The failure criterion based on hydrogen distribution ahead of the fatigue crack tip

The hydrogen effect on the fracture toughness and fatigue crack growth behaviour in themartensitic high strength steel is investigated. The secondary ion mass spectrometry method has beenemployed to analyse the distribution of hydrogen concentration in the zone of the crack tip and at its edges.Changes in hydrogen concentration are observed in the vicinity of the propagating crack tip and at a remotesite. The hydrogen peak H C is reduced and moves away from the fatigue crack tip with the increase of themaximum stress intensity factor max K . The concept of damage evolution is used to explain fatigue crackpropagation in connection with the hydrogen redistribution ahead of the crack tip. The physical failure criterionbased on the hydrogen peak in the vicinity of the fatigue crack tip and the maximum stress intensity factor hasbeen proposed. The criterion reflects changes in the hydrogen peak which resulted from the hydrogenredistribution due to the increase of the maximum stress intensity factor as the crack length increases underfatigue loading

Fracture mechanics research at Mechanical Engineering Research Institute of the Russian Academy of Sciences

Conferencia invitada.Fracture Mechanics is currently an essential subject for understanding failure mechanisms of engineering materials and components. Accurate and rapid evaluation of singular and non-singular terms of stress, strain and displacement fields in the neighbouring of the tip of a fatigue crack is the foundation of multi-parameter Fracture Mechanics [1]. These terms are normally described by means of the Stress Intensity Factor (SIF) and the T stresses and are very useful to assess the level of safety [2] and the stability of cracks and crack-like defects in mechanical components prone to linear elastic failure, both under constant [2–7] and variable amplitude loading [8–11]. In general, evaluation of such terms cannot be performed only by finite element method [12–14]. This is due to the difficulty in accurately accounting for load level and exact geometry and orientation of defects [3,15]. Consequently, hybrid methods that incorporate experimental information [16,17] into an analytical and/or a numerical approach tend to be more trustworthy. Among these, full-field experimental techniques such as electronic speckle pattern interferometry [18–20], digital image correlation [21–27], thermo-elastic stress analysis [28–30], X-ray diffraction [31–33] and photo-elasticity [34–38] are often preferred. Estimation of Fracture Mechanics parameters requires accurate positioning of the crack tip. Moreover, local deformations as well as rigid body movements need to be taken into consideration. This research will summarise a general methodology including the above-described aspects for Fracture Mechanics analyses.Departamento de Ingeniería Civil, de Materiales y Fabricación Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Determination of fracture mechanics parameters on a base of local displacement measurements

New experimental technique for a determination of the stress intensity factor (SIF) and T-stressvalues is developed and verified. The approach assumes combining the crack compliance method and opticalinterferometric measurements of local deformation response on small crack length increment. Initialexperimental information has a form of in-plane displacement component values, which are measured byelectronic speckle-pattern interferometry at some specific points located near a crack tip. Required values offracture mechanics parameters follow from the first four coefficients of Williams’ series. A determination ofinitial experimental data at the nearest vicinity of notch tip is the main feature of the developed approach. Thatis why it is not necessary to involve complex numerical models, which include global geometrical parameters,loading and boundary conditions of the object under study, in a stage of experimental data interpretation. Anavailability of high-quality interference fringe patterns, which are free from rigid-body motions, serves as areliable indicator of real stress state around a crack tip. A verification of the technique is performed bycomparing experimental results with analogous data of FEM modelling. Experimentally determined mode I SIFfor DCB specimen with end crack is in 5 per cent agreement with the numerically simulated case. Proposedapproach is capable of estimating an influence of the notch radius on fracture mechanics parameters.Comparing SIF and T-stress obtained for U-notches of different radius both in actual and residual stress fieldconfirms this statement

Method of femtosecond libs for remote sensing of aerosol atmosphere

A feature of the propagation of high power femtosecond laser radiation in the atmosphere is self-focusing with further filamentation, which leads to the formation of plasma at some distance from the laser system. In the problem of sensing by femtosecond laser radiation, these features make it possible to implement the method of remote identification of an impurity substance contained in the form of a droplet or solid aerosol, and determination of its concentration, known in foreign literature as R-FS-LIBS (Remote Femtosecond Laser Induced Breakdown Spectroscopy) [1, 2, 3]. Work on controlling the position of the filamentation zone is carried out both abroad [4] and in Russia [5, 6]. The report presents the results of evaluating the angular distribution of emission from the breakdown region of the aerosol atmosphere by femtosecond pulses in the range from 6 to 180о and the intensity of the emission line depending on the concentration of impurity for the problem of remote sensing by the method of laser induced breakdown

Laser sounding of instantaneous and mean speed of wind using correlation method

The correlation methods for laser sounding of wind speed are based on mutual processing of lidar signals scattered from several spatially separated volumes at each altitude investigated. The time of atmospheric aerosol transport between the scattering volumes estimated by the position of maximum of the mutual correlation function is the measure of corresponding wind speed. In this case the distance between the scattering volumes (the measuring base), defining the time of aerosol movement through the measuring base also determines the lidar possibilities for measuring the instantaneous (during the time interval of several seconds) or the mean wind speed (some minutes). Based on the experimental investigations performed using two lidars, these possibilites are analyzed

Bodily Transformations as a Sign of Personal Identity Loss of Heroes of World Literature Works of Second Half of XX — early XXI Centuries

The question of the self-identity crisis of the heroes of literary works at the turn of the century is considered. Particular attention is paid to the bodily transformations of characters as a sign of the loss of personal identity. The relevance of the study is due to the need to fill the existing lacunes in modern literary criticism on the problem of bodily metamorphosis, considered in the designated context. The novelty of the research is seen in the fact that previously unexplored works of art by individual writers are analyzed. The authors offer an analysis of the most representative novels of the second half of the 20th — early 21st centuries: “The Last Dream of Reason” by D. Lipskerov, “Second Body” by M. Pavich, “Box Man” and “Alien Face” by Kobo Abe. An analysis of works through the prism of V. Podoroga’s phenomenological theory of corporeality is presented in the paper; special attention is paid to the concepts of “body without skin” and “body outside the norm”. The idea of physicality and identity of J. Baudrillard is also reflected in the work. It is proved that in the novels there are several ways of bodily modifications: moving to another body or object, changes in the functions of internal organs, fusion with an object, which is interpreted by the authors as a sign of the loss and fruitless search for the personal identity of the heroes

Calculation of the energy J -integral for bodies with notches and cracks

Abstract. The approximate solutions for calculation of the energy J -integral of a body both with a notch and with a crack under elastic-plastic loading have been obtained. The crack is considered as the limit case of a sharp notch. The method is based on stress concentration analysis near a notch/crack tip and the modified Neuber's approach. The HRR-model and the method based on an equation of equilibrium were also employed to calculate the J -integral. The influence of the strain hardening exponent on the J -integral is discussed. New aspects of the two-parameter J * c -fracture criterion for a body with a short crack are studied. A theoretical investigation of the effect of the applied critical stress (or the crack length) on the strain fields ahead of the crack tip has been carried out

Reconstruction of N2O and CH4 content by dial measurements at wavelengths of overtone CO laser

The paper presents the results of laboratory experiments on measurement of absorption and extinction of radiation of the overtone СО laser at wavelengths used for sensing of methane and N2O in the mid-IR spectral range with the differential absorption (DIAL) method, as well as the concentrations of the studied gases reconstructed from the analysis of experimentally obtained absorption coefficients

Poetics of Magical Realism in Sarah Ruhl’s сomedy “The Clean House”

The article examines the features of magical realism as a direction of literature, as well as some of the characteristic features of American drama. The history of performances of the play “The Clean House” by the American playwright Sarah Ruhl is presented in the paper, and also a brief overview of critical articles about these theatrical performances is offered. The study proves that the play "The Clean House" can be viewed in the context of magical realism, based on a number of characteristic features, such as metaphysics, conventionality, rejection of psychological explanations of the characters’ actions, the presence of two realities, distortion of space and time, existential problems. It is noted that these features are manifested at the level of compositional construction, speech organization of the play, chronotope, content. It is shown that a metaphysically closed space is materially open, and time in the play is leveled, stopped and determined by the subjective experiences of the characters. Laughter is nominated as the key concept of the play, linking the spatio-temporal organization of the text with its ontological content since through laughter the idea of the immortality of the heroes’ love, which acquires a sacred meaning is affirmed in the play. It is emphasized that the poetics of the “magical” makes it possible to realize the ontological or existential meaning of the play, to show the coexistence of the miraculous and the ordinary