The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
C.k. Lee - One of the best experts on this subject based on the ideXlab platform.
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structure electrochemical and wear corrosion properties of electroless nickel phosphorus deposition on cfrp composites
Materials Chemistry and Physics, 2009Co-Authors: C.k. LeeAbstract:Abstract This work evaluates the Microstructure, and mechanical, elcetrochemical and wear-corrosion properties of electroless nickel–phosphorus (ENP) coatings on carbon-fiber-reinforced plastic (CFRP) composites commonly used in aeronautical and astronautical applications due to their superior properties such as high specific strength and modulus. Experimental results demonstrate that a uniform ENP coating was successfully deposited on a CFRP substrate via electroless plating after appropriate sensitization, activation and mechanical polishing pre-treatments of the CFRP substrate exhibited excellent protection from corrosion and wear corrosion for CFRP composites. The Microstructure, phosphorus content, thickness and electrochemical and wear-corrosion properties of the ENP coatings were strongly correlated with the pre-polishing condition (the corresponding surface roughness) of the CFRP substrate. High P content (P > 7 wt.%), low Micro-Porosity, smooth morphology, high thickness and hardness of ENP coatings on the CFRP substrate were obtained when substrate surface roughness was ≥0.3 μm (grinding with 800-grade emery paper). The resulting electrochemical behavior exhibited a strong passivity that is favorable to enhanced wear-corrosion resistance properties.
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Corrosion and wear-corrosion resistance properties of electroless Ni–P coatings on GFRP composite in wind turbine blades
Surface and Coatings Technology, 2008Co-Authors: C.k. LeeAbstract:Abstract Electroless nickel (EN) coatings with phosphorus are preferred in many industries such as the oil, chemical, plastic, mechanical, and electronic industries because of their excellent corrosion and wear resistance. This work evaluates the corrosion and wear-corrosion resistance of electroless nickel–phosphorus (ENP) coatings on glass fiber-reinforced plastic (GFRP) composites that are frequently used in wind turbine blades. The results demonstrated that the Micro-Porosity, phosphorus content, thickness and corrosion and wear-corrosion properties of ENP coatings on the GFRP substrate were all strongly related to the grinding pre-treatment condition, meaning the corresponding surface roughness state of the substrate. A higher P content (P > 7 wt.%), lower Micro-Porosity, greater thickness and greater hardness of the ENP coatings on GFRP substrate were obtained as the surface roughness of the substrate increased over 0.3 µm (as it did upon grinding with emery paper of lower than 800-grade), improving corrosion and wear-corrosion resistance properties.
Alan D. Ziegler - One of the best experts on this subject based on the ideXlab platform.
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hydrophysical degradation associated with hiking trail use a case study of hawai iloa ridge trail o ahu hawai i
Land Degradation & Development, 2001Co-Authors: Ross A Sutherland, J. O. Bussen, D. L. Plondke, B. M. Evans, Alan D. ZieglerAbstract:Recreational activities can have significant impacts on geomorphic and hydrologic processes in drainage basins, often out of proportion to their areal extent. With increased stress on hiking trails nationwide, there is a need to characterize the impacts of human trampling on soil properties. We examine an 810 m segment of Hawai'iloa Ridge Trail (O'ahu, Hawai'i, USA). Soil compaction and surface erosion on moderate to steeply sloping sites have degraded the trail environment. Bulk density, penetration resistance, and vane shear strength were significantly higher on the trail than in adjacent undisturbed areas, with median differences ranging from 29 to 120 per cent. With compaction and exposure of subsoil on the trail, void ratio, air-filled Porosity, saturated hydraulic conductivity, effective and preferential Porosity were significantly lower, with relative change values ranging from 23–93 per cent. No significant changes were noted in meso- or Micro-Porosity, but macropores with a radius of >110 μm decreased significantly by 58 per cent for on-trail locations. This comprehensive dataset indicates that hiking stress is deleterious to the soil–hydrologic system. Data point to a trail system that would be dominated by Hortonian overland flow and this was supported by field evidence during a storm event. Increased runoff has incised rills on some trail segments and there is evidence that run-on to adjacent side slopes has lead to accelerated erosion. Management on most trails in Hawai'i, including the one studied, is limited, but from our data it is apparent that on-trail sites directly influenced by an overhanging canopy of rapidly growing (aggressive) exotics were least impacted due to increased organic contributions to the surface and root network development. These data will allow land managers to more effectively address the potential geomorphic and hydrologic impacts of recreational land use. Copyright © 2001 John Wiley & Sons, Ltd.
Zhengmao Yang - One of the best experts on this subject based on the ideXlab platform.
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investigation of long term thermal aging induced damage in oxide oxide ceramic matrix composites
Journal of The European Ceramic Society, 2020Co-Authors: Zhengmao Yang, Junjie YangAbstract:Abstract Long-term thermal aging is a typical factor affecting the thermo-mechanical fatigue life for hot-end components in the gas turbine. The present work focuses on the development of thermal aging-induced damage in 2-D woven oxide/oxide ceramic matrix composites from Micro-mechanism and macroscopic mechanical performance. The Porosity evolution and mechanical performance after long-term thermal aging were characterized through mercury intrusion measurements and uniaxial compressive tests, respectively. The results show that the decrease of Micro-Porosity directly reflects the irreversible evolution of material Microstructure in the thermal aging process, and the decrease of compressive strength after aging is the macroscopic reflection of the Microstructure variation. The Porosity increment of matrix was thus used to characterize the thermal aging-induced damage, establishing a unique analysis model between the increment of Micro-Porosity under thermal aging and the corresponding degradation of material compressive strength. The experimental results are in good agreement with the established model.
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Micro Porosity as damage indicator for characterizing cyclic thermal shock induced anisotropic damage in oxide oxide ceramic matrix composites
Engineering Fracture Mechanics, 2019Co-Authors: Zhengmao Yang, Hui Liu, Huang YuanAbstract:Abstract Ceramic matrix composites display complex mechanical behavior under thermo-mechanical loading conditions. The present work focuses on Micro-structural evolution and resultant macroscopic property representation of the composites after cyclic thermal shocks. Micro-structural investigation reveals that variations of the hierarchical Porosity in the matrix characterize the collective behavior of Micro-structural evolution in the material. Cyclic thermal shocks induce thermo-mechanical damage and lead to increasing matrix Porosity. Material damage development is driven by elastic strain energy density which is related to the matrix Porosity increment. Experiments confirm that the anisotropic damage can be represented by the Porosity increment accurately. The Porosity provides a meaningful model for the thermal shock damage evolution in the anisotropic composites.
Haoping Peng - One of the best experts on this subject based on the ideXlab platform.
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the effect of tig welding techniques on Microstructure properties and Porosity of the welded joint of 2219 aluminum alloy
Journal of Alloys and Compounds, 2017Co-Authors: Jiasheng Zou, Junshan Yao, Haoping PengAbstract:Abstract 2219 aluminum alloy was mainly used in the propellant tanks of domestic aerospace vehicles. Porosity was often observed during the VPTIG welding joint of the 2219 aluminum alloy. The new welding technology under condition of direct current electrode negative A-TIG (DCEN A-TIG) welding using a special active agent (AlF 3 , LiF, KF-AlF 3 , K 2 SiF 6 ) had eliminated the welding Porosity of 2219 aluminum alloy. DCEN A-TIG welding and VPTIG welding of 2219 aluminum alloy were performed. Compared with VPTIG welding, the current decrease of DCEN A-TIG welding had greatly reduced thermal effect on base metal and heat-affected zone. The DCEN A-TIG technology had prevented welding Porosity, while VPTIG welding had contained numerous macro and Micro Porosity. The weakest part of the DCEN A-TIG welding joint was the fusion zone, however, the VPTIG joint mainly ruptured in the weld zone due to significant Porosity defect. The grain sizes of the welding zone in VPTIG welding were coarser than those in DCEN A-TIG welding, which can reach the same mechanical performance index with VPTIG welding.
Ross A Sutherland - One of the best experts on this subject based on the ideXlab platform.
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hydrophysical degradation associated with hiking trail use a case study of hawai iloa ridge trail o ahu hawai i
Land Degradation & Development, 2001Co-Authors: Ross A Sutherland, J. O. Bussen, D. L. Plondke, B. M. Evans, Alan D. ZieglerAbstract:Recreational activities can have significant impacts on geomorphic and hydrologic processes in drainage basins, often out of proportion to their areal extent. With increased stress on hiking trails nationwide, there is a need to characterize the impacts of human trampling on soil properties. We examine an 810 m segment of Hawai'iloa Ridge Trail (O'ahu, Hawai'i, USA). Soil compaction and surface erosion on moderate to steeply sloping sites have degraded the trail environment. Bulk density, penetration resistance, and vane shear strength were significantly higher on the trail than in adjacent undisturbed areas, with median differences ranging from 29 to 120 per cent. With compaction and exposure of subsoil on the trail, void ratio, air-filled Porosity, saturated hydraulic conductivity, effective and preferential Porosity were significantly lower, with relative change values ranging from 23–93 per cent. No significant changes were noted in meso- or Micro-Porosity, but macropores with a radius of >110 μm decreased significantly by 58 per cent for on-trail locations. This comprehensive dataset indicates that hiking stress is deleterious to the soil–hydrologic system. Data point to a trail system that would be dominated by Hortonian overland flow and this was supported by field evidence during a storm event. Increased runoff has incised rills on some trail segments and there is evidence that run-on to adjacent side slopes has lead to accelerated erosion. Management on most trails in Hawai'i, including the one studied, is limited, but from our data it is apparent that on-trail sites directly influenced by an overhanging canopy of rapidly growing (aggressive) exotics were least impacted due to increased organic contributions to the surface and root network development. These data will allow land managers to more effectively address the potential geomorphic and hydrologic impacts of recreational land use. Copyright © 2001 John Wiley & Sons, Ltd.