QUALITY ASSURANCE OF STRUCTURAL ALUMINUM AEROSPACE MATERIALS THROUGH NON DESTRUCTIVE TESTING TECHNIQUES

In this work, a new method was developed for structural integrity of welded Aluminum 6082 aero grade material by the means of tensile load as source of initiation and propagation of defect through ultrasonic examination. Three type of tensile samples good/no-defect, defect (Lack of penetrant) and un-welded with dimension shoulder 50*20*8 mm and 57 mm as gauge length have been chosen for reasons of their dimensional acceptability and availability. The tensile samples of both good and defective category were Gas tungsten arc welded (GTAW) which have gone through have gone through X-ray radiography for their reference characterization. Three types of tensile samples were subjected to maximum tensile load which set back as referenced for further examination. To study the initiation and propagation of defect in material, additional set of welded tensile samples of both category samples were subjected to intermediate load of 7.3 KN and 14 KN for good sample, 6 KN and 11KN for the one with defects. These four samples were examined visually for elongation, Surface defects and any other impressions occurred due to the loading. The ultrasonic investigation is carried for internal changes occurred in weld and Heat Effect Zone (HAZ) regions. It is identified that porosity flow at 6 KN in good weld and been propagated 5 mm long by 14 KN load, with an elongation of 2 mm further necking occurred and sustained maximum tensile load 21 KN with 8 mm elongation. Whereas in defect sample 77 % amplitude ultrasonic echo of lack of penetrant is recorded at 6 KN load, propagated by 0.35 mm long due to increase of load by 11 KN with no elongation, maximum tensile load of 18 KN with 2 mm elongation is recorded with brittle fracture. Brinell hardness (study) of the weld, HAZ and parent material was also carried out and a correlation is established in the tensile strength and hardness.