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-fi Im systems, the. present paper explores the detailed procedure of determining elastic properties (elastic modulus E-(f) and Poisson ratio nu ((f))) and creep parameters (C-CREEP ((f)) and n(CREEP) ((f))) for a simple Norton law ((epsilon) over dot =C-CREEP ((f))sigma (n)(CREEP) ((f)), where (epsilon) over dot is creep strain rate, and sigma is the stress) material for a thin film coated on a creep substrate, whose elastic properties(E-(s ) and nu ((s))) and creep properties (C-CREEP((s)) and n(CREEP) ((s))) of t he substrate are known, from indentation elastic and creep testing, respect ively. 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 o n the indentation creep behavior. The relative sizes of indentation systems are chosen so that the behavior of the indentation on the film is influenc ed by the substrate. The two elastic parameters E-(f) and nu ((f)) of the f ilm are coupled on the influence of the elastic behavior of indentation. Wi th the two different size indenters, the two elastic parameters E-(f) and v ((f)) of the film can be uniquely determined by the indentation experimenta l slopes of depth to applied net section stress results. The procedure of d etermining of the two Norton law parameters C-CREEP ((f)) and n(CREEP) ((f) ) includes the following steps by the steady indentation rate a. The first step to calculate the creep indentation rate on certain loads of the two di fferent sizes of indenters on a set of assumed values of C-CREEP ((f)) and n(CREEP) ((f)) Then to build relationship between the creep indentation rat e and the assumed C-CREEP((f)) and n(CREEP)((f)). With the experimental cre ep indentation rate to intersect two sets of C-CREEP((f)) and n(CREEP)((f)) , which have the same values of a. The last step is to build the C-CREEP((f )) and n(CREEP)((f)) curves from the intersection points for the two indent ers. These two curves C-CREEP((f)) and n(CREEP)((f)) will intersect at one point. The axial values of the point are what we want. The procedure presen ted in the paper to determine the elastic parameters and creep parameters f rom the indentation experiments can be applied to any material systems.