Experimental Research and Method for Calculation of 'Upsetting-with-Buckling' Load at the Impression-Free (Dieless) Preforming of WorkpieceVolodymir Kukhar, Victor Artiukh, Andrii Prysiazhnyi and Andrey PustovgarE3S Web Conf., 33 (2018) 02031DOI: https://doi.org/10.1051/e3sconf/20183302031