Issue 4

JTAM, Sofia, vol. 38 Issue 4 (2008)

Dynamic Behaviour of Thin Rimmed Internal Gear System

Fakher Chaari, Mohamed Riadh Letaief, Mohamed Haddar
Dynamics of Mechanical Systems Research Unit, National School of Engineers of Sfax, BP 1173 - 3038 – Sfax, Tunisia

In this paper, a dynamic model of a gear system composed of an external and an internal gear is developed. The finite elements method is used to calculate the gearmesh stiffness which is time varying and considered to be the main source of excitation source of the system. This stiffness is computed for various cases of the internal gear design. The rim thickness, the shape and the fixing mode are varied. It is shown that this design affects considerably the evolution of the gearmesh stiffness and the dynamic response of the system. Lower vibration levels are observed for certain design cases.

JTAM, Sofia, vol. 38 Issue 4 pp. 01 (2008)

Hydrogen Embrittlement in Fe,Al Intermetallics

Angel Baltov1, Zemon Mroz2
1Institute of Mechanics, Bulgarian Academy of Sciences, Akad. G. Bonchev Str., Bl. 4, 1113 Sofia, Bulgaria
2Institute of Fundamental Technological Research, Polish Academy of Sciences, 21, Swietokrzyska, Str., 00-049 Warsaw, Poland

The one-dimensional model for plastic behaviour of the Fe,Al intermetallics is proposed. Two cases are investigated: hydrogen attacks by moisture and hydrogen attacks by pressure. Experimental verification is presented. Some discussion about the possible three-dimensional generalization of the model is done.

JTAM, Sofia, vol. 38 Issue 4 pp. 02 (2008)

Nonlinear Damage Cumulative Model in Blocks Loading Conditions. Application For Gs61 Spheroïdal Graphite Cast-Iron Loaded by Torsion and Plane Bending

A. Aid1, Z. Semari2, A. Amrouche2, G. Mesmacque2, M. Benguediab3
1Laboratoire LPQ3M BP 763, Université de Mascara, Algeri
2Laboratoire de Mécanique de Lille, Université de Lille1, UMR CNRS 8107, Villeneuve d’ASCQ 59650, France
3Département de génie mécanique, Université de Dj. Liabes, Sidi Bel Abbes, 22000, Algérie

The mechanical components generally work under cyclic stresses with varying amplitudes during the lifetime. It is important in predicting fatigue life and how to deal with the problem of fatigue damage accumulation. On the basis of the data for material taken by Stress-Number of cycles at failure (S-N) curves and mechanical properties of material studied, a new nonlinear fatigue damage cumulative model is proposed, ultimate strength, loading parameters and the effect of the loading sequence are considered. This model is connected to S-N curve cycle by cycle to determine the lifetime of the material and to calculate the damage indicator. The cycles extracted are counted by one of counting cycles methods. The recurrence formula of fatigue damage was tested for four various spectra of block loading. The obtained results by this model are compared with the experimental results and those calculated by the most fatigue damage model used in fatigue (Miner’s model). Such model is in agreement with experimental results. Moreover, the error is minimized in comparison to Miner’s model.

JTAM, Sofia, vol. 38 Issue 4 pp. 03 (2008)

Residual Stress and Reduction of the Stress Concentration Factor in Rivet Holes Of 2024 –T3 Aluminium Alloy

M. Elajrami1, M. Benguediab1, G. Ronald2
1Laboratory of Material and Reactive Systems, Department of Mechanical Engineering, University of Sidi bel Abbes
2Research Center and Transfer of Technology – GeM (EMM), University of Nantes

This paper presents a numerical study whose main objective is to analyze the effects of the cold expansion on the variation of the stress field and the influence of the residual stress on the reduction of the stress concentration factor in rivet holes of 2024-T3 aluminium alloy sheet by means of the 2D finite element method This analysis is done according to the plate ligament and the hole edges by using an uniaxial tensile load, the obtained results verified the phenomena of the retardment of crack initiation and propagation experimentally observed.

JTAM, Sofia, vol. 38 Issue 4 pp. 04 (2008)

Evaluation Axisymmetric Analysis of Thermal Stress Residual Near Fiber/Epoxy Interface

A. S. Bouchikhi, A. Megueni
Department of Mechanics Engineering, University of Sidi Bel Abbes, BP 89, Cité Ben M’hidi- Sidi Bel Abbes (22000), Algeria

The finite element method is used to compute and analyze the residual stresses particularly near the fiber/epoxy interface, and these stresses need to be taken into account. An axisymmetric model has been used for stress computation and analysis, in this work two cases are considered by using an epoxy matrix with respectively glass and carbon fibers with a different volume of fiber. Numerical calculation results show that the stresses are important. The interface is affected by thermal stresses particularly in the free edge. The normal and shear stresses values have an influence on the behaviour of the composite during service.

JTAM, Sofia, vol. 38 Issue 4 pp. 05 (2008)

Development of a New Testing Method for Polymer Materials at High Strain Rate

M. Khlif1, N. Masmoudi1, C. Bradai1, V. Grolleau2, G. Rio2
1National School of Engineers of Sfax, Analysis Laboratory of Electro Mechanical Systems, BP.1173. W. 3038 Sfax, Tunisia
2University of Southern Bretagne, France, Mechanical laboratory of Engineering and Materials

The increasing use of polymeric materials in transport fields requires knowledge of their mechanical behaviour at high strain rate to optimize the structures. The particular behaviour of polymers, compared to metals, is characterized by low Young modulus, weak density and viscoplastic behaviour, which make conventional experimental test inoperative. The objective of this work is the development of a dynamic tensile test reaching from 100 to 500 s-1 (strain rate) based on the Charpy testing machine. The proposed test device is composed of an instrumented bar and a sensing block for wave strain measurement to determine the stress and strain on the tested material. The main objective consists in studying mechanical behaviour of polymer material at high strain rate.

JTAM, Sofia, vol. 38 Issue 4 pp. 06 (2008)

On the Rigid Body Motion Restriction of the Elastodynamic Infinite Element with United Shape Functions in Local Coordinates

K. Kazakov
VSU “L. Karavelov”, 175, Suhodolska Str., 1373 Sofia

In this paper the restriction of the rigid body motion of the Elastodynamic Infinite Element with United Shape Functions (EIEUSF) in local coordinate directions, given as ξ and η, is investigated. First, the concept of the construction of the so-called EIEUSF united shape functions is given in brief. The mathematical and mechanical aspects of the rigid body motion is demonstrated and discussed in some details. Such a motion is impossible form mechanical point of view and assures the EIEUSF element to be used as a special form of elastic boundary condition. The conclusions can be treated as a part of the application of the element.

JTAM, Sofia, vol. 38 Issue 4 pp. 07 (2008)