Distribution of Temperatures and Assessment of Durability along the Width of a Butt Weld at Ultrasonic Welding of Plastics

The principles of the decrease in durability of butt weld joints with the wall thickness of more than 5 mm performed by ultrasonic welding are examined in this work. It is established that the temperatures and the nature of their distribution along the width of the weld joint as well as anisotropy of the weld seam material have a significant influence on the decrease of the relative durability of butt weld joints made of rigid plastics when the thickness of the welded material increases. To increase heat emission in the welding zone, a method of ultrasonic welding based on step-by-step concentration of energy of ultrasonic oscillations, an original design of the weld joint and the grooving that strengthen the joint is proposed. A mechanism of weld seam formation for this welding method is described. It is established that when the thickness of samples is more than 6 mm, one of the reasons for the dip in the strength of weld joints is insufficient temperature of melting of the polymer material at a distance of more than 3 mm from the centre of the surface of the V-shaped groove. The influence of the temperatures on the strength of weld joints along the width of the weld seam is determined. Optimal parameters of the ultrasonic welding mode are determined.

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