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The paper deals with experimental simulation measuring and the analysis of defect distribution in passenger car tire under dynamic loading. The main reason for detection of defect extension is to recognize an influence of closed air, small bubbles, separations in tire and it is mainly connected with its quality during its service in a vehicle in terms of road safety. This analysis should help constructors to solve critical conditions in tire casing, whether material selection and individual components proportions are suitable and fit or even the whole construction of tire casing is suitable. The reason for detection of internal defects in tire casing is to avoid the wear of those tires which already contain some internal defects and already recognised separations, which could propagate during the movement of vehicles. This is closely connected with the occurrence of tire destruction and the main purpose is to prevent its critical status and later vehicle crash and human life menace.

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The main aim of this article is study the cause of gear wheel failure. This component has worked in the motorcycle gearbox. During the operation of the transmission, the gear wheel tooth was broken, which made it impossible to continue running this device. The investigation of the damaged area was focused on determining the chemical composition of the inclusions which are present of gear wheel material as well as detecting changes of material contrast in microlocalities close to the defective areas. The method of energy-dispersive spectroscopy and scnanning electron microscopy were chosen for this type of analysis. Furthermore, the micropurity and microstructure of the material were evaluated by methods of optical microscopy and scanning electron microscopy. Using a thermo-emission scanning electron microscope, the microcrack area was evaluated in the mode of secondary electrons and also in the mode of backscattered electrons. In this way, the fracture surface was examined in terms of its micromorphology as well as material contrast.