Above true strain rates of $10^4$ s$^{-1}$ FCC metals exhibit a rapid increase in strength. Understanding of the physical mechanisms behind this strength transition is hindered by the number and interdependence of candidate mechanisms. Broadly, contributions to strength can be split into `instantaneous' effects and the more permanent `structural' ones. In this thesis a series of experiments are presented which are designed to separate the two types of contribution. Chapter 2 outlines the basics of dislocation plasticity, based on the seminal works of Taylor and Orowan. It then progresses on to discuss recent experimental and theoretical work on the understanding of slip as avalanche behaviour. Chapter 3 summarises traditional modelling approaches for instantaneous strength contributions which are routinely applied below $10^4$ s$^{-1}$. It then continues on to outline a number of different approaches which have been adopted to attempt to explain and model the strength transition. Chapter 4 outlines the methods used in the earliest stages of the study: Instron and split Hopkinson pressure bar methods. Both methods are well established, and cover the majority of the range of rates under study. Emphasis is made on minimising experimental sources of error, and subsequently accounting for those which are unavoidable. Finally, the specimen material is introduced and is shown to be fit for purpose. Chapter 5 presents a set of mechanical tests of specimens at strain rates between $10^4-10^5$~s$^{-1}$. The softening of the specimens with increased temperature is observed to increase with strain rate, both in absolute terms and when normalised to the 300 K measurement for each strain rate. The observations are most easily explained if the strength transition is due to an increase in early stage work hardening, however, some anomalous behaviours remain. Chapter 6 introduces a new experimental technique; direct impact Hopkinson pressure bars, required to perform experiments shown to be necessary by the results of Chapter 5. Photon Doppler velocimetry is applied to the projectiles used in experiments, removing one of the most significant flaws of the technique, and creating a more confident basis with which to perform further experimental work. Chapter 7 presents a series of `jump tests' at ambient temperatures. Specimens are deformed at strain rates ranging from $10^{-2}$ to $10^5$~s$^{-1}$ to a fixed strain of 0.1, then reloaded to yield at a strain rate of $10^{-1}$. The yield point at reload is shown to have the same rapid upturn as seen when the specimens were deforming at high rates, providing strong evidence that the increase in strength is due to changes in the underlying dislocation structure, rather than a dynamic effect, as it remains even when the high strain rate is removed. Chapter 8 continues on from the conclusions of Chapter 7. Jump tests are expanded to a variety of temperatures and strains, to provide a more complete characterisation of metal behaviour. No dramatic change in the saturation of work hardening is observed to coincide with the increase in early stage work hardening. Chapter 9 discusses discrepancies between contemporary high rate models and recent developments in the understanding of plasticity being an avalanche process. Potential consequences of incorporating avalanche plasticity into high rate models are explored. Particular attention is paid to Brown's observation that based on quasi static observations of avalanche behaviour, the formation of dislocation avalanches will begin to fail at strain rates of approximately $10^4$ s$^{-1}$. Consequences of the progressive breakdown of avalanche behaviour are discussed with respect to the experimental observations presented in earlier chapters. In Chapter 10, we will discuss the key conclusions of the work. Finally, a number of avenues are proposed for building upon the current work both theoretically and experimentally.

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.

A hydrocode and an explicit finite element code were used to evaluate functionally graded material impacts, meteor impacts, and split Hopkinson pressure bar specimens. Modeling impacts of functionally graded projectiles revealed that density was the primary material characteristic controlling the shock wave profile. A parametric study of material order for functionally graded armor showed that arranging the weaker material in front created the greater stopping power. By modeling an array of meteor impact scenarios, deformation and stress were shown to occur at great depths and possibly cause tectonic movement, like subduction. Three proposed Hopkinson specimens, which were designed to produce either shear or tensile reactions under compressive loading, were evaluated. For two of these specimens, improved stress and strain equations were presented.

O presente trabalho trata sobre a influência do teor de enxofre, em quatro aços com uma composição química similar (famílias ABNT 1045 e ABNT 1145), na microestrutura, nas propriedades estáticas, dinâmicas e nos processos de usinagem. Para esta análise foi feita uma caracterização microestrutural de cada material para determinar parâmetros tais como a fração de inclusões de sulfeto de manganês (MnS) e a fração volumétrica de perlita. Também foi feita uma caracterização mecânica que consistiu em ensaios estáticos mediante o ensaio de tração e dureza, e um ensaio dinâmico utilizando a barra de Hopkinson, com o objetivo de observar o comportamento das inclusões e do próprio material quando deformado com altas e baixas taxas de deformação. Para a caracterização durante a usinagem destes aços foram feitos ensaios de torneamento para avaliar as forças de corte e de avanço em velocidades de corte de 190, 110, 45 e 15 m/min. A rugosidade dos corpos-de-prova também foi medida. Os resultados obtidos nos ensaios de torneamento e da caracterização microestrutural foram analisados estatisticamente para observar variações do comportamento das forças de usinagem de cada aço sob diferentes condições de velocidade de corte, e tentar correlacionar esse comportamento com a microestrutura do material. Observou-se que o aço 1045-A apresentou forças de usinagem (força de corte e força de avanço) superiores que os demais aços, já o aço que apresentou menores forças de usinagem foi o aço 1145-B. Isto é apenas uma tendência, devido que não houve diferença estatística que avaliasse esse comportamento. Também se observou que a rugosidade é um parâmetro que depende mais da velocidade de corte que da distribuição e/ou morfologia das inclusões. Evidenciou-se a formação de aresta postiça de corte (APC) numa faixa de velocidades (15-50 m/min), o que influenciou na rugosidade para estas condições de velocidades. Verificou-se que o comportamento das inclusões em baixas taxas de deformação é de caráter frágil, entanto que em altas taxas seu comportamento é plástico e deforma junto com a matriz. / This work deals with the sulfur influence on the microstructure and on the static, dynamic and machining behavior of four steels with similar chemical composition. (ABNT 1045 and ABNT 1145). Microstructure characterization of the materials was performed in order to obtain the area fraction of the phases of perlite and sulfide inclusions. A mechanical characterization of the materials was also performed, consisting in a set of static (tension and hardness test) and dynamic tests (Split Hopkinson Pressure Bar Test) with the objective of observing the deformation behavior of the sulfide inclusions at low and high strain rates. Various machining tests were carried out at different cutting speeds, namely 190, 110, 45 e 15 m min-1, for obtaining the cutting forces during de machining process. After the machining tests, the roughness of the steels was also measured. Later on, the results of the different experiments were analyzed with statistical tools and then compared to establish a correlation between the cutting forces and microstructure. The higher cutting forces were registered for the 1045-A steel and the lower for the 1145-B steel. However, this was considered merely a trend given that no statistical difference was found to support any conclusion. It was also observed a stronger roughness dependency on the cutting speed than in the distribution and/or morphology of the inclusions. The steels were observed to form a built-up edge (BUE) in a range of cutting velocities of 15-50 m/min. This phenomenon affected the roughness for these cutting velocities. The behavior of the sulfide inclusions was observed to be brittle under low strain rates. On the other hand, under high strain rates, a plastic deformation behavior was observed with inclusions participating in the plastic flow of the metal matrix.

O presente trabalho trata sobre a influência do teor de enxofre, em quatro aços com uma composição química similar (famílias ABNT 1045 e ABNT 1145), na microestrutura, nas propriedades estáticas, dinâmicas e nos processos de usinagem. Para esta análise foi feita uma caracterização microestrutural de cada material para determinar parâmetros tais como a fração de inclusões de sulfeto de manganês (MnS) e a fração volumétrica de perlita. Também foi feita uma caracterização mecânica que consistiu em ensaios estáticos mediante o ensaio de tração e dureza, e um ensaio dinâmico utilizando a barra de Hopkinson, com o objetivo de observar o comportamento das inclusões e do próprio material quando deformado com altas e baixas taxas de deformação. Para a caracterização durante a usinagem destes aços foram feitos ensaios de torneamento para avaliar as forças de corte e de avanço em velocidades de corte de 190, 110, 45 e 15 m/min. A rugosidade dos corpos-de-prova também foi medida. Os resultados obtidos nos ensaios de torneamento e da caracterização microestrutural foram analisados estatisticamente para observar variações do comportamento das forças de usinagem de cada aço sob diferentes condições de velocidade de corte, e tentar correlacionar esse comportamento com a microestrutura do material. Observou-se que o aço 1045-A apresentou forças de usinagem (força de corte e força de avanço) superiores que os demais aços, já o aço que apresentou menores forças de usinagem foi o aço 1145-B. Isto é apenas uma tendência, devido que não houve diferença estatística que avaliasse esse comportamento. Também se observou que a rugosidade é um parâmetro que depende mais da velocidade de corte que da distribuição e/ou morfologia das inclusões. Evidenciou-se a formação de aresta postiça de corte (APC) numa faixa de velocidades (15-50 m/min), o que influenciou na rugosidade para estas condições de velocidades. Verificou-se que o comportamento das inclusões em baixas taxas de deformação é de caráter frágil, entanto que em altas taxas seu comportamento é plástico e deforma junto com a matriz. / This work deals with the sulfur influence on the microstructure and on the static, dynamic and machining behavior of four steels with similar chemical composition. (ABNT 1045 and ABNT 1145). Microstructure characterization of the materials was performed in order to obtain the area fraction of the phases of perlite and sulfide inclusions. A mechanical characterization of the materials was also performed, consisting in a set of static (tension and hardness test) and dynamic tests (Split Hopkinson Pressure Bar Test) with the objective of observing the deformation behavior of the sulfide inclusions at low and high strain rates. Various machining tests were carried out at different cutting speeds, namely 190, 110, 45 e 15 m min-1, for obtaining the cutting forces during de machining process. After the machining tests, the roughness of the steels was also measured. Later on, the results of the different experiments were analyzed with statistical tools and then compared to establish a correlation between the cutting forces and microstructure. The higher cutting forces were registered for the 1045-A steel and the lower for the 1145-B steel. However, this was considered merely a trend given that no statistical difference was found to support any conclusion. It was also observed a stronger roughness dependency on the cutting speed than in the distribution and/or morphology of the inclusions. The steels were observed to form a built-up edge (BUE) in a range of cutting velocities of 15-50 m/min. This phenomenon affected the roughness for these cutting velocities. The behavior of the sulfide inclusions was observed to be brittle under low strain rates. On the other hand, under high strain rates, a plastic deformation behavior was observed with inclusions participating in the plastic flow of the metal matrix.

Η σφυρηλάτηση με βολή σωματιδίων (shot peening) είναι μία επιφανειακή κατεργασία που πραγματοποιείται με σκοπό την αύξηση της αντοχής μεταλλικών υλικών και εφαρμόζεται στο τελευταίο στάδιο της γραμμής παραγωγής. Η αύξηση της αντοχής επιτυγχάνεται με την ανάπτυξη θλιπτικών παραμενουσών τάσεων κοντά στην επιφάνεια του υλικού έπειτα από την κρούση σωματιδίων με υψηλές ταχύτητες. Η ανάπτυξη θλιπτικών παραμενουσών τάσεων αυξάνει την αντοχή σε κόπωση, σε εργοδιάβρωση, καθώς και σε άλλες μηχανικές καταπονήσεις και επιτρέπει την μείωση του βάρους σχεδιάζοντας διατομές με μικρότερο πάχος. Στην παρούσα Διδακτορική Διατριβή παρουσιάζεται μια ολοκληρωμένη αριθμητική προσομοίωση της κατεργασίας και εξετάζεται η μηχανική συμπεριφορά των υπό κατεργασία υλικών σε υψηλούς ρυθμούς καταπόνησης. Συγκεκριμένα η μεθοδολογία που αναπτύσσεται περιλαμβάνει την ανάπτυξη ενός αριθμητικού προτύπου για την προσομοίωση της κατεργασίας της σφυρηλάτησης με βολή σωματιδίων και τον υπολογισμό των αποτελεσμάτων της στο υλικό. Τα βήματα που ακολουθηθήκαν για την ανάπτυξη του αριθμητικού προτύπου είναι, α) ο χαρακτηρισμός του κράματος αλουμινίου 7449-Τ7651 σε υψηλούς ρυθμούς καταπόνησης μέσω της πειραματικής διάταξης Split Hopkinson Bar που σχεδιάστηκε και κατασκευάστηκε στο Εργαστήριο Τεχνολογίας και Αντοχής Υλικών, β) η ανάπτυξη βοηθητικών επιμέρους αριθμητικών μοντέλων, γ) η ανάπτυξη κινηματικών μοντέλων προσομοίωσης της ροής των σωματιδίων, δ) η ανάπτυξη κριτηρίων και η εφαρμογή τους για τον υπολογισμό του ελαχίστου απαιτούμενου αριθμού σωματιδίων για την προσομοίωση, καθώς και των θέσεων κρούσης, ε) η ανάπτυξη ενός αριθμητικού προτύπου πλήρους γεωμετρίας της πλάκας για την κρούση του απαιτούμενου αριθμού σωματιδίων και στ) η πειραματική επαλήθευση του αριθμητικού προτύπου. Με το αριθμητικό πρότυπο που αναπτύχτηκε υπολογίστηκαν τα αποτελέσματα της κατεργασίας της σφυρηλάτησης με βολή σωματιδίων στο υλικό και επιβεβαιώθηκαν μέσω συγκρίσεων με αντίστοιχα πειραματικά αποτελέσματα. Αποτελέσματα της κατεργασίας εκτός από τις παραμένουσες τάσεις αποτελούν και η πλαστική παραμόρφωση, η σκληρότητα, η επιφανειακή τραχύτητα και κατ' επέκταση ο συντελεστής έντασης τάσης. Στη συνέχεια, πραγματοποιήθηκε μια παραμετρική μελέτη για την επίδραση της διαμέτρου, της ταχύτητας και της γωνίας κρούσης στην ανάπτυξη των παραμενουσών τάσεων. Επίσης το αριθμητικό πρότυπο επαληθεύτηκε και για άλλα μεταλλικά υλικά. / Shot peening is a surface treatment process that is performed to increase the strength of metallic materials and is applied to the last stage of the production line (post manufacturing process). The increase in strength is achieved by the developed compressive residual stresses near the surface and the subsurface of the treated material after the impact of small diameter particles with high speeds. The developed compressive residual stresses increases the fatigue strength, the mechanical performance of the component under stress corrosion cracking (SCC), under higher stresses and allows lighter structure design. This PhD thesis presents a comprehensive numerical simulation of the Shot peening process and includes a comprehensive study of the mechanical behaviour of treated materials under high strain rates of deformation. Specifically, the methodology developed includes the development of a comprehensive numerical model to simulate Shot peening treatment and calculate the results on the treated material. The steps followed for the development of the numerical model are: a) the characterization of the Aluminium alloy 7449-T7651 at high strain rates using a Split Hopkinson Bar apparatus designed and built at the Laboratory of Technology and Strength of Materials, b) the development of auxiliary partial numerical models, c) the development of a kinematic simulation model for the analysis of the flow particles, d) the development and the application of two criteria for the successful calculation of the minimum number of particles that required for the simulation, and the impact positions e) the development of a numerical model describing the full plate geometry for the impact of the minimum number of particles required and f) the experimental verification of the numerical model. The process outcomes and results on the treated material were calculated by the numerical model developed. The numerical results that were calculated for the threaded material were confirmed by comparison with experimental results. Treatment results include the residual stresses, the plastic deformation, hardness, surface roughness, and hence the stress concentration factor. A parametric study on the effect of the diameter, speed and angle of impact to the development of residual stresses was performed. The numerical model was also verified for a number of other metallic materials.

Lors de la phase de certification d’un turbomoteur, le motoriste doit démontrer que la perte d’une pale de rotor ne conduit pas au "Knocking-Off", c’est à dire à la rupture en cascade des pales suiveuses. Cette démonstration est faite en général par un essai au banc coûteux car partiellement destructif. Grâce à l’amélioration des moyens de calcul, il devient possible de simuler la réponse transitoire de la structure soumise à ce type de chargement très complexe. En tant que point d’entrée sur la simulation, la connaissance du comportement des matériaux est primordiale. Or, peu d’études sont publiées sur le comportement dynamique des superalliages à base nickel monocristallins et, de surcroît, à des températures élevées de l’ordre de 1000°C. Pour prédire efficacement les conséquences d’impacts sur des pales de turbines, des travaux expérimentaux et numériques ont été réalisés sur un monocristal couramment utilisé par Turbomeca. Des essais de compression dynamique à haute température sur barres de Hopkinson permettent d’estimer le seuil de plasticité et l’écrouissage du matériau en fonction de l’orientation du cristal, de la vitesse de déformation et de la température. Les paramètres d’une loi visco-plastique anisotrope sont identifiés pour modéliser efficacement le comportement macroscopique du MC2 sous des chargements intenses et fortement multi-axiaux. Une campagne d’essais balistiques au banc de Safran Snecma a été réalisée sur des plaques et des pales monocristallines à hautes températures. Afin de prendre en compte la fragmentation des profils dans les calculs de perte de pale, un critère en déformation plastique dépendante du taux de triaxialité des contraintes est calibré puis validé par confrontation aux essais de tirs sur plaques. Des mesures de stéréo-corrélation postmortem et des enregistrements à la caméra rapide permettent de valider les simulations. Une pratique de modélisation de la perte d’une pale avec l’outil LS-Dyna a été établie et appliquée à un cas industriel de perte de pale en service. Enfin, en vue de justifier le découplage temporel entre les dommages primaires, liés aux impacts directs sur les premières pales suiveuses, et secondaires, liés aux effets de l’excentration, une approche de dynamique d’ensemble de ligne d’arbre a été développée puis validée. / During the certification process of a turbo engine, the engine manufacturer has to demonstrate that the loss of a rotor blade does not lead to the "knocking-off" phenomenon, in other words to the cascading failure of the successive blades. Generally, this demonstration is carried out through a costly rig test driving to the partial destruction of the engine. Thanks to the improvement of computational resources, it is now possible to simulate the transient response of the structure subjected to this complex loading. The knowledge of material behavior turns out to be the essential starting point for the simulation. However, only a few studies have been published on the dynamic behavior of nickel-based single crystal superalloys at high temperature reaching 1000°C. With a view to efficiently predicting the consequences of impacts on turbine blades, experimental and numerical works have been conducted on a single crystal frequently used by Turbomeca. High-temperature dynamic compressive tests on Split Hopkinson Pressure Bars (SHPB) have enabled to estimate the material plasticity level and hardening, depending on the crystal orientation, strain rate and temperature. The parameters of a viscoplastic anisotropic law have been identified to effectively model the MC2 macroscopic behavior under highly intense and multiaxial loading. At Safran Snecma Villaroche, ballistic tests have been undertaken on both single crystal plates and blades under high temperatures. In order to consider the fragmentation of profiles in blade-off simulations, a plastic strain criterion depending on stress triaxiality has been calibrated and validated by comparison with the impacts on blades. Post-mortem digital images correlation measurements and high-speed camera recordings have confirmed these simulations. Using LS-Dyna solver, a blade-off modeling strategy has been created and applied to an actual blade-off industrial case. Finally, a rotordynamics approach has been developed and validated with the aim of separately analyzing the primary damage, caused by direct impacts on the first following blades, and the secondary damage due to the effects of unbalance on a flexible rotor.

The PhD thesis deals with the influence of temperature and strain rate on the mechanical behaviour of the Ti-6Al-4V titanium alloy. After verification tests under static loading conditions, the samples were deformed at high strain rates and elevated temperatures, using device for Hopkinson pressure bar test. The result is dependence of stress and strain rate on strain in the temperature range of 20 to 500°C. The deformed shape of specimen from the Taylor anvil test is compared with the results of the simulation in the Ansys – LS Dyna software. The parameters of Johnson-Cook equation were determined from these experiments. Also, the influence of loading conditions on the microstructure was studied. Both optical and scanning electron microscopes were used for the observations. During the research, some adjustments to the experimental devices were made in order to suppress the high-frequency components and noise in the recorded pulses. A functional tensile test adapter for the Hopkinson test was developed; it is registered under No. 2007/008 at the Technology Transfer Office of BUT.

Dynamic testing provides valuable insight into the behavior of materials undergoing fast deformation. During Split-Hopkinson Pressure Bar testing, stress waves are measured using strain gauges as voltage variations that are usually very small. Therefore, an amplifier is required to amplify the data and analyze it. One of the few available amplifiers designed for this purpose is provided by Vishay Micro-Measurements which limits the user’s options when it comes to research or industry. Among the challenges of implementing the Hopkinson technology in the industry are the size and cost of the amplifier. In this work, we propose a novel design of a signal conditioning amplifier that provides the following functionalities: voltage excitation for strain gauges, wide gain range (1-1000), signal balancing, shunting, and filtering. The main objective is to make a smaller and cheaper amplifier that provides equivalent or better performance allowing larger application of the Hopkinson technology in the industry.