Structural aspects of fracture toughness of structural steels

Romaniv, O. N.; Tkach, A. N.; Zima, Yu. V.

doi:10.1007/bf00705104

Cited by 6 publications

(6 citation statements)

References 7 publications

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“…Tungsten-cobalt compositions of the VK-type have considerable advantages because, being at a slight disadvantage in relation to classical ceramics in hardness, they are significantly superior to all other tested materials in the level of Klc. A similar conclusion can be made on the basis of structural-strength diagrams of the ordinary type [20], comparing Kic with o u (Fig. 6a).…”

Section: Comparative Evaluation Of the Structural Strength Of Ceramicsupporting

confidence: 62%

Some features of formation of the structural strength of ceramic materials

Romaniv¹,

Vasyliv²

1998

Mater Sci

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On the basis of preliminary investigations of the characteristics of the crack-propagation resistance of various types of ceramic and cermet materials, we give a general evaluation of their potentialities in the context of the influence of the structural-metallurgical factor and the micromechanisms of fracture on the serviceability of the materials. We propose to evaluate the mechanical efficiency of ceramic materials by comparing their diagrams of structural strength at room and service temperatures. We found certain advantages of cermets in ensuring crack resistance under short-and long-term loading. We propose a classification of dominant and secondary micromechanisms of stress relaxation that manifest themselves in the process of crack growth in ceramics and cermets.Owing to the significant advantages of ceramic materials over traditional metallic materials with respect to the surface strength (hardness, wear resistance, erosion resistance, and resistance to corrosion fracture) at high temperatures, the former are more widely used for the production of elements of the piston-link assembly of internal-combustion engines, the nozzle-blade assembly of gas and steam turbines, the combustion chamber of rocket engines, etc.[ 1 ]. This favors an increase in serviceability, ensures particular functional properties of the components and units of certain types of equipment, and creates potentialities for the production of machines and engines whose characteristics are significantly better than the corresponding characteristics of their traditionally made analogs.However, ceramic materials are susceptible to brittle fracture due to low crack resistance under short-and longterm loading. For this reason, the problem of extension of the functional application of ceramic materials is reduced, first of all, to the development of methods for increasing the crack-growth resistance, which is important for ensuring sufficient structural strength [2].In the present work, on the basis of investigations of crack-growth resistance performed earlier, we compare potentialities of ceramic materials developed in this country in the context of the influence of the structuralmetallurgical factor and the micromechanisms of fracture on their serviceability. Materials and Methods for Evaluation of Their PropertiesTo perform comparative evaluations, we use three types of domestic ceramic materials that reflect the world trend toward the modification of structural ceramics (Table 1). They include an alumina composition (AI 2 0 3), which is a specific model of simple monophase ceramics, an alumina ceramics modified with zirconium dioxide (A12 0 3-ZrO 2 ), and a typical silicon-nitride ceramics modified with yttrium oxide (Si 3 N4-Y 2 0 3). Both modifications of ceramics were preliminarily tested for a long period of time in order to choose the optimal ratio of the components and the technological mode of sintering that allowed one to guarantee the optimal level of their structural strength [3][4][5][6][7][8]. In addition, for comparison, we con...

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Section: Comparative Evaluation Of the Structural Strength Of Ceramicsupporting

confidence: 62%

Some features of formation of the structural strength of ceramic materials

Romaniv¹,

Vasyliv²

1998

Mater Sci

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“…Fracture toughness. The calculation values of fracture toughness index, estimated on dependence K 1с = (2Еs 0.2 d cr ) 1/2 [15] (where E is the Young's modulus; s 0.2 is the calculation value of strengthening; d cr is the value of crack critical opening) according to the data of substructure parameters as well as substitution of K 1c and s y showed the following (Figures 8 and 9).…”

Section: Hybrid Technologies Of Weldingmentioning

confidence: 93%

“…In order to optimize the welding parameters, the most of process experiments in hybrid welding are dedicated to investigation of interaction between arc and laser, arc stabilizing and its spatial attachment by laser radiation, effect of shielding gas, arc voltage, welding speed and current on penetration depth [9][10][11][12][13]. currently, the main task of technologists and researchers [14][15][16][17] is investigation of the peculiarities of laser and hybrid processes, their effect on weld formation, possible advantages and elimination of disadvantages of laser and arc constituents as well as effect of process parameters on structure formation in the welding zone.…”

mentioning

confidence: 99%

Structure and service properties of hybrid laser-arc welded joints of 14KhGN2MDAFB steel

Markashova¹,

Poznyakov²,

Berdnikova³

et al. 2016

The Paton Welding J.

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The paper represents the results of experimental investigations of peculiarities in formation of structure and phase composition of welded joints from high-strength 14KhGN2MDABF steel at different speeds (v w = 72, 90 and 110 m/h) of hybrid laser-arc welding. Information received at different structural levels (from grain to dislocation) is used for analytical evaluation of effect of the structural parameters on mechanical properties and fracture toughness of the welded joints depending on modes of laser-arc welding. The investigations of effect of the structural factors on mode of crack formation under conditions of different dynamic strength tests at external bend loading as well as cyclic loading were carried out for evaluation of a complex of welded joint service characteristics. A role of the structural factors in change of level of local internal stresses, i.e. sources of nucleation and propagation of cracks in the welded joint metal, is shown. The optimum technological modes of hybrid laser-arc welding are determined. They provide for the high indices of mechanical properties and crack resistance of metal under service conditions of external loading from point of view of structure and phase composition. 17 Ref., 2 Tables, 10 Figures.

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“…The results of experimental investigations, received at different structural levels, i.e. from macro (grain) to micro (dislocation), made a basis for performance of analytical estimation of specific (differential) input of separate structural-phase factors and parameters in change of general (integral) value of mechanical characteristics, namely strength σ 0.2 , crack resistance K 1c as well as local internal stresses τ l.in being a potential source of nucleation and propagation of cracks in investigated structural microareas [4][5][6][7].…”

mentioning

confidence: 99%

Structure and properties of railway wheel surface after restoration surfacing and service loading

Markashova¹,

Poznyakov²,

Gajvoronsky³

et al. 2015

The Paton Welding J.

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Presented are the investigations of effect of composition of surfacing consumables on structure and phase composition of deposited metal of surfacing zones (surface, fusion line, HAZ) in restoration of railway wheels from grade 2 steel. Information received at different structural layers (from grain to dislocation) was used for analytical estimations of effect of parameters of forming structures on mechanical properties (σ0.2, K1c) of railway wheels, reconstructed by surfacing, before and after operation. Role of structural factors in change of level of local internal stresses τl.in, i.e. sources of crack formation in subsurface layers of deposited metal, was investigated. It is determined that surfacing consumables of bainite and bainitemartensite classes provide for high indices of mechanical properties and crack resistance of railway wheels after restoration repair and operation. 9 Ref., 1 Today problem of increase of service reliability and life of machines, mechanisms, parts etc. becomes more and more relevant. This problem is particularly critical for separate heavy loaded basic parts and mechanisms of running gear of cars and engines, main element of which is a wheel having direct contact with rail. Surface of wheel flange is subjected to the most significant wear in process of operation. Regardless different technological developments of restoration repair, problem of strength, reduction of wear level and crack resistance of railway wheels [1-3] is still relevant.In relation to restoration surfacing of surface of wheel flange, the authors carried out preliminary examinations of structural-phase changes in metal close to the roll surface of railway wheels [4]. Role of each of structural factors (phase constituents, grain, subgrain and dislocation structures, phase precipitates etc.) in change of strength and crack resistance of metal of railway wheels was investigated based on obtained results. The results of experimental investigations, received at different structural levels, i.e. from macro (grain) to micro (dislocation), made a basis for performance of analytical estimation of specific (differential) input of separate structural-phase factors and parameters in change of general (integral) value of mechanical characteristics, namely strength σ 0.2

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Structural aspects of fracture toughness of structural steels

Cited by 6 publications

References 7 publications

Some features of formation of the structural strength of ceramic materials

Some features of formation of the structural strength of ceramic materials

Structure and service properties of hybrid laser-arc welded joints of 14KhGN2MDAFB steel

Structure and properties of railway wheel surface after restoration surfacing and service loading

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