Defect analysis on welded workpieces from aluminium alloy with phase array ultrasonic testing method

Neporušne preiskave materialov so ključnega pomena za zagotavljanje kakovosti in varnosti pri uporabi različnih strojnih delov. Vse več se preizkuša tekom uporabe, zvarjence ter izdelke z različnimi nanosi barve in drugih zaščit. Pri pregledovanju zvarnih spojev smo najuspešnejši z ultrazvočno tehniko s faznim krmiljenjem, ki nam omogoča opazovanje materiala pod različnimi koti. V okviru raziskave smo ugotavljali vpliv različnih debelin in vrst nanosov na zmožnost zaznave indikacij napak ob uporabi različnih ultrazvočnih sond z različnimi lastnostmi. Ugotovili smo, da nam večanje debeline nanosa veča dušenje ultrazvoka zaradi česar je potrebno večati registracijsko ojačanje za zaznavo indikacije napake. Dušenje ultrazvoka je večje in njegova prodornost v material manjša pri ultrazvočnih sondah višjih frekvenc, vendar je pri tem ločljivost zaznave napake boljša. Dobljeni signal je odvisen od vrste indikacije napake oziroma od njene oblike, saj je odbito valovanje od indikacij napak z ravnim robom boljše kot pri ukrivljenih površinah. Pomembno vlogo pri preizkušanju ima tudi velikost posamezne sonde in njenega klina, kar vpliva na dolžino zvočne poti ter dostopnost pri preizkušanju strojnih delov.Non destructive testing of materials are crucial for ensuring quality and safety in the use of various mechanical parts. Most testing’s are made on already used parts, welded sheets and through various coatings of paint and other protections. When inspecting welds we are most successful with phase array ultrasonic testing technique which allow us to observe the material from different angles. Since more and more inspections are carried out on parts already in use and therefore coated with different thicknesses of anticorrosion protection, it is necessary to determine the influence of the coating thickness on testing results and differences when using different ultrasonic probes with different properties. From the results we learn that higher coating thickness increases ultrasound attenuation which is why we need to increase registration gain to detect material defect. We learn that ultrasound attenuation is bigger and ultrasound penetration is smaller when using probes with higher frequencies. However the resolution of defect detection is better using higher frequency probes. Inspection signal depends on type of defect and its shape. Reflected wave of defects with straight edges is better than inspecting curved defect surfaces. The size of the individual probe and its wedge also plays important role in testing and affects the length of the sound path and accessibility when inspecting different machine parts