It was shown by tests conducted at the National Aviation University (Kiev, Ukraine) that fatigue damage of metal structures may be estimated by sensors with the surface relief pattern to indicate the accumulated fatigue damage. The nature of the deformation relief has been investigated by the light, scan and transmission microscopy, as well as by a new nano-interferometer, developed at the National Aviation University. Fractal analysis of the surface patterns based on box-counting method has proved the efficiency of fractal geometry application for additional quantitative description of such surface structures. The evolution of deformation relief parameters on the sensors surface is determined by the process of the sensor and construction fatigue damage accumulation.

Strain localisation in the heat resistant nanocoated steel at the stage of cracks nucleation, coalescence, and fragmentation of the nanocoating is investigated experimentally. Regularities in the self-organisation of plastic yielding processes and their relation to the deformation relief geometry are established.

It is shown that the deformation pattern is formed under cyclic loads and develops on the surface of the cladding layer of a structural aluminum alloy. The quantitative parameters of the deformation pattern, namely, the saturation, roughness, and plastic strains on the surface, serve as indicators of damage to the material. The experimental dependences of the analyzed parameters on the operating time (number of loading cycles) can be used for the creation of new methods aimed at the prediction of the limit state of structural elements of the aircraft structures.

620.178:539.431(045) and V. I. ZakievThe nanoindenting method is based on the automatic measurement and recording of the force acting on the indenter (10 2 − -5 N) and the depth of indentation (10 2 − -200 μm). The scratch hardness or nanoscratching method is based on the continuous recording of resistance forces to movement of the indenter impressed into the surface. Introduction.To formalize the phenomena of gradual formation of machine failures, the concept of damage accumulation is utilized, the damage of the article material in time being interpreted as deviation of its controllable properties from the initial ones [1]. Controllable parameters which manifest themselves at macroscopic level: amount of residual plastic strain, degree of wear or corrosion, main-crack length are often used as damage criteria. In these cases, objective quantitative estimations of the current degree of damage are possible, and the limiting states or remaining life can be predicted with a fairly high accuracy.However, the deviations of the properties of objects from the initial values manifest themselves not always on macroscopic scale. For instance, damage at the stage of fatigue crack initiation occurs at microstructural dimentional level and is characterized by a deviation of certain physicomechanical properties of the material (exoelectron emission, positron annihilation, internal friction, specific residual resistance, etc) from the initial values [2]. One of such diagnostic indices is microhardness, which is fairly sensitive to change in dislocation structure and loosening in thin surface layers on cyclic loading [3,4].Hardness is considered to be an integral characteristic of the strength and plasticity of materials and is determined by the depth of indentation with a preset force. This testing method is called indentation. In recent years it has been widely used to determine, apart from hardness, other physicomechanical surface properties of materials [5,6].Whereas indentation test is a method of local indentation [6], the scratch hardness test or nanoscratching method [7] allows one to estimate hardness continuously along the indenter scanning path. At the present time, the nanoscratching method is widely used in fine physical investigations of the surface properties of materials [8,9].The present-day stage of development of the methods of local and scanning indentation is characterized by the development and use of a new generation of devices with a high resolution of recording the depth of indentation, on nanoscale as well (nanoindentation depth gages). This has greatly extended the range of recordable deformation and strength characteristics of materials [10], and the methodology of depth sensing testing belongs today to promising trends in science and practice [11,12].In view of the great capabilities of the methods of local and scanning nanoindentation, the problem of using them for the diagnosis of surface layer damage, in particular in the case of fatigue of materials, is topical.The present paper considers ques...

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