Abstract
Welding defects such as lack of penetration, undercutting, crater crack, burn-through and porosity can occur during manufacturing. Assessing weld quality using nondestructive evaluation methods is important for the quality assurance of welded parts. In this paper, the measurement of weld penetration, which is directly related to weld integrity, is investigated by means of ultrasonics. Both linear and nonlinear ultrasonic methods are studied to assess their sensitivities to weld penetration. Welded plates with different penetration depths controlled by changing weld heat input are manufactured using gas metal arc welding (GMAW). Microscopic properties are assessed after the ultrasonic measurements are completed. Numerical models are built using the weld profile obtained from macrographs to explain the relationship between linear ultrasonic and weld penetration. A quantitative correlation between weld morphology (shape, width and depth) and the energy of linear ultrasonic signal is determined, where the increase of weld bead penetration exceeding the plate thickness results in decrease of the energy of the ultrasonic signal. Minimum detectable weld morphology using linear ultrasonics is defined depending on the selected frequency. Microhardness measurement is conducted to explain the sensitivity of nonlinear ultrasonics to both weld penetration and heterogeneity in weld. The numerical and experimental results show that the weld geometry influences the ultrasonic measurement other than the materials’ properties.
Highlights
Gas metal arc welding (GMAW) is the most commonly used industrial welding process since the1940s in heavy industry manufacturing
In gas metal arc welding (GMAW), as with other welding processes, weld bead penetration is dependent on weld heat input, which depends on the type and thickness of metal alloy welded [1]
The objective of this study is to develop a quantitative nondestructive assessment of weld morphology for GMAW using ultrasonics
Summary
Gas metal arc welding (GMAW) is the most commonly used industrial welding process since the1940s in heavy industry manufacturing. Gas metal arc welding (GMAW) is the most commonly used industrial welding process since the. In a GMAW process an electric arc is established between a consumable solid wire electrode and base metal using an externally supplied shielding gas. The intense heat from the electric arc melts a localized portion of the base metal and the consumable wire, which form a weld bead that is part of the weld joint. Weld related parameters involved in the process which control weld quality, include type of shielding gas, gas flow rate, wire feed speed that depends on the applied current, voltage and travel speed. In GMAW, as with other welding processes, weld bead penetration is dependent on weld heat input, which depends on the type and thickness of metal alloy welded [1]. The assessment methods can be categorized as in-situ monitoring and Materials 2020, 13, 2307; doi:10.3390/ma13102307 www.mdpi.com/journal/materials
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