Effect of ultrasonic vibration time on the molecular stacking structure and mechanical properties of the injection molding workpiece

Abstract

AbstractTo study the effect of the high‐frequency vibration time on the mechanical properties of the injection molding workpieces, apply an improved ultrasonic vibrator which contains the original ultrasonic vibrator and the mold insert to change the crystal structure during the melt cooling stage. The crystallinity, crystal perfection, and yield stress characteristics of the workpieces under three injection temperatures were compared with those without ultrasonic vibration. Results manifested that the change of the yield stress and cross‐section crystallinity of the sample obeys the Gaussian distribution at a specific ultrasonic vibration time. The maximum yield strength and the maximum change of the workpiece were 39.06 MPa (220°C, 8 s) and 12.70% (240°C, 10 s), respectively. With the ultrasonic vibration time increased, the crystallinity of the specimen surface decreased; the transition layer and crystal perfection increased first and then decreased. Therefore, considering the relationship between the ultrasonic vibration time and the yield stress, the vibration effect played a critical role at the initial stage of the ultrasonic vibration; the vibration induced the thermodynamics effect required a certain vibration time. This study contributed to changing the mechanism of crystal structure and yield stress under different ultrasonic vibration time.