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- Resistance spot welding (6)
- Advanced high strength steels (4)
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- Lightweight body shell design (2)
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- Spot welding (2)
Organisationseinheit der BAM
Für die Sicherheit und Gebrauchstauglichkeit von geschweißten Behältern mit Aufdachungen unter Innendruck müssen die Biegezusatzspannungen berechnet oder wirklichkeitsnah abgeschätzt werden. Dazu können verschiedene Verfahren herangezogen werden, die sich in Aufwand, Genauigkeit und zeitlicher Verfügbarkeit des Ergebnisses unterscheiden. Beim Entwurf von Behältern, im Betrieb oder im Schadensfall kommen sie zum Einsatz.
Calculation of ultrasonic reflection and transmission in anisotropic austenitic layered structures
(1999)
Characterization of the microstructure of high-chromium cast irons using Mössbauer spectroscopy
(2001)
The finish grinding process for cement materials uses ball mills with differently sized grinding balls. Because the grinding takes place through the impact and friction of the balls, balls with a high wear resistance are desirable and the materials of choice are the high-chromium white cast irons. This article examines the behavior of these cast irons when subjected to various heat treatments. The emphasis is on the dependence of the microstructure properties on the chemical composition of the alloys and the heat treatment parameters. The content of retained austenite and that of carbon in the martensite phase were determined by the use of Mössbauer spectroscopy. The results verify that a higher proportion of retained austenite with low carbon content and a martensite with higher hardness produce a material with good fracture toughness and resistance to abrasive wear.
In lightweight car body shell mass production, due to requirements on vehicle weight reduction and carbon dioxide emissions, joining of advanced high strength steels (AHSS) with different joining procedures and especially hybrid bonding techniques is becoming more and more important. One of these hybrid bonding techniques is the combination of resistance spot welding and adhesive bonding called weldbonding. One of the important advantages of weldbonded joints in comparison to resistance spot welded joints are the enhanced mechanical properties. To guarantee sufficiently high quality conditions regarding the strength of the weldbonded joints, the influences of the applied adhesive systems and of different base metal combinations are studied. This is carried out for both non-corrosive and corrosive environments and for the choice of different joining parameters settings. In particular, the mechanical behaviour of the weldbonded joints is investigated under quasi-static, impact and fatigue loads. Furthermore, the energy absorption of the weldbonded joints for both non-corrosive and corrosive environments is studied. It is shown that the weldbonded joints possess higher mechanical strengths in all load cases (quasi-static, impact and fatigue). Corrosive attack affects weldbonded joints, and the quasi-static strength is reduced. Resistance spot welded joints are not affected by the corrosive attack, but even after several weeks of corrosive attack, the quasi-static strength of weldbonded joints remains higher than that of resistance spot welded joints.
For spot-welded joints, the resistance to
mechanical stress depends on the local strength properties
and gradients in the weld area. The commonly used
methods for investigating the stress–strain behaviour across
the weld area are connected with a high level of sample
preparation and with considerable limitations in local resolution.
A promising method for determining locally
resolved stress–strain curves is the instrumented indentation
test in connection with the method of representative
stress and strain (RS) and the method of artificial neural
networks (NNs). The stress–strain properties of the weld
nugget and the base metal determined by these two methods
are compared and discussed, additionally in relation to
the stress–strain curves obtained from the tensile test. The
measured Vickers hardness across the weld area is compared
with the evaluated local stress–strain properties.
Three steels used in automobile manufacturing are investigated:
mild steel DC04 and two advanced high-strength
steels (TRIP steel HCT690T and martensitic steel HDT
1200M). The results of the two methods (RS and NN) show
good correspondence for the base metal area but some
significant differences for the weld nugget. Comparing the
data across the weld area, no evidence of the presence of
residual stress (which would influence the results) was
found.