DETERMINATION OF MECHANICAL PROPERTIES OF THIN FILMS AND FUNCTIONAL GRADIENT MATERIALS USING INVERSE TECHNIQUE
This paper describes a method for evaluating material properties of multi-layered systems and functional gradient materials using data obtained from indentation testing. The measurement data collected from the penetration force-depth curves in the test are employed for identifying elastic moduli of thin films and functional gradient materials. An indentation problem is first analyzed on the basis of the three-dimensional axisymmetric theory of elasticity. Analyses of elastic contact problem, which an elastic axisymmetric indenter is penetrated into multi-layered systems and into functional gradient materials, are presented. An inverse analysis for determining Young’s moduli, Poisson’s ratios and radii of the contact area is performed under the assumption that the elastic moduli of the substrate and the indenter, and thicknesses for layers are known. When complex method is used for minimizing an objective function composed of errors, effective sampling of data obtained by penetrating indenters with various radii of curvature into the coated substrate and functional gradient materials is presented. INTRODUCTION Modern electric devices and mass storage devices have frequently multilayered structures to achieve a high performance and functionality. Furthermore, such devices are coated often by metal thin films to protect from the damage of external dusts and environment. It is important to estimate their mechanical properties for improving the reliability of devices and machines. Generally, mechanical properties of thin films deposited on a substrate are different from those of bulk. Hence, we need to know in-situ the mechanical properties of deposited films. However, it is very hard to carry out a test for evaluating the mechanical properties of films in a sub-micrometer thickness. Ihara, et al. estimated the material properties of a thin film using surface wave spectroscopy. Matui, et al. examined the accuracy of identified elastic moduli in a multilayered system. Kishimoto, et al. idetified the elastic properties for a bar of functional gradient materials. Indentation test is one of methods for evaluating the mechanical properties of thin films, which is the one estimating elastic moduli of thin films using experimental data of the force and the depth of an indenter penetrated into a multi-layered system. In the present paper, when data of the indentation force and depth are used, a method for identifying the mechanical properties of thin films and the distribution function of mechanical properties in functional gradient materials will be presented. ANALYSIS OF INDENTATION PROBLEMS In the present analysis, an axisymmetric elastic indenter with a cross section of f(r) will be penetrated into an elastic half-region composed of layers with various mechanical properties as shown in Figure 1. This contact problem is analyzed using the theory of threedimensional axisymmetric elasticity. Then, displacements and stresses in the layers, the indenter and the elastic half-region can be deduced by substituting Boussinesq’s potential functions, ψ and φ 3 , into the following relationships (Miyamoto 1977, Gladwell 1980).
Inverse Problem Solution in Non-Destructive Pavement Diagnostics — Computational Aspects
Determination of pavement layer moduli from measured surface deformation is performed by the iteration process based on capability to calculate deformation derivatives with respect to elastic moduli. A priori information on the processed data is used to stabilize process of solution in the case of the greater number of considered layers. The applicability of obtained results is conditioned also by the accuracy with which the imperfect bonding of layers is accounted for.
Multiple-dose pharmacokinetics of moxisylyte after oral administration to healthy volunteers.
The pharmacokinetics of moxisylyte in plasma and urine was investigated after oral administration. Twelve subjects were treated orally, twice daily with 240 mg of the drug for 6 days; on day 7, the subjects received a last dose of 240 mg of moxisylyte. Moxisylyte was assayed in plasma and urine by a specific HPLC method with fluorimetric detection. Moxisylyte was absorbed rapidly and changed to its metabolites immediately after drug administration; unchanged moxisylyte was not found in plasma. Two metabolites were found in plasma and urine: conjugated desacetylmoxisylyte (DAM) and the conjugate of desmethylated DAM (MDAM). The pharmacokinetic parameters determined after the first oral administration were not modified on multiple dosing. The apparent elimination half-lives of conjugated DAM and MDAM were 2.3 and 3.5 h, respectively. Elimination of these two metabolites in urine averaged 50 and 10%, respectively.