Ultrasonic welding is a very useful and simple welding process. It is suitable for establishing a joint between thin sheets and dissimilar metals with short preparation and finish work time . Some welding defects were detected due to less than optimal ultrasonic welding parameters. These defects were ruptures, surface colour change and unacceptable deformations. This article aims to identify these failures and their causes.
Ultrasonic welding is very useful for joining thin metal sheets [1, 2]. The effect of ultrasound on microstructure is currently not well understood because the changes produced depend very much on the welding parameters and the properties of the metal being considered. Thin sheets formed by cold rolling acquire a special grain structure. During the welding process the heat produced causes recrystallization; even where heat is not applied in the joining process the recrystallization process alters the mechanical properties within the heat affected zone (HAZ). The mechanical properties of the welded samples depend on the microstructure. In this work we analyse the ultrasonic welding effect on the joint and the HAZ [3, 4].
Zoltán Nyikes, Norbert Daruka and Tünde Anna Kovács
Unfortunately, people can’t live in peace in this century: many wars and terrorist attacks have been witnessed even within the last year. In the case of such attacks, both the people and the civil infrastructure is in danger [1-3]. The modern age (infrastructure) provides electrical networks and communication networks for the citizens. Without electricity and/or communications (e.g. the internet), urban life is paralysed. Explosions create heat and shock waves and their effects can potentially damage the wall and cables of a building as changes in the material structure occur. In this article, the authors introduce a blast load effect testing method in an empirical way. The metal microstructure deformation level is measurable by changes in resistance, because resistance is a physical property which depends on the crystal structure of the metal.
In the current century, building protection is very important in the face of terrorist attacks. The old buildings in Europe are not sufficiently resilient to the loads produced by blasts. We still do not fully understand the effects of different explosives on buildings and human bodies. [1–3] Computing blast loads are different from that of traditional loads and the material selection rules for this type of impact load are diverse. Historical and old buildings cannot be protected simply by new walls and fences. New ways need to be found to improve a building’s resistance to the effects of a blast. It requires sufficiently thin yet strong retrofitted materials in order to reinforce a building’s walls [4–6].
It is known that fusion welding can cause a decrease in the corrosion resistance of the heat affected zone of unstabilized stainless steels. The reason for this problem is that the welding heat (in the heat affected zone (HAZ)) can cause chromium-carbide (Cr23C6) precipitation with the simultaneous reduction of chromium content at the local grain boundaries. The chromium content dictates the corrosion resistance level. The relationship between surface roughness and corrosion behaviour is well known. We sought to find the difference between the corrosion resistance and surface roughness relationship in the case of cold rolled stainless steel and in the case of heat treated (welding heat effect simulated) stainless steel [1-3].
Industrially produced rails can contain some inherent failures without evident damage. If a fracture propagates beyond a critical size, it can lead to breakage. The study of fracture mechanics suggests many different theories for detecting the fracture. Continuous monitoring of the rail surface state is necessary in order to assure uninterrupted and safe transportation.