Ultrasonic scalpel design for minimally invasive surgical procedures is mainly focused on optimizing cutting performance.However,an important issue is the low fatigue life of traditional ultrasonic scalpels,which affe...Ultrasonic scalpel design for minimally invasive surgical procedures is mainly focused on optimizing cutting performance.However,an important issue is the low fatigue life of traditional ultrasonic scalpels,which affects their long-term reliability and effectiveness and creates hidden dangers for surgery.In this study,a multi-objective optimal design for the cutting performance and fatigue life of ultrasonic scalpels was proposed using finite element analysis and fatigue simulation.The optimal design parameters of resonance frequency and amplitude were determined.By setting the transition fillet and keeping the gain structure away from the node position to enable the scalpel to have a high service life with excellent cutting performance.The frequency modulation method of setting the vibration node bosses at the node position and setting the vibration antinode grooves at the antinode position was compared.Then,the mechanism of the influence of various design elements,such as tip,shank,node position,and antinode position,on the resonance frequency,amplitude,and fatigue life of the ultrasonic scalpel was analyzed,and the optimal design principles of the ultrasonic scalpel were obtained.The proposed ultrasonic scalpel design was confirmed by simulations,impedance measurements,and liver tissue cutting experiments,demonstrating its feasibility and enhanced performance.This research introduces innovative design strategies to improve the fatigue life and performance of ultrasonic scalpels to address an important issue in minimally invasive surgery.展开更多
In order to further simulate the real condition of pavements during the service life,moisture is considered in long-term aging tests based on the existing researches about thermal aging and oxidation aging of asphalt....In order to further simulate the real condition of pavements during the service life,moisture is considered in long-term aging tests based on the existing researches about thermal aging and oxidation aging of asphalt.Water is injected into the pressure aging vessel（PAV）to simulate the aging process during the service life.The performance-based strategic highway research program（SHRP）parameters G/sinδ and S（t）are adopted to evaluate the high-temperature properties and low-temperature properties of the aged asphalt,respectively.The Thailand 90# asphalt,the modified Thailand 90# asphalt and the Shell 70# asphalt are used in the test.It is found that the moisture has a significant influence on parameter G/sinδ when combined with heat and oxygen,so water aging makes high-temperature performance decay more seriously.But the low-temperature performance does not change remarkably after water aging.Since the influences of temperature,oxygen and water are taken into account in the PAV test,the accuracy of asphalt aging tests can be improved and the long-term aging process of asphalt pavement can be exactly simulated.展开更多
Aim To study the theory and method for the prediction of service life of solid rocket propellant grain. Methods With the aid of discontiguous diagnostic technology and method of accumulated damage using accelerated...Aim To study the theory and method for the prediction of service life of solid rocket propellant grain. Methods With the aid of discontiguous diagnostic technology and method of accumulated damage using accelerated aging or heat air oven, the aging isotherms for void content versus aging time were determined. According to the principle of time temperature equivalence the viscoelastic master curve for the prediction of service life were obtained. Results and Conclusion The service life of HMX CMDB solid rocket propellant grain were obtained. Because the critical storage life is measured, the accuracy of predicting the service life of the grain has been increased greatly.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
Chloride-induced corrosion of the reinforcement is considered as one of the major mechanisms resulting in the reduction of structural resistance of reinforced concrete structural elements located in marine and other a...Chloride-induced corrosion of the reinforcement is considered as one of the major mechanisms resulting in the reduction of structural resistance of reinforced concrete structural elements located in marine and other aggressive environments. A study of reinforced concrete structures located at the Fangcheng dock in the Beibu Gulf port, China, was present. The result from field survey indicates that the concrete cover depth and chloride diffusion coefficient fit best normal distribution and lognormal distribution, respectively. The service life of structure is about 55 a, while initiation time is 45 a. Sensitivity analysis indicates that the most influential factor of the structure service life prediction is concrete cover, followed by diffusion coefficient, diffusion decay index, critical chloride concentration, surface chloride concentration, current density and localized pitting corrosion. Finally, the effects of diffusion decay index and critical chloride concentration on structure service life prediction are discussed.展开更多
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
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
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
Service life is often used by state transportation agencies to evaluate alternative flexible pavement designs.The design that keeps the pavement in acceptable condition longest before it needs another maintenance trea...Service life is often used by state transportation agencies to evaluate alternative flexible pavement designs.The design that keeps the pavement in acceptable condition longest before it needs another maintenance treatment is the preferred design.For a given rehabilitation design,this study evaluates the pavement service life using AASHTO 1972 pavement design guide and mechanistic-empirical(M-E)pavement design guide.The service life here is referred as the duration from last completed rehabilitation to the next maintenance treatment.The goal is not to determine which method is better,but rather,it is to understand how their estimated service lives differ and what factors contribute to their differences.To perform the evaluation,rehabilitation designs developed by the SCDOT for a research project are used.These designs take into account existing pavement distresses obtained through field investigation of 28 actual rehabilitation projects on primary routes.Service life is determined using MAP-21 criteria for good and fair pavements.Analysis results indicated that(1)the predicted service life using the M-E method has lower variation than the AASHTO 1972 method and is affected by the location(rural vs.urban)of the routes,(2)the predicted service life using the AASHTO 1972 method is generally lower than that of the M-E method and is affected by the difference between the design structural number(SN)and required SN,(3)the M-E service life for good pavement is generally longer for routes that include CMRB design and the percentage of trucks lower than 10%,and(4)the AASHTO 1972 service life is higher if the existing SN is already exceeding the required SN from the previous maintenance.展开更多
SnO2intermediate layers were coated on the titanium(Ti)substrate by thermal decomposition.Scanning electronmicroscope(SEM)and X-ray diffraction(XRD)results show that uniform SnO2intermediate layers with rutile crystal...SnO2intermediate layers were coated on the titanium(Ti)substrate by thermal decomposition.Scanning electronmicroscope(SEM)and X-ray diffraction(XRD)results show that uniform SnO2intermediate layers with rutile crystal structure weresuccessfully achieved.According to the results of linear sweep voltammetry(LSV),oxygen evolution potential(OEP)of theTi/SnO2/MnO2electrodes decreases with increasing SnO2content,indicating that the electro-catalytic oxidation activity of theelectrode increases.Accelerated service life tests results demonstrate that SnO2intermediate layer can improve the service life of theTi/SnO2/MnO2electrode.As the content of SnO2intermediate layer increases,the cell voltage and the energy consumption decreaseapparently.展开更多
The basic element in any sustainable dam project is safety, which includes the following safety elements： O structural safety, dam safety monitoring, operational safety and maintenance, and emergency planning. Lon...The basic element in any sustainable dam project is safety, which includes the following safety elements： O structural safety, dam safety monitoring, operational safety and maintenance, and emergency planning. Long-term safety primarily includes the analysis of all hazards affecting the project; that is, hazards from the natural environment, hazards from the man-made environment, and project-specific and site-specific hazards. The special features of the seismic safety of dams are discussed. Large dams were the first structures to be systematically designed against earthquakes, starting in the 1930s. How- ever, the seismic safety of older dams is unknown, as most were designed using seismic design criteria and methods of dynamic analysis that are considered obsolete today. Therefore, we need to reevaluate the seismic safety of existing dams based on current state-of-the-art practices and rehabilitate deficient dams. For large dams, a site-specific seismic hazard analysis is usually recommended. Today, large dams and the safety-relevant elements used for controlling the reservoir after a strong earthquake must be able to withstand the ground motions of a safety evaluation earthquake. The ground motion parameters can be determined either by a probabilistic or a deterministic seismic hazard analysis. During strong earthquakes, inelastic deformations may occur in a dam; therefore, the seismic analysis has to be car- ried out in the time domain. Furthermore, earthquakes create multiple seismic hazards for dams such as ground shaking, fault movements, mass movements, and others. The ground motions needed by the dam engineer are not real earthquake ground motions but models of the ground motion, which allow the safe design of dams. It must also be kept in mind that darn safety evaluations must be carried out several times during the long life of large storage dams. These features are discussed in this paper.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
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
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
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 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
Nowadays, clients require solutions that are efficient during the service life as a whole. In this view, maintenance has functional value and greatly contributes to increasing quality in environments. With reference t...Nowadays, clients require solutions that are efficient during the service life as a whole. In this view, maintenance has functional value and greatly contributes to increasing quality in environments. With reference to maintenance phase and residual value of building products upon dismantling, the present manuscript investigates a set of technological packages of quality and technical value referred to two alternative facade systems available for recovery actions on Italian council buildings--the ETICS （external thermal insulation composite system） and the external cladding system--complying with one thermal-insulation strategy, but different in terms of service life duration. Preservation of technical value and value increases are strictly related to maintenance quality and efficiency. Volume of investments in maintenance is not the only parameter to be considered to assess facade-system-management quality. Time-accurate economic assessment requires the entity to be related to periodical checks on performance quality in the building system and in its parts. Effective technical data to draw up consistent estimates and appraisals are rarely available in literature. With all that stated above, the present manuscript aims at introducing technical data related to drawing up reliable cost estimates and effective appraisals in terms of economics, quality and environmental sustainability. Conclusions will be drawn from the end of the manuscript.展开更多
基金Supported by National Natural Science Foundation of China (Grant Nos.52005199,42241149)Shenzhen Fundamental Research Program of China (Grant Nos.JCYJ20200109150425085,JCYJ20220818102601004)+1 种基金Knowledge Innovation Program of Wuhan-Basic Research of China (Grant No.2022010801010203)Shenzhen Science and Technology Program of China (Grant Nos.JSGG20201103100001004,JSGG20220831105800001)。
文摘Ultrasonic scalpel design for minimally invasive surgical procedures is mainly focused on optimizing cutting performance.However,an important issue is the low fatigue life of traditional ultrasonic scalpels,which affects their long-term reliability and effectiveness and creates hidden dangers for surgery.In this study,a multi-objective optimal design for the cutting performance and fatigue life of ultrasonic scalpels was proposed using finite element analysis and fatigue simulation.The optimal design parameters of resonance frequency and amplitude were determined.By setting the transition fillet and keeping the gain structure away from the node position to enable the scalpel to have a high service life with excellent cutting performance.The frequency modulation method of setting the vibration node bosses at the node position and setting the vibration antinode grooves at the antinode position was compared.Then,the mechanism of the influence of various design elements,such as tip,shank,node position,and antinode position,on the resonance frequency,amplitude,and fatigue life of the ultrasonic scalpel was analyzed,and the optimal design principles of the ultrasonic scalpel were obtained.The proposed ultrasonic scalpel design was confirmed by simulations,impedance measurements,and liver tissue cutting experiments,demonstrating its feasibility and enhanced performance.This research introduces innovative design strategies to improve the fatigue life and performance of ultrasonic scalpels to address an important issue in minimally invasive surgery.
基金The National Natural Science Foundation of China(No.50878054)
文摘In order to further simulate the real condition of pavements during the service life,moisture is considered in long-term aging tests based on the existing researches about thermal aging and oxidation aging of asphalt.Water is injected into the pressure aging vessel（PAV）to simulate the aging process during the service life.The performance-based strategic highway research program（SHRP）parameters G/sinδ and S（t）are adopted to evaluate the high-temperature properties and low-temperature properties of the aged asphalt,respectively.The Thailand 90# asphalt,the modified Thailand 90# asphalt and the Shell 70# asphalt are used in the test.It is found that the moisture has a significant influence on parameter G/sinδ when combined with heat and oxygen,so water aging makes high-temperature performance decay more seriously.But the low-temperature performance does not change remarkably after water aging.Since the influences of temperature,oxygen and water are taken into account in the PAV test,the accuracy of asphalt aging tests can be improved and the long-term aging process of asphalt pavement can be exactly simulated.
文摘Aim To study the theory and method for the prediction of service life of solid rocket propellant grain. Methods With the aid of discontiguous diagnostic technology and method of accumulated damage using accelerated aging or heat air oven, the aging isotherms for void content versus aging time were determined. According to the principle of time temperature equivalence the viscoelastic master curve for the prediction of service life were obtained. Results and Conclusion The service life of HMX CMDB solid rocket propellant grain were obtained. Because the critical storage life is measured, the accuracy of predicting the service life of the grain has been increased greatly.
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.
基金Project(41274012) supported by the National Natural Science Foundation of China
文摘Chloride-induced corrosion of the reinforcement is considered as one of the major mechanisms resulting in the reduction of structural resistance of reinforced concrete structural elements located in marine and other aggressive environments. A study of reinforced concrete structures located at the Fangcheng dock in the Beibu Gulf port, China, was present. The result from field survey indicates that the concrete cover depth and chloride diffusion coefficient fit best normal distribution and lognormal distribution, respectively. The service life of structure is about 55 a, while initiation time is 45 a. Sensitivity analysis indicates that the most influential factor of the structure service life prediction is concrete cover, followed by diffusion coefficient, diffusion decay index, critical chloride concentration, surface chloride concentration, current density and localized pitting corrosion. Finally, the effects of diffusion decay index and critical chloride concentration on structure service life prediction are discussed.
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.
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.
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.
文摘Service life is often used by state transportation agencies to evaluate alternative flexible pavement designs.The design that keeps the pavement in acceptable condition longest before it needs another maintenance treatment is the preferred design.For a given rehabilitation design,this study evaluates the pavement service life using AASHTO 1972 pavement design guide and mechanistic-empirical(M-E)pavement design guide.The service life here is referred as the duration from last completed rehabilitation to the next maintenance treatment.The goal is not to determine which method is better,but rather,it is to understand how their estimated service lives differ and what factors contribute to their differences.To perform the evaluation,rehabilitation designs developed by the SCDOT for a research project are used.These designs take into account existing pavement distresses obtained through field investigation of 28 actual rehabilitation projects on primary routes.Service life is determined using MAP-21 criteria for good and fair pavements.Analysis results indicated that(1)the predicted service life using the M-E method has lower variation than the AASHTO 1972 method and is affected by the location(rural vs.urban)of the routes,(2)the predicted service life using the AASHTO 1972 method is generally lower than that of the M-E method and is affected by the difference between the design structural number(SN)and required SN,(3)the M-E service life for good pavement is generally longer for routes that include CMRB design and the percentage of trucks lower than 10%,and(4)the AASHTO 1972 service life is higher if the existing SN is already exceeding the required SN from the previous maintenance.
基金Project(51574287) supported by the National Natural Science Foundation of ChinaProject supported by the Collaborative Innovation Center of Manganese-Zinc-Vanadium Industrial Technology
文摘SnO2intermediate layers were coated on the titanium(Ti)substrate by thermal decomposition.Scanning electronmicroscope(SEM)and X-ray diffraction(XRD)results show that uniform SnO2intermediate layers with rutile crystal structure weresuccessfully achieved.According to the results of linear sweep voltammetry(LSV),oxygen evolution potential(OEP)of theTi/SnO2/MnO2electrodes decreases with increasing SnO2content,indicating that the electro-catalytic oxidation activity of theelectrode increases.Accelerated service life tests results demonstrate that SnO2intermediate layer can improve the service life of theTi/SnO2/MnO2electrode.As the content of SnO2intermediate layer increases,the cell voltage and the energy consumption decreaseapparently.
文摘The basic element in any sustainable dam project is safety, which includes the following safety elements： O structural safety, dam safety monitoring, operational safety and maintenance, and emergency planning. Long-term safety primarily includes the analysis of all hazards affecting the project; that is, hazards from the natural environment, hazards from the man-made environment, and project-specific and site-specific hazards. The special features of the seismic safety of dams are discussed. Large dams were the first structures to be systematically designed against earthquakes, starting in the 1930s. How- ever, the seismic safety of older dams is unknown, as most were designed using seismic design criteria and methods of dynamic analysis that are considered obsolete today. Therefore, we need to reevaluate the seismic safety of existing dams based on current state-of-the-art practices and rehabilitate deficient dams. For large dams, a site-specific seismic hazard analysis is usually recommended. Today, large dams and the safety-relevant elements used for controlling the reservoir after a strong earthquake must be able to withstand the ground motions of a safety evaluation earthquake. The ground motion parameters can be determined either by a probabilistic or a deterministic seismic hazard analysis. During strong earthquakes, inelastic deformations may occur in a dam; therefore, the seismic analysis has to be car- ried out in the time domain. Furthermore, earthquakes create multiple seismic hazards for dams such as ground shaking, fault movements, mass movements, and others. The ground motions needed by the dam engineer are not real earthquake ground motions but models of the ground motion, which allow the safe design of dams. It must also be kept in mind that darn safety evaluations must be carried out several times during the long life of large storage dams. These features are discussed in this paper.
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.
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.
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.
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.
文摘Nowadays, clients require solutions that are efficient during the service life as a whole. In this view, maintenance has functional value and greatly contributes to increasing quality in environments. With reference to maintenance phase and residual value of building products upon dismantling, the present manuscript investigates a set of technological packages of quality and technical value referred to two alternative facade systems available for recovery actions on Italian council buildings--the ETICS （external thermal insulation composite system） and the external cladding system--complying with one thermal-insulation strategy, but different in terms of service life duration. Preservation of technical value and value increases are strictly related to maintenance quality and efficiency. Volume of investments in maintenance is not the only parameter to be considered to assess facade-system-management quality. Time-accurate economic assessment requires the entity to be related to periodical checks on performance quality in the building system and in its parts. Effective technical data to draw up consistent estimates and appraisals are rarely available in literature. With all that stated above, the present manuscript aims at introducing technical data related to drawing up reliable cost estimates and effective appraisals in terms of economics, quality and environmental sustainability. Conclusions will be drawn from the end of the manuscript.
