Determination of Elastic and Creep Properties of Thin-film Systems from indentation Experiments

Based on the detailed computer .simulation of the indentation testing on the thin-film systems, the present paper explores the detailed procedure of determining elastic properties (elastic modulus E(f) and Poisson ratio v(f) ) and creep parameters (CCREEP (f) and nCREEP (f)) for a simple Norton law (ε=CCREEP (f)σnCREEP(f), where ε is creep strain rate, and σ is the stress) material for a thin film coated on a creep substrate, whose elastic properties(E(s) and v(s)) and creep properties (CCREEP(s) and nCREEP(s) ) of the substrate are known, from indentation elastic and creep testing, respectively. The influences of the thickness of the thin-film and the size of the indenter on the indentation behavior have been discussed. It is shown that the boundary between the thin film and the substrate has great influence on the indentation creep behavior. The relative sizes of indentation systems are chosen so that the behavior of the indentation on the film is influenced by the substrate. The two elastic parameters E(f) and v(f) of the film are coupled on the influence of the elastic behavior of indentation. With the two different size indenters, the two elastic parameters E(f) and v(f) of the film can be uniquely determined by the indentation experimental slopes of depth to applied net section stress results. The procedure of determining of the two Norton law parameters CCREEP (f) and nCREEP(f) includes the following steps by the steady indentation rate d. The first step to calculate the creep indentation rate on certain loads of the two different sizes of indenters on a set of assumed values of CCREEP (f) and nCREEP (f). Then to build relationship between the creep indentation rate and the assumed CCREEP(f) and nCREEP(f). With the experimental creep indentation rate to intersect two sets of CCREEP (f) and nCREEP(f), which have the same values of d. The last step is to build the CCREEP(f) and nCREEP(f)curves from the intersection points for the two indenters.These two curves CCREEP and nCREEP(f) will intersect at one point. The axial values of the point are what we want. The procedure presented in the paper to determine the elastic parameters and creep parameters from the indentation experiments can be applied to any material systems.