This paper compares several well known sliding‐window methods for denoising crystal orientation data with variational methods adapted from mathematical image analysis. The variational methods turn out to be much more powerful in terms of preserving low‐angle grain boundaries and filling holes of non‐indexed orientations. The effect of denoising on the determination of the kernel average misorientation and the geometrically necessary dislocation density is also discussed. Synthetic as well as experimental data are considered for this comparison. The examples demonstrate that variational denoising techniques are capable of significantly improving the accuracy of properties derived from electron backscatter diffraction maps.
a b s t r a c tDetailed experimental data on the behavior of textured sheet metals under compressive loading is important to describe their tension-compression asymmetry. This is particularly needed for materials that exhibit a strength-differential effect, or in cases where the Bauschinger effect occurs. So far, there is no systematic work describing the third quadrant in the 2D stress space under biaxial compressive loading. This paper presents a new device for biaxial, compressive in-plane testing of thin sheets. Biaxial and uniaxial compression experiments are carried out in the strain controlled device, analyzing the behavior of deep drawing steel sheets with and without skin-pass treatment. Moreover, in order to allow for the experimental description of the yield surfaces, biaxial tensile tests are performed. Detailed numerical validations and experimental strain analysis both for the new specimen for biaxial compressive testing and for the cruciform specimen for biaxial tensile testing show that reasonably homogeneous strain distributions can be achieved. The combined experimental and numerical method presented here allows to evaluate the tension-compression asymmetry of thin sheet materials. The results for the skin-passed condition clearly exhibit a tension-compression asymmetry, which highlights the necessity of biaxial compression tests already in the as-received material condition. The biaxial compression test opens a pathway to a more detailed analysis of the flow behavior of thin sheets under biaxial compression loading.
High-strength age-hardenable aluminium alloys are susceptible to localised corrosion. It is vital to monitor the evolution of the corrosion depth in order to prevent a critical degradation of the mechanical properties. This study presents the application of 3D optical pattern profilometry for the analysis of the pitting corrosion behaviour of the aluminium alloy EN AW-2024-T3. Therefore, measurements were conducted using a 1 M NaCl solution at different exposure times. The measurements are compared to the results of optical microscopy investigations of metallographic specimens as well as laser scanning microscopy measurements. In immersion bath tests, the 3D pattern profilometry shows a high measurement accuracy of the pitting corrosion. Regarding the pit characteristics, corroded metal sheets exhibit an increase in the pit depth, volume and area with an increasing exposure time of up to 312 h and then decrease. Moreover, a higher increase in the width in rolling direction than perpendicular to it is noticeable.
Abstract. In this study, the behaviour of the residual yield strength of aluminium alloy EN AW-2024-T3 affected by the morphology and numbers of corrosion pits (defects) is presented. Since specific defect structures are not reproducible during experimental corrosion tests, metal sheets with different numbers of pits and pit shapes are produced using laser micro structuring. The defect structures are measured using laser scanning microscopy. To compare the stress states of the micro structured and real corroded metal sheets, FE-analysis is used. Afterwards, uniaxial tensile tests are carried out and critical defect parameters in terms of yield strength reduction of the investigated aluminium alloy are detected.
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