Paweł Kustroń

Friction Welding of Aluminium and Aluminium Alloys with Steel

The paper presents our actual knowledge and experience in joining dissimilar materials with the use of friction welding method. The joints of aluminium and aluminium alloys with the different types of steel were studied. The structural effects occurring during the welding process were described. The mechanical properties using, for example, (i) microhardness measurements, (ii) tensile tests, (iii) bending tests, and (iv) shearing tests were determined. In order to obtain high-quality joints the influence of different configurations of the process such as (i) changing the geometry of bonding surface, (ii) using the interlayer, or (iii) heat treatment was analyzed. Finally, the issues related to the selection of optimal parameters of friction welding process were also investigated.

Real-time ultrasonic control of spot-welded steel joints

Resistance welding is a welding method where the joining of materials is achieved by heating the contact area of the pieces to be joined with an electric current and pressure from plastic strain in the area of the weld. The process of heating workpieces in resistance welding occurs as a result of heat generated by the resistance of the welding current running through the workpieces. Spot welding is a process of joining overlapping workpieces between electrodes, which clamp the pieces together and pass the welding current on to heat the contact area (or ‘spot’) to the proper welding temperature (above the melting temperature). Because this process is quick, simple and effective, spot-welded joints are commonly applied in the automotive industry. Although the welds are usually made at robotized welding stations, they may still show some defects. Fundamental factors having a negative effect on spotwelded joints include:

Ultrasonic quality control methods for spot-welded joints

Spot resistance welding is the most popular method of connecting the steel structures of automotive vehicles. At a time when quality requirements relating to finished goods are higher and higher, welded joints must undergo precise controls in order to assure the highest safety standards possible. Ultrasonic methods enable quick and accurate assessment of any welded joints quality, and at the same time are environmentally friendly. Three ultrasonic applications that make it possible to determine the quality of a welded joint were discussed in the article: testing of joints welded by a single welding head, scanning acoustic tomography, and the resistance spot welding analyzers system – with the application of a mosaic head. The advantages and drawbacks of individual systems were described based on our own experience.

Testing of thin-walled steel joints fabricated by spot welding and plug welding

Selected methods of joining which can be used for manufacturing and repairing of car bodies by means of welding are presented in this article. Three kinds of 1 mm-thick steel sheets were used in the tests: deep drawing steel (DC04) and two-phase steels of increased high strength (DP600 and DP800). The comparative connections were carried out by means of resistance spot welding and with plug joints made by means of the MAG method and through braze welding. Comparative assessment of the strength and geometrical parameters of the test joints was then conducted.

IN‐LINE ULTRASONIC INVESTIGATION OF SPOT WELD QUALITY USING MULTI‐TRANSDUCER SET‐UP

This article presents one of the most recent developments in real‐time ultrasonic quality control methods for resistance spot welds. Currently existing in‐line systems use single‐element transducer to characterize the spot weld quality. The new set‐up is based on 8 ultrasonic transducers placed in one line above the center of the spot weld. The solution presented in this paper makes another step forward towards improvement of accuracy of measurements using array of ultrasonic transducers.

Magnetorheological composites as semi-active elements of dampers

An original magnetorheological composite (MRC) with porous elastomeric matrix and filled with magnetorheological fluid was created at the work. It was used later on to build a damper working in the shearing mode without friction against external surfaces of the so-called skid. This prototype construction was used for damping free vibrations in the beam. An analysis of the effectiveness in the magnetic field function steering the damper was performed. As a result an important relationship between the change of damping in the material under the influence of the magnetic field and the length of time needed for damping the vibrations in the beam was demonstrated.

A high frequency ultrasonic imaging of welded joints

The paper presents chosen results obtained during the investigation of welded joints (laser, spot and friction) tested using acoustic microscopy method. Detection of welds properties and the defects strongly depends on ultrasonic transducers parameters. For the purpose of this research a prototype hardware setup was built - enabling evaluation of various types of ultrasonic probes. The system can be easily adjusted to the geometry of an object and is well equipped with appropriate software for the analysis and processing of images such as B-scan or C-scan. The setup enables determination of welds geometry, in particular the depth of the weld penetration in some cases.

Assessment of the quality of spot-welded joints by ultrasonic testing

Resistance welding is a welding method in which bonding is effected by heating the area of contact between the elements by electric current in combination with deformation of this zone by compressive force. The heating of elements in question occurs because of the generation of heat by the electrical resistances of the circuit during the passage of the current. Spot welding is a process used for the overlap-bonding of elements located between electrodes which also supply welding pressure and conduct the heating current. In turn, this raises the temperature of the contact area to the welding level (i.e. in excess of the melting point). The spot-welding method can be used for the bonding of two or three plates. During the welding on a pressurewelding machine, a number of pressure welds can be deposited at the same time. Because of their effectiveness, speed of deposition, and simplicity of the process, pressure bonds have found a wide range of applications in the car industry. Despite the fact that they are usually made on robotized, pressure welding stands, they may still be subject to some defects. The main factors likely to affect negatively the produced spot-weld joints are: