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).
On the identification of elastoviscoplastic constitutive laws from indentation tests
This paper addresses the identification of the parameters of a nonlinear constitutive law from indentation tests. The identification problem is considered as a constrained minimization problem and the gradient is computed using the adjoint state method, in spite of the difficulties of the underlying contact problem. This provides a general framework to perform optimization in some problems involving contact conditions and nonlinear material behaviour. The case of a Maxwell viscoelastic and a Norton-Hoff elastoviscoplastic constitutive law are treated extensively and a series of numerical identification examples are shown.
Antitumor activities of (2"R)-4'-O-tetrahydropyranyl-adriamycin (THP) and its combination with other antitumor agents on murine tumors.
(2''R)-4'-O-Tetrahydropyranyladriamycin (THP) is a new derivative of doxorubicin (adriamycin, ADM). The concentrations of THP and ADM required to inhibit by 50% the growth of a cultured L1210 cells was 0.003 microgram/ml and 0.016 microgram/ml, respectively. Various therapeutic designs of combinations of THP with other antitumor agents were investigated in vivo using the L1210 murine leukemia. The combination of THP with cytosine arabinoside (Ara-C), cyclocytidine hydrochloride (Cyclo-C), 6-mercaptopurine (6-MP) and cyclophosphamide (EX) showed a great effectiveness following daily intraperitoneal treatment from days 1 to 10. High therapeutic effects were also obtained with the combinations of THP with Ara-C, Cyclo-C, vincristine (VCR) and EX following intravenous combination therapy one day following implantation of L1210 leukemia. Schedule dependency and its therapeutic efficacy of THP were examined. THP showed almost the same antitumor activity on the solid-type sarcoma-180 or solid-type Ehrlich carcinoma as ADM by intraperitoneal or intravenous treatment. THP showed some superior activity to ADM in the advanced stage of L1210 leukemia. High antitumor activity of THP on murine leukemia L1210 has been reported by Tsuruo et al. (Cancer Res. 42: 1462-1467, 1982) and was also confirmed. THP gave many mice cures, especially in the intravenous treatment.