Ultrasound tiam

Tus" super" tus cwj pwm ntawm ultrasound los ntawm qhov tseeb tias qhov qis dua ntawm nws cov zaus band tshaj tib neeg hnov, tab sis yog tias koj txheeb xyuas nws nyob rau hauv cov nqe lus ntawm wavelength, lub wavelength ntawm ultrasound yog luv luv. Cov kws tshawb fawb hu qhov kev ncua deb ntawm ob lub ncov uas nyob ib sab los yog troughs ntawm nthwv dej li wavelength. Lub wavelength ntawm mechanical waves uas peb tib neeg pob ntseg hnov ​​tau yog 2cm ~ 20m (2cm ~ 20m). Yog li ntawd, peb hu cov tshuab tsis muaj zog nrog lub wavelength luv dua 2 cm li" ultrasound." Txawm li cas los xij, hauv kev siv tswv yim, cov tshuab tsis muaj zog nrog lub wavelength hauv qab 3.4cm (siab dua 10000hz) tuaj yeem suav tias yog kev tshawb fawb ultrasonic. Lub wavelength ntawm ultrasound feem ntau siv rau kev kuaj mob yog 10μm ~ 350μm.

Ultrasound yog ib hom kev kho tshuab yoj. Nws yuav tsum cia siab rau qhov nruab nrab kom nthuav tawm thiab tsis tuaj yeem nyob hauv lub tshuab nqus tsev (xws li qhov chaw). Yog li ntawd, peb tsis tuaj yeem siv ultrasound hauv lub tshuab nqus tsev, tab sis peb tseem tuaj yeem siv cov khoom siv hluav taws xob ntsig txog nthwv dej (xws li xov tooj cua, microwaves, thiab infrared rays). , pom lub teeb, ultraviolet rays, X-rays, gamma rays, thiab lwm yam), siv electromagnetic yoj tshuab.

Nyob rau hauv cov huab cua, ultrasonic tsis xa mus rau cov neeg kho tshuab tsis muaj wavelength tsawg tshaj li 2 cm (piv txwv li, 1.7 cm, 2 cm wavelength sib raug rau 17000 Hz, 1.7 cm wavelength sib raug rau 20000 Hz, qhov tseeb, tsis muaj tus qauv ruaj khov, tsuas yog tus nqi uas yooj yim rau nco), thiab nws lub wavelength yog luv heev. Tsawg dua qhov kev txwv qis ntawm tib neeg hnov ​​​​lus (2cm), tib neeg hu qhov tsis hnov ​​​​tsw ntawm lub tshuab yoj ultrasound, thiab lub wavelength ntawm infrasound wavelength feem ntau ntev dua 20 meters (piv txwv li, 17 meters, 20m wavelength sib haum mus rau 17Hz, 17m wavelength sib haum rau 20Hz), siab tshaj Qhov siab tshaj qhov txwv ntawm lub suab ntawm lub suab. Hauv kev siv tswv yim, ultrasonic nthwv dej feem ntau coincide nrog ntau yam ntawm luv-yoj audible suab nthwv dej, thiab cov neeg kho tshuab nthwv dej nrog lub wavelength luv dua 3.4cm (10000hz) tuaj yeem suav tias yog kev tshawb fawb ultrasonic.

Nws lub wavelength luv luv dua li cov suab tsis zoo ib yam, yog li nws tuaj yeem siv rau kev txiav, vuam, drilling, thiab lwm yam. Vim nws qhov luv wavelength, nws muaj ntau yam ntxwv: thawj zaug, kev nthuav tawm anisotropy tshwm sim los ntawm luv wavelength, thiab kuj yog vim li cas. nws luv wavelength thiab tsis muaj peev xwm diffraction. Txawm hais tias nws muaj anisotropy zoo, nws muaj qhov poob loj hauv huab cua thiab tsis tuaj yeem kis tau. Nyob deb, tsis zoo nkag mus, yooj yim tawg. Ultrasound feem ntau yog siv hauv kev lag luam thiab tshuaj rau kev kuaj xyuas ultrasonic. Ultrasound, infrasound, thiab audible suab yog qhov tseem ceeb tib yam. Dab tsi lawv muaj nyob rau hauv ntau yog ib tug neeg kho tshuab yoj, uas feem ntau propagates nyob rau hauv elastic media nyob rau hauv daim ntawv ntawm longitudinal tsis. Nws yog ib daim ntawv ntawm lub zog propagation. Qhov txawv yog ultrasonic tsis. Ntev thiab luv, nws tuaj yeem taug kev raws txoj kab ncaj nraim hauv ib qho kev ncua deb nrog me ntsis diffraction, thiab muaj anisotropy zoo. Txawm li cas los xij, piv nrog lub suab nrov thiab infrasound, nws muaj lub zog nkag mus tsis zoo thiab yooj yim tawg.

Cov kev cai propagation ntawm kev xav, refraction, diffraction, thiab tawg ntawm ultrasonic nthwv dej nyob rau hauv nruab nrab yog tsis tseem ceeb txawv los ntawm cov kev cai ntawm infrasound thiab audible suab tsis. Tab sis lub wavelength ntawm ultrasound yog luv heev, tsuas yog ob peb centimeters, txawm ob peb txhiab ntawm ib millimeters. Piv nrog rau lwm cov nthwv dej, ultrasonic nthwv dej muaj ntau yam ntxwv: kev nthuav tawm cov yam ntxwv - lub wavelength ntawm ultrasonic tsis yog luv heev, thiab qhov loj ntawm cov teeb meem zoo tib yam yog ntau zaus ntau dua qhov wavelength ntawm ultrasonic tsis. Yog li ntawd, ultrasonic tsis muaj kev nkag mus tsis zoo, muaj peev xwm tsis zoo, thiab tawg yooj yim. . Nws tuaj yeem nthuav tawm hauv txoj kab ncaj nraim hauv qhov nruab nrab homogeneous tab sis nyuaj rau kev sib txawv. Qhov luv luv lub wavelength ntawm ultrasonic yoj, qhov pom tseeb dua tus yam ntxwv. Tsis tas li ntawd, raws li Rayleigh scattering txoj cai, qhov kev siv ntawm cov yoj tawg ntho yog inversely proportional rau plaub lub zog ntawm lub wavelength, thiab lub wavelength ntawm ultrasonic yoj yog luv heev. , Yog li qhov tawg yog qhov hnyav heev thiab lub zog nkag mus tsis zoo. Cavitation ─ ─ Thaum lub ultrasonic yoj propagates nyob rau hauv nruab nrab, muaj ib tug zoo thiab tsis zoo alternating lub sij hawm. Nyob rau hauv lub zoo theem, lub ultrasonic yoj nyem qhov nruab nrab molecules hloov lub qub ntom ntawm nruab nrab thiab nce nws; nyob rau hauv lub siab tsis zoo theem Thaum lub nruab nrab molecules yog sparse thiab ntxiv dispersed, qhov ceev ntawm nruab nrab yog txo. Thaum muaj zog txaus ultrasonic yoj siv rau cov kua nruab nrab, qhov nruab nrab ntawm qhov nruab nrab molecules yuav tshaj qhov tseem ceeb molecular nrug uas ua rau cov kua nruab nrab tsis tu ncua. Fracture tshwm sim thiab microbubbles tsim. Cov kab noj hniav me me no nthuav dav thiab kaw nrawm, ua rau muaj kev sib tsoo ntawm cov kua ua kua, ua rau muaj kev kub ntxhov ntawm ntau txhiab mus rau kaum tawm txhiab tus cua. Qhov kev sib cuam tshuam hnyav ntawm cov khoom no muaj cov txiaj ntsig zoo, kom ob qho dej tsis sib haum xeeb (xws li dej thiab roj) emulsify thiab ua kom cov kua dej ua kom nrawm dua. Ntau yam teebmeem tshwm sim los ntawm qhov kev txiav txim ntawm ultrasonic tsis nyob rau hauv cov kua yog hu ua ultrasonic cavitation.