L'élastographie par résonance magnétique (ERM) est une technique d'imagerie, reconnue comme une méthode pertinente pour la caractérisation mécanique des tissus humains in vivo. Celle-ci représente un intérêt fondamental en diagnostic clinique car le développement d'un processus pathologique s'accompagne la plupart du temps d'altérations des propriétés mécaniques des tissus atteints. L'ERM consiste à enregistrer le champ de déplacement induit au passage d'une onde de cisaillement généré dans le milieu étudié. Les paramètres mécaniques comme la vitesse, v, et les modules de viscoélasticité de cisaillement, G' et G'', peuvent être cartographiés. La quantification des paramètres mécaniques dépend à la fois de la fréquence mécanique, fexc, de la taille de voxel, a, de l'amplitude des champs de déplacement induits, A, de l'amplitude du rotationnel du champ de déplacement, q, des erreurs de mesure, ΔA et Δq, donc du rapport signal à bruit, RSB, et enfin de la méthode de reconstruction. En inversant les équations différentielles du champ de déplacement acquis selon les trois dimensions de l'espace, ces paramètres ont été considérés pour déterminer la précision et l'exactitude des modules mécaniques obtenus et établir les conditions de validité de l'ERM. Dans cette thèse, nous avons tout d'abord considéré A et A/ΔA afin de définir un premier seuil de validité pour l'ERM. Nous avons étudié l'influence de ces deux paramètres sur un fantôme hétérogène dans un appareil IRM 1,5 T avec deux types d'antennes. Dans une première étude, les champs de déplacement ont été acquis en fonction de A en utilisant deux séquences écho de spin (RFE) et écho de gradient (FFE) sensibilisées au mouvement pour une taille de voxel isotrope de 1 mm. Dans une seconde étude, ils ont été acquis en RFE en fonction de A pour trois résolutions spatiales différentes. Ces études ont révélé l'existence d'un seuil en A/ΔA au-delà duquel les paramètres extraits (G', G'') atteignent un plateau et l'ERM est fiable. Nous avons ensuite considéré le nombre de voxel par longueur d'onde, λ/a, comme paramètre déterminant des conditions de validité de l'ERM et nous avons caractérisé la qualité des données acquises par le rapport q/Δq. Sur des simulaitons dans un milieu élastique, homogène et isotrope avec un RSB variant entre 5 et 30, la précision et l'exactitude des mesures se sont avérées optimales pour 6 à 9 voxels par longueur d'onde. Nous avons reproduit expérimentalement à 2 kHz les conditions des siimulations sur un fantôme de PVA. Les champs de déplacement ont été acquis à 11,7 T en utilisant une séquence RFE sensibilisée au mouvement pour des résolutions spatiales de 150 μm à 300 μm afin de balayer le rapport λ/a de 1 à 20. Les résultats expérimentaux confirment pleinement les prédictions de la simulation. La vitesse de cisaillement diminue et tend vers la vitesse de référence attendue lorsque l'acquisition est réalisée dans le domaine optimal, à savoir ici lorsque a est inférieure ou égale à 200 μm. En outre la dispersion de la vitesse est réduite dans le domaine optimal et des estimations plus précises des paramètres mécaniques ont pu être déduites. Cette thèse montre d'une part que la précision et l'exactitude de l'ERM sont optimales lorsque les acquisitions sont réalisées ou traitées pour un domaine d'échantillonnage de la longueur d'onde déterminé par le RSB. Elle montre d'autre part que la comparaison des résultats obtenus doit être menée dans une gamme similaire de q/Δq. La prise en compte des conditions de validité de l'ERM, déterminées par les rapports λ/a et q/Δq, conduit à une mesure quantitative effective des paramètres mécaniques. Il est ainsi possible d'envisager un diagnostic clinique pertinent au sein d'un même organe, d'un même sujet, entre sujets ou au cours du temps. / Magnetic Resonance Elastography (MRE) is a imaging technique, recognized as a pertinent method for the mechanical characterization of human tissue in vivo. It offersa particular interest in clinical diagnosis because the development of a pathological process is often accompanied by modifications of the mechanical properties of diseased tissues. MRE consists of recording, along the three spatial dimensions, the displacement field induced by the propagation of a shear wave generated by excitation of the investigated tissue. Mechanical parameters such as shear wave velocity, v, and shear moduli, G' and G'', can then be mapped. The quantification of the mechanical parameters depends on the frequency of the mechanical excitation, fexc, the spatial resolution, a, the amplitude of the induced displacement field, A and the amplitude of the curl field displacement, q, with associated measurement errors, ΔA and Δq, (related to the signal-to-noise ratio, SNR) and finally the reconstruction method. All these parameters were considered to determine the precision and the accuracy of the estimated mechanical moduli and to establish the conditions of validity of MRE following the inversion of the differential equations of the displacement field. In this work, first A and A/ΔA were considered to define a validity threshold for MRE. The influence of A and A/ΔA was studied on a heterogeneous phantom acquired using a 1.5 T MRI with two different types of coils. In a first study, the displacement fields were acquired as a function of A using motion-sensitized spin-echo (REF) and gradient-echo (FFE) sequences for an isotropic spatial resolution of 1 mm. In a second study, the displacement field was acquired as a function of A using RFE for three different spatial resolutions. These studies revealed the existence of a threshold in A/ΔA beyond which the extracted parameters (G', G'') reach a plateau and the MRE is reliable. Then the number of voxels per wavelength, λ/a was considered as a parameter determining the conditions of validity of MRE. This parameter was studied according to the quality of the acquired data characterized by the ratio q//Δq. Simulations were carried in a homogeneous and isotropic elastic medium with a SNR between 5 and 30. The accuracy and the precision of the measurements were found optimal for 6 to 9 voxels per wavelength. The simulation conditions were experimentally reproduced at 2 kHz on a home-made polyvinyl alcohol phantom. The displacement fields were acquired at 11.7 T using a motion-sensitized RFE sequence with spatial resolutions ranging from 150 μm to 300 μm in order to obtain a λ/a ratio ranging from 1 to 20. The experimental results fully confirm the predictions of the simulation. The shear wave velocity decreases with λ/a. It tends towards the expected reference value when the acquisition is performed in the optimal condition, namely here when a is less than or equal to 200 μm. In addition, the standard deviation of the shear wave velocity is reduced for the optimal conditions. Therefore, accurate estimation of mechanical parameters could be deduced. This thesis first demonstrates that the precision and accuracy of MRE are optimal when the acquisitions are performed or processed for a certain wavelength sampling range determined by the SNR. We also showed that for fair comparison of the results, MRE must be carried out in a similar range of q/Δq. Taking into account the conditions of validity of MRE, determined by the ratios λ/a and q/Δq, leads to an effective quantitative measurement of the mechanical parameters making it possible to establish a relevant clinical diagnosis within the same organ, the same subject, between subjects or over time.

The deep mining and civil engineering industry need to perform rock stability analyses during excavation projects. The stability is mainly controlled by the shear strength of the rock fractures, which are the weakest point of the rock mass. In turn, the shear strength is governed by the mechanical properties of the fractures. It is both time and cost demanding to determine the properties of the rock fractures in laboratory. Also, the interpretation of the results requires a deep understanding of the normal and shear behaviour of rock fractures. This study aims to investigate if it is possible to determine the peak shear strength of rock fractures by merely estimating fracture parameters during field mapping and core logging. SKB supplied test results on drilled bore cores from site investigations in Forsmark and Laxemar for deep nuclear waste deposits. SKB generated data of high quality and in large quantity, which made it very valuable for the purpose of the study. The study begins with a literature review and an interaction matrix, clarifying the relationships between mechanical properties and affecting parameters of rock fractures. The predicted relationships of the parameters are then tested in an analysis based on the compiled data from SKB. The results show that the peak friction angle, the residual friction angle and the dilation angle are possible to approximate for open granite fractures in deep mining projects. Further on, the study proposes that the joint matching coefficient is included in the field mapping and core logging since it has a strong influence on the mechanical behaviour of the fracture, notably the normal and shear stiffness. Finally, the study questions estimations of JRC on small samples.

Στο πλαίσιο της παρούσας διπλωματικής εργασίας, αρχικά γίνεται μια σύντομη περιγραφή της γεωλογίας της μελετούμενης περιοχής που εντοπίζεται σε τμήμα της ε.ο Πατρών- Τριπόλεως περί της χ.θ 84 + 000. Αναφέρονται οι γεωλογικές συνθήκες της ευρύτερης περιοχής και η γεωτεκτονική εξέλιξη της γεωτεκτονικής ζώνης Ωλονού- Πίνδου. Η σπουδαιότητα των στοιχείων αυτών έγκειται στην κατανόηση του ευρύτερου τεχνικογεωλογικού περιβάλλοντος που ανήκουν οι ασβεστολιθικοί σχηματισμοί. Ακολουθεί η περιγραφή- αξιολόγηση των εργαστηριακών δοκιμών που εκτελέστηκαν σύμφωνα με τις ισχύουσες προδιαγραφές και περιγράφονται ο τρόπος δειγματοληψίας, η διαμόρφωση δειγμάτων και ο προσδιορισμός των φυσικών και μηχανικών παραμέτρων των ληφθέντων βραχώδων δειγμάτων ασβεστολίθου. / In the context of this thesis, first a brief description of the geology of the studied area is located in a part of the National Road Patras Tripoli on KP 84 + 000. Describe the geological conditions of the region, and the tectonic evolution of the geotectonic zone Olonou - Pindos. The importance of these data lies in understanding the wider geotechnical environment belonging calcareous formations. Here's a description - evaluation of the laboratory tests carried out in accordance with the applicable specifications and described the method of sampling the configuration samples and determination of physical and mechanical properties of the obtained samples rocky limestone.

In this diploma thesis is at first a revision of field used process of interpretation of full acoustic well logging record in WellCAD program. This program uses an algorithm based on velocity analysis which uses semblance principle. Furthermore an independent interpretation of same data has been done in MATLAB program. In this one, individual steps of the process are verified using analysis of complex seismic trace - in particular by using instantaneous frequency. Both processes of interpretation were applied on wide spectrum of Bohemian Massif rocks with very different mechanic properties, so their robustness has been tested. The results of both interpretation processes have been compared and there haven't been found any fundamental differences, just minor, which can't be systematically eliminated with regard to WellCAD's capabilities. Interpreted values of Poisson's ratio and velocities of longitudinal and transversal have been used for comparison. As the credibility of mechanic parameters' values determined by interpretation processes mentioned above has been proven, other reasons of difference between mechanic parameters' values determined seismically and using static methods were searched for. At first a comparison of basic aspects in which the measuring methods differ (e.g. sample size,...

This document presents a methodology that (using tunable finite element models) allow validating during the development phase of the project, the behavior that equipment and mechanical systems will have once they are installed in microgravity. To achieve this purpose, a general methodology is developed initially. It can be applied to any space system or equipment necessary to know the behavior of any engineering parameter in case this parameter is affected by the particular space conditions. Later, the general methodology in applied over the VIF System. Thus, a concrete methodology for a mechanical system (VIF System) is developed in order to analyze a set of mechanical parameters that allow predicting on ground the mechanical behavior of this system once it is in microgravity. Once defined the mechanical parameters that are required to be analyzed and characterized form the VIF System (forces, moments, velocities, accelerations, etc), then the test phase started. In this phase, test equipment is developed and the VIF System is installed on. The VIF System is externally excited and it is acquired the VIF System behavior, for different levels of excitement, using the appropriate sensors (accelerometers, strain gauges, position sensors, etc). In this way, it is obtained the characterization of VIF System on ground. Once the VIF system has been already characterized on ground, a finite element model (FEM) of the VIF System is performed. This model is properly characterized to achieve the same behavior that the VIF System showed during previous tests. Finally, the FEM model is modified applying a zero gravity condition. This allows getting the VIF System behavior under these particular microgravity conditions. / El present treball planteja una metodologia que, basant-se fonamentalment en models d’elements finits caracteritzables, permet analitzar, a la fase de desenvolupament del projecte, el comportament que equips i sistemes mecànics tindran un cop es trobin instal•lats en condicions de microgravetat. Per aconseguir aquest propòsit, inicialment es desenvolupa una metodologia general que permet ser aplicada a qualsevol equip o sistema espacial on sigui necessari conèixer el comportament de qualsevol paràmetre d’enginyeria que es trobi afectat per les particulars condicions de l’espai. Posteriorment, la teoria general es particularitza pel cas concret d’un sistema mecànic, el Sistema VIF, plantejant així una metodologia particular que permet predir a terra el comportament que tindran un seguit de paràmetres mecànics quan el Sistema VIF es trobi en condicions de microgravetat. Un cop definits els paràmetres mecànics que es volen analitzar i caracteritzar del Sistema VIF (forces, moments, velocitats, acceleracions, etc), s’inicia la fase de test. En aquesta fase es desenvolupa un equip de test on s’hi instal•la el Sistema VIF. L’excitació externa que s’efectua sobre el Sistema VIF permet recollir, usant els sensors adients (acceleròmetres, galgues extensomètriques, sensors de posició, etc), el comportament del Sistema VIF per diferents nivells d’excitació. D’aquesta manera, s’obté la caracterització del Sistema VIF a terra. Una vegada es disposa del Sistema VIF ja caracteritzat a terra, cal realitzat un model d’elements finits (FEM) del Sistema VIF. Aquest model es caracteritza adequadament per tal que assoleixi el mateix comportament que mostrava el Sistema VIF durant la fase de tests. Finalment, s’aplica sobre el model FEM la condició d’ingravidesa imposant un valor de gravetat nul•la. D’aquesta manera, s’obté el comportament del Sistema VIF en aquestes particulars condicions de microgravetat que proporciona l’espai.

Η παρούσα διπλωματική εργασία έχει σαν αντικείμενο μελέτης την αποτίμηση των φυσικών και μηχανικών παραμέτρων των μαλακών βράχων σκληρών εδαφών. Η περιοχή μελέτης τοποθετείται στο βορειοδυτικό τμήμα της Πελοποννήσου και συγκεκριμένα στο Νομό Αχαΐας. Οι ιδιαιτερότητες των φυσικών χαρακτηριστικών των σχηματισμών αυτών απαιτούν τη συστηματική τους διερεύνηση. Για το λόγο αυτό η μελέτη τους αποκτά μεγάλο ενδιαφέρον. Η εργασία περιλαμβάνει τα παρακάτω στάδια: -Περιγραφή των γεωλογικών συνθηκών σε ευρεία κλίμακα και συγκέντρωση τεκτονικών και σεισμικών στοιχείων της ευρύτερης περιοχής μελέτης. -Λεπτομερής εξέταση, διαχωρισμός και ακριβής προσδιορισμός των θέσεων δειγματοληψίας της περιοχής μελέτης. -Δειγματοληψία από τους σχηματισμούς που απαντώνται στην περιοχή και εκτέλεση εργαστηριακών δοκιμών -Προσδιορισμός των φυσικών παραμέτρων των υπό εξέταση υλικών -Στατιστική επεξεργασία των τιμών των εργαστηριακών δοκιμών με σκοπό την εξαγωγή διαφόρων συμπερασμάτων για τη μηχανική συμπεριφορά των μαλακών βράχων. / The aim of this thesis is the study of natural and mechanical parameters of soft rocks – hard soil. The region of study is placed in the north-western department of Peloponnese and concretely in the Prefecture Achaia. The particularities of natural characteristics of this shapings require their systematic investigation. For this reason their study acquires big interest. The work includes the following stages: - Description of geological conditions in wide scale and concentration of tectonic and seismic elements of the wider region of study. - Examination and precise determination of places of sampling of region of study. - Sampling from the shapings in the region and implementation of laboratorial trials - Determination of natural parameters of materials under review - Statistical analysis of prices of laboratorial trials in order to export various conclusions on the mechanic behavior of soft rocks.

Magistriniame darbe nustatytos legiruotųjų konstrukcinių plienų ir jų suvirinimo siūlių medžiagų mechaninių ir deformavimo diagramos charakteristikų A1, α, sT priklausomybės būdingame intervale kambario ir aukštesnėje temperatūroje. Nuosekli statistinė analizė parodė, kad duomenys yra atsitiktiniai, nepriklausomi bei pasiskirstę pagal normalųjį dėsnį, o atlikta tyrimo rezultatų koreliacinė ir regresinė analizė, kad tarp daugumos medžiagų grupių deformavimo diagramos charakteristikų ir modifikuoto plastiškumo kriterijaus egzistuoja reikšmingas tiesinis koreliacinis ryšys. Darbe ciklinėms deformavimo diagramos charakteristikoms pagal mechanines savybes nustatyti, buvo apskaičiuoti analitinių priklausomybių koeficientai, bei patikrintas regresijos lygčių adekvatumas. Nustatant deformavimo diagramos charakteristikų reikšmes nuo modifikuoto plastiškumo kriterijaus nustatytame būdingame intervale gaunami tikslesni rezultatai, nes daugumai skaičiuotų ir eksperimentinių charakteristikų rezultatų sklaida intervaluose yra mažesnė lyginant su bendrų plienų ir jų suvirinimo siūlių medžiagų grupių rezultatų sklaida. Darbe pasiūlyti tiesinės priklausomybės koeficientai nuo modifikuoto plastiškumo kriterijaus, gali būti pritaikyti nustatant preliminarų inžinerijos šakose (energetikoje, naftoje) dirbančių mašinų ilgalaikiškumą, atsižvelgiant į jų eksploatacijos aplinką, darbo temperatūrą, naudojamas medžiagas. Magistrinio darbo tema buvo skaitoma ir aptarta 2013 m. gegužės 15 d. Šiaulių... [toliau žr. visą tekstą] / In this master thesis alloy structural steels and their weld joint materials cyclic stress–stain curves parameters A1, α, sT dependences on mechanical characteristic in the typical range at room and elevated temperatures are determined. Consistent statistical analysis of experimental results shown, that data is accidental, independence and normal distributed, also correlation - regression analysis shown, that almost for all groups of the materials exists a significant linear correlation between cyclic stress–stain curves parameters and modified plasticity criterion. In this final work, for parameters A1, α, sT from mechanical properties to determine, was calculated analytical dependence coefficients, also regression equations adequacy was verified. Determining value of deformation parameters from modified plasticity criterion in typical range, is better way, because the results is more accurate this is because for almost all computed and experimental characteristics results dispersion in ranges are lower comparing with total groups of alloy steels and their weld joint materials results dispersion. In this master thesis are suggested linear regression coefficients from modified plasticity criterion, which can be used for preliminary evaluation of lifetime for engineering industries machines considering of their operational environment, working temperature and what materials are used for machine‘s construction. Master's thesis has been read and discussed in May 15, 2013 at... [to full text]

En France, le secteur de la construction routière est le plus grand consommateur de matériaux granulaires, avec une consommation annuelle d'environ 200 millions de tonnes. Avec la pénurie de matériaux standards, la valorisation des sédiments dragués pour la construction routière pourrait constituer une solution intéressante.Les sédiments dragués se composent généralement d’une phase minérale, une phase organique (sous diverses formes) et une phase liquide (eau). La présence des Matières Organiques (MO) dans les sédiments, même en petites quantités, affecte leurs propriétés physiques et mécaniques.L'objectif principal de cette thèse est de proposer une méthode simple de caractérisation des matériaux organiques adaptée au domaine routier et d'étudier les effets de la teneur en MO sur les propriétés physiques et mécaniques des sédiments dragués. Pour y parvenir, une méthodologie spécifique pour reconstituer des mélanges avec différentes quantités de MO est proposée et une évaluation est faite des essais existants pour la caractérisation des MO.L'investigation des effets de la teneur en MO sur les paramètres physiques et mécaniques (considérés comme des paramètres clés dans le domaine de la construction routière) montre que même pour des teneurs en MO supérieures aux limites imposées dans les guides d’utilisation des matériaux standards, les sédiments restent compatibles avec la valorisation dans la technique routière. / In France, the road construction sector is the greatest consumer of granular materials, with a yearly consumption of about 200 million tons. With the shortage of standard materials, the valorization of dredged sediments for road construction could constitute an interesting solution.Dredged sediments generally consist of a mineral phase, an organic phase (in various forms) and a liquid phase (water). The presence of Organic Matter (OM) in sediments, even in small amounts, affects their engineering properties.The main objective of this study is to propose a simple method of characterization of organic materials adapted to the road construction and to study the effects of OM content on the physical and mechanical properties of dredged sediments. To this end, a specific methodology for reconstituting mixtures with different amounts of OM is proposed and an evaluation is made of existing tests for OM characterization. The investigation of the effects of OM content on physical and mechanical parameters (considered as key parameters in the field of road construction) shows that even for OM contents greater than the limits imposed in the guidelines for the use of standards materials, the dredged sediments remain compatible with the valuation in the road construction technique.

Diploma thesis deals with composite materiál and it is dedicated to steel fiber concreat. The thesis focuses on verification of mechanical parameters of the steel fiber concrete. Especially on the compressive (tensile) strength at first cracking and the compressive strength in cracked state. Testing was conducted on concrete different tensile with 30 kg on m3 steel fibers KrampeHarex DE 50/1,0 N. The thesis is divided into theoretical and experimental part.

Title: Changes in the mechanical parameters of women's hair during pregnancy Matters: We can look from different angles on the hair - as on a nanocomposite fiber and as on biomaterial changing with the origin and age. The hair doesn't differ only by lenght, stucture and color but also by diameter and shape. It reflects the overall health of the individual and all the processes in the organism of the individual and thus also the pregnancy. During pregnancy, hormonal changes take place which have an effect on the hair. Many women experience faster hair growth, extension and increased volume of the hair during pregnancy. This status is only temporary and lasts only to the childbirth. Aim: The aim of this work was to show the influence of pregnancy on mechanical parameters of hair and what direction this influence takes. Next, using questionnaires, to better solve the effect of particular pregnancy parameters on the hair, i.e. pregnancy order, sex of the child. Then, evaluate the whole problem using statistical tests and so make better sense of it. Methods: We'd selected a group of 64 pregnant women; hair samples were cut from them in the nape area each month throughout pregnancy. Each measurement started with evaluation of hair diameter with the use of optical microscope. Next, the hair had been...