Showing papers by "Mohamed Haboussi published in 2013"

4210 - a hybrid weight function approach for the computation of stress intensity factor in elliptical and semi-elliptical cracks

Abstract: The use of the weight functions in fracture mechanics appears in the literature in a very increasing way in particular in the computation of the stress intensity factor (SIF). The difficulties of calculation of this significant parameter, which come from the analytical singularities present in its formulation, encourage the use of the methods using weight functions for both their simplicity and their effectiveness with respect to the other approximate methods. This work consists on the hybridization of two weight functions developed by Oore & Burns [1] and Krasowsky & al.[2] in order to model the elliptical cracks for the computation of the stress intensity factor (SIF) in mode I. The idea of hybridization consists in dividing the ellipse into two zones, then to use each one of them in the area where it is more efficient. The proportion between the two zones is determined by optimization of the relationship between the small one and the large axis of the ellipse. Compared with the exact solution, the maximum error of the results obtained is of 2.4%, whereas, for those of Krasowsky & al.[2] and Oore & Burns[1], the maximum error is 6.3% and 17.4%, respectively, and this in the case of an elliptical crack uniformly charged in an infinite body. Our approach is tested on another practical example of an internal semi-elliptical crack in tubes. In the absence of the exact solutions, the results found by our calculations are in strong correlation with those of other authors using various techniques (FEM for [3] & WFM for [2]). The idea of hybridization thus really demonstrated its effectiveness like its flexibility in the computation of SIF for a variety of problems in fracture mechanics. 1INTRODUCTION The development of the weight functions in fracture mechanics started with the work of Bueckner [4] in 1970, based on the formulation by the Green’s function, for a semi-infinite crack, in an infinite medium. The investigation in the weight functions on the one hand and the evaluation of the energy balance formula of Rice [5] on the other hand, allowed the extension of the use of the weight functions by several authors such as Oore & Burns [1] and Bortmann & Al. [6]. In 1986, Gao & Rice [7] introduced the study of the stability of the fictitiously disturbed rectilinear form from which results the values of SIF along the crack front. Other investigations related especially to the fissure shape (ellipse, half of ellipse, quarter of ellipse, rectangle. . .), to the mode of rupture (mode I, II, III or mixed), and to the large domain of application (elastoplastic, elastodynamic, thermoelastic. . .), consequently succeeded. Among those works, one can chronologically mention, Fett & al.[8] (1989), Vainshtok & al.[9] (1990), Dominguez & al.[10] (1992), Rooke & al.[11] (1994), Orynyak & al.[12] (1995), Zheng & al.[13] (1997), Kiciak & al.[14] (1998), Pommier & al.[15] (1999), Krasowsky & al.[2] (1999), Hachi & al.[16] (2003) and Christopher & al.[17] (2004). The principle of the weight function technique consists in employing one or more known solutions (known as of reference) of a particular case in order to find the solution for the general case. The reference solution generally comes from the analytical results (exact). But in some cases, the absence of such results obliges the authors, such as [12], [13], [14], [15] and [17], to use approximate solutions which could be the existing weight functions. The solution of the SIF in mode I using the weight function technique is given by the general form [12]:

Occlusal force sensor

Abstract: The invention relates to a force sensor for measuring the occlusal forces of a jaw of a patient, comprising a tubular housing (1) having an axis of revolution (R), two bearing surfaces (11, 12) which are substantially perpendicular to the axis of revolution (R) and which are to be clamped between the teeth of the patient, a test body (13) mounted in the housing (1) between the bearing surfaces (11, 12) and an application means (10) for applying the clamping forces onto the test body (13). The test body (13) comprises a disk (130), the application means (10) comprising a piston (101) engaging with a central area (1300) of the disk (130) via a first surface (1301), and a ring (104) engaging with the periphery of the disk (130) via a second surface (1302) opposite the first surface (1301).