Top PDF Finite Element Analysis of the Crack Propagation for Solid Materials

Abstract: Problem statement: The use of fracture mechanics techniques in the assessment of performance and reliability of structure is on increase and the prediction of crack propagation in structure play important part. The finite element method is widely used for the evaluation of SIF for various types of crack configurations. Source code program of two-dimensional finite element model had been developed, to demonstrate the capability and its limitations, in predicting the crack propagation trajectory and the SIF values under linear elastic fracture analysis. Approach: Two different geometries were used on this finite element model in order, to analyze the reliability of this program on the crack propagation in linear and nonlinear elastic fracture mechanics. These geometries were namely; a rectangular plate with crack emanating from square-hole and Double Edge Notched Plate (DENT). Where, both geometries are in tensile loading and under mode I conditions. In addition, the source code program of this model was written by FORTRAN language. Therefore, a Displacement Extrapolation Technique (DET) was employed particularly, to predict the crack propagations directions and to, calculate the Stress Intensity Factors (SIFs). Furthermore, the mesh for the finite elements was the unstructured type; generated using the advancing front method. And, the global h-type adaptive mesh was adopted based on the norm stress error estimator. While, the quarter- point singular elements were uniformly generated around the crack tip in the form of a rosette. Moreover, make a comparison between this current study with other relevant and published research study. Results: The application of the source code program of 2-D finite element model showed a significant result on linear elastic fracture mechanics. Based on the findings of the two different geometries from the current study, the result showed a good agreement. And, it seems like very close compare to the other published results. Conclusion: A developed a source program of finite element model showed that is capable of demonstrating the SIF evaluation and the crack path direction satisfactorily. Therefore, the numerical finite element analysis with displacement extrapolation method, had been successfully employed for linear-elastic fracture mechanics problems.

The eXtended Finite Element Method XFEM has been reliably used for an- alyzing crack growth in 3D structural elements over last years. In fact, many researchers have worked in this field, but it is scarce to find scientific con- tributions about 3D XFEM models applied to the failure of non-standard composite parts, such as tapered structures and thick laminated composites. Thus, a new computational framework is developed, which is based on a new enhanced golden section search algorithm and 3D Puck’s action plane principle in order to define the crack initiation direction. This in-formation is integrated into a XFEM and used to enrich elements, which have failed during analysis. Compared to the traditional algorithm, the new methodol- ogy has convergence one order higher than the traditional one; and it is 20 times more efficient computationally. Therefore, if more precision is needed, then higher gains are achieved combined to lower computational cost by us- ing the proposed framework. Moreover, thick laminated composites with layers mainly oriented to 90o were simulated under tension and compres- sion via the computational framework, displaying results as reported in the literature. Also, compact tension tests with 0°, 90° and 45° specimens were evaluated, and numerical results were qualitatively coherent with experi- mental data.

Finite element analysis as shown in Fig. 4 displays the distribution of the Von Misses stress and displacement in the clamp of the return air flow part. Maximum stress values were similarly found at the upper area of the neck of the part regardless of the applied load, but the values increased with increasing applied load. However, the maximum Von Misses stress in the sample reached the plateau at the applied load of approximately 4-5 N and only slightly increased with further increase in applied load (Fig. 5). These stress values were in the range of 28.8-30.8 MPa which were closed to the yield strength and even greater than the ultimate strength of the HIPS specimens as determined from tensile test. Correspondingly, the displacement of the sample linearly increased with increasing applied load without reaching a plateau limit as observed in Von Misses stress (Fig. 6). This means that when the applied load was lower than 4 N, the sample could withstand the load with only small deformation, but subjecting to high stress in some localized area. Once the load was greater than 4 N, the sample started to plastically deform and could not tolerate the applied load since the stress already reached the yield strength of the materials. At this stage, the sample changed the shape permanently or even produced damages [7]. From the analysis, the sample Proceedings of the International MultiConference of Engineers and Computer Scientists 2013 Vol II,

For full 3D elasticity formulations for vibration and linear dynamic analysis of FGM shells, one find the work of Vel and Batra (2004) based on three dimensional exact solutions for free and forced vibrations of simply supported FGM rectangular plates. In Asemi et al. (2014) the static and dy- namic analyses of FGM skew plates are obtained based on the three-dimensional theory of elastici- ty. Graded elements, the principle of minimum energy and Rayleigh-Ritz energy method are used. Using 3D elasticity model, Nguyen and Nguyen-Xuan (2015) proposed an efficiently computational tool based on an isogeometric finite element formulation for static and dynamic response analysis of FGM plates.

which is gradually increased to near the ultimate load that may be sustained by the pipe. The pipe is modelled as an elasto-plastic material using the Von Mises yield criterion which is normally used for metallic materials[2]. The specification of the load in several increments enables the spread of the plasticity to occur gradually and its effect on the stress distribution to be assessed. Key words: finite element analysis, elastic-plastic behavior, thin walled pipe equivalent stress, TWT.

But there are only a few works devoted to direct investigation of temperature evolution at fatigue crack tip. At present, it is well known that in materials under cyclic deformation, fatigue cracks are initiated in the area of plastic deformation localization and lead to an intensive heat dissipation [4]. It makes possible the early detection of crack initiation by infrared thermography [5]. The infrared thermography can be also applied during mechanical tests in order to obtain detailed information about the process of structure evolution, damage accumulation and damage-fracture transition in solids [6-8]. The investigation of the heat dissipation at the fatigue crack tip allows one to develop an effective method for determination of the linear fracture mechanics parameters in a wide range of stress intensity and, as a consequence, gives a way of monitoring of critical state of crack. The solution of this problem requests an analysis of solutions of nonlinear problems of plasticity theory and experimental investigation of plastic deformation localization at crack tip.

Structural optimization using computational tools has be- come a major research field in recent years. Methods com- monly used in structural analysis and optimization may de- mand considerable computational cost, depending on the problem complexity. Therefore, many techniques have been evaluated in order to diminish such impact. Among these various techniques, Artificial Neural Networks (ANN) may be considered as one of the main alternatives, when com- bined with classic analysis and optimization methods, to reduce the computational effort without affecting the final solution quality. Use of laminated composite structures has been continuously growing in the last decades due to the ex- cellent mechanical properties and low weight characterizing these materials. Taken into account the increasing scien- tific effort in the different topics of this area, the aim of the present work is the formulation and implementation of a computational code to optimize manufactured complex lam- inated structures with a relatively low computational cost by combining the Finite Element Method (FEM) for structural analysis, Genetic Algorithms (GA) for structural optimiza- tion and ANN to approximate the finite element solutions. The modules for linear and geometrically non-linear static fi- nite element analysis and for optimize laminated composite plates and shells, using GA, were previously implemented. Here, the finite element module is extended to analyze dy- namic responses to solve optimization problems based in fre- quencies and modal criteria, and a perceptron ANN module is added to approximate finite element analyses. Several ex- amples are presented to show the effectiveness of ANN to approximate solutions obtained using the FEM and to re- duce significatively the computational cost.

series of 3D stress analyses by finite element method have been made on SENT specimen using ABAQUS 6.5 [13] finite element software. The geometry of the specimen considered in this analysis is shown in Fig.1. Finite element computations were carried out considering only one half of the specimen due to the symmetry. The analysis domain is descritized using 20-noded isoparametric 3D solid reduced integration elements. These types of

Fatigue is still one of the main concerns when dealing with mechanical components failure. While it is fundamental to experimentally determine the fatigue material behavior using standard specimens, testing large and complex component geometries can be complicated. In these cases, the Finite Element Method can be a cost-effective solution but developing fatigue crack growth models is still a complicated task. In order to solve this problem, an algorithm for automatic crack propagation was developed. Using three different modules, the algorithm can generate a complex Finite Element Method model including a fatigue crack; solve this model considering complex loading conditions, by applying the superposition method; and calculate the fatigue crack propagation rate, using it to update the original model. In order to benchmark this solution two different problems were analyzed, a modified compact tension specimen and a cruciform specimen. By modifying the compact tension specimen hole location and simulating an initial crack, it was possible to understand how mixed mode conditions influence the fatigue crack path. Different load ratios and initial crack directions on the cruciform specimen were analyzed. Increasing the load ratio will increase the crack deflecting angle. The obtain solutions were compared with experimental results, showing good agreement. Therefore the developed algorithm can be used to predict the fatigue crack growth behavior on complex geometries and when different types of loads are applied to the component.

The numerical simulations were performed with the Three-Dimensional Elasto-Plastic Finite Element program (DD3IMP) that follows a fully implicit time integration scheme [3, 4]. The mechanical model and the numerical methods used in the finite element code DD3IMP, specially developed for the numerical simulation of metal forming processes, takes into account the large elastic-plastic strains and rotations that are associated with large deformation processes. To avoid the locking effect a selective reduced integration method is used in DD3IMP18. The optimum values of the numerical parameters of the DD3IMP implicit algorithm have been already established in previous works, concerning the numerical simulation of sheet metal forming processes [5] and plasticity induced crack closure [6].

The original of the wheel we re the round slices of a log and it was gradually re-inforced and used in this form for centuries on both carts and wagons. This solid disc changed to a design having several spokes radially arranged to support the outer part of the wheel keeping it equidistant from the wheel centre. The steel disk wheel and the light alloy wheel are the most typical installation. The method of manufacturing the light alloy wheel, wh ich has become popular in recent years, is expla ined here. The manufacturing method for the light alloy wheel is classified into two. They are cast metal or the forged manufacturing methods. The alu minu m a lloy wheel is manufactured both ways, and the casting manufacturing method is used as for the magnesium alloy wheel.

While transferring power from driving to driven sprocket, chain exerts high load on sprocket teeth.So, maximum loads acting on teeth are calculated.Stress induced due to load should be less than the yield stress of the material. If stress becomes more than yield stress of material then there is a possibility of failure. Hence static analysis was performed to ensure that the proposed design has factor of safety greater than one. Also due to cyclic load acting on the sprocket from chain, it is important to test the sprocket for fatigue loading. In fatigue analysis fatigue life of sprocket is calculated and it is ensured that the minimum fatigue life is higher for safe use of sprocket for sufficient time period. After the minimum fatigue life, crack in the component initiated, which further increases with time and leads to failure of component. Therefore it is important for any component to have sufficient fatigue life.

In this contribution modeling and simulation of surface acoustic waves (SAW) sensor using finite element method will be presented. SAW sensor is made from piezoelectric GaN layer and SiC substrate. Two different analysis types are investigated - modal and transient. Both analyses are only 2D. The goal of modal analysis, is to determine the eigenfrequency of SAW, which is used in following transient analysis. In transient analysis, wave propagation in SAW sensor is investigated. Both analyses were performed using FEM code ANSYS.

o numerically predict crack formation and growth of this model under accidental loading, it is necessary to characterize fracture properties at the microscopic level. To approach this objective a complete code of program using finite element method was written by the authors in MathCAD software. The geometrical characteristics, material properties and boundary conditions are attributed to the model. Corresponding finite element analysis was performed to determine the evolution of stress and strain states. For more comprehensible results and better facileness for comparison Von Misses stress had been calculated across the model using Eq. (1).

The term cracked tooth syndrome (CTS) refers to an incomplete fracture of a vital posterior tooth that involves the dentine and occasionally extends into the pulp (Cameron, 1964; Rosen, 1982; Lynch et al, 2002). The symptoms are very variable, making it a notoriously difficult condition to diagnose. The term was first introduced by Cameron in 1964 (Cameron, 1964), who noted a correlation between restoration size and the occurrence of CTS. It was mentioned in the earlier literature of pulpal pain resulting from incomplete tooth fractures. A more recent attempt to define the nature of this condition describes it “as a fracture plane of unknown depth and direction passing through tooth structure that may progress to communicate with the pulp and/or periodontal ligament” (Ellis, 2001). The condition

In this paper, a systematic approach for elastic finite strain crack propagation with multiple cohesive cracks and self-contact is described. Crack paths are deter- mined by the CTOD method and the advance crite- rion uses either the equivalent stress intensity factor or the tip-element stress. Crack intersections, coales- cence and cohesive laws are accounted for, as is the for- mation of multiple particles. Globally-optimized mesh repositioning is used to minimize the least-square of all elements’ inner-angle error. This is followed, in a stag- gered form, by a Godunov-based advection step for the deformation gradient. Several examples are presented showing the robustness and accuracy of the implemen- tation, as well as the ability to represent crack face thickness variation in finite strains. Classical fracture benchmarks are solved and a problem of multiple crack evolution is proposed. Excellent results were observed in the effected tests.

Abstract: Seals have wide application in automotive products. They are responsible for sealing the car in several parts such as the doors, the air intake cowl seal, and air intake lights seal. Strain and stress studies are very important in order to understand the behavior of polymeric materials, which are generally submitted to great workload variation and environmental influence. This study of EPDM rubber was carried out to define the strain, stress and yield stress. Tensile and compression tests were carried out on workpieces with 100 mm of length. The data were acquired using the Qmat software. A Finite Element Analysis using the MSC Marc Mentat™ was conducted and compared with experimental tests. The results showed an increase of effort proportional to bulb thickness. The proportional increase of compression effort for different displacements was significant. Moreover, physical parameters such as length, thickness, and friction coefficient changed the strain and stress rate.

matrix with subsequent loading. With continuous increase in load, crack propagation occurred through successive adjacent regions of fibres and matrix. The longitudinal splits observed in the propagation zone were secondary fractures and they were developed after transverse crack propagation. This is established through study of hackle directions (directions are reversed) on similar split surfaces on either side of transverse fracture. After the crack propagated to certain distance, the net load carrying capacity of the composite reduced to that of the applied load resulting in an unstable fracture. The step in final fracture was a successive fracture and it was not related to bridging. The direction of hackles on a similar longitudinal split surface on mating fracture surface shows similar orientation. Therefore, longitudinal splitting is a primary fracture and it occurred before transverse fracture. Longitudinal fracture occurs when the shear stress, τm, in the matrix reaches the ultimate shear stress, τmu. Longitudinal splitting may occur either due to longitudinal fracture of matrix or debonding process. Since the aerospace grade composite has good interfacial strength, the debonding stress τd is greater than the ultimate shear stress of the matrix, τmu, Hence, in such composites, longitudinal fracture of matrix occurs in preference to Figure 10. Random fibre fracture directions indicated by white

The paper is organized as follows: Section 2 introduces both stress-based finite element methods. In section 3, the shape functions of both CFE and CDFE methods are obtained for different bound- ary conditions in order to approximate the deflection in each element. In section 4, using La- grange’s equation, equations of motion are obtained and the natural frequencies of beams are ob- tained. Finally, in section 5, numerical examples related to the static and dynamic responses of some beams are investigated.

The intensive investigation of structural behavior of cylindrical concrete shell is carried out by using finite element method of analysis. The linear elastic analysis is performed wherein concrete is assumed to be homogeneous, isotropic having linear elastic behaviour. For a fixed cross section of shell, a parametric study involving various spans and thicknesses is undertaken. Besides the self weight, loads considered are a uniform surcharge over the shell surface and longitudinal thrust. For the finite element analysis type of elements employed are 4 noded plate elements. Results of investigation are presented in the form of useful graphical representations and same are discussed. One of the interesting findings of investigation is the graphical representation of longitudinal stresses, bending moments relates to the displacement behavior of the elements used in the analysis.