Mathematical Representation of Friction in Metal Forming Analysis
As recently stressed by Kalpakjian [1]. Schey [2] and many other authors [3-8] the development is an improved friction model is an important topic in metal farming analysis. In the present study a fresh friction approach is suggested. It connects the friction shear stress not only with the normal stress but also with the relative displacement between tool and workpiece and the relative surface increase. The model presented is based on the physical conception of the friction phenomenon as described by Schey [2.4″], Wanheim, [7] and Dautzenberg [8, 9]. Connections with the well known Coulomb model (T Fr = up) and the so called constant friction model [T Fr = m J F /✓3 and discussed. Theoretical findings are verified with experimental data from different tests. Although a few questions are still open, some progress in technical understanding of friction in forming tools could be achieved.
Validation of Frictional Studies by Double-Cup Extrusion Tests in Cold-Forming
Abstract Studies on frictional conditions in cold-forming have shown that, for a given lubricant, friction factor values are strongly affected by the test method. In the present paper, different cold-forging processes of an aluminium alloy, are modelled by a FEM numerical code using the m values obtained by both the double cup extrusion and ring compression tests. It appears that the m values given by the ring tests can be effectively used in the simulation of upsetting processes, while the m values derived by the double cup extrusion tests are more appropriate for predictions in extrusion and closed-die forging operations.
Investigating the Optical properties of cd1-xznxs thin films deposited by the Dip Technique
A Thesis submitted to the Department of Physics, Kwame Nkrumah University of Science and Technology, in partial fulfillment of the requirement for the degree of 
Master of Science (Solid State Physics)