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Evaluation of sialon ceramics - crack resistance via surface stereometry and multifractal analysis

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One of the most frequently applied parameters in quantitative fractography is the fracture area development coefficient RS. It provides, inter alia, the information on the fracture formation mechanism and the energy consumed for its formation. Sialon ceramics studies confirm this viewpoint [1]. For selected parameters RS qualitative dependencies were developed. A proportional relation betwee[...]

The effect of forming the polyethylene structure of endoprosthesis cups on morphological changes in the upper layer during friction

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To increase resistance to wear and permanent deformation of polyethylene working in a polymer/metal couple (e.g. in human joint endoprostheses), the authors applied a new method. The method consists in changing the structure and properties of polyethylene subjected to preliminary work-hardening and irradiation with an electron beam. The assessment of the morphology obtained for the material v[...]

The morphology, texture and structure orientation of polyethylene formed via work hardening and electron irradiation

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The paper presents a new method for shaping the structure and properties of polyethylene intended for endoprostheses' cups. The method consists in applying plastic strain to a semi-finished product of a cup (Chirulen) and its irradiation with an electron beam. As a result of a small, permanent deformation, performed in an area distant from the consolidation area and a high polymer orien[...]

Verification of the stereometric-fractal description of overlaps in sialon ceramics' fractures

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A quantitative description of overlaps on fractures in sialon ceramics, is presented in the paper. A conventional analysis, aiming at the determination of the percentage share of overlaps on the basis of quantitative fractography, was preceded by stereometric/fractal analyses. They enabled the selection of representative sections of samples and then, the production of transverse microsections[...]

Evaluation of the share of overlaps on 34CrMo4 steel fractures by surface stereometry and multifractal analysis methods

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A method is presented to estimate the percentage share of overlaps in 34CrMo4 steel fractures in a conventional way based on quantitative fractography and image analysis methods, as well as utilizing new stereometric/multifractal methodology. The present study was performed in order to determine whether the new method and the co-dependence developed earlier for sintered carbides can be transf[...]

Analysis of the possibilities of increasing resistance to plastic deformation of new biopolymers by means of modification through radiation

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Operational durability of the polymer-metal kinematic systems used in technology and endoprosthesoplasty depends to a considerable degree on the resistance of polyethylene to plastic deformation and wear [1÷6]. In about 90% of applications, conventional and the cheapest polymer-metal couples are still used in alloplastic procedures. In one of such cases, a ca. fivefold reduction of susceptibility to permanent deformation and tribological wear was obtained for the polyethylene Chirulen 1120. The effect was a result of a combined application of small plastic deformation (ef. ≈ 0.2, initiating the transitions) and electron beam irradiation [7÷9]. Those factors modified the morphology of the polymer. As a result, in operational conditions, the thickness of the deformed upper layer of polyethylene reduced, its degree of crystallinity and reorientation of the lamellar phase were modified, the degree of structure order increased, and in consequence, the operational durability improved. The reference literature of the last decade shows, however, that in order to increase resistance to wear and ageing, what should be aimed at is to ensure a very high molecular weight and an appropriate proportion of crystalline and amorphous phases [10÷13]. In the shaping of the properties, a more and more significant role of irradiation with an electron beam is being recognized. Doses higher than 25 kGy are conducive to decomposition of long macrochains, spatial arrangement of the structure and UHMWPE crosslinking. A growing dose, to as much as 150 kGy, causes a very significant increase of resistance to wear [14, 15]. According to the presented information from the reference literature, two grades of polyethylene have been recently introduced to production. Polymers GUR 1020 and GUR 1050 have replaced Chirulen 1120 of a molecular weight of ca. 106 g/mole. New materials weigh many times more: 5·106 and 9.2·106 g/mole, and are intended e[...]

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