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Author

Ramesh Rajasekaran

Other affiliations: University of Oxford
Bio: Ramesh Rajasekaran is an academic researcher from Rolls-Royce Holdings. The author has contributed to research in topics: Mistuning & Honeycomb. The author has an hindex of 12, co-authored 18 publications receiving 546 citations. Previous affiliations of Ramesh Rajasekaran include University of Oxford.

Papers
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Journal ArticleDOI
TL;DR: In this article, a vibroacoustics analysis of auxetic gradient honeycomb composite structures with hexagonal configurations is presented, where two classes of gradient cellular layout are examined: one with continuously varying internal cell angle, the other with gradient cell wall aspect ratio across the surface of the honeycomb panel.

135 citations

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TL;DR: In this paper, a biaxial fatigue experiment is described which is capable of simulating the loading experienced by a dovetail blade root in an aircraft gas turbine and a comprehensive stress analysis of the experimental configuration has been undertaken and a semi-analytical approach has been developed to provide accurate estimates of surface tractions and subsurface stress fields.

127 citations

Journal ArticleDOI
TL;DR: In this paper, gradient cellular centresymmetric auxetic configurations are evaluated as potential cores for aeroengine fan blades, and optimized to reduce the dynamic response for the first three fundamental modes.
Abstract: In this study, gradient cellular centresymmetric auxetic configurations are evaluated as potential cores for aeroengine fan blades, and optimized to reduce the dynamic response for the first three fundamental modes. Auxetic (negative Poisson’s ratio) re-entrant cellular beams are modeled, manufactured, and tested to assess their natural frequencies and mode shapes. Gradient versions of these beams with a varying internal cell angle are then designed to be incorporated as fillers in a baseline fan blade model. The optimized configurations of the gradient core lead to a substantial decrease of the mass of the fan blade, reduction of the dynamic modal displacements, and a lowering of the first three natural frequencies within the admissible frequency bandwidth.

115 citations

Journal ArticleDOI
TL;DR: In this article, a review of the relevant literature about mistuning problems in bladed disc systems, and their implications for the uncertainty propagation associated to the dynamics of aeroengine systems is presented.

52 citations

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TL;DR: In this paper, the authors explore fully damping in honeycomb cells with inserts from the point of view of minimal increase in density and location of inserts, using analytical, finite element and topological optimisation methods to find the best locations of a damping insert within the cell.

38 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the relationship among structures, materials, properties and applications of auxetic metamaterials and structures is discussed. And the challenges and future work on the topic of auxetics are also presented to inspire prospective research work.
Abstract: Materials and structures with negative Poisson's ratio exhibit a counter-intuitive behaviour. Under uniaxial compression (tension), these materials and structures contract (expand) transversely. The materials and structures that possess this feature are also termed as 'auxetics'. Many desirable properties resulting from this uncommon behaviour are reported. These superior properties offer auxetics broad potential applications in the fields of smart filters, sensors, medical devices and protective equipment. However, there are still challenging problems which impede a wider application of auxetic materials. This review paper mainly focuses on the relationships among structures, materials, properties and applications of auxetic metamaterials and structures. The previous works of auxetics are extensively reviewed, including different auxetic cellular models, naturally observed auxetic behaviour, different desirable properties of auxetics, and potential applications. In particular, metallic auxetic materials and a methodology for generating 3D metallic auxetic materials are reviewed in details. Although most of the literature mentions that auxetic materials possess superior properties, very few types of auxetic materials have been fabricated and implemented for practical applications. Here, the challenges and future work on the topic of auxetics are also presented to inspire prospective research work. This review article covers the most recent progress of auxetic metamaterials and auxetic structures. More importantly, several drawbacks of auxetics are also presented to caution researchers in the future study.

603 citations

Journal ArticleDOI
TL;DR: In this article, the authors focus on the topology-property relationship in three main classes of auxetic metamaterials, namely re-entrant, chiral, and rotating (semi-) rigid structures.
Abstract: The surge of interest in so-called “designer materials” during the last few years together with recent advances in additive manufacturing (3D printing) techniques that enable fabrication of materials with arbitrarily complex nano/micro-architecture have attracted increasing attention to the concept of mechanical metamaterials. Owing to their rationally designed nano/micro-architecture, mechanical metamaterials exhibit unusual properties at the macro-scale. These unusual mechanical properties could be exploited for the development of materials with advanced functionalities, with applications in soft robotics, biomedicine, soft electronics, acoustic cloaking, etc. Auxetic mechanical metamaterials are identified by a negative Poisson's ratio and are perhaps the most widely studied type of mechanical metamaterials. Similar to other types of mechanical metamaterials, the negative Poisson's ratio of auxetics is generally a direct consequence of the topology of their nano/micro-architecture. This paper therefore focuses on the topology–property relationship in three main classes of auxetic metamaterials, namely re-entrant, chiral, and rotating (semi-) rigid structures. While the deformation mechanisms in the above-mentioned types of structures and their relationship with the large-scale mechanical properties receive most attention, the emerging concepts in design of auxetics such as the use of instability in soft matter and origami-based structures are discussed as well. Furthermore, the data available in the literature regarding the elastic properties of auxetic mechanical metamaterials are systematically analyzed to identify the spread of Young's modulus–Poisson's ratio duos achieved in the auxetic materials developed to date.

428 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive updated review of auxetic materials, their types and properties, and applications has been presented, and the design and modeling approaches of Auxetic structures are discussed.
Abstract: Material properties can be tailored through modification of their geometry or architecture. With this concept, a lot of smart materials, metamaterials, and smart structures have been developed. Auxetic materials and structures are a novel class of materials which exhibit an interesting property of negative Poisson's ratio. By virtue of the auxetic behavior, mechanical properties such as fracture toughness, indentation resistance, etc., can be improved. In order to exploit the interesting properties of auxetic materials, several potential applications of auxetic materials have been explored in medical, sports, automobile, defense, etc. Design and modeling of novel auxetic materials and structures is still on the way. Here, the article focuses upon the different aspects of auxetic materials and structures. A comprehensive updated review of auxetic materials, their types and properties, and applications has been presented. This paper also discusses the design and modeling approaches of auxetic structures.

378 citations

Journal Article
TL;DR: In this paper, a modification of the integrated friction model structure proposed by Swevers et al. called the Leuven model is presented, which allows accurate modeling both in the presliding and the sliding regimes without the use of a switching function.
Abstract: This note presents a modification of the integrated friction model structure proposed by Swevers et al. (2000), called the Leuven model. The Leuven model structure allows accurate modeling both in the presliding and the sliding regimes without the use of a switching function. The model incorporates a hysteresis function with nonlocal memory and arbitrary transition curves. This note presents two modifications of the Leuven model. A first modification overcomes a recently detected shortcoming of the original Leuven model: a discontinuity in the friction force which occurs during certain transitions in presliding. A second modification, using the general Maxwell slip model to implement the hysteresis force, eliminates the problem of stack overflow, which can occur with the implementation of the hysteresis force.

288 citations