Laserstrahlschweißen von Stahl und Titan hoher Blechdicke unter dem Einfluss eines lokal reduzierten Umgebungsdruckes
Notice bibliographique
Résumé
The increasing power of the laser beam sources allow a continuous expansions of applications, particularly for metals with high thickness. Due to the increase of the power, a number of negative effects arise which can adversely affect the welding result. That is particularly important for the metal vapour plume, that forms due to the high temperature in the keyhole and evolves in direction of the laser beam axis. The usable laser beam power is thus decreased and thereby the available power for the welding process declines as well. A suppression of the vapour plume is possible, with the help of an applied vacuum. Thereby, the complete amount of laser beam power is available for the welding process. This has positive effects on the welding depth and the weld quality. The limiting factor is the size of the vacuum chamber, which is adapted to the component to be welded. The aim of this study was to make the vacuum technology available independently of the component size. The patented pending vacuum cap presented in this thesis is placed at the welding area and movable in welding direction. The positive influence of the vacuum is used during the welding process, but it is not limited by the component size. The used local vacuum device has been specially designed for the available laser system, designed by CAD and manufactured afterwards. Instead of being made of glass, an aerodynamic window was used as a boundary layer between the ambient pressure and the vacuum region. For the design of the Laval nozzle in the aerodynamic window, a Schlieren test stand has been developed to make the stream visible. The positive influence of the welding under vacuum to the weld pool is independent of the composition of the material. However, the effect of the vacuum is stronger for some alloys compared to others. Steel was readily welded already under atmospheric conditions, whereas welding of titanium alloys succeeds only with high complexity of the shielding gas supply. For this reason, significant effects were expected for the titanium alloy. Therefore, the focus of this work lies on the titanium alloy Ti3Al2,5V. Previously, it was not possible to weld material thicknesses of 20 mm with satisfactory quality with a 20 kW fiber laser. Piineering tests were carried out on different thicknesses of S235 and S355. The great potential of this method was already shown for these structural steel types. The welding depths were increased by around 30 % to 50 % compared to the welding under atmospheric pressure. The transfer of the results on the titanium plates showed similar results. Again, a significant increase in the penetration depth up to 75 % can be observed under the influence of the local vacuum. Thus it was possible to weld thick titanium plates up to 28 mm with using fiber lasers.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
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 | 0,001 | 0,000 |
| Communication savante | 0,001 | 0,001 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,006 | 0,001 |
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 ».