Application of compression test in analysis of mechanical and color changes in grapefruit juice powder as related to glass transition and water activity

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Aplicação de danos mecânicos em abacates e seus efeitos na qualidade dos frutos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comportamento de adesão da madeira de um híbrido clonal de Eucalyptus urophylla x Eucalyptus grandis proveniente de três condições de manejo

This study aimed to evaluate the adhesion ability of eucalyptus lumber from three tillage systems, using adhesives: resorcinol formaldehyde and two adhesives in water emulsion based on vinyl poly-acetate. The management systems were characterized by three strata, the stratum one (E1) characterized by wood from coppice and 70 months of age, the stratum two (E2) characterized by wood and retirement age of 166 months and stratum three (E3), also characterized by retirement at 70 months of age. The wood was derived from a random mixture of the first two sawn logs, each three feet from the base, which comprised three treatments on the adhesive used. We evaluated the shear strength by compression tests and the percentage of wood failure in the glue line. Based on the results obtained, it can be said that the adhesion had satisfactory performance with all the resins used, and the average values of shear strength of the glue line were shown to be equivalent to the shear strength of solid wood only for the samples which adhered with 'Wonderbond' adhesive and also provide higher values for wood failure (97.64%). The highest density present in the wood of the second stratum (E2) influenced only sticking with the resorcinol formaldehyde resin. For polyvinyl acetate (Cascorez 2590), shear values decreased in the third management condition (E3).

Determinação do módulo de elasticidade da madeira juvenil e adulta de Pinus taeda por ultra-som

A madeira de Pinus sp. tem utilização crescente na indústria madeireira brasileira. O decréscimo constante do suprimento de árvores adultas com grandes diâmetros, provenientes de florestas naturais, tornou comum a produção de madeira em ciclos curtos, com grande proporção de madeira juvenil. Resultados de diversas pesquisas têm reportado que o módulo de elasticidade e a resistência a diferentes solicitações mecânicas são seriamente afetados pela presença de madeira juvenil. Este trabalho teve por objetivo determinar o módulo de elasticidade da madeira juvenil e adulta de Pinus taeda L. a partir da constante dinâmica C LL, obtida em ensaios não-destrutivos de ultra-som. A madeira de P. taeda era originária de plantios da Estação Experimental de Itapeva - SP, sendo amostrados seis indivíduos arbóreos com 34 anos de idade. Os corpos-de-prova (4 cm x 4 cm x 45 cm) foram obtidos separadamente das regiões de madeira juvenil e adulta da prancha central, previamente submetida à secagem industrial (umidade final de 12%), para a determinação da constante dinâmica por meio de ensaios de ultra-som. Para avaliar a sensibilidade do método do ultra-som, os corpos-de-prova foram ensaiados destrutivamente à compressão paralela. Os resultados mostraram boa sensibilidade do método do ultra-som (R² » 0,90) na avaliação desse parâmetro mecânico da madeira juvenil e adulta.

Elastic properties of hygrothermally conditioned glare laminate

The influences of hygrothermal conditioning on mechanical properties of a fiber/metal laminate (FML) have been investigated by tensile and compression tests. The environmental action, such as high moisture concentration, high temperatures, corrosive fluids or ultraviolet radiation (UV), can affect the performance of advanced composites during service. In the present work, the results show that for the glass fiber/epoxy composites tensile and compression values decrease after hygrothermal conditioning. However, no changes on mechanical properties (tensile and compression strength) are observed for the Glare laminate, regardless the hygrothermal conditioning. (C) 2006 Elsevier Ltd. All rights reserved.

O Zoledronato no tratamento da osteoporose umeral em ratas: estudo prospectivo e randomizado

OBJETIVO: Investigar as repercussões clínicas, biomecânicas e histomorfométricas do zoledronato no tratamento da osteoporose umeral em ratas osteoporóticas. MÉTODOS: Analisou-se, prospectivamente, 40 ratas (Rattus novergicus albinus). Com 60 dias de vida, foram aleatorizadas em dois grupos de acordo com o procedimento cirúrgico: ooforectomia bilateral (O) (n=20) e pseudo-cirurgia (P) (n=20). Após trinta dias, os animais foram novamente randomizados, de acordo com a administração de 0,1mg/kg de zoledronato (AZ) ou água destilada (AD): OAZ (n=10), OAD (n=10), PAZ (n=10) e PAD (n=10). Após doze meses, os animais foram eutanasiados e seus úmeros retirados. Clinicamente considerou-se o peso dos animais; biomecanicamente foram realizados ensaios compressivos e histomorfometricamente foi determinada a área trabecular óssea. RESULTADOS: Os grupos O tiveram um aumento de peso maior que os grupos P (p=0,005). Os grupos com zoledronato suportaram maior carga máxima que os grupos com água destilada (p=0,02). Nos grupos com zoledronato verificou-se o aumento da área trabecular óssea quando comparados aos grupos com água destilada (p=0,001). Houve correlação positiva entre a área trabecular e a carga máxima (p=0,04; r=0,95). CONCLUSÃO: O zoledronato não influiu no peso dos animais. Os resultados mostraram o aumento da resistência óssea umeral e da área trabecular óssea.

Efeitos do treinamento físico sobre a resistência mecânica do terço proximal do fêmur de ratos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Porous titanium for biomedical applications: An experimental study on rabbits

Objective: The aim of this study was to carry out an in vivo assessment of bone ingrowth in two different types of porous titanium -the first being completely porous, and the second with a porous surface and dense nucleus, manufactured by powder metallurgy- and to evaluate their mechanical properties. Study design: Ten scaffolds from each group were submitted to metallographic analysis and compression tests. Next, two scaffolds of each type were inserted into 14 rabbits, which were sacrificed 8 weeks after surgery. The samples were submitted for histological examination. Results: Metallographic analysis revealed interconnected pores, and the average interconnected pore diameter was about 360 mm, with 36% total porosity. The totally porous titanium samples and the titanium samples with porous surface and dense nucleus showed an average compressive strength of 16.19 MPa and 69.27 MPa, respectively. After 8 weeks, the animals showed bone ingrowth, even into the most internal pores. Conclusions: The pore morphology was effective in permitting bone ingrowth in both groups. Titanium scaffolds with a porous surface and dense nucleus showed the best mechanical properties and most adequate interface.

Effect of Ag addition on the martensitic phase of the Cu-10 wt.% Al alloy

Thermal analysis and compression tests at room temperature have been carried out for Cu-10 wt.% Al and Cu-10 wt.% Al-10 wt.% Ag alloys samples. The results indicate that the decomposition reaction of the (beta(1)) parent phase is decreased suppressed and a martensite stabilization effect can be induced by Ag addition. The Cu-Al-Ag alloy shows some degree of shape memory capacity. (C) 2007 Elsevier B.V. All rights reserved.

Liofilização de fatias de abacaxi: avaliação da cinética de secagem e da qualidade do produto

O objetivo deste trabalho foi avaliar a cinética de secagem e os parâmetros de qualidade - conteúdo de vitamina C, reidratação e textura - de fatias de abacaxi liofilizadas em função da espessura e da temperatura de congelamento. Abacaxis do tipo Havaí, variedade Smooth Cayenne, foram fatiados transversalmente em espessuras de 0,5, 1,0 e 1,5 cm. As fatias foram congeladas nas temperaturas de -14, -24 e -34 °C, sendo, em seguida, conduzidas ao liofilizador. Uma parcela das amostras era destinada ao estudo da cinética de secagem pela pesagem periódica das mesmas, enquanto outra foi reservada para os testes de qualidade. O teor de vitamina C foi quantificado por adição de ácido oxálico na amostra e titulado com 2,6-diclorofenolindofenol. O parâmetro de textura avaliado foi a dureza, por testes de compressão em texturômetro, enquanto a reidratação foi obtida pela pesagem das amostras antes e após a imersão em água destilada por 5 min. Os resultados do presente trabalho mostraram que existe uma forte dependência da cinética de secagem e dos atributos de qualidade de fatias de abacaxi liofilizadas em função das condições utilizadas durante a etapa de congelamento, mesmo sendo este classificado como congelamento lento. Por outro lado, a taxa de congelamento não é a única variável que tem influência sobre a cinética de secagem e os atributos de qualidade. A combinação de temperatura e umidade, tanto durante a liofilização propriamente dita, quanto durante a etapa de reidratação, tem influência sobre a transição vítrea do material que, por sua vez, afeta a extensão do colapso estrutural sofrido pelo produto.

Influence of different drying methods on tbe rheological properties of raisins

The rheological parameters of raisins were obtained after three different drying methods: convective, osmo-convective and solar drying. Compression tests were applied to rehydrated samples by using a Texture Analyzer TAXT2i. A mathematical trick was used to determine the stress and area was calculated along the deformation. A power law model could adequately fit stress-true strain curves and parameters; K (measure of stiffness) and n (solid behavior index) were obtained as a function of water activity between 0.755 to 0.432. Results showed that these parameters were strongly dependent on water activity for all drying methods. The constant K, which indicates the resistance against deformation, increased with decreasing water activity. on the other hand, increasing water activity resulted in higher solid behavior indexes, showing a large deviation from the Hookean behavior.

Influence of hygrothermal conditioning on the elastic properties of carall laminates

The influence of hygrothermal conditioning on mechanical properties of Carall laminates have been investigated by tensile and compression tests. The environmental factors can limit the applications of composites by deteriorating the mechanical properties during service. The importance of temperature at the time of conditioning plays an important role in environmental degradation of such composite materials. In this work, the results show that for carbon fiber/epoxy composites tensile and compression values decrease after hygrothermal conditioning. However, the changes on mechanical properties of Carall are negligible, regardless the hygrothermal conditioning.

Application of the modified Cam-Clay model to a residual soil

The modified Cam - Clay model was used to model experimental results of a saturated residual sandy soil from Sao Carlos - SP. Triaxial compression tests were performed using Bishop - Wesley cell with internal transducers to measure axial and radial strains. It was observed that the model fairly fitted experimental results, specially the principal stress difference at critical state. In general it was observed a good qualitative agreement between experimental and predicted strain values, considering compression or expansion of the samples. However, in all the stress path used, but 100 degrees and 140 degrees, the model yielded strains larger than that measured in the tests.

Hardness and compressive strength of indirect composite resins: effects of immersion in distilled water

The aim of this study was to evaluate the effect of ageing in distilled water on the hardness and compressive strength of a direct composite resin Z100, a feldspatic porcelain (Noritake) and three indirect composites (Artglass, Solidex and Targis). For the Vickers hardness tests, five disk-shaped specimens (2 x 4 mm) of each material were prepared according to the manufacturers' instructions. The hardness tests were conducted using a Vickers diamond indentor. Compressive strength measurements were recorded on cylindrical specimens with a diameter of 6 mm and a length of 12 mm. The compression tests were carried out with a constant cross-head speed of 0.5 mm min(-1) on a mechanical test machine. For each material, 10 specimens were tested after 7 days of dry storage at 37 +/- 1 degreesC and 10 specimens were tested after water storage at 37 +/- 1 degreesC for 180 days. Noritake porcelain specimens showed higher hardness values than the composites. Among the composite materials, Z100 promoted the highest VHN values, regardless of the ageing periods. The results showed that Solidex and Z100 had the highest compressive strength values. Ageing in water reduced the hardness for all composites, but had no long-term effect on the compressive strength.

Remarks on orthotropic elastic models applied to wood

Wood is generally considered an anisotropic material. In terms of engineering elastic models, wood is usually treated as an orthotropic material. This paper presents an analysis of two principal anisotropic elastic models that are usually applied to wood. The first one, the linear orthotropic model, where the material axes L (Longitudinal), R(radial) and T(tangential) are coincident with the Cartesian axes (x, y, z), is more accepted as wood elastic model. The other one, the cylindrical orthotropic model is more adequate of the growth caracteristics of wood but more mathematically complex to be adopted in practical terms. Specifically due to its importance in wood elastic parameters, this paper deals with the fiber orientation influence in these models through adequate transformation of coordinates. As a final result, some examples of the linear model, which show the variation of elastic moduli, i.e., Young's modulus and shear modulus, with fiber orientation are presented.