Welding ultrasonic, shear joint

Ultrasonic Welding. Ultrasonic welding has been appHed to Tefzel with weld strength up to 80% of the strength of the base resin. Typical conditions include a contact pressure of 172 kPa (25 psi) and 1—2 s cycle time. The two basic designs, the shear and butt joints, employ a small initial contact area to concentrate and direct the high frequency vibrational energy. 

Figure 26.29 Typical ultrasonic welding shear joint configuration.

We also previously studied ultrasonic welding of HDPE clay nanocomposites [7]. Here too we found that weld strength decreased with increasing clay content. However, the decrease in weld strength was smaller for the shear joints than for the energy director joints indicating that flow could impact weld quality [7]. 

Lamellar tearing is generally found in the HAZ of weldments of tee and corner joints. The cause of cracking appears to be inclusions that are parallel to the rolling direction of the plate section being welded. The restraining forces in the welded joint cause the inclusions to open up and run together to form a crack. Set on-type connections welded to heavy sections are particularly susceptible to this type of defect. Where set on-type connections are used, shear-wave ultrasonic inspection of the plate in the area of the attachment and of the completed weld is recommended. 

Ultrasonic welding is used to assemble amorphous and semicrystalline thermoplastic components that have joints that are butt, lap, tongue and groove, and shear. The typical ultrasonic normal vibration in the range of 15-70 kHz and 10-50 pm oscillates two mating components to create the weld. The amplitude of vibration generates the heat required to melt and flow the joint and is thus polymer dependent. Ultrasonic... 

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