Tamás Markovits

Research on the thermo-physical process of laser bending

Abstract This paper presents a new method of real-time measuring technology to reveal the thermo-physical process of laser bending. The dynamic micro-deformation of the specimen is measured using a laser beam reflex amplifier system. Experimental results show that the common action of thermal stress and phase transformation stress makes the specimen bend. The final deformation direction of the specimen depends on the result of the co-operation of the thermal strain and the phase transformation strain, away from the laser beam or towards the laser beam. The conclusion lays the foundation for further research on the process of laser bending.

Adhesion of Steel and PMMA by Means of Laser Radiation

As the utilization of plastics is growing in our devices, their joining with other structural materials, like metals is more and more necessary. A novel method for joining polymeric materials and metals is the laser assisted metal plastic joining. The method is in focus of several researches. However, the mechanism of joint formation is not described sufficiently yet. In this study, the adhesion between structural steel and PMMA plastic and the phenomena of bubble formation is investigated. Scanning electron microscopy (SEM), thermogravimetry and mass spectrometry (TG-MS) were used to analyze joining interfaces and changes in the plastic material. Results show good adhesion between the mentioned materials and the important role of bubbles in the evolution of joining force.

Hybrid joining of steel and plastic materials by laser beam

Hybrid joining of metals and plastics in order to produce lightweight parts is of growing interest in the manufacturing processes of vehicles, electrical devices and biomedical applications. In this study, the joining of PMMA plastic (poly methyl metacrylate) and unalloyed steel were investigated by the authors. The authors successfully joined PMMA and steel by means of Nd:YAG laser and carried out tensile tests to measure the joining strength. Experimental results showed that the joint strength is influenced by the heating time, the penetration depth of the steel workpieces in the plastic, by the surface roughness of steel and by the time elapsed between bonding and tearing of the samples.

Investigation of Laser Brazing of Aluminium

Use of aluminium materials has increased in the vehicle industry in the last years due to their low weight. Machining of aluminium by industrial lasers is a more complex task than that of steel because of the lower absorption, higher heat conduction, higher heat capacity and oxide layer on the surface. The low absorption ability of the Al surface can be significantly improved by using appropriate brazing flux suspension on the wavelength of CO2 lasers. In this paper the role of brazing flux components and their influence are investigated in the heating efficiency in case of Nd:YAG lasers, which are widely used in the laser joining technology. This research work presents the differences between the effects of the brazing flux in case of CO2 and Nd:YAG lasers.