Ceramics have been widely used for personnel and vehicle armour because of their desirable properties such as high hardness and low density. However the brittle nature associated with the ceramic materials, i.e. low toughness, reduces their ability to withstand multiple ballistic hits. The present work is focused on ceramic armour materials made from alumina and zirconia toughened alumina (ZTA). The effects of grain size and zirconia phase transformation toughening on the mechanical and high strain rate properties in both materials were investigated in detail. Alumina, 10%, 15% and 20% nano ZTA with 1.5 mol% yttria stabiliser were produced with various grain sizes. The processing of the materials started from suspension preparation, spray freeze drying of the suspension and die pressing to produce homogeneous green bodies with densities above 54%. Then, the green bodies were sintered using conventional single stage and/or two stage sintering to produce the samples with full density and a range of grain sizes (0.5 to 1.5 µm alumina grains and 60 to 300 nm zirconia grains). The effects of the processing conditions on the microstructures were studied and the optimum processing route for each sample was determined. The mechanical properties of the alumina and ZTA samples were investigated, including Vickers hardness, indentation toughness, 4-point bend strength and wear resistance. The results showed that, with an increasing amount of zirconia addition, evident increases of the toughness, strength and wear resistance properties were observed, whilst the hardness reduced slightly correspondingly. The effect of density and grain sizes on the hardness and toughness were studied as well: larger alumina grain size led to a higher hardness and negligible change in toughness, whilst the zirconia grain coarsening enhanced the phase transformation toughening effect and the samples displayed a higher toughness. In addition to the investigation of the mechanical properties, the alumina and nano ZTA samples were subjected to high strain rate testing, including split Hopkinson pressure bar (SHPB) (8-16 m/s) and gas gun impact testing (100-150 m/s). The high strain rate performances were compared in terms of their fracture behaviours, fragmentation process and fragment size distribution. Raman spectroscopy was used to measure the amount of zirconia phase transformation in ZTA samples after the high strain rate testing. The residual stress and dislocation density in alumina grains after testing were quantitatively measured using Cr3+ fluorescence spectroscopy. The results indicated that zirconia phase transformation can reduce the residual stress and dislocation densities in the ZTA samples, resulting in less damage, lower plastic deformation and less crack propagation. In addition, a nano zirconia material with 1.5 mol% yttria stabiliser (1.5YSZ) was subjected to a gas gun impact test with a very high impact speed (142 m/s); a deep projectile penetration was observed, due to the low hardness of the pure zirconia, whilst the sample stayed intact. The result further confirmed that the zirconia phase transformation toughening effect can improve the sample's high strain rate performance.

Objetivo: investigar a associação entre estresse no trabalho e a autopercepção de saúde bucal. Método: Os dados analisados foram obtidos por meio de questionário de autopreenchimento de 3253 funcionários técnicos administrativos da Universidade Estadual do Rio de Janeiro um Estudo do Pró-Saúde. O estresse no trabalho foi medido através de um questionário elaborado por Karasek 1970 e reduzido por Theorell 1988. O instrumento é composto pelas seguintes dimensões: alta exigência no trabalho (alta demanda e baixo controle), baixa exigência (baixa demanda e alto controle), trabalho ativo (altos níveis de demanda e controle) e passivo (baixos níveis de demanda e controle). Autopercepção de saúde bucal foi obtida pela pergunta: “De um modo geral, como você considera o seu estado de saúde bucal (dentes e gengiva)?”, com opções de resposta variando entre, “muito bom” e “muito ruim”. Para a análise dos dados utilizou-se regressão logística ordinal, posteriormente ajustada para três blocos de variáveis: 1) saúde bucal (perda de dentes e dor de dentes nas duas últimas semanas) e uso e utilização serviço de saúde (frequência de visita ao dentista) 2) sociodemográficas (idade, sexo, escolaridade e renda) e 3) comportamentais em saúde (fumo e autopercepção de saúde geral). Resultados: Trabalhadores expostos à alta exigência e pouco controle no trabalho (OR=1,67; IC95%: 1,38-2,03) e ao trabalho passivo (OR=1,31; IC95%: 1,12-1,54), tiveram maiores chances de perceber pior saúde bucal, quando comparados àqueles expostos a baixa exigência no trabalho, não se observando associação com aqueles expostos ao trabalho ativo (OR=1,05; IC95%: 0,90-1,23). Entretanto, no modelo de regressão múltipla estas estimativas reduziram em magnitude e perderam significância estatística, a saber: alta exigência (OR=1,19; IC95%: 0,95-1,49), trabalho passivo (OR=1,09; IC95%: 0,91-1,31). Conclusão: Funcionários expostos a alta exigência no trabalho apresentaram pior saúde bucal autorreferida (modelo bruto e ajustado para os três blocos de variáveis) que parece ser parcialmente explicada pelas comportamentais em saúde, presença de problemas de saúde bucal (dor e perda dentária) e uso de serviços odontológicos com uma frequência maior do que uma vez ao ano. / Objective: To investigate the association between occupational stress and oral health self-perception. Method: Data obtained through a self-completion questionnaire with 3253 administrative technicians from a university in Rio de Janeiro, in the Pro-Health Study, were analyzed. Occupational stress was measured through a questionnaire prepared by Karasek, 1970, and reduced by Theorell, 1988. Oral health self-perception was obtained through the question: “In general, how do you consider your oral health state (teeth and gums)?”, with answer options ranging from “very good” to “very bad”. For data analysis, ordinal logistic regression was used, subsequently adjusted to three blocks of variables: 1) oral health (loss of teeth and toothache in the past two weeks) and use of the health service (frequency at which the dentist is attended); 2) socio-demographic (age, sex, schooling, and income); and 3) health-related behavior (smoking and general health self-perception). Results: Workers exposed to high strain and little control at work (OR=1.67; 95%CI: 1.38-2.03) and to passive work (OR=1.31; 95%CI: 1.12-1.54) had greater chances of perceiving worse oral health, when compared with those exposed to high-strain work, and no association was observed with those exposed to active work (OR=1.05; 95%CI: 0.90-1.23). However, in the multiple regression model, these estimates declined in magnitude and lost statistical significance, namely: high strain (OR=1.19; 95%CI: 0.95-1.49), passive work (OR=1.09; 95%CI: 0.91-1.31). Conclusion: Workers exposed to high-strain work presented worse self-reported oral health (raw model and adjusted to the three blocks of variables), which seems to be partially explained by health-related behavior, presence of oral health problems (toothache and dental loss), and use of dental services at greater frequency than once a year.

Objetivo: investigar a associação entre estresse no trabalho e a autopercepção de saúde bucal. Método: Os dados analisados foram obtidos por meio de questionário de autopreenchimento de 3253 funcionários técnicos administrativos da Universidade Estadual do Rio de Janeiro um Estudo do Pró-Saúde. O estresse no trabalho foi medido através de um questionário elaborado por Karasek 1970 e reduzido por Theorell 1988. O instrumento é composto pelas seguintes dimensões: alta exigência no trabalho (alta demanda e baixo controle), baixa exigência (baixa demanda e alto controle), trabalho ativo (altos níveis de demanda e controle) e passivo (baixos níveis de demanda e controle). Autopercepção de saúde bucal foi obtida pela pergunta: “De um modo geral, como você considera o seu estado de saúde bucal (dentes e gengiva)?”, com opções de resposta variando entre, “muito bom” e “muito ruim”. Para a análise dos dados utilizou-se regressão logística ordinal, posteriormente ajustada para três blocos de variáveis: 1) saúde bucal (perda de dentes e dor de dentes nas duas últimas semanas) e uso e utilização serviço de saúde (frequência de visita ao dentista) 2) sociodemográficas (idade, sexo, escolaridade e renda) e 3) comportamentais em saúde (fumo e autopercepção de saúde geral). Resultados: Trabalhadores expostos à alta exigência e pouco controle no trabalho (OR=1,67; IC95%: 1,38-2,03) e ao trabalho passivo (OR=1,31; IC95%: 1,12-1,54), tiveram maiores chances de perceber pior saúde bucal, quando comparados àqueles expostos a baixa exigência no trabalho, não se observando associação com aqueles expostos ao trabalho ativo (OR=1,05; IC95%: 0,90-1,23). Entretanto, no modelo de regressão múltipla estas estimativas reduziram em magnitude e perderam significância estatística, a saber: alta exigência (OR=1,19; IC95%: 0,95-1,49), trabalho passivo (OR=1,09; IC95%: 0,91-1,31). Conclusão: Funcionários expostos a alta exigência no trabalho apresentaram pior saúde bucal autorreferida (modelo bruto e ajustado para os três blocos de variáveis) que parece ser parcialmente explicada pelas comportamentais em saúde, presença de problemas de saúde bucal (dor e perda dentária) e uso de serviços odontológicos com uma frequência maior do que uma vez ao ano. / Objective: To investigate the association between occupational stress and oral health self-perception. Method: Data obtained through a self-completion questionnaire with 3253 administrative technicians from a university in Rio de Janeiro, in the Pro-Health Study, were analyzed. Occupational stress was measured through a questionnaire prepared by Karasek, 1970, and reduced by Theorell, 1988. Oral health self-perception was obtained through the question: “In general, how do you consider your oral health state (teeth and gums)?”, with answer options ranging from “very good” to “very bad”. For data analysis, ordinal logistic regression was used, subsequently adjusted to three blocks of variables: 1) oral health (loss of teeth and toothache in the past two weeks) and use of the health service (frequency at which the dentist is attended); 2) socio-demographic (age, sex, schooling, and income); and 3) health-related behavior (smoking and general health self-perception). Results: Workers exposed to high strain and little control at work (OR=1.67; 95%CI: 1.38-2.03) and to passive work (OR=1.31; 95%CI: 1.12-1.54) had greater chances of perceiving worse oral health, when compared with those exposed to high-strain work, and no association was observed with those exposed to active work (OR=1.05; 95%CI: 0.90-1.23). However, in the multiple regression model, these estimates declined in magnitude and lost statistical significance, namely: high strain (OR=1.19; 95%CI: 0.95-1.49), passive work (OR=1.09; 95%CI: 0.91-1.31). Conclusion: Workers exposed to high-strain work presented worse self-reported oral health (raw model and adjusted to the three blocks of variables), which seems to be partially explained by health-related behavior, presence of oral health problems (toothache and dental loss), and use of dental services at greater frequency than once a year.

The project elaborated in frame of engineering studies branch M-STG describe characteristics of plasticity of non-anneal materials E 235, E 190 and E 220. Materials characteristic was receive by static and dynamical tests. Based on the literature study it was conducted survey of the current state of experimental techniques for high-speed deformation. The materials were designed by Holomon approximation of rigid-plastic material model without hardening. It was conducted force analyses for machine Unison MG 2790 for rewind bending and bend with compressive force considering the identified material model. It was describe the impact passive and active forces to move the neutral axis.

The majority of research on high strain-rate effects in timber structures has been limited to the study of the load-bearing members in isolation. Limited work has been conducted on timber connections and full-scale timber assemblies under blast loading, and these have generally been constrained to qualitative observations. In North America, the increasing prevalence of mid- and high-rise timber structures makes them susceptible to blast effects. In addition, questions remain on how to design and optimize these timber assemblies, including the connections, against blast loads, due in part to the limitations on comprehensive design provisions. The effects of far-field blast explosions were simulated using the University of Ottawa shock tube. A total of fifty-eight dynamic tests were conducted on connection-level and full-scale specimens. The research program aimed to investigate the behaviour of heavy-timber connections when subjected to simulated blast loads. The experimental results showed that connections with a main failure mechanism consisting of wood crushing experienced significant increases in dynamic peak load when compared to the static peak load. In contrast, connections where steel yielding and rupturing occurred experienced no statistically significant increase in dynamic peak load. Full-scale glulam specimens with bolted connections designed to yield via wood crushing and bolt bending performed better than those with overdesigned connections. Bolted connections which failed in splitting led to premature failure of the glulam assembly. Reinforcement with self-tapping screws allowed these bolted joints to fail in a combination of bolt yielding and wood crushing, and provided more ductility when compared to unreinforced specimens. Specially designed energy-absorbing connections significantly increased the energy dissipation capabilities of the timber assemblies. The basis of these connections was to allow for connection yielding while delaying failure of the wood member. This was achieved via elastoplastic connection behaviour, which effectively limited the load imparted onto the wood member. Based on the experimental results, limitations in the current Canadian blast provisions were highlighted and discussed. A two-degree-of-freedom blast analysis software was developed and validated using full-scale and connection-level experimental results and was found to adequately capture the system response with reasonable accuracy. Sensitivity analyses regarding the applicability of using single-degree-of-freedom analysis were presented and discussed.

This work presents the design and construction of a self-deployable, self-stiffening,and retractable (SDSR) space array from carbon fiber reinforced polymers (CFRP’s) and a working prototype is demonstrated. The effort required developing principles for the design of high-strain composite flexural joints and their integration into angled composite panels. Designing LET arrays in angled panels is explored. Analysis of simple composite LET joints is presented for two degrees of freedom. Validation of the composite LET modeling is sought through numerical methods and empirical testing. Testing of several composite LET joint specimens is conducted and the results are reported. Results indicate that (while not as compact as their isotropic material counterparts) composite laminates can successfully use LET joints as surrogate folds.

This work analyzes the design and implementation of waveguides used to measure stress waves in solid mechanics via explicit finite element analysis and experimentation. Many areas of physics use waveguides where control of timing, location, or frequency of waves is imperative to functionality of a system. Split Hopkinson pressure bars (Kolsky bars) traditionally utilize straight waveguides during testing. Prior research produced the first bent wave guide for use in such an application, the coaxially embedded serpentine bar (CESB). Explicit finite element analysis (FEA) provides a modeling approach to understand the effects of pass and joint geometry and boundary conditions on the functionality of solid-mechanic waveguides like the CESB. FEA and experimentation also contrasts the functionality of welded joints and threaded joints. Novel waveguide designs that do not feature tubes are also detailed for use in dynamic mechanical testing and dynamic hardness indentation experiments. These designs feature acoustic lengths up to two orders of magnitude greater than their physical lengths.

The object of this study was to investigate the micro-structural response of DP 600 subjected to high strain rate, ballistic impact tests. The ballistic tests were conducted using normal impact of a hardened steel penetrator into a 2 mm thick sheet of DP 600. The average strain rates produced from this test method are on the order of 10^5 s-1. Multiple methods were used to investigate the micro-structure before and after high strain rate deformation including optical microscopy, electron microscopy, and X-ray diffraction. A large variation in material response was observed between tests conducted at 0.8 x 10^5 and 2.5 x 10^5 s-1.

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No description available.