Psychopharmacological and behavioural interventions are used to treat challenging behaviours (e.g., self-injury, aggression, stereotypy, bizarre vocalizations) in individuals with intellectual disability (ID), often in combination. However, little is known about the behavioural mechanisms underlying psychopharmacological treatment. Establishing a better understanding of these mechanisms could contribute to improving treatment efficacy. For this study, I conducted repeated functional analyses using single-subject experimental designs to assess the impact of naturally varying dosages of psychotropic medications on behaviour function. Four individuals with ID who engaged in challenging behaviour and were undergoing psychotropic medication changes participated. Medication impact across two topographies for one participant, and three topographies for another participant were assessed, for a total of seven cases. For Analysis 1, I calculated standardized mean differences between baseline and final drug administration phases to estimate the overall effect of medication. I used this information to examine whether response rate following drug administration was related to response rate during baseline, referred to as rate-dependency. Rate-dependency was not observed. Analysis 2 explored the relation between psychotropic medications and behaviour function identified through functional analyses. Challenging behaviour was the dependent variable, while functional analysis conditions and psychotropic medication level served as independent variables. The latter was a quasi-experimental variable given participants’ psychiatric team prescribed changes independent of the researchers. Behaviour function correspondence, defined as no function change after a medication manipulation, was observed across 14 of the 21 medication manipulations (67%). / October 2015

The main task of this thesis is to clarify the impact of demographics on the rate of gross national savings which is considered one of the main elements of economic growth. Demographic trends and theoretical background are presented, which contributes to the understanding of the relationship of savings and the age structure of the population. The assessment of the relationship is done based on cross-sectional analysis of data from period 2009 -2013 for 133 countries, while the effect of demographic forces is studied through dependency rates of unproductive population. In the analysis partial estimates and analogous research with the pre-crisis data are performed. The results suggest that demographic forces leading to the growth of dependency rates negatively influence the savings rate. However, the important role is played by the level of development of individual countries or regional specifics since the effect of demographics between developed and developing countries is considerably different.

Despite the phenomena of fracture and fatigue having been the focus of academic research for more than 150 years, it remains in effect an empirical science lacking a complete and comprehensive set of predictive solutions. In this regard, the focus of the research in this thesis is on the development of new cohesive-zone models for fracture and fatigue that are afforded an ability to capture strain-rate effects. For the case of monotonic fracture in ductile material, different combinations of material response are examined with rate effects appearing either in the bulk material or localised to the cohesive-zone or in both. The development of a new rate-dependent CZM required first an analysis of two existing methods for incorporating rate dependency, i.e.either via a temporal critical stress or a temporal critical separation. The analysis revealed unrealistic crack behaviour at high loading rates. The new rate-dependent cohesive model introduced in the thesis couples the temporal responses of critical stress and critical separation and is shown to provide a stable and realistic solution to dynamic fracture. For the case of fatigue, a new frequency-dependent cohesive-zone model (FDCZM) has been developed for the simulation of both high and low-cycle fatigue-crack growth in elasto-plastic material. The developed model provides an alternative approach that delivers the accuracy of the loading-unloading hysteresis damage model along with the computational efficiency of the equally well-established envelope load-damage model by incorporating a fast-track feature. With the fast-track procedure, a particular damage state for one loading cycle is 'frozen in' over a predefined number of cycles. Stress and strain states are subsequently updated followed by an update on the damage state in the representative loading cycle which again is 'frozen in' and applied over the same number of cycles. The process is repeated up to failure. The technique is shown to be highly efficient in terms of time and cost and is particularly effective when a large number of frozen cycles can be applied without significant loss of accuracy. To demonstrate the practical worth of the approach, the effect that the frequency has on fatigue crack growth in austenitic stainless-steel 304 is analysed. It is found that the crack growth rate (da/dN) decreases with increasing frequency up to a frequency of 5 Hz after which it levels off. The behaviour, which can be linked to martensitic phase transformation, is shown to be accurately captured by the new FDCZM.

Ce travail concerne l'analyse de la vulnérabilité des structures de protection et des ouvrages sensibles en béton soumis à des actions dynamiques sévères (impacts, explosions) dues à des risques anthropiques d'origine accidentelle ou non. L'objet est la mise au point d'outils prévisionnels de simulation capables de décrire de manière objective le comportement dynamique du béton. Pour cela, une approche numérique novatrice reposant sur la méthode des Eléments Discrets (MED) est développée. Une première partie de cette thèse concerne la simulation des essais quasi-statiques de compression et traction uniaxiales. Une loi de transfert de moment (LTM) a été introduite pour pallier au problème de fragilité en compression simple. Ensuite, la procédure d'identification des paramètres du modèle modifié a été optimisée pour bien reproduire le comportement macroscopique du béton. Enfin, le modèle a été validé en représentant correctement le comportement quasi-statique de plusieurs types de béton. La deuxième partie du travail traite la simulation des essais de traction dynamique du béton aux barres de Hopkinson. Les résultats ont montré la nécessité de prendre l'effet de vitesse de déformation dû au matériau pour bien reproduire le comportement expérimental. Ensuite, Les paramètres du modèle permettant de reproduire cet effet de vitesse ont été identifiés. Enfin, des essais avec des taux de déformation très élevés ont été simulés et les résultats numériques ont été en accord avec le comportement observé expérimentalement. / This work concerns the analysis of the vulnerability of sensitive concrete structures subjected to severe dynamic actions such as impacts due to natural hazards or human factors. The object is to develop a numerical tool that can describe objectively the dynamic behaviour of concrete. Then, a 3D discrete element method (DEM) was developed and used to perform the analysis. The first part of this thesis focuses on the simulation of quasi-static uniaxial compression and traction tests. A moment transfer law (MTL) was introduced to overcome the problem of brittle compressive behavior. Then, the identification procedure of the modified DEM model has been optimized in order to reproduce very well the macroscopic behaviour of concrete. Finally, the model has been validated by representing properly the real quasi-static behavior of different types of concrete. The second part of the study deals with the simulation of the dynamic Hopkinson traction bar tests of concrete. The results showed that a local rate effect has to be introduced to reproduce the strain rate dependency, which would then be a material-intrinsic effect. Then, the parameters of the model have been identified. Finally, simulations were run at high strain rates and showed consistent results with respect to experimental behaviour.

Ce travail concerne l'analyse de la vulnérabilité des structures de protection et des ouvrages sensibles en béton soumis à des actions dynamiques sévères (impacts, explosions) dues à des risques anthropiques d'origine accidentelle ou non. L'objet est la mise au point d'outils prévisionnels de simulation capables de décrire de manière objective le comportement dynamique du béton. Pour cela, une approche numérique novatrice reposant sur la méthode des Eléments Discrets (MED) est développée. Une première partie de cette thèse concerne la simulation des essais quasi-statiques de compression et traction uniaxiales. Une loi de transfert de moment (LTM) a été introduite pour pallier au problème de fragilité en compression simple. Ensuite, la procédure d'identification des paramètres du modèle modifié a été optimisée pour bien reproduire le comportement macroscopique du béton. Enfin, le modèle a été validé en représentant correctement le comportement quasi-statique de plusieurs types de béton. La deuxième partie du travail traite la simulation des essais de traction dynamique du béton aux barres de Hopkinson. Les résultats ont montré la nécessité de prendre l'effet de vitesse de déformation dû au matériau pour bien reproduire le comportement expérimental. Ensuite, Les paramètres du modèle permettant de reproduire cet effet de vitesse ont été identifiés. Enfin, des essais avec des taux de déformation très élevés ont été simulés et les résultats numériques ont été en accord avec le comportement observé expérimentalement. / This work concerns the analysis of the vulnerability of sensitive concrete structures subjected to severe dynamic actions such as impacts due to natural hazards or human factors. The object is to develop a numerical tool that can describe objectively the dynamic behaviour of concrete. Then, a 3D discrete element method (DEM) was developed and used to perform the analysis. The first part of this thesis focuses on the simulation of quasi-static uniaxial compression and traction tests. A moment transfer law (MTL) was introduced to overcome the problem of brittle compressive behavior. Then, the identification procedure of the modified DEM model has been optimized in order to reproduce very well the macroscopic behaviour of concrete. Finally, the model has been validated by representing properly the real quasi-static behavior of different types of concrete. The second part of the study deals with the simulation of the dynamic Hopkinson traction bar tests of concrete. The results showed that a local rate effect has to be introduced to reproduce the strain rate dependency, which would then be a material-intrinsic effect. Then, the parameters of the model have been identified. Finally, simulations were run at high strain rates and showed consistent results with respect to experimental behaviour.

Blades used on brushcutters and lawn mowers are subjected to a wide variety of working conditions. Besides continuous loads from cutting grass, the blades are also subjected to accidental impacts of branches, stones and structures. Due to exceptionally high rotational velocities, these types of impacts involve blade deformation at high strain rates. This master’s thesis aims to improve understanding and predictability of blade properties for design of future blades. The project is aimed at characterization of the mechanical response of steel used for brushcutter blades and developing a simulation model of a blade impact load case. Thus, the problem was divided into two main parts: firstly, material characterization, and secondly, numerical modeling. The objective of the material characterization part was to determine the rate dependence of the flow stress for two hardened steels. Experimental compression tests were performed at quasi-static strain rates (10-4 - 10-2 s-1) and at high strain rates (102 - 104 s-1) in order to characterize the rate dependence of each material. The objective of the numerical modeling part was to develop simulation models of an impact load case for the purpose of recreating tests performed with an experimental test setup. The simulation models were aimed to include material models for the blade based on the experimental tests performed for the two hardened steels. In preparation for the compression tests, cylindrical specimens were acquired through electrical discharge machining involving material removal from blades intended for brushcutters. Compression tests at high strain rates were performed utilizing a split-Hopkinson pressure bar apparatus which resulted in strain rates in the order of 1000 s-1 and 3000 s-1. Compression tests at quasi-static strain rates were performed with an electro-mechanical loading machine and implementation of two-dimensional digital image correlation for strain measurements. With this method, strain rates in the order of 5 · 10-2 s-1 and 5 · 10-4 s-1 were achieved. The acquired results from the experimental tests included the response of the two materials at four different strain rates in the form of true stress-true strain curves. The results were indicative of small strain rate dependency for each of the two hardened steels with a slight increase in yield stress for increasing strain rates. Both materials exhibited closely similar characteristics. At quasi-static rates, the response of both materials exhibited work-hardening of closely similar characteristics. At high strain rates, the response of both materials exhibited a close to identical decrease in stress for values of strain exceeding 10 %. This behavior was suggested to be a consequence of adiabatic heating. At all four achieved strain rates, the results were indicative of a higher yield stress with higher subsequent stresses for one of the hardened steels in comparison to the other. The impact load case aimed to be simulated involved one swing of a brushcutter against a 25 mm diameter steel rod according to standard SS-EN ISO 11806-1:2011. The steel rod was specified to be impacted horizontally by the blade at an approaching translational velocity of 1 m/s and a blade rotational velocity of 8500 rpm. The multi-physics simulation software LS-DYNA was used to develop simulation models which consisted of two main parts, the blade and the rod and included two different blade geometries. As a result of a study regarding the suitability of different discretization techniques, the decision was made to implement the mesh-free particle method Smoothed Particle Galerkin (SPG) and to perform coupling with the finite element method (FEM). Two material models were developed based on the measured stress-strain response obtained through high strain rate compression testing. Several numerical models of the impact load case were produced, all of which entailed different sets of parameters. These included selection of blade material, failure strain, rod length and blade angle relative to the horizontal plane. Finally, two models were developed which were opposite in terms of assigned element formulation for the blade tip and the rod and otherwise identical. The results of the different models were then compared, namely in terms of resulting material failure of the blade after impact. It was concluded that SPG was the most suitable method of choice for the impact load case aimed to be simulated due to its ability to handle large deformation and the inclusion of the a bond-based failure mechanism. Furthermore, implementation of the SPG method resulted in deformation and failure considered to be of greater agreement to experimental test results compared to FEM.

The brain is a complex organ and its response to the mechanical loads at all strain rates has been nonlinear and inelastic in nature. Split-Hopkinson Pressure Bar (SHPB) high strain rate compressive tests conducted on porcine brain samples showed a strain rate dependent inelastic mechanical behavior. Finite Element (FE) modeling of the SHPB setup in ABAQUS/Explicit, using a specific constitutive model (MSU TP Ver. 1.1) for the brain, showed non-uniform stress state during tissue deformation. Song et al.’s assertion of using annular samples for negating inertial effects was also tested. FE simulation results showed that the use of cylindrical or annular did not mitigate the initial hardening. Further uniaxial stress state was not maintained is either case. Experimental studies on hydration effects of the porcine brain on its mechanical response revealed two different phenomenological trends. The wet brain (~80% water wt. /wt.) showed strain rate dependency along with two unique mechanical behavior patterns at quasi-static and high strain rates. The dry brain’s (~0% water wt. /wt.) response was akin to the response of metals. The dry brain’s response also observed to be strain rate insensitivity in its elastic modulus and yield stress variations. Uncertainty analysis of the wet brain high strain rate data revealed large uncertainty bands for the sample-to-sample random variations. This large uncertainty in the brain material should be taken into in the FE modeling and design stages. FE simulations of blast loads to the human head showed that Pressure played a dominant role in causing blast-related Traumatic Brain Injury (bTBI). Further, the analysis of shock waves exposed the deleterious effect of the 3-Dimensional geometry of the skull in pinning the location of bTBI. The effects of peak negative Pressure at injury sites have been attributed to bTBI pathologies such as Diffuse Axonal Injury (DAI), subdural hemorrhage and cerebral contusion.

The aims of this thesis are to study the fracture behaviour in unreinforced masonry, to carry out a limited experimental program on three-point bending (TPB) masonry panels and to develop a time-dependent fracture formulation for the study of mode I fracture in quasi-brittle materials. A micro-model for fracture in unreinforced masonry is developed using the concept of the discrete crack approach. All basic masonry failure modes are taken into account. To capture brick diagonal tensile cracking and masonry crushing, a linear compression cap is proposed with a criterion for defining the compression cap. The failure surface for brick and brick-mortar interfaces are modelled using a Mohr-Coulomb failure surface with a tension cut-off and a linear compression cap. The fracture formulation, in nonholonomic rate form within a quasi-prescribed displacement approach, is based on a piecewise-linear constitutive law and is in the form of a so-called ?linear complementarity problem? (LCP). The proposed model has been applied to simulating fracture in masonry shear walls and masonry TPB panels. An experimental program was undertaken to investigate the failure behaviour of masonry panels under TPB with relatively low strength mortar. The basic material parameters were obtained from compression, TPB and shear tests on bricks, mortar and brick-mortar interfaces. The experimental results showed that the failure of masonry TPB panels is governed by both tensile and shear failure rather than just tensile failure. The simulation of the masonry TPB tests compared well with the experimental results. In addition, the LCP fracture formulation is enhanced to study the time-dependent mode I fracture in quasi-brittle materials. Two main time-dependent sources, the viscoelasticity of the bulk material and the crack rate dependent opening, are taken into account. A simplified crack rate model is proposed to include the rate-dependent crack opening. The model is applied to predicting time-dependent crack growth in plain concrete beams under sustained loading. The model captures the essential features including the observed strength increase with loading rate, the load-deflection and load-CMOD responses, the deflection-time and CMOD-time curves, the predicted time to failure and the stress distributions in the fracture zone.

The aims of this thesis are to study the fracture behaviour in unreinforced masonry, to carry out a limited experimental program on three-point bending (TPB) masonry panels and to develop a time-dependent fracture formulation for the study of mode I fracture in quasi-brittle materials. A micro-model for fracture in unreinforced masonry is developed using the concept of the discrete crack approach. All basic masonry failure modes are taken into account. To capture brick diagonal tensile cracking and masonry crushing, a linear compression cap is proposed with a criterion for defining the compression cap. The failure surface for brick and brick-mortar interfaces are modelled using a Mohr-Coulomb failure surface with a tension cut-off and a linear compression cap. The fracture formulation, in nonholonomic rate form within a quasi-prescribed displacement approach, is based on a piecewise-linear constitutive law and is in the form of a so-called ?linear complementarity problem? (LCP). The proposed model has been applied to simulating fracture in masonry shear walls and masonry TPB panels. An experimental program was undertaken to investigate the failure behaviour of masonry panels under TPB with relatively low strength mortar. The basic material parameters were obtained from compression, TPB and shear tests on bricks, mortar and brick-mortar interfaces. The experimental results showed that the failure of masonry TPB panels is governed by both tensile and shear failure rather than just tensile failure. The simulation of the masonry TPB tests compared well with the experimental results. In addition, the LCP fracture formulation is enhanced to study the time-dependent mode I fracture in quasi-brittle materials. Two main time-dependent sources, the viscoelasticity of the bulk material and the crack rate dependent opening, are taken into account. A simplified crack rate model is proposed to include the rate-dependent crack opening. The model is applied to predicting time-dependent crack growth in plain concrete beams under sustained loading. The model captures the essential features including the observed strength increase with loading rate, the load-deflection and load-CMOD responses, the deflection-time and CMOD-time curves, the predicted time to failure and the stress distributions in the fracture zone.

The cutting of foods is characterized by deformation, fracture and friction processes, and the viscoelastic properties of the cutting materials determine their rate-dependent cutting behavior. This is responsible for uncontrolled fracture and deformation events with increasing cutting velocity. There is a significant information deficit regarding the assignment of material properties and cutting parameters, as well as regarding a process description for industrial high-speed cutting. The aim of the work is the analysis of the velocity-dependent cutting behavior of foods up to the high-speed range. The focus is on the deformation and fracture phenomena, analysed by methods of classical material analysis but also associated cutting experiments performed in the range from low to high cutting velocities. For high-speed analyses, a test station enabling cutting velocities of up to 10 m/s was designed. To identify relevant material and cutting parameters and to establish a systematic experimental program, elastomer-based model systems with controllable viscoelastic profiles were developed. The results of the respective investigations were further verified for foods. The velocity-dependent deformation behavior during cutting could be described by dynamic-mechanical material analyses in the frequency range. Cutting force slopes at the beginning of the cutting process correlated with the complex moduli and were furthermore dependent on the cutting velocity; this dependency corresponded to the frequency behavior from material analysis. The fracture properties could be attributed to ductile (polymeric systems) or brittle behavior (cellular plant systems). Confectionary products had a strong temperature- and time-dependent behavior with ductile-brittle transition within the experimental conditions. The results obtained demonstrate that there is a significant relationship between viscoelasticity and velocity-dependent cutting behavior. They allow a phenomenological process description of high-speed cutting and can be used as a basis for the balancing of cutting forces and as input parameters for numerical analyses of the cutting process. / Das Schneiden von Lebensmitteln ist geprägt durch Deformations-, Bruch- und Reibvorgänge. Dabei bestimmen die viskoelastischen Eigenschaften der Schneidgüter deren geschwindigkeitsabhängiges Schneidverhalten. Dies führt mit zunehmender Schneidgeschwindigkeit zu unkontrollierten Bruch- und Deformationsereignissen. Dabei besteht ein Informationsdefizit bei der konkreten Zuweisung von Materialeigenschaften und Schneidparametern sowie einer Verfahrensbeschreibung für das industrielle Hochgeschwindigkeitsschneiden. Ziel der Arbeit ist die Analyse des geschwindigkeitsabhängigen Schneidverhaltens von Lebensmitteln bis in den Hochgeschwindigkeitsbereich. Der Fokus richtet sich auf die Untersuchung der Teilphänomene Deformation und Bruch durch Methoden der klassischen Materialanalyse sowie zugeordnete Schneidexperimente im Bereich von niedrigen bis hohen Schneidgeschwindigkeiten. Für entsprechende Hochgeschwindigkeitsanalysen wurde ein Versuchsstand mit Schneidgeschwindigkeiten von bis zu 10 m/s konzipiert. Zur Identifikation relevanter Material- und Schneidparameter und zur Aufstellung des systematischen Versuchsprogramms wurden Modellsysteme auf Elastomerbasis mit steuerbarem viskoelastischen Profil entwickelt. Die Ergebnisse wurden für Lebensmittel verifiziert. Das geschwindigkeitsabhängige Deformationsverhalten beim Schneiden konnte durch dynamisch-mechanische Materialanalysen im Frequenzbereich beschrieben werden. Dabei korrelierten Kraftanstiege zu Beginn des Schneidvorganges mit den Komplexmoduln. Die Anstiege zeigten eine Abhängigkeit von der Geschwindigkeit; diese entsprach dem Frequenzverhalten aus der Materialanalyse. Die Brucheigenschaften konnten produktspezifisch duktilem (polymere Systeme) oder sprödem Verhalten (zelluläre, pflanzliche Systeme) zugeordnet werden. Zuckerwaren zeigten ein stark temperatur - und zeitabhängiges Verhalten mit duktil-sprödem Übergang innerhalb der Versuchsbedingungen. Die gewonnenen Erkenntnisse demonstrieren den Zusammenhang von Viskoelastizität und geschwindigkeitsabhängigem Schneidverhalten. Sie erlauben eine phänomen ologische Verfahrensbeschreibung des Hochgeschwindigkeitsschneidens und können als Basis für die Bilanzierung von Schneidkräften und als Eingangsparameter für numerische Analysen des Schneidvorganges dienen.