Weld bead detection based on 3D geometric features and machine learning approaches

14 p.Weld bead detection is essential for automated welding inspection processes. The non-invasive passive techniques, such as photogrammetry, are quickly evolving to provide a 3D point cloud with submillimeter precision and spatial resolution. However, its application in weld visual inspection has not been extensively studied. The derived 3D point clouds, despite the lack of topological information, store significant information for the weld-plaque segmentation. Although the weld bead detection is being carried out over images or based on laser profiles, its characterization by means of 3D geometrical features has not been assessed. Moreover, it is possible to combine machine learning approaches and the 3D features in order to realize the full potential of the weld bead segmentation of 3D submillimeter point clouds. In this paper, the novelty is focused on the study of 3D features on real cases to identify the most relevant ones for weld bead detection on the basis of the information gain. For this novel contribution, the influence of neighborhood size for covariance matrix computation, decision tree algorithms, and split criteria are analyzed to assess the optimal results. The classification accuracy is evaluated by the degree of agreement of the classified data by the kappa index and the area under the receiver operating characteristic (ROC) curve. The experimental results show that the proposed novel methodology performs better than 0.85 for the kappa index and better than 0.95 for ROC area.S

Wire Arc Additive Manufacturing of Mn4Ni2CrMo Steel: Comparison of Mechanical and Metallographic Properties of PAW and GMAW

Wire arc additive manufacturing, WAAM, is a popular wire-feed additive manufacturing technology that creates components through the deposition of material layer-by-layer. WAAM has become a promising alternative to conventional machining due to its high deposition rate, environmental friendliness and cost competitiveness. In this research work, a comparison is made between two different WAAM technologies, GMAW (gas metal arc welding) and PAW (plasma arc welding). Comparative between processes is centered in the main variations while manufacturing Mn4Ni2CrMo steel walls concerning geometry and process parameters maintaining the same deposition ratio as well as the mechanical and metallographic properties obtained in the walls with both processes, in which the applied energy is significantly different. This study shows that acceptable mechanical characteristics are obtained in both processes compared to the corresponding forging standard for the tested material, values are 23% higher for UTS and 56% for elongation in vertical direction in the PAW process compared to GMAW (no differences in UTS and elongation results for horizontal direction and in Charpy for both directions) and without significant directional effects of the additive manufacturing technology used.This research was funded by BASQUE GOVERNMENT, grant number KK-2018/00115 (ADDISEND, ELKARTEK 2018 programme) and grant number ZE-2017/00038 (HARITIVE, HAZITEK 2017 programme)

The current state of research of wire arc additive manufacturing (WAAM): a review

Wire arc additive manufacturing is currently rising as the main focus of research groups around the world. This is directly visible in the huge number of new papers published in recent years concerning a lot of different topics. This review is intended to give a proper summary of the international state of research in the area of wire arc additive manufacturing. The addressed topics in this review include but are not limited to materials (e.g., steels, aluminum, copper and titanium), the processes and methods of WAAM, process surveillance and the path planning and modeling of WAAM. The consolidation of the findings of various authors into a unified picture is a core aspect of this review. Furthermore, it intends to identify areas in which work is missing and how different topics can be synergetically combined. A critical evaluation of the presented research with a focus on commonly known mechanisms in welding research and without a focus on additive manufacturing will complete the review

Symmetry and its application in metal additive manufacturing (MAM)

Additive manufacturing (AM) is proving to be a promising new and economical technique for the manufacture of metal parts. This technique basically consists of depositing material in a more or less precise way until a solid is built. This stage of material deposition allows the acquisition of a part with a quasi-final geometry (considered a Near Net Shape process) with a very high raw material utilization rate. There is a wide variety of different manufacturing techniques for the production of components in metallic materials. Although significant research work has been carried out in recent years, resulting in the wide dissemination of results and presentation of reviews on the subject, this paper seeks to cover the applications of symmetry, and its techniques and principles, to the additive manufacturing of metals.The authors are grateful to the Basque Government for funding the EDISON project, ELKARTEK 2022 (KK-2022/00070)

Microstructure and mechanical properties of Ni-Cu alloys fabricated using wire arc additive manufacturing

Ni-Cu alloys, also known as Monel alloys, are widely used in marine industry due to their high corrosion resistance and good mechanical properties. Submarine propeller shafts, diesel engine piston rods and centrifugal pump shafts are examples of application of these alloys. Despite their good mechanical and corrosion resistant properties, Ni-Cu components may fail in operation via sliding wear, galling and pitting corrosion. Since the Ni-base alloys are expensive, repair is often an economic choice than replacement. A possibility to use wire arc additive manufacturing (WAAM) technology for fabrication of new and repair of used Ni-Cu components was assessed in this thesis. Two Ni-Cu wires with various Ti, Mn, Al and C contents were deposited on a Ni-Cu substrate with a wide range of welding parameters (travel speed, wire feed rate). The solute atom concentrations and particle number density values were modified using various post processing heat treatment schedules. A comprehensive study of the microstructure, mechanical properties, wear and corrosion resistance of the Ni-Cu alloy components fabricated using WAAM has been conducted. Microstructure characterisation, in particular a detailed study of the precipitate’s parameters (size, number density and chemical composition) was carried out using optical, scanning, transmission and atomic resolution electron microscopy. Mechanical properties were assessed using hardness, tensile testing to fracture, wear and corrosion resistance