Pramod Padole

Statistical wind prediction and fatigue analysis for horizontal-axis wind turbine composite material blade under dynamic loads:

The purpose of this article is to analyze various wind speed-forecasting methods, select the appropriate method for developing synthetic wind speed for 1-year period at Salem in Tamilnadu state in India, and use it for the structural and fatigue analysis of a small horizontal-axis wind turbine blade made of composite material. Various forecasting models such as Markov chain, Kalman filter, and autoregressive integrated moving average are evaluated, and a long-term wind speed pattern at Salem is developed using Markov chain. This wind pattern is used to create time-varying loads using the blade element momentum on blade sections. Then, the fatigue analysis of the blade is carried out using the stress life approach. The blade is found to have available life of about 20 years and the critical area for fatigue is found on the skin near the root of the blade. Various blade skin materials are also compared for fatigue performance. A cohesive zone model of the adhesively joined root joint is also developed and analyzed for fatigue at the metal–composite joint. Thus, an integrated methodology involving high-fidelity modeling of the blade, wind forecasting, and static and fatigue analysis is developed for horizontal-axis wind turbine blade for locations where historically wind speed measurements are available for short time.

How cryogenic techniques help in machining of nickel alloys? A review

ABSTRACT Nickel alloys are extensively used in aerospace, automotive, marine, nuclear, petro-chemical and food processing industries due to properties like high strength, resistance to heat, resistance to corrosion, etc. However, machining of these alloys pose many challenges in machining such as: work hardening, high temperatures at the cutting zone, rapid tool wear, reduced tool-life, etc. Attempts are made to overcome these challenges by using various cryogenic techniques. This paper, therefore discusses different techniques such as cryogenic cooling, cryogenic treatment of tool and simultaneous use of cryogenic cooling of tool and heating of workpiece (hybrid technique) and their effects on machinability of Nickel alloys with the help of indicators like tool-life, surface roughness, residual stresses, etc. It is concluded that cryogenic techniques are helpful in improving the machining performance by way of improvement in tool-life and surface quality. This happens due to better cooling by cryogen and improved tool properties after cryogenic treatment. However, based on the published works, it is not possible to decide about the following: correct amount of cryogen required for cooling, appropriate cryogenic tool treatment cycle to be used and the best parameters for machining of Nickel alloys. Therefore, future research should focus on these aspects.

Deep neural network-based wind speed forecasting and fatigue analysis of a large composite wind turbine blade

The purpose of this paper is to analyze the modern deep neural networks such as nonlinear autoregressive network with external inputs and a recurrent neural network called long short-term memory for wind speed forecast for long-term and use the prediction for fatigue analysis of a large 5 MW wind turbine blade made of composite materials. The use of machine learning algorithms of advanced neural network applied for engineering problems is increasing recently. The present paper therefore brings as important connection between these latest machine learning methods and engineering analysis of complex wind turbine blades which are also the focus of researchers in renewable system design and analysis. First, a nonlinear autoregressive network with external inputs neural network model using Levenberg–Marquardt back propagation feed forward algorithm is developed with 5 years of environment parameters as input. Similarly, a long short-term memory based model is developed and compared. The chosen long short-term memory model is used for developing two-year wind speed forecast. This wind pattern is used to create time varying loads on blade sections and cross-verified with National Renewable Energy Laboratory tools. A high-fidelity CAD model of the NREL 5 MW blade is developed and the fatigue analysis of the blade is carried out using the stress life approach with load ratio based on cohesive zone modeling. The blade is found to have available life of about 23.6 years. Thus, an integrated methodology is developed involving high-fidelity modeling of the composite material blade, wind speed forecasting using multiple environmental parameters using latest deep learning methods for machine learning, dynamic wind load calculation, and fatigue analysis for National Renewable Energy Laboratory blade.

Non Linear Finite Element Stress Analysis of a Restored Tooth in the Oral Cavity

The aim of the present study is to obtain the stress distribution pattern on the different domains of the tooth in the oral cavity, taking into account non linear properties of the periodontal ligaments (PDL)surrounding the tooth. The stresses and deformation under the action of chewing forces are studied to estimate the risk of tooth fractures. Initially, linear stress and deformation analysis is carried out with three posts different in constitution. However, considering the role of periodontal ligaments, which ensures uniform stress distribution in tooth structure, due to its elastic and non-linear properties, it is felt necessary to simulate the model for non linear analysis. The study reveals that non-linear analysis gives more realistic results as compared to linear analysis. It is observed that under similar loading conditions, the stresses are approximately 25% less in case of non linear analysis and the deformation is 50% more as compared to linear static analysis for an endodontically treated maxillary central incisor. The Dentist can do selection of optimum post core system with better accuracy.Copyright

Linear Finite Element Analysis of a 3-Dimensional Tooth and Its Prototype Model

Dentist, follow root canal therapy to treat teeth with pulpal involvement due to dental caries or as a result of trauma. In order to restore fractured and broken down teeth internal reinforcement is required in the form of a post-core restoration. The post extends into the root canal space and provides retention for the core, which subsequently helps to provide a foundation for the crown restoration. For the treatment procedure, post, core and crown are casted by an indirect procedure by taking the measurements from patient’s tooth in the form of impressions. These impressions are then converted into solid gypsum casts and then wax patterns are developed in order to facilitate casting by the lost wax technique. The final shape of the core and crown and success of the treatment entirely depends upon the skill of the dental technician and involves a number of variables in impressioning, cast poring and wax pattern fabrication. The treatment can be further simplified by making a prototype model of the post, core and the crown by taking the dimensions from the patient’s tooth. This paper presents four prototype models prepared from the solid model of the original tooth and three restored tooth.Copyright