Use of Automated Ball Indentation Testing to Measure Flow Properties and Estimate Fracture Toughness in Metallic Materials

Abstract

A field indentation microprobe (FIM) apparatus was developed (and patented) to evaluate, nondestructively in situ, the integrity of metallic structures. This study investigated the applicability of using a new automated ball indentation (ABI) test, which is a major part of the FIM, to measure the flow properties of metallic materials including those exhibiting Lüders or inhomogeneous strains (carbon steels, titanium alloys, aluminum alloys, etc.) and to estimate their fracture toughness. The ABI test is based on multiple indentations (at the same penetration location) of a polished metallic surface by a spherical indenter. Automation of the test, where a computer and test controller were used in innovative ways to control the test as well as to analyze test data, made it simple, rapid, accurate, economical, and reproducible. Results of ABI tests on different base metals, welds, and irradiated materials are presented and discussed in this paper. Excellent agreement was obtained between ABI-derived data and those from standard ASTM uniaxial tension and fracture toughness tests.

A study on robust indentation techniques to evaluate elastic–plastic properties of metals

“…Haggag et al (1990) and Field and Swain (1995) developed the evaluation methods based on Tabor (1948Tabor ( , 1951 and Francis (1976)'s representative concept. Their formulations, however, have some assumptions that are inconsistent with actual deformations and stress-strain distributions (Taljat et al, 1998;Lee et al, 2005).…”

Effect of temperature on deformation and fracture behaviour of high strength rail steel

“…18 may have been caused by the strength differential effect between tension and compression [29]. Although uniaxial compressive test has been suggested in some work to establish the proper stress-strain relationship for FE modelling of the indentation test [30,31], the tensile stress-strain relationship has actually been satisfactorily used for this purpose in the literature [32,33]. Since the FE simulation conducted in our study was performed using commercial software based on classical von Mises yield function and isotropic hardening, no difference is expected between the tensile and compressive yield behaviours.…”

A Load-Based Multiple-Partial Unloading Micro-Indentation Technique for Mechanical Property Evaluation

“…If the system compliance (C s ) does change during the indentation test, the linear relationship depicted in equation (9) will not be maintained and vice versa. It should be noted that, after obtaining Young's modulus, other mechanical properties such as hardness and stress-strain relationship can also be determined using methods developed by other researchers [9,10,[16][17][18][19].…”

“…Therefore, indirect measurement methods for indentation contact area evaluation were developed by various investigators based on precise indentation depth measurements coupled with suitable calibration procedures. Typically, the unloading stiffness is used to estimate the contact area through some iterative algorithm [16][17][18][19]. Furthermore, high-precision displacement sensors are needed in order to accurately obtain load-depth curve and the unloading stiffness data [6-9, 18, 19].…”