The aim of this paper is to conduct an experimental study in order to obtain a roughness (Ra) prediction model for dry end-milling (with an AlTiCrSiN PVD-coated tool) of the Co–28Cr–6Mo and Co–20Cr–15W–10Ni biomedical alloys, a model that can contribute to more quickly obtaining the desired surface quality and shortening the manufacturing process time. An experimental plan based on the central composite design method was adopted to determine the influence of the axial depth of cut, feed per tooth and cutting speed process parameters (input variables) on the Ra surface roughness (response variable) which was recorded after machining for both alloys. To develop the prediction models, statistical techniques were used first and three prediction equations were obtained for each alloy, the best results being achieved using response surface methodology. However, for obtaining a higher accuracy of prediction, ANN models were developed with the help of an application made in LabView for roughness (Ra) prediction. The primary results of this research consist of the Co–28Cr–6Mo and Co–20Cr–15W–10Ni prediction models and the developed application. The modeling results show that the ANN model can predict the surface roughness with high accuracy for the considered Co–Cr alloys.

This study evaluates the response of flame-retardant polypropylene composites after long-term exposure to aqueous and chemically aggressive media. Polypropylene (PP), used as a reference material, and PP-based composites containing 5, 10, 15, 20, and 25 wt.% of a phosphorus-based intumescent flame-retardant additive were immersed in water, NaCl solution, H₂SO₄ solution, and NaOH solution for up to 200 days. The material behavior was initially assessed by gravimetric measurements, based on the absorption/degradation degree calculated for early, mid, and late exposure intervals. This allowed the evolution of the material–medium interaction to be tracked not only by individual mass variations but also by average trends over the exposure period. The exposed systems were further investigated by thermogravimetric analysis (TGA/DTG) and dynamic mechanical analysis (DMA) to determine whether contact with the selected media modified the thermal degradation profile or the dynamic mechanical response of the composites. The results showed that the incorporated flame-retardant additive increases the interaction of PP with the liquid media, especially at intermediate and high additive contents. TGA/DTG and DMA confirmed that the thermal and viscoelastic behavior of the PP-based systems was maintained after long-term exposure, indicating that the observed medium-induced interactions did not result in substantial deterioration of their bulk thermo-mechanical properties.