Wyniki wyszukiwania - BazTech

1

Numerical analysis of fracture behavior of functionally graded materials using 3D-XFEM

Benhamena Ali, Fatima Benaoum, Foudil Khelil, Baltach Abdelghani, Chaouch Mohamed Ikhlef

Advances in Materials Science

|

2023

|

Vol. 23, nr 3(77)

33--46

EN

This paper presents the numerical evaluation of mixed stress intensity factors (SIFs) and non-singular terms of William's series (T-stress) of functionally graded materials (FGMs) using three-dimensional extended finite element method (3D-XFEM). Four-point bending specimen with crack perpendicular to material gradation have been used in this investigation in order to study the effect of some parameters (crack position, crack size, specimen thickness) on the failure of FGMs materials. The fracture parameters (KI KII, phase angle ψ and T-stress) obtained by the present simulation are compared with available experimental and numerical results. An excellent correlation was found of the 3D-XFEM simulations with those available in the literature. From the numerical results, a fitting procedure is performed in order to propose an analytical formulation and subsequently are validated against the 3D-XFEM results.

2

Assessing surface fatigue crack growth in railway wheelset axle

Rudavskyi D. V., Kaniuk Yu. I., Duriagina Z. A., Kulyk V. V., Shefer M. S., Dolinska I. Ya.

Archives of Materials Science and Engineering

|

2020

|

Vol. 106, nr 2

59--67

EN

Purpose: The aim of the proposed research is to create a calculation model of surface fatigue crack growth at the axle of railway wheelset working under operational loads. Design/methodology/approach: The energy approach of the fracture mechanics was used to formulate the calculation model of fatigue crack propagation at the wheelset axle surface. The method of least squares was used to determine the investigated material mechanical constants that the kinetic equations of the calculation model contain. The system of differential equations of crack growth kinetics was solved numerically using the Runge-Kutta method. Findings: On the basis of the energy approach of the fracture mechanics the calculation model of fatigue macrocrack growth in three-dimensional elastic-plastic body in case of a mixed-mode I+II+III macromechanism of fracture has been built. On the basis of the created calculation model, the kinetics of the growth of fatigue cracks was investigated both in the middle part of the wheelset axle and in the axle journal. Research limitations/implications: The results obtained on laboratory specimens should be tested during a real railway wheelset axle investigation. Practical implications: The created calculation model can be used in practice to formulate method of residual lifetime estimation of railway wheelset axle. Originality/value: It was shown, that surface crack kinetics depends not only on the crack initial area but also significantly depends on the crack edge geometry and comparatively small crack-like defects at the wheelset axle surface can reach critical sizes in comparatively short run. It has been found that mechanical shear stresses caused by the weight of the loaded railway wagon in the cross section of the wheelset axle journal can significantly accelerate the growth of the transverse fatigue crack at the axle surface, reducing the period of crack subcritical growth by about 20%.

3

A strain energy density theory for mixed mode crack propagation in rubber-like materials

Boulenouar A., Benseddiq N., Merzoug M., Benamara N., Mazari M.

Journal of Theoretical and Applied Mechanics

|

2016

|

Vol. 54 nr 4

1417--1431

EN

In this paper, a numerical modeling of crack propagation for rubber-like materials is presented. This technique aims at simulating the crack growth under mixed-mode loading based on the strain energy density approach. At each crack increment length, the kinking angle is evaluated as a function of the minimum strain energy density (MSED) around the crack tip, using the Ansys Parametric Design Language (APDL). In this work, numerical examples are illustrated to demonstrate the effectiveness, robustness and accuracy of the computational algorithm to predict the crack propagation path. The results obtained show that the plan of crack propagation is perpendicular to the direction of the maximum principal stretch. Moreover, in the framework of linear elastic fracture mechanics (LEFM), the minimum values of the density are reached at the points corresponding to the crack propagation direction.

4

Computer aided teaching of the Materials Science and Engineering

Dobrzański L. A., Brom F.

Archives of Materials Science

|

2008

|

Vol. 29, nr 4

150-158

EN

The main aim of this article is to present the advantages and disadvantages of teaching Materials Science Subjects using blended learning, which was used in Fundamentals of Materials Science and Metal Materials. The purpose of the conducted research is to analyze the efficacy of e-learning as the means of introducing education within a traditional model. This article contains the description of learning within the mixed mode (mixed mode/ blended), comparison of the education results of Materials Science students using traditional method and distance education (via the Internet), and relation of students’ education effects to the results of the tests done by them on the platform. This paper will present results of the research on the influence of academic teachers and education effects in secondary school on achievements of students taught within those methods. The course presented in this article confirms that e-learning enables the introduction of the new education formula, which may embrace advantages of traditional teaching and distance education as far as Materials Science is concerned.

5

Niskonapięciowe analogowe bloki funkcjonalne realizowane w oparciu o inwertery CMOS

Kuta S., Machowski W., Jasielski J.

Pomiary Automatyka Kontrola

|

2007

|

R. 53, nr 3

70-77

PL

W artykule opisano wybrane rozwiązania układowe liniowych i nieliniowych niskonapięciowych analogowych bloków funkcjonalnych zrealizowanych w oparciu o inwertery CMOS (lub ich niewielkie modyfikacje). Rozwiązania te charakteryzują się tym, że w obwodzie zasilania występuje zawsze stos dwóch komplementarnych tranzystorów MOS, zatem są to układy pozwalające na stosowanie najniższych z możliwych napięć zasilających - takich samych jak układy cyfrowe. Podano przykłady syntezy filtrów czasu ciągłego w trybie prądowym (C-Gm) o dowolnych transmitancjach, wzmacniaczy operacyjnych ze sprzężeniem prądowym, konwejerów prądowych drugiej i trzeciej generacji oraz przedstawiono najbardziej reprezentatywny i uniwersalny układ nieliniowy - czteroćwiartkowy układ mnożący. Symulacje przeprowadzono w programie SPICE dla modelu BSIM3v3 w technologii 0,35um z AMS.

EN

The paper describes the CMOS implementation of low-voltage linear and non-linear elementary analog circuit blocks realized on inverters (eventually their very small modifications). The characteristic feature of presented circuit solutions is only two transistor stacks in-between supply rails, therefore the circuits in question are suited for the lowest possible supply and are simultaneously fully compatibile with digital part. A synthesis procedure for continuous time analog filters with arbitrary characteristics, current feedback amplifiers as well as second and third generation current conveyors is presented. The most representative and versatile nonlinear circuit block - a four-quadrant multiplier has also been constructed using inverter-like circuit elements. SPICE simulation results for 0.35 um process parameters from AMS are presented.

6

Use of e-learning in teaching fundamentals of materials science

Dobrzański L. A., Brom F., Brytan Z.

Journal of Achievements in Materials and Manufacturing Engineering

|

2007

|

Vol. 24, nr 2

215-218

EN

Purpose: The main aim of this article is to present the usage of educational platform Moodle in teaching Fundamentals of Materials Science in the Institute of Engineering Materials and Biomaterials at Silesian University of Technology in Gliwice, and to analyse the efficacy of e-learning as the means of introducing education within a traditional model. Design/methodology/approach: This article contains the description of learning within the mixed mode, which is education embracing a face to face method and distance learning method for the first-year students. The comparison of the efficacy of mixed mode learning versus traditional learning will be presented. Findings: The efficient method of assisting remotely the e-learning students acquiring skills and knowledge at a varying pace has been developed, providing them with the personalised support. Research limitations/implications: Larger population of students should be tested so as to give measurable results, which would imply what needs to be worked on and what changes to introduce in order to improve the e-learning process. Originality/value: The course presented in this article confirms that e-learning enables the introduction of the new education formula, which may embrace advantages of traditional teaching and distance education as far as Materials Science is concerned.

7

Fatigue crack growth rate in aluminium alloy including Mixed Mode I and III

Rozumek D.

Journal of Theoretical and Applied Mechanics

|

2005

|

Vol. 43 nr 4

731--743

EN

The paper contains results of experimental tests on the fatigue crack growth rate of AlCuMg1 aluminium alloy for Mixed Mode I and Mode III in conditions of different stress ratios R. For the tests, plane specimens with an external unilateral sharp notch as the stress concentrator were used. The tests were done for a constant moment amplitude under bending with torsion. The results of experimental tests were described by a nonlinear formula based on the ?J-integral range. The change of the stress ratio R from -1 to 0 caused the fatigue crack growth rate. The proposed formula for description of the fatigue crack growth rate, including the ?J- integral range, satisfactorily described the results obtained experimentally for AlCuMg1 aluminium alloy.

PL

W pracy przedstawiono wyniki badań doświadczalnych wzrostu prędkości pęknięć zmęczeniowych dla mieszanego I i III sposobu obciążenia w stopie aluminium AlCuMgl (PA6) i różnych wartości współczynnika asymetrii cyklu R. Do badań użyto próbek płaskich z koncentratorem naprężeń w postaci zewnętrznego jednostronnego karbu ostrego. Badania prowadzono dla stałej amplitudy momentu przy kombinacji zginania ze skręcaniem. Wyniki badań doświadczalnych opisano nieliniowym związkiem zawierającym zakres całki delta J. Przeprowadzone badania doświadczalne potwierdziły, że zmiana współczynnika. asymetrii cyklu R od -1 do O powodowała. wzrost prędkości pęknięć zmęczeniowych. Zaproponowany związek do opisu prędkości wzrostu pęknięć zmęczeniowych, zawierający zakres całki delta J, w sposób zadawalający opisuje wyniki uzyskane doświadczalnie dla stopu aluminium AlCuMg 1.