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| 1 | Effects of aging treatment on microstructure and mechanical properties of Cr25Ni35Nb and Cr35Ni45Nb furnace tube steel显示文摘Cr25Ni35Nb and Cr35Ni45Nb alloys are usually used in the ethylene cracking furnaces.However,premature failure of furnace tubes often occurs ahead of design life due to elevated temperature exposure conditions (1050-1100 ℃) and aggressive service environment.Effects of exposure temperature and time on microstructure and mechanical properties of Cr25Ni35Nb and Cr35Ni45Nb steel at aging temperature (1200 ℃) with various exposure time were simulated different service times at 1050 ℃.Change of mechanical properties at room temperature and elevated temperature (900 ℃) of the aged Cr25Ni35Nb and Cr35Ni45Nb steel were investigated.Under exposure at 1200 ℃,ultimate tensile and yield strength,elongation of Cr35Ni45Nb steel increase initially and then decrease,however,strength and ductility of Cr25Ni35Nb steel decrease with aging time increasing.Large amount of fine secondary carbide particles precipitated and dispersed in matrix of Cr35Ni45Nb steel,which increased strength and ductility for dispersion strengthening.However,the effect of the dispersion strengthening is weakened by needle-like secondary carbides.Strength and ductility decreased with fine secondary carbide particles growing.For Cr25Ni35Nb steel,few fine secondary carbide particles precipitated and dispersed in the matrix,and needle-like secondary carbides generated in the matrix,which causes strength and ductility decreased with aging time increasing. | Limin SHEN Jianming GONG Yong JIANG Luyang GENG | 2011 | Acta Metallurgica Sinica(English Letters)2011，24，3： | 8 |
| 2 | Damage prediction of HP40Nb steel with coupled creep and carburization based on the continuum damage mechanics显示文摘HP40Nb steel,used as a candidate material for ethylene cracking furnace tube,suffers creep and carburization damage from the complex environment of high temperature,high carbon potential and low oxygen partial pressure,and they lead to failure of the furnace tubes ahead of designed life.In order to investigate damage evolution under the complex condition,coupled creep damage and carburization damage constitutive equations were developed according to continuum damage mechanics theory.Based on the finite element ABAQUS code,user subroutines were developed for analyzing damage evolution of ethylene furnace tube under the action of coupled creepcarburization.The results show that carburization accelerates the damage process dramatically,damage value reaches the critical value along the inner surface after serving for 75,000 h under the action of creep-carburization,meanwhile the damage value is only 0.53 along the outer surface after operating the same time under the action of creep alone,which means that microcracks are generated along the inner surface under the action of coupled creep-carburization,fracture begins along the outer surface of tube under the action of creep alone. | Limin SHEN Jianming GONG Yong JIANG Luyang GENG | 2012 | Acta Metallurgica Sinica(English Letters)2012，25，4： | 1 |
| 3 | Fabrication and properties of high quality InGaN-based LEDs with highly reflective nanoporous GaN mirrors显示文摘Distributed Bragg reflectors (DBRs) are essential components for the development of optoelectronic devices.In this paper, we first report the use of the nanoporous GaN (NP-GaN) DBR as a template for regrowth of InGaN-based light-emitting diodes (LEDs). The wafer-scale NP-GaN DBR, which is fabricated by electrochemical etching in a neutral solution, has a smooth surface, high reflectivity (>99.5%), and wide spectral stop band width (>70 nm). The chemical composition of the regrown LED thin film is similar to that of the reference LED, but the photoluminescence (PL) lifetime, PL intensity, and electroluminescence intensity of the LED with the DBR are enhanced several times compared to those of the reference LED. The intensity enhancement is attributed to the light reflection effect of the NP-GaN DBR and improved crystalline quality as a result of the etching scheme, whereas the enhancement of PL lifetime is attributable to the latter. | DEZHONG CAO XIAOKUN YANG LUYANG SHEN CHONGCHONG ZHAO CAINA LUAN JIN MA HONGDI XIAO | 2018 | Photonics Research2018，6，12： | 0 |
| 4 | Continual learning fault diagnosis:A dual-branch adaptive aggregation residual network for fault diagnosis with machine increments显示文摘As a data-driven approach, Deep Learning(DL)-based fault diagnosis methods need to collect the relatively comprehensive data on machine fault types to achieve satisfactory performance. A mechanical system may include multiple submachines in the real-world. During condition monitoring of a mechanical system, fault data are distributed in a continuous flow of constantly generated information and new faults will inevitably occur in unconsidered submachines, which are also called machine increments. Therefore, adequately collecting fault data in advance is difficult. Limited by the characteristics of DL, training existing models directly with new fault data of new submachines leads to catastrophic forgetting of old tasks, while the cost of collecting all known data to retrain the models is excessively high. DL-based fault diagnosis methods cannot learn continually and adaptively in dynamic environments. A new Continual Learning Fault Diagnosis method(CLFD) is proposed in this paper to solve a series of fault diagnosis tasks with machine increments. The stability–plasticity dilemma is an intrinsic issue in continual learning. The core of CLFD is the proposed Dual-branch Adaptive Aggregation Residual Network(DAARN).Two types of residual blocks are created in each block layer of DAARN: steady and dynamic blocks. The stability–plasticity dilemma is solved by assigning them with adaptive aggregation weights to balance stability and plasticity, and a bi-level optimization program is used to optimize adaptive aggregation weights and model parameters. In addition, a feature-level knowledge distillation loss function is proposed to further overcome catastrophic forgetting. CLFD is then applied to the fault diagnosis case with machine increments. Results demonstrate that CLFD outperforms other continual learning methods and has satisfactory robustness. | Bojian CHEN Changqing SHEN Juanjuan SHI Lin KONG Luyang TAN Dong WANG Zhongkui ZHU | 2023 | Chinese Journal of Aeronautics2023，36，6： | 0 |
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