【摘要】 针对已成型的多层聚合物制品中不同聚合物层厚度,提出基于超声波脉冲反射的测量方法.根据超声波在分界面的反射和透射规律,建立超声波在不同介质分界面的反射波声压幅值与声阻抗的关系.通过测量超声波在各层聚合物分界面的反射回波的声压幅值,计算各层聚合物的声阻抗,再除以该层聚合物的密度计算声速.将声速乘以测量得到的各界面反射回波的时间差,可以计算制品的各层壁厚.研究表明,与扫描电镜的测量方法相比,采用超声波方法测量得到的流体辅助共注成型制品各层壁厚有较好的精度,分层误差不大于4.5%,总厚度误差约为1.6%.更多还原

【Abstract】 A measuring method based on ultrasonic pulse reflections was proposed for measuring each different material layer’s wall thick of multi-layer polymer co-injection molded product.The relationship between pressure amplitude of reflected wave against the interface between the different plastic layers and their acoustic impedances was established according to the law of reflection and transmission in interface.Acoustic impedance of each plastic layer can be calculated via the measurement of sound pressure amplitude of echo reflected from interfaces between two adjacent plastic layers.Then ultrasound velocity in each plastic is equal to acoustic impedance dividing their density.Wall thickness of each layer is equal to the product of ultrasound velocity and the propagation time of ultrasound in each layer,which can be measured from the reflected wave.Results showed that the ultrasonic measuring method had good accuracy compared with the method using scanning electron microscope.Errors of each layer were less than 4.5%,and error of total thickness was approximately equal to 1.6%.更多还原