Open AccessFinite element modeling of acoustic field induced by laser line source near surface defect
Author(s) -
Yifei Shi,
Zhonghua Shen,
Xiaowu Ni,
Jian Lü,
Jiancheng Guan
Publication year - 2007
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.15.005512
Subject(s) - optics , line source , laser , transverse plane , materials science , directivity , pulse (music) , finite element method , acoustics , displacement (psychology) , near and far field , physics , psychology , telecommunications , structural engineering , detector , computer science , antenna (radio) , psychotherapist , thermodynamics , engineering
A numerical model of acoustic field induced by laser line source near the surface defect is established by finite element method (FEM), where a surface notch of rectangular shape has been introduced to represent the fatigue defect for the convenience of modeling. After calculating numerically the transient displacement distributions, which are generated by the laser irradiation, the ultrasonic wave modes on the surface and in the body of the plate material are presented in details. The longitudinal, transverse and surface acoustic waves (SAWs) excited by laser pulses near surface notch are compared under the situations that the notch depths are different. As the notch depth increases, the directivity of the bulk waves generation changes greatly. The amplitude of the reflected SAW rises observably at the same time, which is observed experimentally when the laser source is shifted near the surface notch in scanning laser line source (SLLS) measurement. Another effect induced by the surface notch is the time lag of the transmitted SAW pulse with respect to the original incident pulse. These phenomena can be explained from the results. The conclusions can be used to surface notch depth evaluation.