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.

After the collapse of the roof structure in Tarfalahallen 2020, great attention has been focused on instability of sub-tensioned glulam roof trusses. Investigations were launched to find the reason for the collapse and the cause was instability in the roof truss that supported the roof. As a result, several similar glulam roof trusses in Sweden have been investigated and reinforced to avoid the fate of Tarfalahallen.Inexperience with instability, negligent design procedure and faulty assumptions is an underlying issue with this type of structure. Complex structures can be difficult to analyze without suitable assumptions which means sophisticated method must be used. Proper analysis must be done before construction.To perform this sophisticated analysis, an engineer can use the finite element method to perform global stability analysis. Simple and computationally cheap models can produce meaningful insight, but in most cases the user must be experienced to understand the implications of the results that the finite element method can produce. There is therefore a need for a more detailed, realistic model that can capture failure and motion and visualize it for the user. This thesis has created such a model in the FE-software Abaqus/Standard.By using a wide variety of elements and element sizes a detailed geometry of the connection between primary beam and compression stud, the behavior of the structural components has been analyzed throughout the loading period of the structure. The critical buckling mode was identified, and the complex non-linear interaction of the connection was tracked when buckling occurs.The thesis can be used as a guideline of how to create a FE-model that captures the intricate behavior of the connection between primary beam and compression stud and be used as the groundwork for more complex models in the future.

Hexapod trusses are an important element in many mechanical design systems. The natural frequency and stiffness behavior under geometric and mass variations of such structures is largely undocumented. Furthermore, the ability to quickly model hexapod designs and explore a large design-space in finite element software packages is, in general, time consuming and inefficient. The purpose of this project was to develop software tools that made design-space exploration (modeling and simulation processes) for hexapod structures drastically more efficient. Secondly, the project included an experimental analysis portion to demonstrate the various modal study techniques and to validate finite element analysis predictions. Lastly, the project investigated a specific hexapod design problem as a means of exhibiting the modeling/optimization software tools and to develop an understanding of the natural frequency behavior of hexapods. To this end, the research could be used for the design of telescope secondary support structures and other hexapod optimization engineering problems.