Deformation behaviour of a commercial pure titanium alloy during hot compression testing

The flow curve behaviour and microstructure evolution of commercially pure titanium (CP-Ti) through uniaxial hot compression was investigated at 850 °C and a strain rate of 0.1/s. Electron back scattered diffraction (EBSD) was employed to characterize the microstructure and crystallographic texture development for different thermomechanical conditions. The stress-strain curves of CP-Ti alloy under hot compression displayed a typical flow behaviour of metals undergoing dynamic recrystallization (DRX), which resulted in grain refinement. The critical strain for the onset of DRX was 0.13 using the double differentiation analysis technique. It was also revealed that the texture was markably altered during hot deformation. © (2014) Trans Tech Publications, Switzerland.

Virtual and physical prototyping for compression sportswear

For high end compression sportswear it has increasingly become a crowded and highly competitive market with almost all sportswear companies having some form of offering. This work done in conjunction with a multinational sportswear group explores the use of virtual (FEA) and physical prototyping for a new garment design to ensure a competitive product in the market place. It was found that using a variety of processes, validation and feedback was given at several stages of the development program and highlighted areas of concern well before a final product was developed.

Evaluation of FRP concrete compression member under repeated load and harsh environment

Strengthening and rehabilitation have been increasingly applied in many structures to improve their capacity and serviceability. Fiber Reinforced Polymer (FRP) materials are universally known for their ability to improve the load capacity of damaged structural elements because of their high linear-elastic behavior. However, enhancing the capacity of structural elements that are exposed to repeated load coupled with harsh environment is an area that requires further investigation. This research focused on experimental analysis of the behavior and response of confined and unconfined concrete compression members (300mm x 150mm) under repeated load while exposed to 1440 cycles of seawater splash zone in United Arab Emirates (UAE). Confining concrete compression members with Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) sheets have increased the load capacity compared to the control sample at room temperature by 110% and 84%, respectively. Results showed that the average value of compressive strength for the confined concrete exposed to sea water splash zone conditions for CFRP and GFRP specimens has decreased by 33% and 23%, respectively, compared to the confined concrete in the room temperature. However, GFRP specimens showed higher performance in compressive strength under sea water splash zone than those of the CFRP specimens. Different mode of failures such as delamination, de-bonding and combination of such modes were observed and related to various exposure factors and mechanical properties.

Investigation of precipitate hardening of slip and twinning in Mg5%Zn by micropillar compression

A Mg-5%Zn alloy has been aged to form c-axis rod precipitates which are known to increase strength. Micropillar compression tests were carried out in the precipitate-free and aged samples to investigate the effects of these precipitates on twinning and slip in magnesium alloys. Basal slip, pyramidal slip and {101¯2} twinning were selectively activated by compressing micropillars in the [112¯3], [0 0 0 1] and [112¯0] orientations, respectively. It has been found that precipitation causes moderate hardening of the basal slip system, and also significantly increases the work hardening rate. The compression of [112¯0] initiated twinning, but the present experiments were dominated by twin nucleation, rather than growth. It was found that the effect of precipitation on twin nucleation was negligible. Precipitation had little effect on specimens compressed in the c-axis.

Strain gradients in Cu-Fe thin films and multilayers during micropillar compression

Plastic strain gradients can influence the work-hardening behaviour of metals due to the accumulation of geometrically necessary discolations at the micron/submicron scale. A finite element model based on the conventional theory of mechanism-based strain-gradient plasticity has been developed to simulate the micropillar compression of Cu–Fe thin films and multilayers. The modelling results show that the geometric constraints lead to inhomogeneous deformation in the Cu layers, which agrees well with the bulging of Cu layers observed experimentally. Plastic strain gradients develop inside the individual layers, leading to extra work-hardening due to the accumulation of geometrically necessary dislocations. In the multilayer specimens, the Cu layers deform more severely than the Fe layers, resulting in the development of tensile stresses in the Fe layers. It is proposed that these tensile stresses are responsible for the development of micro-cracks in the Fe layers.

Orientation dependence of the deformation microstructure in a Fe-30Ni-Nb model austenitic steel subjected to hot uniaxial compression

The present work was aimed at a detailed investigation of the orientation dependence of the microstructure characteristics in a Fe-30Ni-Nb austenitic model steel subjected to hot uniaxial compression at 1198 K (925 °C) at a strain rate of 1 s−1 to several strain levels up to 1.0. The quantification of the substructure evolution as a function of strain was performed for the stable 〈011〉 oriented grains. Other grain orientations were also investigated in detail at a strain of 0.2. The 〈110〉 oriented grains contained self-screening arrays of “microbands” (MBs) aligned with high Schmid factor {111} slip planes. The MB crystallographic alignment was largely maintained up to a strain of 1.0, which suggests that the corresponding boundaries kept continuously rearranging themselves during straining and did not follow the sample shape change. The mean MB spacing decreased and misorientation angle increased with strain towards saturation, indicating the operation of the “repolygonization” dynamic recovery mechanism. The non-〈011〉 oriented grains displayed a strong tendency to split during deformation into deformation bands having alternating orientations and being mutually rotated by large angles. The bands were separated by transition regions comprising arrays of closely spaced, extended sub-boundaries collectively accommodating large misorientations across very small distances.

Endogenous wage compression and aggregation boundaries in a model of hierarchical human capital

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Bias and size effects of price-comparison search engines : theory and experimental evidence

We analyze the impact on consumer prices of the size and bias of price comparison search engines. In the context of a model related to Burdett and Judd (1983) and Varian (1980), we develop and test experimentally several theoretical predictions. The experimental results confirm the model’s predictions regarding the impact of the number of firms, and the type of bias of the search engine, but reject the model’s predictions regarding changes in the size of the index. The explanatory power of an econometric model for the price distributions is significantly improved when variables accounting for risk attitudes are introduced.

Determination of ecological efficiency in internal combustion engines: The use of biodiesel

This paper evaluates and quantifies the environmental impact from the use of some renewable fuels and fossils fuels in internal combustion engines. The following fuels are evaluated: gasoline blended with anhydrous ethyl alcohol (anhydrous ethanol), conventional diesel fuel, biodiesel in pure form and blended with diesel fuel, and natural gas. For the case of biodiesel, its complete life cycle and the closed carbon cycle (photosynthesis) were considered. The ecological efficiency concept depends on the environmental impact caused by CO(2), SO(2), NO(x) and particulate material (PM) emissions. The exhaust gases from internal combustion engines, in the case of the gasoline (blended with alcohol), biodiesel and biodiesel blended with conventional diesel, are the less polluting; on the other hand, the most polluting are those related to conventional diesel. They can cause serious problems to the environment because of their dangerous components for the human, animal and vegetable life. The resultant pollution of each one of the mentioned fuels are analyzed, considering separately CO(2), SO(2), NO(x) and particulate material (PM) emissions. As conclusion, it is possible to calculate an environmental factor that represents, qualitatively and quantitative, the emissions in internal combustion engines that are mostly used in urban transport. Biodiesel in pure form (B100) and blended with conventional diesel as fuel for engines pollute less than conventional diesel fuel. The ecological efficiency for pure biodiesel (B100) is 86.75%: for biodiesel blended with conventional diesel fuel (B20, 20% biodiesel and 80% diesel), it is 78.79%. Finally, the ecological efficiency for conventional diesel, when used in engines, is 77.34%; for gasoline, it is 82.52%, and for natural gas, it is 91.95%. All these figures considered a thermal efficiency of 30% for the internal combustion engine. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.

Preconcentration and determination of metal ions in commercial ethanol used as fuel for automotive engines

The present investigation reports the synthesis, characterization, and adsorption properties of a new nanomaterial based on organomodified silsesquioxane nanocages. The adsorption isotherms for CuCl,, CoCl2, ZnCl2, NiCl2, and FeCl3 from ethanol solutions were performed by using the batchwise method. The equilibrium condition is reached very quickly (3 min), indicating that the adsorption sites are well exposed. The results obtained in the flow experiments, showed a recovery of ca. 100% of the metal ions adsorbed in a column packed with 2 g of the nanomaterial, using 5 mL of 1.0 mol L-1 HCl solution as eluent. The sorption-desorption of the metal ions made possible the development of a method for preconcentration and determination of metal ions at trace level in commercial ethanol, used as fuel for car engines. The values determined by recommended method for plants 1, 2, and 3 indicated an amount of copper of 51, 60, and 78 mu g L-1, and of iron of 2, 15, and 13 mu g L-1, respectively. These values are very close to those determined by conventional analytical methods. Thus, these similar values demonstrated the accuracy of the determination by recommended method.

Extrinsic compression of popliteal artery in asymptomatic athlete and non-athlete individuals - A comparative study using duplex scan (color duplex sonography)

Aim. Extrinsic compression of the popliteal artery and absence of surrounding anatomical abnormalities characterize the functional popliteal artery entrapment syndrome (PAES). The diagnosis is confirmed to individuals who have typical symptoms of popliteal entrapment and occlusion or important stenosis of the popliteal artery with color duplex sonography (CDS), magnetic resonance imaging (MRI) or arteriography during active plantar flexion-extension maneuvers. However, variable result findings in normal asymptomatic subjects have raised doubts as to the validity of these tests. The purpose of this study was to compare the frequency of popliteal artery compression in 2 groups of asymptomatic subjects, athletes and non-athletes.Methods. Forty-two individuals were studied. Twenty-one subjects were indoor soccer players, and 21 were sedentary individuals. Physical activity was evaluated through questionnaires, anthropometric measurements, and cardiopulmonary exercise test. Evaluation of popliteal artery compression was performed in lower limbs with CDS, ankle-brachial index (ABI) measurements and continuous wave Doppler of the posterior tibial artery.Results. The athletes studied fulfilled the criteria of high level of physical activity whereas sedentary subjects met the criteria of low level of activity. Popliteal artery compression was observed with CDS in 6 (14.2%) studied subjects; 2 of whom (4.7%) were athletes and 4 (9.5%) were non-athletes. This difference was not statistically significant (p=0.21). Doppler of the tibial arteries and ABI measurements gave good specificity and sensibility in the identification of popliteal artery compression.Conclusion. The frequency of popliteal artery compression during maneuvers in normal subjects was 14.2% irrespective of whether or not they performed regular physical activities. Both Doppler and ABI showed good agreement with CDS and should be considered in screening popliteal arteries in individuals suspected of PAES.

Histomorphometric evaluation of periodontal compression and tension sides during orthodontic tooth movement in rats

OBJECTIVE: The purpose of this study was to evaluate the thickness of the periodontal ligament of rat molars during orthodontic tooth movement (OTM). METHODS: Thirty Wistar rats were divided into three groups of 10 animals each: GI, GII and GIII and the mice were euthanized at 7, 14 and 21 days, respectively. Experimental subjects were compared to their respective controls by the Mann-Whitney test. Comparison of values between compression and tension sides were performed during the same and different time periods through Analysis of Variance (ANOVA), Kruskal-Wallis test and, subsequently, Tukey's test. RESULTS: Groups GI and GII showed decreased PDL size in the apical regions of the mesiobuccal root and in the cervical region of the distobuccal root. There was also an increased PDL in the cervical regions of the mesiobuccal root, apical region of the distobuccal root and middle region of both roots. CONCLUSION: The reduction and increase in PDL size were seen in the same root, which characterizes tooth inclination. The apical, middle and cervical regions were compared with one another in each time period and at three times: 7, 14 and 21 days. They were also compared in each region, confirming a tipping movement in GI and GII and a gradual decreased intensity between GI to GII, reaching normal dimension in GIII.

Effect of compression load and temperature on thermomechanical tests for gutta-percha and Resilon (R)

Tanomaru-Filho M, Silveira GF, Reis JMSN, Bonetti-Filho I, Guerreiro-Tanomaru JM. Effect of compression load and temperature on thermomechanical tests for gutta-percha and Resilon (R). International Endodontic Journal, 44, 1019-1023, 2011.Aim To analyse a method used to evaluate the thermomechanical properties of gutta-percha and Resilon at different temperatures and compression loads.Methodology Two hundred and seventy specimens measuring 10 mm in diameter and 1.5 mm in height were made from the following materials: conventional gutta-percha (GCO). thermoplastic gutta-percha (GTP) and Resilon (R) cones (RE). After 24 h, the specimens were placed in water at 50 degrees C. 60 degrees C or 70 degrees C for 60 s. After that, specimens were placed between two glass slabs, and loads weighing 1.0, 3.0 or 5.0 kg were applied. Images of the specimens were digitized before and after the test and analysed using imaging software to determine their initial and final areas. The thermomechanical property of each material was determined by the difference between the initial and final areas of the specimens. Data were subjected to ANOVA and SNK tests at 5% significance. To verify a possible correlation between the results of the materials, linear regression coefficients (r) were calculated.Results Data showed higher flow area values for RE under all compression loads at 70 degrees C and under the 5.0 kg load at 60 degrees C (P < 0.05). Regarding gutta-percha, GTP showed higher flow under loads weighing 3.0 and 5.0 kg. at 60 and 70 degrees C (P < 0.05). GCO presented higher flow at 70 degrees C with a load of 5.0 kg. Regression analyses showed a poor linear correlation amongst the results of the materials under the different experimental conditions.Conclusion Gutta-percha and Resilon (R) cones require different compression loads and temperatures for evaluation of their thermomechanical properties. For all materials, the greatest flow occurred at 70 degrees C under a load of 5.0 kg: therefore. these parameters may be adopted when evaluating endodontic tilling materials.

Influence of compression forces on tablets disintegration by AC Biosusceptometry

Analysis of physical phenomena that occurs during tablet disintegration has been studied by several experimental approaches; however none of them satisfactorily describe this process. The aim of this study was to investigate the influence of compression force on the tablets by associating the AC Biosusceptometry with consolidated methods in order to validate the biomagnetic technique as a tool for quality control in pharmaceutical processes.Tablets obtained at five compression levels were submitted to mechanical properties tests. For uncoated tablets, water uptake and disintegration force measurements were performed in order to compare with magnetic data. For coated tablets, magnetic measurements were carried out to establish a relationship between physical parameters of the disintegration process. According to the results, differences between the compression levels were found for water uptake, force development and magnetic area variation measurements. ACB method was able to estimate the disintegration properties as well as the kinetics of disintegration process for uncoated and coated tablets. This study provided a new approach for in vitro investigation and validated this biomagnetic technique as a tool for quality control for pharmaceutical industry. Moreover, using ACB will also be possible to test these parameters in humans allowing to establish an in vitro/in vivo correlation (IVIVC). (C) 2007 Elsevier B.V. All rights reserved.