高聚物拉伸形变中的声发射

对一系列高聚物进行了单轴拉伸过程中声发射的观察,包括玻璃态高聚物、结晶高聚物、共聚物、共混高聚物和一种交联橡胶。非晶态高聚物拉伸时声发射次数很少,伴随银纹和微裂缝的产生而出现。结晶高聚物在屈服成颈时出现强的声发射,在颈部拉伸的初期声发射较少或不出现,拉伸到接近试件断裂前声发射强烈,次数急剧增多。相同高聚物但试件加工成形历史不同会在声发射上得到反映。交联的顺丁橡胶拉伸时声发射很弱,但可以观察到,在拉力-形变曲线开始偏离线性后出现,没有Kaiser效应。共混高聚物拉伸时声发射很多。高耐冲击共混接枝塑料在断裂前不出现强烈的声发射。如试样和试件加工成形条件相同,声发射现象的重演性是相当好的。

ACOUSTIC EMISSION DURING STRETCHING OF POLYMERS

Acoustic emission has been studied for a wide range of polymers including amorphous glasses, semi-crystalline polymers, copolymers, polymer blends and a crosslinked rubber during the course of uni-axial stretching at room temperature. For noncrystalline polymers acoustic emission occurred in rather small number of events accompanied by crazing and micro-crack formation. Strong acoustic activity appeared during yielding and necking of crystalline polymers. Rather small number or none of acoustic bursts occurred during the initial stage of neck drawing but numerous strong bursts appeared when drawing proceeded approaching specimen break. Specimens of the same polymer but of different fabrication history may be reflected in their acoustic emission behavior. Acoustic emission during stretching crosslinked polybutadiene rubber was very weak but observable when the force-elongation curve started to deviate from the linear region. No Kaiser effect was observed for the rubber. Very strong and numerous acoustic emission was observed during stretching specimens of polymer blends. High impact resistant polymer modifications showed no sharp increase of acoustic activity before specimen break. So long as the polymer and conditions of specimen fabrication are the same quite reproducible acoustic emission behavior could be observed.