Constitutive modeling of shape memory alloy wire with non-local rate kinetics

A constitutive modeling approach for shape memory alloy (SMA) wire by taking into account the microstructural phase inhomogeneity and the associated solid-solid phase transformation kinetics is reported in this paper. The approach is applicable to general thermomechanical loading. Characterization of various scales in the non-local rate sensitive kinetics is the main focus of this paper. Design of SMA materials and actuators not only involve an optimal exploitation of the hysteresis loops during loading-unloading, but also accounts for fatigue and training cycle identifications. For a successful design of SMA integrated actuator systems, it is essential to include the microstructural inhomogeneity effects and the loading rate dependence of the martensitic evolution, since these factors play predominant role in fatigue. In the proposed formulation, the evolution of new phase is assumed according to Weibull distribution. Fourier transformation and finite difference methods are applied to arrive at the analytical form of two important scaling parameters. The ratio of these scaling parameters is of the order of 10(6) for stress-free temperature-induced transformation and 10(4) for stress-induced transformation. These scaling parameters are used in order to study the effect of microstructural variation on the thermo-mechanical force and interface driving force. It is observed that the interface driving force is significant during the evolution. Increase in the slopes of the transformation start and end regions in the stress-strain hysteresis loop is observed for mechanical loading with higher rates.

Effect of wave parameters on flood wave subsidence

A detailed analy~is on the propagation of a sinusoidal flood wave in a wide prismatic open channel b.as hen made by numc? ii.~ll~integrating We govemins nondimenional equations of unsteady flow in an open chamei. EmpE:dsis has been laid on the effect of wave parmefen on th propagation of 6.8 sinusoidal wave. Results show that the amount of subsidence is more in the case of small wave anplltude and wave duration cases. Further, wave duration has been noticed to have a relatively Vier influence on subsidence than wave amplitude. The speed at which the peak of the wave moves is observed to be a function of only the wave amplitude.

Diffusion Parameters in the Nb-Mo System: Revisited

The variation of the interdiffusion coefficient with the change in composition in the Nb-Mo system is determined in the temperature range of 1800 °C to 1900 °C. It was found that the activation energy has a minimum at around 45 at. pct Nb. The values of the pre-exponential factor and the activation energy for diffusion are compared with the data available in the literature. Further, the impurity diffusion coefficients of Nb in Mo and Mo in Nb are calculated.

Nucleation parameters for polymer crystallization from non-isothermal thermal analysis

Differential scanning calorimetry (DSC) has been used to obtain kinetic and nucleation parameters for polymer crystallization under a non-isothermal mode of operation. The available isothermal nucleation growth-rate equation has been modified for non-isothermal kinetic analysis. The values of the nucleation constant (K g ) and surface free energies (sgr, sgr e ) have been obtained for i-polybutene-1, i-polypropylene, poly(L-lactic acid), and polyoxymethylene and are compared with those obtained from isothermal kinetic analysis; a good agreement in both is seen.

Effect of experimental parameters on non-isothermal TG

The effect of some experimental parameters, namely sample weight, particle size and its distribution, heating rate and flow rate of inert gas, on the fractional decomposition of calcium carbonate samples have been studied both experimentally and theoretical. The general conclusions obtained from theoretical analysis are corroborated qualitatively by the experimental data. The analysis indicates that the kinetic compensating effect may be partly due to the variations in experimental parameters for different experiments.

Microstructural study of rapidly solidified titanium eutectoid alloysstar, open

Rapid solidification of Ti-7.3wt.%Cu (near-eutectoid composition), Ti-36.2wt.%Ni and Ti-34.3wt.% Ni-5.8wt.%Si alloys has been carried out by electron beam melting and splat quenching on a water-cooled rotating copper disc. The product obtained was in the form of thin ribbons 60–100 μm thick. Transmission electron microscopy studies of Ti---Cu alloy splats showed that the microstructure consisted of a mixture of martensite and a lamellar eutectoid product. The formation of the intermetallic compound Ti2Cu involved a diffusionless ω transformation and spinodal clustering. In the case of Ti---Ni alloy the as-quenched microstructure is complex, consisting of α, transformed β and intermetallic phases. This could have arisen possibly as a result of local variation in cooling rates. Rapid solidification of Ti---Ni---Si alloy resulted in partial quenching of an amorphous phase. The amorphous phase was seen to be extremely hard (a Vickers hardness of about 800 HV).

Isomerization Dynamics In Solution In The Absence Of An Activation Barrier - Evaluation Of The Potential Parameters

We analyze recent experimental results of Sundström and Gillbro by using the theory of Bagchi, Fleming and Oxtoby. The experimental results are in good agreement with this theory, but not with the earlier theory of Förster and Hoffmann. By fitting the new experimental results to the theory, we obtain approximate estimates of the frequency of the excited surface (assumed harmonic) and the width of the sink function.

Mapping compositional parameters of cocoa to sensory profiles

This project will establish an innovative quantitative analytical technique which will assist the development of Queensland's cocoa industry through a better understanding of those components that can produce unique sensory and flavour profiles of cocoa products.

Product-library-derived specification parameters in building information models augmentation

This paper conceptualizes a framework for bridging the BIM (building information modelling)-specifications divide through augmenting objects within BIM with specification parameters derived from a product library. We demonstrate how model information, enriched with data at various LODs (levels of development), can evolve simultaneously with design and construction using different representation of a window object embedded in a wall as lifecycle phase exemplars at different levels of granularity. The conceptual standpoint is informed by the need for exploring a methodological approach which extends beyond current limitations of current modelling platforms in enhancing the information content of BIM models. Therefore, this work demonstrates that BIM objects can be augmented with construction specification parameters leveraging product libraries.

Study of Friction and Transfer Layer Formation in Copper-Steel Tribo-System: Role of Surface Texture and Roughness Parameters

In the present investigation, experiments were conducted on a tribological couple-copper pin against steel plate-using an inclined pin-on-plate sliding tester to understand the role of surface texture and roughness parameters of the plate on the coefficient friction and transfer layer formation. Two surface characteristics of the steel plates-roughness and texture-were varied in the tests. It was observed that the transfer layer formation and the coefficient of friction along with its two components, namely, the adhesion and plowing, are controlled by the surface texture of the plate. The plowing component of friction was highest for the surface texture that promotes plane strain conditions while it was lowest for the texture that favors plane stress conditions at the interface. Dimensionless quantifiable roughness parameters were formulated to describe the degree of plowing and hence the plane strain/stress type deformations taking place at the asperity level.

Microstructural evolution and grain boundary sliding in a superplastic magnesium AZ31 alloy

Tensile experiments on a fine-grained single-phase Mg–Zn–Al alloy (AZ31) at 673 K revealed superplastic behavior with an elongation to failure of 475% at 1 × 10−4 s−1 and non-superplastic behavior with an elongation to failure of 160% at 1 × 10−2 s−1; the corresponding strain rate sensitivities under these conditions were 0.5 and 0.2, respectively. Measurements indicated that the grain boundary sliding (GBS) contribution to strain ξ was 30% under non-superplastic conditions; there was also a significant sharpening in texture during such deformation. Under superplastic conditions, ξ was 50% at both low and high elongations of 20% and 120%; the initial texture became more random under such conditions. In non-superplastic conditions, deformation occurred under steady-state conditions without grain growth before significant flow localization whereas, under superplastic conditions, there was grain growth during the early stages of deformation, leading to strain hardening. The grains retained equiaxed shapes under all experimental conditions. Superplastic deformation is attributed to GBS, while non-superplastic deformation is attributed to intragranular dislocation creep with some contribution from GBS. The retention of equiaxed grain shapes during dislocation creep is consistent with a model based on local recovery related to the disturbance of triple junctions.

Simultaneous prediction of acidity parameters (pH and titratable acidity) in Kefir using near infrared reflectance spectroscopy.

Acidity in terms of pH and titratable acids influences the texture and flavour of fermented dairy products, such as Kefir. However, the methods for determining pH and titratable acidity (TA) are time consuming. Near infrared (NIR) spectroscopy is a non-destructive method, which simultaneously predicts multiple traits from a single scan and can be used to predict pH and TA. The best pH NIR calibration model was obtained with no spectral pre-treatment applied, whereas smoothing was found to be the best pre-treatment to develop the TA calibration model. Using cross-validation, the prediction results were found acceptable for both pH and TA. With external validation, similar results were found for pH and TA, and both models were found to be acceptable for screening purposes.

Male traits and herd reproductive capability in tropical beef cattle. 2. Genetic parameters of bull traits

A total of 4063 young bulls of two tropical genotypes (1639 Brahman and 2424 Tropical Composite) raised in northern Australia were evaluated for a comprehensive range of production and reproduction traits up to 24 months of age. Prior to weaning, peripheral blood concentrations of luteinising hormone (LH) and inhibin were measured at 4 months of age. At weaning (6 months) blood insulin-like growth factor-1 (IGF-I) and flight time were recorded. Body composition traits of fat depth and eye-muscle area were determined by ultrasonography at 15 months of age when additional measurements of liveweight, hip height and body condition score were recorded. Bull breeding soundness was evaluated at similar to 12, 18 and 24 months of age when measurements of scrotal circumference, sheath score, semen mass activity, progressive motility of individual sperm and percent morphologically normal sperm were recorded. Magnitude of heritability and genetic correlations changed across time for some traits. Heritability of LH, inhibin, IGF-I and of 18-month scrotal circumference, mass activity, progressive motility and percent normal sperm was 0.31, 0.74, 0.44, 0.75, 0.24, 0.15 and 0.25, respectively, for Brahmans and 0.48, 0.72, 0.36, 0.43, 0.13, 0.15 and 0.20, respectively, for Tropical Composites. Inhibin and IGF-I had moderate genetic association with percent normal sperm at 24 months in Brahmans but low to negligible associations in Tropical Composites. Body condition score in Brahmans and sperm motility (mass and individual) traits in both genotypes had moderate to strong genetic correlation with percent normal sperm and may prove useful candidates for indirect selection. There is scope to increase scrotal circumference by selection and this will be associated with favourable correlated responses of improved semen quality in both genotypes. The lack of genetic antagonism among bull traits indicates that selection for improved semen quality will not adversely affect other production traits.

Optimal simultaneous maximum a posterioriestimation of states, noise statistics and parameters I. Algorithm

The simultaneous state and parameter estimation problem for a linear discrete-time system with unknown noise statistics is treated as a large-scale optimization problem. The a posterioriprobability density function is maximized directly with respect to the states and parameters subject to the constraint of the system dynamics. The resulting optimization problem is too large for any of the standard non-linear programming techniques and hence an hierarchical optimization approach is proposed. It turns out that the states can be computed at the first levelfor given noise and system parameters. These, in turn, are to be modified at the second level.The states are to be computed from a large system of linear equations and two solution methods are considered for solving these equations, limiting the horizon to a suitable length. The resulting algorithm is a filter-smoother, suitable for off-line as well as on-line state estimation for given noise and system parameters. The second level problem is split up into two, one for modifying the noise statistics and the other for modifying the system parameters. An adaptive relaxation technique is proposed for modifying the noise statistics and a modified Gauss-Newton technique is used to adjust the system parameters.