Investigation of the effects of ultrasonic vibration-assisted micro-upsetting on brass

Ultrasonic vibration is widely applied in traditional metal forming to soften material and to increase formability. However, the effects of ultrasonic vibration on miniaturized workpieces must be studied before applying its benefits to metallic micro-forming.This study investigates the effects of applying ultrasonic vibration to micro-forming, along with two other factors: specimen size and grain size. Conventional (without ultrasonic vibration) and ultrasonic vibration micro-upsetting experiments were conducted using brass (C2600). Specimens of three different dimensions (ϕ3×4.5 mm, ϕ2×3 mm, and ϕ1×1.5 mm) and of three grain sizes (12 μm, 44 μm, and 90 μm) were used.The conventional micro-upsetting (CMU) experiment revealed the size-effect in which flow stress decreased with the miniaturizing of the specimen. Flow stress also decreased as the grain size increased, but at a smaller magnitude than that of the size-effect. Results show that ultrasonic vibration-assisted micro-upsetting (UMU) decreased the flow stress effectively, especially in miniaturized specimens. The amount of decrease was related more to the dimension than to the grain size of the specimen.