In this paper,acoustic emission（AE） and digital image correlation methods were applied to monitor interface cracking in thermal barrier coatings under compression.The interface failure process can be identifie via i...In this paper,acoustic emission（AE） and digital image correlation methods were applied to monitor interface cracking in thermal barrier coatings under compression.The interface failure process can be identifie via its AE features,including buckling,delamination incubation and spallation.According to the Fourier transformation of AE signals,there arefourdifferentfailuremodes：surfaceverticalcracks,opening and sliding interface cracks,and substrate deformation.The characteristic frequency of AE signals from surface vertical cracks is 0.21 MHz,whilst that of the two types of interface cracks are 0.43 and 0.29 MHz,respectively.The energy released of the two types of interface cracks are 0.43 and 0.29 MHz,respectively.Based on the energy released from cracking and the AE signals,a relationship is established between the interface crack length and AE parameters,which is in good agreement with experimental results.展开更多
Layered epoxy/paper composites that exhibit excellent insulating characteristics under elevated electrification and temperature conditions are essential components for power system insulation.Yet,inevitable charge acc...Layered epoxy/paper composites that exhibit excellent insulating characteristics under elevated electrification and temperature conditions are essential components for power system insulation.Yet,inevitable charge accumulation occurs at hetero interfaces between layers due to interfacial polarisation and interface barrier effect,bringing about local electric field distortion and potential risk of partial discharge.A fundamental challenge is either to obtain accurate interface charge behaviours of in-service multi-layer insulating composites,or to construct verified simulating models for replacing experiments.Herein,a modified bipolar charge transport model to simulate interface charge behaviours in layered composites is proposed.With model parameters directly originated from equivalent experiments(e.g.conduction current measurement,thermally stimulated depolarisation current testing,and ultraviolet-visible spectroscopy)of epoxy/paper composites,the simulated temperature-dependent interface charge characteristics match well with pulsed electro-acoustic results.Furthermore,electrical thresholds can also be accurately calculated using such models(maximum deviation of 8.44%from experimental results),providing references for optimised insulation structural design.展开更多
By considering the interaction between Fowler-Nordheim tunneling injection theory and charge carriers transporting through the bulk, an electroluminescence model for organic single-layer diodes is presented. The expre...By considering the interaction between Fowler-Nordheim tunneling injection theory and charge carriers transporting through the bulk, an electroluminescence model for organic single-layer diodes is presented. The expressions of the recombination current density, recombination efficiency and conductivity of the diodes are provided, which elucidate the controlling role of the electric field on mobility and recombination zone. The equilibrium of two opposite charge carriers injection and the cen-tral position of recombination zone are two important preconditions for reducing the leakage current. Space-charge-limited current occurs only over a certain high bias, meanwhile, the quantity of injection carriers increases over the transport capacity of the bulk.展开更多
基金supported by the National Natural Science Foundation of China (Grants 11472237,11002122,51172192,and 11272275)
文摘In this paper,acoustic emission（AE） and digital image correlation methods were applied to monitor interface cracking in thermal barrier coatings under compression.The interface failure process can be identifie via its AE features,including buckling,delamination incubation and spallation.According to the Fourier transformation of AE signals,there arefourdifferentfailuremodes：surfaceverticalcracks,opening and sliding interface cracks,and substrate deformation.The characteristic frequency of AE signals from surface vertical cracks is 0.21 MHz,whilst that of the two types of interface cracks are 0.43 and 0.29 MHz,respectively.The energy released of the two types of interface cracks are 0.43 and 0.29 MHz,respectively.Based on the energy released from cracking and the AE signals,a relationship is established between the interface crack length and AE parameters,which is in good agreement with experimental results.
基金Science and Technology Project of State Grid Corporation of China,Grant/Award Number:SGLNDK00KJJS1900250。
文摘Layered epoxy/paper composites that exhibit excellent insulating characteristics under elevated electrification and temperature conditions are essential components for power system insulation.Yet,inevitable charge accumulation occurs at hetero interfaces between layers due to interfacial polarisation and interface barrier effect,bringing about local electric field distortion and potential risk of partial discharge.A fundamental challenge is either to obtain accurate interface charge behaviours of in-service multi-layer insulating composites,or to construct verified simulating models for replacing experiments.Herein,a modified bipolar charge transport model to simulate interface charge behaviours in layered composites is proposed.With model parameters directly originated from equivalent experiments(e.g.conduction current measurement,thermally stimulated depolarisation current testing,and ultraviolet-visible spectroscopy)of epoxy/paper composites,the simulated temperature-dependent interface charge characteristics match well with pulsed electro-acoustic results.Furthermore,electrical thresholds can also be accurately calculated using such models(maximum deviation of 8.44%from experimental results),providing references for optimised insulation structural design.
基金This work was financed by the National Natural Science Foundation of China (Grant Nos. 29992530 and 19974002) the Paper Foundation of Northern Jiaotong University.
文摘By considering the interaction between Fowler-Nordheim tunneling injection theory and charge carriers transporting through the bulk, an electroluminescence model for organic single-layer diodes is presented. The expressions of the recombination current density, recombination efficiency and conductivity of the diodes are provided, which elucidate the controlling role of the electric field on mobility and recombination zone. The equilibrium of two opposite charge carriers injection and the cen-tral position of recombination zone are two important preconditions for reducing the leakage current. Space-charge-limited current occurs only over a certain high bias, meanwhile, the quantity of injection carriers increases over the transport capacity of the bulk.
