AVS 49th International Symposium
    Surface Engineering Tuesday Sessions
       Session SE+TF-TuA

Invited Paper SE+TF-TuA1
Mechanical Design of Coated Systems Based on Elastic Surface Contacts

Tuesday, November 5, 2002, 2:00 pm, Room C-111B

Session: Systems Design of Functional Coatings
Presenter: T. Chudoba, Federal Institute of Materials Research and Testing, Germany
Authors: T. Chudoba, Federal Institute of Materials Research and Testing, Germany
N. Schwarzer, TU Chemnitz, Germany
I. Hermann, TU Chemnitz, Germany
F. Richter, TU Chemnitz, Germany
Correspondent: Click to Email
Problems in contact mechanics can be solved very conveniently using analytical solutions, even for layered systems and non-axissymmetric systems involving friction. The calculation time is much lower than for finite element calculations, especially for non-axissymmetric problems, and allows an optimization in a large parameter field, which is difficult to achieve with other methods. In many cases, with a foreknowledge of the type of failure to be avoided, the elastic stress fields computed permit critical values of stress to be avoided by a change in input parameters. One of the key requirements of an analytical solution to a contact problem is the availability of accurate and representative values of material properties. Such properties are not generally available for thin film systems where mechanical properties may not be the same as the bulk properties. The present work shows how elastic modulus and yield stress can be obtained experimentally using nanoindentation techniques for films down to a thickness of some nanometres. Results are given for several film substrate combinations. The parameters can be used for a mechanical modelling to optimize film thickness or to find the required mechanical properties of an intermediate layer to withstand a Hertzian contact at the surface. This is demonstrated by some calculations. In another example ternary (B,C,N) films on Si and fused silica produced by magnetron sputtering with a modulus range of 130 GPa to 300 GPa are used. The mechanical properties so obtained are then used as inputs in an analytical model to determine the optimum thickness and properties of an interlayer for a particular loading configuration, that of contact with a spherical indenter. The work extends the analytical treatment to nearly any cases of indenter shape by showing how the results of individual elastic analytical solutions can be assembled and solved using boundary element methods.