A new testing method was introduced and developed to determine Mode I fracture toughness of disc type rock specimens. The new method was named as Straight Notched Disc Bending and it uses disc specimens under three-point bending. 3D Numerical modeling was carried out with a finite element program ABAQUS to find stress intensity factors for both well-known Semi-circular Bending specimen models and Straight Notched Disc Bending specimen models for varying disc geometries. Both specimen types included notches where a crack front is introduced at the tip of the notch to compute the stress intensity factors. For stress intensity analysis, crack front-upper loading point distance and span length between the two roller supports at the bottom boundary of the specimens were changed. Fracture toughness testing was carried on Ankara G&ouml / lbaSi pink colored andesite for both specimen types / crack front-upper loading point distance and span length between the two roller supports at the bottom boundary of the specimens were changed during the tests. For both specimen geometries, notch lengths changing from 5 mm to 20 mm were used. For each notch length, two different roller supports with span lengths 60 mm and 70 mm were used. For both methods, fracture toughness values determined by using numerically computed stress intensity factors and failure loads obtained from the experiments were very close / the new method was verified by comparing the results. The new method had advantages of lower confining pressure at the crack front and lower stress intensities with a possible smaller crack tip plasticity region.

Flattened Brazilian disc and modified ring test methods are attractive methods being simpler compared to the other mode I fracture toughness testing methods on rock cores. The aim of this study is to improve these simple methods to yield fracture toughness values that are close to the ones determined by the suggested methods. ABAQUS finite element program was used to determine stress intensity factors of models with various dimensions. Comparing fracture toughness to the results obtained by semicircular bending method tests (0.94 MPa&amp / #8730 / m for andesite and 0.56 MPa&amp / #8730 / m for marble) and the cracked chevron notched Brazilian disc method tests (1.45 MPa&amp / #8730 / m for andesite and 1.08 MPa&amp / #8730 / m for marble), proper geometrical parameters were investigated by changing diameter, central-hole diameter, and loading angle of Ankara andesite and Afyon marble specimens. Semicircular bending method results were lower than the cracked chevron notched Brazilian disc method results. With flattened Brazilian disc method, the closest results (1.45 MPa&amp / #8730 / m for andesite and 1.12 MPa&amp / #8730 / m for marble) to the suggested method was obtained by 54 mm diameter discs with loading angles between 32.5&deg / and 38.0&deg / and with thicknesses between 19 mm and 34 mm. With modified ring test on andesite, the closest results to the suggested method was obtained by 75 mm diameter discs with 8 mm central-hole diameter and 25&deg / loading angle (1.47 MPa&amp / #8730 / m for andesite and 1.07 MPa&amp / #8730 / m for marble), and with 14 mm central-hole diameter and 16&deg / loading angle (1.50 MPa&amp / #8730 / m for andesite and 1.05 MPa&amp / #8730 / m for marble).

Abdominal aortic aneurysms are a leading cause of death in the U.S. where 14,000 people die from aneurysm rupture and 178,000 are diagnosed each year. A novel alternative treatment for abdominal aortic aneurysms has been proposed, where a biodegradable polymer scaffold is photopolymerized in situ around the exterior of the aneurysm. This scaffold will mechanically constrain the aneurysm from further expansion, and will deliver a drug, doxycycline, to treat the underlying biological cause of the disease. In order for device development, a suitable polymer must be designed with appropriate mechanical properties, degradation rate, polymerization, and elution rate. Poly(β-amino ester) networks have been proposed as the material of choice; however, many of their structure-property relationships have yet to be determined. Therefore, the overall goal of this work is to determine the structure-property relationships of the poly(β-amino ester) networks in order to advance the design of the treatment, and has been divided into three objectives: (1) understand the structure-property relationships of poly(β-amino ester) networks, specifically the polymerization, degradation rate, and thermo-mechanical properties, (2) determine the impact of doxycycline incorporation on degradation rate and mechanical properties, (3) evaluate the effect of simulated physiological conditions on degradation rate and mechanical properties. In the initial chapters, the fundamental structure-property relationships are established between reactant chemical structure, step-growth polymerization, photopolymerization, thermo-mechanical properties, and degradation rate using a systematic approach of two homologous series of reactants. Further tailoring of degradation rate, water content, and modulus in vitro was performed by using a copolymer network. Doxycycline inhibited photopolymerization due to overlapping absorbance spectra with the photoinitiator, but full network formation occurred by increasing the photoinitiator concentration. Networks displayed varying controlled release rates, and the underlying release mechanism was determined for each network using established methods. In order to increase mechanical properties, a co-monomer, methyl methacrylate, was added to the network to increase the glass transition temperature, toughness, and deformation capacity. These co-networks displayed temporal-control of mechanical properties in simulated physiological conditions, since degradation caused a shift in the glass transition temperature, which changed the mechanical behavior of the network. The temporal-control of mechanical properties was further investigated under degradation conditions in vitro and in vivo. Due to the mechanically active loading environment in vivo, networks displayed a decrease in toughness, yet maintained mechanical properties similar to native biological tissues. These networks establish a multifunctional biomaterials platform with materials that can be easily synthesized, photopolymerized into various geometries, and sustain mechanical properties while undergoing degradation and therapeutic agent release.

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The paper presents results of a research project founded by the Swiss Federal Nuclear Inspectorate concerning the application of the Master Curve approach in nuclear reactor pressure vessels integrity assessment. The main focus is put on the applicability of pre-cracked 0.4T-SE(B) specimens with short cracks, the verification of transferability of MC reference temperatures T0 from 0.4T thick specimens to larger specimens, ascertaining the influence of the specimen type and the test temperature on T0, investigation of the applicability of specimens with electroerosive notches for the fracture toughness testing, and the quantification of the loading rate and specimen type on T0. The test material is a forged ring of steel 22 NiMoCr 3 7 of the uncommissioned German pressurized water reactor Biblis C. SE(B) specimens with different overall sizes (specimen thickness B=0.4T, 0.8T, 1.6T, 3T, fatigue pre-cracked to a/W=0.5 and 20% side-grooved) have comparable T0. T0 varies within the 1σ scatter band. The testing of C(T) specimens results in higher T0 compared to SE(B) specimens. It can be stated that except for the lowest test temperature allowed by ASTM E1921-09a, the T0 values evaluated with specimens tested at different test temperatures are consistent. The testing in the temperature range of T0 ± 20 K is recommended because it gave the highest accuracy. Specimens with a/W=0.3 and a/W=0.5 crack length ratios yield comparable T0. The T0 of EDM notched specimens lie 41 K up to 54 K below the T0 of fatigue pre-cracked specimens. A significant influence of the loading rate on the MC T0 was observed. The HSK AN 425 test procedure is a suitable method to evaluate dynamic MC tests. The reference temperature T0 is eligible to define a reference temperature RTTo for the ASME-KIC reference curve as recommended in the ASME Code Case N-629. An additional margin has to be defined for the specific type of transient to be considered in the RPV integrity assessment. This margin also takes into account the level of available information of the RPV to be assessed.

This work presents a fracture mechanics analysis of the cathodic delamination problem for the polyurethane/titanium and polyurea/steel interfaces. The nonlinear behavior of both polymers was investigated. The recent Marlow model was used to define the strain energy function of the polymers. Viscoelastic effects of the polyurea were also studied. The Marlow model was associated with a nine-term Prony series. This model was seen to represent experimental data relatively well for a wide range of strain rates both in tension and compression. The driving force for delamination, the strain energy release rate G, is presented for both interfaces. Cathodic delamination data for several temperatures are presented as crack growth rate as a function of crack driving force. The approach recognizes that both temperature and stress can be used as accelerated life testing parameters. / text

High rolling contact fatigue parts are vital for the long service life of fuel pumps. Cummins Fuel Systems are currently using an M2 tool steel for one of the most important roller bearing application in their pumps, namely the cam follower. The future design of the cam follower is a pin-less tappet roller. The wear and fatigue properties of the roller is vital to ensure reliability of the fuel system. M2 tool steel is an expensive material and becomes even more so if diamond like coating (DLC) is needed to decrease the friction coefficients. To cut costs of the fuel pump it might be possible to replace the M2 tool steel with 52100 steel (100Cr6). Competitive methods have proven that carbonitrided 52100 can reach excellent wear and fatigue properties making it a candidate to replace M2 tool steel. How the properties of hardness, toughness and compressive residual stresses are developed in 52100 and how they affect the fatigue and wear resistance has been researched from the literature. A big part of this project was to do an extensive analysis of a roller bearing that was believed to have gone through one of these competitive methods that produce excellent wear and fatigue resistance. The analysis was done with background to the knowledge gathered from the literature. Finally process trials were set up to carbonitride 52100 steel samples. The trials were done to develop a better understanding of how adding carbon together with nitrogen to the surface of 52100 steel will influence the metallurgical parameters that results in good wear and fatigue resistance. From this analysis Cummins hope to create a process recipe that can be used for carbonitriding the cam follower and maybe other components in their fuel systems.

Ou study focuses on the effects of phase transformations on crack propagation. We want to understand the changes of fracture toughness during welding. In this work, fracture toughness is expressed by J-integral. There are many experimental methods to obtain the critical toughness JIC but they are impractical for our investigation during phase transformation. That is the reason why we have proposed a method coupling mechanical tests, digital image correlation and finite element simulation. The fracture tests are implemented on pre-cracked single edge notched plate sample which is easy for machining and heat conduct during phase transformation. The tests are conducted at different temperatures until rupture. Digital image correlation gives us the displacement information on every sample. Each test is then simulated by finite element where the fracture toughness is evaluated by the method G-Theta at the crack propagation starting moment found by potential drop method and digital image correlation technical. Two materials have been studied, 15Cr-5Ni martensitic precipitation hardening stainless steel and 16MND5 ferritic low carbon steel. For these two materials, different test temperatures were chosen before, during and after phase transformation for testing and failure characterization of the mechanical behavior. Investigation result shows that metallurgical phase transformation has an influence on fracture toughness and further crack propagation. For 15-5PH, the result of J1C shows that the as received 15-5PH has higher fracture toughness than the one at 200°C. The toughness is also higher than the original material after one cycle heat treatment probably due to some residual austenite. Meanwhile, pure austenite 15-5PH at 200°C has higher fracture toughness than pure martensitic 15-5PH at 200°C. For 16MND5, the result also proves that the phase transformation affects fracture toughness. The as received material has bigger J1C than the situation where it was heated to 600°C. On the other hand, the material at 600°C just before isothermal bainite transformation after the austenitization during cooling process also has higher fracture toughness than the one at 600°C before austenitization. These two conclusions are consistent well with the result of 15-5PH. But the final situation of 16MND5 after one cycle heat treatment has a slightly smaller J1C than the receiving situation. It means that one cycle heat treatment hasn't an significant influence on 16MND5fracture toughness. Conclusions show that one should pay attention to the heating period before austenitization of the substrate material when people do the welding as the higher temperature will bring the lower fracture toughness during this process. While during cooling period, the fracture toughness doesn't change a lot during, before or after the cooling induced phase transformation. Even for 15-5PH, it has a better fracture toughness after the martensite transformation than before.

Syfte och frågeställningar: Denna studie har granskat begreppet mental tuffhet och dess roll i sporten baseboll. Syftet var att, genom en kvantitativ och kvalitativ metod, undersöka hur fyra unga svenska pitchers reflekterar över de egenskaper, färdigheter och verktyg associerade till mental tuffhet för att skapa en ökad förståelse i unga pitchers mentala förmåga. Detta genomförs som den första svenska idrottspsykologiska studien i sitt slag. Hur upplever unga basebollspelare olika aspekter av de innefattande egenskaper och färdigheter som omfattar mental tuffhet? Besitter unga basebollspelare som håller en jämn prestationsnivå under match även en högre grad av mental tuffhet? Metod: Studien består av en kvalitativ och kvantitativ metod där ett urval av fyra pitchers först statistiskt har observerats under match för att sen intervjuas med en semistrukturerad intervjumetod. Statistikinsamling genomfördes med syftet att kvantitativt granska deras prestation under match sett till lyckade och misslyckade kast. Efter varje match har testpersonerna intervjuats med utgångspunkt från matchens statistik samt fyra idrottspsykologiska teman; självförtroende, motivation, idrottspsykologiska verktyg och målsättning. Denna metodtriangulering har använts för att granska hur de hanterar mentalt tuffa situationer i match. Resultat: Ett antal faktorer framkom i studiens analys som relaterade till mental tuffhet: fysiska och mentala förberedelser, den fysiska förmågan, fokusering/refokusering, viljan att bli bättre samt att hantera motgång. Även ett antal påverkande faktorer framkom: utbildning, lagkamrater/omgivning, yttre krav och externa distraktioner. Slutsats: Generellt framkom mental tuffhet som ett brett och komplext begrepp kopplat till många olika idrottspsykologiska faktorer. Kopplingar mellan self-efficacy och mental tuffhet har gjorts då testpersonerna beskrev prestationsbaserade självförtroende i sin tro på sin egen fysiska och tekniska förmåga, samt motivation i sin fysiska utveckling. Det framkom även att resultatets påverkande faktorer spelade en stor roll i hur de senare kände mental tuffhet i match. Nyckelord: Baseboll, pitchers, mental tuffhet, self-efficacy, självförtroende, motivation, visualisering, självprat, målsättning

Low temperature cleavage fracture behaviour was investigated using four experimental microalloyed bainitic plate steels. The four plate samples were produced by different thermomechanical processing (TMP) schedules and had yield strengths in the range 540 - 670 MPa. Microstructures were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and electron back scattered diffraction (EBSD). Quantitative data was obtained for prior austenite grain (PAG) size, volume fractions of two bainite types (conventional bainite and acicular ferrite) and EBSD 15° domain size. Charpy impact tests (using two notch orientations) were carried out over a range of temperatures. Cleavage facet sizes were measured on -196°C Charpy samples. The range of TMP schedules produced variations in PAG width, type of bainite and 15° domain size. The effects of these three microstructural features on cleavage crack propagation are discussed. Results indicate that the microstructures are controlled by i) deformation below TNR and ii) accelerated cooling rate. Domain structure reflects TMP. There is no clear correlation between domain size and cleavage facet size. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-07-30 19:17:01.25