A temperature oscillation instrument to determine pyroelectric properties of materials at low frequencies: Towards elimination of lock-in methods

Pyroelectric properties of materials can be accurately determined by applying a new digital signal processing method on the discrete sampled data obtained with a temperature oscillation technique. The pyroelectric coefficient is calculated from the component of the generated current 90? out of phase with respect to the sinusoidal temperature...

Prediction and Validation of the Austenite Phase Fraction upon Intercritical Annealing of Medium Mn Steels

In this research, the effects of Mn and Si concentration and that of the isothermal intercritical holding temperature on the austenite-to-ferrite (? ? ?) and the martensite-to-austenite (?? ? ?) phase transformations are studied for a series of Fe-C-Mn-Si steels with up to 7 wt pct Mn. The model is based on the local equilibrium (LE) concept....

Process-time Optimization of Vacuum Degassing Using a Genetic Alloy Design Approach

This paper demonstrates the use of a new model consisting of a genetic algorithm in combination with thermodynamic calculations and analytical process models to minimize the processing time during a vacuum degassing treatment of liquid steel. The model sets multiple simultaneous targets for final S, N, O, Si and Al levels and uses the total slag...

Switchable static friction of piezoelectric composite—silicon wafer contacts

The meso-scale surface roughness of piezoelectric fiber composites can be manipulated by applying an electric field to a piezocomposite with a polished surface. In the absence of an applied voltage, the tips of the embedded piezoelectric ceramic fibers are below the surface of the piezocomposite and a silicon wafer counter surface rests solely...

Piezoelectric and mechanical properties of structured PZT–epoxy composites

Structured lead zirconium titanate (PZT)–epoxy composites are prepared by dielectrophoresis. The piezoelectric and dielectric properties of the composites as a function of PZT volume fraction are investigated and compared with the corresponding unstructured composites. The effect of poling voltage on piezoelectric properties of the composites is...

Modeling and characterization of dielectrophoretically structured piezoelectric composites using piezoceramic particle inclusions with high aspect ratios + Erratum

In this work, the piezoelectric properties at high electric fields of dielectrophoretically aligned PZT—polymer composites containing high aspect ratio particles (such as short fibers) are presented. Polarization and strain as a function of electric field are evaluated. The properties of the composites are compared to those of PZT-polymer...

Dielectrophoretically structured piezoelectric composites with high aspect ratio piezoelectric particles inclusions

Piezoelectric composites were prepared by dielectrophoretic alignment of high aspect ratio piezoelectric particles in a thermosetting polymer matrix. A high level of alignment was achieved in the cured composite from a resin containing randomly oriented high aspect ratio particles. Upon application of an electric field during curing of the resin...

Analysis of the fractal dimension of grain boundaries of AA7050 aluminum alloys and its relationship to fracture toughness

Quantitative analysis of the grain boundaries in partially recrystallized microstructures of heat-treated 7050 aluminum alloys has been performed. Fractal dimensions of the extracted grain boundaries were calculated by boxcounting method. Five different types of tear-tested materials rolled in different processes each at two orientations of 0º...

Tuning the stress induced martensitic formation in titanium alloys by alloy design

Direct strain energy harvesting in automobile tires using piezoelectric PZT–polymer composites

Direct piezoelectric strain energy harvesting can be used to power wireless autonomous sensors in environments where low frequency, high strains are present, such as in automobile tires during operation. However, these high strains place stringent demands on the materials with respect to mechanical failure or depolarization, especially at...

Modeling of soft impingement effect during solid-state partitioning phase transformations in binary alloys

The soft impingement effect at the later stage of partitioning phase transformations has been modeled both for the diffusion-controlled growth model and for the mixed-mode model. Instead of the linear and exponential approximations for the concentration gradient in front of the interface used in the past, a general polynomial method of dealing...

Improving the d33 and g33 properties of 0-3 piezoelectric composites by dielectrophoresis

Composites of piezoelectric particles in a polymer matrix with enhanced properties in the poling direction were prepared by dielectrophoretic alignment of the particles. The effect of processing parameters such as the amplitude and frequency of the applied electric field and the viscosity of the matrix on the dielectric and piezoelectric...

Bidirectional current-voltage converters based on magnetostrictive/piezoelectric composites

We report a power supply-free, bidirectional electric current-voltage converter based on a coil-wound laminated composite of magnetostrictive alloy and piezoelectric crystal. An electric current applied to the coil induces a magnetic field, resulting in an electric voltage from the composite due to the direct magnetoelectric effect. Conversely,...

Modelling plastic deformation of metals over a wide range of strain rates using irreversible thermodynamics

Based on the theory of irreversible thermodynamics, the present work proposes a dislocation-based model to describe the plastic deformation of FCC metals over wide ranges of strain rates. The stress-strain behaviour and the evolution of the average dislocation density are derived. It is found that there is a transitional strain rate (~104 s-1)...

A mathematical analysis of physiological and morphological aspects of wound closure

A computational algorithm to study the evolution of complex wound morphologies is developed based on a model of wound closure by cell mitosis and migration due to Adam [Math Comput Model 30(5–6):23–32, 1999]. A detailed analysis of the model provides estimated values for the incubation and healing times. Furthermore, a set of inequalities are...

Modification of a thermomechanical model to predict constitutive behavior of Al-Mg-Si alloys

A previously developed constitutive model for quantification of the effect of the condition of Mg and Si in AA6xxx alloys was used for the prediction of the flow stresses measured by plane strain compression (PSC) tests. As an extension of earlier work, two AA6xxx alloys were subjected to different thermal pretreatments and were plane strain...