During the thawing process of a railway subgrade,bidirectional thawing complicates water-heat transfer,leading to serious thaw settlement issues under train loads.Focusing on the severely frozen section of the Shuozho...During the thawing process of a railway subgrade,bidirectional thawing complicates water-heat transfer,leading to serious thaw settlement issues under train loads.Focusing on the severely frozen section of the Shuozhou-Huanghua port heavy-haul railway,this study conducted indoor soil-column laterally-limited compression tests on thawing fine-grained soil specimens to analyze the cumulative deformation during thawing.The deformation evolution was examined from both macroscopic and microscopic perspectives.The test results revealed a sig-nificant increase in the water content at the frozen interlayer during thawing,with minimal thaw settlement under no-load conditions.However,under dynamic loads,the thawing soil exhibited rapid settlement during the initial stages of the process.Increasing the dynamic load amplitude did not result in significant additional thaw settlement compression.Particle image velocimetry revealed substantial thaw settlement and compression at the top of thawing soil.Microscopically,the porosity at the top of the specimens significantly decreased,whereas the porosity in the frozen interlayer remained largely unchanged.Under dynamic loading,the specimens exhibited a concentrated distribution of large pores with scattered smaller pores.The phase change from ice to water,combined with dynamic loading,induced particle movement and expanded the inter-particle pore space,leading to macroscopic thaw settlement and soil compression.The findings can provide a theoretical foundation for maintaining and ensuring the safety of railway subgrades in cold regions.展开更多
Micro-structure related behavior of diffusion bonding joints is a crucial issue in device and reactor fabrication of Micro Chemo Mechanical Systems.However,the previous studies have been focused on the macro mechanica...Micro-structure related behavior of diffusion bonding joints is a crucial issue in device and reactor fabrication of Micro Chemo Mechanical Systems.However,the previous studies have been focused on the macro mechanical performance of diffusion bonded joint,especially diffusion bonding conditions effects on tensile strength,shearing strength and fatigue strength.The research of interfacial micro-voids and microstructures evolution for failure mechanism has not been carried out for diffusion-bonded joints.An interfacial electrical resistance measuring method is proposed to evaluate the quality of bonded joints and verified by using two-dimensional finite-element simulation.The influences of micro void geometry on increments of resistance are analyzed and the relationship between bonded area fraction and resistance increment is established by theoretical analysis combined with simulated results.Metallographic inspections and micro-hardness testing are conducted near the interface of diffusion bonded joints.For the purpose of identifying the failure mechanisms of the joints,both microscopic tensile and fatigue tests are conducted on the self-developed in-situ microscopic fatigue testing system.Based on the microscopic observations,the mechanism of interfacial failure is addressed.The observation result shows that for 316LSS diffusion-bonded joints,microstructure evolution and effect of micro-voids play a key role in interfacial failure mechanism.Finally,a new life prediction model in terms of the increment of electrical resistance is developed and confirmed by the experimental results.The proposed study is initiated that constituted a primary interfacial failure mechanism on micron scale and provide the life prediction for reliability of components sealed by diffusion bonding.展开更多
Epocast 50-A1/946 epoxy was primarily developed for joining and repairing of composite aircraft structural components. The objective of the present work is to modify the Epocast epoxy resin by different nanofillers in...Epocast 50-A1/946 epoxy was primarily developed for joining and repairing of composite aircraft structural components. The objective of the present work is to modify the Epocast epoxy resin by different nanofillers infusion. The used nanofillers include multi-walled carbon nanotubes（MWCNTs）, SiC and Al2O3 nanoparticles. The nanofillers with different weight percentages are ultrasonically dispersed in the epoxy resin. The sonication time and amplitude for MWCNTs are reduced compared to Al2O3 and SiC nanoparticles to avoid the damage of MWCNTs during sonication processes. The fabricated neat epoxy and twelve nanocomposite panels were characterized via standard tension and in-plane shear tests. The experimental results show that the nanocomposites materials with 0.5wt% MWCNTs, 1.5wt% SiC and 1.5wt% Al2O3 nanoparticles have the highest improvement in the tensile properties compared to the other nanofiller loading percentages.The improvements in the shear properties of these nanocomposite materials were respectively equal to 5.5%, 4.9%, and 6.3% for shear strengths, and 10.3%, 16.0%, and 8.1% for shear moduli. The optimum nanofiller loading percentages will be used in the following papers concerning their effect on the bonded joints/repairs of carbon fiber reinforced composites.展开更多
In order to study how to improve the overall performance of the operational metal bolt, based on the production process of an ordinary metal bolt used in understructure engineering, this paper focused on the existing ...In order to study how to improve the overall performance of the operational metal bolt, based on the production process of an ordinary metal bolt used in understructure engineering, this paper focused on the existing problems of ordinary metal bolts identified by some survey and analysis. The results show that the structure of operational metal bolts is so unrea- sonable that the bolt tail is easily fractured by low load capacity. Furthermore, a new type of strong big-end metal bolt and its heat treatment and roughing processing technology were introduced. Through bolt tensile and metallographic tests, the property of the new big-end bolt was analyzed. The new findings indicate that after a special processing, the overall strength and plasticity of the bolt is greatly improved, and the grain of the bolt tail structure is refined, which would help build up favorable working conditions for bolt tails.展开更多
Ion photon emission microscopy （IPEM） is a new ion-induced emission microscopy. It employs a broad ion beam with high energy and low fluence rate impinging on a sample. The position of a single ion is detected by an...Ion photon emission microscopy （IPEM） is a new ion-induced emission microscopy. It employs a broad ion beam with high energy and low fluence rate impinging on a sample. The position of a single ion is detected by an optical system with objective lens, prism, microscope tube and charge coupled device （CCD）. A thin ZnS film doped with Ag ions is used as a luminescent material. Generation efficiency and transmission efficiency of photons in the ZnS（Ag） film created by irradiated Cl ions are calculated. A single Cl ion optical microscopic image is observed by high quantum efficiency CCD. The resolution of a single Cl ion given in this IPEM system is 6μm. Several factors influencing the resolution are discussed. A silicon diode is used to collect the electrical signals caused by the incident ions. Effective and accidental coincidence of optical images and electronic signals are illustrated. A two-dimensional map of single event effect is drawn out according to the data of effective coincidence.展开更多
Earthen sites are widely distributed throughout China, and most of them belong to archaeological sites with significant values, which not only directly witness the origin, formation and development of Chinese civiliza...Earthen sites are widely distributed throughout China, and most of them belong to archaeological sites with significant values, which not only directly witness the origin, formation and development of Chinese civilization, but also possess important values for conservation and exhibition. Many researches and practices on their conservation and consolidation have been carried out; however, the consolidation effect is mainly judged by visual observation and expert evaluation. Scientific assessment of conservation and consolidation effects is a challenging issue. Many instruments in other fields cannot be directly applied to the conservation of cultural relics due to their peculiarity. In order to assess the effects of field conservation experiments, this paper tries to understand the consolidation effects at Liangzhu site using nondestructive or micro-damage methods, including thermo-physical parameters testing, infrared thermal imaging, high-density microelectrode resistivity testing, portable microscope observation, and hydrophilic and hydrophobic testing, and thereby explores the practicable methods for evaluating the properties of consolidation materials for earthen sites treatment.展开更多
To thoroughly investigate the damage evolution of anchorage structures under corrosive conditions,laboratory simulations of corrosive environments were conducted,including corrosion tests and mechanical performance ev...To thoroughly investigate the damage evolution of anchorage structures under corrosive conditions,laboratory simulations of corrosive environments were conducted,including corrosion tests and mechanical performance evaluations on anchorage systems.Based on experimental results,relationships were analyzed between factors(prestress,pH value,and anti-corrosion methods)and the corrosion degree,macro-micro characteristics,and mechanical performance degradation patterns of specimens.The results of the test indicated that:(1)the corrosion of coal bodies increases over time,and lower pH environments correspond to lower uniaxial compressive strength of coal bodies;(2)the corrosion of the rock bolts increases over time,the maximum mechanical performance in the rock bolts loss occurs at pH=5.0,and higher prestress of the rock bolts leads to greater mechanical degradation,and galvanization effectively reduces corrosion in functional rock bolts;(3)the degree of corrosion in the anchorage bodies has increases over time,pH=5.0 causes maximum bond strength of the anchorage bodies property loss and increases the prestress in the anchorage bodies exacerbates bond strength degradation,and double anti-protected anchorage bodies show less bond strength loss than ordinary ones.The corrosion-induced structural deterioration of underground anchorage systems leads to significant mechanical performance degradation,potentially causing support failure,surrounding rock instability,and roof fall disasters.Greater attention therefore needs to be paid to this area.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.52078312,52478461,and 52408379)the Natural Science Foundation of Hebei Province(E2024210134)+2 种基金the Innovative Research Group Project of the Natural Science Foundation of Hebei Province(Grant No.E2021210099)CCCC Science and Technology R&D Project(Grant No.2021-ZJKJ-01)the S&T Program of Hebei(Grant No.225A0802D).
文摘During the thawing process of a railway subgrade,bidirectional thawing complicates water-heat transfer,leading to serious thaw settlement issues under train loads.Focusing on the severely frozen section of the Shuozhou-Huanghua port heavy-haul railway,this study conducted indoor soil-column laterally-limited compression tests on thawing fine-grained soil specimens to analyze the cumulative deformation during thawing.The deformation evolution was examined from both macroscopic and microscopic perspectives.The test results revealed a sig-nificant increase in the water content at the frozen interlayer during thawing,with minimal thaw settlement under no-load conditions.However,under dynamic loads,the thawing soil exhibited rapid settlement during the initial stages of the process.Increasing the dynamic load amplitude did not result in significant additional thaw settlement compression.Particle image velocimetry revealed substantial thaw settlement and compression at the top of thawing soil.Microscopically,the porosity at the top of the specimens significantly decreased,whereas the porosity in the frozen interlayer remained largely unchanged.Under dynamic loading,the specimens exhibited a concentrated distribution of large pores with scattered smaller pores.The phase change from ice to water,combined with dynamic loading,induced particle movement and expanded the inter-particle pore space,leading to macroscopic thaw settlement and soil compression.The findings can provide a theoretical foundation for maintaining and ensuring the safety of railway subgrades in cold regions.
基金supported by National Natural Science Foundation of China(Grant No.50475068)
文摘Micro-structure related behavior of diffusion bonding joints is a crucial issue in device and reactor fabrication of Micro Chemo Mechanical Systems.However,the previous studies have been focused on the macro mechanical performance of diffusion bonded joint,especially diffusion bonding conditions effects on tensile strength,shearing strength and fatigue strength.The research of interfacial micro-voids and microstructures evolution for failure mechanism has not been carried out for diffusion-bonded joints.An interfacial electrical resistance measuring method is proposed to evaluate the quality of bonded joints and verified by using two-dimensional finite-element simulation.The influences of micro void geometry on increments of resistance are analyzed and the relationship between bonded area fraction and resistance increment is established by theoretical analysis combined with simulated results.Metallographic inspections and micro-hardness testing are conducted near the interface of diffusion bonded joints.For the purpose of identifying the failure mechanisms of the joints,both microscopic tensile and fatigue tests are conducted on the self-developed in-situ microscopic fatigue testing system.Based on the microscopic observations,the mechanism of interfacial failure is addressed.The observation result shows that for 316LSS diffusion-bonded joints,microstructure evolution and effect of micro-voids play a key role in interfacial failure mechanism.Finally,a new life prediction model in terms of the increment of electrical resistance is developed and confirmed by the experimental results.The proposed study is initiated that constituted a primary interfacial failure mechanism on micron scale and provide the life prediction for reliability of components sealed by diffusion bonding.
基金funded by King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia under Grant DRP-5-3financial support of KACST
文摘Epocast 50-A1/946 epoxy was primarily developed for joining and repairing of composite aircraft structural components. The objective of the present work is to modify the Epocast epoxy resin by different nanofillers infusion. The used nanofillers include multi-walled carbon nanotubes（MWCNTs）, SiC and Al2O3 nanoparticles. The nanofillers with different weight percentages are ultrasonically dispersed in the epoxy resin. The sonication time and amplitude for MWCNTs are reduced compared to Al2O3 and SiC nanoparticles to avoid the damage of MWCNTs during sonication processes. The fabricated neat epoxy and twelve nanocomposite panels were characterized via standard tension and in-plane shear tests. The experimental results show that the nanocomposites materials with 0.5wt% MWCNTs, 1.5wt% SiC and 1.5wt% Al2O3 nanoparticles have the highest improvement in the tensile properties compared to the other nanofiller loading percentages.The improvements in the shear properties of these nanocomposite materials were respectively equal to 5.5%, 4.9%, and 6.3% for shear strengths, and 10.3%, 16.0%, and 8.1% for shear moduli. The optimum nanofiller loading percentages will be used in the following papers concerning their effect on the bonded joints/repairs of carbon fiber reinforced composites.
文摘In order to study how to improve the overall performance of the operational metal bolt, based on the production process of an ordinary metal bolt used in understructure engineering, this paper focused on the existing problems of ordinary metal bolts identified by some survey and analysis. The results show that the structure of operational metal bolts is so unrea- sonable that the bolt tail is easily fractured by low load capacity. Furthermore, a new type of strong big-end metal bolt and its heat treatment and roughing processing technology were introduced. Through bolt tensile and metallographic tests, the property of the new big-end bolt was analyzed. The new findings indicate that after a special processing, the overall strength and plasticity of the bolt is greatly improved, and the grain of the bolt tail structure is refined, which would help build up favorable working conditions for bolt tails.
基金Supported by the National Natural Science Foundation of China under Grant No 11690044
文摘Ion photon emission microscopy （IPEM） is a new ion-induced emission microscopy. It employs a broad ion beam with high energy and low fluence rate impinging on a sample. The position of a single ion is detected by an optical system with objective lens, prism, microscope tube and charge coupled device （CCD）. A thin ZnS film doped with Ag ions is used as a luminescent material. Generation efficiency and transmission efficiency of photons in the ZnS（Ag） film created by irradiated Cl ions are calculated. A single Cl ion optical microscopic image is observed by high quantum efficiency CCD. The resolution of a single Cl ion given in this IPEM system is 6μm. Several factors influencing the resolution are discussed. A silicon diode is used to collect the electrical signals caused by the incident ions. Effective and accidental coincidence of optical images and electronic signals are illustrated. A two-dimensional map of single event effect is drawn out according to the data of effective coincidence.
基金supported by the National"12th Five-Year"Plan for Science and Technology Support(Grant No.2014BAK16B02)the Key Project of the State Administration of Cultural Heritage(Grant No.20120207)the Project on Basic Research of Gansu Province's Innovation Group(Grant No.145RJIF336)
文摘Earthen sites are widely distributed throughout China, and most of them belong to archaeological sites with significant values, which not only directly witness the origin, formation and development of Chinese civilization, but also possess important values for conservation and exhibition. Many researches and practices on their conservation and consolidation have been carried out; however, the consolidation effect is mainly judged by visual observation and expert evaluation. Scientific assessment of conservation and consolidation effects is a challenging issue. Many instruments in other fields cannot be directly applied to the conservation of cultural relics due to their peculiarity. In order to assess the effects of field conservation experiments, this paper tries to understand the consolidation effects at Liangzhu site using nondestructive or micro-damage methods, including thermo-physical parameters testing, infrared thermal imaging, high-density microelectrode resistivity testing, portable microscope observation, and hydrophilic and hydrophobic testing, and thereby explores the practicable methods for evaluating the properties of consolidation materials for earthen sites treatment.
基金supported by the National Natural Science Foundation of China:Damage Mechanism and Stability Precursor Characteristics of Gradient Enclosure Structures in Impact Hazardous Roadways under Dynamic and Static Loads(No.52374201).
文摘To thoroughly investigate the damage evolution of anchorage structures under corrosive conditions,laboratory simulations of corrosive environments were conducted,including corrosion tests and mechanical performance evaluations on anchorage systems.Based on experimental results,relationships were analyzed between factors(prestress,pH value,and anti-corrosion methods)and the corrosion degree,macro-micro characteristics,and mechanical performance degradation patterns of specimens.The results of the test indicated that:(1)the corrosion of coal bodies increases over time,and lower pH environments correspond to lower uniaxial compressive strength of coal bodies;(2)the corrosion of the rock bolts increases over time,the maximum mechanical performance in the rock bolts loss occurs at pH=5.0,and higher prestress of the rock bolts leads to greater mechanical degradation,and galvanization effectively reduces corrosion in functional rock bolts;(3)the degree of corrosion in the anchorage bodies has increases over time,pH=5.0 causes maximum bond strength of the anchorage bodies property loss and increases the prestress in the anchorage bodies exacerbates bond strength degradation,and double anti-protected anchorage bodies show less bond strength loss than ordinary ones.The corrosion-induced structural deterioration of underground anchorage systems leads to significant mechanical performance degradation,potentially causing support failure,surrounding rock instability,and roof fall disasters.Greater attention therefore needs to be paid to this area.
