Laser shock processing is a recently developed surface treatment designed to improve the mechanical properties and fatigue performance of materials, by inducing a deep compressive residual stress field. The purpose of this work is to investigate the residual stress distribution induced by laser shock processing in a 2050-T8 aeronautical aluminium alloy with both X-ray diffraction measurements and 3D finite element simulation. The method of X-ray diffraction is extensively used to characterize the crystallographic texture and the residual stress crystalline materials at different scales (macroscopic, mesoscopic and microscopic).Shock loading and materials’ dynamic response are experimentally analysed using Doppler velocimetry in order to use adequate data for the simulation. Then systematic experience versus simulation comparisons are addressed, considering first a single impact loading, and in a second step the laser shock processing treatment of an extended area, with a specific focus on impact overlap. Experimental and numerical results indicate a residual stress anisotropy, and a better surface stress homogeneity with an increase of impact overlap.A correct agreement is globally shown between experimental and simulated residual stress values, even if simulations provide us with local stress values whereas X-ray diffraction determinations give averaged residual stresses.International audienceLaser shock processing is a recently developed surface treatment designed to improve the mechanical properties and fatigue performance of materials, by inducing a deep compressive residual stress field. The purpose of this work is to investigate the residual stress distribution induced by laser shock processing in a 2050-T8 aeronautical aluminium alloy with both X-ray diffraction measurements and 3D finite element simulation. The method of X-ray diffraction is extensively used to characterize the crystallographic texture and the residual stress crystalline materials at different scales (macroscopic, mesoscopic and microscopic).Shock loading and materials’ dynamic response are experimentally analysed using Doppler velocimetry in order to use adequate data for the simulation. Then systematic experience versus simulation comparisons are addressed, considering first a single impact loading, and in a second step the laser shock processing treatment of an extended area, with a specific focus on impact overlap. Experimental and numerical results indicate a residual stress anisotropy, and a better surface stress homogeneity with an increase of impact overlap.A correct agreement is globally shown between experimental and simulated residual stress values, even if simulations provide us with local stress values whereas X-ray diffraction determinations give averaged residual stresses
Based on the optical pulse correlation measurement and differential detection technique, an optical fibre sensor with high time resolution has been developed. However, due to the birefringence in single mode fibre induced by the uneven thermal effect, polarization fluctuation in the correlation signal was observed. In order to suppress the polarization fluctuation in the correlation sensing system, a polarization-suppressed optical correlation sensing system is proposed by utilizing the birefringence compensation approach in a retraced fibre path using Faraday rotator mirror elements. The polarization fluctuation of the output correlation signals is suppressed by more than 15 dB. The results of temperature experiment indicate that the linearity between the temperature and differential signal is further improved. With the reflection of the mirror, a double-pass monitoring is established, which significantly enhances the sensitivities of the sensing system to temperature and strain.
A novel fibre optic sensing system with a high time resolution of less than 0.04 ps based on an optical pulse correlation measurement mechanism and differential detection technique is investigated. The optical pulse correlation state corresponding to time drift in fibre optic transmission lines is detected by SHG. The results of temperature and strain sensing experiments demonstrate an excellent linear relationship between the differential signal and the measurands inducing time drift of the optical pulse through a fibre optic. Based on the sensing system, a temperature resolution of 0.04 m • C and a strain resolution of 0.2 µε are obtained, respectively, which indicate that the sensing system can be successfully applied to monitor the environment conditions around fibre optic transmission lines with high resolution.
A quantitative analysis is conducted on the impacts of experimental imperfections in the input state, the detector properties, and their interactions on photon-subtracted squeezed vacuum states in terms of a quantum non-Gaussian character witness and Wigner function. Limitations of the nonclassicality and quantum non-Gaussian characteristic of Schrödinger kitten states are identified and addressed. The detrimental effects of a photon-number detector on the generation of odd Schrödinger kitten states at near-infrared wavelengths (∼860 nm) and telecommunication wavelengths (∼1550 nm) are presented and analysed. This analysis demonstrates that the high dark count probability of telecommunication-wavelength photon-number detectors significantly undermines the negativity of the Wigner function in Schrödinger kitten state generation experiments. For a one-photon-subtracted squeezed vacuum state at ∼1550 nm, an avalanche photodiode-based photon-numberresolving detector provides no significant advantage over a non-photon-numberresolving detector when imperfections, such as dark count probability and inefficiency, are taken into account.
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