Author
Nagaraj K. Arakere
Other affiliations: Wichita State University
Bio: Nagaraj K. Arakere is an academic researcher from University of Florida. The author has contributed to research in topics: Contact mechanics & Turbine blade. The author has an hindex of 24, co-authored 75 publications receiving 1723 citations. Previous affiliations of Nagaraj K. Arakere include Wichita State University.
Papers published on a yearly basis
Papers
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TL;DR: In this article, some of the most widely used RCF models are reviewed and discussed, and their limitations are addressed, and the modeling approaches recently proposed by the authors to develop life models and better understanding of the RCF.
Abstract: Ball and rolling element bearings are perhaps the most widely used components in industrial machinery. They are used to support load and allow relative motion inherent in the mechanism to take place. Subsurface originated spalling has been recognized as one of the main modes of failure for rolling contact fatigue (RCF) of bearings. In the past few decades a significant number of investigators have attempted to determine the physical mechanisms involved in rolling contact fatigue of bearings and proposed models to predict their fatigue lives. In this paper, some of the most widely used RCF models are reviewed and discussed, and their limitations are addressed. The paper also presents the modeling approaches recently proposed by the authors to develop life models and better understanding of the RCF.
438 citations
TL;DR: In this paper, a fatigue failure criterion based on the maximum shear stress amplitude /Delta(sub tau)(sub max))] on the 24 octahedral and 6 cube slip systems was presented for single crystal turbine blades.
Abstract: High cycle fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE' N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude /Delta(sub tau)(sub max))] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200 F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale three-dimensional finite element model. This finite element model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297 finite element model runs. Fatigue lives at critical points in the blade are computed using finite element stress results and the failure criterion developed. Stress analysis results in the blade attachment region are also presented. Results presented demonstrates that control of secondary and primary crystallographic orientation has the potential to significantly increase a component S resistance to fatigue crack growth with- out adding additional weight or cost. [DOI: 10.1115/1.1413767]
134 citations
TL;DR: In this article, a microindentation technique was used to measure the changes in the material hardening and softening characteristics within the RCF affected zone and represent the change in the form of microhardness maps.
90 citations
TL;DR: In this paper, numerical and experimental evolutions of slip fields in notched Ni-Base Single Crystal superalloy tensile specimens are presented as a function of secondary crystallographic orientation, and the numerical predictions based on three-dimensional anisotropic elasticity and crystal plasticity are compared with experimental observations.
74 citations
TL;DR: In this paper, crystal plasticity simulations and experiments of cylindrical indentation on Nickel base single crystal superalloy specimens are presented and discussed and the subsurface stress and strain fields presented are similar to those observed in meso-scale dovetail joints in single crystal turbine blades.
69 citations
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TL;DR: In this paper, the structure and properties of bearing steels prior to the point of service are first assessed and described in the context of steelmaking, manufacturing and engineering requirements, followed by a thorough critique of the damage mechanisms that operate during service and in accelerated tests.
729 citations
TL;DR: This paper reviews the current technologies used in high-speed electrical machines through an extensive survey of different topologies developed and built in the industry and academia for several applications.
Abstract: This paper reviews the current technologies used in high-speed electrical machines through an extensive survey of different topologies developed and built in the industry and academia for several applications. Developments in materials and components, including electrical steels and copper alloys, are discussed, and their impact on the machines' operating physical boundaries is investigated. The main application areas pulling the development of high-speed machines are also reviewed to better understand the typical performance requirements.
596 citations
University of Groningen1, PSL Research University2, École centrale de Lyon3, University of Padua4, Delft University of Technology5, Imperial College London6, Luleå University of Technology7, IMT Institute for Advanced Studies Lucca8, Technical University of Denmark9, University of Southampton10, University of Cape Town11, École Polytechnique Fédérale de Lausanne12, Aarhus University13, King's College London14, Hamburg University of Technology15, Czech Technical University in Prague16, Instituto Politécnico Nacional17, Polish Academy of Sciences18, University of Turin19, University of Trento20, Queen Mary University of London21, Saarland University22
TL;DR: This review summarizes recent advances in the area of tribology based on the outcome of a Lorentz Center workshop surveying various physical, chemical and mechanical phenomena across scales, and proposes some research directions.
347 citations
TL;DR: In this article, a review of Ni-base superalloys in terms of fundamental deformation mechanisms, environmental effects, and interactions between environment and deformation mode is presented, where the basic principles that are developed are used to show how both intrinsic and extrinsic variables can be manipulated to control fatigue behaviour and as a guide for formulation of engineering life prediction models.
339 citations
TL;DR: New analytical solutions and closed-form relationships for predicting the elastic modulus, Poisson׳s ratio, critical buckling load, and yield (plateau) stress of cellular structures made of the diamond lattice unit cell are presented.
Abstract: Cellular structures with highly controlled micro-architectures are promising materials for orthopedic applications that require bone-substituting biomaterials or implants The availability of additive manufacturing techniques has enabled manufacturing of biomaterials made of one or multiple types of unit cells The diamond lattice unit cell is one of the relatively new types of unit cells that are used in manufacturing of regular porous biomaterials As opposed to many other types of unit cells, there is currently no analytical solution that could be used for prediction of the mechanical properties of cellular structures made of the diamond lattice unit cells In this paper, we present new analytical solutions and closed-form relationships for predicting the elastic modulus, Poisson׳s ratio, critical buckling load, and yield (plateau) stress of cellular structures made of the diamond lattice unit cell The mechanical properties predicted using the analytical solutions are compared with those obtained using finite element models A number of solid and porous titanium (Ti6Al4V) specimens were manufactured using selective laser melting A series of experiments were then performed to determine the mechanical properties of the matrix material and cellular structures The experimentally measured mechanical properties were compared with those obtained using analytical solutions and finite element (FE) models It has been shown that, for small apparent density values, the mechanical properties obtained using analytical and numerical solutions are in agreement with each other and with experimental observations The properties estimated using an analytical solution based on the Euler–Bernoulli theory markedly deviated from experimental results for large apparent density values The mechanical properties estimated using FE models and another analytical solution based on the Timoshenko beam theory better matched the experimental observations
315 citations