Articles written in Sadhana
Volume 40 Issue 4 June 2015 pp 1205-1240 Mechanical Sciences
In this paper we review developments in higher order strain gradient theories. Several variants of these theories have been proposed in order to explain the effects of size on plastic properties that are manifest in several experiments with micron sized metallic structures. It is generally appreciated that the size effect arises from the storage of geometrically necessary dislocations (GNDs) over and above the statistically stored dislocations (SSDs) required for homogeneous deformations. We review developments that show that the GNDs result from the non-homogeneous nature of the deformation field. Though the connection between GNDs and strain gradients are established in the framework of single crystal plasticity, generalisations to polycrystal plasticity has been made. Strain gradient plasticity inherently involves an intrinsic length scale. In our review, we show, through a few illustrative problems, that conventional plasticity solutions can always be reduced to a scale independent form. The same problems are solved with a simple higher order strain gradient formulation to capture the experimentally observed size effects. However, higher order theories need to be thermodynamically consistent. It has recently been shown that only a few of the existing theories pass this test. We review a few that do. Higher order theories require higher order boundary conditions that enable us to model effects of dislocation storage at impermeable boundaries. But these additional boundary conditions also lead to unique conceptual issues that are not encountered in conventional theories. We review attempts at resolving these issues pertaining to higher order boundary conditions. Finally, we review the future of such theories, their relevance and experimental validation.
Volume 45 All articles Published: 31 August 2020 Article ID 0216
This special issue contains selected papers from among those presented at the ‘‘First International Conference on Mechanical Engineering (INCOM)’’, 2018 held from 4 to 6 January, 2018 at Jadavpur University, Kolkata. The conferencewas organized by the Department of Mechanical Engineering, Jadavpur University. Around 200 papers were presented at the conference in wide ranging areas of mechanical engineering. Based on a preliminary scrutiny, some papers, mostly based on fundamental areas of mechanical engineering, wereshortlisted for consideration of publication in the special issue of Sadhana. The authors of the shortlisted papers were invited to submit extended versions of their works presented at the conference. The submitted papers were reviewedfollowing the review protocol of Sadhana. After multiple rounds of review, eleven papers were finally selected. These papers, apart from being of high quality that meets the standards of the journal, represent different areas like solidmechanics and materials, fluid-structure interaction, heat transfer, combustion and dynamic analysis of mechanical systems.