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Microstructural Effects (microstructural + effects)

Distribution by Scientific Domains

Polymers and Materials Science	60%

Selected Abstracts

Microstructural effects on hot drawing syndiotactic styrene P-methyl styrene copolymer

POLYMER ENGINEERING & SCIENCE, Issue 10 2001
R. J. Yan
Crystalline syndiotactic styrene/p-methyl styrene copolymer (SPMS) has been oriented by tensile drawing at various temperatures between the glass transition and crystalline melting point. The microstructural changes resulting from drawing have been studied using differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). WIth increasing draw temperature, both melting temperature and crystalline dimensions of the oriented samples increase. The heat of fusion increases with increasing draw temperature up to ,200°C. It also increases with draw ratio and draw rate, while the crystalline width increases only with draw ratio. THe amorphous fraction shows a clear glass transition, the temperature of which (Tg) increases with draw ratio. However, Tg decreases somewhat with increasing draw temperature. This is interpreted in terms of the stretching of the randomly coiled amorphous phase molecules. [source]

Thermodynamic consistent modelling of defects and microstructures in ferroelectrics

GAMM - MITTEILUNGEN, Issue 2 2008
Ralf Müller
Abstract The paper describes the main phenomena associated with fatigue in ferroelectricmaterials due to defects and microstructural effects. An analysis the modelling on different length scales is presented. Starting from a thermodynamic analysis of the macroscopic material behavior other microscopic aspects are addressed. The introduction of an orientation distribution function allows for a computationally efficient extension of a single crystal model to realistic 3D structures. Additionally, the thermodynamic treatment of defects and domain wall motion is discussed to provide a better understanding of various micro-mechanisms. It is explained by the concept of configurational/driving forces, how defects influence each other and how the mobility of domain walls is reduced in the presence of defects. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

An advanced boundary element method for solving 2D and 3D static problems in Mindlin's strain-gradient theory of elasticity

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2010
G. F. Karlis
Abstract An advanced boundary element method (BEM) for solving two- (2D) and three-dimensional (3D) problems in materials with microstructural effects is presented. The analysis is performed in the context of Mindlin's Form-II gradient elastic theory. The fundamental solution of the equilibrium partial differential equation is explicitly derived. The integral representation of the problem, consisting of two boundary integral equations, one for displacements and the other for its normal derivative, is developed. The global boundary of the analyzed domain is discretized into quadratic line and quadrilateral elements for 2D and 3D problems, respectively. Representative 2D and 3D numerical examples are presented to illustrate the method, demonstrate its accuracy and efficiency and assess the gradient effect on the response. The importance of satisfying the correct boundary conditions in gradient elastic problems is illustrated with the solution of simple 2D problems. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Mechanical Properties of Sputter-Deposited Titanium-Silicon-Carbon Films

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2001
James E. Krzanowski
The effect of SiC additions on the mechanical properties of TiC films was investigated. Ti-Si-C films with varying SiC content were deposited using dual-cathode radio-frequency magnetron sputtering. The nanoindentation hardness of these films increased with SiC content to a maximum of 20,22 GPa for films in the range of 15,30 at.% SiC. The elastic modulus was also measured, and the hardness to modulus ratio (H/E) increased with SiC content, indicating that hardness increases were due to microstructural effects. The residual stress was measured in several films, but was low in magnitude, indicating that hardness measurements were not influenced by residual stress. TEM examination of several films revealed that the SiC additions altered the film microstructure in a manner that could account for the observed hardness increases. [source]

Failure prediction for Titanium alloys using a superplastic forming limit diagram approach

MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4-5 2008
S.B. Leen
Abstract Superplastic forming limit diagrams (SPFLDs) are presented for both Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo alloys. FE-predicted ,1 - ,3 -,eq paths for key points on the forming blank are then plotted on the SPFLD to predict failure. A key factor for reliable SPF forming limit prediction is the incorporation of a mechanisms-based constitutive model, which includes microstructural effects, such as static and dynamic grain growth and associated hardening, and with material constants independent of the forming strain-rate. The sinh model of Dunne and co-workers is thus employed. Results from forming trials for both materials are used to assess the failure predictions. [source]