Investigation of the Stress-Strain State of a Steel Column Base Connection for Seismic Regions

Currently, the main type of connection between a steel column and a reinforced concrete foundation is a steel base, which is often economically unprofitable due to its size, number or diameter of anchor bolts. Not only in Armenia, but also in most countries, a steel base is the main type of connection between a steel column and a reinforced concrete foundation. The usage of other types of connections is associated with both new calculation methods and technological problems. The possibility of computation and design of the connection of a steel column with a reinforced concrete foundation in seismically active regions using shear studs is considered in this work, a reinforced concrete section with longitudinal reinforcement is used for this type of connection which ensures a smooth transfer of forces from the column to the foundation. Based on the example of the connection of a single-story industrial building column shows the change in the stress-strain state of the connection under axial force and bending moments for seismic regions. Not only the feature and construction technology of the connection considered in the work, but also proposes a calculation method with future possibility of its subsequent inclusion in the building codes of the Republic of Armenia.

Fabrication and Characterization of Steel-Base Metal Matrix Composites Reinforced by Yttria Nanoparticles through Friction Stir Processing

Friction Stir Processing (FSP) was used to fabricate metal matrix composite, based on steel and reinforced with nano-sized yttrium oxide powder. The powder was packed in a narrow longitudinal groove of 2 mm depth and 1 mm width cut in the steel plate’s rear surface. Different rotation speeds of 500–1500 rpm were used, at a fixed traveling speed of 50 mm.min−1. Single-pass and two passes, with the same conditions, were applied. The direction of the second pass was opposite to that of the first pass. After the first pass, complete nugget zones were obtained when the rotation speeds were more than 700 rpm with some particles agglomeration. The added particles showed as narrow elliptical bands, with a band pitch equal to the rotation speed over traveling speed. Performing the second FSP pass in the opposite direction resulted in better particles distributions. Almost defect-free composite materials, with homogenously distributed yttria nano-sized particles, were obtained after two passes when rotation speeds more than 700 rpm were used. The resulting steel matrix grains were refined from ~60 μm of the base metal to less than 3 μm of the processed nugget zone matrix. The hardness and the tensile strength of the fabricated materials improved almost two-fold over the base metal. Uniform microhardness values within the nugget areas were observed at higher rotational speeds. The ductility and toughness of the fabricated composites were reduced compared to the base metal.

Simulation of wire and arc additive manufacturing of 308L stainless steel with cold arc gas metal arc welding

This research focuses on the capabilities of coldArc GMAW in the behavior of heat input to the weld bead dimension. In this study, the effect of process GMAW of 308L stainless steel filler wire with a thickness of 1.2 mm and 304L stainless steel base plate, with a dimension of 120 mm x 25 mm x 10 mm (height x width x thickness) by applying WAAM. The data was collected using MATLAB of a Smart Weld Rosenthal’s Steady-State 3D Isotherms. A Taguchi response was used in the DOE method with Minitab software to analyze the effect of process parameters on height, width, and depth of weld bead dimension during GMAW. The experiments were conducted following the low, mid, and high input parameters will show the different structures of weld bead dimension, which include 70 A, 75 A, and 78 A (arc current), 15 V, 16 V, and 17 V (voltage), 400 mm/min, 600 mm/min, and 800 mm/min (welding speed). Hence, the optimum value is 75 A, 16 V, and 800 mm/min, and the most significant parameters to deposit stainless steel with coldArc GMAW were welding speed followed by arc current and voltage.

Contact Surfaces Preparation in Manufacturing of Bimetallic Strips CuZn10 Brass - C22E Steel - CuZn10 Brass

Contact surfaces preparation before cold cladding is one of the most important technological operations. A joint plastic components deformation of the of bimetal 1 according to OST 3-6648-91 and bimetal 3 according to OST 3-6649-91 CuZn10 brass - C22E steel - CuZn10 brass (according to EN standard) should be performed with the strongest possible compression to obtain the required layers connection strength, ensuring strip winding into a roll without delamination. We investigated influence of some factors on the bond strength of bimetal layers: surface hardening of contact surfaces, presence of an underlayer on a steel base, contact surfaces micro geometry, components heating temperature in the deformation zone, diffusion annealing after cladding and a bimetal layers thicknesses ratio effect. Cold cladding technological recommendations have been developed for manufacturing of bimetal 1 according to OST 3-6648-91 and bimetal 3 according to OST 3-6649-91 (CuZn10 brass - C22E steel - CuZn10 brass).