Crack Propagation Ansys Apdl Manual

Abstract:The aim of this paper is to simulate the propagation of linear elastic crack in 3D structures using the latest innovation developed using Ansys software, which is the Separating Morphing and Adaptive Remeshing Technology (SMART), in order to enable automatic remeshing during a simulation of fracture behaviors. The ANSYS Mechanical APDL 19.2 (Ansys, Inc., Canonsburg, PA, USA), is used by employing a special mechanism in ANSYS, which is the smart crack growth method, to accurately predict the crack propagation paths and associated stress intensity factors. For accurate prediction of the mixed-mode stress intensity factors (SIFs), the interaction integral technique has been employed. This approach is used for the prediction of the mixed-mode SIFs in the three-point bending beam, which has six different configurations: three configurations with holes, and the other three without holes involving the linear elastic fracture mechanics (LEFM) assumption. The results indicated that the growth of the crack was attracted to the hole and changes its trajectory to reach the hole or floats by the hole and grows when the hole is missing. For verification, the data available in the open literature on experimental crack path trajectories and stress intensity factors were compared with computational study results, and very good agreement was found.Keywords: crack growth; stress intensity factors; mixed-mode; failure analysis; LEFM; ANSYS

The obtained SIF data set can be used to construct an easy-to-use formula through the general linear regression technique, expressing the SIF as a function of the interested crack and contact parameters and facilitating the evaluation of the crack propagation behaviour.

I have constrained the bottom surface of the test piece and applied a vertical force of 1.5E5N. The initial crack length is 6.4 mm. A manual calculation gives a value for KI of 6.152E7 . This is below the Critical Kc of 1.5e8 input in Fig. 5. The component will not fracture under this loading. The main objective is to check the value and distribution of KI.

Modelling of a crack propagating through a finite element mesh under mixed mode conditions is of prime importance in fracture mechanics. In this paper, three different crack growth criteria and the respective crack paths prediction in the cement mantle of the reconstructed acetabulum are compared. The maximum tangential stress (MTS) criterion, the minimum strain energy density (MSED) criterion and the new general fracture criterion based on the energy release rate G(θ) are investigated using advanced finite element technique. The displacement extrapolation technique (DET) is used, to obtain the SIFs at crack tip. Several examples are presented to show the robustness of the numerical techniques. The effect of the inclusions and cavities on the crack propagation in cement orthopedic are highlighted.

In the literature, there has been a little research carried out into the crack's growth path in the orthopedic cement, there have been some studies dealing with the fatigue life and/or fracture of orthopedic cement, but not following the crack's growth path66 Ramos A, Simões JA. The influence of cement mantle thickness and stem geometry on fatigue damage in two different cemented hip femoral prostheses. Journal of Biomechanics. 2009;42(15):2602-2610.,77 Graham J, Pruitt L, Ries M, Gundiah N. Fracture and fatigue properties of acrylic bone cement: The effects of mixing method, sterilization treatment, and molecular weight. The Journal of Arthroplasty. 2000;15(8):1028-1035.,88 Lennon AB, McCormack BAO, Prendergast PJ. The relationship between cement fatigue damage and implant surface finish in proximal femoral prostheses. Medical Engineering & Physics;2004;25(10):833-841.,99 Jeffers JRT, Browne M, Lennon AB, Prendergast PJ, Taylor M. Cement mantle fatigue failure in total hip replacement: Experimental and computational testing. Journal of Biomechanics. 2007;40(7):1525-1533.. Benbarek et al.1010 Benbarek S, Bachir Bouiadjra B, Bouziane MM, Achour T, Serier B. Numerical analysis of the crack growth path in the cement mantle of the reconstructed acetabulum. Materials Science and Engineering: C. 2013;33(1):543-549. used the finite element method to analyze the propagation path of the crack in orthopedic cement around a total hip replacement. Results show that the crack propagation's path can be influenced by human body posture. Benouis et al.1111 Benouis A, Boulenouar A, Benseddiq N, Serier B. Numerical analysis of crack propagation in cement PMMA: application of SED approach. Structural Engineering and Mechanics. 2015;55(1):93-109. presented a numerical modeling of crack propagation trajectory in cement of reconstructed acetabulum. The direction crack is evaluated as a function of the displacement extrapolation technique and the strain energy density theory. Kim et al.1212 Kim B, Moon B, Mann KA, Kim H, Boo KS. Simulated crack propagation in cemented total hip replacements. Materials Science and Engineering: A. 2008;483-484:306-308. determine the specific fracture mechanics response of cracks that initiate at the stem-cement interface and propagate into the cement mantle.

This paper presents a finite element analysis for the modeling of the crack growth problems in cement of reconstructed acetabulum using the displacement extrapolation technique (DET). This modeling is based on the maximum tangential stress criterion (MTS), the minimum strain energy density (MSED) criterion and the general fracture criterion based on the approximate expression of energy release rate G(θ), to present a comparison of the crack propagation paths. In this investigation, the effect of the inclusions and cavities on the crack trajectories in cement orthopedic was examined.

Where is the strain energy density function per unit volume, and r0 is a finite distance from the point of failure initiation. The angle of crack propagation θ can be determined by solving the following equations2626 Bhadauria BB, Pathak KK, Hora MS. Finite element modeling of crack initiation angle under mixed mode (I/II) fracture. Journal of Solid Mechanics. 2010;2(3):231-247.:

Fracture mechanics is based on the determination of stress intensity factors. It is therefore important to develop a numerical model capable of calculating these factors for different geometries of cracked structures under different boundary conditions. In this paper, the displacement extrapolation method2828 Alshoaibi AM, Hadi MSA, Ariffin AK. An adaptive finite element procedure for crack propagation analysis. Journal of Zhejiang University SCIENCE A. 2007;8(2):228-236.,2929 Boulenouar A, Benseddiq N, Mazari M. Strain energy density prediction of crack propagation for 2D linear elastic materials. Theoretical and Applied Fracture Mechanics. 2013;67-68:29-37. is used to calculate the stress intensity factors KI and KII as follows:

In this paper, the APDL code has been employed to create the program to simulate the mixed-mode crack propagation in the cement. The displacement extrapolation technique is used, to determine the SIFs at each increment of the crack length.

Figure 6 shows boundary conditions acting on the model. To simulate the connections with the remainder of the basin, we blocked the nodes corresponding to the junction with the iliac bone3434 Foucat D. Effets de la présence d'un grillage métallique au sein du ciment de scellement des cupules des prothèses totales de hanche. Etude mécanique et thermique. [Thèse de doctorat]. Strasbourg: Université Louis Pasteur; 2003.. The boundary conditions imposed on the geometrical model are taken from previous work1010 Benbarek S, Bachir Bouiadjra B, Bouziane MM, Achour T, Serier B. Numerical analysis of the crack growth path in the cement mantle of the reconstructed acetabulum. Materials Science and Engineering: C. 2013;33(1):543-549.,1111 Benouis A, Boulenouar A, Benseddiq N, Serier B. Numerical analysis of crack propagation in cement PMMA: application of SED approach. Structural Engineering and Mechanics. 2015;55(1):93-109.,3232 Zouambi L, Serier B, Fekirini H, Bouiadjra B. Effect of the Cavity-Cavity Interaction on the Stress Amplitude in Orthopedic Cement. Journal of Biomaterials and Nanobiotechnology. 2013,4(1):30-36.,3535 Benouis A. Effet d'interactión des cavités sur le comportement du cément orthopédique de prothèse totale de hanche. [Thèse de doctorat]. Sidi-Bel-Abbès: Université Djillali Liabes; 2015.,3636 Boulenouar A, Benouis A, Merzoug M. Application of strain energy density approach in biomechanics fracture problems. In: Actes de la 2èmeConférence Internationale de Mécanique (ICM'15); 2015 Nov 25-26; Constantine, Algeria..

The Finite element standard code ANSYS3737 ANSYS. Programmer's Manual for Mechanical APDL, Release 12.1; 2009. [cited 2016 Jun 16]. Available from: -manual-for-mechanical-apdl-e10865820.html -manu... has been employed for modeling the problem. A typical FE model is shown in Figure 7a. The special quarter point singular elements proposed by Barsoum3030 Barsoum RS. On the use of isoparametric finite element in linear fracture mechanics. International Journal for Numerical Methods in Engineering. 1976;10(1):25-37. are investigated for modeling the singular field near the crack tip in cement layer (Figure 7b). For a=50μm, the mesh discretization consists of 66583 elements and 136529 nodes. The numerical simulation is performed in plane stress conditions.

Through these results, we can conclude that the initial crack angle of 40° represents the initial direction of the crack propagation according to the opening mode (mode-I) with: KI=KImax and KII=0.

Figure 9 shows the evolution of SIFs KI and KII during crack propagation extension obtained by MTS criterion. These results are compared with those obtained by MSED and G(θ) criterion. The plotted curves show a good agreement between these three approaches. 2b1af7f3a8