NDE for Characterizing Oxidation Damage in Reinforced Carbon-Carbon

In this study, coated reinforced carbon-carbon (RCC) samples of similar structure and composition as that from the NASA space shuttle orbiter s thermal protection system were fabricated with slots in their coating simulating craze cracks. These specimens were used to study oxidation damage detection and characterization using NDE methods. These specimens were heat treated in air at 1143 and 1200 C to create cavities in the carbon substrate underneath the coating as oxygen reacted with the carbon and resulted in its consumption. The cavities varied in diameter from approximately 1 to 3 mm. Single-sided NDE methods were used since they might be practical for on-wing inspection, while x-ray micro-computed tomography (CT) was used to measure cavity sizes in order to validate oxidation models under development for carbon-carbon materials. An RCC sample having a naturally-cracked coating and subsequent oxidation damage was also studied with x-ray micro-CT. This effort is a follow-on study to one that characterized NDE methods for assessing oxidation damage in an RCC sample with drilled holes in the coating. The results of that study are briefly reviewed in this article as well. Additionally, a short discussion on the future role of simulation to aid in these studies is provided

Impact Resistance of EBC Coated SiC/SiC Composites

Impact performance of 2-D woven SiC/SiC composites coated with 225 and 525 m thick environmental barrier coating (EBC) was investigated. The composites were fabricated by melt infiltration and the EBC was deposited by plasma spray. Impact tests were conducted at room temperature and at 1316 C in air using 1.59-mm diameter steel-balls at projectile velocities ranging from 110 to 375 m/s. Both microscopy and nondestructive evaluation (NDE) methods were used to determine the extent of damage in the substrate and coating with increasing projectile velocity. The impacted specimens were tensile tested at room temperature to determine their residual mechanical properties. At projectile velocities less than 125 m/s, no detectable damage was noticed in the MI SiC/SiC composites coated with 525 m EBC. With increase in projectile velocity beyond this value, spallation of EBC layers, delamination of fiber plies, and fiber fracture were detected. At a fixed projectile velocity, the composites coated with 525 m EBC showed less damage than the composite coated with 225 m EBC. Both types of EBC coated composites retained a large fraction of the baseline properties of as-fabricated composites and exhibited non-brittle failure after impact testing at projectile velocities up to 375 m/s. Exposure of impact tested specimens in a moisture environment at 1316 C for 500 hr indicated that the through-the-thickness cracks in the EBC coating and delamination cracks in the substrate generated after impact testing acted as conduits for internal oxidation

Mechanical Properties of 17-4PH Stainless Steel Foam Panels

Rectangular 17-4PH stainless steel sandwiched foam panels were fabricated using a commercial manufacturing technique by brazing two sheets to a foam core. Microstructural observations and ultrasonic nondestructive evaluation of the panels revealed large variations in the quality of the brazed areas from one panel to the next as well as within the same panel. Shear tests conducted on specimens machined from the panels exhibited failures either in the brazed region or in the foam core for the poorly brazed and well-brazed samples, respectively. Compression tests were conducted on the foam cores to evaluate their elastic and plastic deformation behavior. These data were compared with published data on polymeric and metallic foams, and with theoretical deformation models proposed for open cell foams

Nondestructive Evaluation (NDE) for Characterizing Oxidation Damage in Cracked Reinforced Carbon-Carbon

In this study, coated reinforced carbon-carbon (RCC) samples of similar structure and composition as that from the NASA space shuttle orbiter's thermal protection system were fabricated with slots in their coating simulating craze cracks. These specimens were used to study oxidation damage detection and characterization using nondestructive evaluation (NDE) methods. These specimens were heat treated in air at 1143 C and 1200 C to create cavities in the carbon substrate underneath the coating as oxygen reacted with the carbon and resulted in its consumption. The cavities varied in diameter from approximately 1 to 3mm. Single-sided NDE methods were used because they might be practical for on-wing inspection, while X-ray micro-computed tomography (CT) was used to measure cavity sizes in order to validate oxidation models under development for carbon-carbon materials. An RCC sample having a naturally cracked coating and subsequent oxidation damage was also studied with X-ray micro-CT. This effort is a follow-on study to one that characterized NDE methods for assessing oxidation damage in an RCC sample with drilled holes in the coating

Architectural Effects on Impact Resistance of Uncoated MI SiC/SiC Composites

Impact tests were conducted on uncoated 2D and 2.5D MI SiC/SiC composite specimens at room temperature and 1316 C in air. The specimens were analyzed before and after impact using optical microscopy, pulsed thermography (PT) and computed tomography (CT). Preliminary results indicate the following. Both 2-D and 2.5D composites show increase in surface and volumetric damages with increasing impact velocity. However, 2-D composites are prone to delamination cracks. In both 2D and 2.5D composites, the magnitude of impact damage at a fixed impact velocity is slightly greater at room temperature than at 1315 C. At a fixed projectile velocity and test temperature, the depth of penetration of the projectile into the substrate is significantly lower in 2.5D composites than in 2D composites. Fiber architecture plays a significant role controlling impact damage in MI SiC/SiC composites

Osteoinductive PolyHIPE Foams as Injectable Bone Grafts

We have recently fabricated biodegradable polyHIPEs as injectable bone grafts and characterized the mechanical properties, pore architecture, and cure rates. In this study, calcium phosphate nanoparticles and demineralized bone matrix (DBM) particles were incorporated into injectable polyHIPE foams to promote osteoblastic differentiation of mesenchymal stem cells (MSCs). Upon incorporation of each type of particle, stable monoliths were formed with compressive properties comparable to control polyHIPEs. Pore size quantification indicated a negligible effect of all particles on emulsion stability and resulting pore architecture. Alizarin red calcium staining illustrated the incorporation of calcium phosphate particles at the pore surface, while picrosirius red collagen staining illustrated collagen-rich DBM particles within the monoliths. Osteoinductive particles had a negligible effect on the compressive modulus (∼30 MPa), which remained comparable to human cancellous bone values. All polyHIPE compositions promoted human MSC viability (∼90%) through 2 weeks. Furthermore, gene expression analysis indicated the ability of all polyHIPE compositions to promote osteogenic differentiation through the upregulation of bone-specific markers compared to a time zero control. These findings illustrate the potential for these osteoinductive polyHIPEs to promote osteogenesis and validate future in vivo evaluation. Overall, this work demonstrates the ability to incorporate a range of bioactive components into propylene fumarate dimethacrylate-based injectable polyHIPEs to increase cellular interactions and direct specific behavior without compromising scaffold architecture and resulting properties for various tissue engineering applications

Measuring glomerular filtration rate using chromium-51 EDTA: body surface area normalization before or after Brochner-Mortensen correction?

We read with interest the article by Pottel et al. [1] 'Measuring glomerular filtration rate using 51Cr-EDTA: body surface area normalization before or after Bröchner-Mortensen correction?' The authors question the basis for the recommendation in the British Nuclear Medicine Society (BNMS) guidelines[2] that glomerular filtration rate (GFR) measurements using the slope-intercept (SI) method be corrected for body surface area (BSA) before applying the Bröchner-Mortensen (BM) correction for the missing area under the curve (AUC)

Estudo de caso : avaliação do impacto no desempenho e satisfação da força de trabalho com a reestruturação organizacional do departamento de gestão integrada (DGI) - UFRGS

A administração pública no Brasil é um tema bastante estudado e criticado por diversos autores, pois ainda está imersa em dúvidas acerca das melhores governanças, práticas de gestão e estruturas organizacionais que impactem positivamente o desempenho e, consequentemente, promova o crescimento e vigor dessas instituições. O setor da administração pública em nosso país é constantemente criticado pela disfunção da burocracia pertinente ao sistema, bem como a dificuldade de acompanhar as mudanças que são vivenciadas pelo setor privado, por exemplo. No presente trabalho, é realizado um estudo de caso no Departamento de Gestão Integrada (DGI) da PROPLAN – UFRGS (Universidade Federal do Rio Grande do Sul), que passou por mudanças na sua atuação e função como departamento perante a instituição. As modificações que foram propostas ao departamento podem ser divididas em dois campos. O primeiro em relação à orientação e função do departamento como um todo, que também influenciou uma mudança de mesmo teor em suas divisões internas. O segundo campo, pelo qual as modificações passaram, é o da força de trabalho, ou seja, pessoas. Em outras palavras, uma realocação de funções que promovesse um melhor aproveitamento das competências dos membros foi promovida. O presente estudo traça um paralelo entre o período anterior as modificações em contraste com o período após as modificações, verificando, junto ao departamento, questões ligadas ao desempenho e satisfação das pessoas que trabalham nesse espaço. Com os resultados, foi possível concluir que houve um aumento na satisfação geral dos membros, bem como aspectos relativos ao desempenho foram impactados positivamente pelas mudanças promovidas no DGI.Public administration in Brazil is a theme widely studied and criticized by authors in this area, because it stills immerged in doubts concerning the best managing practices, governance and organizational structures that impact positively the performance and, as a result, generate growth in this kind of institutions. The public administration sector in Brazil is constantly criticized by its burocracy disfunction related to the system it is involved, as well as a strong effort to be up to date with the changes that happen in the private sector of the economy. In this study, its presented a case study in the “Departamento de Gestão Integrada - (DGI)” which can be understood as the department responsible for the strategy deployment in the institution, that has been under several changes in its function an operation towards the university (Universidade Federal do Rio Grande do Sul – UFRGS). The changes on the department can be split in two, in order to be easily understood. The first is related to the orientation and function of the entire department, that influenced changes in its intern divisions. The second point in which the changes went through is people functions in the department. In other words, shifts in personal roles in the department aiming a better exploitation of each ones capacities and competences was implemented. This case study draws a parallel between the period before the changes and after them, verifying issues linked to the department’s overall performance and personal satisfaction with the role each person has in the organization. Analyzing the results, it was possible to conclude an increase in people satisfaction and aspects related to the department’s performance