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Quality assessment of mineral wool insulation plates: Using ultrasonic non-destructive testing
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
2019 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In the manufacturing process of mineral wool insulation plates, defects arise, such as unmelted base minerals and uncured binder which gets embedded within the plates. To be able to sort out these defective plates from a manufacturing line, a reliable quality assessment is needed. The aim is to find an ultrasonic non-destructive testing method that can identify the embedded defects. This was achieved through experiments on defective insulation plates using three different ultrasonic non-destructive testing methods that were of interest. These methods were higher harmonics, pulse-echo and through transmission. Of these three, the through transmission method showed the most promising results in finding the defects that were sought after. The through transmission method utilizes two aligned transducers, one acting as a transmitter and one as a receiver. When the defective area passes through the sound beam between the transducers the intensity of the beam drops, indicating that a defect is present. The weakened intensity is due to the signal attenuation, mainly caused by the higher density of the defects compared to the base material in the surrounding insulation plate. The method is well suited for being implemented in a production line since it’s a fast method and, therefore, suited for moving objects. More measurements are needed to establish a reliable reference value to consistently distinguish the defects from the surrounding plate. The method was only evaluated in a small scale experimental environment so further experiments on a larger scale are needed to mimic and evaluate the reliability in the real case scenario of the production lines.

Abstract [sv]

I tillverkningsprocessen av isolerskivor i stenull uppstår inneboende defekter i isolerskivorna, dessa defekter består av osmälta basmineraler och ohärdat bindemedel. För att kunna sortera bort dessa skadade skivor från tillverkningslinjen behövs en pålitlig metod för kvalitetsbedömning. Avsikten med det här arbetet är att hitta en oförstörande provningsmetod baserad på ultraljud som kan identifiera de inneboende defekterna. Detta genomfördes genom experiment på defekta isolerskivor med tre olika oförstörande provningsmetoder baserade på ultraljud. Dessa metoderna var, higher harmonics, pitch-echo och through transmission. Through transmission visade lovande resultat i att identifiera de båda typerna av skador. Metoden är baserad på att en sändare sänder ut ultraljud till en mottagare placerad i linje med sändaren. När ett defekt område passerar ultraljudsvågen mellan sändaren och mottagaren försvagas intensiteten av signalen. Försvagningen av signalen beror mestadels på att densiteten är högre hos defekterna än hos basmaterialet i isolerskivan. Denna försvagning indikerar att en defekt befinner sig i mätområdet. Metoden är väl implementerbar i en tillverkningslinje, då det är en snabb metod vilket den behöver vara då objektet är i rörelse. Mer mätningar behövs för att fastställa ett pålitligt referensvärde för att konsekvent kunna sortera ut de defekta isolerskivorna. Metoden är endast utvärderad i en småskalig laborationsmiljö och det behövs fler tester i en större skala undersöka pålitligheten i det verkliga scenariot med tillverkningslinjen.

Place, publisher, year, edition, pages
2019. , p. 62
Keywords [en]
Non-destructive testing, linear ultrasound, mineral wool, fibrous materials, acoustics, frequency response, signal attenuation
Keywords [sv]
Oförstörande provning, linjärt ultraljud, stenull, fibrösa material, akustik, frekvenssvar, signalförsvagning
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:bth-18223OAI: oai:DiVA.org:bth-18223DiVA, id: diva2:1332002
External cooperation
Acoustic Agree AB
Subject / course
Degree Project in Master of Science in Engineering 30,0 hp
Educational program
MTACI Master of Science in Mechanical Engineering
Supervisors
Examiners
Available from: 2019-07-02 Created: 2019-06-27 Last updated: 2019-07-02Bibliographically approved

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