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

100%

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

tom Vol. 54 nr 4

1417--1431

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.

Niskonapięciowe analogowe bloki funkcjonalne realizowane w oparciu o inwertery CMOS

63%

Kuta S. , Machowski W. , Jasielski J.

tom R. 53, nr 3

70-77

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.

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.

Use of e-learning in teaching fundamentals of materials science

63%

Dobrzański L. A. , Brom F. , Brytan Z.

tom Vol. 24, nr 2

215-218

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.

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

51%

Benhamena A. , Fatima B. , Foudil K. , Baltach A. , Chaouch M. I.

Advances in Materials Science

2023

tom Vol. 23, nr 3(77)

33--46

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.