This study examines the nanoindentation (energy inclusive) properties of 0.2 mg/kg alendronate treated ribs at one and three years against a vehicle treated control in a fresh-frozen, non-cold-mounted, condition. This was to verify if the tissue-level properties for 0.2 ALN treated beagles would increase because of an increased level of mineralization despite a microdamage increase. A total of twelve (12) skeletally mature (1–2 years old) female beagle dogs were treated daily for three years and one year with oral doses of vehicle (VEH, 1 mL/kg saline) or alendronate (ALN, 0.2 Merck, Rahway, NJ). The 0.2 mg dose corresponds, on a milligram per kilogram basis, to those used for treatment of postmenopausal osteoporosis. Transversely cut samples were ground and polished to 0.3μm, and were then mounted while nanoindentation was performed. The data obtained were analyzed using two modes of diamond area functions: ideal function and general function. The statistical analysis for the data were carried out using a repeated measured ANOVA (SAS V 9.1, Cary NC.) with the measured and calculated mechanical property (elastic modulus or hardness) or energy property (elastic work or plastic work) as the dependent variable and treatment (control, 1 year or 3 years) modeled as the subject. Either Turkey-Kramer or Bonferroni method was used to compute the pair-wise difference. The results indicate that when compared to one year, the three years of alendronate medication for postmenopausal osteoporosis did not have any effect on the strength of the canine cortical bone, whereas this had effect on the hardness of the subjects. This increase in the medication time resulted in an increase in the elastic work but a decrease in the plastic work. The two methods (modes) of diamond area function analysed showed different mechanical properties (elastic modulus and hardness).

Ce travail vise à étudier la rupture du gainage avec des essais mécaniques plus représentatifs des conditions RIA, en prenant en compte les blisters d'hydrures ainsi que le niveau élevé de biaxialité du chargement mécanique et des vitesses de déformation. Nous avons formé par thermodiffusion en laboratoire des blisters similaires à ceux observés sur des gaines de Zircaloy-4 irradiées en réacteur. Les caractérisations par métallographie, nanodureté, DRX et ERDA ont montré qu'un blister est constitué d'hydrures delta dont la concentration dans la matrice varie entre 80% et 100%, et que la matrice sous-jacente contient des hydrures radiaux. Nous avons modélisé la cinétique de croissance des blisters avec l'hystérésis de la limite de solubilité de l'hydrogène,puis défini le gradient thermique seuil permettant leur formation. Notre étude sur le comportement dilatométrique du zirconium hydruré montre le rôle important de la texture cristallographique du matériau, ce qui peut expliquer des différences de morphologie des blisters. En parallèle, des essais suivis par caméra infrarouge ont montré que des vitesses de déformation supérieures à 0,1/s induisent des échauffements locaux importants qui favorisent la localisation précoce de la déformation. Enfin, nous avons optimisé l'essai d'Expansion Due to Compression pour atteindre un niveau de biaxialité de déformation plane (essais HB-EDC et VHB-EDC), ce qui réduit fortement la déformation à rupture à 25°C et 350°C, mais seulement en l'absence de blisters. Un critère de rupture est proposé pour rendre compte de la baisse de ductilité des gaines en Zircaloy-4 non irradiées en présence de blisters. / Our aim is to study the cladding fracture with mechanical tests more representative of RIA conditions, taking into account the hydrides blisters, representative strain rates and stress states. To obtain hydride blisters, we developed a thermodiffusion setup that reproduces blister growth in reactor conditions. By metallography, nanohardness, XRD and ERDA, we showed that they are constituted by 80% to 100% of delta hydrides in a Zircaloy-4 matrix, and that the zirconium beneath has some radially oriented hydrides. We modeled the blister growth kinetic taking into account the hysteresis of the hydrogen solubility limit and defined the thermal gradient threshold for blister growth. The modeling of the dilatometric behavior of hydrided zirconium indicates the important role of the material crystallographic texture, which could explain differences in the blister shape. Mechanical tests monitored with an infrared camera showed that significant local heating occurred at strain rates higher than 0.1/s. In parallel, the Expansion Due to Compression test was optimized to increase the biaxiality level from uniaxial stress to plane strain (HB-EDC and VHB-EDC tests). This increase in loading biaxiality lowers greatly the fracture strain at 25°C and 350°C only in homogeneous material without blister. Eventually, a fracture criterion of unirradiated Zircaloy-4 cladding tube taking into account the blister depth is proposed.

Surface treatments used to improve the life of a material known as peening are already extensively used in industry. The main aim of peening is to introduce compressive resiudal stress to the surface and subsurface of a metallic material, however literature also includes a number of microstructural and mechanical effects that peening introduces to a material when the compressive residual stress is established. The aim of this dissertation is compare and contrast the mechanical and microstructural effects of a current industrial peening method called shot peening, with three new increasingly competitive surface treatments. These are laser shock peening, ultrasonic impact treatment and water jet cavitation peening. The surface finish, and changes in microstructure, hardness depth profile, residual stress depth profile and plastic work depth profile of the four surface treatments are analysed. The effect of the peening parameters on the material is also determined, such as length of time of treatment, shot size, step size, direction of treatment, and irradiance per centimetre squared. The effect of peening on the residual stress depth profile of a gas tungsten eight pass grooved weld is also determined. Welding is a known region of early failure of material, with one of the factors affecting this being the introduction of tensile residual stress to the surface and near surface of the weld. An analysis to determine if peening the welded region alters the residual stress was carried out. In all experiments in this dissertation, the material that was used was austenitic stainless steel, as this material is highly used, especially within the nuclear industry. The results of this dissertation show that different peening types and peenign parameters produce a variety of surface, microstructural and mechanical effects to austenitic stainless steel. Peening of an aaustenitic stainless steel welded region results in teh near surface tensile residual stress to alter to ccompressive residual stress.