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.

When talking about tests that include measurements, the uncertainty of measurement is an essential element because it is important to know the limits within the obtained results may be assumed to lie and the influence the measurement technological system elements have on these results. The research presented in this paper focuses on the estimation of the Vickers hardness uncertainty of measurement for the heterogeneous welded joint between S235JR+AR and X2CrNiMo17-12-2 materials in order to establish the results relevance and the quality assessment of this joint. The paper contents are structured in three main parts. In the first part, the initial data necessary for the experiment is presented in terms of the welded joint and technological means characterisation. The second part presents the physical experiment development and its results and in the third part the uncertainty of the measurements is calculated and a results discussion is undertaken.

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.