Abstract. The strain rate is a significant external factor, and its influence on material behavior in the forming process is a function of its internal structure. This paper presents an analysis of the impact of the loading rate from 1.6 x 10-4 m s-1 to 24 m s-1 on changes in the fracture properties of steel sheet used for bodywork components in cars. Experiments were performed on samples taken from HC420LA grade strips produced by cold rolling and hot dip galvanization. Material strength properties were compared on the basis of measured values, and changes to the character of the fracture surface were observed.

The paper is focused on the experimental investigation of the montmorillonite nanofillers effect on deformation properties of polystyrene KRASTEN 171. The combination of a low amount of clay with dispersed polymeric phase may cause synergistic effects leading to very fair balance of mechanical behaviour in some cases. The paper analyses the effect of nanocomposites and type of the material on the individual measured parameters, relations between them, strength and deformation behaviour. Deformations were evaluated by non-contact videoextensometry method. The results show that doping of the base material polystyrene with nanofillers particles has an effect on the plastic deformation increments.

Strain rate is a significant external factor and its influence on material behaviour in forming process is a function of its internal structure. In this contribution the influence of loading on the deformation IF steel is investigated using rotate hammer. To study the influence of rate deformation from 8.33 x 10-3 s-1 to 4000 s -1 to changes in the fracture of steel sheet used for bodywork components in cars. Experiments were performed on samples taken from interstitial free (IF) grade strips produced by cold rolling and hot dip galvanizing. Material strength properties were compared based on measured values, and changes to fracture surface character were observed.

Dual phase (DP), interstitial free (IF) and advanced high strength low alloy steel (HSLA)sheets have been successfully used for different components of car body. DP and HSLA are used ascrash resistant and IF as cover or “skin” of car body. The development of new vehicles nowadays isbeing driven by the need to simultaneously reduce mass and increase of passenger and pedestriansafety as well as costs saving through cold forming instead of hot forming. Limited publishedinformation is available on the changes in microstructure of these steel grades at different highstrain rates [1-3].This paper deals with changes of mechanical properties, microstructure and fractography of threesteel grades, which were tested at quasi static (10-3 s-1) and high strain rate (3000 s-1). Themicrostructures were characterized in terms of ferrite grain size, aspect ratio of ferrite andelongation of constituent phases. Deformed and undeformed specimens were compared to assess thechanges in the microstructure. The fracture appearance analysis indicates that the fracture patternunder high strain rates is mainly ductile, regardless of steel grades. The microstructure changessignificantly during the deformation process under both quasi-static and dynamic tension in allinvestigated steels. The plastic deformation in ferrite dominates in this process.

Currently, the automotive industry used sheets of different qualities. The most common include IF (inter Interstitial Free) steel and alloyed steel. Use the sheet quality depends on the point of application in the production car. Testing and product testing is a standard part of the process of innovation and production itself. Testing of automotive steels under dynamic conditions is increasingly important. Changing the hardness HV 1 was performed on the fractured bars on the static and dynamic loading conditions. Tests were made on steel IF and S 460.