Crack growth analysis in friction stir welded joint zones using extended finite element method

U ovom radu je prikazana analiza rasta prsine u zonama zavarenog spoja izvedenog postupkom frikcionog zavarivanja mešanjem (FSW). Ploče od legure aluminijuma 2024-T351 su sučeono zavarene primenom postupka FSW. Ploče su modelirane primenom softvera ABAQUS. Osobine materijala u zonama zavarenog spoja su prihvaćene iz radova drugih autora. Ploča je podvrgnuta zamornom opterećenju zatezanjem sa faktorom nesimetričnosti ciklusa R = 0. Rast prsline je praćen (za nestacionarnu prslinu) i faktori intenziteta napona su analizirani u okolini vrha prsline za svaki front prsline. Proširena metoda konačnih elemenata (XFEM) u ovoj analizi je omogućila automatsku generaciju mreže oko vrha prsline kod svakog koraka tokom njenog rasta. Cilj ovog rada je procena integriteta konstrukcije sa inicijalnom prslinom, dobijene frikcionim zavarivanjem mešanjem.Presented in this paper is the analysis of crack growth in zones of a welded joint, obtained by Friction Stir Welding - FSW. Plates of aluminium alloy 2024-T351 are frontally welded using the FSW procedure. Plate models are made using ABAQUS software. Material properties in the weld zones are adopted from papers by other authors. The plate is subjected to tensile fatigue loading with cycle asymmetry factor of R = 0. The crack growth is observed (for a non-stationary crack) and stress intensity factors are analysed around the crack tip for every crack front. The eXtended Finite Element Method (XFEM) in this analysis has enabled automatic mesh generation around the crack tip for every step of its growth. The aim of this paper is the integrity assessment of a structure that is produced by friction stir welding with an initial crack

Practical aspects of finite element method applications in dentistry

The use of numerical methods, such as finite element method (FEM), has been widely adopted in solving structural problems with complex geometry under external loads when analytical solutions are unachievable. Basic idea behind FEM is to divide the complex body geometry into smaller and simpler domains, called finite elements, and then to formulate solution for each element instead of seeking a solution for the entire domain. After finding the solutions for all elements they can be combined to obtain a solution for the whole domain. This numerical method is mostly used in engineering, but it is also useful for studying the biomechanical properties of materials used in medicine and the influence of mechanical forces on the biological systems. Since its introduction in dentistry four decades ago, FEM became powerful tool for the predictions of stress and strain distribution on teeth, dentures, implants and surrounding bone. FEM can indicate aspects of biomaterials and human tissues that can hardly be measured in vivo and can predict the stress distribution in the contact areas which are not accessible, such as areas between the implant and cortical bone, denture and gingiva, or around the apex of the implant in trabecular bone. Aim of this paper is to present - using results of several successful FEM studies - the usefulness of this method in solving dentistry problems, as well as discussing practical aspects of FEM applications in dentistry. Some of the method limitations, such as impossibility of complete replication of clinical conditions and need for simplified assumptions regarding loads and materials modeling, are also presented. However, the emphasis is on FE modelling of teeth, bone, dentures and implants and their modifications according to the requirements. All presented studies have been carried out in commercial software for FE analysis ANSYS Workbench

Practical aspects of finite element method applications in dentistry

The use of numerical methods, such as finite element method (FEM), has been widely adopted in solving structural problems with complex geometry under external loads when analytical solutions are unachievable. Basic idea behind FEM is to divide the complex body geometry into smaller and simpler domains, called finite elements, and then to formulate solution for each element instead of seeking a solution for the entire domain. After finding the solutions for all elements they can be combined to obtain a solution for the whole domain. This numerical method is mostly used in engineering, but it is also useful for studying the biomechanical properties of materials used in medicine and the influence of mechanical forces on the biological systems. Since its introduction in dentistry four decades ago, FEM became powerful tool for the predictions of stress and strain distribution on teeth, dentures, implants and surrounding bone. FEM can indicate aspects of biomaterials and human tissues that can hardly be measured in vivo and can predict the stress distribution in the contact areas which are not accessible, such as areas between the implant and cortical bone, denture and gingiva, or around the apex of the implant in trabecular bone. Aim of this paper is to present - using results of several successful FEM studies - the usefulness of this method in solving dentistry problems, as well as discussing practical aspects of FEM applications in dentistry. Some of the method limitations, such as impossibility of complete replication of clinical conditions and need for simplified assumptions regarding loads and materials modeling, are also presented. However, the emphasis is on FE modelling of teeth, bone, dentures and implants and their modifications according to the requirements. All presented studies have been carried out in commercial software for FE analysis ANSYS Workbench

Fem analysis of pressure vessel with an investigation of crack growth on cylindrical surface

To ensure reliability of pressure vessels during service it is necessary to (1) know properties of materials used in their design and (2) evaluate vessels' behaviour under different working conditions with satisfying accuracy. Due to various technical and/or technological requirements, nozzles are usually welded on vessel's shell producing geometrical discontinuities that reduce the safety factor. To evaluate their influence, vessels with two different nozzles were experimentally studied and critical areas for crack initiation have been identified by 3D Digital Image Correlation (DIC) method. After that, the numerical analysis of equivalent 3D finite element model was performed and obtained results were compared with experimental values. In the most critical area, next to the one of the nozzles, crack was initiated and then growth of the damage was simulated using extended finite element method (XFEM). In this paper evaluation of stress intensity factors (SIFs) along crack path is presented, as well as the most probable direction of the crack propagation on the shell. Based on SIFs values, critical length of the crack and number of pressure cycles to the final failure were estimated

Assessment of the integrity and life of welded panel using local stresses

Relevantne lokalne karakteristike zamornog opterećenja su najveći amplitudni napon i odgovrajauća srednja vrednost napona, koje treba odrediti za celu komponentu. Relevantna svojtva materijala se onda upoređuju sa dobijenim naponima, na osnovu čega je procenjen integritet i vek panela od Al legure sa zavarenim ukrućenjem. Za određivanje najvećih napona korišćena je metoda konačnih elemenata.Relevant local characteristics of fatigue loading are the largest stress amplitudes in the related mean stress values. They should be determined for the whole components. The relevant material properties are then compared with the stresses to assess integrity and life of a panel, made of Al allow, with welded stringers. To determine the maximum stresses the Finite Element Method was used

Investigation of fatigue life in superalloys structural components

The researches in the field of fatigue failure are mainly aimed at identifying the factors which determine the fatigue behavior of the structural components and their inter relations. It is known that the fatigue resistance of structures is influenced mostly by load sequences, combinations of load types, as well as by materials and their fatigue properties. Therefore, the fatigue life cannot be determined without a thorough analysis of these parameters. Materials known as superalloys exhibit excellent mechanical strength and considerable creep resistance, especially at high temperatures. However, a critical property of these alloys is their resistance to fatigue-crack propagation, particularly at service temperatures. Besides, their fatigue features are not as easily accessible as of other materials (aluminum or steel, for instance). Consequently, determining the fatigue life in superalloy structures is not an easy task to accomplish. Taking into consideration the superalloy properties set in the NASGRO database, this thesis has explored the fatigue life of the real structural components, considering – at the same time – the stresses of both constant and variable amplitudes. The structural components have been designed in the CATIA v5, whereas the propagations of the 2D and 3D fatigue cracks through the structure have been simulated afterwards by the application of the FEM in the FRANC2D/L, and the application of the extended finite element method (XFEM) in the Abaqus software. Special attention has been devoted to the fatigue analysis of the spar of a light aircraft. Numerical methods have been used to identify the weak points on the spar, along with the fatigue life of a spar crack and its direction of propagation. The results gained have corresponded well with the experimental values obtained on the spar of the alloy 2024-T3. Taking into account the good correlation between numerical and experimental values, the same finite element models have been used to estimate the crack life on the spars made of super alloys. The investigations have shown that the majority of the super alloys possess fatigue properties similar to aluminum, and in a few of them the life of fatigue crack has proved to be much longer than in the 2024-T3 alloy

Failure analysis of bicycle frame composite structure based on stacking variant of laminate layers

No matter what kind of bike the parts belong to (according to the requirements they need to meet), these parts are almost identical. The most complex bicycle part in the structural optimization for manufacture is a bicycle frame that can be made of steel, aluminium, titanium or composite material. All the parts on the bicycle are customized to the frame. Functional dimensions and angles should be taken into account when selecting the frame geometry. Manufacturers present them in the form of tables with a sketch of the frame itself. The process of development and identification of stress-strain distributions must provide unique insight into the behaviour of composite structures. This paper presents the results of structural analysis of a composite bicycle frame with clearly defined fiber orientations at the level of complex geometry, according to relevant load cases. Emphasis is placed on identifying critical zones on the frame when pedalling and crossing holes in the road. The modern ANSYS software package (module dealing with composites: ANSYS Composite Prep Post) is used for modelling and numerical analysis

Investigation of fatigue life in superalloys structural components

The researches in the field of fatigue failure are mainly aimed at identifying the factors which determine the fatigue behavior of the structural components and their inter relations. It is known that the fatigue resistance of structures is influenced mostly by load sequences, combinations of load types, as well as by materials and their fatigue properties. Therefore, the fatigue life cannot be determined without a thorough analysis of these parameters. Materials known as superalloys exhibit excellent mechanical strength and considerable creep resistance, especially at high temperatures. However, a critical property of these alloys is their resistance to fatigue-crack propagation, particularly at service temperatures. Besides, their fatigue features are not as easily accessible as of other materials (aluminum or steel, for instance). Consequently, determining the fatigue life in superalloy structures is not an easy task to accomplish. Taking into consideration the superalloy properties set in the NASGRO database, this thesis has explored the fatigue life of the real structural components, considering – at the same time – the stresses of both constant and variable amplitudes. The structural components have been designed in the CATIA v5, whereas the propagations of the 2D and 3D fatigue cracks through the structure have been simulated afterwards by the application of the FEM in the FRANC2D/L, and the application of the extended finite element method (XFEM) in the Abaqus software. Special attention has been devoted to the fatigue analysis of the spar of a light aircraft. Numerical methods have been used to identify the weak points on the spar, along with the fatigue life of a spar crack and its direction of propagation. The results gained have corresponded well with the experimental values obtained on the spar of the alloy 2024-T3. Taking into account the good correlation between numerical and experimental values, the same finite element models have been used to estimate the crack life on the spars made of super alloys. The investigations have shown that the majority of the super alloys possess fatigue properties similar to aluminum, and in a few of them the life of fatigue crack has proved to be much longer than in the 2024-T3 alloy

Investigation of fatigue life in superalloys structural components

The researches in the field of fatigue failure are mainly aimed at identifying the factors which determine the fatigue behavior of the structural components and their inter relations. It is known that the fatigue resistance of structures is influenced mostly by load sequences, combinations of load types, as well as by materials and their fatigue properties. Therefore, the fatigue life cannot be determined without a thorough analysis of these parameters. Materials known as superalloys exhibit excellent mechanical strength and considerable creep resistance, especially at high temperatures. However, a critical property of these alloys is their resistance to fatigue-crack propagation, particularly at service temperatures. Besides, their fatigue features are not as easily accessible as of other materials (aluminum or steel, for instance). Consequently, determining the fatigue life in superalloy structures is not an easy task to accomplish. Taking into consideration the superalloy properties set in the NASGRO database, this thesis has explored the fatigue life of the real structural components, considering – at the same time – the stresses of both constant and variable amplitudes. The structural components have been designed in the CATIA v5, whereas the propagations of the 2D and 3D fatigue cracks through the structure have been simulated afterwards by the application of the FEM in the FRANC2D/L, and the application of the extended finite element method (XFEM) in the Abaqus software. Special attention has been devoted to the fatigue analysis of the spar of a light aircraft. Numerical methods have been used to identify the weak points on the spar, along with the fatigue life of a spar crack and its direction of propagation. The results gained have corresponded well with the experimental values obtained on the spar of the alloy 2024-T3. Taking into account the good correlation between numerical and experimental values, the same finite element models have been used to estimate the crack life on the spars made of super alloys. The investigations have shown that the majority of the super alloys possess fatigue properties similar to aluminum, and in a few of them the life of fatigue crack has proved to be much longer than in the 2024-T3 alloy