Evaluation of Stresses in a Two-Layer Co-Extruded LDPE Melt Blown Film
Despite the fast growth of co-extruded film production, little research work has been devoted to this process. Films of LDPE, ULDPE, LDPE/ULDPE and ULDPE/LDPE were produced at various processing conditions. A continuous experimental set up was used to evaluate the in-plane birefringence during bubble formation. The data collected were used to derive the axial and transverse stresses. A non-isothermal Newtonian model that allows the determination of the kinematics and dynamics of the two-layer film blowing process was then used to calculate the axial and transverse stress. Generally the calculated stresses are in agreement with the experimental values.
Unsteady extrusion of a viscoelastic annular film: I. General model and its numerical solution
Abstract The unsteady extrusion of a viscoelastic film from an annular and axisymmetric die is examined. This moving boundary problem is solved by mapping the inner and outer liquid/air interfaces of the extruded film onto fixed ones, and by transforming the governing equations accordingly. The ratio of the film thickness to its inner radius at the exit of the die is used as the small parameter, e, in a regular perturbation expansion of the governing equations. Forces applied on the film give rise to four dimensionless numbers: Stokes, Capillary, Reynolds and Deborah. When the Oldroyd-B model is used, the dimensionless retardation time also arises. For typical fluid properties and process conditions, the Stokes and Deborah numbers are O(e0), i.e. much larger than the other relevant dimensionless numbers. In such cases, the base state is significantly deforming with time and it is calculated numerically by solving a partial differential system of equations in time and the axial direction. Special attention is required for its accurate numerical solution. It was found that gravity plays the most important role in the process by accelerating the film, deflecting its inner and outer surfaces towards its axis of symmetry and decreasing its thickness around the middle of its length. For typical values of the De number, its increase leads to deceleration of the film that has less curved interfaces and more uniform thickness along its length. These effects become apparent, if the St number is of order one; if it is smaller, the effects of fluid elasticity decrease considerably. For typical values of the Ca and Re numbers, and of the retardation time of the fluid, their influence on the process is small.
The measuriment of ferromagnets magnetic characteristics using Labview software
The digital method of measurement and registration of dynamic loops hysteresis family of magneto-soft materials where, along with known analogues from electro-technical steel, magnetic materials with considerably smaller specific magnetic losses such as amorphous alloys on the basis of iron, is offered. Tests of magnetic properties of materials are carried out on the base of the hardware-software measuring complex in which along with the standard established electric equipment and USB oscillograph for realization of a digital method, the software for the personal computer developed in the environment of visual programming of Borland Delphi 7.0, connected through the ActieveX technology with the Labview 7.0 environment, is applied. The software allows carrying out input of basic data concerning geometry of prototypes of cores from magnetic materials and numbers of rounds of the magnetizing and measuring windings located on their surface. Experimental data on voltage at measuring winding terminals are processed by means of the virtual integrator in a Labview package. The developed software provides the possibility of saving the obtained hysteresis loop in the form of a text file, and creation of the hysteresis loops family on the virtual oscillograph screen.