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.
Recent progress in metal forming tribology
A review of recent progress in metal forming tribology, both in bulk and sheet-forming processes, with regard to advances in fundamental concepts, test methods, developments in various areas of metal forming processes, lubricants and lubrication, improvements and new applications.
Use of a specific antiserum for renin detection in human kidney.
The use of anti-human renin antibodies made possible the intrarenal localization of renin in human kidney by immunofluorescence. In normal kidney, only some juxtaglomerular apparatus (JGA) were fluorescent. In these JGA, granular or diffuse fluorescence was only seen in afferent arterioles and was not present in all cells. In the ischemic areas of partially infarcted kidney, fluorescence was seen in all JGA and in interlobular arteries. In these arteries the most eccentric cells were often the most positive. In the nonischemic areas of the same kidneys, fluorescence was not seen in JGA, but was observed in proximal tubular cells, suggesting the reabsorption of filtered renin at this site.