Design Of Multilayer Coatings Research Articles

Semi-analytical model for rough multilayered contacts

This paper presents a new model for analysis of non-conformal rough surface contacts where one or both of the contacting bodies are coated with a multilayered coating. The model considers elastic contact of arbitrary geometry with real measured roughnesses and both normal and tangential surface loads. It predicts contact pressure distribution, surface deformations and full subsurface stress field. As such, the model offers an optimisation tool for analysis and development of multilayered coatings. Influence coefficients approach is utilised to obtain contact pressures and subsurface stresses while the contact solver is based on a standard conjugate gradient method. To improve model efficiency, a semi-analytical approach is devised, where the influence coefficients for displacements and stresses are expressed explicitly by solving the fundamental equations in the frequency domain. Fast Fourier Transforms in conjunction with discrete convolution are then utilised to provide the solution in spatial domain. Selected results are presented to first validate the model and then illustrate the potential improvements that can be achieved in the design of multilayered coatings through application of the model.

GS0501-214 非連成解析による多層塗膜の動的損傷力学シミュレーション

In this research we use uncoupled analysis to evaluate the impact resistance of multi-layer coatings. We conduct high strain-rate simulation by ANSYS. Then the results of stress and strain are in put to damage analysis program which employs the elasto-viscoplastic damage constitutive equation based on continuum damage mechanics. Both of tensile fracture analysis and drop impact analysis have almost agreed well with the corresponding experimental results. Uncoupled analysis for dynamic damage mechanics problems can be expected to be used as a computational tool for the evaluation and the design of multi-layer coatings.

Identification of Dynamic Damage Mechanics Models and Tensile Fracture Analysis for Multi-Layer Coatings

As the first step of the development of a computational tool to evaluate the impact resistance of multi-layer coatings, the authors have conducted the formulation of elasto-viscoplastic damage constitutive equation based on continuum damage mechanics and extended to high strain-rate behaviors, the identification of the constitutive modeling based on the tensile test results for each layer material, and its applications to the finite element analysis of tensile fracture behaviors of multi-layer coatings. The obtained results of the identification of constitutive modeling and the tensile fracture analysis have agreed well with the corresponding experimental results. The present dynamic damage mechanics models can be expected to be used as a computational tool for the evaluation and the design of multi-layer coatings.

Design of multilayer polymeric coatings for indentation resistance

Indentation is often a mode of in-service loading for a thin coating deposited on a substrate. Under such a loading, the strong adherence of the coating to the substrate is a basic necessity for successful performance of the coating. In this study, we investigate the indentation behavior of thin single and multilayered polymeric coatings using the finite element method. The deformation patterns and the stress fields that are generated during indentation are obtained by employing constitutive models which accurately represent the elastic-viscoplastic and hyperelastic behavior of the glassy and rubbery states of the polymeric layers under investigation. Three types of loading conditions are considered: indentation to (1) a fixed depth; (2) a fixed work; and (3) a fixed force. For these loading conditions, we then investigate the mechanical performance of various composite coatings subjected to an overall thickness design constraint. The composite structure is altered via variation in individual layer material composition, layer thickness and layer arrangement. It is shown how the placement of different material layers in a multilayer coating can alter the flow pattern and hence the distribution of stress state and resulting failure. It is also shown that a soft rubber elastic layer acts to greatly minimize the interfacial shear stress at the substrate, thereby reducing the risk of delamination of the coating, but the presence of the rubber can also produce detrimental tensile stresses on the surface. We then demonstrate that the tensile stress state can be eliminated through manipulation of the rubber layer thickness, without increasing the interface shear stress. Through these examples, a framework for evaluation and design of multilayer coatings for indentation resistance is provided.

Reflectivity minimization of semiconductor laser amplifiers with coated and angled facets considering two-dimensional beam profiles

The reflectivity minimization of semiconductor laser amplifiers and waveguides with straight and angle facets is considered. A formalism, taking two-dimensional waveguides effects into account, that allows the design of multilayer coatings on output facets with minimized reflectivities for either the transverse-electric (TE), transverse-magnetic (TM), or both polarizations is developed. A detailed study of residual modal reflectivities for two-dimensional rectangular laser profiles is presented. Reflectivities as low as 10/sup -4/-10/sup -5/ are achieved using angled output facets. The reflectivity of higher order modes and mode conversion are shown to limit the residual reflectivities of tilted laser outputs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design method for multilayer interference filters

In this paper expressions for the transmittance and the reflectance of a system consisting of a spacer surrounded by two multilayer stacks are presented. These expressions provide a general approach for the design of multilayer coatings. High- and low-transmittance bands and a narrowband in the transmittance spectrum of multilayer stacks with unequal designed wavelengths are reported.