Elektronsko i softversko rešenje kvadrofonske transmisione ultrazvučne defektoskopije u primeni na direktno laserski sinterovanim materijalima

Predmet ove doktorske disertacije predstavlja razvoj defektoskopa koji funkcioniše na principu nove ultrazvučne metode, nazvanoj kvadrofonska transmisiona ultrazvučna defektoskopska metoda (KTUD metoda), u primeni na direktno laserski sinterovanim materijalima (DLSM). Cilj rada je da pruži konkretan doprinos kontroli kvaliteta procesa proizvodnje DLSM proizvoda, predstavljanjem KTUD metode. Metoda omogućava jeftinu i efikasnu ultrazvučnu defektoskopiju elemenata proizvedenih DLSM postupkom. Ovim postupkom se izrađuju čvrsti, a ujedno lagani, porozni, šupljikavi elementi koji se primenjuju u tehnici orbitalnih satelita, tehnologiji najmodernijih motora i u avionskoj tehnici. Razvoj DLSM metode je pokušaj ispunjavanja zahteva za ekonomičnijom proizvodnjom malih serija mašinskih elemenata i sve kompleksnijih geometrija (kako spoljašnjih tako i unutrašnjih) metalnih elemenata. Trodimenzionalni element izgrađuje se na taj način što se dodaje jedan po jedan deo zapremine u obliku tankog sloja, čime nastaje porozan i šupljikav element, koji je čvrst i lak. Za razliku od indirektnog laserskog sinterovanja metala, DLSM se sastoji od samo jednog procesnog koraka što je prednost direktne metode jer se izbegava problematična procedura očvršćavanja u peći

Defectoscopy of direct laser sintered metals by low transmission ultrasonic frequencies

This paper focuses on the improvement of ultrasonic defectoscopy used for machine elements produced by direct laser metal sintering. The direct laser metal sintering process introduces the mixed metal powder and performs its subsequent laser consolidation in a single production step. Mechanical elements manufactured by laser sintering often contain many hollow cells due to weight reduction. The popular pulse echo defectoscopy method employing very high frequencies of several GHz is not successful on these samples. The aim of this paper is to present quadraphonic transmission ultrasound defectoscopy which uses low range frequencies of few tens of kHz. Therefore, the advantage of this method is that it enables defectoscopy for honeycombed materials manufactured by direct laser sintering. This paper presents the results of testing performed on AlSi12 sample. [Projekat Ministarstva nauke Republike Srbije, br. OI 172057

A novel ultrasonic technique for material testing

The material defectoscopy method that uses separate ultrasonic heads for emitting and reception of signals, i.e. ultrasonic transmission defectoscopy, hasn't been in use in science and engineering that much until now. This method consists of an ultrasonic head for emitting the signal and a single ultrasonic head for the reception of the signal. The method described in this paper is named "Quadrophonic Transmission Ultrasonic Defectoscopy" (QTUD). It is an ultrasonic defectoscopy method for material testing that uses a single ultrasonic head for emitting and four ultrasonic heads for receiving the ultrasonic signal. The prime advantage of the QTUD method is its real life applicability even with porous materials, and the basis for the method on relatively low frequencies (only a few tens of kHz). Because electronic components are very cheap to acquire, therefore, the wide application of this method, both in science and industry, is very likely

A novel ultrasonic technique for material testing

The material defectoscopy method that uses separate ultrasonic heads for emitting and reception of signals, i.e. ultrasonic transmission defectoscopy, hasn't been in use in science and engineering that much until now. This method consists of an ultrasonic head for emitting the signal and a single ultrasonic head for the reception of the signal. The method described in this paper is named "Quadrophonic Transmission Ultrasonic Defectoscopy" (QTUD). It is an ultrasonic defectoscopy method for material testing that uses a single ultrasonic head for emitting and four ultrasonic heads for receiving the ultrasonic signal. The prime advantage of the QTUD method is its real life applicability even with porous materials, and the basis for the method on relatively low frequencies (only a few tens of kHz). Because electronic components are very cheap to acquire, therefore, the wide application of this method, both in science and industry, is very likely

Low Frequencies for Cardboard Quality Assurance

During the ultrasound defectoscopy the ultrasound absorption factor inside the material is raised to the fourth power of frequency. In conjunction with the previously stated, the attenuation of the sound signal which is caused by the reflections of the sound inside the sample, the application of high frequency ultrasound in porous and hollow materials is very limited or even impossible. The frequencies are the reason for this, because they are in the range of just several megahertz, which are currently the main trend in the ultrasound examination. This paper presents a principle of this new method, including the experimental results from its application on the typical represent of product packaging material. Also, it is shown that the expressed absorption of ultrasound waves from porous and hollow structures can be avoided by applying the method with such low frequencies