MATHEMATICAL MODELING OF FRICTION FORCE AND FRICTION COEFFICIENT AT DEEP DRAWING PROCESS
This paper includes: experimental determination of process and blank holder forces at plate deep drawing, calculation of friction force and friction coefficient on the basis of achieved experimental results, determination of mathematical models Ft = f (SHP, φ, pd) and μ = f (SHP, φ, pd), as well as graphical simulations and analyses of achieved mathematical models. As substance for cooling and lubrication molybdenum disulfide and oil EP50 were used, while tribological conditions of contact surfaces were varied using phosphated and non-phosphated plate (EN 10027-1: DC04; DIN: RRSt14). Research results have shown that the best tribological conditions were achieved with molybdenum disulfide on phosphated plate, and the most influencing parameter is material deformation degree.
The tribological state test in metal forming processes using experiment and modelling
Purpose: of this paper is test of the tribological state in metal forming processes with main aims the determination of state on the tool contact surface (contact stresses and friction coefficient) friction coefficient modelling and simulation and to present the original method of defining contact stresses tf and pn and coefficient of contact friction mi. Design/methodology/approach: of this research is review of contact stresses determination methods, general principles of stochastic modelling, experimental friction test and modelling, examples tribological state test and simulaton by deep drawing and drawing processes. Main achievement are: original experimental identification of contact stresses, original experimental of tools for measurement of contact stresses, mathematical model for defining the tribological state. Application methods of this research are: experimental, tribological state test in forming processes by means of experiment and modelling, statistical and direct contact stresses determining method. Findings: experimental and stochastic modelling of tribological parameters of the forming processes and verification of mathematical model. The tribological state test is performed on the basis of experimental investigations and stochastic modelling. Research limitations/implications: modelling and optimization of tool geometry and selection of optimal lubricators, development experimental methods in the determination of contact stresses, etc. Practical implications: Results of investigations in processing conditions show that the desired effects can be achieved: increased durability of tools 20-40%, reduced stagnation time in the machining process 20-30%, increase on the productivity of the forming process 15-30% and less energy consumption up to 15%. Originality/value: of this paper is obtained original mathematical model for defining coefficient contact friction and contact temperature on the contact surface of tool. Also, is obtained original experimental tool for measurement of contact stresses.
Accumulation of Bone-Seeking Radionuclides in Liver Metastasis from Colon Carcinoma
Fifteen colon cancer patients with metastasis to the liver were examined by both liver and bone scans. Seven of these showed accumulation of bone seeking radionuclides in the liver at the site of a defect in the scan. Such accumulation was found in two diphosphonate, in one pyrophosphate and in six 18F scans. To our knowledge, this is the first series to report localization of 18F in intrahepatic metastasis from colon cancer. The precise mechanism for this non-skeletal accumulation is unknown.