Identification of Heterogeneous Constitutive Parameters in a Welded Specimen: Uniform Stress and Virtual Fields Methods for Material Property Estimation
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Local strain data obtained throughout the entire weld region encompassing both the weld nugget and heat affected zones (HAZs) are processed using two methodologies, uniform stress and virtual fields, to estimate specific heterogeneous material properties throughout the weld zone. Results indicate that (a) the heterogeneous stress–strain behavior obtained by using a relatively simple virtual fields model offers a theoretically sound approach for modeling stress–strain behavior in heterogeneous materials, (b) the local stress–strain results obtained using both a uniform stress assumption and a simplified uniaxial virtual fields model are in good agreement for strains ɛ xx < 0.025, (c) the weld nugget region has a higher hardening coefficient, higher initial yield stress and a higher hardening exponent, consistent with the fact that the steel weld is overmatched and (d) for ɛ xx > 0.025, strain localization occurs in the HAZ region of the specimen, resulting in necking and structural effects that complicate the extraction of local stress strain behavior using either of the relatively simple models.
KeywordsMaterial parameter identification Heterogeneous weld zone Virtual fields method Computer vision Digital image correlation
The authors gratefully acknowledge the support of (a) the Army Research Office and Dr. Bruce Lamattina through W911NF-06-1-0216, (b) Dr. Stephen Smith and NASA Langley under Grant NASA-NRA-NNX07AB46A and (c) General Motors and Dr. Pablo Zavattieri through both contractual support ND0144200 and an unrestricted gift 002259249. The technical assistance provided by Prof. Xiaomin Deng in the Department of Mechanical Engineering at the University of South Carolina and Dr. Hubert Schreier and Correlated Solutions Incorporated for supporting this effort through modifications to their software, VIC-2D, for our use is deeply appreciated.
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