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2 Machine Dynamics Research

2 2010

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Study of the Fillers Influence on Mechanical Properties of PE by Using of AFM Measurements

Bakošova D., Šišáková J., Bezecný J., Rusnáková S.

Machine Dynamics Research

2010

Vol. 34, No. 3

13-20

The works deals with a study of fillers influence on choosing mechanic properties of high density polyethylene (HDPE) by using of atomic force microscopy (AFM), where the using method and equipment are describe. Atomic-force microscope in a complex with control and image processing software is intended for measurement and analysis of surface micro- and submicro relief, objects of the micro- and nanometer range with high resolution. Using AFM it is possible to scan curves that show dependence of composite action force of the probe and surface of the sample on distance between them - they are curves of approach /moving off. These curves are very important for measurements of vertical force attached to the surface from the side of the tip in the process of scanning. Besides the force it is also possible to evaluate viscosity of dirty surface, thickness of the covering layer and also local variations of elastic features of the surface from the curve. The curve of approach /moving off is a graphic dependence of measuring cantilever deviation on scanning device extension. Van der Waals forces are only one factor of cantilever deviation affecting. The measurement will be also influenced by thin layers of moisture that are usually present at working with AFM in the presence of air and also streaks and impurities. In presented measurements by using of spectroscopic curve were evaluated the homogeneity and ratio of Young modulus on HDPE samples. The HDPE samples were prepared in standard version and by adding of silver and gold pigment. For each sample was creation the curve by using of five different places - points. We employed the general approximation and Snedonn's formula for analysis dates and calculation of Young's modulus off complete rake curve. From spectroscopy curves and following calculations were occurred that the Young modulus of the silver sample is the 1.197 times more than the standard HDPE together the gold HDPE which is 0.822 times lesser than standard. We can allege that the silver pigmented HDPE has the reinforcing effect. From these surface topography and spectroscopic curve inclination is possibly to say that all used samples are homogeneous.

Hydrogen Embrittlement Control of Metallic Screws after the Surface Treatments by Wedge Test

Bezecný J., Šišáková J., Bakošová D.

Machine Dynamics Research

2010

Vol. 34, No. 3

21-28

By surface treatments can occur so called hydrogen embrittlement, which is proving the cracking of joining pieces. Embrittlement on the critical value is predicated by several factors and therefore is important the concretization to admit the effective curative proceeding. Most parts produced of construction steels are exposed not only the mechanical straining but also the action of aggressive environment during its service. Common used protection is the galvanic metallization. However it impending degradation dangerous of useful properties so called hydrogen embrittlement by the surface treatments. By this time doesn't exist the definitive explanation what mechanism causes the hydrogen degradation of useful properties. At the same time is not achieved the efficiency of technologically precautions the eliminated the possibly degradation of useful properties parts influenced by hydrogen. The purpose of this paper was to verify and practically realized the method of steel hydrogenization control after the heat treatment according to ISO/DIS 10587. The test apparatus comprise of the steel wedge by angle of 6° and the filling steel plate. The test consists of screw tightening on moment, its cracks controlling and observing of number of hours leading to fracture. The experimental confirmed that the method of inclined wedge is an applicable method for material hydrogenization process on the critical value. The advantage is for state if the screws of same production runs are applicable by this standard, there can be fitted into a processing. By materials tests were occurred that for hydrogen process on critical value has the most influence the bating process realized before the surface treatments. However, after this operation is impossible the dehydrogenization of parts. The meaningful influence has also the radiuses in the critical parts which can affect as the notches and stress raisers.