A constitutive model independent analytical method in determining the tensile properties from incremental spherical indentation tests (ISITs). (November 2018)

• Record Type: Journal Article
• Authors: Zhang, Tairui; Wang, Shang; Wang, Weiqiang
• Is Part Of: International journal of mechanical sciences. Volume 148(2018)
• Page Start: 9
• Page End: 19
• Publication Date: 2018-11
• Subjects: Simplified expanding cavity model -- Equivalent energy principle -- Differential approach -- Constitutive behavior -- Incremental spherical indentation tests; Mechanical engineering -- Periodicals; Génie mécanique -- Périodiques; Mechanical engineering; Maschinenbau; Mechanik; Zeitschrift; Periodicals; 621.05
• DOI: 10.1016/j.ijmecsci.2018.08.010
• Languages: English
• ISSNs: 0020-7403

Abstract

Highlights: The analytical method proposed in this study has an obvious physical meaning and does not depend on a specific constitutive model, and thus can be used on a large variety of materials and can be considered as a substitute of destructive uniaxial tensile tests. A simplified expanding cavity model, which considers the core region and elastoplastic region as a whole, was proposed, and thus the error caused by corresponding p i to p m was avoided. DIC measurement of the plastic zone radius was introduced into the indentation tests in this study to determine the proportional limit of a material, and was proved to be of considerable accuracy. This method was verified through experiments on four materials, and the effects of strain threshold in DIC measurements on tensile property evaluations were also discussed. The stress-strain data points from ISITs can even characterize the yield plateau in tensile stress-strain curves, which no previous indentation method can characterize yet. Abstract: In this study, an analytical method based on the simplified expanding cavity model, the equivalent energy principle, and the differential approach was proposed to determine the stress-strain relationship (constitutive behavior) of materials from incremental spherical indentation tests (ISITs). Apart from the load-depth curve obtained from the load cell and displacement sensor, respectively, one measurement of the plastic zone radius r p after the indentation test through digital image correlation (DIC) method was also used to determine the proportional limit σ 0 . The analytical derivation of this method has a clear physical meaning and does not depend on any specific constitutive models, and thus can be used on a large variety of materials and can be considered as a substitute for destructive uniaxial tensile tests. Experiments were conducted on four materials, 15CrMoR, TC21, SA508, and SA533. Two different models, which took the characteristics of the derived stress-strain data points into consideration, were used to describe the constitutive behavior of the four experimental materials. Experimental results proved that ISITs provided almost identical Young's modulus E (with a maximum error of less than 3%), stress-strain curves, proof strength R p0.2 (with a maximum error of -5.9% when the strain threshold ε th = 0.6%), and tensile strength R T (with a maximum error of -6.7% when ε th = 0.6%) as their tensile counterparts. Furthermore, the stress-strain data points derived with the method proposed in this study could even characterize the yield plateau in the stress-strain curves of 15CrMoR, SA508, and SA533. Graphical abstract: