Determination of flow stress and friction in cold forging is of paramount importance. In this work, an inverse procedure is developed for predicting the Coulomb’s coefficient of friction and strain-dependent flow stress simultaneously based on the measurement of bulge and forging load. It is also established that in cold forging Coulomb’s coefficient of friction can be approximated as half the friction factor in Tresca (or constant friction) model. In the inverse procedure, forging load is estimated analytically but bulging is estimated by developing an empirical relation. The efficacy of the inverse procedure is ascertained by the data obtained from finite element method simulations. Finite element method was implemented in ABAQUS and validated with the results available in literature. In most of the cases, inverse procedure provides less than 5% error in the estimates of friction and flow stress. A sensitivity analysis is also carried out to study the effect of measurement error. It is observed that error in the estimation of friction is proportional to error in the measurement of bulge. The novelty of the method lies in the quickness and simplicity of the method.

A study of mechanical and optical properties of samples of transparent plastic Polyethylene terephthalate glycol (PETG) manufactured by additive technology Fused Filament Fabrication (FFF) was carried out. PETG plastic is used in medicine, particularly in dentistry due to its unique set of properties: strength, elasticity, resistance to aggressive environments, transparency. Preserving the complex of properties of PETG plastic, including transparency, during 3D-printing is an important technical task. In order to solve this task a set of studies of PETG laboratory samples was carried out. The optimum modes of 3D printing were determined to provide PETG samples with increased strength properties, preservation of elastic properties and optical transparency of the material. The increase in the optical transparency of the material is provided by an additional post-treatment of the printed samples surface with a chemical reagent. The influence of technological parameters of the post- treatment mode on the mechanical and optical properties of the printed samples has been investigated. The novelty of the work consists in a comprehensive study of the modes of manufacturing products from PETG by technology FFF with subsequent post-treatment, allowing to preserve the transparency of the polymeric material.

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The paper describes the research of springing of a multilayered material. It shows the comparison of springing of a single-layer and multilayered sample. The article considers the change character of springing that depends on a bend angle and internal radius.

The paper proposes a scheme of testing with a uniform deformation for measuring the properties of multi-layer material with viscoelastic connective layer while performing experiments on the shift. Experimental results showing the features of large shear deformation of a viscoelastic layer and the elastic layer in the samples are provided.