ISSN:
1662-7482
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
The introduction of advanced high strength steels, e.g., into the automotive industryinitiated a huge interest in analyzing and understanding ductile fracture of sheet metals to greaterdetails. This demands for the development of experimental methodologies that provide microvoidevolution parameters, which also serve as crucial input parameters for advanced forming simulationthat can predict damage evolution. Therefore, this work scrutinizes the reliability and applicabilityof an increasingly popular damage characterization methodology, in which microindentation testsare carried out to measure hardness and elastic modulus degradation as a function of accumulatedstrain, relating this degradation to damage evolution. To accomplish this goal, this methodology isapplied to several different sheet metals of different formability (an interstitial-free steel, a dualphase steel, an aluminum-magnesium-silicon alloy and a ferritic stainless steel). To analyze andverify the results of indentation based methodology, damage evolution in these metals is monitoredalso via different experimental techniques, i.e. scanning electron microscopy, micro-ct tomographyand sensitive density measurement. Moreover, finite element simulations are carried out tounderstand the effect of void accumulation in the degradation of hardness and elastic modulus. Inthe case of using the hardness as a damage probe, the degradation due to damage is always coupledto other effects (strain hardening, grain shape change, texture development) causing an increase inthe obtained hardness value for all of the sheet metals tested, thereby complete obscuring anydegradation of the hardness due to damage. In the case of elastic modulus, all the sheet metals tendto pile-up upon indentation when they are severely deformed, leading to large systematic errors inthe Oliver-Pharr methodology based modulus determination, whereas the elastic modulus is alsointrinsically altered by the grain shape change and texture development seen for increasingdeformation. Therefore, it can only be concluded that, contrary to the published results in theliterature, neither the hardness degradation nor the elastic modulus degradation can be used as aprecise probe for damage accumulation, at least when the indentation based methodology is carriedout in the originally-proposed manner that is commonly used in the literature
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/38/transtech_doi~10.4028%252Fwww.scientific.net%252FAMM.13-14.151.pdf
Permalink