STRENGTH AND HIGH-PLASTICITY MATERIALS FRACTURE MECHANISMS UNDER DISCRETE WATER-DROPLET FLOW

The field research results of the austenitic steel wear under the droplet impact erosion are presented. The stages of the erosive wear origin and development are considered. The leading part of the side cracks in the forming and growth of the erosion fracture craters, as specified in Marshall-Lawn model, is shown by the high-resolution scanning electron microscopy technique

PREDICTION OF TITANIUM ALLOYS EROSIVE WEAR UNDER LONG-TERM DROPLET-IMPACT EFFECT

The approximating model for the definition of the steam turbines blades wear rate under the continuous operation through the droplet-impact erosion is built on the ground of the comparative analysis of the stand test data of the titanium alloy samples

To problem of hydrogen embrittlement of steel at droplet impingement erosion

Introduction. The work is devoted to the problem of the hydrogen saturation of steel parts skin at their high-speed impacts with a water-drop flow. A hypothesis of the water molecules dissociation at high-speed drop impacts was suggested in a number of papers. This hypothesis was confirmed by some experimental data. The effect of this dissociation is hydrogen embrittlement of the metal surface layer. The work objective is the calculation and experimental verification of the given mechanism of the erosion destruction of the steel surface. Materials and Methods. Energy equations of various ways of the water molecules dissociation are considered for the calculation-analytical estimates. The Tate and van der Waals equations are used with allowance for the change in the phase states of water at impact. Experimental data are obtained on the basis of spectral analysis using visible monochromatic (qualitative analysis) and infrared (quantitative analysis) emissions. Research Results. An improved calculation apparatus is proposed to determine the energy level of the water molecules dissociation and free hydrogen release with account for the compressibility of water at achievable impact speeds. The results of spectral studies of bubble tracks formed on the experimental steel samples under the bench erosion tests are presented. The spectral analysis shows that the tracks are composed of air bubbles. Free hydrogen is not detected in them. Discussion and Conclusions. The calculated and experimental data obtained in this paper do not give grounds for confirming the hypothesis of hydrogen dissociation under the water-drop impacts with a steel surface in the impact velocity range of 200-600 m / s. Therefore, the mechanism of hydrogen embrittlement, apparently, should be excluded from the number of additive components of the droplet impingement erosive wear

Morphological features and mechanics of destruction of materials with different structures under impact drop cyclic loading

The process of erosion destruction of steels with austenitic, sorbitol and martensitic structure under the influence of high-speed liquid-drop collisions is studied. The characteristics of the morphological features and mechanisms of the process of surface degradation of steels with different structures are given. Their classification criterion is proposed on the basis of the diagrams of limiting states. Based on the theory of Paris-Erdogan, the computational and analytical model of the fatigue fracture of martensitic steel has been developed

Morphological features and mechanics of destruction of materials with different structures under impact drop cyclic loading

The process of erosion destruction of steels with austenitic, sorbitol and martensitic structure under the influence of high-speed liquid-drop collisions is studied. The characteristics of the morphological features and mechanisms of the process of surface degradation of steels with different structures are given. Their classification criterion is proposed on the basis of the diagrams of limiting states. Based on the theory of Paris-Erdogan, the computational and analytical model of the fatigue fracture of martensitic steel has been developed

Research in domain of droplet impingement erosion of the power equipment: lookback study and context analysis

The main work objective is the creation of the scientific background for correct determination of a set of requirements to the fabrication material with a high-wearing feature under the droplet impingement erosion. A review of a backward and present state of the art of the national and foreign investigations in the field of the droplet impingement erosion of metal materials is carried out. The main outcome is as follows: insufficient fundamentality of research in this area; limitation of the used theoretical models; one-sided approach of many authors to the phenomenon that combines a whole set of factors of different physical nature. On this background, the author's concept of the erosive wear process of metal under the influence of two-phase mist flow is presented. Particular attention is paid to a new scientific hypothesis of the active hydrogen effect on the fracture of metal under the hypervelocity dropwise collisions

Development of the Paris-Erdogan model for the quantitative evaluation of the wear resistance of materials under dynamic contact with a discrete liquid-drop flow

The known fatigue model of Paris-Erdogan was first used for conditions of multi-cycle water-drop impacts with a metallic surface. The model is supplemented by the structure-dependent characteristics of the material. Experimental data providing correctness of model application is presented. The applied problem of quantitative evaluation of the material durability in the conditions of the droplet impact and comparison of materials of different structural classes was solved in the work without costly bench tests

Development of the Paris-Erdogan model for the quantitative evaluation of the wear resistance of materials under dynamic contact with a discrete liquid-drop flow

The known fatigue model of Paris-Erdogan was first used for conditions of multi-cycle water-drop impacts with a metallic surface. The model is supplemented by the structure-dependent characteristics of the material. Experimental data providing correctness of model application is presented. The applied problem of quantitative evaluation of the material durability in the conditions of the droplet impact and comparison of materials of different structural classes was solved in the work without costly bench tests