This article presents a methodology for evaluating the yield strength and hardening behavior of metallic materials by spherical indentation. Two types of assumed material behaviors with a pure elastic-Hollomon’s power law hardening and a pure elastic-linear hardening were considered separately in the models of spherical indentation. The numerical relationships between the material properties and indentation responses were established on the basis of dimensional and finite element analysis. As the first approximation to the real plastic flow properties, the yield strengths and hardening behaviors determined from the spherical indentation loading curve and the numerical relationships were used to derive the intersecting points between Hollomon’s power law hardening curve and linear hardening line. Through proceeding the three parameter’s regression analysis with Swift’s power law function for the intersecting points determined at different maximum indentation depths, the final yield strength and hardening behavior of tested material can be obtained. The validation of this method was examined by investigating three groups of materials with near linear hardening behavior, near Hollomon’s power law hardening behavior, and initial yield plateau. It is concluded that the proposed method is applicable to a wide variety of materials which exhibit separate hardening behaviors.

Ma, D., Ong, C. W., Lu, J., & He, J. (2003). Methodology for the evaluation of yield strength and hardening behavior of metallic materials by indentation with spherical tip. Journal of Applied Physics, 94(1), 288–294.