Some problems of assessing the dynamic crack resistance of structural steels

2021 ◽  
Vol 18 (3) ◽  
pp. 428-435
Author(s):  
Vladimir I. SMIRNOV ◽  
◽  
Tatiana A. KNOPOVA ◽  
Sergey S. MAYER ◽  
◽  
...  
Keyword(s):  
Crack Resistance ◽  
High Speed ◽  
Dynamic Testing ◽  
Practical Importance ◽  
Dynamic Strength ◽  
Structural Steels ◽  
Dynamic Crack ◽  
Unstable Fracture ◽  
Structural Elements ◽  
Limiting State

Objective: Solving the problem of determining the conditions for the onset and development of unstable fracture, which is extremely important for the development of methods for calculating the limiting states of structural elements, improving the dynamic testing schemes of materials and classifying steels according to their ability to resist fracture. Methods: Analytical methods for assessing the limiting state of structural elements are used. Results: A brief overview of the available test methods for structural steels for dynamic strength and crack resistance is given. The experience accumulated by domestic and foreign practices in testing steels for strength and crack resistance under high-speed loading is analyzed. The disadvantages of the existing methods for assessing the indicators of dynamic strength and resistance to brittle fracture are indicated. Practical importance: It is shown that along with the traditional methods for assessing strength based on safety factors, it is necessary to develop and apply new methods for assessing the limiting state of structural elements, including by the criteria of crack resistance

Influence of the choice of wear criterion on the life of high speed machine manual taps

2020 ◽  
pp. 74-78
Author(s):  
A.E. Dreval
Keyword(s):  
Service Life ◽  
Structural Steel ◽  
Tool Life ◽  
High Speed ◽  
High Speed Steel ◽  
Parameter Dependence ◽  
Limiting State ◽  
Thread Cutting ◽  
Failure Life ◽  
High Speed Machine

The assessment of the limiting state of high-speed machine-manual taps in the processing of structural steel billets is considered. A general multi-parameter dependence is developed for calculating the criterion of allowable wear, which makes it possible to rationally use the tool life and normalize the cut amount during regrinding. Keywords thread cutting, tap, angle of the cutting part, criterion, high-speed steel, wear, failure, life, service life. [email protected]

scholarly journals Droplet impact onto a spring-supported plate: analysis and simulations

2021 ◽  
Vol 128 (1) ◽  
Author(s):  
Michael J. Negus ◽  
Matthew R. Moore ◽  
James M. Oliver ◽  
Radu Cimpeanu
Keyword(s):  
High Speed ◽  
Flexible Substrate ◽  
Practical Importance ◽  
Hybrid Approach ◽  
Hydrodynamic Pressure ◽  
Analytical Framework ◽  
Canonical System ◽  
Linear Process ◽  
Plate Motion ◽  
The Impact

AbstractThe high-speed impact of a droplet onto a flexible substrate is a highly non-linear process of practical importance, which poses formidable modelling challenges in the context of fluid–structure interaction. We present two approaches aimed at investigating the canonical system of a droplet impacting onto a rigid plate supported by a spring and a dashpot: matched asymptotic expansions and direct numerical simulation (DNS). In the former, we derive a generalisation of inviscid Wagner theory to approximate the flow behaviour during the early stages of the impact. In the latter, we perform detailed DNS designed to validate the analytical framework, as well as provide insight into later times beyond the reach of the proposed analytical model. Drawing from both methods, we observe the strong influence that the mass of the plate, resistance of the dashpot, and stiffness of the spring have on the motion of the solid, which undergo forced damped oscillations. Furthermore, we examine how the plate motion affects the dynamics of the droplet, predominantly through altering its internal hydrodynamic pressure distribution. We build on the interplay between these techniques, demonstrating that a hybrid approach leads to improved model and computational development, as well as result interpretation, across multiple length and time scales.

Crack resistance of structural steels under static and cyclic loading

1990 ◽  
Vol 22 (7) ◽  
pp. 965-970
Author(s):  
N. S. Kogut ◽  
V. N. Moskvichev ◽  
N. L. Kuklyak ◽  
L. I. Bozhenko ◽  
Yu. A. Suetin
Keyword(s):  
Cyclic Loading ◽  
Crack Resistance ◽  
Structural Steels ◽  
Static And Cyclic Loading

Speech influence in advertising texts

2020 ◽  
Vol 45 (4) ◽  
pp. 106-114
Author(s):  
Y. Kim ◽  
◽  
А. Yermekbayeva ◽  
Keyword(s):  
Practical Importance ◽  
Russian Language ◽  
Main Body ◽  
Structural Elements ◽  
School Teachers ◽  
High Quality ◽  
Great Practical Importance ◽  
Advertising Message ◽  
Potential Consumer ◽  
The Russian Language

This work is devoted to the speech impact of advertising texts, in other words, the language of advertising, the purpose of which is to attract the attention of a potential consumer by making the message as memorable and unusual as possible, lively and catchy, colorful and attractive to a potential listener / buyer. The significance of the work lies in the fact that the author, in the process of analyzing the basic structural elements of the advertising message (slogan and main body), determines the main speech techniques for the influence of advertising texts: expressive means, including metaphors, epithets metonymy, speech turns, paths, various grammatical forms and other forms of influence: nominative, one-part, verb sentences, comparative and superlative adjectives, rhymes, imperative verbs, adverbs, lexical repetition. On specific examples of advertising slogans, evidence is given that the above speech means contribute to increased demand for the advertised product or service. During the study, the author confirms the hypothesis put forward at the beginning of the study: if you skillfully use speech exposure, i.e. to choose words whose harmonious combination lays in the subconscious of a person the information transmitted to him by the manufacturer through high-quality advertising, then such an advertising text can become the key to the success of trade. The work is of great practical importance: the material presented in it can be used by students to improve the culture of speech, improve stylistically differentiated speech, as well as school teachers as methodological material in the Russian language when studying the section «Vocabulary», «Stylistics».

Dynamic Failure Mechanisms in Beryllium-Bearing Bulk Metallic Glasses

1998 ◽  
Vol 554 ◽  
Author(s):  
David M. Owen ◽  
Ares J. Rosakis ◽  
William L. Johnson
Keyword(s):  
Crack Initiation ◽  
Shear Band ◽  
Metallic Glasses ◽  
Impact Loading ◽  
High Speed ◽  
Failure Mechanisms ◽  
Shear Bands ◽  
Dynamic Crack ◽  
Dynamic Failure ◽  
Asymmetric Impact

AbstractThe understanding of dynamic failure mechanisms in bulk metallic glasses is important for the application of this class of materials to a variety of engineering problems. This is true not only for design environments in which components are subject to high loading rates, but also when components are subjected to quasi-static loading conditions where observations have been made of damage propagation occurring in an unstable, highly dynamic manner. This paper presents preliminary results of a study of the phenomena of dynamic crack initiation and growth as well as the phenomenon of dynamic localization (shear band formation) in a beryllium-bearing bulk metallic glass, Zr41.25Ti13.75Ni10Cu12.75Be22.5. Pre-notched and prefatigued plate specimens were subjected to quasi-static and dynamic three-point bend loading to investigate crack initiation and propagation. Asymmetric impact loading with a gas gun was used to induce dynamic shear band growth. The mechanical fields in the vicinity of the dynamically loaded crack or notch tip were characterized using high-speed optical diagnostic techniques. The results demonstrated a dramatic increase in the crack initiation toughness with loading rate and subsequent crack tip speeds approaching 1000 m s−1. Dynamic crack tip branching was also observed under certain conditions. Shear bands formed readily under asymmetric impact loading. The shear bands traveled at speeds of approximately 1300 m s−1 and were accompanied by intense localized heating measured using high-speed full-field infrared imaging. The maximum temperatures recorded across the shear bands were in excess of 1500 K.

scholarly journals Evaluation of crack resistance of welded joints with soft interlayers

2022 ◽  
Vol 21 (4) ◽  
pp. 308-311
Author(s):  
K. A. Molokov ◽  
V. V. Novikov
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Crack Resistance ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Transverse Load ◽  
Structural Elements ◽  
Metal Structures ◽  
Characteristic Appearance ◽  
Reliability Indicator

Introduction. Welded joints in large-sized metal structures (e.g., in the structures of ship hulls) subject to low-cycle fatigue are considered. The characteristic appearance of soft interlayers, which are significantly plastically deformed under working loads, was noted. Deformation of the metal structure with damage, especially in the form of cracks, reduces the strength and reliability of structural elements and joints. Pre-deformation negatively affects plasticity; therefore, much depends on the residual plasticity of the cracking material. At the same time, with a decrease in residual plasticity, such an important reliability indicator as the resistance of the material to crack propagation — the fracture toughness – decreases. The paper is devoted to the development of a model that includes analytical dependences for assessing the crack resistance of metal structures and their welded joints with soft interlayers according to the crack resistance limit for all crack sizes.Materials and Methods. The theory and methods of linear mechanics of materials destruction, structural-mechanical approach are used. The calculation results were analyzed and compared to the experimental data and other analytical solutions. The numerical experiment was performed for the ferrite-perlite steel grades of 10, 50, 22K, St3sp, etc., widely used in industry, as well as for alloy steels hardened to medium and high strength of 30KhGSA, 37KhN3A, etc. Results. Analytical dependences are obtained for calculating the relative crack resistance limit according to three main known mechanical characteristics of the state of the material of the soft interlayer of the welded joint.Discussion and Conclusions. The results obtained can be used to assess the crack resistance of pre-deformed structural elements and welded joints (including those with soft interlayers) operating under a transverse load. The results of experimental data and analytical calculations are shown in dimensionless form, which enables to obtain invariant results with respect to the fracture toughness limit.

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