THE EFFECTS OF VIBRATION ON THE MECHANICAL PROPERTIES OF LOW - CARBON STEEL WELDED JOINTS

Abstract

In this study, the effects of mechanically induced vibrations on the mechanical properties of low carbon steel (0.18%C) was evaluated. Specimens were prepared for double V-butt welding on an electro-mechanical vibrating device that was designed and constructed specifically for the purpose of inducing vibration of frequencies OHz. 8.33Hz, 16.67Hz, 33.33Hz and 50Hz in the vertical direction on the welded joints. Tests for the percentage elongation, yield strength, impact strength and hardness tests were carried out. Metallographic analysis of the joints was also carried out. The yield strength increased with the frequencies of vibration up to a maximum value of 378N/mm about 47H, the percentage elongation had a generally increasing trend, and the impact strength was steadily declining while the hardness property initially increased with the frequencies of vibration up to a maximum value of at 1.6kN/mm² at about 30H: but thereafter started to drop. It is discernable from the photomicrographs that the grain sizes of the welded joints was decreasing steadily with the increase in vibration frequencies up to a minimum value of about 0.83µm at 32Hz, which is the point of the best grain refinement, but thereafter started rising.