Stamping dies are used in the Sheet Metal Forming (SMF) process for manufacturing of car body parts. The lead time for design and manufacturing of a stamping die is long, and therefore costly. In the final step of the manufacturing process, manual rework is performed to reach a desired pressure distribution on the forming surfaces in order to achieve a robust process and an approved part within tolerance. The main purpose for this work is to study and further develop a Virtual Rework Method that alters the shape of the forming surfaces of a die to compensate for the displacements of a stamping press that occur during stamping. Measurements were performed to obtain the displacements that occur in the stamping press during stamping. These measurements were performed on a double action deep drawing press of the brand Danly, located at Volvo Cars Tool & Die department in Olofström, Sweden. The measurement yields information of how the stamping press is deflecting and deforming during operation. The measurements are recorded with a Digital Image Correlation (DIC) system that records the displacements of the press during stamping. The displacements obtained in the measurements are then used as constraints to inverse FE- model a press table with topology optimization. This optimized press table is used in the Virtual Rework Method to be able to simulate both the deformations of the press and the internal deformations that occur in the die. Pre-simulations were performed before the measurements to ensure that the blank holder plate used in the measurements would withstand the applied blank holder force. These simulations also yield if the displacements were large enough for the ARAMIS DIC system to capture. The FE-model used in this work consisted of a die, blank holder, blank holder plate, outer ram and the optimized press table. The Virtual Rework Method was applied on the FE-model, where the result concludes that the altered shape of the deformed forming surfaces is almost identical to the shape of the nominal forming surfaces. However, an inversed modelled structure that represents the behavior of the outer ram is required to apply the Virtual Rework Method on the blank holder. This inversed modelled structure could be created from the displacements obtained in the measurements. To apply the Virtual Rework method on the punch, further measurements are required, where the position of the ARAMIS DIC system is altered, or an additional ARAMIS DIC system is used. / Pressverktyg används i plåtformningsprocessen vid tillverkning av karossdelar. Ledtiden för konstruktion och tillverkning av ett pressverktyg är lång och därför kostsam. I det sista steget i tillverkningsprocessen utförs manuell bearbetning för att nå en önskad tryckfördelning på formningsytorna, vilket ger en robust process och en godkänd del inom toleranserna. Huvudsyftet med detta arbetet är att studera och vidareutveckla en virtuell fläckningsmetod som korrigerar formningsytorna på dynan för att kompensera för de förskjutningar som uppstår i en stämplingspress under stämpling. Mätningar har utfördes för att erhålla förskjutning som uppstår i en stämplingspress under stämpling. Dessa mätningar utfördes på en dubbelverkande djupdragningspress av märket Danly, som finns hos Volvo Cars Tool & Die avdelning i Olofström, Sverige. Mätningen gav information om hur pressen deformeras under stämpling. Mätningarna registreras med ett Digital Image Correlation (DIC) system som registrerar pressens förskjutningar under stämpling. Förskjutningarna som erhållits i mätningarna användes sedan som randvillkor för en inversmodell för topologioptimering av ett pressbord. Detta optimerade pressbord används sedan i den Virtuella fläckningsmetoden för att kunna simulera både pressens stelkroppsrörelse och de interna deformationer som uppstår i pressverktyget. En förstudie utfördes innan mätningarna för att säkerställa att den plåthållarplattan som användes i mätningarna skulle motstå den applicerade plåthållarkraften. Denna förstudie gjordes även för att säkerhetsställa att förskjutningarna som uppstår i plåthållarplattan var stora nog för att ARAMIS DIC systemet skulle registrera dem. FE-modellerna som användes i detta arbete bestod av en dyna, plåthållare, plåthållarplatta, yttre slid och det optimerade pressbordet. Den Virtuella fläckningsmetoden applicerades på FE- modellen, där resultatet gav slutsatsen att den korrigerade formningsytan med applicerad belastning är nästintill identisk med formen på den nominella formningsytan. En inversmodellerad struktur som representerar beteendet hos den yttre sliden krävs emellertid för att tillämpa den Virtuella fläckningsmetoden på plåthållaren. Denna inversmodellerade struktur kunde erhållas från de förskjutning som erhölls i mätningarna. För att tillämpa den Virtuella fläckningsmetoden på stansen krävs ytterligare mätningar, där ARAMIS DIC systemets position ändras eller ett ytterligare ARAMIS DIC system används. / Reduced Lead Time through Advanced Die Structure Analysis - Vinnova

Thin polymer materials are today widely used in industry and production. An ordinary food package can have around six different layers of materials laminated together to obtain the desired protection. To obtain an efficient usage of these materials simulations are often required. But the simulations require precise and good material models and properties. To obtain these properties through standard tests are difficult as normal strain gauges or extensometers can’t be used. Much research has been done on this kind of material. But still, the knowledge of the behaviour in certain cases is limited. One such area is the tearing of a laminated material.   The first objective of the work is to test a new measurement method, Digital Image Correlation (DIC), for thin polymer films and test if the method is applicable. DIC is a non-contact measurement technique that measure the deformation of a stochastic pattern. The strain is then calculated from this deformation. These strains can then be used to obtain material properties and behaviour. The second objective is to test the tearing behaviour of a laminate.   The material used is a laminate between a PET (100 μm) and LDPE (25 μm) film. When testing the single layers they were carefully delaminated with a plexiglass staff. As the material can be anisotropic the materials were tested in five directions: Machine Direction (MD); 22,5˚; 45˚; 67,5˚ and Cross Direction (CD). The work and tests were performed at BTH Campus Gräsvik.   An experimental setup for DIC with the usage of chalk spray and backlight was tested. Five tests were performed with and without DIC pattern. It was calculated that the DIC specimens were within standard deviation of the reference tests. GOM Correlate was used to evaluate the strains and visualise the distribution. The strains obtained were also used to calculate the true stress of the specimens and estimate the Poisson’s ratio.      Through testing it was concluded that the tearing of the laminate led to delamination in one of the legs. The delamination always appears in the leg where the LDPE film will experience tensile forces. The crack also angels towards 45˚. By testing single layers it was found that the PET film angles when teared, likely caused by the anisotropy of the material.      An experimental setup for the use of DIC for thin polymer has been developed. This method can be used for future measurements and improvement of material models. The behaviour of laminated tearing was observed and some conclusions could be drawn about its behaviour. However, a lot more work is required on this subject.

The main intention of this thesis work was to investigate the effect of strain rate on continuum and pre-cracked polymer failure. Low-Density Polyethylene (LDPE) was chosen to study experimentally and numerically. In order to cover wide range of strain rates, four specific strain rates were selected for the uniaxial tensile tests. To perform the tests, cyclic loading and unloading with relaxation was utilized in the room temperature for continuum specimen and for pre-cracked specimen monotonic tensile test till failure was utilized. Through Digital Image Correlation (DIC) the local strain distribution was assessed through the specimen and the deformation was compared with simulation results. Based on the extensive literature review of material models from PolyUMod library among Viscoplastic models, the Three Network Viscoplastic (TNV) model was selected to proceed with the calibration. The motivation behind choosing TNV model is it's capability of capturing load-unload curves, different strain rates as well as non-linear responses. Furthermore, it was seen that among Viscoplastic models, TNV has the lowest average errors which plays a vital role in this case as the accuracy of FE simulation directly depends on the calibration results. From the experimental results it was safe to say that with increasing strain rates LDPE films tend to get stiffer and stronger both in continuum and pre-cracked. Through the calibration it was seen that the predicted curves were in reasonable agreement with experimental ones. Hence,the calibrated model was exported as python script into Abaqus CAE to perform the simulations. The comparison was done and discussed in details between the simulation and experimental data in three orientations; MD (Machine Direction), CD (Cross Direction) and 45 direction.

Further understanding of mesoscale slip mechanics is crucial to future development of polycrystalline metals with improved performance. The research contained within this thesis aims to characterize localized mesoscale slip on slip bands further through two studies. First, a comprehensive comparison of slip system identification techniques was carried out to further validate each method as well as compare advantages and disadvantages of each. Second, slip bands in the presence of grain boundaries were studied to better characterize the dislocation content and behavior. In the first study, the use of SEM-DIC, AFM, ECCI, and HR-EBSD to characterize slip-system activity was assessed on the same material volume of Ti-7Al. This study presents a robust comparison of the various methods for the first time, including an assessment of their advantages and disadvantages, and how they can be used effectively in a complementary manner. The analysis of the different approaches was carried out in a blind manner independently at three different universities. A Ti-7Al specimen was deformed in uniaxial tension to approximately 3% axial strain, and the active slip systems were independently identified using (i) trace analysis; (ii) in-SEM digital image correlation, (iii) observations of residual dislocations from ECCI, and (iv) long-range rotation gradients through HR-EBSD, with consistent trace identification in all cases. Displacement data from AFM was used to augment the SEM-DIC displacement data by providing complementary out of plane displacement information. Furthermore, short-range dislocation gradients (measured by DIC) provided insight into the residual geometrically necessary dislocation (GND) content, and was consistent with the GND content extracted from EBSD data and ECCI images, confirming the presence of residual GNDs on the dominant slip systems resulting in visible slip bands. These approaches can be used in tandem to provide multi-modal information on slip band identification, strain and orientation gradients, out-of-plane displacements, and the presence of GNDs and SSDs, all of which can be used to inform and validate the development of dislocation-based crystal plasticity and strain gradient models. In the second study, shear strain profiles along slip bands in a modified Rolls-Royce nickel superalloy (RR1000) were analyzed for a tensile sample deformed by 2%. The strain increased with distance away from a grain boundary (GB), with maximum shear strain towards the center of the grain, indicating that dislocation nucleation generally occurred in the grain interior. The strain gradients in the neighborhood of the GBs were quantified and generally correlated with rotation about the active slip system line direction. This leads to an ability to determine the active slip system in these regions. The dislocation spacing and pileup stresses were inferred. The dislocation spacing closely follows an Eshelby analytical solution for a single ended pileup of dislocations under an applied stress. The distribution of pileup stress values for GBs of a given misorientation angle follows a log-normal distribution, with no correlation between the pileup stress and the GB misorientation angle. Furthermore, there is no observed correlation between various transmissivity factors and slip band pileup stress. Hence it appears that the obstacle strength of any of the observed GBs is adequate to facilitate the dislocation pileups present in the slip bands. However, slip band transmission does correlate with transmissivity factors, with the current study focusing on the Luster and Morris m'-factor. Observation of strain profiles of transmitted bands indicate dislocation nucleation locations.

Pour améliorer la caractérisation et le dimensionnement des disques de turbines pour les moteurs d’avion, le motoriste Safran Aircraft Engines (SAE) développe des modèles de comportement, des lois d’endommagement et des critères de fatigue plus adaptés aux chargements réels. Pour aider à cette démarche, le but de cette étude est de développer un modèle de plasticité adapté à l'Inco718DA (un alliage à base nickel utilisé dans la fabrication des turbines haute pression), capable de représenter différents chargements (monotone, cyclique symétrique et non-symétrique). La proposition puis l'identification du modèle a été possible grâce à une campagne expérimentale favorisant des tests complexes et innovants aux essais de fatigue nombreux et coûteux. Les essais faits incluent un essai monotone avec décharges élastiques, un essai multi-niveau à Rε=-1 et deux essais multi-niveau à Rε=0 pour mieux caractériser la relaxation de la contrainte moyenne et un essai pour quantifer le rochet. Le comportement cyclique du matériau a été identifié en utilisant un écrouissage cinématique non saturant avec des éléments s'inspirant de la surface mémoire de Chaboche. Un des défis a été d'obtenir des boucles stabilisées "pointues" dans un régime de plasticité cyclique saturante, en utilisant une évolution du paramètre Γ en fonction de la déformation plastique équivalente maximale (prefacteur du terme de rappel de la loi d'écrouissage cinématique).Une deuxième difficulté apparaît dans la description de la relaxation de la contrainte moyenne, phénomène complexe avec un impact considérable sur la durée de vie en fatigue. Dans le chapitre 3, un modèle est proposé pour la caractérisation de la relaxation partielle de la contrainte moyenne. Une originalité du modèle est l'idée que la relaxation incomplète est une conséquence directe de la différence entre la charge et la décharge de la boucle de hystérésis. Le paramètre choisi pour décrire cette différence a été le préfacteur du terme de rappel Γ, pour lequel la thermodynamique donne de la liberté. Par rapport à d'autres lois d'écrouissage confirmées, notre modèle présente l'avantage d'utiliser un seul terme de rappel, mais avec une formulation plus complexe. En plus, le modèle est incrémental (écrit en taux/en vitesse), il peut donc prendre en compte des chargements complexes tels que aléatoires ou plus simplement tels que dans les essais multi-niveaux pilotés en déformation. Dans le dernier chapitre de la thèse, une campagne biaxiale vaste est présentée, avec les développements pour réaliser des essais biaxiaux pilotés en déformation. La campagne biaxiale a été réalisée sur des éprouvettes cruciformes en utilisant des capteurs LASER et des mesures de champs mono et stéréo analysées en utilisant la Corrélation d'Images Numeriques (CIN). Pour analyser la relaxation de la contrainte moyenne en biaxial un moyen de mesure et de contrôle fiable a dû être développé, adapté aux déformations plastiques élevées qui apparaissent dans la région d'intérêt de l'éprouvette. En utilisant la corrélation d'images intégrée (I-CIN) avec des fonctions de forme adaptées sur un seul élément et des calculs sur GPU, on a obtenu des fréquences de mesure de 100~Hz. En plus, avec sa précision et vitesse, I-CIN a été une technique adaptée pour contrôler une machine d'essais multiaxiale hydraulique. Un résultat important obtenu quand on a réalisé des essais equi-biaxiaux pilotés en déformation a été l'observation d'une relaxation de la contrainte moyenne très faible par rapport au cas uniaxial. Ce résultat doit être pris en compte dans les études futures avec des calculs éléments finis sur l'éprouvette complète. / To improve the characterization and design of aircraft engine turbine disks, the propulsion systems manufacturer Safran Aircraft Engines (SAE) develops constitutive equations, damage laws and fatigue criteria that are more adapted to real loadings. As part of this effort, the purpose of the current study is to develop a plasticity model for Inco718DA (a nickel-based alloy used in the manufacturing of high-pressure turbine disks), capable of representing several loading conditions (monotonic, symmetrical and non-symmetrical cyclic loading). The identification of the model was possible thanks to a uniaxial campaign, favoring a few but complex, innovative, tests to numerous costly fatigue tests. The tests we performed include a monotonic test with elastic discharges, a multi-level Rε = -1 test and two multi-level Rε = 0 tests that better quantify the mean stress relaxation and a test to identify ratcheting. The cyclic behavior was identified using a non-saturating kinematic hardening law with elements of Chaboche's memory surface. One of the challenges was to obtain sharp stabilized loops in a saturated cyclic plasticity regime, which was possible using parameter Γ evolving with respect to the maximum equivalent plastic strain, in the back-stress of kinematic hardening rule.A second difficulty appears in the description of mean stress relaxation, which has a considerable impact on fatigue lifetime. In chapter 3, a model is proposed for the description of the incomplete mean stress relaxation. One of the originalities is the idea that incomplete mean stress relaxation is a direct consequence of the difference between the loading and the unloading part of the hysteresis loop. The parameter we used to describe this difference, was the prefactor of the back-stress term Γ, for which the thermodynamics allows liberty. When compared to confirmed kinematic hardening laws that model non-zero mean stress relaxation, our model presents the advantage of using only one backstress, even if its description is more complex. Moreover, the model is incremental (written in a rate form in chapter 3 section 5) so it can take into account complex loadings such as multi-level strain-controlled tests.In the last chapter of the thesis, a vast biaxial campaign is presented, along with developments to make biaxial strain-controlled tests. The biaxial campaign was performed on cross-shaped samples using LASER sensors, mono and stereo full-field measurements using Digital Image Correlation (DIC). In order to analyze biaxial mean stress relaxation, a reliable measurement and control method had to be developed for the high plastic strains occurring in the region of interest of the sample. By using an Integrated-DIC (I-DIC) algorithm with adequate shape functions on one element and GPU computations we were able to obtain measurement frequencies of 100 Hz. Moreover, with its precision and speed, I-DIC proved to be a suitable technique for controlling a biaxial hydraulic machine. An important result obtained when performing equi-biaxial I-DIC strain-controlled tests was that there was very little biaxial mean stress relaxation, with respect to the uniaxial case. This result will have to be taken into account in future studies when performing finite element computations of the whole sample.

<p>Shallow foundations are used to support small-to-medium size structures, and their capacity derives from the strength of strong, near-surface soils. The design of shallow foundations is done by proportioning the plan dimensions of the foundation element by considering three factors: (1) the structural stability of the foundation, (2)  the allowable bearing pressure of the soil supporting the foundation to prevent ultimate bearing capacity failure, and (3) the tolerable total and differential settlements to meet serviceability requirements under normal working loads. Different theories have been developed to estimate the bearing capacity of a foundation, mostly relying on the Terzaghi (1943) form of the bearing capacity equation with the superposition of three terms. The partly theoretical and empirical methods of bearing capacity predictions rely on an assumed failure mechanism within the soil. In addition, the soil itself is considered to be a perfectly plastic material and its strength is accounted for through non-dimensional bearing capacity factors. However, the boundary-value problem of footing penetration, in reality, is quite complex and the use of the traditional bearing capacity, with use of the principle of superposition, leads to somewhat conservative results. The challenges involved in a footing penetration problem emanate not only from the difficulties in estimating soil strength parameters but also because the footing penetration problem involves large deformations and strains, which localize to form shear bands that propagate in the soil domain until the "collapse" of the sand-footing system.</p> <p>The overarching aim of this research is the study of the response of shallow foundations on clean silica sands by investigating the measured bearing capacities and getting insights into the failure mechanisms that develop as a result of the soil displacements below the base of the foundation element. This was experimentally achieved using a combination of physical modelling (by performing a series of model footing 1g load tests inside a novel half-circular calibration chamber) and image analysis (using digital image correlation technique). The load-settlement response of the model footings is investigated by performing displacement-controlled load tests on model strip and square footings placed either on the surface or embedded in the sand samples of varying relative densities prepared inside the calibration chamber using the method of air-pluviation. A series of high-resolution images collected during model footing loading were analyzed using the digital image correlation (DIC) technique to obtain the displacement and strain fields in the sand domain. Two fully characterized silica sands, Ohio Gold Frac (OGF) and Ottawa 20-30 (OTC) are used in the research. Different testing variables that were considered in the experimental setup are: (1) sand particle morphology, (2) sand sample's relative density, (3) sand layer thickness, and (4) footing shape, size, and embedment depth. A detailed test matrix was formulated to isolate these variables and study the effects of each on both the bearing capacity and the associated failure mechanism. Accordingly, this article-based dissertation is organized to describe the results of three studies.</p> <p>In the first study, the effects of relative density and particle morphology on the bearing capacity and failure mechanism of a model strip footing were investigated. This was done by using two silica sands: OGF sand and OTC sand, both the sands have comparable mineralogy, gradation, and particle sphericity; however, they have markedly different values of particle roundness. Samples of both sands were prepared at relative densities of 90%, 65%, and 30%. The evolution of the footing's collapse mechanism was considered by selecting relevant points on the load-settlement curves. A novel methodology was adapted to record the thickness of the shear band that developed in the sand domain. In the second study, the effects of the presence of a stiff layer below the strip footing were investigated. This was achieved by load testing the model strip footing on OTC sand layer of limited thickness. To simulate the sand-bedrock system, a half-circular steel plate supported by a stack of hollow concrete blocks was used. Load tests on model strip footing were performed on OTC sand samples without the presence of a stiff base and on the sand samples underlain by a stiff base located at depths equal to 0.5B and 1B below the base of the footing. The effect of the presence of the stiff base on the limit unit bearing capacity of the footing and stiffness of the sand-footing system were investigated. In addition, the contours of the cumulative maximum shear strains, horizontal displacements, and vertical displacements that develop in the sand layer are presented for both cases of with and without the presence of the stiff base. In the third study, the effects of footing geometry and embedment on the bearing capacity and failure mechanism were investigated. Load tests were performed on surface and embedded model strip and square footings on dense, medium dense, and loose OTC sand samples. The effects of choice of flow rule (associative versus non-associative) on the bearing capacity calculation and the increase in bearing capacity due to footing embedment (bearing capacity ratio) were determined. In addition, a framework is proposed to experimentally determine the shape and depth factors using strip and square footings of equal widths considering the flow rule non-associativity, conditions of low confinement, and different loading paths.</p> <p>The results of the experimental program presented in this research on bearing capacity, displacement fields, strain fields, and failure mechanisms for different footing sizes and shapes under different testing conditions show that that the footing's collapse mechanism depends on the relative density of the sand sample, sand particle morphology, and the footing geometry. Significant differences in the bearing capacity of model footings due to sand particle morphology and sand sample density were observed. The shear band thickness is also shown to be dependent on the shape of the sand particles. It was also observed that the scale effects in model footing tests are closely related to sand dilatancy. For a sand layer of finite thickness underlain by a stiff base it is shown that the critical depth of the stiff base is greater for stiffness calculation than that for the bearing capacity calculation. DIC analysis results provided valuable insights to the footing penetration problem and corroborated the theoretical knowledge about the failure modes in sandy soils. It is shown that the failure mechanism extend deeper and wider for sands with angular particles as compared to the sand with rounded particles. DIC analysis also revealed that as the distance between the footing base and stiff layer reduces, the shear bands are more readily formed but their lateral extents are reduced considerably. The high-quality experimental data provided in this dissertation is aimed to be useful to researchers working on the validation of numerical simulations of footing penetration in sands.</p>

No description available.

TBF 1180 steel was studied under various conditions focusing on the correlation of ductility and amount of retained austenite. Samples were prepared from sheet stock and then strained using limiting dome height tooling (LDH), a standard uniaxial test frame, and a tensile stage for use in an electron microscope. The steel was observed in plane, biaxial, and uniaxial strain to determine its effect on retained austenite transformation and ultimately, ductility. Retained austenite was observed using a scanning electron microscope (SEM) equipped with an electron backscatter detector (EBSD) to distinguish the different phases present. Initial austenite levels were around 5% by volume and was quickly reduced as the sample was strained. The biaxial samples were the slowest to transform, having about 2.5% austenite at .05 effective strain, which allowed the specimen to reach an effective strain of .3 with 1.1% austenite remaining. In contrast, the plane strain samples had the fastest rate of transformation having only 1.2% austenite at .05 effective strain and .7% austenite at a final effective strain of .18. Both forms of uniaxial, (in-situ and ex-situ), were near identical, as expected, and exhibited an austenite transformation curve between that of the plane and biaxial curves. The uniaxial austenite level at .05 strain was 2.1% and was able to reach about .15 strain with a final austenite percentage around 1%. It was concluded that the biaxial strain path had the greatest ductility due in part to its slower austenite transformation rate while plane and uniaxial strain paths were not as ductile with their faster austenite transformation rates.

The goal of this thesis is to improve the predictive capability of Finite element (FE) by gathering data from experimental test and implement the characteristics into the material model that is used. FE is a commonly used method to predict the mechanical behavior of materials and components during applied forces. Therefore, it’s an important part of product development since it gives an opportunity to lower the costs as well as saving resources since it reduces the number of experimental tests. The method for this thesis was to first simulate tensile tests in Abaqus and then to analyze its results. Once all the simulations were done, we replicated the simulation with experimental tests. This was done with DIC (Digital Image Correlation) to help gather data. Since the goal of this thesis is to see how the predictive capability of the FEM-simulation can be improved the results are compared and discussed to see what from the FEM-simulation matches the DIC results and what does not. This will help understand what in the material model that needs to be changed to better match the testing. DIC is a non-contact method that is used to measure deformations and strain locally over an area which results in a more detailed view of the mechanical behavior of the material. The idea of using DIC during this thesis is to sample enough valuable data and apply it to the original material model of the FE-simulations to increase the predictive capability. After the results from the experimental tests were analyzed it was clear that there were both resemblances and differences in the results, for example the Young’s modulus in the FEM-calculations was higher than it was for the experimental tests, Yield strength was lower in the FEM-calculations compared to the experimental tests, maximum load at fracture was lower in the FEM-calculations compared to the experimental tests and elongation was lower in the FEM-calculations compared to the experimental tests. The FEM-calculations were based of the assumptions that the material was homogenous but that wasn’t the case for the experimental tests. Due to the strain varying over the tests the material model could be improved by adding a statistical variation, to all the elements to give them varying mechanical properties simulate how the strain vary more correctly over the specimen.

Swine stocks are endemically infected with the major porcine pathogen Streptococcus (S.) suis. The factors governing the transition from colonizing S. suis residing in the tonsils and the exacerbation of disease have not yet been elucidated. We analyzed the sudden death of fattening pigs kept under extensive husbandry conditions in a zoo. The animals died suddenly of septic shock and showed disseminated intravascular coagulopathy. Genotypic and phenotypic characterizations of the isolated S. suis strains, a tonsillar isolate and an invasive cps type 2 strain, were conducted. Isolated S. suis from dead pigs belonged to cps type 2 strain ST28, whereas one tonsillar S. suis isolate harvested from a healthy animal belonged to ST1173. Neither S. suis growth, induction of neutrophil extracellular traps, nor survival in blood could explain the sudden deaths. Reconstituted blood assays with serum samples from pigs of different age groups from the zoo stock suggested varying protection of individuals against pathogenic cps type 2 strains especially in younger pigs. These findings highlight the benefit of further characterization of the causative strains in each case by sequence typing before autologous vaccine candidate selection.