中文摘要：

超声检测单螺杆挤出机中聚合物共混状态时，螺杆结构对回波信号幅值的衰减有很大影响，从而难以判别共混状态。本文分析了螺杆结构对超声回波信号的影响，以超声传播时间为依据，建立螺杆结构模型，根据螺棱位置的回波幅度，计算出低密度聚乙烯（LDPE）的衰减系数和不同螺杆位置的反射系数比，通过拟合建立反射系数比与螺杆结构关系模型；将上述模型应用到混合物中，计算不同位置的传感器采集信号的衰减系数方差并以此表征聚合物混合状态的均匀性。实验结果利用样本的电镜扫描图验证：上述建立模型及混合状态的表征方法可以较好地判别聚合物的共混状态。

英文摘要：

In the ultrasonic testing of polymer compounding state in a single screw extruder, screw structure has a great influence on the amplitude attenuation of echo signals which is difficult to distinguish blending state. Screw structure on the influence of ultrasonic echo signal was analyzed in this paper. Based on the echo time, screw structure model was established. According to the echo amplitude of screw edge location, the ratio of attenuation coefficient of low-density polyethylene （LDPE） and reflection coefficient of different screw location was calculated. The relationship model between reflection coefficient ratio and screw structure was established. Applying the model to the mixture, the variance of signals attenuation was calculated to characterize the uniformity of polymer blending state. The experimental results were verified by the electron microscopy scans of samples. The results show that the proposed method in this paper can distinguish the polymer mixture uniformity effectively.