Strain Energy Density Prediction of Mixed-Mode Crack Propagation in Functionally Graded Materials

The objective of this work is to present a numerical modeling of crack propagation path in functionally graded materials (FGMs) under mixed-mode loadings. The minimum strain energy density criterion (MSED) and the displacement extrapolation technique (DET) are investigated in the context of fracture and crack growth in FGMs. Using the Ansys Parametric Design Language (APDL), the direction angle is  evaluated as a function of stress intensity factors (SIFs) at each increment of propagation and the variation continues of the material properties are incorporated by specifying the material parameters at the centroid of each finite element (FE). In this paper, several applications are investigated to check for the robustness of the numerical techniques. The defaults effect (inclusions and cavities) on the crack propagation path in FGMs are examined

Two-dimensional fracture analysis of FGM under mechanical loading

This paper extends the concept to isotropic functionally graded materials and addresses fracture problems under mechanical loading. The mode-I and mixed mode stress intensity factors (SIFs) are determinate by combination between the finite element method and the displacement extrapolation technique (DET). The variation continue of the elastics properties is incorporated at the centroid of each finite element, using the Ansys Parametric Design Language (APDL). In this work, two examples are analysed to check for the robustness of the present approach, the FGM disk with a central inclined crack subjected to concentrated couple forces and the three-point bending specimen with crack parallel to material gradation. The numerical results obtained by present technique are discussed by comparison with other published results

Numerical analysis of bonded composite patch efficiency in the case of lateral U and V-notched aluminium panels

In this study, the finite element method is applied to investigate the mechanical behavior of aluminium notched structures reinforced by composite patch. In order to evaluate the efficiency of patches in the case of lateral semicircular and V-notches, it is very important to analyze the stress distribution at the notch tip and to take in consideration the influence of the geometrical and mechanical properties of the patch and the adhesive. Simple and double patch were used as reinforcement techniques. Results showed that the stress concentration factor is reduced at the notch tip by using a double patch reinforcement. This reduction becomes more noticeable when the patch thickness increases

Experimental and FE Modeling of Mixed-Mode Crack Initiation Angle in High Density Polyethylene

In this paper, an experimental and a numerical analysis were carried out using High density polyethylene (HDPE). Sheets with an initial central crack (CCT specimens) inclined with a given angle are investigated and compared to the loading direction. The kinking angle is experimentally predicted and numerically evaluated under mixed mode (I+II), as a function of the strain energy density (SED) around the crack-tip, using the Ansys Parametric Design Language (APDL).According to the experimental observations and numerical analysis, the plan of crack propagation is perpendicular to the loading direction. Moreover, as suggested by Sih in the framework of linear elastic fracture mechanics (LEFM), the minimum values Sminof the factor S are reached at the points corresponding to the crack propagation direction. These results suggest that the concept of the strain energy- density factor can be used as an indicator of the crack propagation direction

Approaching Translation Competence: the effect of vocabulary instruction on translated word learning among EFL Master Students at Saida University

This research work is an attempt to investigate the effects of vocabulary instruction on translated word learning. The experimental group was assigned to vocabulary instruction through group work enhanced by short text context, definitions and examples. However, the control group was assigned to the same treatment without examples. The main objective of the present study, therefore, was to approach the students’ translation competence with regard to two task conditions: a) isolated-word translation vocabulary. b) Phrase translation within a sentence context. The subjects of the study were First year EFL Master Students of science in didactics at Saida University. The students were divided into four homogenous groups (that consist of 5students for each) according to their performance in the pretest, two of which form the experimental group and the others form the control group. The study indicated the existence of a strong and statistically significant correlation between the two tasks. The findings demonstrated also the existence of statistically significant differences in favor of the experimental group in the post test between the means of the two test scores in the first task. However, there were no statistically significant differences between the two test scores in the second task

A STRAIN ENERGY DENSITY THEORY FOR MIXED MODE CRACK PROPAGATION IN RUBBER-LIKE MATERIALS

In this paper, a numerical modeling of crack propagation for rubber-like materials is presen-ted. 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 xamples 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 erpendicular to the direction of the maximum principal stretch. Mo-reover, 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

Crack growth path simulation in a cement mantle of THR using crack box technique

A numerical method for 2D LEFM crack propagation simulation in a cement mantle of the total hip replacement (THR) is presented. This work is based on the implementation of the displacement correlation technique (DCT) and the maximum circumferential stress (MCS) theory in a finite element code, using the Ansys Parametric Design Language (APDL). At each crack increment length, the crack direction angle is evaluated as a function of stress intensity factors (SIFs). The crack box technique is investigated for crack propagation simulation. The advantage of this technique is facilitation of the automatic remeshing of the structure during crack extension. In this paper, we analyzed the mechanical behavior of cracks initiated in the cement mantle by evaluating the SIFs. The effect of the cavities and the initial crack directions on the crack growth path has been highlighted

Computation of SIFs for cracked FGMs under mechanical and thermal loadings

The objective of this study is to present a numerical modeling of mixed-mode fracture in isotropic functionally graded materials (FGMs), under mechanical and thermal loading conditions. In this paper, a modified displacement extrapolation technique (DET) was proposed to calculate the stress intensity factor (SIFs) for isotropic FGMs. Using the Ansys Parametric Design Language APDL, the continuous variations of the material properties are incorporated by specified parameters at the centroid of each element. Three numerical examples are presented to evaluate the accuracy of SIFs calculated by the proposed method. Comparisons have been made between the SIFs predicted by the DET and the available reference solutions in the current literature. A good agreement is obtained between the results of the DET and the reference solutions

Finite element analysis of the behaviour of a crack in the orthopedic cement

In this paper, the finite element method is used to analyse the crack behaviour in the orthopedic cement of the total hip replacement by computing the stress intensity factors (SIFs) arround the crack tip. In this work, three cases are studied: crack emanating from a cavity, interaction effect of the crack emanating from a cavity with another cavity and the interaction effect of two cracks emanatingfrom two cavities. The stress intensity factors under mixed mode problems at the crack tip are computed for three zones of prosthesis: proximal, median and distal. The obtained results show that the crack initiated from a micro-cavity in the distal zone of cement can be propagated at the same time by opening and shearing of its lips. It is contrary to that initiated in the proximal zone which cannot be propagated. The mechanical behaviour of cracks in the medial zone depends of the crack initiation position