In situ ultrasonic testing for wire arc additive manufacturing applications

In this paper, we present a non-destructive testing (NDT) technique based on in situ detection of defects up to 100 °C by ultrasonic testing (UT) during construction of parts by a metal additive manufacturing technology known as wire arc additive manufacturing (WAAM). The proposed technique makes use of interlayer application of commercial solder flux to serve as coupling medium for in situ inspection using a special-purpose UT probe. The experimental work was carried out in deposited ER5356 aluminum straight walls following a threefold structure. First, characterization tests with geometrically similar walls with and without interlayer application of solder flux highlight its neutrality, with no effect on the chemical, metallurgical and mechanical properties of the walls. Secondly, UT tests on walls at temperatures ranging from room temperature to 100 °C demonstrate the satisfactory performance of the solder flux as a coupling medium, with little to no soundwave amplitude losses or noise. Finally, acoustic attenuation, impedance and transmission estimations highlight the effectiveness of the proposed technique, establishing a basis for the future development of automated NDT systems for in situ UT of additive manufacturing processes.info:eu-repo/semantics/publishedVersio

A software for research and education in ductile damage

This paper gives insight into the development and utilization of a computer software that uses raw experimental data from the load cells and DIC systems to obtain the instant of time at fracture tf, the loading paths in principal strain space ε1=f(ε2), and their conversion into the space of effective strain vs. stress triaxiality ε‾=f(η). Special emphasis is given to the different assumptions and stress triaxiality measures that can be used to convert the loading paths from principal strain space into the space of effective strain vs. stress triaxiality. Results for double-action radial extrusion show the differences of treating the loading paths as linear or non-linear from beginning until the onset of failure by fracture. Results also allow concluding on the importance of accounting for the stress triaxiality derived from individual experimental measurements in an average sense over the entire loading paths, to avoid overestimation and mislocation of the fracture forming limits. The applicability of the software for education and training of students in formability is also discussed

Modelling of wire-arc additive manufacturing – A review

This paper is focused on wire-arc additive manufacturing and has a twofold objective. First, to deliver an overall state-of-the-art review of the different aspects of modelling. Second, to provide a detailed analysis of the macro-scale finite element modelling. The methodology draws from the fundamentals of the macro, meso and micro-scale modelling of the process, to the main strategies and objectives behind the development of analytical, statistical, machine learning and finite element analyses of macro-scale modelling. The intention is to provide information on the pre-processing requirements, solution techniques and results that are currently being worked on by some of the leading researchers in the field. This will enable readers to understand the main challenges, relevance, and assumptions of the different published works. The theoretical and numerical aspects are intentionally kept in a clear and understandable level so that users of finite element computer programs having the know-how on wire-arc additive manufacturing can bridge the actual gap to the developers of the programs

Injection lap riveting of aluminum busbars — a thermo-electro-mechanical investigation

This paper presents a new mechanical joining process to assemble aluminum busbars in energy distribution systems. The process is based on the extension of injection lap riveting to the connection of busbars made from the same material as the rivets and requires redesigning the joints to ensure complete filling with good mechanical interlocking and appropriate contact pressures on the overlapping area. The experimental work was carried out in unit cells and involved the fabrication of the riveted joints and the evaluation of their electrical resistance at different service temperatures. Comparisons with the bolted joints that were fabricated and tested for reference purposes show that injection riveted joints provide lower values of electrical resistance and require much less space for assembly due to the absence of material protrusions above and below their surfaces. Numerical simulation with finite elements allows the relating of the reduction in electrical resistance with the changes in the electric current flow when the bolts are replaced by the new type of rivets. The experimental and numerical predictions revealed that the new type of rivets experience an increase in electrical resistance of up to 6 μΩ (30%) when the service temperature approaches 105 °C. Still, the resistance at this temperature (26.2 μΩ) is more than 3 times smaller than that of the bolted joints (80.5 μΩ).info:eu-repo/semantics/publishedVersio