Dataset of dimensionless operating conditions for welding and metal additive manufacturing

The present dataset contains the dimensionless operating conditions obtained by processing a wide range of welding and metal Additive Manufacturing (AM) process parameters through a unified theoretical framework based on the Rosenthal solution [1]. The exploratory data analysis covered Arc and Beam Welding (AW and BW, respectively) on various materials, joint types, and bead sizes ranging from 0.5 to over 10 mm. As for AM, we considered Laser Metal Deposition (LMD) and Selective Laser Melting (SLM) on steel, Al, Ni, Ti, Cu, and Co-Cr alloys by limiting the research to the last five years of published literature

Technological implications of the Rosenthal solution for a moving point heat source in steady state on a semi-infinite solid

This paper introduces a theoretical framework for the analysis and optimization of melting processes that use focused moving heat sources. Specifically, we consider the Rosenthal solution for a moving point heat source in steady state on a semi-infinite solid. Firstly, we analyze the feasibility of the thermal problem while constraining the melt pool size and aspect ratio. We then express the maximum allowable velocity and the corresponding power as explicit functions of the constraints and material properties. Finally, we examine a wide range of melting processes within a dimensionless framework derived from the above solution. The paper concludes with an application example concerning lack of fusion porosity in powder bed fusion additive manufacturing, which shows the reliability of analytical estimates despite the complexity of the underlying physics. This makes it possible to outline a direct procedure for optimizing the main process parameters given a few basic requirements. Ultimately, the proposed methods are not intended to replace other modeling and experimental approaches, but rather to complement their capabilities and encourage more efficient use of available resources. In addition, reframing seemingly different problems within a common perspective can improve understanding, reveal new levels of similarity, and sometimes even allow for global solutions

Design of a non-destructive test for validating models of hydrogen migration.

High-strength steels, despite their excellent mechanical properties in normal conditions, can be susceptible to hydrogen embrittlement. Due to the service loads or residual stresses, hydrogen migrates within the component and accumulates in the regions where the highest tensile hydrostatic stress occurs. As a consequence, component brittle failure can occur even if the initial or mean hydrogen concentration is lower than the critical value. The availability of models predicting the hydrogen diffusion within the component is a crucial task for the design. Several diffusive models have been presented in the literature and some general-purpose finite element codes have implemented some of them. However, the validation of those models is still an open issue due to the difficulty in performing accurate local measurements of the hydrogen concentration. This study deals with the design of a test potentially able to validate hydrogen migration models. In the test, a four-point bending configuration is applied to a properly shaped hourglass specimen, previously charged with hydrogen, extracted from thin high-strength steel sheets. The specimen geometry and the loading configuration were designed to obtain a central region in which the stress and strain field is uniform in plane and exhibits a quasi-uniform gradient in the thickness direction. As a consequence, it is expected a large enough central region of the specimen in which the Hydrogen can migrate only in the thickness direction during the typical duration of the test. The local hydrogen concentration is evaluated by measuring the flux leaving the tensile surface of the specimen by a solid-state hydrogen sensor

Funzione peso per una fessura laterale inclinata e deflessa

In questo lavoro viene presentato un metodo per determinare i fattori di intensità degli sforzi (stress intensity factors SIF) per una fessura di bordo inclinata e deflessa in un semipiano. Il problema è stato affrontato mediante un’analisi parametrica ad elementi finiti che ha permesso di studiare l’influenza dei principali parametri che governano il problema: l’angolo d’inclinazione iniziale, l’angolo di deflessione del segmento terminale della fessura ed il rapporto tra le lunghezze dei due segmenti di fessura. Sulla base dei risultati numerici è stata definita una Funzione Peso (Weight Function WF) con struttura matriciale, estendendo una tecnica mista analitico-numerica già sviluppata per lo studio di fessure di bordo inclinate. La correttezza della WF è stata verificata mediante confronto con i risultati numerici ottenuti per condizioni di carico indipendenti. La WF può essere usata per calcolare i SIF per fessure aventi inclinazione iniziale compresa tra 0° e 60 °, angolo di deflessione rispetto al segmento iniziale tra -90° e + 90° e rapporto di lunghezza tra i segmenti iniziale e terminale compreso tra 0.005 e 0.1

Effetti sulla ripartizione dei carichi dovute alla configurazione dei satelliti in rotismi planetari

La conoscenza della ripartizione dei carichi sulle dentature è di cruciale importanza per la progettazione di rotismi planetari, in quanto permette di evitare che la trasmissione operi in condizioni non conformi alle specifiche, in cui possano avvenire rotture catastrofiche. La ripartizione del carico dipende sia dai parametri funzionali del rotismo (quali gioco dei cuscinetti, backlash, rigidezze dei componenti) sia dal numero di satelliti impiegati. Il presente lavoro mira ad investigare come il numero di satelliti possa influenzare la ripartizione dei carichi applicati a una trasmissione tipicamente impiegata in campo eolico e come questi effetti vengano amplificati oppure attenuati dalla variazione di parametri funzionali (quali il gioco dei cuscinetti, le rigidezze dei supporti e dell’ingranamento, ed il backlash) e dagli errori di montaggio. Lo studio è stato condotto impiegando un modello a parametri concentrati interamente parametrico che permette di identificare condizioni di malfunzionamento quali perdita di contatto e/o incuneamento oltre al carico agente su ciascun ingranamento in funzione dell’insieme dei suddetti parametri. Mappe di ripartizione del carico vengono proposte per rotismi aventi da tre a cinque satelliti.The knowledge of the distribution of loads on the teeth is of crucial importance for the design of planetary gearboxes, since it allows to avoid that the transmission operates in conditions that do not comply with the specifications, in which a catastrophic failure can take place. The load distribution depends both on the functional parameters of the gearing (such as bearing play, backlash, stiffness component) and on the number of planets. This paper aims to investigate how the number of planets will affect the distribution of loads applied to a transmission typically used in wind farms and how these effects are amplified or attenuated by the variation of operating parameters (such as bearing clearance, supports and tooth stiffness, and backlash) and the assembly errors. The study was conducted employing a lumped parameter model parametric spaces that allows to identify fault conditions such as loss of contact and/or wedging in addition to the load acting on each meshing on the basis of all of those parameters. Maps load distribution are proposed for gears having from three to five planets

Mechanical Characterization of Metallic Materials by Instrumented Spherical Indentation Testing

Instrumented indentation testing is now considered one of the most attractive tools for characterizing engineering materials. A large number of materials properties can be investigated. The present dissertation was aimed at developing a new methodology for inferring the material behaviour of metallic materials from their indentation response

HCF assessment of additively manufactured notched specimens in Inconel 718 considering the effective local geometry

Expressing the potential of metal Additive Manufacturing (AM) for components of industrial interest means the ability to produce complex geometries in high-performance materials. AMed components present several notches, both on external and internal surfaces, such as blunt notches, introduced by the designer for functional requirements of the component, or local severe notches and cracks produced by the AM process. Criteria developed for dealing with notches in traditionally manufactured components, such as the Average Strain Energy Density (ASED), have been successfully extended to AMed components in recent years. In the present work, it is analyzed the High Cycle Fatigue (HCF) notch sensitivity as-built cylindrical specimens, including the local geometry and surface roughness in proximity to the notch region. Four geometries of V-notches featuring a radius ranging from 0.3 to 2 mm were considered. Tests were carried out at room temperature in an axial load configuration with a stress ratio of 0.05 and a loading frequency of about 150 Hz, by using a resonant machine. Fractographic analyses were carried out to identify the nucleation and crack propagation region, as well as the presence of the defects in proximity to the fracture onset. The actual geometry in proximity to the notch root was investigated by optical microscopy to extract the local surface profile, including the notch effective geometry and the surface roughness, which was employed to set up a specimen-specific FE model. The results were investigated in the framework of the ASED approach, comparing the prediction obtained using the nominal and the effective notch geometry. Notwithstanding the severe stress concentration caused by the local irregularities introduce by the L-PBF process, the ASED values were found to be almost insensitive to the actual profile geometry. The method was demonstrated to be a valid tool for the design of AMed complex-shaped components

Elasto-plastic behavior of a Warrington-Seale rope: Experimental analysis and finite element modeling

The mechanical behavior of Warrington-Seale (WS) strands as well as of a Warrington Seale rope with a polymeric fiber core is investigated. Specifically, the elasto-plastic response under axial loading conditions beyond the elastic limit is studied. Tensile tests were carried out on both WS strands and ropes. The strain-stress curves of single wires with different diameters were determined and used as input of a fully parametric Finite Element (FE) study aimed at investigating the stress and strain evolution in the rope in the elastic as well as in the elasto-platic regime. The numerical simulations, validated on the basis of the experimental results, are useful to shed light on the way the load is distributed among the wires. The different damage evolution and the most likely failure mechanisms of strands and of ropes were identified. Helpful remarks are drawn about the structural response of these components under heavy loading conditions

Impact of process parameters on the dynamic behavior of Inconel 718 fabricated via laser powder bed fusion

In this research, we investigate the dynamic behavior of Inconel 718 fabricated through laser powder bed fusion (L-PBF), addressing a notable knowledge gap regarding the correlation between process parameters and dynamic properties. The process parameters adopted are deducted from an extension of the Rosenthal solution, formulated to increase the process productivity while avoiding the typical production process defects. The dynamic Young modulus and the structural damping of the material are estimated as a function of the process parameters through ping tests reproducing the flexural vibrations of the specimens in as-built, solutioned, and aged conditions. The microstructure and porosity are investigated through metallographic analyses. The results show a substantial influence of the L-PBF process parameters on the dynamic Young modulus, which markedly increases as the energy density is reduced (23%) and progressively becomes more similar to the conventionally produced material. This influence stands in stark contrast to the relatively modest impact of heat treatments, which underlines a negligible effect of the process-induced residual stress. The structural damping remained approximately constant across all test conditions. The elastic response of the material is found to be primarily influenced by the different microstructures produced as the L-PBF process parameters varied, particularly in terms of the dimensions and shape of the solidification structures. The unexpected relationship between the dynamic Young modulus, energy density, and microstructure unveils the potential to fine-tune the material's dynamic behavior by manipulating the process parameters, thereby carrying substantial implications for all the applications of additively manufactured components susceptible to significant vibratory phenomena