propellant at the time of analysis. Change in physical properties due to aging is more significant at exposed surfaces. Traditional methods of assessing current physical properties may not truly rep resent the properties of the batch. The paper presents a novel technique to measure the stress strain response at the exposed surface of propellant grain using a miniature-testing device. This specially designed device is able to measure the stress response while the propellant surface is compressed at a constant rate. This measured stress strain behavior is then co-related with the physical properties measured by routine tensile tests of the similar type of propellant which is aged artificially. It is observed that there exists an excellent correlation between the measured stress values by the sensor and physical properties measured by uni-axial tensile test. This nondestructive technique provides properties of propellant grains of all the motors in the batch comprehensively. The technique is safe as well as economical as compared to the traditional methods.
文摘The design and manufacture of spiral tap yet are in r esearch stage at present. This paper mainly introduces how to calculate its geom etric parameters and scientific selection of them with vector method. In additio n, an empiric formula of the tool life of spiral tap with large diameter is esta blished by method of correlation. The practice of design, manufacture and applying proves the advantage of spiral tap by the comparison between the spiral tap and common tap with same size. In the application of spiral tap has got better economic effect. The cutting fea ture and economic effect are obvious, that mean spiral tap greatly better than c ommon tap. The bright and wide prospect are going to come. No greatly increasing the ω can be effective to improve the cutting condition. Scientific selection of cutting speed V can increase the tool life of tapping and life of tapping too l.