Welding process monitoring applications and industry 4.0

With the fourth industrial revolution in progress, traditional manufacturing processes are being transformed. Fusion welding is no exception from this transformation. The centuries-old manual craft is being reshaped by cyber-physical systems, turning into a digitized process governed by industrial informatics. By implementing process monitoring in welding applications invaluable data are collected that can be utilized in the new, futuristic smart factories of Industry 4.0. In this article two purposes are being served. The first is to present the status quo alongside the future trends of welding process monitoring on industrial implementation. The second is to present the results of an ongoing investigation of robotic Gas Tungsten Arc Welding (GTAW) monitoring for defect detection and characterization. Deviations from the optimal values in three welding conditions (surface integrity, shielding gas flow rate and surface contamination) were introduced during stainless steel 316L beads-on-plates welding. Acquired data during the welding process were used to extract features in order to identify correlations between the disturbances and the monitored signals

Current mode effects on weld bead geometry and heat affected zone in pulsed wire arc additive manufacturing of Ti-6-4 and Inconel 718

For the last decade, additive manufacturing (AM) has been revolutionising the aerospace industry, building and repairing various components for aircrafts and outer space vehicles. Despite the fact that AM is gaining rapid adoption by the industry, it is still considered a developing technology, with ongoing research in a variety of fields. Wire arc additive manufacturing (WAAM), a welding-based AM technology, is an active field of research as well, because it enables economical production of large-scale metal components with relatively high deposition rates. In this article, the effects on the weld-bead geometry and heat affected zone from high and low frequency pulsed current are explored on Gas Tungsten Arc Welding (GTAW). The materials used in this investigation were selected to be Ti-6-4 and Inconel 718, both highly used in the aerospace industry for their high strength-to-weight ratio and strength at elevated temperatures respectively. The design of the experiments followed a Taguchi-inspired orthogonal array, altering, apart from the current modes and values, the torch travel speed driven by an industrial robotic arm as well as the wire-feeding rate. The results demonstrate the ability to control both the weld-bead dimensions and penetration depth, as well as the heat affected regions, by utilizing the dual pulsing combination of both high and low frequency pulsing. Alterations from wide beads with deep penetration to narrower beads with greater height-to-width ratios are demonstrated in a single manufacturing setup, enabling further development of the WAAM process

D(3He,p)4He and D(d,p)3H fusion in a small plasma focus operated in a deuterium helium-3 gas mixture

Abstract A 3 kJ plasma focus was operated with a 3He-D2 gas mixture, with partial pressures in the ratio of 2:1, corresponding to an atomic number ratio of 1:1 for 3He and D atoms. The fusion reactions D(3He,p)4He and D(d,p)3H were measured simultaneously using CR-39 polymer nuclear track detectors placed inside a pinhole camera positioned on the forward plasma focus axis. A sandwich arrangement of two 1000 mi m thick CR-39 detectors enabled the simultaneous registration of two groups of protons with approximate energies of 16 MeV and 3 MeV arising from the D(3He,p)4He and D(d,p)3H reactions, respectively. Radial track density distributions were obtained from each CR-39 detector and per-shot average distributions were calculated for the two groups of protons. It is found that the D(3He,p)4He and D(d,p)3H proton yields are of similar magnitude. Comparing the experimental distributions with results from a Monte Carlo simulation, it was deduced that the D(3He,p)4He fusion is concentrated close to the plasma focus pinch column, while the D(d,p)3H fusion occurs relatively far from the pinch. The relative absence of D(d,p)3H fusion in the pinch is one significant reason for concluding that the D(3He,p)4He fusion occurring in the plasma focus pinch is not thermonuclear in origin. It is argued that the bulk of the D(3He,p)4He fusion is due to energetic 3He2+ ions incident on a deuterium target. Possible explanations for differing spatial distributions of D(3He,p)4He and D(d,p)3H fusion in the plasma focus are discussed

Multiscale microstructural heterogeneity and mechanical property scatter in Inconel 718 produced by directed energy deposition

Directed energy deposition (DED) is an additive manufacturing technique that enables rapid production and repair of metallic parts with flexible geometry. The complex nature of thermal and material transport during DED can yield unwanted microstructure heterogeneity, which causes scatter in parts performance. Here, we investigate microstructure variations at different length scales in Inconel 718 produced by powder-blown DED using different deposition rates. We quantify spatial trends in grain structure, texture, composition, and solidification structure within parts and correlate them with variations in hardness, yield strength, and Young's Modulus to highlight the effect of the thermal environment during solidification. We find that the high energy input employed when using high deposition rates is conducive to significant microstructure heterogeneity along both the build and transversal directions, which stems from the asymmetric cooling rates generated by the deposition strategy used. We also find that standard heat treatments employed on Inconel 718 are not suitable to homogenize the microstructure. These results have important implications for the development of industrially relevant build rate strategies for additively manufactured parts

Low-frequency acoustic shielding by the Silent Aircraft airframe

The Silent Aircraft airframe has a flying-wing design with a large wing planform and a propulsion systemembedded in the rear of the airframe with intake on the upper surface of the wing. In the present paper, boundaryelementcalculations are presented to evaluate acoustic shielding at low frequencies. Besides the three-dimensionalgeometry of the Silent Aircraft airframe, a few two-dimensional problems are considered that provide some physicalinsight into the shielding calculations. Mean-flow refraction effects due to forward-flight motion are accounted for bya simple time transformation that decouples the mean-flow and acoustic-field calculations. It is shown that asignificant amount of shielding can be obtained in the shadow region where there is no direct line of sight between thesource and observer

Characteristics of CVD diamond films in detecting UV, x-ray and alpha particle

International Journal of Modern Physics B166-71018-1023IJPB