Comparison of the Modified Campbell-Dontula Model with Experimental Data

4 Comparison of the Modified Campbell-Dontula Model with Experimental Data 

This section wiil compare the modified Campbeii-Dontula modei to the experimen-tai data for the LDPE resin. The physicai properties for this resin were provided in Section 5.3.2. The dynamic coefficients of friction are avaiiahie in Appendix A5 and are reported as stress at a sliding interface. The coefficient of friction is related to the stress at a sliding interface as follows  

The modified Campbell-Dontula model was developed using the LDPE resin friction data as applied to an empirical model. The empirical model is shown by Eq. 5.31 for the temperature range of 25 to 110 °C. The coefficients of dynamic friction using Eq. 5.31 is shown in Eig. 5.31. 

V is the sliding velocity in cm/s, P is the pressure in MPa, and T is the interface temperature in degrees Celsius. The constants in the equation have units and these units have been omitted for clarity. At temperatures less than about 110 °C, the stress at the interface is due to a frictional force mechanism. At temperatures higher than 110 °C, the forces are from a viscous mechanism. The friction coefficients provided by Eq. 5.31 have the proper trends. Coefficients derived from the equation, however, need to be used with care because of its empirical nature and the difficulties in measuring frictional data. 

The soiids conveying rate data as a function of discharge pressure at a screw speed of 50 rpm and barrei and screw temperatures of 75 °C are provided in Tabie 5.1. 

---