The eXtended Finite Element Method is a partition of unity based method, particularly suitable for modelling crack propagation phenomena, without knowing a priori the crack path. Its numerical implementation is mostly achieved with stand-alone codes. The implementation of the eXtended Finite Element Method in commercial FEA softwares is still limited, and the most famous one including such capabilities is Abaqus TM. However, due to its relatively recent intro-duction, XFEM technique in Abaqus has been proved to provide trustable results only in few simple benchmark problems involving linear elastic material models.In this work, we present an assessment of the applicability of the eXtendend Finite Element Method in Abaqus, to deal with fracture mechanics problems of rubber-like materials. Results are provided for both Neo-Hookean and Arruda-Boyce material models, under plane strain conditions. In the rst part of this work, a static analysis for the pure Mode-I and for a 45o mixed-Mode load condition, whose objective has been to evaluate the ability of the XFEM technique in Abaqus, to correctly model the stress and displacement elds around a crack tip, has been performed. Outcomes from XFEM analysis with coarse meshes have been compared with the analogous ones obtained with highly re ned standard FEM discretizations. Noteworthy, despite the remarkable level of accuracy in analyzing the displacement eld at the crack tip, concerning the stress eld, the adoption of the XFEM provides no bene ts, if compared to the standard FEM formulation. The only remarkable advantage is the possibility to discretize the model without the mesh con-forming the crack geometry. Furthermore, the dynamic process of crack propagation has been analyzed by means of the XFEM. A 45o mixed-Mode and a 30o mixed-Mode load condition are analyzed. In particular, three fundamental aspects of the crack propagation phenomenon have been investigated, i.e. the instant at which a pre-existing crack starts to propagate within the body under the applied boundary conditions, the crack propagation direction and the predicted crack propagation speeds. According to the obtained results, the most inuent parameters are thought to be the elements size at the crack tip hand the applied displacement ratev. Severe diculties have been faced to attain convergence. Some reasonable motivations of the unsatisfactory convergence behaviour are proposed.

Understanding the true behaviour of impacted structures is the only way to assess their robustness under exceptional events such as vehicle collision. The primary objective of this master’s thesis was to perform a finite element parametric investigation on the influence that some parameters have in steel buildings subjected to vehicle impacts. The parameters chosen for the study, involved uncertainties in the material definition and in the load configuration of the bolts used in the impacted column end-connections. By using the Abaqus software, a finite element model of the structure has been created. The five storey steel building considered has been modelled in a simplified manner with the exception of the impacted area which, instead, has been defined in a more detailed fashion. During the simulations, different preload conditions have been used, comparing cases with and without the preload force. Regardless its variation, it has not been observed any increase in the structural resistance. On the other hand, the simulation provided interesting results for what concerns the material variations in the bolts. Although the changes have been small in magnitude, the effect on the structural response during the impact was remarkable. For all the cases considered, an increase of the material ductility, achieved by increasing the ultimate strain at failure, entailed higher resistance of the connections. Various failure modes have been observed when the material properties have been changed. Having clarified the influence of the assumptions made, the results provided helpful information in sight of future studies. Although the model still needs to be validated, the research clarified which of the parameters investigated are to be collected with more attention. Keywords: Vehicle collision, steel building, FE model, Abaqus/Explicit, parametric investigation, bolt preload, bolt material.

Fatigue assessment of welded joints using finite element methods is becoming very common. Research about new methods is being carried out every day that show a more accurate estimation of the fatigue life cycle than the previous ones. Some of these methods are investigated in this thesis for a thorough understanding of the weld fatigue evaluation process.The thesis study presents several methods as candidates for analysis of selected case studies for comparison. The sensitivity of methods towards FE model properties was studied. The ease of implementation for further automatization of the method was highly considered from the early stages of the project. A comparison study amongst feasible methods was then performed after analysis.The selected three case studies provided a wide range of difficulties in terms of geometry and loading and made them suitable for the methods to be evaluated. It should be noted that case studies only with fillet welds were considered during the literature study and analysis. Implementation of some methods on a case study where they have not previously been tested before gave a challenging task during the analysis phase. The proposed method after comparison and ranking of the methods based on several criteria such as accuracy, robustness, etc. was the hot spot stress method. The main advantages of this method are its low computational time, less complexity during both pre- and post-processing, and the ability to work for both solid and shell models.Finally, the report gives a walk-through of several functionalities of the post-processor tool built to enhance workflow for the hot spot based fatigue assessment of welds. Pseudo-codes for some functions of the tool are given for clarity. A summary of the workflow is presented as a flowchart. The outputs of the case studies were then evaluated using the tool and compared with the manual evaluation to check the effectiveness of the tool on different scenarios. The tool shows flexibility in handling different types of weld geometry with good agreement to the results obtained manually but only for welds lying on a flat surface. Some of the advantages of the tool are its capability to handle multiple welds simultaneously and the flexibility to the user in selecting the way the results are presented. Most of the postprocessing steps are automatized, while some require user inputs.

Detta examensarbete handlar om konstruktionsoptimering av en ny och innovativteknisk produkt som riskerar att skadas då användaren av misstag tapparprodukten. Arbetet belyser tidigare studier där dropptester utförts för att insamlakunskap inför viktiga moment i detta arbete. Dropptest av produkten genomfördesoch data samlades in med hjälp av accelerometer och höghastighetskamera.Insamlad data presenteras i olika grafer och beräkningar som beskriversammanstötningsförloppet. Lösningsförslag genereras med CAD programmetCatia V5, sedan simulerades lösningsförslagen i programmet abaqus/explicit eftersamma principer och förhållanden som utfört dropptest visade. Genomfördasimuleringar verifierades med hjälp av insamlad data. Projektgruppen presenterarolika koncept av lösningsförslag till företag X genom olika exempel påkonstruktiva lösningar eller förslag till byte av befintligt produktmaterial. Underprojektets gång uppstod en del svårigheter i de olika delarna av studien, dessadiskuterades i studiens resultat- och metoddiskussion. Avslutningsvis taskonstruktionsoptimeringens inverkan på sociala, ekonomiska och miljömässigaaspekter i anseende. / This thesis is about design optimization of a new and innovative technical productthat risks being damaged when the user accidentally drops the product. The workillustrates previous studies where drop tests have been performed to gatherknowledge before introducing important stages in this work. Droptesting of theproduct was performed and data were collected using an accelerometer and ahigh-speed camera. Collected data are presented in various graphs andcalculations that describes the stages of impact. Solution proposals were generatedwith the CAD program Catia V5, then the solution proposals were transferred tothe program abaqus/explicit were the same principles and conditions that occurredduring the droptest was implemented in the simulations. Completed simulationswere verified using collected data. The project group presents different concepts iiof solution proposals to company X through various examples of constructivesolutions or proposals for replacement of existing product material. During theproject, some difficulties arose in the various parts of the study, these werediscussed in the study's results and method discussion. Finally, the impact ofdesign optimization on social, economic and environmental aspects was taken intoaccount.

This paper investigates the linear elastic behavior of timber shear walls under monotonic prescribed displacement. ABAQUS© 16.4-5, is a numerical finite element software used as the primary analysis methodology.  Parameterized models are created for two shear wall specimens of different geometry concerning door and window configurations. The shear walls are simulated as solid timber framing which is mechanically connected to gypsum sheathing board through fasteners. The primary findings are the linear elastic shear force distribution of the mechanical joints. Additionally, deformations and reaction forces of the shear walls are determined. The overall horizontal shear wall behavior of each specific wall was also studied in the presence of door and window openings. The simulations indicate there is a clear deformation difference in the behaviors of the two shear walls. Furthermore, the highest shear force values of the fasteners are located around the corners of the openings. The findings are supported by other researcher’s experiments and analytical tests, timber shear wall theory and Eurocode design requirements.

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A finite element model is developed in Abaqus Explicit to determine the resistance of Salem Limestone with three levels of initial micro-cracking to high-speed, monotonic impact. A comprehensive description of the model development is included, and the model is validated by comparing simulation impact results to known penetration depths during a mesh refinement study. The uniaxial compression simulations were performed to correlate the HJC damage parameter to the uniaxial compressive strengths from mechanical test data. Then, the HJC damage parameter is compared to the unconfined compression strengths to correlate the micro-crack damage levels. Subsequently, the model was used to determine the correlation of the penetration depths at the finite damage levels. In conclusion, the model described in the paper can adequately predict the penetration depths of the projectiles for a range of micro-crack damage levels. The micro-cracking did/did not affect the penetration depth.

Wave propagation analysis in 1-D and 2-D composite structures is performed efficiently and accurately through the formulation of a User-Defined Element (UEL) based on the wavelet spectral finite element (WSFE) method. The WSFE method is based on the first order shear deformation theory which yields accurate results for wave motion at high frequencies. The wave equations are reduced to ordinary differential equations using Daubechies compactly supported, orthonormal, wavelet scaling functions for approximations in time and one spatial dimension. The 1-D and 2-D WSFE models are highly efficient computationally and provide a direct relationship between system input and output in the frequency domain. The UEL is formulated and implemented in Abaqus for wave propagation analysis in composite structures with complexities. Frequency domain formulation of WSFE leads to complex valued parameters, which are decoupled into real and imaginary parts and presented to Abaqus as real values. The final solution is obtained by forming a complex value using the real number solutions given by Abaqus. Several numerical examples are presented here for 1-D and 2-D composite waveguides. Wave motions predicted by the developed UEL correlate very well with Abaqus simulations using shear flexible elements. The results also show that the UEL largely retains computational efficiency of the WSFE method and extends its ability to model complex features. An enhanced cross-correlation method (ECCM) is developed in order to accurately predict damage location in plates. Three major modifications are proposed to the widely used cross-correlation method (CCM) to improve damage localization capabilities, namely actuator-sensor configuration, signal pre-processing method, and signal post-processing method. The ECCM is investigated numerically (FEM simulation) and experimentally. Experimental investigations for damage detection employ a PZT transducer as actuator and laser Doppler vibrometer as sensor. Both numerical and experimental results show that the developed method is capable of damage localization with high precision. Further, ECCM is used to detect and localize debonding in a composite material skin-stiffener joint. The UEL is used to represent the healthy case whereas the damaged case is simulated using Abaqus. It is shown that the ECCM successfully detects the location of the debond in the skin-stiffener joint.

This master thesis studied the possibilities of implementing new handbook methodologies for sizing of corner and bathtub attachments with respect to static strength.  Parametric studies of corner and bathtub attachments were performed in order to examine the effect of boundary conditions and vital dimensions with respect to static strength. The parametric studies were performed by solving FE-models of attachments with different dimensions. Variables such as flange thickness, end-plate thickness, end-plate length and total attachment width were varied in order to identify geometric trends for prediction of cross-sectional loads.  The FE-models consisted of a bolt, washer and attachment assembly. The bolt was subjected to pre-tension and contact conditions were applied in between each part. The parametric study examined the cross-sectional loads of critical cross sections of the end-plate, bolt, flanges and back.  The parametric study of the bathtub attachment resulted in verification of critical failure modes from earlier handbook methodology, as well as a foundation for a new handbook methodology for sizing with respect to static strength. The parametric study of the corner attachment resulted in an identification of critical failure modes. The non-symmetric configuration of a corner attachment was found to result in larger load distribution in the bolt shank cross section.