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Values of tensile strength and hardness of different welding joint area has great importance. In this study a combination of welding processes include Friction Stir Welding (FSW) and ultrasonic welding has been used in butt joint for ABS type plastic sheets. Thus ultrasonic vibrations is put on FSW rotary tool, then some parameters effects such as tool rotary speed, travel speed and tool shoulder diameter on tensile strength and hardness of welded samples have been studied. With attention to parameters number and related levels to each one for doing experiments with Taguchi method L18 array has been selected. Parameters effect has been studied separately. Results showed that ultrasonic vibration putting improves tensile strength and hardness of welded joint. After ultrasonic vibration, tool rotary speed, tool shoulder diameter and travel speed were the most effective parameters on tensile strength and hardness of joint in order. Results from optimization with analysis method showed that ultrasonic vibration put rotary speed of 1200 RPM, travel speed of 60 mm/min and tool shoulder diameter of 22 mm causes the most hardness and tensile strength of joint simultaneously.