Responses and constitutive modeling of aluminum alloys, and strain-rate and temperature dependent failure criteria for F.C.C. and H.C.P. metals

Title	Responses and constitutive modeling of aluminum alloys, and strain-rate and temperature dependent failure criteria for F.C.C. and H.C.P. metals
Author	Liu, Haowen
Advisors	Akhtar. Khan, Akhtar S. ;
Program	Engineering, Mechanical
UMBC Department	Mechanical Engineering
Document Type	dissertation
Sponsors	University of Maryland, Baltimore County (UMBC)
Keywords	Anisotropy; Constitutive model; Failure criterion; Strain Rate; Temperature; Tension compression asymmetry
Date Issued	2011-01-01
Abstract	The thermo-mechanical response of Al 2024-T351 under uniaxial compression loading are presented. Below certain threshold temperature, negligible strain-rate sensitivity is observed during quasi-static regime, while significant strain rate sensitivity is measured at dynamic strain-rates. Above threshold temperature, increasing strain-rate sensitivity has been observed. Based on these observations, KHL phenomenological constitutive model is significantly modified to predict the mechanical behavior of the alloy. Correlations with this modified model are shown very close to the observed responses. The second aim of this investigation is to establish a universal, accurate and robust failure criterion for ductile solids. New experimental results, along with published data on the Al 2024-T351 alloy by Stoughton and Yoon (2011), are used to establish a phenomenological failure criterion using the magnitude of stress vector and the first invariant of stress tensor. Moreover, the proposed failure criterion is used for prediction of the published results by Bruenig et al. (2008). This proposed isotropic failure criterion, based on the magnitude of stress vector (MSV), is further developed to include strain rate and temperature dependences. Based on experiment results, an exponential loading is included to simulate the strain rate effect; the KHL hardening model type temperature dependent term is also included to correlate with the observed temperature sensitivity of the failure of Al2024-T351 alloy. These modifications allow the proposed MSV failure criterion to predict the failure of Al 2024-T351 alloy over wide ranges of strain rate and temperature. Further, by demonstrating the influence of hydrostatic pressure on the anisotropic failure behavior of a HCP alloy, a new uncoupled anisotropic failure criterion is established. To comprehensively consider the anisotropy and tension compression asymmetry in the Ti-6Al-4V alloy, the modified Hill anisotropic function proposed by Khan and Yu (2011b), is used to describe the geometry of the anisotropic failure loci in principal stress space. Moreover, the KHL hardening mode type strain rate and temperature terms are adopted in the new anisotropic failure criterion to predict the failure strength of the Ti-6Al-4V alloy. Excellent correlation between predicted failure loci and the corresponding failure observations is demonstrated.
Identifier	10561
Format	application:pdf
Language	en
Collection	UMBC Theses and Dissertations.
Rights Statement	This item may be protected under Title 17 of the U.S. Copyright Law. It is made available by UMBC for non-commercial research and education. For permission to publish or reproduce, please see http://aok.lib.umbc.edu/specoll/repro.php or contact Special Collections at speccoll(at)umbc.edu.
Source	Liu_umbc_0434D_10561.pdf

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Responses and constitutive modeling of aluminum alloys, and strain-rate and temperature dependent failure criteria for F.C.C. and H.C.P. metals

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