Effect of microstructure on strain localization in a 7050 aluminum alloy: Comparison of experiments and modeling for various textures

Abstract

Microstructure attributes are responsible for heterogeneous deformation and strain localization. In this study, the relation between residual strain fields and microstructure is examined and assessed by means of experiments and crystal plasticity modeling. The microstructure of rolled aluminum alloys (AA) in the 7050-T7451 condition was experimentally obtained with electron backscatter diffraction (EBSD) analysis along the rolling direction (L-T orientation), across the rolling direction (T-L orientation), and transverse to the rolling direction (T-S orientation). Each of these sections was also patterned using a novel microstamping procedure, to allow for strain mapping by digital image correlation (DIC). The measured microstructures were in turn used as input of an elasto-viscoplastic crystal plasticity formulation based on fast Fourier transforms (EVP-FFT). Comparisons between the strain maps obtained experimentally by the concurrent DIC-EBSD method and the EVP-FFT simulations were made for the three sections, corresponding to the initial textures. The comparisons showed that the predicted levels of strain concentration were reasonable for all three specimens from a statistical perspective, which is important to properly describe and predict the strains within an ensemble of components; however the spatial match with the actual strain fields needs improvement.

The use of nondestructive evaluation methods in fatigue: A review

“…The data points shown were used to investigate the effect of the resulting plastic fields on the crack growth behaviour and to provide estimations of crack growth rates. Similar applications have succeeded to relate local measurements with globally observed data trends, which have been additionally leveraged to validate various fatigue models …”

“…Measurements at the material scale made when monitoring the fatigue process have assisted in the overall understanding of the fatigue behaviour as well as in the development of mathematical relations which are used to define conditions, for example, based on which subcritical or critical crack growth occurs. One such popular mathematical relation is the widely used Paris Law which relates the crack growth rate to the stress intensity factor, resulting in a linear relationship prior to fast crack growth, which has proven useful to investigate the growth of long (typically greater than 1 mm) cracks . Other ways to address fatigue damage is to implement a material selection and design approach based on the widely used fatigue limit, according to which the material is assumed to not fail if the applied loading remains smaller than the so‐called limit stress.…”

“…One such popular mathematical relation is the widely used Paris Law which relates the crack growth rate to the stress intensity factor, resulting in a linear relationship prior to fast crack growth, which has proven useful to investigate the growth of long (typically greater than 1 mm) cracks. [13][14][15] Other ways to address fatigue damage is to implement a material selection and design approach based on the widely used fatigue limit, 3 according to which the material is assumed to not fail if the applied loading remains smaller than the so-called limit stress. In practice, not all materials reach such limit, while recent advances in ultrasonic fatigue testing, for example, show that failure will often occur below the classically defined fatigue limit.…”

Crack incubation in shot peened AA7050 and mechanism for fatigue enhancement

“…The gripping mechanisms used were MTS 647 hydraulic wedge grips, capable of gripping pressure up to 21 MPa. The maximum stress was chosen as ~85% of the material's tensile yield strength, 469 MPa as measured from . Thus, the load range was 20 to 400 MPa, resulting in a stress ratio of 0.05 to avoid any potential buckling of the specimen.…”

“…The maximum stress was chosen as~85% of the material's tensile yield strength, 469 MPa as measured from. 35 Thus, the load range was 20 to 400 MPa, resulting in a stress ratio of 0.05 to avoid any potential buckling of the specimen. This ensured that the fatigue loading regime remained within the elastic region of the material.…”