Further Studies into Crack Growth in Additively Manufactured Materials

Understanding and characterizing crack growth is central to meeting the damage tolerance and durability requirements delineated in USAF Structures Bulletin EZ-SB-19-01 for the utilization of additive manufacturing (AM) in the sustainment of aging aircraft. In this context, the present paper discusses the effect of different AM processes, different build directions, and the variability in the crack growth rates related to AM Ti-6Al-4V, AM Inconel 625, and AM 17-4 PH stainless steel. This study reveals that crack growth in these three AM materials can be captured using the Hartman–Schijve crack growth equation and that the variability in the various da/dN versus ΔK curves can be modeled by allowing the terms ΔKthr and A to vary. It is also shown that for the AM Ti-6AL-4V processes considered, the variability in the cyclic fracture toughness appears to be greatest for specimens manufactured using selective layer melting (SLM).

Эрозионные характеристики композитных материалов на основе меди в дуге переменной длины с поперечным продувом газа

We present experimental data on the erosion of electrodes made of copper-based pseudoalloys during contact breaking at current amplitudes up to 150 kA in nitrogen at a pressure of ~2 MPa with transverse gas blowing. The electric-erosion characteristics of copper–iron pseudoalloy CuFe (85/15%) electrodes obtained by laser layer melting, as well as CuFe (70/30%) and CuW (25/75%) pseudoalloy electrodes fabricated by traditional powder technology (sintering of pressed powder compacts) are reported. The specific erosion of electrodes in variable-length arc amounts to ~1 mg/C, which somewhat exceeds the value observed for a fixed-length arc discharge gap.

Application of additive technologies for synthesis of titanium alloys of Ti-Al, Ti-Al-Nb systems of elemental powders

Additive technologies are one of the drivers for development of new industrial revolution. For developing additive production it is necessary to expand the nomenclature of materials used in the form of powders. One of the ways for synthesizing new alloys in additive technologies is applying a mixture of powders as primary components; the powders correspond in their composition to the given alloy. The technology of selective laser melting enables synthesizing the necessary alloy by means of layer by layer melting of a powder mixture. A study of the process of Ti-5Al and Ti-6Al-7Nb titanium alloys synthesis of elemental powders by means of selective laser melting was undertaken in this work. Microstructure, chemical composition, mechanical properties of the synthesized alloys were studied and also the influence of thermal processing on the microstructure of the Ti-6Al-7Nb alloy obtained of elemental powders was explored.

Fatty Acids Profile of the Subcutaneous Backfat Layers from Iberian Pigs Raised Under Free-range Conditions

The aim of this study was to investigate the fatty acid composition of the outer, inner and subinner subcutaneous backfat layers from Iberian pigs raised under free-range conditions. The pigs were fattened on acorns and grass under free-range conditions from 101 to 155 kg of live weight. Proportions of C16:0, C18:0 and C20:0 were lower in the outer than in the inner layer, while the C12:0, C16:0 and C18:0 contents were higher in the subinner layer than in the inner layer. The outer layer had higher C15:1, C16:1 n-7, C17:1, C18:1 n-7 and similar C16:1 n-9, C18:1 n-9 and C20:1 n-9 proportions than the inner layer, while the subinner layer had lower C17:1, C18:1 n-9, C20:1, similar C15:1, C16:1 n-7, C18:1 n-7 and higher C16:1 n-9 proportions than the inner layer. Only the concentrations of C18:3 n-3, C18:4 n-3 and C20:3 n-3 were lower in subinner than in inner layer. The content of all polyunsaturated fatty acids (PUFA) was higher in the outer than in the inner layer except for the C20:4 n-6 fatty acid. A tendency (P < 0.1) to a higher Σ n-6/Σ n-3 fatty acids ratio was found for the inner and subinner layers than for the outer layer. Significant correlation coefficients were observed between the proportions of C14:0, C16:0, C18:1 n-9, C18:2 n-6, C18:3 n-3 and C20:3 n-9 of the inner layer and subinner layer. The outer layer melting point (MP) was lower than those of the inner and subinner layers, although no difference for MP between inner and subinner layers was observed.