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Elastic Energy (elastic + energy)
Selected AbstractsSolution-precipitation creep , micromechanical modelling and numerical resultsPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005Sandra Ili Our aim is to present a continuum mechanical model for solution-precipitation creep as well as to compare the numerical results based on that model with experimental observations. The formulation of the problem is based on the minimization of a Lagrangian consisting of elastic power and dissipation. Elastic energy is chosen to be in a standard form but dissipation is strongly adapted to the solution-precipitation process by introducing two new quantities: the velocity of material transport within the crystallite-interfaces and the normal velocity of precipitation or solution respectively. The model enables one to give an analytical solution for the case of a single crystal and numerical solution based on a finite element method for more complex, polycrystalline materials. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystal mismatched layers in pentagonal nanorods and nanoparticlesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2010L. M. Dorogin Abstract Pentagonal nanorods (PNRs) and nanoparticles (PNPs) covered by mismatched shell layers are theoretically investigated. Mechanical stresses and elastic energies of such objects are calculated analytically and analyzed in the framework of linear isotropic elasticity. Difference between elastic modules of core and shell is taken into account. The threshold radiuses as the minimal radiuses of PNR and PNP for which the formation of the shell layer is energetically favorable are found. The threshold radius is approximately 10,nm for PNPs and 100,nm for PNRs of typical face-centered cubic (FCC) metals. The optimal magnitudes of mismatch parameter giving the maximal energy release for shelled PNRs and PNPs are determined. [source] Superficial digital flexor tendon lesions in racehorses as a sequela to muscle fatigue: A preliminary studyEQUINE VETERINARY JOURNAL, Issue 6 2007M. T. Butcher Summary Reasons for performing study: Racing and training related lesions of the forelimb superficial digital flexor tendon are a common career ending injury to racehorses but aetiology and/or predisposing causes of the injury are not completely understood. Objectives: Although the injury takes place within the tendon, the lesion must be considered within the context of the function of the complete suspensory system of the distal limb, including the associated muscles. Methods: Both muscle and tendon function were investigated in vivo using implanted strain gauges in 3 Thoroughbred horses walking, trotting and cantering on a motorised treadmill. These data were combined with assessments of muscle architecture and fibre composition to arrive at an overview of the contribution of each muscle-tendon unit during locomotion. Results: The superficial digital flexor muscle has fatigue-resistant and high force production properties that allow its tendon to store and return elastic energy, predominantly at the trot. As running speed increases, deep digital flexor tendon force increases and it stabilises hyperextension of the fetlock, thus reinforcing the superficial digital flexor in limb load support. The deep digital flexor muscle has fast contracting properties that render it susceptible to fatigue. Conclusion: Based on these measurements and supporting evidence from the literature, it is proposed that overloading of the superficial digital flexor tendon results from fatigue of the synergistic, faster contracting deep digital flexor muscle. Potential relevance: Future research investigating distal limb system function as a whole should help refine clinical diagnostic procedures and exercise training approaches that will lead to more effective prevention and treatment of digital flexor tendon injuries in equine athletes. [source] Polymer/NiTi-composites: Fundamental Aspects, Processing and Properties,ADVANCED ENGINEERING MATERIALS, Issue 11 2005K. Neuking NiTi shape memory alloys can be used as actor materials and perform mechanical work; they can also be used for damping applications. In combination with polymers their functionality can be increased. Shape memory effects of NiTi alloys are associated with large strains and in a NiTi/polymer-composite, the polymer can accommodate these large strains without breaking. In a NiTi/polymer-composite the polymer can for example be used to store elastic energy, to provide corrosion resistance or to assist in a damping application. For all applications, a good bonding between the shape memory alloy and the polymer is required. The present paper considers fields of applications, processing and properties of NiTi/polymer-composites. [source] Identification of dislocations in large tetragonal hen egg-white lysozyme crystals by synchrotron white-beam topographyJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2003M. Tachibana Large tetragonal hen egg-white (HEW) lysozyme crystals have been grown by a salt concentration-gradient method. The grown crystals, of thicknesses greater than 1.5,mm, were observed by means of X-ray topography using white-beam synchrotron radiation. Line contrasts clearly appeared on the Laue topographs. Extinction of the line images was observed in specific reflections. These results mean that the observed lines correspond to dislocation images. From the extinction criterion it is shown that the predominant dislocations are of screw character with ,110, Burgers vectors. In addition, dislocation loops with [001] Burgers vectors have been found in a tetragonal HEW lysozyme crystal including some cracks. These results are discussed in the light of dislocation elastic energy and slip systems in the crystals. [source] Phase Field Simulations of Hysteresis and Butterfly Loops in Ferroelectrics Subjected to Electro-Mechanical Coupled LoadingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2006A. K. Soh Two-dimensional computer simulations of ferroelectric polarization switching have been performed using the phase field simulation model developed by employing the time-dependent Ginsburg,Landau equations. The bulk-free energy, polarization gradient energy, long-range dipole,dipole electrostatic interactions, and elastic energy were taken into account in the above-mentioned simulations. The influences of electric,mechanical coupled loading on the hysteresis and butterfly loops were studied. The results showed that the coupled electro-mechanical loading could change both the coercive field of ferroelectric materials and the symmetry of hysteresis and butterfly loops. [source] Thermomechanical studies of aluminum nitride filled shape memory polymer compositesPOLYMER COMPOSITES, Issue 3 2007Muhammad Yasar Razzaq High thermal conductivity polyurethane shape memory polymer (SMP) composites filled with aluminum nitride (AlN) were fabricated, and their thermal and thermomechanical properties were studied. The purpose of this microstructure is to improve the thermal properties of the SMPs at low filler content. Morphology of AlN filler in polyurethane SMP matrix and the resulting thermal conductivity was also investigated. Thermal studies have shown that AlN is an effective filler for reinforcement of the polyurethane SMP and that it does not deteriorate the stable physical crosslink structure of the polyurethane, which is necessary to store the elastic energy in the service process of the shape memory material. The thermal conductivities of these SMP composites in relation to filler concentration and temperature were investigated, and it was found that the thermal conductivity can increase up to 50 times in comparison with that of the pure SMP. Furthermore, differential scanning calorimetry tests have shown a significant decrease in the glass transition temperature of the switching segment. Dynamic mechanical studies have shown that the storage modulus of the composites increase with higher AlN content in both glassy and rubbery state. Damping peak decreases and also the curve of damping becomes broader with increasing filler content. Strain fixity rate which expresses the ability of the specimens to fix their strain has been improved slightly in the presence of AlN filler but the final recovery rate of the shape memory measurement has decreased evidently. POLYM. COMPOS., 28:287,293, 2007. © 2007 Society of Plastics Engineers [source] | ||||||||||