Browsing by Author "Lodh, Arijit"

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    Fabrication and mechanical testing of mesoscale specimens
    (Springer, 2023-05-08) Lodh, Arijit; Keller, Clement; Castelluccio, Gustavo M.
    The mechanical response of metallic materials results from a complex hierarchy of deformation mechanisms across length scales. The need to understand these mechanisms independently has driven the miniaturization of testing samples, including small scale samples and single crystal micropillars. However, difficulties in machining and testing small samples have hampered the evaluation of the mechanical response of mesoscale samples with dimensions between tens to hundreds of microns. This paper innovates with a simple approach for the manufacturing and test of dog-bone specimens with a minimum gauge width up to 50 μm. The results demonstrate a pronounced sample size effects on the mechanical response for the dimensions analysed and highlights the need to advance the characterization of mesoscale samples. We also demonstrated the capability of testing the tensile response of single crystals from engineering alloys.
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    Insights into the stability of retained austenite during wear
    (Taylor and Francis, 2022-11-01) Neoga, Suruj Protim; Lodh, Arijit; Karmakar, Anish; Nair, Akhil G.; Dasgupta, Arup; Bakshi, Subhankar Das; Das, Sourav
    Transformation-induced plasticity mechanism is a very interesting phenomenon wherein a certain amount of austenite, which is thermally stable at room temperature but can be transformed to martensite during deformation, is retained in the microstructure. The amount of deformation (either by tensile, compressive or shear) that the austenite regions can withstand before they transform to martensite depends on their stability which is a function of the chemical-free energy and the severity of straining. In the current work, a bainitic steel with some retained austenite (RA), exposed to sliding wear in a pin-on-disc wear testing machine, was considered for the study. This paper aims to quantify the shear strain developed in the deformed subsurface region due to wear by using a simple image digitisation technique, and the stability aspect of RA for a complicated deformation mechanism like wear was studied considering the thermodynamics of austenite to ferrite transformations.
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    Orientation-dependent solid solution strengthening in zirconium: a nanoindentation study
    (Springer, 2019-12-17) Lodh, Arijit; Pant, Prita; Kumar, Gulshan; Mani Krishna, K. V.; Tewari, Raghvendra; Samajdar, Indradev
    Orientation-dependent solid solution strengthening was explored through a combined microtexture plus nanoindentation study. Pure zirconium (6N purity crystal-bar Zr) and commercial Zircaloy-2 were investigated for comparison. Local mechanical properties were estimated through finite element (FE) simulations of the unloading part of the nanoindentation load–displacement response. Combinations of ‘averaging’ scheme and constitutive relationship were used to resolve uncertainty of FE-extracted mechanical properties. Comparing the two grades, non-basal oriented grains showed an overall hardening and increase in elastic modulus. In contrast, insignificant change was observed for basal (or near-basal) oriented grains. The strengthening of non-basal orientations appeared via elimination of the lowest hardness/stiffness values without a shift in the peak value. Such asymmetric development brought out the clear picture of orientation-dependent solid solution strengthening in zirconium.
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    Revitalising metallic materials: a path towards a sustainable circular economy
    (MDPI, 2023-07-28) Ashraf, Farhan; Lodh, Arijit; Pagone, Emanuele; Castelluccio, Gustavo M.
    Improving materials’ productivity and reusability can advance circularity by reducing extraction and enabling efficient fully recyclable parts and systems. However, the pursuit of circular materials often focuses on the choice among reusing, repairing, or recycling materials, with limited consideration for techniques that can proactively revitalise materials. Consequently, the adoption of preventive material therapies remain relatively scarce and unexplored. This work discusses the potential for revitalising metallic materials with preventive maintenance prior to detectable damage and we identify techniques that can effectively prolong the structural lifespan of metallic components. By analysing the literature and considering the eco-footprint and implementation feasibility within the aerospace sector, this study ranks approaches based on their circularity impact and provides valuable insights to guide future research in the field of materials maintenance.
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    X-ray diffraction for the determination of residual stress of crystalline material: an overview
    (Springer, 2022-03-07) Lodh, Arijit; Thool, Khushahal; Samajdar, Indradev
    Though there are a variety of experimental techniques available for residual stress measurements, diffraction-based measurements have the unique advantage of estimating the individual components of the residual strain matrix in a crystalline material. This is then converted to residual stresses with appropriate continuum elasticity model(s) and X-ray elastic constants. In particular, measurements based on electron or neutron diffractions have their complexities or availability issues. The laboratory X-ray diffraction, on the other hand, may provide an easy resource and an effective tool. Such measurements range from two tilt methods to more extended d-sin2ψ measurements and multiple {hkil} grazing incident X-ray diffraction. Measurements can even be conducted on single crystals with micro-Laue diffraction and extended to stress ODF (orientation distribution function) calculations. These techniques are unquestionably extremely specialized, where measurement uncertainty plays an important role in the effectiveness plus reproducibility of the data. Unfortunately, standard textbooks or review articles typically describe some, but not all, of the techniques. In this overview, different techniques of X-ray diffraction for the determination of residual stresses in crystalline material have been summarized. It is hoped that potential users may benefit from the deliberations.