Estudo do comportamento mecânico e microestrutural de um aço maraging após soldagem a laser e tratamentos térmicos

Pós-graduação em Engenharia Mecânica - FEG

Efeito do fresamento com alta velocidade de corte na integridade superficial de aços ferríticos com grãos ultrafinos

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

Caracterização mecânica e microestrutural de um aço 4340 com estrutura multifásicas e tratamento de nitrocarbonetação a plasma

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Alloxan diabetes alters the tensile strength, morphological and morphometric parameters of abdominal wall healing in rats

PURPOSE:To investigate the effects of alloxan diabetes on the abdominal wall healing of rats undergoing laparotomy.METHODS:Ninety-six male Wistar rats weighing between 200 and 300 grams, divided into two groups: non-diabetic group (G1) and another with untreated diabetes (G2). Three months after diabetes induction, the animals underwent a 5cm-long- laparotomy and 5.0 nylon monofilament suture. After the surgery, 12 animals from each group were euthanized on days 4, 14, 21 and 30 corresponding to the moments M1, M2, M3 and M4. In each moment a fragment of the abdominal wall containing the scar was removed for tensile strength measurement, histological and morphometric study. Clinical and biochemical parameters were also analyzed.RESULTS:G2 animals showed parameters compatible with severe diabetes and decreased plasma levels of insulin. The tensile strength in G2 was significantly smaller in M2 and M4, with a tendency to fall in the other two. Through light microscope, diabetic animals showed more difficulty to increase collagen density and contraction. G2 animals showed high cellularity of fibroblasts in later healing moments, with collagen thinning in M2 and M4.CONCLUSION:The abdominal wound healing in untreated diabetic animals was altered and led to a higher incidence of dehiscence and infections.

Microstructural and electrochemical characterization of friction stir welded duplex stainless steels

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

MICROSTRUCTURAL CHARACTERIZATION OF DUAL AND MULTIPHASE STEELS APPLIED TO AUTOMOTIVE INDUSTRY

TRIP (Transformation Induced Plasticity) and DP (Dual-Phase) steels are written in a new series of steels which present excellent mechanical properties. As for microstructure aspect, TRIP steels consist on a ferrite matrix with a second phase dispersion of other constituents, such as bainite, martensite and retained austenite, while dual-phase steels consist on martensite dispersion in a ferrite matrix. In order to identify the different microconstituents present in these materials, microstructure characterization techniques by optical microscopy (using different etchants: LePera, Heat-Tinting and Nital) and scanning electron microscopy were carried out. This being so, microstructures were correlated with mechanical properties of materials, determined by means of tensile tests. It is concluded that steels assisted by TRIP effect have a strength and elongation relation higher than the dual-phase one. With microstructure characterization, it was observed phases present in these materials microstructure.

Efficacy of Surface Treatments on the Bond Strength of Resin Cements to Two Brands of Zirconia Ceramic

Purpose: To compare the shear bond strength (SBS) of two cements to two Y-TZP ceramics subjected to different surface treatments.Materials and Methods: Zirconia specimens were made from Lava (n = 36) and IPS e.max ZirCAD (n = 36), and their surfaces were treated as follows: no treatment (control), silica coating with 30-mu m silica-modified alumina (Al2O3) particles (CoJet Sand), or coating with liners Lava Ceram for Lava and Intensive ZirLiner for IPS e.max ZirCAD. Composite resin cylinders were bonded to zirconia with Panavia F or RelyX Unicem resin cements. All specimens were thermocycled (6000 cycles at 5 degrees C/55 degrees C) and subjected to SBS testing. Data were analyzed by post-hoc test Tamhane T2 and Scheffe tests (alpha = 0.05). Failure mode was analyzed by stereomicroscope and SEM.Results: With both zirconia brands, CoJet Sand showed significantly higher SBS values than control groups only when used with RelyX Unicem (p = 0.0001). Surface treatment with liners gave higher SBS than control groups with both ceramic brands and cements (p < 0.001). With both zirconia brands, the highest SBS values were obtained with the CoJet and RelyX Unicem combination (> 13.47 MPa). Panavia F cement showed significantly better results when coupled with liner surface treatment rather than with CoJet (p = 0.0001, SBS > 12.23 MPa). In untreated controls, Panavia F showed higher bond strength than RelyX Unicem; the difference was significant (p = 0.016) in IPS e.max ZirCAD. The nontreated specimens and those treated with CoJet Sand exhibited a high percentage of adhesive and mixed A (primarily adhesive) failures, while the specimens treated with liners presented an increase in mixed A and mixed C (primarily cohesive) failures as well as some cohesive failure in the bulk of Lava Ceram for both cements.Conclusion: CoJet Sand and liner application effectively improved the SBS between zirconia and luting cements. This study suggests that different interactions between surface treatments and luting cements yield different SBS: in clinical practice, these interactions should be considered when combining luting cements with surface treatments in order to obtain the maximum bond strength to zirconia restorations.

Evaluation of Resin Bond Strength to Yttria-stabilized Tetragonal Zirconia and Framework Marginal Fit: Comparison of Different Surface Conditionings

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

Zirconia-Porcelain Bonding: Effect of Multiple Firings on Microtensile Bond Strength

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

Influence of shot peening on the fatigue strength of Custom 465 stainless steel for aeronautic application

This project was originated from the national aircraft industry requirements to reduce the use of coated materials with electroplated chromium or cadmium that produce waste, which is harmful to health or the environment. The selected material is a Custom 465 stainless steel used in the aeronautical field due to its high mechanical strength. Considering the load sustained by the wheel axis of the landing gear, the Custom 465 is tested in axial fatigue. The objective is to compare the behavior of the Custom 465 with plated AISI 4340 steel coated with cadmium. X-ray diffraction method was used to determine the residual stress field induced by shot peening.

Estudo das propriedades mecânicas do aço SAE 1312 modificado ao nióbio

The study of mechanical properties of high-alloy special steels is of great interest of the steel industry due to the great demand by companies that manufacture automotive components of high criticality, and also because of its high commercial value. However, the development of this type of alloy metals demand highly technical knowledge. Among these extremely important kinds of steel, the subject which is the interest of this study is the special steel modified by niobium. The manganese and niobium are the main alloying elements in the composition of these steels, both of them increase the stability of the austenite region, however, manganese increases the hardenability and tensile yield strength, and niobium increases the mechanical strength and promotes refining the grain. The mechanical characterization of steel SAE 1312 modified the niobium was made in order to gain a better understanding of the influence on the mechanical properties caused by aging at different temperatures and for different reductions in the drawing of gauge material. This characterization was made by means of tensile test and hardness. This material showed an increase in yield strength and hardness when gauge with large reductions during the wiredrawing, but when subjected to aging temperatures higher than 300 ° C had a slight loss of these properties

Aços avançados de alta resistência: avaliação da microestrutura e propriedades dos aços DP 600 E DP 780

This work aims to study the Dual-Phase 600 and 780 steels, which are part of technology development project materials for the automotive industry. It is worth underscoring the antagonistic properties as the Dual-Phase steel assemble, high mechanical strength and elongation due its microstructure, ferrite and martensite. These properties are obtained by a intercritical heat treatment which facilitates the formation of a hardness metastable microstructure shaped plates of low carbon steels. The applicability of Dual Phase steel in the structure of vehicles is huge and its production is already on a commercial scale, so the study and development of this material implies lower cost in automobile manufacturing processes. The dual phase steels DP600 and DP780 underwent tensile, hardness and metallographic analysis to evaluate and comparing its properties. The results indicate that the DP780 steel has higher strength and hardness than the DP600 steel and its microstructure consists of martensite higher fraction which accounts for the higher resistance and hardness. However, the DP600 has higher conformability to DP780 steel

Handgrip strength as a predictor of bone mineral density in cirrhotic outpatients

Osteoporosis is well recognized as a cirrhosis complication; however, most studies assessing this condition included only patients on liver transplantation lists with an elevated rate of bone diseases. While general population studies show that handgrip strength is clearly associated with bone mineral density, until now this tool has not been applied to cirrhotic patients in relation to their bone condition. This study aimed to evaluate whether handgrip strength, bone and liver tests may be useful as predictors of bone disease in cirrhotic outpatients. 129 subjects were included (77 men and 52 women). Dual energy X-ray absorptiometry was applied to evaluate lumbar-spine and femoral-neck T scores. Osteoporosis/osteopenia rates were 26.3%/35.6% in the lumbar spine and 6.9%/41.8% in the femoral neck, respectively. Model selections were based on backward procedures to find the best predictors of low T scores. For lumbar spine, only low handgrip strength and high parathyroid hormone levels were clearly related to low T scores. For femoral neck, only age was associated with low T scores. Handgrip strength may serve as an effective predictor of low lumbar spine T score among cirrhotic outpatients. As cirrhosis affects the lumbar spine more than the femoral neck, these results suggest that handgrip strength should be tested in all cirrhotic patients as a first indicator of bone health. This article is protected by copyright. All rights reserved.

Short-term low-intensity blood flow restricted interval training improves both aerobic fitness and muscle strength

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The canonical correlation between the biological markers of performance and physical fitness in high level judo athletes

The objective of this research was to verify the relationship between biological markers of performance of elite judo athletes and performance in different physical fitness tests. Twenty-one judo athletes were involved in the present observational and correlational study. Dermatoglyphic variables and the 2D:4D digit ratio were considered as biological markers, while the physical fitness variables analyzed were body fat, maximal strength, muscular power, the aerobic and anaerobic profile, and performance in specific tests. The statistics involved canonical correlations and a multivariate technique. A high and significant canonical correlation was observed between groups of variables, the first expressed by 1=0.999 (p<0.0001) and the second by 2=0.997 (p<0.001). It appears that, beyond height and body mass, total ridge count, pattern intensity for fingers and 2D:4D had more canonical loading. The physical fitness component of the first canonical variable incorporated, with high intensity were: the sum of skinfold thickness, the bench press onerepetition maximum (1RM), upper and lower body aerobic power. In the second canonical variable, physical fitness was composed of the squat 1RM, suspension time on the bar, the SJFT-index, and mean power during the upper body Wingate test. The data of this investigation showed the interdependence between biological markers of performance and physical fitness in high level judo athletes.