Research On Relative Velocity Coefficient Based On The Rapid Measurement Of Internal Stress Of Polymer Sheet

Polycarbonate sheet products are used for producing car windshields, airplane external windows and the astronaut helmet shield and so on. The main factors affecting the service life, the optical and mechanical properties of polycarbonate sheet products is the surface smoothness of products, dimensional accuracy and surface stress and so on. The surface smoothness of products and dimensional accuracy can be achieved by the corresponding detection means to achieve accurate measurement and can meet requirement by changing the mold machining accuracy, improve technological formula and improve the control of process parameter accuracy and so on. But the internal stress of polymer sheet products are unable to achieve precise measurement. Research on the basic theory of Rayleigh wave measurement the polymer sheet internal stress based on the acoustic elasticity theory combined with the structure property of the polymer sheet products. The relative velocity coefficient method is derived, it can be fast, accurate and qualitatively achieve the polymer sheet internal stress measurement. The acoustic elasticity coefficient measurement which is difficult to measure can be effectively avoid by the relative velocity coefficient method. By building the experimental verification experiment device, and the sound velocity change internal stress measurement model is established base on a lot of experimental data. It can be quickly and accurately measure effectively for the distribution of the polymer sheet internal stress. This kind of method provide a favorable guarantee to improve the process condition, and reduce the forming process of internal stress of polymer sheet. Main work is as follows:1、Comprehensive analysis the characteristics and application of Rayleigh wave propagation. Research on the relationship between Rayleigh wave propagation velocity and polymer sheet internal stress. Relative velocity coefficient method is put forward based on acoustic elastic theory. To establish the relationship between polymer sheet internal stress and Rayleigh wave propagation velocity by relative velocity coefficient, to avoid the acoustic elastic coefficient which is difficult to measure. Provide a theoretical basis for distribution of polymer sheet internal stress by Rayleigh wave rapid measurement.2、Experiment platform is set up about the polymer sheet internal stress by the measurement of ultrasonic. Rayleigh wave measurement system based on relative velocity coefficient is development. It can realize the Rayleigh wave transmitting and receiving. The servo drive for accurate measurement of probe distance based on difference method is development. And the calibration device based on relative velocity coefficient is development.3、The feasibility of relative velocity coefficient method is verified by the experiment based on the experiment platform of setting up. Rayleigh wave propagation velocity when polycarbonate sheet with no stress by the experiment. Polycarbonate sheet drawing, the experiment verification of relative velocity coefficient when Rayleigh wave propagation direction tensile stress direction parallel or perpendicular. Comparison and analysis between the internal stress distribution by Moldflow and the internal stress distribution by experimental measurement, and determine the accuracy of the relative velocity coefficient method.4、According to the experimental data of the internal stress and Rayleigh wave propagation velocity, establish the soft measurement model of polymer sheet internal stress base on Rayleigh wave propagation velocity. Finally, the measurement model is embed to Rayleigh wave measurement system, and implement the rapid measurement of polymer sheet internal stress distribution and numerical.