A B S T R A C T The most valuable quantitative information contained in fatigue fracture surfaces is related to striations. An alternative source of information, in particular if striation identification is impossible, can be the general characteristics of fracture micromorphology evaluated by digital image analysis. For study of micrographs as image textures, new methods called textural fractography have been developed. In this paper, some of these methods and examples of their application are described. A generalization for the case of a variable cycle loading is proposed, based on a new concept of counting loading cycles. The presented work foreshadows the potential contribution of textural fractography for fractographic reconstitution of fatigue crack history.Keywords fatigue crack growth; image texture; quantitative fractography; variable cycle loading. N O M E N C L A T U R ES a = crack length a = crack increment in one cycle a cc = crack increment under constant cycle loading a real = crack increment under general loading B = harmonic wave C = vector of regression constants F = loading force F = matrix of image features f ij = j-th feature of i-th image h = effectivity of a loading cycle L = vector of logs of crack rates assigned to images N = number of loading cycles N ref = reference number of loading cycles p = period (wavelength) of a harmonic wave v = macroscopic fatigue crack growth rate v ref = RCGR, reference fatigue crack growth rate X = image of fracture surface x ij = local image brightness θ = orientation of a harmonic wave I N T R O D U C T I O NThe knowledge of the real history of a fatigue process is very valuable for design, development and reliable operation of structures exposed to time-variable loading service conditions. Information of this type can be obtained with

The effect was studied of the solvent of chloroplatinic acid used for impregnation of activated carbon on the distribution and dispersion of platinum and on the catalyst activity. Using different solvents, catalysts were prepared exhibiting either surface platinum distribution (water) or its uniform distribution (ketones). Catalysts with uniform platinum distribution displayed a better stability of the platinum dispersity against sintering. The catalyst activities in liquid phase hydrogenation of 1-octene and of nitrobenzene were related to the platinum dispersity; the results suggest that the hydrogenations of the two substrates are governed by different mechanisms.

A B S T R A C T Quantitative fractography of components which have failed under cyclic loading can offer very valuable information usually unattainable by any other means -in particular, a detailed description of fatigue crack growth (FCG) in space and in time. The reliable characterization of crack propagation provides data important in engineering applications.The main source of information on the relationship between fractographic findings and macroscopic crack growth rate (CGR) is striation spacing. This quantitative microfractographic characteristic was the basis for the methods described in the paper. An application of the fractographic reconstitution of FCG is illustrated by an example of an aircraft wing spar fatigued during a full-scale test.Keywords fatigue crack growth; quantitative fractography; striation spacing. N O M E N C L A T U R Ea = crack length D = relation between macroscopic crack growth rate and striation spacing N = number of loading cycles p s = area percentage of striation patches on fracture surface v = macroscopic crack growth rate s = striation spacing K = stress intensity factor range K eff = effective value of stress intensity factor range ϑ = angle between local & macroscopic crack growth direction I N T R O D U C T I O NFractography is a potent and useful tool for studying failure processes in a broad spectrum of applicationsfrom fundamental research on relations between material microstructure and failure micromechanisms to practical failure analysis of service events. General capability of the fractography is based on a simple axiomatic presumption: the information on a failure process history is encoded in the fracture surface, and possibly in its vicinity. The task of fractography is to decode this information, and to apply it in the fields of fracture & damage mechanics, materials science and other linked disciplines.Our interest is to discuss the information encoded in a new surface created by a fatigue crack in a cyclically loaded body. Fatigue cracks can propagate by many fracture micromechanisms. The character of the failure proCorrespondence: I. Nedbal.

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