Computer simulation is an essential tool in the development process of childseats, particularly when it comes to ensuring the safety of child passengers.As awareness regarding child passenger safety continues to grow, the use ofsuitable materials in the development of child seats becomes increasinglycrucial. Numerical simulations play a vital role throughout the entiredevelopment phase, enabling accurate analysis and evaluation. Toeffectively reduce development costs and time, it is imperative to have amaterial model that accurately predicts the behavior of materials innumerical simulations. This enables optimized performance of child seatswhile maintaining safety standards. The objective of the thesis is to implement a standard procedure forextracting material data for numerical modelling of foam materials andvalidating it. In this study, material models available in LS-DYNA, such asMAT_083 and MAT_057 for foam materials, are utilized along withcompression test data to create the material model. The model is furtherenhanced by optimizing the material parameters to establish a correlationbetween the test and simulation results. The improved material model is thenvalidated by comparing it with the impact drop test results. However,THULE's current impact drop test equipment is not considered accurate orefficient, and addressing this issue is one of the main objectives of thisthesis. Within this thesis, the identified problems are thoroughly examined,and suitable solutions are proposed to ensure the accurate extraction ofmaterial data and its validation, particularly when introducing new foammaterials.

Many of today’s engineering advancements rely on minerals such as copper, gold and iron. For this reason, the mining industry plays an important role for the development of society and technological wonders. Mining excavators are commonly used tools for extracting the minerals from the mine. Mining excavators are large machines used to breakdown, penetrate and load the rock ores onto trucks that transport the minerals. During the dynamic loading, the excavator bucket experiences significant amount of wear and tear that negatively affects the production by increasing the downtime. The bucket teeth are arguably the most worn parts of the bucket and are responsible for significant amounts of downtime. This thesis aims to provide a better understanding of the load and wear on the bucket teeth of large scale mining excavators used in Bolidens Aitik copper mine in Sweden. Because of how much wear and tear the bucket teeth are exposed to, there is a need to better understand the wear behaviour of the teeth and for the whole bucket in general. This understanding can then be used to improve the service life of the teeth and other parts of the bucket and thus increase work efficiency and reduce downtime. This project was divided into two parts. The first part consisted of regular field measurements to follow the wear on the bucket for about two weeks of digging and loading. The gathered data was then analysed to provide a better understand about the wear behaviour. The second part was to develop a numerical model that could predict the wear on the bucket and could be verified by the field measurements. The field measurements consisted of seven 3D laser scans of the bucket starting with brand new teeth. At the time of the last scan, the buckets total loaded tonnage was approximately 542 kton and the excavator had operated in total of approximately 195 hours. After the raw data from the scans was gathered and analysed, various information about the wear behaviour on the teeth was achieved. The 3D scanned data was also used to provide a complete wear development cycle which allowed to track the wear of any point in the bucket. The method could also be used to create animations of the teeth as they were being worn. From the results, it was concluded that the wear rate for the teeth slowed down and even converged as the geometry changed due to wear. When comparing all nine teeth on the bucket, it was also found that the middle teeth on the bucket were most exposed to wear. The most worn tooth was found to lose around 50 kg of weight after approximately 117 operating hours, which accounts for 40 % of the original weight. The animations from the complete wear development results also showed how the individual teeth and the whole leading edge with all nine teeth were being worn as the buckets loaded tonnage increased from 0 to 542 kton. The numerical model consisted of simulations of loading with the rocks being modelled with the Discrete Element Method (DEM). These were divided into four cases, the first being with the bucket with all new teeth. The second bucket with a mixture of new and worn teeth. The third bucket with all worn teeth and then finally the fourth bucket in which a new tooth geometry was tested. The numerical model showed promising results and potential for being a reliable way to predict the wear on the bucket. The results showed that both the penetration force and wear for the middle teeth was higher than the other neighbouring teeth. It also showed that the completely worn teeth had a lower wear rate than the new teeth which is in agreement with the results from field measurements. Other factors such as tooth shape and length were also observed to have a significant impact on the wear and penetration force. Lastly, the new teeth geometry also showed potential for design improvements in terms of wear resistance but can be further optimised. From the new teeth geometry, a suggestion was given for using an existing tooth system that might be more wear resistant.

The motivation behind the project was to update the Livermore Software Technology Corporation (LSTC) Hybrid III 95th percentile finite element model, such that the neck assembly response under varying simulated loading conditions equals that of the federally regulated Hybrid III 95th percentile anthropomorphic testing device (ATD). The family of Hybrid III crash test dummies approximate the physical properties and response of the human body in a frontal automotive crash. The Hybrid III is used to assess the effectiveness of vehicle restraint systems. LSTC offers Hybrid III finite element models for use in their Multiphysics simulation software package, LS-DYNA. The Hybrid III models are used as cost-effective alternative to physical crash tests in the development of vehicle crashworthiness. However, the neck response of the LSTC Hybrid III 95th percentile model in simulation was poorly correlated to that of the physical Hybrid III neck in corresponding tests. The source of the dissimilarity was inadequate dimensions, element behavior, and material properties of the neck. To improve correlation to the physical ATD, a number of modifications were made to the LSTC Hybrid III 95th percentile neck. Development of the neck model began with improvements in mass and geometry. Element formulation and element discretization were altered to improve model durability and accuracy. A mesh convergence study and simulation under extreme-severity loading were completed to validate the foregoing model alterations. Test data from a physical compression test and NASA-performed Neck Sled Tests were collated with data from simulation to adjust material type and material properties. The model was further calibrated according to Code of Federal Regulations neck calibration test response requirements. The resulting neck model developed in LS-DYNA exhibited improved dynamic characteristics and reliability under both low and high-severity loading. Computational efficiency was enhanced along with model tendency to normally terminate under excessive loading. The updated model moreover demonstrated consistent element behavior and realistic feedback in bending. The revised neck model will be adopted by NASA for use in predicting potential occupant injury during spacecraft landing. A similar model with reworked material properties attuned to higher loading will be implemented into the full consumer version of the Hybrid III 95th percentile model for employment in high-severity frontal crash simulation.

High-strength steel (HSS) conforming to ASTM A1035 is becoming increasingly used in various structural applications, including in high-rise buildings and bridges. Due to their chemistry and manufacturing process, ASTM A1035 steel bars result in a combination of high tensile strength to yield ratio and varying levels of corrosion resistance. One potential application of ASTM A1035 bars is in the blast-resistant design of concrete structures, where their use can allow for reduced steel congestion, and increased blast resistance. Despite their high initial cost, stainless steel (SS) reinforcing bars are also seeing increased use in concrete construction. Solid stainless steel bars are referenced in ASTM A955, which is applicable to various stainless steel alloys. In addition to their inherent corrosion resistance, most stainless steel bars possess greater tensile strength, and importantly, exceptional ductility, when compared to ordinary steel reinforcement. This unique combination of strength and ductility makes SS bars well-suited for blast design applications. The overarching aim of this thesis is to gain better understanding of the blast behavior of RC flexural members designed with high-strength (HSS) and stainless steel (SS) reinforcement. This objective is achieved through a combined experimental and numerical research program. As part of the experimental research, a large set of beams, subdivided into three series, are tested under either quasi-static bending or simulated blast loads using the University of Ottawa shock-tube. Series 1 (HSC-HSS) and Series 2 (HSC-SS) aim at examining the effects of blast detailing (as recommended in modern blast codes,) on the quasi-static, blast and post-blast behaviour of high-strength concrete (HSC) beams reinforced with either ASTM A1035 high-strength bars (8 beams) or ASTM A955 stainless steel bars (16 beams). In addition to the influence of detailing, the effects of steel grade/type, steel ratio and steel fibers are also studied. Series 3 further studies the benefits of combining higher grade or higher ductility reinforcement, with more advanced ultra-high performance concrete (UHPC). This series includes 20 UHPC beams built with either ordinary, HSS or SS reinforcing bars (UHPC-NSS, UHPC-HSS and UHPC-SS). In addition to the effect of steel grade/type, concrete type, steel ratio and steel detailing are also studied. The results from Series 1 and 2 demonstrate the benefits of implementing high-strength and stainless steel reinforcement in HSC beams subjected to blast loads, where their use leads to increased blast capacity, reduced support rotations, and higher damage tolerance. The results further demonstrate the benefits of “blast detailing” on the ductility and resilience of such beams, under both static and blast loads. The results also show that the use of steel fibers can be used to relax blast detailing in the beams with high-strength or stainless steel by increasing the required tie spacing from d/4 to d/2. The results from Series 3 confirm that the use of UHPC in beams enhances flexural response (in terms of strength and stiffness), which in turn results in superior blast resistance. Conversely, the high bond capacity of UHPC makes such beams more vulnerable to bar fracture. Increasing the steel ratio is found to effectively increase the failure displacement and ductility of the UHPC beams. The use of high-strength steel is found to increase load capacity and blast resistance, while the use of stainless steel results in remarkable ductility, which further enhances beam response under blast loading. As part of the numerical research program, the static and blast responses of the test beams are simulated using either 2D or 3D finite element (FE) modelling, using software VecTor2 and LS-DYNA. The numerical results show that the 2D FE modelling using software VecTor2 can provide reliable predictions of the static and blast responses of the HSS or SS reinforced HSC beams built with varying detailing, in terms of load-deflection response, cracking patterns, failure mode, displacement time histories and dynamic reactions. Likewise, the 3D FE modelling using software LS-DYNA with appropriate modelling of UHPC (using the Winfrith Concrete or CSCM models) can well predict the blast responses of UHPC beams with ordinary, high-strength and stainless steel, in terms of displacement/load-time histories, damage and failure modes.

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No description available.

<p>Masonry is one of the most commonly used materials in building construction throughout the world. Unreinforced masonry (URM) walls typically have very low flexural capacities and tend to posses brittle failure modes. Due to brittle nature of URM walls, it is critical to predict the behaviour of the wall when exposed to extreme out of plane loadings such as blast loads. An effective way to enhance the ability of unreinforced masonry walls to withstand blast loads and consequently to limit the amount of wall damage is imposing arching mechanism on the wall. Since carrying out physical experiments to study the response of URM walls subjected to blast load is both dangerous and expensive, finite element modeling has become more attractive to researchers. In this research, an unreinforced one-way arching wall is simulated using the finite element program LS-DYNA and its behaviour subjected blast loading is studied. The model is constructed based on the data recorded earlier during a physical blast experiment. Close agreement was observed between the numerical and experimental results which validated the developed model. A sensitivity study is then performed where the influence of variation of some input parameters such as mortar strength, coefficients of friction, scaled distance, boundary condition, wall height and the effect of two-way arching action on the wall’s response is evaluated. The most influential parameters in this study found to be the scaled distance, wall height and two-way arching action. Smaller scaled distances result in high deflection and as the scaled distance increases the maximum deflection decreases. The wall height also significantly affect the wall’s response to blast loads, i.e. the taller the wall the larger the maximum displacement. It is also concluded that two-way arching action can significantly reduce the wall’s maximum deflection.</p> / Master of Applied Science (MASc)

This diploma thesis is concerned with the numerical analysis of welded aluminim structures. In these structures, there are significant decreases in the mechanical properties at the area of the weld and in the heat affected zone as a result of welding. Within this thesis, simulations of quasi-statically loaded welded joints made from EN AW-6082 T6 alloy were performed to investigate the load capacity and ductility of these joints. Computations were performed using a programme system based on an explicit finite element method. To describe material anisotrophy, a nonlinear material model called the Weak texture model was chosen. Material properties of the weld and the heat affected zone were considered to be different from base material. The required material parameters were adopted from available literature, however, material tests and indetification procedure of these parameters were described. In comparison with the experimental data, the results of the numerical simulations showed a relatively good ability of models to capture load capacity of studied welded joints. Nevertheless, due to mesh sensitivity of models caused by localization of deformation, it was not possible to determine ductility of these joints.

Le bois est un matériau cellulaire naturel et excellent absorbeur d’énergie. Employé au sein de structures du type limiteur d’impact, il subit de nombreux phénomènes lors d’un cas de chute. Une large campagne expérimentale est réalisée afin d’analyser les réponses en compression du hêtre et de l’épicéa, en fonction de la direction de sollicitation, de la vitesse de déformation pour la plage [0.001-600] s−1 et de deux types de restrictions latérales qualifiées d’extrêmes. La direction longitudinale se révèle la plus sensible à la vitesse ainsi qu’au type de restrictions latérales et les conséquences sur la capacité d’absorption d’énergie du bois sont alors significatives. Par ailleurs, les protocoles développés ont vocation à être déclinés pour un large panel d’essences aux propriétés mécaniques variées. Un modèle matériau élastoplastique, isotrope transverse et sensible à la vitesse de déformation est élaboré à l’aide des techniques multi-échelles et de la micromécanique. Les propriétés élastiques macroscopiques sont estimées à l’aide du schéma d’homogénéisation de Mori-Tanaka à partir de données issues de la microstructure. Un critère de type Gurson étendu reposant sur l’approche micromécanique de l’endommagement ductile est employé pour retranscrire le comportement non linéaire, la densification et le caractère compressible du bois. Des paramètres de dégradation découplés du critère sont appliqués selon la direction longitudinale. La modélisation proposée repose sur une description simplifiée du bois et les résultats numériques associés illustrent la bonne capacité du modèle à reproduire les différentes réponses observées lors d’un cas de chute. / Wood is a natural cellular material, which is widely and advantageously used as shock absorber for the transport of radioactive materials. Accident situations are evaluated based on the 9 m drop test, which allows us to observe the complex crushing behavior of wood. A compressive experimental study is conducted on spruce and beech wood species over a large range of strain rates (from 0.001 to 600 s−1) to investigate the effect of the loading direction and of two extreme lateral confinements. The longitudinal direction is the most sensitive to the effect of strain rate and of lateral confinements which have significant consequences on the energy absorption. Besides, the experimental investigation can be adapted to various wood species with very different mechanical properties. A strain rate dependent elastoplastic model with transversal isotropy is developed using multi-scale and micromechanics techniques. The elastic macroscopic properties of wood are estimated with a Mori-Tanaka scheme and information extracted from the microstructure. The Gurson type criterion based on the micromechanical approach of the ductile damage is used in order to describe the non linear behavior of wood, its densification regime and its compressibility as well. Additionally, uncoupled degradation parameters are applied to reproduce the failure mechanisms involved in the longitudinal response. A simplified description of wood is used within the modeling and the numerical results exhibit the good ability of the model to reproduce the various wood responses during an accident situation.

Collision avoidance systems have become an integrated part of modern vehicles and aim to avoid accidents or mitigate the crash severity for the occupant. For example, the autonomous emergency braking system influences the pre-crash state of the occupant in sitting posture, stress state, or velocity. The occupant might try to retain its posture by activating muscles, which induce muscle bracing and could counteract the movement of the occupant in the pre-crash phase.  Therefore, it is essential to study the influence of active musculature on occupant response in pre-crash and crash events. A finite element human body model (HBM) with and without closed-loop muscle activation control was used to simulate the occupant response during those events. Comparing the HBM responses &amp; head kinematics reveal an influence of muscle bracing in the evasive braking manoeuvre. Simulating the pre-crash and in-crash phase in two stages can provide multiple benefits. However, the correlation between a single-stage simulation (baseline) and a two-stage simulation needs to be investigated. The baseline simulation uses an active HBM to model an occupant during an evasive braking manoeuvre and the muscles are deactivated when entering the frontal impact phase. The parameters of the final pre-crash state, which are needed to mimic the baseline’s response when transitioning from the pre-crash to the in-crash event are investigated in this study. For that reason, sitting position, stress state and velocity are transferred respectively to the initial passive in-crash HBM state. The simulations enabled the comparison of occupant response and calculation of cross-correlation. Each retainment strategy gave a good cross-correlation with the baseline simulation. / Kollisionsundvikande system har blivit en viktig del i moderna fordon där syftet är att undvika olyckor samt att minska allvarhetsgraden av olyckor för de åkande. Ett exempel är nödbromssystem som kan påverka den åkandes initiala tillstånd direkt före en krock som, till exempel, sittposition, spänningstillstånd, eller initial hastighet inför krock. Den åkande kan försöka att bibehålla sin hållning genom att aktivera sina muskler vilket påverkar rörelsen av dess kropp under för-krocks fasen. Det är därför viktigt att studera hur aktiva muskler påverkar rörelsen av kroppen hos den åkande under både före krocksfasen och själva krockfasen. En finit element humanmodell (HBM) med och utan reglerad muskelaktivitet används för att prediktera responsen hos den åkande i båda faserna. En jämförelse mellan simuleringarna visar att aktiva muskler kan påverka åkandekinematiken under bromsningsförloppet. Att simulera fasen före krock och fasen under krock i två steg kan medföra flera fördelar. Korrelationen mellan en enkelstegssimulering (originalsimulering) och en tvåstegssimulering måste dock studeras. Som originalsimulering används en aktiv HBM för att modellera den åkande under för-krocksfasen där den reglerade muskelaktiviteten inaktiveras under krockfasen. I denna studie undersöks den åkandes initiala tillstånd före krocken som behövs för att efterlikna originalsimulerings respons vid övergången från för-krocksfasen till krockfasen. Av den anledningen mappas det passiva HBM-tillståndet till det slutliga tillståndet av före krocksfasen för sittposition, spänningstillstånd respektive hastighet. Simuleringarna möjliggjorde en jämförelse av åkande respons och beräkning av korskorrelation. Varje mappningsstrategi gav en bra korskorrelation med originalsimuleringen.