Characterization of Micro-Plasma Wire Arc Additive Manufacturing: Anisotropy and Layer Height Investigation
Notice bibliographique
Résumé
Directed energy deposition describes the process of deposition of molten metal in wire or powder form with a focused energy beam source in a layer-by-layer fashion to create a final part. The use of an arc as heat source and wire as feedstock material for directed energy deposition, also known as wire arc additive manufacturing, has become increasingly popular in recent years due to its high productivity, high versatility, availability, cost, and its ability to produce large and complex parts. \nHowever, due to the additive nature of the process and the high heat input involved, anisotropy is a recurring problem arising in printed parts, which leads to different tensile properties in the travel and build directions. Hence, the first section of this work looks into the mechanical properties and microstructures of a thin-walled AISI316LSi austenitic stainless-steel component fabricated by wire arc additive manufacturing using the micro-plasma arc welding process, which is a low heat input process. While properties were mainly uniform, the effect of anisotropy was found to have a significant influence on the modulus of elasticity, with values ranging from 79.5±6.8 GPa along the build direction to 105.2±20.7 GPa in the travel direction. This difference was found to be due to the strong preferential orientation of grains during solidification along the direction corresponding to the build direction, which was also confirmed by electron back scatter diffraction. This was also confirmed by theoretical calculations. \nThe second portion of the work deals with the investigation of the effect of vibratory weld conditioning on the grain size for titanium and stainless-steel layers using the current process. This was motivated by the need to break down the orientation of columnar grains witnessed and transform them into random equiaxed grains. Tests were conducted through the deposition of five layers for each material and the use of a shaker device and a signal generator, which was used to conduct tests based on v-square waves with different amplitudes and frequency ranges. Results revealed that fine grains were achieved when close to the substate, while only frequency was found to have a significant effect on secondary dendrite arm spacing and grain size for stainless-steel and titanium, respectively. \nThe final section of this work deals with correcting layer height deviations, which arise as a result of the heat accumulation of the wire arc additive manufacturing process. The performance of the automatic voltage control, which automatically adjusts the Z-position of the torch during deposition based on arc voltage measured, was initially investigated based on gain and correction speed. Results revealed very high correlations between Z-position and bead height, particularly for a gain of 1.0 (R=0.96) and a max speed of 65 mm/min (0.995). This proved the high reliability of the automatic voltage control when maintaining the voltage measured with the desired voltage but still does not account for surface inconsistencies. Hence, layer height deviations were measured and corrected with an accuracy of 0.03 mm through the modification of the wire feed speed, obtained by determining the exact volume of material added during deposition for different wire feed speeds. Also, in this section, optimal bead overlay parameters were determined based on best fusion and flat surface, revealing to be 15 % for substate welding and 25 % for subsequent layer deposition.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».