Customized High-Temperature Bending with DIC for High-Throughput Determination of Creep Parameters: Technique, Instrumen
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https://doi.org/10.1007/s11837-020-04445-5 2020 The Minerals, Metals & Materials Society
MESOSCALE MATERIALS SCIENCE
Customized High-Temperature Bending with DIC for High-Throughput Determination of Creep Parameters: Technique, Instrumentation, and Optimization SYED IDREES AFZAL JALALI and VIKRAM JAYARAM1,4
,1,2 PRAVEEN KUMAR
,1,3
1.—Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, India. 2.—e-mail: [email protected]. 3.—e-mail: [email protected]. 4.—e-mail: [email protected]
Bending is emerging as an alternative to uniaxial testing for high-throughput determination of primary-cum-secondary creep parameters. This is feasible because of augmentation of cantilever bending tests with digital image correlation (DIC). Here, we provide guidelines for selecting the patterning medium, spray conditions, and other important parameters for laying highresolution, high contrast ratio DIC speckle-patterns that are optimal for longterm creep tests performed up to 800C. Furthermore, an experimental setup for efficiently performing creep experiments in bending at high temperatures is designed and developed. Proper choices of paint, spraying technique, highresolution image capturing device, and the appropriate heat management system in the mechanical testing unit yield unambiguous correlation in the ‘‘DIC augmented bending creep’’ tests. The developed methodology and the equipment are validated by evaluating the creep behavior of a stainless steel at 750C by obtaining multiple stress–strain rate pairs from a single test. An excellent match between uniaxial and bending data is observed, thereby paving the way for using DIC augmented bending creep for studying the creep response of materials at high temperatures in a high-throughput fashion.
INTRODUCTION Digital image correlation (DIC) is a non-contact strain mapping technique widely used for its simplicity in instrumentation and well-established strain measurement algorithms.1 While contact strain measurement is suitable for measuring uniform deformation, non-homogeneous deformation is observed in a majority of engineering applications and hence measurement of localized deformation fields is often essential. Such localized deformations can be aptly measured by non-contact strain measurement techniques, such as the laser speckle method, laser interferometry, ultrasonic measurements, DIC, etc.1 Among these methods, DIC stands out as the most versatile strain measuring technique. Due to its simplicity in implementation and fully automated correlation procedures, DIC is now regularly implemented in measuring deformation in (Received July 2, 2020; accepted October 7, 2020)
studies involving fracture mechanics,2 fluid mechanics,3 aerial image processing,4 micro-mechanics,5–7 etc. It is routinely applied for studying a wide variety of materials, such as metals,8 composites,9 ceramics,10 polymers,11 and fluids,12 using samples, across various length scales, that are exposed to different loading conditions, such as uniaxial,5 bending,13 t
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