Meri Burzić

The effect of welding process and shielding atmosphere on the AlMg4.5Mn weld metal properties

Abstract In this paper, the AlMg4.5Mn alloy has been welded using tungsten inert gas (TIG) and metal inert gas (MIG) processes with different gas shielding atmospheres. Tensile strength, hardness, impact and fracture toughness, fatigue crack growth parameters (ΔKth, da/dN), as well as microstructure were determined. By comparing results for different gas mixtures, the main conclusion for TIG welding was that increased helium content has an important effect on toughness and fatigue crack growth parameters, whereas its effect on other mechanical properties is not significant. On the other hand, in the case of MIG welding, adding helium does not affect mechanical properties, except the fatigue crack growth rate. It was also established that adding nitrogen (TIG welding) and oxygen (MIG welding) reduces toughness and increases crack growth rate, so their use in shielding mixtures is not recommended.

3D Experimental optical analysis of titanium alloys for biomedical applications

In this paper is presented an example of experimental analysis of biomaterials based on optical measurement methodology. GOM optical system and Aramis software were used to perform 3D experimental optical analysis of titanium alloys for biomedical applications. The possibilities of using this method for analyzing materials for biomedical applications are discussed, and having in mind that the system used in this experimental analysis is utilized to solve problems in structural integrity analysis and determining properties of materials, it is concluded that this method is suitable for analysis of irregular object geometries made of various materials, as is often the case in biomedical applications. Considering that titanium alloys have high sensitivity to fatigue induced by notches, a sharp-notch tension test was performed. The goal of this in vitro study was to measure and analyze fracture behaviour of Ti6Al4V alloy specimens. The major strain field of the titanium alloy specimen for crack tip opening and fracture are presented. It is shown that the application of a modern 3D optical measuring method is useful in determining some of the key properties of metallic materials in biomedical applications.

Effect of Microalloyed Steel Welding Procedure on Fatigue Crack Growth

The application of high strength steel, e.g. NIOMOL 490K, developed for highly loaded welded structures and low temperatures, depends on properties of welded joint critical regions. Strength, toughness and crack resistance of welding joints have to be tested. Fatigue crack growth rate is defined by relation of stress intensity factor range, δK, induced by variable loading and crack extension for one cycle, da/dN. For that precraked specimen has to be tested [1]. Samples for investigation had been prepared by metal manual arc welding (MMAW) and MAG welding. Two plates of 16 mm thick NIOMOL 490K steel of nominal yield stress 490 MPa [2], had been prepared for asymmetric 2/3 X welded joint by edge machiningInitial notch for fatigue crack growth rate testing was machined in weld metal and HAZ [3].