Incorporation of a spatial source distribution and a spatial sensor sensitivity in a laser ultrasound propagation model using a streamlined Huygensʼ principle

Laloš, Jernej (author), Babnik, Aleš (author), Možina, Janez (author), Požar, Tomaž (author)

The near-field, surface-displacement waveforms in plates are modeled using interwoven concepts of Greenʼs function formalism and streamlined Huygensʼ principle. Greenʼs functions resemble the building blocks of the sought displacement waveform, superimposed and weighted according to the simplified distribution. The approach incorporates an arbitrary circular spatial source distribution and an arbitrary circular spatial sensitivity in the area probed by the sensor. The displacement histories for uniform, Gaussian and annular normal-force source distributions and the uniform spatial sensor sensitivity are calculated, and the corresponding weight distributions are compared. To demonstrate the applicability of the developed scheme, measurements of laser ultrasound induced solely by the radiation pressure are compared with the calculated waveforms. The ultrasound is induced by laser pulse reflection from the mirror-surface of a glass plate. The measurements show excellent agreement not only with respect to various wave-arrivals but also in the shape of each arrival. Their shape depends on the beam profile of the excitation laser pulse and its corresponding spatial normal-force distribution.

• Language: English
• Keywords: Greenʼs function, laser ultrasonics, optodynamics, radiation pressure, wave propagation
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: In print
• Publication version: Author Accepted Manuscript
• Year: 2016
• Number of pages: Str. 34-42
• Numbering: Vol. 66
• PID: 20.500.12556/RUL-105464
• UDC: 535(045)
• ISSN on article: 0041-624X
• DOI: 10.1016/j.ultras.2015.12.002
• COBISS.SI-ID: 14391835
• Publication date in RUL: 30.11.2018

Record is a part of a journal

• Title: Ultrasonics
• Shortened title: Ultrasonics
• Publisher: Butterworth Scientific
• ISSN: 0041-624X
• COBISS.SI-ID: 26569728

Secondary language

• Language: Slovenian
• Title: Vključitev prostorske porazdelitve vira in prostorske občutljivosti senzorja v širitvenem modelu laserskega ultrazvoka z uporaba dopolnjenega Huygensovega načela

Abstract

Valovne oblike pomikov površine plošč smo v bližnjem polju modelirali z uporabo prepletenih konceptov formalizma Greenovih funkcij ter dopolnjenega Huygensovega načela. Greenove funkcije, ki ustrezajo gradnikom iskanih valovnih oblik, so pri tem ustrezno utežene in superponirane glede na njihovo poenostavljeno porazdelitev. Ta pristop vključuje poljubno krožno prostorsko porazdelitev vira in poljubno krožno prostorsko občutljivost senzorja na merilnem območju. Izračunali smo valovne oblike za enakomerno, Gaussovo in kolobarno porazdelitev vira ter za enakomerno občutljivost senzorja, pri čemer smo ustrezne utežene porazdelitve med seboj primerjali. Kot demonstracija uporabnosti razvitega modela smo izračunane valovne oblike primerjali z meritvami laserskega ultrazvoka induciranega zgolj s sevalnim tlakom. Ultrazvok je bil sprožen z laserskim bliskom, ki se je odbil od zrcalne površine steklene plošče. Meritve kažejo na odlično ujemanje z modelom tako pri časih prihoda posameznih valov kot tudi pri njihovih oblikah. Slednje so odvisne od časovnega poteka vpadlega laserskega bliska ter od njegove prostorske porazdelitve.

• Keywords: Greenove funkcije, laserski ultrazvok, optodinamika, sevalni tlak, širjenje valovanja, modeliranje ultrazvoka

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: P2-0392
• Name: Optodinamika