scholarly journals MATHEMATICAL MODELING OF THE INFLUENCE PARAMETERS DURING FORMATION AND PROPAGATION OF THE LÜDERS BANDS

2020 ◽  
pp. 595
Author(s):  
Tin Brlić ◽  
Stoja Rešković ◽  
Zoran Jurković ◽  
Gordan Janeš
Keyword(s):  
Mathematical Models ◽  
Plastic Flow ◽  
Local Stress ◽  
Image Correlation ◽  
Maximum Temperature ◽  
Microalloyed Steels ◽  
Band Formation ◽  
The Difference ◽  
Lüders Band ◽  
Lüders Bands

In this study, an analysis of the influence parameters measured by the static tensile test, thermography and digital image correlation was performed during formation and propagation of the Lüders bands. A new approach to the prediction of stresses, maximum temperature changes and strains during the Lüders band formation and propagation is proposed in this paper. Application of the obtained mathematical models of influence parameters gives a clear insight into the behavior of niobium microalloyed steel at the beginning of the plastic flow, which can improve product quality and reduce costs during the forming of microalloyed steels with the appearance of the Lüders bands. The obtained models of influential parameters during formation and propagation of the Lüders bands have been developed by the regression analysis method. The proposed mathematical models showed low deviations of calculated results ranging from 1.34% to 12.37%.The local stress amounts, important in the forming of microalloyed steels since indicating surface roughness and plastic flow possibilities during the Lüders band propagation, are obtained by the mathematical model. It was found that stress amounts increase during the Lüders band propagation in the area behind the Lüders band front. The difference in stress amount between the start of the Lüders band propagation and advanced Lüders band propagation is 25.53 MPa.

scholarly journals Автоволновое описание пластичности материалов с нестабильной фазовой структурой на макромасштабном уровне

2021 ◽  
Vol 91 (2) ◽  
pp. 267
Author(s):  
В.И. Данилов ◽  
Л.Б. Зуев ◽  
В.В. Горбатенко ◽  
Л.В. Данилова ◽  
Д.В. Орлова
Keyword(s):  
Plastic Deformation ◽  
Digital Image Correlation ◽  
Phase Transformations ◽  
Plastic Flow ◽  
Experimental Analysis ◽  
Titanium Nickelide ◽  
Image Correlation ◽  
Mechanisms Of Formation ◽  
Deformation Processes ◽  
Lüders Bands

The regularities of plastic flow in materials with deformation-induced phase transformations on the example of titanium nickelide and TRIP steel are studied. For experimental analysis of plastic deformation processes, the method of digital image correlation has been used, which allows us to quantitatively describe the behavior of plasticity fronts associated with the course of phase transformations in the materials under study. The mechanisms of formation of Lüders bands and Portevin-Le Chatelier bands at different stages of plastic flow are considered.

Nucleation and Boundary Layer Growth of Shear Bands in Machining

2019 ◽  
Author(s):  
Shwetabh Yadav ◽  
Dinakar Sagapuram
Keyword(s):  
Boundary Layer ◽  
Shear Band ◽  
Plastic Flow ◽  
High Speed ◽  
Cutting Speed ◽  
Critical Shear Stress ◽  
Layer Growth ◽  
Image Correlation ◽  
Material System ◽  
Band Formation

Abstract An experimental study of shear band formation in cutting of metals is made using a low melting point Bi-based alloy as a model material system. High-speed imaging is used to capture the transition in the plastic flow, from laminar to shear banded flow, as a function of cutting speed. The dynamics of shear band nucleation is captured in situ and temporal evolution of localized plastic flow during shear band growth is quantitatively analyzed using an image correlation method, particle image velocimetry (PIV). The observations show that shear band nucleation is governed by a critical shear stress criterion, and accompanied by a large drop in the flow viscosity by several orders of magnitude, analogous to the phenomenon of yielding in yield-stress (Bingham) fluids. Likewise, the displacement field around a freshly nucleated shear band evolves in a manner resembling the boundary layer formation in planar flow of a Bingham fluid with a very small viscosity. Surprisingly, temperature has little influence on shear band nucleation or growth.

scholarly journals In-Situ Observation of Lüders Band Formation in Hot-Rolled Steel via Digital Image Correlation

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 530 ◽  
Author(s):  
Hai Qiu ◽  
Tadanobu Inoue ◽  
Rintaro Ueji
Keyword(s):  
Stress Concentration ◽  
Yield Stress ◽  
Image Correlation ◽  
In Situ Observation ◽  
Rolled Steel ◽  
Band Formation ◽  
Hot Rolled ◽  
Hot Rolled Steel ◽  
Lüders Band

Although the Lüders yield phenomenon has been investigated for more than 150 years, some understanding of Lüders band formation lack substantial support from experimental evidence. In-situ observation of Lüders band formation in hot-rolled steel experimentally clarified the following facts: (i) When stress reaches the true upper yield stress, the Lüders band begins to nucleate. True upper yield stress is greater than nominal upper yield stress. (ii) Gross stress concentration promotes the Lüders band formation, and the size of the gross stress concentration region determines the initial width of the Lüders band. (iii) The Lüders band nucleates far ahead of the gross yield point.

scholarly journals Identification of Lüders bands using digital image correlation

2019 ◽  
Vol 9 (1) ◽  
pp. 8-11
Author(s):  
Tin Brlić ◽  
Dimitri Debruyne ◽  
Pascal Lava ◽  
Stoja Rešković ◽  
Ivan Jandrlić
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Microalloyed Steel ◽  
Image Correlation ◽  
Qualitative And Quantitative Analysis ◽  
Static Tensile ◽  
Niobium Microalloyed Steel ◽  
Lüders Band ◽  
Lüders Bands

This paper presents the characterization of Lüders bands by digital image correlation on niobium microalloyed steel during a static tensile testing. Digital image correlation with the qualitative and quantitative analysis of the Lüders bands on the microalloyed steel was proved as a very precise and suitable method for determining the strain amount in the deformation zone. In this research was determined that the strain amount is the highest in the area behind the Lüders band front and the lowest in the area in front of the Lüders band.

Numerical Study of Mechanical Behaviour of Heterogeneous Materials

2012 ◽  
Vol 730-732 ◽  
pp. 549-554
Author(s):  
Rui M. Branco ◽  
Pedro Prates ◽  
Marta C. Oliveira ◽  
Nataliya A. Sakharova ◽  
J. Valdemar Fernandes
Keyword(s):  
Mechanical Behaviour ◽  
Numerical Study ◽  
Local Stress ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Correlation Technique ◽  
Element Analysis ◽  
Plastic Properties ◽  
The Difference

The mechanical behaviour of heterogeneous specimens under uniaxial tensile test is studied using finite element analysis. The difference between mechanical properties of adjacent regions in the heterogeneous specimen creates constraints which alter the strain path relatively to pure tension. A methodology for determining the local stress-strain curves is proposed and successfully tested numerically on the heterogeneous specimen composed by two materials with dissimilar plastic properties. This methodology has recourse to the same type of variables which are usually obtained experimentally with the digital image correlation technique.

Mathematical models of Gauss – Kruger projection for calculation of meridians conversion on the plane and scale of the image

2018 ◽  
Vol 934 (4) ◽  
pp. 2-7
Author(s):  
P.A. Medvedev ◽  
M.V. Novgorodskaya
Keyword(s):  
Mathematical Models ◽  
Analytical Methods ◽  
Theoretical Studies ◽  
Spherical Trigonometry ◽  
Cylindrical Projection ◽  
Rectangular Coordinates ◽  
In Series ◽  
Observational Errors ◽  
The Difference

This work contains continued research carried out on improving mathematical models of the Gauss-Krueger projection in accordance with the parameters of any ellipsoid with the removal of points from the axial meridian to l ≤ 6° . In terms of formulae earlier derived by the authors with improved convergence for the calculation of planar rectangular coordinates by geodesic coordinates, the algorithms for determining the convergence of meridians on the plane and the scale of the image are obtained. The improvement of the formulae represented in the form of series in powers of the difference in longitudes was accomplished by separating spherical terms in series and then replacing their approximate sums by exact expressions using the formulae of spherical trigonometry. As in previous works published in this journal [7, 8], determining the sums of the spherical terms was carried out according to the laws of the transverse-cylindrical projection of the sphere on the plane. Theoretical studies are given and formulae are proposed for estimating the observational errors in the results of the derived algorithms. The maximum of observational errors of convergence of meridians and scale, proceeding from the specified accuracy of the determined quantities was established through analytical methods.

scholarly journals Development of Simulation Program for Temperature Field of Mass Concrete Structures

2018 ◽  
Vol 38 ◽  
pp. 03020 ◽  
Author(s):  
Zheng Si ◽  
Qian Zhang ◽  
Ling Zhi Huang ◽  
Dan Yang
Keyword(s):  
Temperature Field ◽  
Concrete Structure ◽  
Relative Difference ◽  
Maximum Temperature ◽  
Mass Concrete ◽  
Field Calculation ◽  
Concrete Dam ◽  
Roller Compacted Concrete ◽  
Roller Compacted Concrete Dam ◽  
The Difference

Most existing temperature field calculation programs have relative defects. In the present paper, based on merits of ANSYS platform, a temperature field calculation program of mass concrete structure is developed and demonstrated. According to actual pouring progress and thermodynamic parameters, a roller-compacted concrete dam is simulated. The difference of maximum temperature between calculated and measured values of measuring points is less than 1.8°C. Furthermore, the relative difference is -5%–5%. This result shows that the calculation program developed based on ANSYS platform can simulate and calculate the temperature field of mass concrete structure.

Analysis of Stresses in CFRP Composite Plates Drilled with Conventional and Abrasive Water Jet Machining

2013 ◽  
Vol 763 ◽  
pp. 127-143 ◽  
Author(s):  
M. Saleem ◽  
Habiba Bougherara ◽  
L. Toubal ◽  
F. Cénac ◽  
Redouane Zitoune
Keyword(s):  
Fatigue Testing ◽  
Composite Plates ◽  
Water Jet ◽  
Image Correlation ◽  
Initial Surface ◽  
Abrasive Water Jet ◽  
Machining Processes ◽  
Static Tests ◽  
The Difference ◽  
Conventional Machining

The aim of this paper is to analyze the influence of two machining processes on the mechanical behaviour of composite plates under cyclic loading. For this purpose, an experimental study using several CFRP plates drilled with conventional machining and non-conventional machining (abrasive water jet) was carried out. Digital image correlation and static tests using an Instron 4206 tester were performed. In addition, infrared thermography (IR) and fatigue tests were also performed to assess temperature and damage evolutions and also the stiffness degradation. Fatigue results have shown that the damage accumulation in specimens drilled with conventional machining was higher than the abrasive water jet ones. Furthermore, the endurance limit for plates drilled conventionally was approximately 10% higher than those drilled with abrasive water jet. This difference was related to the initial surface integrity after machining induced by the difference in the mechanism of material's removal between the two processes. The difference in surface texture was responsible for the initiation of stress concentration sites as evident from IR camera’s stress analysis. This was confirmed by SEM tests conducted after a destructive sectioning of the specimens before fatigue testing.

Studies of Elastic-Plastic Instabilities

1999 ◽  
Vol 66 (1) ◽  
pp. 3-9 ◽  
Author(s):  
V. Tvergaard
Keyword(s):  
Shear Band ◽  
Plastic Flow ◽  
Continuum Mechanics ◽  
Shear Band Formation ◽  
Band Formation ◽  
Elastic Plastic ◽  
Localized Necking ◽  
Focus On Results ◽  
Metal Sheets ◽  
Bifurcation Behavior

Analyses of plastic instabilities are reviewed, with focus on results in structural mechanics as well as continuum mechanics. First the basic theories for bifurcation and post-bifurcation behavior are briefly presented. Then, localization of plastic flow is discussed, including shear band formation in solids, localized necking in biaxially stretched metal sheets, and the analogous phenomenon of buckling localization in structures. Also some recent results for cavitation instabilities in elastic-plastic solids are reviewed.

The mechanism of work-hardening and slip-band formation

1957 ◽  
Vol 242 (1229) ◽  
pp. 147-159 ◽  
Keyword(s):  
Single Crystals ◽  
Slip Band ◽  
Work Hardening ◽  
Stage I ◽  
Polycrystalline Materials ◽  
Temperature Dependent ◽  
Band Formation ◽  
Slip Bands ◽  
Three Stages ◽  
The Difference

A summary is given of some present ideas on the mechanism of work-hardening of single crystals and polycrystalline materials. In particular, the difference is stressed between the three stages of hardening: stage I, or easy glide; stage II, the region of rapid hardening accompanied by short slip lines; and stage III, the region of slow or parabolic hardening which is temperature-dependent and in which long slip bands are formed.

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