HDPE振动注射试样拉伸断裂行为研究

TENSILE FAILURE ANALYSIS ON HDPE VIBRATION INJECTION MOLDINGS

利用自行研制的低频振动注射实验装置,研究了注射成型对HDPE哑铃试样的力学性能及拉伸断口微观形态。与常规注射相比,振动注射能明显改善试样的拉伸强度,实现注射试样的自增强。在0Hz～0.7Hz之间增加振动频率能明显提高试样的强度,断裂伸长率明显下降;当f>0.7Hz,频率增加对拉伸强度的改变不大,断裂伸长率有明显的回升。提高压力振幅能大幅度提高屈服强度,但韧性有所下降。振动注射有利于晶体取向,制件的断裂方式由常规注射的塑性变形到振动注射的塑性降低,以至于呈现脆性断裂。

Used by the self-made low-frequency vibration injection-molding device, the effects of vibration injection molding on tensile properties of dumbbell specimen were investigated. In the research the mechanical performance and fractographs of the static sample and vibration-injected samples were compared with each other. Processed at the constant vibration pressure amplitude, low range of frequency(0 Hz<f<(0.7) Hz) is favorable to the increase of yield strength with part of plastics lost, and in the high range of frequency((0.7) Hz<f<(2.33) Hz) the promotion of yield strength and changes in elongation are little, and the fracture mode is plastic. At the constant frequency((0.7) Hz) the increase of vibration pressure amplitude can greatly increase the yield strength with decreased elongation, the maximal yield strength is (62.1) MPa compared with (43.9) MPa of conventional injection molding, the increase percentage is (41.5%), and the plastic deformation at low-pressure amplitude is changed to brittle fracture at high-pressure amplitude with clear three layers including skin, shear layer and core.