Defects in protective-coating systems on steel surfaces are inevitable in practical engineering applications. A composite coating system, including a primer, middle coat and topcoat, were used to protect carbon steel ...Defects in protective-coating systems on steel surfaces are inevitable in practical engineering applications. A composite coating system, including a primer, middle coat and topcoat, were used to protect carbon steel from corrosion in a marine environment. Two environmental additives, glass fibers and thiourea, were applied in the middle coat to modify the coating system. The long-term corrosion durability and self-healing ability of the scratched coating system were evaluated by multiple methods. Results of the electrochemical technologies indicated that the coating system that contained 0.5 wt.% fibers and 0.5 wt.% thiourea presented good corrosion protection and self-healing for carbon steel when immersed in 3.5% NaCl for 120 d. Evolution of localized corrosion factors with time, as obtained from the current distribution showed that fibers combined with thiourea could inhibit the occurrence of local corrosion in scratched coating systems and retarded the corrosion development significantly. Surface characterization suggested that adequate thiourea could be absorbed tmiformly on fibers for a long time to play an important role in protecting the carbon steel. Finally, schematic models were established to demonstrate the action of fibers and thiourea on the exposed surface of the carbon steel and the scratched coating system in the entire deterioration process.展开更多
Scratch damage can reduce both the aesthetic appearance and structural integrity of polymer surfaces.To optimize and enhance the scratch resistance of polycarbonate,this study investigates the influence of assembly pr...Scratch damage can reduce both the aesthetic appearance and structural integrity of polymer surfaces.To optimize and enhance the scratch resistance of polycarbonate,this study investigates the influence of assembly pre-tensile and pre-compressive stresses,with scratch experiments being conducted under both linearly increasing and constant normal load modes.Experimental results and finite element simulations are used to analyze scratch resistance and visibility.The results indicate that the application of 20%pre-compressive stress increases the critical normal load for onset of scratch visibility by 42%compared with the case in which no assembly pre-stress is applied,and it effectively decreases residual scratch depth,shoulder height,shoulder width,and tangential load.This is because assembly pre-compressive stress can effectively counteract the extrusion of material at the front and sides caused by the sliding scratch tip.Pre-compressive stress hinders scratch groove formation,improving the scratch resistance of polycarbonate.By contrast,pre-tensile stress weakens these characteristics.This study provides valuable insights for enhancing the surface damage resistance of polycarbonate materials.展开更多
Correlations between the mechanical properties and surface scratch resistance of polylactic acid(PLA)are investigated via tensile and scratch tests on samples after degradation in soil for various times.The results sh...Correlations between the mechanical properties and surface scratch resistance of polylactic acid(PLA)are investigated via tensile and scratch tests on samples after degradation in soil for various times.The results show that the tensile yield strength of PLA is inversely proportional to the natural logarithm of the degradation time,and the scratch resistance and fracture toughness of PLA and the temperature rise near the indenter all increase and then decrease.The surface crystallinity of PLA also increases and then decreases,indicating that it and the scratch resistance are closely related.These findings provide useful information about how PLA behaves under degradation conditions.展开更多
Chronic long-segment iliac artery occlusion represents a relatively rare and particularly severe form of iliac artery disease,often associated with complex anatomical challenges.When symptomatic,these patients are typ...Chronic long-segment iliac artery occlusion represents a relatively rare and particularly severe form of iliac artery disease,often associated with complex anatomical challenges.When symptomatic,these patients are typically candidates for surgical revascularization.展开更多
The fused quartz hemispherical resonator is the core component of the hemispherical resonator gyroscope.It features a complex shape and is Made from a Material that is difficult to process.Scratches are easily introdu...The fused quartz hemispherical resonator is the core component of the hemispherical resonator gyroscope.It features a complex shape and is Made from a Material that is difficult to process.Scratches are easily introduced during grinding,potentially degrading the mass-stiffness-damping symmetry;however,the underlying mechanisms of this influence have not been fully understood.This paper aims to investigate the effects of scratch defects on the frequency splitting and quality factor of the hemispherical resonator.First,finite element models of the hemispherical resonator with scratches are established.Then,the effects of the mass-stiffness factor,as well as the latitude and length of the scratches,on frequency splitting are analyzed.Furthermore,the impacts of latitude,length,and the first four harmonics of the unbalanced mass caused by scratches on thermoelastic damping and anchor loss are examined.Simulation results indicate that scratches above 55°latitude cause frequency splitting solely due to stiffness changes.Frequency splitting caused by scratches of the same size on the inherent rigidity shaft at the rim is approximately 50%of that near the transition fillet.Frequency splitting varies linearly with the volume of material removed by scratches.Scratches have little effect on thermoelastic damping.The first three harmonics of the unbalanced mass due to scratches at the rim are the primary contributors to anchor loss.Finally,focused ion beam trimming experiments are conducted at different locations on the hemispherical resonator.The trends observed in the experimental results are consistent with the simulation results.This work provides guidance for evaluating the impact of scratches on the performance of hemispherical resonators and for developing appropriate trimming processes.展开更多
基金Supported by the Open Project of Key Laboratory of Marine New Materials of CNITECH(No.LMMT-KFKT-2014-008)the National Basic Research Program of China(973 Program)(No.2014CB643304)
文摘Defects in protective-coating systems on steel surfaces are inevitable in practical engineering applications. A composite coating system, including a primer, middle coat and topcoat, were used to protect carbon steel from corrosion in a marine environment. Two environmental additives, glass fibers and thiourea, were applied in the middle coat to modify the coating system. The long-term corrosion durability and self-healing ability of the scratched coating system were evaluated by multiple methods. Results of the electrochemical technologies indicated that the coating system that contained 0.5 wt.% fibers and 0.5 wt.% thiourea presented good corrosion protection and self-healing for carbon steel when immersed in 3.5% NaCl for 120 d. Evolution of localized corrosion factors with time, as obtained from the current distribution showed that fibers combined with thiourea could inhibit the occurrence of local corrosion in scratched coating systems and retarded the corrosion development significantly. Surface characterization suggested that adequate thiourea could be absorbed tmiformly on fibers for a long time to play an important role in protecting the carbon steel. Finally, schematic models were established to demonstrate the action of fibers and thiourea on the exposed surface of the carbon steel and the scratched coating system in the entire deterioration process.
基金supported by the National Natural Science Foundation of China(Grant Nos.12272326,12102073,HWG2022001)the China Postdoctoral Science Foundation(Grant Nos.2024M763860 and 2024M763861).
文摘Scratch damage can reduce both the aesthetic appearance and structural integrity of polymer surfaces.To optimize and enhance the scratch resistance of polycarbonate,this study investigates the influence of assembly pre-tensile and pre-compressive stresses,with scratch experiments being conducted under both linearly increasing and constant normal load modes.Experimental results and finite element simulations are used to analyze scratch resistance and visibility.The results indicate that the application of 20%pre-compressive stress increases the critical normal load for onset of scratch visibility by 42%compared with the case in which no assembly pre-stress is applied,and it effectively decreases residual scratch depth,shoulder height,shoulder width,and tangential load.This is because assembly pre-compressive stress can effectively counteract the extrusion of material at the front and sides caused by the sliding scratch tip.Pre-compressive stress hinders scratch groove formation,improving the scratch resistance of polycarbonate.By contrast,pre-tensile stress weakens these characteristics.This study provides valuable insights for enhancing the surface damage resistance of polycarbonate materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.12072324 and 11702253)the Natural Science Foundation of Henan Province for Excellent Young Scholars(Grant No.212300410087).
文摘Correlations between the mechanical properties and surface scratch resistance of polylactic acid(PLA)are investigated via tensile and scratch tests on samples after degradation in soil for various times.The results show that the tensile yield strength of PLA is inversely proportional to the natural logarithm of the degradation time,and the scratch resistance and fracture toughness of PLA and the temperature rise near the indenter all increase and then decrease.The surface crystallinity of PLA also increases and then decreases,indicating that it and the scratch resistance are closely related.These findings provide useful information about how PLA behaves under degradation conditions.
文摘Chronic long-segment iliac artery occlusion represents a relatively rare and particularly severe form of iliac artery disease,often associated with complex anatomical challenges.When symptomatic,these patients are typically candidates for surgical revascularization.
基金Supported by National Key Research and Development Program of China(Grant No.2022YFB3403600)the National Natural Science Foundation of China(Grant No.52305461)。
文摘The fused quartz hemispherical resonator is the core component of the hemispherical resonator gyroscope.It features a complex shape and is Made from a Material that is difficult to process.Scratches are easily introduced during grinding,potentially degrading the mass-stiffness-damping symmetry;however,the underlying mechanisms of this influence have not been fully understood.This paper aims to investigate the effects of scratch defects on the frequency splitting and quality factor of the hemispherical resonator.First,finite element models of the hemispherical resonator with scratches are established.Then,the effects of the mass-stiffness factor,as well as the latitude and length of the scratches,on frequency splitting are analyzed.Furthermore,the impacts of latitude,length,and the first four harmonics of the unbalanced mass caused by scratches on thermoelastic damping and anchor loss are examined.Simulation results indicate that scratches above 55°latitude cause frequency splitting solely due to stiffness changes.Frequency splitting caused by scratches of the same size on the inherent rigidity shaft at the rim is approximately 50%of that near the transition fillet.Frequency splitting varies linearly with the volume of material removed by scratches.Scratches have little effect on thermoelastic damping.The first three harmonics of the unbalanced mass due to scratches at the rim are the primary contributors to anchor loss.Finally,focused ion beam trimming experiments are conducted at different locations on the hemispherical resonator.The trends observed in the experimental results are consistent with the simulation results.This work provides guidance for evaluating the impact of scratches on the performance of hemispherical resonators and for developing appropriate trimming processes.
