Articles written in Sadhana

    • A non-linear ductile damage growth law at elevated temperature


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      Continuum damage mechanics (CDM) model is commonly used for the prediction of ductile fracture. For numerical simulation of ductile fracture in impact or high-temperature problems, the damage growth law that incorporates the effect of high temperature is needed. Experimentally, it has been observed that damage growth decreases with temperature. However, the damage growth law at high temperature is not easily available in the literature. In the present work, a damage growth law at high temperature is proposed for steel, based on the experimental measurement of damage carried out at IIT Kanpur.

    • NURBS-based isogeometric analysis for stable and accurate peeling computations


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      Numerical solution of adhesive peeling problems presents significant computational challenges. This is due to the large peeling stresses that occur in the very narrow zone ahead of the peeling front. The available literature offers solutions using either higher-order Lagrange-enriched finite-element (FE) or nonuniform rational B-spline (NURBS)-enriched FE strategies. However, no work that fully utilizes the intrinsic advantageous features of isogeometric analysis and systemically explores the influence of NURBS discretizations exists on the adhesive peeling computations. Thus, the objective of the present work is to fill this research gap by carrying out a comprehensive and detailed isogeometric analysis of peeling problems and also to study the effect of different classes of NURBS discretizations on the stability and accuracy of peeling contact computations. In particular, higher-continuous and higher-order NURBS discretizations that are constructed with different combinations of various isogeometric refinement strategies are employed. In addition to this, higher-order Lagrange discretizations are adopted to perform comparative assessment of various isogeometric NURBS discretizations. The comparison is carried out in terms of accuracy, stability and computation cost for peeling analysis. The obtained results demonstrate the advantages of the NURBS discretizations: higher-continuous NURBS discretization delivers an accuracy similar to that with the higher-order Lagrange discretization at a much lower computational cost. Further, the higher-order NURBS discretizations significantly improve the stability and accuracy again at a lower computational cost as compared with higher-order Lagrange discretizations

    • A novel hybrid isogeometric element based on two-field Hellinger– Reissner principle to alleviate different types of locking


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      In the present work, novel hybrid elements are proposed to alleviate the locking anomaly in non-uniform rational B-spline-based isogeometric analysis (IGA) using a two-field Hellinger–Reissner variational principle. The proposed hybrid elements are derived by adopting the independent interpolation schemes for displacement and stress fields. The key highlight of the present study is the choice and evaluation of higher-order terms for the stress interpolation function to provide a locking-free solution. Furthermore, the present study demonstrates the efficacy of the proposed elements with the treatment of several two-dimensional linear-elastic benchmark problems alongside the conventional single-field IGA, Lagrangian-based finite element analysis (FEA), and hybrid FEA formulation. It is shown that the proposed class of hybrid elements performs effectively for analyzing the nearly incompressible problem domains thatare severely affected by volumetric locking along with the thin plate and shell problems where the shear locking is dominant. A better coarse mesh accuracy of the proposed method in comparison with the conventional formulation is demonstrated through various numerical examples. Moreover, the formulation isnot restricted to the locking-dominated problem domains but can also be implemented to solve the problems of general form without any special treatment. Thus, the proposed method is robust, most efficient, and highly effective against both shear and volumetric locking.

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