<p> The effects of small additions of Fe2O3, GeO2, Ta2O5, V2O5, TiO2, and SiO2 on the microstructure and fracture toughness of magnesia enriched doloma were investigated. Effects of up to 5% additive oxides on grain growth and sintering in MgO and CaO were determined in preliminary tests. One percent additions were made to 40%, 60% and 80% MgO dolomas and the fracture toughness at temperatures up to 1500°C determined using the single edge notched beam specimen. Fracture surfaces were studied on the scanning electron microscope to determine fracture mode. Silica and Ta2O5 doped material showed high toughness at 1500°C possibly due to microcracks, while TiO2 resulted in formation of a viscous grain boundary film producing high toughness at 1300°C followed by a rapid decline by 1500°C. In undoped samples increases in MgO resulted in the appearance of a toughness peak near 1300°C. This was attributed to grain boundary segregation of impurities.</p> / Thesis / Master of Engineering (MEngr)

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Participants were 20 (14 females and 6 males) first-time marathon runners registered for the Bank of America Chicago Marathon in Chicago, IL on October 7th, 2013. Participants were recruited for the purpose of exploring the effects of a 4-week individualized imagery training program on mental toughness and flow and asked to complete a demographics survey, the Movement Imagery Questionnaire (MIQ), the Sport Imagery Questionnaire (SIQ), Short Flow States Scale-2 (Short FSS-2), Sport Mental Toughness Questionnaire (SMTQ), and a Pre-Imagery Training Interview and then be divided into an experimental and control group (prior to running the marathon). Participants in the experimental group received a modified copy of a Chicago marathon training video and a tailored 10-15 minute imagery training session while participants in the control group received only the Chicago marathon training video. Next, participants ran in the Bank of America Chicago Marathon and, after the race, met with the researcher to complete the SIQ, Short FSS-2, SMTQ, and a post-imagery interview. Several themes emerged concerning the runners' understanding of the marathon course, race concerns, race goals, and race strategies at pretest as well as both positive and negative experiences during the marathon and their methods for coping and using the imagery during the marathon (reported at posttest). The experimental group had a moderate positive correlation between the imagery subscales of cognitive general (CG) and motivational-general mastery (MG-M) and mental toughness (MT) (r(6) = .761 and r(6)= .685, p &lt; .05 respectively). There was a moderate positive correlation between the imagery subscales of CG and MG-M and flow (r(6) = .719 and r(6) = .783, p &lt; .05 respectively). This would indicate that individuals high in using imagery as a means to goal set as well as master the course tended to have high flow scores. Cognitive specific (CS), motivational specific (MS), and motivational-general arousal (MG-A) had a small, non-significant correlation with MT (r(6) = .492, r(6) = .321, r(6) = .341, p &lt; .05) and a moderate relationship with flow (r(6) = .522, r(6) = .593, r(6) = .529, p &lt; .05). There is a high positive relationship between flow and MT (r(6) = .906, p &lt; .05), indicating that individuals who experienced high levels of flow also experienced high levels of MT. Control group participants had a moderate inverse relationship between CG and MT (r(4) = -.659, p &lt; .05) and moderate positive relationships between CG, MS, and MG-A and flow (r(4) = .662, r(4) = .710, and r(4) = .552, p &lt; .05 respectively) within control participants. For the control participants, flow and MT were not found to have a significant relationship (r(4) = .310, p &lt; .05); these results are consistent with the control participants' imagery, flow, and MT scores suggesting that flow did not have any effect on MT. Overall, the tailored imagery script training was found to be helpful for both flow and mental toughness. Recommendations for future research should focus on developing a 6-week psychological skills training program for first time marathon runners and developing research that focuses on periodizing imagery to coincide with runners' marathon training programs. / Kinesiology

The purpose of this study was to accomplish three major objectives: to quantitatively understand the applicability of an existing list of characteristics of mental toughness to a population of ultramarathon runners, to establish a new definition of mental toughness specific to ultra runners, and to conduct interviews to understand experiences, examples, and development of mental toughness. A mixed-methods approach was utilized with online surveys and semi-structured interviews. Participants were ultramarathon runners who had completed at least one organized ultramarathon event of 50 miles or more, all of whom were at least 18 years of age. The online survey yielded 408 completed questionnaires and 476 definitions of mental toughness in ultramarathon running. The online survey consisted of an open-ended question on defining mental toughness, and a list of 30 characteristics of mental toughness from Jones and colleagues' (2007) mental toughness study on elite athletes. The survey utilized a 5-point Likert scale, and a Basic Demographic Questionnaire in addition to questions relevant to running experience. The existing characteristics represented limited applicability to the population of ultramarathon runners, with most prevalent attributes on drive towards success, goal attainment, learning from failure, and coping under pressure. In the 476 definitions of mental toughness, the most prominent themes were persistence, perseverance, utilization of psychological skills, and adapting to environmental and duration-related obstacles. Semi-structured interviews were conducted with 12 randomly selected ultramarathon runners. Interviews were designed to verify a raw definition of mental toughness in ultramarathon runners, identify traits of mentally tough ultra runners, understand experiences and examples of mental toughness, and understand how mental toughness could be developed. Grounded theory was utilized to isolate themes; many factors emerged and were categorized based on research questions. The definition of mental toughness was supported with the addition of an emotional and perceptual component. Traits of mentally tough runners supported the traits found in the definitions of mental toughness. Experiences and examples of mental toughness included situations of using psychological skills and witnessing a runner overcome adversity. Lastly, development of mental toughness was most highlighted in social aspects of the ultra culture and experiences both in running and in life. / Kinesiology

Effective treatment of carbon fiber components to improve delamination resistance is vital to the application of such materials since delamination is one of the biggest concerns regarding the use of composites in the aerospace sector. Due to the significant application benefit gained from increased stiffness to density ratio with composite materials, innovative developments resulting in improved through-thickness strength have been on the rise. The inherent anisotropy of composite materials results in an added difficulty in designing structural elements that make use of such materials. Proposed techniques to improve the through-thickness strength of laminar composites are many and varied; however all share the common goal of improving inter-laminar bond strength. This research makes use of novel materials in the field of wet flocking and Z-pinning. Cellulose nanofibers (CNFs) have already demonstrated excellent mechanical properties in terms of stiffness and strength, originating at the nano-scale. These materials were introduced into the laminate while in a sol-gel suspension in an effort to improve load transfer between laminate layers. The effect of CNFs as lightweight renewable reinforcement for CFRPs will be investigated. Carbon nanotube (CNT) additives were also considered for their beneficial structural properties. / Master of Science

The work described herein examines the fracture behavior of steels used in bridge applications. As part of Transportation Pooled Fund (TPF) Project 5-238, Design and Fabrication Standards to Eliminate Fracture Critical Concerns in Steel Members Traditionally Classified as Fracture Critical, researchers aim to take advantage of advances made in both steel production technology and in the field of fracture mechanics. Testing and analysis of both conventional and High Performance Steel (HPS) grades of bridge steel was conducted as part of this study. This includes both Charpy V-Notch testing, as well as more rigorous elastic-plastic fracture toughness testing. Analysis includes the application of the master curve methodology to statistically characterize fracture behavior in the ductile to brittle transition region. In addition, a database of historic bridge fracture toughness data was compiled and re-analyzed using plasticity corrections to estimate elastic-plastic fracture toughness. Correlations between Charpy V-Notch impact energy and fracture toughness, which forms the basis for the current material specification, were also examined. Application of fracture toughness characterization of both new and historic data results in updated methodologies for addressing fracture in bridge design. / Ph. D.

Determining the factors that contribute to mental toughness development in athletes has become a focus for researchers as coaches, athletes, and others extol its influence on performance success. In this study we examined a model of mental toughness development based on achievement goal theory, assessing the relations between motivational climates, goal orientations, and mental toughness. Five hundred ninety-nine varsity athletes, representing 13 different sports from six different high schools in a southwestern United States school district, participated in the study. Athletes completed self-report measures assessing parent, peer, and coach motivational climates, goal orientations, and their mental toughness. Initially, I examined the measurement model and found it fit the data well both in the exploratory (SRMR = .06; CFI = .94) and confirmatory (SRMR = .06; CFI = .95) samples. Second, the structural model was examined and found to fit the data well in both the exploratory (SRMR = .08; CFI = .93) and confirmatory samples (SRMR = .07, CFI = .95). Parent task-involving climate, (β = .55; p < .05) and coach task-involving climate (β = .32; p < .05), but not peer task-involving climate (β = .05), were associated with task goal orientation (R2 = .57). Ego goal orientation (R2 = .32) was explained by peer ego-involving climate (β = .15; p < .05), parent ego-involving climate (β = .39; p < .05), and coach ego-involving climate (β = .16; p < .05). Finally, only task goal orientation (β = .75; p < .05) was related to the athletes’ mental toughness (R2 = .56); the ego goal orientation pathway was not significant (β = .04). These results speak to the potential positive influence of parents and coaches on athletes’ mental toughness through their endorsement of task-involving messages and pursuits leading to the development of a task goal orientation.

Os ensaios mecânicos são mundialmente empregados para caracterização e implementação de diversos materiais. Dentre a vasta gama de ensaios existentes, o ensaio de impacto convencional é consagrado no meio científico, industrial e na indústria do óleo e gás onde a sua função básica é determinar a energia total absorvida na fratura de um corpo-de-prova entalhado conforme as recomendações da norma ASTM E23. Entretanto, a energia global absorvida possui um valor de uso muito limitado e ela normalmente não é aceita como um indicador quantitativo da resistência à fratura do material. Assim, com a utilização de uma máquina de ensaios de impacto instrumentada, torna-se possível a aquisição de um maior número de informações obtidas através de um ensaio de impacto clássico, como por exemplo, o estudo detalhado da integridade estrutural de materiais utilizados na fabricação de dutos. Desta maneira, o presente trabalho tem como objetivo avaliar a tenacidade de um duto de aço API 5L X70 sem costura, com 11 polegadas de diâmetro externo e ½ polegada de parede, frente a uma falha dinâmica, através da tenacidade a fratura, comparando carregamento estático com dinâmico através dos resultados de J0,2 e Jm. Entretanto a tenacidade a fratura é consideravelmente afetada para altas taxas de deformação, com redução de aproximadamente 30% nas amostras com orientação de entalhe X-Y (defeito lateral passante) e de aproximadamente 40% nas amostras com orientação de entalhe X-Z (defeito superficial), demostrados através do JΔinit. / Mechanical testing are worldwide employed for materials characterization and implementation. Among the large group of the existing tests, the conventional impact test has been used for industry and academic fields, especially oil and gas engineering in order to evaluate the energy absorbed of a notched sample, according to the ASTM E23 standard. However, the energy absorbed has a limited use and is not usually accepted as a quantitative indicator of the fracture thougness. Thus, by using an instrumented impact test, there will be an increasing in the amount of information obtained than the traditional impact test and, thefore, a detailed study of the structural integrity of materials can be carried out for manufacturing of pipes. Hence, this study aims to characterize a pipe steel API 5L X70 seamless, with 11 inches outside diameter and ½ inche of wall, against dynamic failure through fracture toughness, comparing static loading with dynamic through the results of J0,2 and Jm. However, fracture toughness is considerably affected at high deformation rates, with a reduction of approximately 30% in X-Y notch (through thickness defect) and approximately 40% in X-Z notch (surface defect) samples, demonstrated for JΔinit.

Concrete structures may be subjected to dynamic loading during their service life. Understanding the dynamic properties of concrete structures is becoming critical because of the increased concern about the dynamic loading of both civilian and military structures, and especially, the recent increase in terrorist attacks on structures. Fiber reinforced concrete (FRC) is known to exhibit superior performance in its post-peak energy absorption capacity, (i.e., toughness) under flexural and tensile loading. However, the behavior of fiber reinforced concrete under compressive impact has not previously been investigated. In the present research, the response of fiber reinforced concrete was investigated over the full strain rate regime, from static loading to high strain rate loading, and finally to impact loading. The compressive toughness of FRC under static loading was studied using an existing Japanese standard (JSCE SF-5). Then, a test method for FRC under compressive impact loading was developed, involving the use of a high speed video camera system to measure the deformation of FRC cylinders under compressive impact. The strain rate sensitivity of FRC in both flexure and compression was also fully investigated. FRC was found to have higher strengths under impact loading (both flexural and compressive) than under static loading. The compressive toughness under impact loading increased due to the high peak load and the high strain capacity. FRC under flexural impact loading showed a greater strength improvement than under static flexure. FRC displays a much higher Dynamic Improvement Factor (DIF) under flexural impact than under compressive impact. It gave an overall higher performance under impact than under static loading. It also exhibited a higher strain rate sensitivity than plain concrete in both compression and flexure. Damage analysis, in terms of loss of strain energy, was carried out based on damage mechanics principles. Damage was found to increase with increasing strain rate. A new constitutive model was proposed to account for the relationship between DIF (Comp) and strain rate and the data derived from the model were found to be consistent with the experimental results.

Concrete structures may be subjected to dynamic loading during their service life. Understanding the dynamic properties of concrete structures is becoming critical because of the increased concern about the dynamic loading of both civilian and military structures, and especially, the recent increase in terrorist attacks on structures. Fiber reinforced concrete (FRC) is known to exhibit superior performance in its post-peak energy absorption capacity, (i.e., toughness) under flexural and tensile loading. However, the behavior of fiber reinforced concrete under compressive impact has not previously been investigated. In the present research, the response of fiber reinforced concrete was investigated over the full strain rate regime, from static loading to high strain rate loading, and finally to impact loading. The compressive toughness of FRC under static loading was studied using an existing Japanese standard (JSCE SF-5). Then, a test method for FRC under compressive impact loading was developed, involving the use of a high speed video camera system to measure the deformation of FRC cylinders under compressive impact. The strain rate sensitivity of FRC in both flexure and compression was also fully investigated. FRC was found to have higher strengths under impact loading (both flexural and compressive) than under static loading. The compressive toughness under impact loading increased due to the high peak load and the high strain capacity. FRC under flexural impact loading showed a greater strength improvement than under static flexure. FRC displays a much higher Dynamic Improvement Factor (DIF) under flexural impact than under compressive impact. It gave an overall higher performance under impact than under static loading. It also exhibited a higher strain rate sensitivity than plain concrete in both compression and flexure. Damage analysis, in terms of loss of strain energy, was carried out based on damage mechanics principles. Damage was found to increase with increasing strain rate. A new constitutive model was proposed to account for the relationship between DIF (Comp) and strain rate and the data derived from the model were found to be consistent with the experimental results.