Spherical indentation of compositionally graded materials: Theory and experiments

• Published in: Acta materialia Vol. 45; no. 4; pp. 1307 - 1321
• Main Authors: Suresh, S., Giannakopoulos, A.E., Alcalá, J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.1997; Elsevier Science
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Deformation and plasticity (including yield, ductility, and superplasticity); Exact sciences and technology; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Metals. Metallurgy; Physics; Nickel base alloys; Spherical shape; Elasticity; Theoretical study; Mechanical properties; Plastic deformation; Experimental study; Indentation; Titanium base alloys; Young modulus; Finite element method; Composite materials; Stress distribution; Simulation; Poisson ratio; Strain distribution; Alumina; Yttrium oxides
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/S1359-6454(96)00291-1

Computational and experimental results on the evolution of stresses and deformation fields due to indentation from a rigid spherical indenter on a graded substrate are presented. The analyses address the variations in Young's modulus, E, of the substrate as a function of depth, z, beneath the indented surface for an exponential law, E = E 0e αz , where E 0 is Young's modulus at the surface and 1 α is a length parameter. The finite element simulations are used to check the analytical theory of Giannakopoulos and Suresh [ Int. J. Solids Struct. (in press)], and are used to gain further insights into the effects of the variation in Poisson ratio, v, with depth. The theoretically predicted force-indenter penetration ( P-h) curves are also compared with direct experimental measurements made on compositionally graded NiAl 2O 3 and TiAlY 2O 3-stabilized TZP composites of known composition gradients. A new method is proposed for the estimation of Young's modulus variations through a compositionally graded layer by recourse to spherical indentation.