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High power ultrasonic
spot welding is an alternative manufacturing process which recently has been developed for joining automotive bodies. This technique is a very low energy process and forms effective welds in less than a second. The present chapter covers different aspects of High Power Ultrasonic Spot Welding HPUSW technology towards lightweig...
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Citations
... The other main limitations include high energy consumption and the need of consumables [3,4]. Therefore, the development of solid-state processes, like friction stir welding (FSW), friction stir spot welding (FSSW), and ultrasonic spot welding (USW) helped to avoid problems that are related to melting and provide opportunities for dissimilar material welding [5][6][7]. However, FSW and FSSW have the limitations of making "keyhole" and the need to fixture and a long process time [5]. ...
... Therefore, the development of solid-state processes, like friction stir welding (FSW), friction stir spot welding (FSSW), and ultrasonic spot welding (USW) helped to avoid problems that are related to melting and provide opportunities for dissimilar material welding [5][6][7]. However, FSW and FSSW have the limitations of making "keyhole" and the need to fixture and a long process time [5]. ...
... Under the effect of frictional shear forces, surface oxide layers break down and two joining parts approach bare contact and the temperature increases due to friction, and then local welding occurs between the asperities of two faying surfaces. Finally, the spreading of local micro-welds and coalescence results in the creation of a metallurgical bond in the weld spot [5,[7][8][9][10][11]. ...
Open access on: https://www.mdpi.com/2075-4701/9/5/532
The effect of Cu coating metallic interlayer on the weldability, joint strength, and interfacial microstructure during high-power ultrasonic spot welding (HP-USW) of AZ31B Mg alloy has been studied. Interlayered samples exhibited good weldability and they resulted in strong sound joints with nearly the same strength as joints without interlayer, with the distinction of lower energy being required. The Cu interlayer affected the thermal and vibrational properties of the interface, as the maximum interface temperature decreased and approached better uniformity across the weld nugget. The base metal grain structure changed to equiaxed larger grains after ultrasonic welding and a chain of parent metal small grains were observed around the interface. A binary intermetallic compound product of Mg-Cu, which was rich in Mg, has been found around the interface that was diffused toward base metal. According to the electron probe micro-analyzer (EPMA) results, alongside temperature measurements and hardness data, the formation of Mg2Cu is suggested in this region. At the interface centerline, a narrow region was identified that was composed of Mg, Cu, and Al. Complementary transmission electron microscopy analysis estimated that Al-containing reaction product is a ternary alloy of the MgCuxAly type. The dispersion of fine grain intermetallic compounds as discrete particles inside Mg substrate in both interfacial regions formed a composite like structure that could participate in joint strengthening.
Das Gewicht von Fahrzeugkarosserien kann durch den Einsatz von Leichtbauwerkstoffen reduziert werden, in der Massenproduktion ist die Kombination von Aluminium und Stahl besonders interessant. Unabhängig von ihren unterschiedlichen Schmelztemperaturen können Aluminium und Stahl durch das Metall-Ultraschallschweißen im festen Werkstoffzustand energieeffizient, schnell und ohne Zusatzwerkstoffe verbunden werden. Zur Herstellung eines großflächigen Werkstoffkontaktes auf mikroskopischer Skala wird eine Anpresskraft mit hochfrequenten Schwingungen überlagert, die sich in den Bauteilen ausbreiten und bereits vorhandene Schweißpunkte beeinflussen können. In dieser Arbeit wurde daher ein Prozess entwickelt, um die Aluminiumknetlegierung AA6005A-T4 mit dem feuerverzinkt-geglühten Dualphasenstahl HCT980X+ZF100 sowie dem feuerverzinkten, niedriglegierten Stahl HX380LAD+Z100 durch aufeinanderfolgend erzeugte Schweißpunkte zu verbinden. Die zentralen Prozessparameter wurden mithilfe einer statistischen Versuchsplanung ermittelt und auf hohe und gleichzeitig zuverlässige Zugscherkräfte optimiert. Zur Analyse der Fügeprozesse wurden Temperaturmessungen in der Schweißzone, die Zeitverläufe der Leistung des Ultraschallgenerators sowie die Schweißzeiten selbst herangezogen. Ferner wurden licht- und rasterelektronenmikroskopische Untersuchungen inklusive energiedispersiver Röntgenspektroskopie an Quer- und Längsschliffen sowie an Bruchflächen der Schweißverbindungen nach der Zugscherprüfung durchgeführt. Die Prozess- und Verbundeigenschaften wurden sowohl durch die spezifische Position und Reihenfolge der Schweißpunkte als auch durch die Zinkschichten der Stahlbleche beeinflusst. Den Abschluss der Arbeit bildet die Erarbeitung eines Bindungsmodells für das vorliegende Multi-Material-System. Die Erkenntnisse können zur Entwicklung zukünftiger Anwendungen des Metall-Ultraschallschweißens in Aluminium/Stahl-Strukturen mit mehreren Verbindungsstellen beitragen.
