This paper presents the results of FEM numerical simulations, of the HC260Y steelsheet mechanical clinching process. The starting tool parameters were chosen for the central composite design of experiments, in order to find out which tool parameters have the largest contribution to the sheet joint interlock. Assessment of the mathematical model, and analysis of variance (ANOVA) were performed within the design of experiments. This numerical analysis was done to find the most suitable tool geometry and tool work stresses, so that the tool sets for further experiments could be manufactured and results compared with numerical results.

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The production of compensators (expansion joints), and especially of bellows as their most demanding elements, requires the usage of stainless materials. These stainless materials exhibit certain particularities at welding (and quality control) since they are very thin, i.e., their thickness ranges usually from 0.12 to 3.00 mm. This paper starts with the elaboration of compensators and their application, and further presents characteristics of the material selected for experimental testing. In the second part, the paper continues with a description of the experiment referring to longitudinal welding of samples without filler material. The experiment focused on the determination of accurate characteristics of radiographic recordings and their assessment based on comparison with the tensile testing (mechanical properties), FEM numerical simulation and dimensional control. The paper also presents the analysis of obtained results and conclusions made thereof. The research hypothesis was to determine in what way the welding parameters affect the mechanical properties, the geometric shape of the welds, and the exploitation possibilities of the compensator. According to the performed experimental part and the performed testing of mechanical properties, all welded joints are acceptable for use. Nevertheless, according to the standard that prescribes the acceptability criteria of defects that occur in welded joints, some of tested samples were not suitable for operating conditions. Such kinds of welded sheets must be repaired or eliminated from further processing.

Original scientific paperThe automobile chassis is produced from various metal formed parts that are welded together. Trends in the automobile industry show that most of the car manufacturers tend to use high strength, lightweight materials. The main reasons for this are minimization of the used material and better fuel economy of the produced cars. Such lightweight materials often have high strength which causes large amounts of elastic unloading (springback) after sheet metal forming operations. Mostly used sheet metal forming process is the bending process, where the elastic springback can be severe thus diminishing the desired accuracy of the part. In this paper, the comparison between mathematical models, FEM method and experiments is shown, and the effects of Vtool bending process parameters can be seen on the resulting sheet angle of the HC260Y steel. Keywords: bending; FEM; V-tool Točnost savijanja čeličnog lima HC260Y u različitim konfiguracijama V-alataIzvorni znanstveni članak Karoserija automobila je izrađena zavarivanjem različitih dijelova koji su prethodno izrađeni tehnologijama oblikovanja lima deformiranjem. Trendovi u automobilskoj industriji pokazuju kako sve vise proizvođača koristi lake, visokočvrste materijale. Glavni razlozi ovom trendu su minimizacija korištenog materijala i bolja ekonomičnost automobila u vidu potrošnje goriva i manje emisije ispušnih plinova. Takvi visokočvrsti materijali imaju, kako naziv govori visoku vlačnu čvrstoću i granicu razvlačenja, što uzrokuje velike iznose elastičnog povrata nakon operacija oblikovanja deformiranjem. Najviše je u proizvodnji raširen postupak savijanja, gdje za visokočvrste materijale veliki elastični povrat može narušiti željeni oblik i preciznost izrađenog proizvoda. U ovom radu je prikazana usporedba između rezultata dobivenih matematičkim modelima, metode konačnih elemenata i rezultata eksperimenata i vidljiv je utjecaj procesnih parametara u postupku savijanja V-alatom na konačni kut savijenog lima od HC260Y čeličnog lima.