Lukáš Zuzánek

Influence of Deformation on the Damage of Zn-Mg Based Protective Coating

These days are in the automotive industry going to be still more and more used new types of protective coatings on the Zn-Mg basis. The advantage of these coatings is their excellent protection against corrosion of basic material. On the other hand disadvantage is mainly their low formability which takes effect at own stamping process. Such paper deals with the research influence of the deformation on the damage process of this coating. Size of deformation at different stress states was measured with the help of photogrammetry (system ARAMIS). Coating damage process at these stress states was monitored by means of optical and electron microscopy. Results of protective coating Zn-Mg damage process are presented in the form of strain distribution maps and images from optical and electron microscope.

SPRING-BACK PREDICTION FOR STAMPINGS FROM THE THIN STAINLESS SHEETS

The metal forming technology is (mainly due to the automotive industry) one of the most dynamically developing branch of the engineering industry. Continuous effort to achieve the top technological level and car ́s safety factor at keeping the low price level means necessity to still implement into the own production process the newest mathematical models of these technological processes. Thus these days represents utilization of the numerical simulations an essential part for the car shape lay-out design, for determination the basic technological operations and also e.g. for stamping tools shape optimization. Alongside such implementation of the newest materials into production reveals necessity to develop new and more precise computational models of materials deformation behavior as well as models designed for spring-back prediction. Nowadays, in the branch of the metal forming technologies, there are several truly top software among which also belongs software PAM-STAMP 2G. In this article is evaluated influence of the computational model on the numerical simulation accuracy by PAM-STAMP 2G at the spring-back prediction. For the deformation analysis it was chosen stainless sheet material DIN 1.4301 and for the spring-back prediction were used two anisotropic computational models termed as Hill-48 and Vegter in combination with the kinematic hardening model termed as YOSHIDA UEMORI. Accuracy of the measured results from the individual computational models is evaluated by the compliance of the carried out experiment and results from the numerical simulations. For the own experiment was chosen test where material is drawn over the drawbead and drawing edge.

TEMPERATURE INFLUENCE ON THE CHANGE OF THE SANDWICH MATERIAL ADHESIVE PROPERTIES

The automotive manufacturing represents one of the most developing segments of the engineering industry. The persisting tendency of designers to achieve the best technological level, car ́s safety level and also ecological running at keeping the low price level means necessity to still implement into own production new types of materials. Among these materials also belong so-called sandwich materials which combine steel sheets with the plastic core. These materials are used in the car design due to their lower weight and excellent acoustic properties. As a disadvantage of such materials there is lower temperature stability and worse technological processability. This paper deals with the evaluation temperature influence on the change of the sandwich material mechanical properties. For tests there were selected the characteristic mechanical tests for different loading types in light of the adhesive properties testing – the lap shear test and the T-peel test. The range of the testing temperature was from -40°C up to 80°C and was chosen with respect to the commonly used criterions for temperature resistivity of parts designed for the car-body design.

X-Ray Diffraction Analysis of Steel with Oxidised Surface Layer

The basic principle of the X-ray diffraction analysis is based on the determination of components of residual stresses. They are determined on the basis of the change in the distance between atomic planes. The method is limited by a relatively small depth in which the X-ray beam penetrates into the analysed materials. For determination of residual stresses in the surface layer the X-ray diffraction and electrolytic polishing has to be combined. The article is deals with the determination of residual stress and real material structure of a laser-welded steel sample with an oxide surface layer. This surface layer is created during the rolling and it prevents the material from its corrosion. Before the X-ray diffraction analysis can be performed, this surface layer has to be removed. This surface layer cannot be removed with the help of electrolytic polishing and, therefore, it has to be removed mechanically. This mechanical procedure creates “technological” residual stress in the surface layer. This additional residual stress is removed by the electrolytic polishing in the depth between 20 and 80 μm. Finally, the real structure and residual stresses can be determined by using the X-ray diffraction techniques.

X-Ray Diffraction and Barkhausen Noise Diagnostics of Thick Welds Prepared by Metal Active Gas and Laser Welding

Non-destructive methods for detection and measurement of residual stresses (RS) have been increasingly used in the last few years. The paper outlines the capability of Barkhausen noise analysis (BNA) for evaluation of real structure changes and RS on cross-section of welds due to welding of ferromagnetic plates compared with X-ray diffraction (XRD). The purpose of this study is to evaluate the RS distribution of specimens joined using by high power diode laser and metal active gas (MAG) welding that can be used for quantitative analysis of macro and micro level RS separately. The principal advantages of BNA over XRD as a tool for RS analysis and real structure characterisation are that it is mobile, faster with more facile carrying out and hence BNA is frequently used for continuous monitoring of RS in industrial processes.

Adhesive Bonding Technology at Car - Body Structure – Application of New Coating with Layer Zn/Mg

The paper deals with the application possibilities of new coatings types on the basis of Zn/Mg and their utilization at car-body production Comparison is done by evaluation bonded joints strength acc. to ISO 11339 for commonly used zinc-coated sheet at production car-body stampings (HDG Z100) with layer of new type on the basis of zinc/magnesium (ZM). Such utilization of new materials also means necessity to carry out test of the individual bonded car-body parts utility properties, mainly at peel loading, in dependence on adhesive type simultaneously with regard to the lubricant which is used in the technological process drawing of stampings and temperature under which is joint loaded. To guarantee required joints quality is one of the crucial criterions for applications new types of coatings in mass production.

X-Ray Diffraction Analysis of Zn-Mg Coating in Dependence on Deformation

The Zn-Mg coatings are considered as the next generation of steel covering to be used in automotive industry since they improve the corrosion resistance of the base material. The article is focused on the X-ray diffraction analysis of Zn-Mg coating in dependence on strain. The specimens made from a material, which has Zn-Mg coating, were gradually deformed until they became totally fractured. Subsequently, the specimens´ surface layer was analysed using X-ray diffraction. X-ray diffraction methods are used for evaluation of the qualitative changes in the real structure of the polycrystalline material. The modification of the real structure is considered as a degree of plastic deformation, change of crystallite size and their orientation depending on deformation.

Change of Tribological Properties of Zn-Mg Coating in Dependence on Deformation

Protective coatings on the basis of Zn-Mg are still more a more used in present engineering industry. However their wider using (e.g. in the automotive industry) is still limited by unsufficient and pure knowledge about their behavior in dependence on deformation. Thus this paper is focused on testing tribological properties and their change in dependence on size of deformation. That is why there was used tribological strip drawing test where samples were firstly deformed on different values (15% and 30%). Subsequently were these strips drawn between hardened and non-hardened jaws and there were evaluated different forces necessary to draw a strip and friction coefficient was calculated. Main results (mainly course of friction coefficient on pressure and deformation) were shown as graphs and tables.

2D Residual Stress and Hardness Maps in Steel Laser Weld with Filler Wire

Residual stresses (RS) and welding process represent a traditional partnership between an ever evolving, and vital, technological process and a quantity characterizing the result of this process. As the modern way of joining materials is shifting gradually from conventional welding into friction stir or laser welding, RS remain a crucial parameter which gives clues about the welds’ behavior under dynamic loads. In this contribution the joint created by laser welding with filler wire is described by 2D maps of RS and hardness.