The tribological properties of PA66, PA46, and PTFE-mixed PA46 were investigated. The tests were achieved on a pin-on-disc tribometer. Before tests with different sets of parameters, a running-in-type test (with constant parameters) was performed for all the materials, under lubricated and dry conditions. The tests parameters were variable referring on load, velocity, and temperature. The results are referring on the value of the wear developed during the run-in period and on the variation of friction coefficient with the testing parameters. The results show that the PTFE-mixed PA46 polyamide has better tribological properties than the PA66 and the PA46 polyamide.

Over time, many minted coins were withdrawn from circulation, being replaced with new ones. The returned, obsolete metal coins were melted in order to ensure sustainable reuse of the alloy for other purposes. Between the withdrawal and melting, some of the metal coins were canceled by the destruction of their original shape and dimensions using adequate tools. The first part of this paper is focused on presenting some insights into the canceling method used on old Romanian nickel coins; also, some examples are presented. The introduction also includes a literature review in the field of coin manufacturing, covering subjects such as metal behavior under striking load and aspects of 3D modeling and FEM analysis as well as explaining some striking errors. The main purpose of this paper is to study the particularities of canceling methods applied to coins, which is conducted on relatively valuable collection metal pieces. In the second part of the paper, an adequate 3D model is computed for the canceling dies and the coin. Then, the assembled models are introduced, corresponding to each canceling case, consisting of the obverse and reverse canceling dies with coins inside them. For each model, the finite element analysis is realized and is achieved for different initial conditions. The final part of the paper presents the analysis results as well as the discussion and conclusions.

The silent chain transmissions are widely used in automotive industry as part of the distribution transmission for the combustion engines. The investigation of friction loses in chains is important in order to find out the influence of their constructive and exploitation parameters. The paper presents the results of the tests performed on a test rig used in the case of transmissions with parallel axes. The main contribution of the paper is represented by determining the influence of speed, tensioning force, temperature and pitch on the friction loses of silent chains. Two types of silent chains are tested: LD6 with the pitch equal with 6.35 mm and LD8 with the pitch equal with 8 mm. The tests have been achieved with the following test parameters: the driver sprocket rotations with the values of 500, 1000, 1800 and 5000 r/min; the tensioning force with the values of 0.5, 1, 2 and 3 kN; the lubrication oil temperature equal with 40°C, 90°C and 115°C. Conclusions are drawn regarding the influence of the chains’ pitch and of the exploitation parameters on the frictional torque. The presence of boundary or mixed friction in the joints of the chain explains the frictional behaviour of the chain.

The paper presents the study of the friction, by using tests, in the sliding translational oscillating motion of the steel on PA46 relative to the steel on PA66 type materials by considering as variables the testing parameters as: the load, the velocity and the operating temperature. The paper starts with a study of the literature and, according to that, presents the main conclusions regarding the sliding friction of the steel on PA66 and PA46 type materials and identifies the lacks of the results. The tests are performed on an oscillating motion type tribometer module. First, it is made a running-in program, for each of the materials, at 25 and 90°C, a load of 5 N and a frequency of 1 Hz for one hour; after that, there are performed tests at 90°C and 120°C, at loads of 3 N, 5 N, 7 N and at frequencies at 0.25 Hz, 5 Hz and 1 Hz. The results are presented for the PA46 type material relative to the PA66 material. The conclusions indicate in which conditions and with which advantages are used the PA66 and PA46 polyamides in the case of oscillating translational motions.

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