The orthotropic bimaterial antiplane interface end of a flat lap is studied by constructing new stress functions and using the composite complex function method of material fracture. The expressions of stress fields, ...The orthotropic bimaterial antiplane interface end of a flat lap is studied by constructing new stress functions and using the composite complex function method of material fracture. The expressions of stress fields, displacements fields and the stress intensity factor around the flat lap interface end are derived by solving a class of generalized bi-harmonic equations. The result shows that this type of problem has one singularity, the stress field has no singularity when two materials have constant ratio F 〉 0, the stress field has power singularity, and the singularity index has a trend to -1/2 as F increases. The derived equation is verified with FEM analysis.展开更多
The improvement of the signal to noise ratio （SNR） has significant meaning to the fiber Bragg grating （FBG） sensing system. The source of the noise as well as the signal attenuation of the FBG sensing system is an...The improvement of the signal to noise ratio （SNR） has significant meaning to the fiber Bragg grating （FBG） sensing system. The source of the noise as well as the signal attenuation of the FBG sensing system is analyzed. It is found that optical noise caused by the optical return loss （ORL） is the main source of noises in the system, and the coupler is the main source of attenuation of the signal. The cause of the ORL in fiber-optic elements （such as jumper cables connector and fiber end） is presented. In addition, suggestions to optimize the fiber optical sensing network in order to improve the SNR are presented. Methods to suppress noises caused by the fiber end interfaces of FBGs, including using index-matching fluid, bending fiber p!gtails in the way mentioned in this paper and cleaving the slant angle of the fiber interfaces to be 8, all contribute to the optimized SNR. Besides, the thermo-weld method is suggested to be used for both parallel and serial FBG setups to provide a low insertion loss. The results would be a useful engineering tool to design the high SNR optical sensing system.展开更多
基金supported by the Natural Science Foundation of Shanxi Province (No. 2007011008)
文摘The orthotropic bimaterial antiplane interface end of a flat lap is studied by constructing new stress functions and using the composite complex function method of material fracture. The expressions of stress fields, displacements fields and the stress intensity factor around the flat lap interface end are derived by solving a class of generalized bi-harmonic equations. The result shows that this type of problem has one singularity, the stress field has no singularity when two materials have constant ratio F 〉 0, the stress field has power singularity, and the singularity index has a trend to -1/2 as F increases. The derived equation is verified with FEM analysis.
文摘The improvement of the signal to noise ratio （SNR） has significant meaning to the fiber Bragg grating （FBG） sensing system. The source of the noise as well as the signal attenuation of the FBG sensing system is analyzed. It is found that optical noise caused by the optical return loss （ORL） is the main source of noises in the system, and the coupler is the main source of attenuation of the signal. The cause of the ORL in fiber-optic elements （such as jumper cables connector and fiber end） is presented. In addition, suggestions to optimize the fiber optical sensing network in order to improve the SNR are presented. Methods to suppress noises caused by the fiber end interfaces of FBGs, including using index-matching fluid, bending fiber p!gtails in the way mentioned in this paper and cleaving the slant angle of the fiber interfaces to be 8, all contribute to the optimized SNR. Besides, the thermo-weld method is suggested to be used for both parallel and serial FBG setups to provide a low insertion loss. The results would be a useful engineering tool to design the high SNR optical sensing system.
