Experimental-numerical analysis of the indentation-based damage characterization methodology

C.C. Tasan, J.P.M. Hoefnagels, L.C.N. Louws, M.G.D. Geers

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

Abstract

The introduction of advanced high strength steels, e.g., into the automotive industry initiated a huge interest in analyzing and understanding ductile fracture of sheet metals to greater details. This demands for the development of experimental methodologies that provide microvoid evolution parameters, which also serve as crucial input parameters for advanced forming simulation that can predict damage evolution. Therefore, this work scrutinizes the reliability and applicability of an increasingly popular damage characterization methodology, in which microindentation tests are carried out to measure hardness and elastic modulus degradation as a function of accumulated strain, relating this degradation to damage evolution. To accomplish this goal, this methodology is applied to several different sheet metals of different formability (an interstitial-free steel, a dual phase steel, an aluminum-magnesium-silicon alloy and a ferritic stainless steel). To analyze and verify the results of indentation based methodology, damage evolution in these metals is monitored also via different experimental techniques, i.e. scanning electron microscopy, micro-ct tomography and sensitive density measurement. Moreover, finite element simulations are carried out to understand the effect of void accumulation in the degradation of hardness and elastic modulus. In the case of using the hardness as a damage probe, the degradation due to damage is always coupled to other effects (strain hardening, grain shape change, texture development) causing an increase in the obtained hardness value for all of the sheet metals tested, thereby complete obscuring any degradation of the hardness due to damage. In the case of elastic modulus, all the sheet metals tend to pile-up upon indentation when they are severely deformed, leading to large systematic errors in the Oliver-Pharr methodology based modulus determination, whereas the elastic modulus is also intrinsically altered by the grain shape change and texture development seen for increasing deformation. Therefore, it can only be concluded that, contrary to the published results in the literature, neither the hardness degradation nor the elastic modulus degradation can be used as a precise probe for damage accumulation, at least when the indentation based methodology is carried out in the originally-proposed manner that is commonly used in the literature.

Original languageEnglish
Title of host publicationSociety for Experimental Mechanics - 11th International Congress and Exhibition on Experimental and Applied Mechanics 2008
Pages1737-1745
Number of pages9
Volume4
Publication statusPublished - 2008
Event11th International Congress and Exhibition on Experimental and Applied Mechanics - Orlando, United States
Duration: 2 Jun 20085 Jun 2008

Conference

Conference11th International Congress and Exhibition on Experimental and Applied Mechanics
CountryUnited States
CityOrlando
Period2/06/085/06/08

Fingerprint

Dive into the research topics of 'Experimental-numerical analysis of the indentation-based damage characterization methodology'. Together they form a unique fingerprint.

Cite this