Mileta Janjić

Experimental-Numerical Friction Factor Determination

The subject matter of this paper is to research the friction factor defining contact conditions in deformation treatment. A very frequently used method of determining friction factor is by means of experimentally determined curves obtained on the basis of ring deformation. The results of various authors have been compared and significant differences have been stated in this paper. Taking into consideration the expansion of the numerical programme packages based on FEM simulation in this field, it is important to determine numerically the friction factor in wide range of possible values. This is a method of experimental-numerical friction factor determination has been proposed in this paper, thus giving possibilities for its precise determination. The friction factor determined in this way gives the results of numerical analysis close to real ones.

INVESTMENTS IN REPAIR OF OUTDATED METAL FORMING MACHINES AND EVALUATION OF THIS INVESTMENTS

The production of various details with deformation always wants work, accuracy and expenses. The purpose of these expenses at the beginning of the project also gives hope that these investments will return to us together with profit. In the Balkan countries, as we know, production in metal forming has stagnated. The privatization is not done so well that many metal forming factories have been returnet into various supermarkets. The few remaining factories are facing various problems. Among the problems with which most of them are faced is outdated machinery which in developed countries is sophisticated. The purpose of this paper is to present the possibility of investment in such machineries by taking as an example a metal forming press as well as evaluating the investment project in manufacturing of these press dies (tools). These evaluation of this investment will be done using IRR method. Application of internal rate return (IRR) method sends us in terms of investment assessment and potential benefit, taking into account all project data of investment.

A study on friction stir welding of AlSi1MgMn aluminium alloy plates

Original scientific paper Presented in this paper are an experimental investigation and numerical simulations of the Friction Stir Welding (FSW) process. The aim was to determine thermo-mechanical and kinematic parameters of the process of joining two AlSi1MgMn aluminium alloy plates with the thickness of 7,8 mm. Experimental study was designed based on the 2-level multifactorial design of experiment (DoE), with centre points. Parameters varied in the experiment were: welding speed, rotation speed, angle of pin slope, pin diameter and shoulder diameter. Based on the adopted geometric parameters, the family of tools was designed and manufactured for the experiment. The experiment was performed in laboratory conditions, which were similar to production environment. Numerical simulation of the FSW process was carried out using DEFORM-3D software. Detailed analysis of the process as well as comparison between experimental and numerical results is presented.